1-s2.0-S0022391312601164-main o

The Journal of Prosthetic Dentistry

103August 2012

Acar et alAcar et al

Clinical ImplicationsWhen the moisture source is inherent dentinal fluid, elastomeric im-pression materials with different hydrophilicity may show the same ability to reproduce detail. Polyurethane resin reproduces fine details better than Type IV dental stone. The use of Type IV dental stone may result in a loss of detail because of its large particle size.

Statement of problem. It is not clear whether more hydrophilic impression materials are better able to copy and transfer dentin surface detail than less hydrophilic ones.

Purpose. The purpose of this study was to evaluate the reproduction of dentin surface detail by means of hydropho-bic and hydrophilic elastomeric impression materials under simulated pulpal pressure and their ability to transfer surface detail onto casts produced from such impressions.

Material and methods. The wettability of the impression materials (n=8) was determined by contact angle measure-ment with an evolution period of 135 seconds. Dentin moisture was provided by means of pulpal pressure simulation, and objective analyses were performed by measuring the average roughness value (Ra) with a 3-D optical profilometer (n=10). One specimen from each group was analyzed with scanning electron microscopy. Contact-angle values were analyzed with a repeated measures ANOVA, and detail reproduction was tested with 3-way ANOVA (α=.05). The Bon-ferroni correction was used to control Type I error for follow-up analyses.

Results. Contact angle measurements revealed significant differences depending on the impression material used and time of the measurement (P<.001). The Ra values of the hydrophilic impression materials, which were made from dry specimens, and the pulpal pressure simulated dentin surfaces did not differ from the dentin surfaces (P>.013). The hydrophobic impression material showed similar detail reproduction ability in a dry field, but loss of detail (evaluated subjectively) and increased roughness values (evaluated objectively) were recorded in a moisturized field (P=.004). Polyurethane-based cast material successfully reproduced the surface texture (P≥.006), whereas Type IV gypsum mate-rial was unable to reproduce this texture to the same extent.

Conclusions. The hydrophilic impression materials tested showed similar ability to reproduce detail under simu-lated pulpal pressure. Polyurethane-based cast material successfully reproduced the surface texture. (J Prosthet Dent 2012;108:102-113)

Surface detail reproduction under simulated pulpal pressure: A 3-dimensional optical profilometer and scanning electron microscopy evaluation

Ozlem Acar, DDS,a Selim Erkut, DDS, PhD,b and Manas Lakshmipathy, MSc

Baskent University, Ankara, Turkey

Supported by a grant-in-aid to scientific research No. D-DA09/02 from the Baskent University, Ankara, Turkey.

aResearch Fellow, Department of Prosthetics, Faculty of Dentistry.bAssociate Professor, Department of Prosthetics, Faculty of Dentistry.cApplication Engineer, Zygo Corporation, Middlefield, Conn.

The most common impression materials used are the vinyl polysi-loxanes (VPS) and polyethers (PE). Widespread use of VPS impression materials may be attributed to their

high accuracy, dimensional stabil-ity, and excellent elastic recovery.1 Polyethers are also highly accurate, but their flexibility is inferior to that of VPS.1 Although VPS impression

materials possess some advantages over polyether, their hydrophobic na-ture, which is related to the chemical structure of the material, results in significant disadvantages. VPS con-

tains hydrophobic aliphatic hydro-carbon groups which surround the siloxane bond, making this material hydrophobic in nature.2 In contrast to VPS, PE impression material, which has functional groups that attract and interact with water molecules, is hydrophilic.2 To overcome this limi-tation, manufacturers have incorpo-rated surfactants and marketed these as hydrophilic VPS materials.3 These materials show more wettability than conventional VPS,4-6 and are known to exhibit lower hydrophilicity than PE impression materials.7,8 However, recent studies have reported lower initial contact angle values (better hy-drophilicity) for recently introduced VPSs than for PEs.4,9 Increased hydro-philicity may be linked to the accurate reproduction of wet oral surfaces and increased wettability with gyp-sum slurry.9 However, Takahashi and Finger10 indicated that hydrophilicity may not be the key to enhanced sur-face detail reproduction.

To investigate the ability of im-pression materials to reproduce sur-face detail, different methods have been used. The American National Standards Institute/American Den-tal Association (ANSI/ADA) speci-fication No. 19 has identified what constitutes acceptable detail repro-duction for nonaqueous elastomeric impression materials.11 Some investi-gators who have used this procedure have evaluated the reproducibility of these impression materials.12,13 How-ever, other investigators have either poured the impression with gypsum slurry and investigated the detail of the cast and the related impres-sion14,15 or have evaluated only the detail of the cast.16,17 It is possible to identify 2 primary problems with this procedure. First, the results of these investigations are based on subjec-tive evaluations made by one or more examiners,12-17 and secondly, as noted by Kanehira et al,18 they disregard the nature of dental substrates such as enamel, dentin, and mucosa. In this regard, using a device that can ana-lyze surfaces may ensure an objective

evaluation,10,18-25 and using calibrated dentin specimens as reference sur-faces10,18,26 may be a more realistic ap-proach.

Although several in vitro stud-ies have evaluated various properties of elastomeric impression materi-als,9,12,13,18,19,21,27 there have been rela-tively few clinical trials which have investigated the success rates of im-pression materials.28,29 It is possible that the detail obtained with elasto-meric impression materials with the in vitro test specimens might be bet-ter than the detail obtained in vivo. This may be related to the different hydrophilicity of the materials in-vestigated and to the wetness of the tooth structure.2 Unlike under in vi-tro conditions, dentin, as a result of outward fluid flow from the pulp to the dentin, is an intrinsically hydrated tissue in vivo.30 Therefore, when the reproduction ability of an elastomeric impression material is tested, the wa-ter remaining on the prepared tooth surface should be considered. To simulate clinical conditions, artificial moisture may be created in various ways.10,12,13,18,20,21

Traditionally, prosthetic restora-tions are made on dental casts. One of the potential sources of error in the fabrication of a fixed prosthesis is the die material. A number of die materi-als are currently available, yet none of these satisfies all the desirable quali-ties of a die system.31 Currently, im-proved dental stones, despite their lower detail reproduction capabil-ity32,33 and abrasion resistance,17 are the most commonly used die mate-rials because of their acceptable di-mensional accuracy,34 low cost, and ease of manipulation. Although an-other cast material, polyurethane res-in, possesses high transverse strength, abrasion resistance, and detail repro-duction ability, it has lower dimen-sional stability than improved dental stones due to polymerization shrink-age.32,34,35 Kenyon et al34 also noted that polyurethane resin may show a combination of linear shrinkage and expansion, resulting in castings that

exceed the incisogingival dimension of the tooth impressed but that are small-er facioligually and mesiodistally.

Several studies have indicated that impression materials with low con-tact angles are more wettable with gypsum products.4-6,36,37 The wettabil-ity of impression materials may have a positive effect on the ability of im-pression materials to transfer detail.17 The results of these approaches war-rant investigation as to whether these VPS impression materials, which are more hydrophilic than polyether, are able to copy dentin surface detail better than PE. The purposes of this study were to determine in vitro 1) the ability of impression materials to reproduce detail in moist and dry sur-face conditions when human dentin is used as a substrate with simulated possible and ideal clinical conditions and 2) to document their ability to transfer those details onto the casts produced from those impressions. The null hypotheses tested were that all evaluated impression materials would show no significant difference in the reproduction or transference of detail to the casts.

MATERIAL AND METHODS

Wettability The impression materials used in

this investigation are listed in Table I. The materials were mixed and sy-ringed according to the manufactur-ers’ instructions. The environment was fixed at 20°C and 50% humidity to standardize the effects of tempera-ture and moisture. Distilled water was used as the test liquid. Eight speci-mens of each of the impression mate-rials were prepared. The thickness of each impression specimen was stan-dardized at 50 µm in a metal mold. At 25 seconds after the start of mixing, a water drop (4 µL) was placed on each impression material. Time-resolved static contact angle measurements were performed with an optical con-tact-angle meter (OCA 30; DataPhys-ics Instruments GmbH, Filderstadt,


103August 2012


Clinical ImplicationsWhen the moisture source is inherent dentinal fluid, elastomeric im-pression materials with different hydrophilicity may show the same ability to reproduce detail. Polyurethane resin reproduces fine details better than Type IV dental stone. The use of Type IV dental stone may result in a loss of detail because of its large particle size.

Statement of problem. It is not clear whether more hydrophilic impression materials are better able to copy and transfer dentin surface detail than less hydrophilic ones.

Purpose. The purpose of this study was to evaluate the reproduction of dentin surface detail by means of hydropho-bic and hydrophilic elastomeric impression materials under simulated pulpal pressure and their ability to transfer surface detail onto casts produced from such impressions.

Material and methods. The wettability of the impression materials (n=8) was determined by contact angle measure-ment with an evolution period of 135 seconds. Dentin moisture was provided by means of pulpal pressure simulation, and objective analyses were performed by measuring the average roughness value (Ra) with a 3-D optical profilometer (n=10). One specimen from each group was analyzed with scanning electron microscopy. Contact-angle values were analyzed with a repeated measures ANOVA, and detail reproduction was tested with 3-way ANOVA (α=.05). The Bon-ferroni correction was used to control Type I error for follow-up analyses.

Results. Contact angle measurements revealed significant differences depending on the impression material used and time of the measurement (P<.001). The Ra values of the hydrophilic impression materials, which were made from dry specimens, and the pulpal pressure simulated dentin surfaces did not differ from the dentin surfaces (P>.013). The hydrophobic impression material showed similar detail reproduction ability in a dry field, but loss of detail (evaluated subjectively) and increased roughness values (evaluated objectively) were recorded in a moisturized field (P=.004). Polyurethane-based cast material successfully reproduced the surface texture (P≥.006), whereas Type IV gypsum mate-rial was unable to reproduce this texture to the same extent.

Conclusions. The hydrophilic impression materials tested showed similar ability to reproduce detail under simu-lated pulpal pressure. Polyurethane-based cast material successfully reproduced the surface texture. (J Prosthet Dent 2012;108:102-113)

Surface detail reproduction under simulated pulpal pressure: A 3-dimensional optical profilometer and scanning electron microscopy evaluation

Ozlem Acar, DDS,a Selim Erkut, DDS, PhD,b and Manas Lakshmipathy, MSc

Baskent University, Ankara, Turkey

Supported by a grant-in-aid to scientific research No. D-DA09/02 from the Baskent University, Ankara, Turkey.

aResearch Fellow, Department of Prosthetics, Faculty of Dentistry.bAssociate Professor, Department of Prosthetics, Faculty of Dentistry.cApplication Engineer, Zygo Corporation, Middlefield, Conn.

The most common impression materials used are the vinyl polysi-loxanes (VPS) and polyethers (PE). Widespread use of VPS impression materials may be attributed to their

high accuracy, dimensional stabil-ity, and excellent elastic recovery.1 Polyethers are also highly accurate, but their flexibility is inferior to that of VPS.1 Although VPS impression

materials possess some advantages over polyether, their hydrophobic na-ture, which is related to the chemical structure of the material, results in significant disadvantages. VPS con-

tains hydrophobic aliphatic hydro-carbon groups which surround the siloxane bond, making this material hydrophobic in nature.2 In contrast to VPS, PE impression material, which has functional groups that attract and interact with water molecules, is hydrophilic.2 To overcome this limi-tation, manufacturers have incorpo-rated surfactants and marketed these as hydrophilic VPS materials.3 These materials show more wettability than conventional VPS,4-6 and are known to exhibit lower hydrophilicity than PE impression materials.7,8 However, recent studies have reported lower initial contact angle values (better hy-drophilicity) for recently introduced VPSs than for PEs.4,9 Increased hydro-philicity may be linked to the accurate reproduction of wet oral surfaces and increased wettability with gyp-sum slurry.9 However, Takahashi and Finger10 indicated that hydrophilicity may not be the key to enhanced sur-face detail reproduction.

To investigate the ability of im-pression materials to reproduce sur-face detail, different methods have been used. The American National Standards Institute/American Den-tal Association (ANSI/ADA) speci-fication No. 19 has identified what constitutes acceptable detail repro-duction for nonaqueous elastomeric impression materials.11 Some investi-gators who have used this procedure have evaluated the reproducibility of these impression materials.12,13 How-ever, other investigators have either poured the impression with gypsum slurry and investigated the detail of the cast and the related impres-sion14,15 or have evaluated only the detail of the cast.16,17 It is possible to identify 2 primary problems with this procedure. First, the results of these investigations are based on subjec-tive evaluations made by one or more examiners,12-17 and secondly, as noted by Kanehira et al,18 they disregard the nature of dental substrates such as enamel, dentin, and mucosa. In this regard, using a device that can ana-lyze surfaces may ensure an objective

evaluation,10,18-25 and using calibrated dentin specimens as reference sur-faces10,18,26 may be a more realistic ap-proach.

Although several in vitro stud-ies have evaluated various properties of elastomeric impression materi-als,9,12,13,18,19,21,27 there have been rela-tively few clinical trials which have investigated the success rates of im-pression materials.28,29 It is possible that the detail obtained with elasto-meric impression materials with the in vitro test specimens might be bet-ter than the detail obtained in vivo. This may be related to the different hydrophilicity of the materials in-vestigated and to the wetness of the tooth structure.2 Unlike under in vi-tro conditions, dentin, as a result of outward fluid flow from the pulp to the dentin, is an intrinsically hydrated tissue in vivo.30 Therefore, when the reproduction ability of an elastomeric impression material is tested, the wa-ter remaining on the prepared tooth surface should be considered. To simulate clinical conditions, artificial moisture may be created in various ways.10,12,13,18,20,21

Traditionally, prosthetic restora-tions are made on dental casts. One of the potential sources of error in the fabrication of a fixed prosthesis is the die material. A number of die materi-als are currently available, yet none of these satisfies all the desirable quali-ties of a die system.31 Currently, im-proved dental stones, despite their lower detail reproduction capabil-ity32,33 and abrasion resistance,17 are the most commonly used die mate-rials because of their acceptable di-mensional accuracy,34 low cost, and ease of manipulation. Although an-other cast material, polyurethane res-in, possesses high transverse strength, abrasion resistance, and detail repro-duction ability, it has lower dimen-sional stability than improved dental stones due to polymerization shrink-age.32,34,35 Kenyon et al34 also noted that polyurethane resin may show a combination of linear shrinkage and expansion, resulting in castings that

exceed the incisogingival dimension of the tooth impressed but that are small-er facioligually and mesiodistally.

Several studies have indicated that impression materials with low con-tact angles are more wettable with gypsum products.4-6,36,37 The wettabil-ity of impression materials may have a positive effect on the ability of im-pression materials to transfer detail.17 The results of these approaches war-rant investigation as to whether these VPS impression materials, which are more hydrophilic than polyether, are able to copy dentin surface detail better than PE. The purposes of this study were to determine in vitro 1) the ability of impression materials to reproduce detail in moist and dry sur-face conditions when human dentin is used as a substrate with simulated possible and ideal clinical conditions and 2) to document their ability to transfer those details onto the casts produced from those impressions. The null hypotheses tested were that all evaluated impression materials would show no significant difference in the reproduction or transference of detail to the casts.

MATERIAL AND METHODS

Wettability The impression materials used in

this investigation are listed in Table I. The materials were mixed and sy-ringed according to the manufactur-ers’ instructions. The environment was fixed at 20°C and 50% humidity to standardize the effects of tempera-ture and moisture. Distilled water was used as the test liquid. Eight speci-mens of each of the impression mate-rials were prepared. The thickness of each impression specimen was stan-dardized at 50 µm in a metal mold. At 25 seconds after the start of mixing, a water drop (4 µL) was placed on each impression material. Time-resolved static contact angle measurements were performed with an optical con-tact-angle meter (OCA 30; DataPhys-ics Instruments GmbH, Filderstadt,

104 Volume 108 Issue 2


105August 2012

Acar et al Acar et al

Germany). For each specimen, the measurements were started before the droplet touched the surface to record the entire process of jump to contact,7 and measurements were made at 8 time points (0, 5, 10, 20, 30, 40, 60, and 135 seconds). Measurement of the contact angles of the impression materials at different time points al-lowed the evaluation of time-related wettability. The total recording time of 135 seconds (0 to 135 seconds) was based on previous investigations and was long enough to evaluate the wet-tability of the materials.7,21

Detail Reproduction The project (D-DA09/02) was ap-

proved by the Institutional Review Board of Baskent University, Ankara, Turkey. To determine the surface de-tails, 178 noncarious extracted hu-man molars (from those aged 20 to 40 years) were collected. The teeth were stored in a 4°C thymol solu-tion (0.1%) and were used within 1 month of extraction. The occlusal enamel of each crown was removed at 2.5 mm occlusal to the cemento- enamel junction (CEJ), and the roots were removed at 1 mm apical to the CEJ with a coarse grit diamond ro-tary cutting instrument (6856 L-016; Gebr Brassler GmbH & Co. KG, Lem-go, Germany) under coolant water. Pulpal tissue was removed from the exposed pulp chamber. The remain-ing dentin thickness was adjusted to between 1.7 mm and 1.8 mm for each specimen by measuring with a pincer-type caliper (Aesculap AG, Tuttlingen, Germany). To standardize the dentin surface texture, the dentin thickness

was reduced by 1 mm with a modified aerator, without hand pressure, and with a tungsten carbide finishing bur (H284 – 014; Gebr Brassler GmbH & Co. KG). After filling the pulp cham-ber with cotton pellets and wax, the specimens were embedded in auto po-lymerizing acrylic resin (Steady-Resin; Scheu-Dental GmbH, Iserlohn, Ger-many), exposing the dentin surface 1 mm from the acrylic resin surface. The acrylic resin blocks had 1 mm thick stoppers that limited reduction depth. A new rotary cutting instru-ment was used after the preparation of every 3 dentin specimens. A total of 178 crown segments, each with a minimal remaining dentin thickness of 0.7 to 0.8 mm, were prepared. Before impressions were made, the prepared dentin surfaces were either dried or moisturized (pulpal pressure simula-tion). To simulate the latter in clini-cal conditions, specimens were kept under positive hydrostatic intrapulpal fluid pressure by means of pulp cham-bers filled with distilled water during the impression procedure. Tooth sec-tions were attached to a polymethyl-methacrylate plate (2 × 2 × 0.5 cm) with an 18 gauge stainless steel tube and cyanoacrylate adhesive (502 Su-per Glue; Evabond Group, New Taipei City, Taiwan). These specimens were connected to a hydraulic pressure de-vice that delivered 98 Pa pressure dur-ing impression making.38 Before the impression was made, a gentle blast of compressed air was applied to the dentin surface for 2 seconds from a distance of 20 cm to simulate clini-cal conditions. Dentin wetness was controlled by using a micromoisture meter (Periotron 8000; Oraflow, Inc,

Plainview, NY) designed to quantify submicroliter volumes of fluid. The other half of the specimens was main-tained under 40% moisture and 20 ±1°C stable ambient conditions for 48 hours. The moisture content of these dentin surfaces was also con-trolled with the micromoisture meter. Diagrams of specimen preparation are shown in Figure 1. Impressions of dry and wet dentin surfaces were obtained. All the impression materi-als used (Table I) were of a light body consistency. All materials were used according to manufacturers’ instruc-tions, with approved ancillary equip-ment, where appropriate. Custom-made polymethylmethacrylate plates (2 × 2 × 0.5 cm) were used as impres-sion trays. After the 2 cm portions were discharged, mixed portions were then used. The impression material was allowed to polymerize for twice the manufacturer’s recommended time to allow for complete polymer-ization at room temperature. The im-pressions were removed and half of them were immediately poured with working die material. The surface of individual materials (10 impression specimens for each impression mate-rial from dry and moisturized dentin surfaces as well as 10 polyurethane resin specimens for each group) and 10 dentin specimens as references were analyzed with a 3-dimension-al (3-D) surface profiler (NewView 7300; Zygo Corp, Middlefield, Conn) incorporating noncontact scanning white-light interferometry over an area of 0.35 × 0.2 mm with ×400 magnification and 0.5 µm lateral resolution. Three-dimensional inter-ferograms of the specimens were re-

Impregum Garant L DuoSoft, Batch No: 273776

Panasil Initial Contact Light, Batch No: 110271

Panasil Contact Plus, Batch No: 50561

Panasil Contact Plus Nonsurfactant (Test material)

*Test material without surfactant

IGL

PIC

PC

PCNS*

3M ESPE AG, Seefeld, Germany

Kettenbach GmbH & Co. KG, Eschenburg, Germany



Code

Polyether

VPS

VPS

VPS

Polymer Type ManufacturerImpression Materials/Batch No.

Table I. Elastomeric impression materials used

corded and the Ra surface roughness value was obtained for each specimen with image analysis software (Metro-Pro; Zygo Corp). Four measurements were made along the long axis of each specimen, and the mean value was re-corded for the Ra parameter, defined as the arithmetic average value of all departures of the profile above and below a mean line through the sam-pling length. One specimen from each group was analyzed with scanning electron microscopy (SEM) (Quan-to 200 F; FEI Company, Eindhoven, Netherlands).

To avoid possible loss of detail due to the varying grain dimensions of dif-ferent stone brands, 3 different Type IV dental stone products (Table II) were evaluated in a pilot study. Dentin and its polyether impression replicas were prepared by following the proce-dure described for dry dentin surfac-es. Type IV dental stones were vacuum mixed following the manufacturer’s

instructions and poured onto impres-sion specimens for profilometer and SEM analysis. Polyurethane resin cast material (Alpha Die Top; Schütz Den-tal GmbH, Rosbach, Germany) (Table II) was chosen based on the results of a pilot study. The die material, was used according to the manufacturer‘s instructions with respect to the liquid to powder ratio, mixing time, and po-lymerization time.

A total specimen size of 102 (n=6) was required to detect an Ra difference of at least 0.23 µm between the 2 test material groups, within both dry and wet surfaces, and with a power of 85% at the 5% significance level. The 0.23 µm value difference was taken from the study of Kanehira et al.18

Specimen size estimation was performed by us-ing software (NCSS and PASS 2000; NCSS Inc, Kaysville, Utah).

Data analysis was performed with statistical software (Statistical Pro-gram for Social Sciences, v11.5; SPSS,

Inc, Chicago, Ill). Whether the distri-butions of continuous variables were normal or not was determined by us-ing the Shapiro Wilk test. Homoge-neity of variance was evaluated with the Levene test. Data were shown as mean ± standard deviation (SD).

Repeated measures of analysis of variance (ANOVA) was used to com-pare time-dependent changes on con-tact angle values of impression mate-rials (independent factor) at an alpha of .05. The Greenhouse-Geisser test statistic was used to determine the statistical significance of the material × time interaction term.

Three-way ANOVA was used to compare detail reproduction at an alpha of .05. The first independent factor was test materials. The second was type of specimens (elastomeric impression materials and polyure-thane resin) and the third was sur-faces (dried and moisturized). When the P value of the 3-way interaction

1 Schematic showing how dry and moisturized dentin surfaces were created: (a) standardized tooth surface, (b) production of dry and moisturized (with pulpal pressure simulation) dentin surfaces, (c) moistness and dryness control with micromoisture meter.

Type IV dental stone



Polyurethane resin

Prostone 21

Duralit S

Fujirock EP

Alpha Die Top

BPB Formula, Walkenried, Germany

Degussa AG, Geschaftsbereich Dental, Hanau, Germany

GC, Leuven, Belgium

Schütz Dental Group, Rosbach, Germany

Trade Name ManufacturerProduct

Table II. Cast materials evaluated



105August 2012


Germany). For each specimen, the measurements were started before the droplet touched the surface to record the entire process of jump to contact,7 and measurements were made at 8 time points (0, 5, 10, 20, 30, 40, 60, and 135 seconds). Measurement of the contact angles of the impression materials at different time points al-lowed the evaluation of time-related wettability. The total recording time of 135 seconds (0 to 135 seconds) was based on previous investigations and was long enough to evaluate the wet-tability of the materials.7,21

Detail Reproduction The project (D-DA09/02) was ap-

proved by the Institutional Review Board of Baskent University, Ankara, Turkey. To determine the surface de-tails, 178 noncarious extracted hu-man molars (from those aged 20 to 40 years) were collected. The teeth were stored in a 4°C thymol solu-tion (0.1%) and were used within 1 month of extraction. The occlusal enamel of each crown was removed at 2.5 mm occlusal to the cemento- enamel junction (CEJ), and the roots were removed at 1 mm apical to the CEJ with a coarse grit diamond ro-tary cutting instrument (6856 L-016; Gebr Brassler GmbH & Co. KG, Lem-go, Germany) under coolant water. Pulpal tissue was removed from the exposed pulp chamber. The remain-ing dentin thickness was adjusted to between 1.7 mm and 1.8 mm for each specimen by measuring with a pincer-type caliper (Aesculap AG, Tuttlingen, Germany). To standardize the dentin surface texture, the dentin thickness

was reduced by 1 mm with a modified aerator, without hand pressure, and with a tungsten carbide finishing bur (H284 – 014; Gebr Brassler GmbH & Co. KG). After filling the pulp cham-ber with cotton pellets and wax, the specimens were embedded in auto po-lymerizing acrylic resin (Steady-Resin; Scheu-Dental GmbH, Iserlohn, Ger-many), exposing the dentin surface 1 mm from the acrylic resin surface. The acrylic resin blocks had 1 mm thick stoppers that limited reduction depth. A new rotary cutting instru-ment was used after the preparation of every 3 dentin specimens. A total of 178 crown segments, each with a minimal remaining dentin thickness of 0.7 to 0.8 mm, were prepared. Before impressions were made, the prepared dentin surfaces were either dried or moisturized (pulpal pressure simula-tion). To simulate the latter in clini-cal conditions, specimens were kept under positive hydrostatic intrapulpal fluid pressure by means of pulp cham-bers filled with distilled water during the impression procedure. Tooth sec-tions were attached to a polymethyl-methacrylate plate (2 × 2 × 0.5 cm) with an 18 gauge stainless steel tube and cyanoacrylate adhesive (502 Su-per Glue; Evabond Group, New Taipei City, Taiwan). These specimens were connected to a hydraulic pressure de-vice that delivered 98 Pa pressure dur-ing impression making.38 Before the impression was made, a gentle blast of compressed air was applied to the dentin surface for 2 seconds from a distance of 20 cm to simulate clini-cal conditions. Dentin wetness was controlled by using a micromoisture meter (Periotron 8000; Oraflow, Inc,

Plainview, NY) designed to quantify submicroliter volumes of fluid. The other half of the specimens was main-tained under 40% moisture and 20 ±1°C stable ambient conditions for 48 hours. The moisture content of these dentin surfaces was also con-trolled with the micromoisture meter. Diagrams of specimen preparation are shown in Figure 1. Impressions of dry and wet dentin surfaces were obtained. All the impression materi-als used (Table I) were of a light body consistency. All materials were used according to manufacturers’ instruc-tions, with approved ancillary equip-ment, where appropriate. Custom-made polymethylmethacrylate plates (2 × 2 × 0.5 cm) were used as impres-sion trays. After the 2 cm portions were discharged, mixed portions were then used. The impression material was allowed to polymerize for twice the manufacturer’s recommended time to allow for complete polymer-ization at room temperature. The im-pressions were removed and half of them were immediately poured with working die material. The surface of individual materials (10 impression specimens for each impression mate-rial from dry and moisturized dentin surfaces as well as 10 polyurethane resin specimens for each group) and 10 dentin specimens as references were analyzed with a 3-dimension-al (3-D) surface profiler (NewView 7300; Zygo Corp, Middlefield, Conn) incorporating noncontact scanning white-light interferometry over an area of 0.35 × 0.2 mm with ×400 magnification and 0.5 µm lateral resolution. Three-dimensional inter-ferograms of the specimens were re-

Impregum Garant L DuoSoft, Batch No: 273776

Panasil Initial Contact Light, Batch No: 110271

Panasil Contact Plus, Batch No: 50561

Panasil Contact Plus Nonsurfactant (Test material)

*Test material without surfactant

IGL

PIC

PC

PCNS*

3M ESPE AG, Seefeld, Germany




Code

Polyether

VPS

VPS

VPS

Polymer Type ManufacturerImpression Materials/Batch No.

Table I. Elastomeric impression materials used

corded and the Ra surface roughness value was obtained for each specimen with image analysis software (Metro-Pro; Zygo Corp). Four measurements were made along the long axis of each specimen, and the mean value was re-corded for the Ra parameter, defined as the arithmetic average value of all departures of the profile above and below a mean line through the sam-pling length. One specimen from each group was analyzed with scanning electron microscopy (SEM) (Quan-to 200 F; FEI Company, Eindhoven, Netherlands).

To avoid possible loss of detail due to the varying grain dimensions of dif-ferent stone brands, 3 different Type IV dental stone products (Table II) were evaluated in a pilot study. Dentin and its polyether impression replicas were prepared by following the proce-dure described for dry dentin surfac-es. Type IV dental stones were vacuum mixed following the manufacturer’s

instructions and poured onto impres-sion specimens for profilometer and SEM analysis. Polyurethane resin cast material (Alpha Die Top; Schütz Den-tal GmbH, Rosbach, Germany) (Table II) was chosen based on the results of a pilot study. The die material, was used according to the manufacturer‘s instructions with respect to the liquid to powder ratio, mixing time, and po-lymerization time.

A total specimen size of 102 (n=6) was required to detect an Ra difference of at least 0.23 µm between the 2 test material groups, within both dry and wet surfaces, and with a power of 85% at the 5% significance level. The 0.23 µm value difference was taken from the study of Kanehira et al.18

Specimen size estimation was performed by us-ing software (NCSS and PASS 2000; NCSS Inc, Kaysville, Utah).

Data analysis was performed with statistical software (Statistical Pro-gram for Social Sciences, v11.5; SPSS,

Inc, Chicago, Ill). Whether the distri-butions of continuous variables were normal or not was determined by us-ing the Shapiro Wilk test. Homoge-neity of variance was evaluated with the Levene test. Data were shown as mean ± standard deviation (SD).

Repeated measures of analysis of variance (ANOVA) was used to com-pare time-dependent changes on con-tact angle values of impression mate-rials (independent factor) at an alpha of .05. The Greenhouse-Geisser test statistic was used to determine the statistical significance of the material × time interaction term.

Three-way ANOVA was used to compare detail reproduction at an alpha of .05. The first independent factor was test materials. The second was type of specimens (elastomeric impression materials and polyure-thane resin) and the third was sur-faces (dried and moisturized). When the P value of the 3-way interaction

1 Schematic showing how dry and moisturized dentin surfaces were created: (a) standardized tooth surface, (b) production of dry and moisturized (with pulpal pressure simulation) dentin surfaces, (c) moistness and dryness control with micromoisture meter.




Polyurethane resin

Prostone 21

Duralit S

Fujirock EP

Alpha Die Top

BPB Formula, Walkenried, Germany

Degussa AG, Geschaftsbereich Dental, Hanau, Germany

GC, Leuven, Belgium

Schütz Dental Group, Rosbach, Germany

Trade Name ManufacturerProduct

Table II. Cast materials evaluated



107August 2012


was significant, to determine which group differed from which other, the post hoc Tukey Honestly Significant Difference (HSD) or the Student t test, where appropriate, was used. According to the Bonferroni Correc-tion (4 potential multiple comparison test), the level of statistical signifi-cance was set at .0125 (.05/4) for the post hoc Tukey HSD test. When the P value from the Student t test was less than .006 (.05/8), it was considered statistically significant regarding the Bonferroni Correction (8 potential multiple comparison test).

RESULTS

Wettability

Figure 2 shows the mean contact angle values with water (n=8) on un-polymerized impression materials. The contact angle values were deter-mined at 8 time points. The IGL con-tact angle value started at 67.5 ±3.2 degrees, decreased to 38.3 ±2.2 de-grees at 5 seconds, 22.2 ±1.8 degrees at 30 seconds, and 14.6 ±2.7 degrees at 135 seconds (the end of the evalu-ation period). PIC contact angle val-ues started at 71.3 ±10.7 degrees, decreased to 57.0 ±3.2 after 5 sec-onds, and 54.8 ±2.5 after 10 seconds, and 15.4 ±3.6 after 20 seconds and reached to 0.5 ±0.1 degrees after 30 seconds. The PC contact angle values started at 74.3 ±3.3 degrees and end-ed at approximately 58.7 ±2.3. The contact angle values on PCNS were between 88.1 ±4.4 and 78.3 ±4.7 degrees. Maximum decrease at con-tact angle values from 0 to 5 seconds occurred in the IGL group, and mini-mum decrease in the PCNS and PC groups (P<.001). After 10 seconds, IGL showed maximum decrease again and PIC showed higher decrease over PCNS (P<.001). After 20 seconds, PIC reached the polyether IGL’s contact angle, at approximately the 17 second time point (P=.002). From the 30 sec-ond time point to the end of the eval-uation period, PIC decreased more than the others (P<.001). Throughout

the evaluation period, PC and PCNS showed similar decrease of the con-tact angle (P>.002). The statistical results for unpolymerized impression materials are shown in Table III.

Detail Reproduction

The selection of the cast material was based on the results of the pilot study. It appears that the dentin and polyether specimens exhibited similar roughness numbers, while the values of the dental stone specimens were significantly higher (Fig. 3). Three-dimensional interferograms (Fig. 4) and SEM images (Fig. 5) of dentin, polyether, and Fujirock EP stone spec-imens are presented. The reproduc-tion of dry dentin surface detail on the polyether was acceptable, but the in-

herent microporosity of dental stones hid fine and narrow cutting troughs. In other words, none of the Type IV dental stones used in this study was capable of transferring the detail of the tungsten carbide finishing bur. As a result of the pilot study, another die material, polyurethane resin, capable of reproducing 1 to 2 µm of detail32,33 was chosen as the cast material.

The mean surface roughness val-ues (Ra) and standard deviations of dentin (n=10), impression mate-rial (n=10), and polyurethane resin (n=10) are shown in Table IV. Three-way ANOVA results for surface rough-ness are shown in Table V. The 3-way interaction term of ANOVA was found to be statistically significant (F=8.3 and P<.001). The statistical significance of all possible 2-way in-

2 Contact angle development. Mean contact angles and SDs. Water droplet (4 µL) placed 25 seconds after mix (material thickness 50 µm). Standard deviations indicated as error bars (See Table I for abbreviations).

Table III. Repeated Measures of ANOVA results for wettability

[Q3]

[Q2]

120

Con

tact

Ang

le (

Deg

rees

)Time (Seconds)

60

80

100

40

20

–20

00 5 20 3010 40 60 135

IGLPIC

PCPCNS

Within-subjects effects

Time

Material × Time

Error (Time)

Between-subjects effects

Intercept

Material

Error

40278

30455

1336

667146

153952

1602

Type IIISum of Squares

23161

5836

27

667146

51317

57

MeanSquares

844

213

11662

897

F

1.7

5.2

48.7

1

3

28

df

<.001

<.001

<.001

<.001

PSource

teraction terms was ignored because of the significant result of the 3-way interaction term.

According to the multiple com-parisons, there were significant differ-ences in the ability of the impression materials to reproduce detail from the dry dentin surface (D) (P=.002). The Ra values obtained from PC (D) showed statistically higher rough-ness than PCNS (D) (P=.004). For dry conditions, no significant differ-ences were observed in the Ra values between impression materials and dentin surfaces (P>.013). There were significant differences in the detail reproduction ability of impression materials from pulpal pressure simu-lated dentin surfaces (PP) (P<.001). PCNS showed higher Ra values than both dentin (P=.004) and other im-pression materials [IGL (P=.008), PIC (P<.001), PC (P<.001)]. For moist conditions, no significant differ-ences were observed in the Ra value between impression materials and dentin surfaces for IGL, PIC, and PC. Representative 3-D oblique plots (interferograms) and SEM images revealed that IGL (Fig. 6), PIC (Fig. 7), and PC (Fig. 8) impression mate-rials reproduced the surface cutting troughs on dentin, under moist sur-face conditions. PCNS impressions replicated dentin similarly well in dry conditions, whereas impressions from pulpal pressure simulated den-tin showed rounded surface texture instead of scratching details, as seen on the 3-D interferograms (Fig. 9A). In addition, SEM evaluation showed that PCNS impressions from pulpal pressure simulated dentin showed loss of detail because water droplets hid the scratching details (Fig. 9B). No significant differences were ob-served in the Ra values between im-pression and resin surfaces (P>.006) (Table IV). Polyurethane resin-based cast material successfully transferred the impression detail as shown in 3-D oblique plots (interferograms) (Fig. 10). These representative specimens were chosen from pulpal pressure simulated groups. Therefore, there is

4 Three-dimensional oblique surface plots (interferograms) (×400) of representative specimens from pilot study: A, dentin prepared with finish-ing bur. B, IGL impression surface from air dried dentin; cutting grooves produced during preparation of dentin clearly seen on IGL impression. C, Fujirock stone cast; cutting grooves not visible or discernible.

[Q3]

[Q2]

2.5

Rou

ghne

ss R

a (µ

m)

1

1.5

2

0.5

0

Dentin

Impression Material

Type IV Dental Stone

3 Graph of mean Ra values for dentin, impression surface (IGL), and Type IV dental stone (Pilot study).

A

B

C



107August 2012


was significant, to determine which group differed from which other, the post hoc Tukey Honestly Significant Difference (HSD) or the Student t test, where appropriate, was used. According to the Bonferroni Correc-tion (4 potential multiple comparison test), the level of statistical signifi-cance was set at .0125 (.05/4) for the post hoc Tukey HSD test. When the P value from the Student t test was less than .006 (.05/8), it was considered statistically significant regarding the Bonferroni Correction (8 potential multiple comparison test).

RESULTS

Wettability

Figure 2 shows the mean contact angle values with water (n=8) on un-polymerized impression materials. The contact angle values were deter-mined at 8 time points. The IGL con-tact angle value started at 67.5 ±3.2 degrees, decreased to 38.3 ±2.2 de-grees at 5 seconds, 22.2 ±1.8 degrees at 30 seconds, and 14.6 ±2.7 degrees at 135 seconds (the end of the evalu-ation period). PIC contact angle val-ues started at 71.3 ±10.7 degrees, decreased to 57.0 ±3.2 after 5 sec-onds, and 54.8 ±2.5 after 10 seconds, and 15.4 ±3.6 after 20 seconds and reached to 0.5 ±0.1 degrees after 30 seconds. The PC contact angle values started at 74.3 ±3.3 degrees and end-ed at approximately 58.7 ±2.3. The contact angle values on PCNS were between 88.1 ±4.4 and 78.3 ±4.7 degrees. Maximum decrease at con-tact angle values from 0 to 5 seconds occurred in the IGL group, and mini-mum decrease in the PCNS and PC groups (P<.001). After 10 seconds, IGL showed maximum decrease again and PIC showed higher decrease over PCNS (P<.001). After 20 seconds, PIC reached the polyether IGL’s contact angle, at approximately the 17 second time point (P=.002). From the 30 sec-ond time point to the end of the eval-uation period, PIC decreased more than the others (P<.001). Throughout

the evaluation period, PC and PCNS showed similar decrease of the con-tact angle (P>.002). The statistical results for unpolymerized impression materials are shown in Table III.

Detail Reproduction

The selection of the cast material was based on the results of the pilot study. It appears that the dentin and polyether specimens exhibited similar roughness numbers, while the values of the dental stone specimens were significantly higher (Fig. 3). Three-dimensional interferograms (Fig. 4) and SEM images (Fig. 5) of dentin, polyether, and Fujirock EP stone spec-imens are presented. The reproduc-tion of dry dentin surface detail on the polyether was acceptable, but the in-

herent microporosity of dental stones hid fine and narrow cutting troughs. In other words, none of the Type IV dental stones used in this study was capable of transferring the detail of the tungsten carbide finishing bur. As a result of the pilot study, another die material, polyurethane resin, capable of reproducing 1 to 2 µm of detail32,33 was chosen as the cast material.

The mean surface roughness val-ues (Ra) and standard deviations of dentin (n=10), impression mate-rial (n=10), and polyurethane resin (n=10) are shown in Table IV. Three-way ANOVA results for surface rough-ness are shown in Table V. The 3-way interaction term of ANOVA was found to be statistically significant (F=8.3 and P<.001). The statistical significance of all possible 2-way in-

2 Contact angle development. Mean contact angles and SDs. Water droplet (4 µL) placed 25 seconds after mix (material thickness 50 µm). Standard deviations indicated as error bars (See Table I for abbreviations).

Table III. Repeated Measures of ANOVA results for wettability

[Q3]

[Q2]

120

Con

tact

Ang

le (

Deg

rees

)

Time (Seconds)

60

80

100

40

20

–20

00 5 20 3010 40 60 135

IGLPIC

PCPCNS

Within-subjects effects

Time

Material × Time

Error (Time)

Between-subjects effects

Intercept

Material

Error

40278

30455

1336

667146

153952

1602


23161

5836

27

667146

51317

57

MeanSquares

844

213

11662

897

F

1.7

5.2

48.7

1

3

28

df

<.001

<.001

<.001

<.001

PSource

teraction terms was ignored because of the significant result of the 3-way interaction term.

According to the multiple com-parisons, there were significant differ-ences in the ability of the impression materials to reproduce detail from the dry dentin surface (D) (P=.002). The Ra values obtained from PC (D) showed statistically higher rough-ness than PCNS (D) (P=.004). For dry conditions, no significant differ-ences were observed in the Ra values between impression materials and dentin surfaces (P>.013). There were significant differences in the detail reproduction ability of impression materials from pulpal pressure simu-lated dentin surfaces (PP) (P<.001). PCNS showed higher Ra values than both dentin (P=.004) and other im-pression materials [IGL (P=.008), PIC (P<.001), PC (P<.001)]. For moist conditions, no significant differ-ences were observed in the Ra value between impression materials and dentin surfaces for IGL, PIC, and PC. Representative 3-D oblique plots (interferograms) and SEM images revealed that IGL (Fig. 6), PIC (Fig. 7), and PC (Fig. 8) impression mate-rials reproduced the surface cutting troughs on dentin, under moist sur-face conditions. PCNS impressions replicated dentin similarly well in dry conditions, whereas impressions from pulpal pressure simulated den-tin showed rounded surface texture instead of scratching details, as seen on the 3-D interferograms (Fig. 9A). In addition, SEM evaluation showed that PCNS impressions from pulpal pressure simulated dentin showed loss of detail because water droplets hid the scratching details (Fig. 9B). No significant differences were ob-served in the Ra values between im-pression and resin surfaces (P>.006) (Table IV). Polyurethane resin-based cast material successfully transferred the impression detail as shown in 3-D oblique plots (interferograms) (Fig. 10). These representative specimens were chosen from pulpal pressure simulated groups. Therefore, there is

4 Three-dimensional oblique surface plots (interferograms) (×400) of representative specimens from pilot study: A, dentin prepared with finish-ing bur. B, IGL impression surface from air dried dentin; cutting grooves produced during preparation of dentin clearly seen on IGL impression. C, Fujirock stone cast; cutting grooves not visible or discernible.

[Q3]

[Q2]

2.5

Rou

ghne

ss R

a (µ

m)

1

1.5

2

0.5

0

Dentin

Impression Material

Type IV Dental Stone

3 Graph of mean Ra values for dentin, impression surface (IGL), and Type IV dental stone (Pilot study).

A

B

C



109August 2012


A B C

5 SEM photographs (×100 magnification) of representative specimens from pilot study: A, dentin prepared with finishing bur. B, IGL impression surface from air-dried dentin; cutting grooves produced during preparation of dentin clearly seen on IGL impression. C, Fujirock stone cast; cutting grooves not visible or discernible.

(Ra) Arithmetic mean roughness(a) 1-way ANOVA, Bonferroni correction (because of the 4 multiple comparisons); P<.013 statistical significance, (b) Student’s t test, Bonferroni correction (because of the 8 multiple comparisons); P<.006 statistical significance. (A) PC vs PCNS (P<.013), (B) Dentin vs PCNS (P<.013), (C) IGL vs PCNS (P<.013), (D) PIC vs PCNS (P<.013).

0.41±0.06C

0.36±0.08D

0.34±0.06A

0.68±0.35ABCD

<.001

Dentin Dry (D) Pulpal Pressure (PP)Impression Material

0.42±0.07C

0.34±0.05D

0.39±0.09A

1.30±0.74ABCD

<.001

Resin

.754

.533

.100

.028

Pb

0.48 ±0.10

0.36±0.06

0.32±0.08A

0.54±0.23A

.002

0.39±0.12B

IGL

PIC

PC

PCNS

Pa

Impression Material

0.35±0.10

0.39±0.13

0.35±0.04

0.32±0.10

.541

Resin

.009

.554

.282

.011

Pb

Table IV. Surface roughness (mean ± SD) of dentin, impression material (under dry and pulpal pressure simulated surface condition), and resin (in µm)

Table V. Sources of Variation in 3-Way ANOVA results for surface roughness

Test Material (TM)

Type of Specimen (TS)

Surface (S)

TM × TS

TM × S

TS × S

TM × TS × S

Error

Total

3.5

0.1

0.8

0.4

2.4

0.6

1.3

7.3

16.2


1.2

0.1

0.8

0.1

0.8

0.6

0.4

0.1

MeanSquares

23.2

1.7

15.7

2.4

15.9

11.5

8.3

F

3

1

1

3

3

1

3

144

159

df

<.001

.192

<.001

.072

<.001

<.001

<.001

PSource

6 Impregum Garant L DuoSoft (IGL). A, 3-D oblique surface plot (interferogram) of impression surface from pulpal pressure simulated dentin (See Fig. 4B for dry con-dition). Specimen best representing mean condition was chosen for 3-D oblique surface plots. B, SEM images of impression surface from pulpal pressure simulated dentin (×100) (See Fig. 5B for dry condition).

7 Panasil Initial Contact (PIC). A, 3-D oblique surface plot (interferogram) of impression surface from pulpal pressure simulated dentin. Specimen best representing mean condition chosen for 3-D oblique surface plots. B, SEM images of impression surface from pulpal pressure simulated dentin surface (×100).

A

B

A

B

a loss of detail and rounded texture on the resin images of PCNS impres-sions (Fig. 10D).

DISCUSSION The first part of the null hypoth-

esis, that all tested impression mate-rials would show no significant dif-ference in the reproduction of detail, was rejected, whereas the second part of the null hypothesis, that all tested impression materials would show no significant difference in transferring details to casts, was not rejected. The ability of an impression material to reproduce detail on a moist surface is a function of material properties such as viscosity and wettability.21,26 Ger-man et al21 indicated that 150 seconds after the start of mixing, elastomeric impression materials still have low vis-

cosity. Mondon et al7 showed that the most rapid changes in the wettability of nonpolymerized elastomeric im-pression materials occurred during the first 40 seconds. Moreover, the time after mixing had a significant effect on wettability, where time and contact angle were positively correlated.8,9 In the present study, the total recording time of 135 seconds was long enough to determine significant changes. There is no agreement as to which ini-tial time point should be chosen for the contact angle measurements of the unpolymerized elastomeric impression materials.7-9 Therefore, the duration of clinic procedure was calculated in a pilot study. In this pilot study, the total working time, starting with mix-ing the impression material and fin-ishing when the impression tray was fully loaded, was calculated. A mean

value (25 seconds) was determined by calculating the total working time for each of the 8 different clinicians. Throughout the evaluation period, PIC, which showed the strongest hy-drophilization (decrease in contact angle values9) reached the hydrophi-licity of polyether IGL after 17 sec-onds. This is not in agreement with the findings of a previous study that showed this equalization to occur af-ter 0.28 seconds.9 Rupp et al9 showed that humidity level can influence the hydrophilic behavior of the impres-sion material. Discrepancies among these findings may be due to differ-ences in humidity.

American National Standards In-stitute (ANSI)/American Dental As-sociation (ADA) specification No. 19 states that elastomeric impression material should be able to continu-



109August 2012


A B C

5 SEM photographs (×100 magnification) of representative specimens from pilot study: A, dentin prepared with finishing bur. B, IGL impression surface from air-dried dentin; cutting grooves produced during preparation of dentin clearly seen on IGL impression. C, Fujirock stone cast; cutting grooves not visible or discernible.

(Ra) Arithmetic mean roughness(a) 1-way ANOVA, Bonferroni correction (because of the 4 multiple comparisons); P<.013 statistical significance, (b) Student’s t test, Bonferroni correction (because of the 8 multiple comparisons); P<.006 statistical significance. (A) PC vs PCNS (P<.013), (B) Dentin vs PCNS (P<.013), (C) IGL vs PCNS (P<.013), (D) PIC vs PCNS (P<.013).

0.41±0.06C

0.36±0.08D

0.34±0.06A

0.68±0.35ABCD

<.001

Dentin Dry (D) Pulpal Pressure (PP)Impression Material

0.42±0.07C

0.34±0.05D

0.39±0.09A

1.30±0.74ABCD

<.001

Resin

.754

.533

.100

.028

Pb

0.48 ±0.10

0.36±0.06

0.32±0.08A

0.54±0.23A

.002

0.39±0.12B

IGL

PIC

PC

PCNS

Pa

Impression Material

0.35±0.10

0.39±0.13

0.35±0.04

0.32±0.10

.541

Resin

.009

.554

.282

.011

Pb

Table IV. Surface roughness (mean ± SD) of dentin, impression material (under dry and pulpal pressure simulated surface condition), and resin (in µm)

Table V. Sources of Variation in 3-Way ANOVA results for surface roughness

Test Material (TM)

Type of Specimen (TS)

Surface (S)

TM × TS

TM × S

TS × S

TM × TS × S

Error

Total

3.5

0.1

0.8

0.4

2.4

0.6

1.3

7.3

16.2


1.2

0.1

0.8

0.1

0.8

0.6

0.4

0.1

MeanSquares

23.2

1.7

15.7

2.4

15.9

11.5

8.3

F

3

1

1

3

3

1

3

144

159

df

<.001

.192

<.001

.072

<.001

<.001

<.001

PSource

6 Impregum Garant L DuoSoft (IGL). A, 3-D oblique surface plot (interferogram) of impression surface from pulpal pressure simulated dentin (See Fig. 4B for dry con-dition). Specimen best representing mean condition was chosen for 3-D oblique surface plots. B, SEM images of impression surface from pulpal pressure simulated dentin (×100) (See Fig. 5B for dry condition).

7 Panasil Initial Contact (PIC). A, 3-D oblique surface plot (interferogram) of impression surface from pulpal pressure simulated dentin. Specimen best representing mean condition chosen for 3-D oblique surface plots. B, SEM images of impression surface from pulpal pressure simulated dentin surface (×100).

A

B

A

B

a loss of detail and rounded texture on the resin images of PCNS impres-sions (Fig. 10D).

DISCUSSION The first part of the null hypoth-

esis, that all tested impression mate-rials would show no significant dif-ference in the reproduction of detail, was rejected, whereas the second part of the null hypothesis, that all tested impression materials would show no significant difference in transferring details to casts, was not rejected. The ability of an impression material to reproduce detail on a moist surface is a function of material properties such as viscosity and wettability.21,26 Ger-man et al21 indicated that 150 seconds after the start of mixing, elastomeric impression materials still have low vis-

cosity. Mondon et al7 showed that the most rapid changes in the wettability of nonpolymerized elastomeric im-pression materials occurred during the first 40 seconds. Moreover, the time after mixing had a significant effect on wettability, where time and contact angle were positively correlated.8,9 In the present study, the total recording time of 135 seconds was long enough to determine significant changes. There is no agreement as to which ini-tial time point should be chosen for the contact angle measurements of the unpolymerized elastomeric impression materials.7-9 Therefore, the duration of clinic procedure was calculated in a pilot study. In this pilot study, the total working time, starting with mix-ing the impression material and fin-ishing when the impression tray was fully loaded, was calculated. A mean

value (25 seconds) was determined by calculating the total working time for each of the 8 different clinicians. Throughout the evaluation period, PIC, which showed the strongest hy-drophilization (decrease in contact angle values9) reached the hydrophi-licity of polyether IGL after 17 sec-onds. This is not in agreement with the findings of a previous study that showed this equalization to occur af-ter 0.28 seconds.9 Rupp et al9 showed that humidity level can influence the hydrophilic behavior of the impres-sion material. Discrepancies among these findings may be due to differ-ences in humidity.

American National Standards In-stitute (ANSI)/American Dental As-sociation (ADA) specification No. 19 states that elastomeric impression material should be able to continu-



111August 2012


8 Panasil Contact Plus (PC). A, 3-D oblique surface plot (interferogram) of impression surface from pulpal pressure simulated dentin. Specimen best representing mean condition chosen for 3-D oblique surface plots. B, SEM images of impression surface from pulpal pressure simulated dentin (×100).

A

B

9 Panasil Contact Plus Non-Surfactant (PCNS). A, 3-D oblique surface plot (interferogram) of impression surface from pulpal pressure simulated dentin. Specimen best repre-senting mean condition chosen for 3-D oblique surface plots. B, SEM images of impression surface from pulpal pressure simulated dentin (×100).

10 Three-dimensional oblique surface plot (interferogram) of resin surface. A, Impregum Garant L DuoSoft. B, Panasil Initial Contact. C, Panasil Contact. D, Panasil Contact Plus Non-Surfactant.

A

B

ously replicate 1 of the 0.02-mm wide horizontal lines in 2 of 3 specimens prepared from a calibrated metal die model,11 but, because of the struc-tural difference between metal and dentin, its clinical significance is not clear.2,18,21 Nonetheless, using dentin as the reference surface brings with it standardization problems. In most of the studies, the dentin surface was prepared by grinding the teeth with wet SiC paper,18,26 whereas in a clini-cal situation, teeth are prepared with different cutting instruments, such as diamond, tungsten carbide, and tungsten carbide finishing burs. In the present study, a tungsten carbide finishing bur was used because of its contributions to marginal fit.39

Instead of the ANSI/ADA detail reproduction test, the combined use of SEM and profilometry has been popular for analyzing the detail re-production ability of impression and cast materials.10,20,23,32 Although the 2-D SEM technique does not provide roughness parameters or quantitative roughness values directly, it can be used in surface roughness analysis.32 In the present study, the 2-D SEM image of PCNS impression material from a moisturized dentin surface is clearly indicative of fidelity loss. The recognized disadvantages of con-tact profilometry are the distortion or abrasion of the specimen surface and the resolution of the instrument due to large tip size, which may com-promise the accuracy of measure-ments.23,32 However, from the data gathered from noncontact profiling techniques, it is possible to create a 3-D image of the surface in addition to the quantitative roughness val-ues.24 Rodriguez et al22 showed that the measurement of the noncontact laser profilometer is affected by the color and transparency of the materi-als. In the present study, a 3-D surface profilometer incorporating scanning white-light interferometry was used. Delong et al25 showed that color does not affect the digitizing performance of a white light digitizer.

It was clear that dentin wetness

is important during the impression procedure.12,13,20,21 To the authors’ knowledge, the inclusion of pulpal pressure simulation to evaluate detail reproduction has not been used in a previous study. In this study, dentin moisture was provided to replicate the outward seepage of dentinal flu-id through the dentin tubules under positive pulpal pressure. The appli-cation of pulpal pressure statistically reduced the ability of PCNS to repro-duce detail. Of the impression mate-rials with the same chemical struc-ture, PC showed acceptable detail reproducing ability, while surfactant free VPS (PCNS) did not have such ability on the moisturized dentin sur-face. This agrees with the findings of Pratten and Craig4 and Panichuttra et al.5 For impression materials with a contact angle larger than 70 degrees, such as PCNS, viscosity was the decid-ing factor for water displacement.26 In the present study, hydrophobic, light body consistency VPS (PCNS) did not reproduce the moistened dentin sur-face. If the contact angle was less than 70 degrees, a negative correlation be-tween the water-displacing ability of the impression material and the con-tact angle was reported.26 IGL (with a contact angle value of 18 degrees at 60 seconds), PIC (with 0 degrees), and PC (with 63 degrees) reproduced the dentin detail successfully. Indeed, all impression materials except for PCNS demonstrated similar surface texture and Ra values. Previously, Takahashi and Finger10 reported that hydrophobic and hydrophilic impres-sion materials showed similar dentin surface reproduction ability, whereas in the current study hydrophobic VPS (PCNS) failed to reproduce the surface texture to the same extent as hydrophilic VPS (PC, PIC) and poly-ether (IGL) impression materials. The discrepancy between these findings is probably due to intrinsic moisture provided by the pulpal pressure simu-lation in this study.

It should be noted that this study focused on the reproduction of a flat tooth surface, whereas more com-

plex structures such as narrow and deep subgingival preparation finish lines19,21 and clinical conditions29 may influence the success of impression materials. In a recent study, where dif-ferent width sulci were reproduced, polyether (IGL) reproduced narrow (50 µm wide) sulci better than the VPS impression materials tested in this study. This was correlated with the low contact angle values of the polyether impression material (<40 degrees) rather than the contact angle values of the VPS impression materi-als used in the Finger et al19 study (65 degrees, 60 degrees).

The ability to reproduce the ge-ometry of the peak, the peak to valley height, and the subgingivally located preparation finish lines was not evalu-ated in the present study. German et al21 determined the reproducibility of grooves of different depths in moist gypsum casts and showed that the ability of materials to reproduce de-tail depends on wettability for smaller grooves and initial tan delta values for deep grooves.21 The tan delta value gives an indication of the energy loss in the material during deformation and is important in the evaluation of the viscoelastic properties of elas-tomeric impression materials during polymerization. Higher values of tan delta indicate higher energy loss and more viscous behavior.40 PCNS repli-cas yielded higher surface roughness values than the original dentin surface and showed different surface texture (Fig. 9A, 9B), results which are prob-ably related to the materials’ low wet-tability, causing water to be trapped at the surface.21 In a previous study, none of the hydrophilic VPS impres-sion materials reproduced the surface detail in wet conditions.13 Walker et al12 determined that only PE impres-sion material showed satisfactory de-tail reproduction in moist conditions. In these studies, the contact angle val-ues of the impression materials were not considered.11,13 However Mondon and Ziegler7 showed that one of the VPS materials, which was indicated as hydrophilic in previously mentioned



111August 2012


8 Panasil Contact Plus (PC). A, 3-D oblique surface plot (interferogram) of impression surface from pulpal pressure simulated dentin. Specimen best representing mean condition chosen for 3-D oblique surface plots. B, SEM images of impression surface from pulpal pressure simulated dentin (×100).

A

B

9 Panasil Contact Plus Non-Surfactant (PCNS). A, 3-D oblique surface plot (interferogram) of impression surface from pulpal pressure simulated dentin. Specimen best repre-senting mean condition chosen for 3-D oblique surface plots. B, SEM images of impression surface from pulpal pressure simulated dentin (×100).

10 Three-dimensional oblique surface plot (interferogram) of resin surface. A, Impregum Garant L DuoSoft. B, Panasil Initial Contact. C, Panasil Contact. D, Panasil Contact Plus Non-Surfactant.

A

B

ously replicate 1 of the 0.02-mm wide horizontal lines in 2 of 3 specimens prepared from a calibrated metal die model,11 but, because of the struc-tural difference between metal and dentin, its clinical significance is not clear.2,18,21 Nonetheless, using dentin as the reference surface brings with it standardization problems. In most of the studies, the dentin surface was prepared by grinding the teeth with wet SiC paper,18,26 whereas in a clini-cal situation, teeth are prepared with different cutting instruments, such as diamond, tungsten carbide, and tungsten carbide finishing burs. In the present study, a tungsten carbide finishing bur was used because of its contributions to marginal fit.39

Instead of the ANSI/ADA detail reproduction test, the combined use of SEM and profilometry has been popular for analyzing the detail re-production ability of impression and cast materials.10,20,23,32 Although the 2-D SEM technique does not provide roughness parameters or quantitative roughness values directly, it can be used in surface roughness analysis.32 In the present study, the 2-D SEM image of PCNS impression material from a moisturized dentin surface is clearly indicative of fidelity loss. The recognized disadvantages of con-tact profilometry are the distortion or abrasion of the specimen surface and the resolution of the instrument due to large tip size, which may com-promise the accuracy of measure-ments.23,32 However, from the data gathered from noncontact profiling techniques, it is possible to create a 3-D image of the surface in addition to the quantitative roughness val-ues.24 Rodriguez et al22 showed that the measurement of the noncontact laser profilometer is affected by the color and transparency of the materi-als. In the present study, a 3-D surface profilometer incorporating scanning white-light interferometry was used. Delong et al25 showed that color does not affect the digitizing performance of a white light digitizer.

It was clear that dentin wetness

is important during the impression procedure.12,13,20,21 To the authors’ knowledge, the inclusion of pulpal pressure simulation to evaluate detail reproduction has not been used in a previous study. In this study, dentin moisture was provided to replicate the outward seepage of dentinal flu-id through the dentin tubules under positive pulpal pressure. The appli-cation of pulpal pressure statistically reduced the ability of PCNS to repro-duce detail. Of the impression mate-rials with the same chemical struc-ture, PC showed acceptable detail reproducing ability, while surfactant free VPS (PCNS) did not have such ability on the moisturized dentin sur-face. This agrees with the findings of Pratten and Craig4 and Panichuttra et al.5 For impression materials with a contact angle larger than 70 degrees, such as PCNS, viscosity was the decid-ing factor for water displacement.26 In the present study, hydrophobic, light body consistency VPS (PCNS) did not reproduce the moistened dentin sur-face. If the contact angle was less than 70 degrees, a negative correlation be-tween the water-displacing ability of the impression material and the con-tact angle was reported.26 IGL (with a contact angle value of 18 degrees at 60 seconds), PIC (with 0 degrees), and PC (with 63 degrees) reproduced the dentin detail successfully. Indeed, all impression materials except for PCNS demonstrated similar surface texture and Ra values. Previously, Takahashi and Finger10 reported that hydrophobic and hydrophilic impres-sion materials showed similar dentin surface reproduction ability, whereas in the current study hydrophobic VPS (PCNS) failed to reproduce the surface texture to the same extent as hydrophilic VPS (PC, PIC) and poly-ether (IGL) impression materials. The discrepancy between these findings is probably due to intrinsic moisture provided by the pulpal pressure simu-lation in this study.

It should be noted that this study focused on the reproduction of a flat tooth surface, whereas more com-

plex structures such as narrow and deep subgingival preparation finish lines19,21 and clinical conditions29 may influence the success of impression materials. In a recent study, where dif-ferent width sulci were reproduced, polyether (IGL) reproduced narrow (50 µm wide) sulci better than the VPS impression materials tested in this study. This was correlated with the low contact angle values of the polyether impression material (<40 degrees) rather than the contact angle values of the VPS impression materi-als used in the Finger et al19 study (65 degrees, 60 degrees).

The ability to reproduce the ge-ometry of the peak, the peak to valley height, and the subgingivally located preparation finish lines was not evalu-ated in the present study. German et al21 determined the reproducibility of grooves of different depths in moist gypsum casts and showed that the ability of materials to reproduce de-tail depends on wettability for smaller grooves and initial tan delta values for deep grooves.21 The tan delta value gives an indication of the energy loss in the material during deformation and is important in the evaluation of the viscoelastic properties of elas-tomeric impression materials during polymerization. Higher values of tan delta indicate higher energy loss and more viscous behavior.40 PCNS repli-cas yielded higher surface roughness values than the original dentin surface and showed different surface texture (Fig. 9A, 9B), results which are prob-ably related to the materials’ low wet-tability, causing water to be trapped at the surface.21 In a previous study, none of the hydrophilic VPS impres-sion materials reproduced the surface detail in wet conditions.13 Walker et al12 determined that only PE impres-sion material showed satisfactory de-tail reproduction in moist conditions. In these studies, the contact angle val-ues of the impression materials were not considered.11,13 However Mondon and Ziegler7 showed that one of the VPS materials, which was indicated as hydrophilic in previously mentioned



113August 2012


studies, showed a 117 ±5 degree ini-tial contact angle value, creating a hydrophobic state after 50 seconds of mixing time. This may account for the failure of the VPS impression material in the previous studies.12,13

In addition to the evaluation of the ability of impression material to reproduce detail, this study also ex-amined the transference of those de-tails to casts made of Type IV dental stone and polyurethane resin. The selection of polyurethane resin was based on the results of a pilot. In this study, polyurethane resin-based die material (Alpha Die Top; Schütz Dental Group, Rosbach, Germany) transferred the surface texture of im-pression material better than Type IV dental stone. This agrees with the findings of previous studies in which Derrien and Le Menn32 and Duke et al33 showed that gypsum materials caused loss of fidelity in details small-er than 17 µm and 20 µm. In the pres-ent study, dental stone showed higher roughness values than dentin and im-pression materials, probably because of the large particle size or micropo-rosity of dental stone. This corrobo-rates the finding of a previous study.10 However, the same investigators were able to demonstrate that Type IV den-tal stone could reproduce the main details of surfaces prepared with SiC paper, grit 240, by using SEM imag-es.10 The results of the present study also showed that polyurethane resin was able to reproduce detail similar to that of impression materials.32 The Ra value of the resin surface (PCNS/PP) was statistically higher than that of dentin, whereas it was not different from the impression surface (PCNS/PP). This means that the difference between the Ra values of the den-tin surface and the resin surface was caused by PCNS impression materi-als. In the current study, PE, because of its inherent hydrophilicity, and VPS, because of the presence of surfactant (PIC, PC), were both able to repro-duce surface detail despite different contact angle values (18, 0, and 63 degrees). There are limitations to this

study since clinical conditions such as humidity level, temperature effect, and sulcular area were not consid-ered. The impression materials tested were not used with a tray, which may affect their clinical success.28 Further clinical investigations are needed to investigate the clinical performance of newly formulated elastomeric den-tal impression materials.

CONCLUSIONS

Within the limitations of this study, the following conclusions were drawn:

1. Polyether impression material and surfactant-containing VPS im-pression materials showed decreasing contact angle values over time, where-as surfactant free VPS impression ma-terial showed constant contact angle values during polymerization.

2. VPS impression materials modi-fied by the addition of surfactant were better able to reproduce detail than surfactant free VPS impression mate-rials under simulated pulpal pressure design (P<.013).

3. Under simulated pulpal pres-sure design, surfactant modified VPS and the polyether impression materi-als tested (P>.013) may reproduce similar detail of the prepared dentin surface.

4. Polyurethane resin cast mate-rial accurately reproduced the detail of the impression materials (P≥.006).

REFERENCES

1. O’Brien WJ. Dental materials and their selection. 4th ed. Illinois: Quintessence Publishing Co, Inc.; 2008. p. 103-4

2. Anusavice KJ. Phillips’ science of dental ma-terials. 11th ed. St. Louis: Elsevier Mosby; 2003. p. 214-6, 225

3. Chai JY, Yeung TC. Wettability of nonaque-ous elastomeric impression materials. Int J Prosthodont 1991;4:555-60.

4. Pratten DH, Craig RG. Wettability of a hydro-philic addition silicone impression material. J Prosthet Dent 1989; 61:197-202.

5. Panichuttra R, Jones RM, Goodacre C, Munoz CA, Moore BK. Hydrophilic poly(vinyl siloxane) impression materials: dimensional accuracy, wettability, and effect on gypsum hardness. Int J Prosthodont 1991;4:240-8.

6. Vassilakos N, Fernandes CP. Surface prop-erties of elastomeric impression materials. J Dent 1993;21:297-301.

7. Mondon M, Ziegler C. Changes in water contact angles during the first phase of setting of dental impression materials. Int J Prosthodont 2003;16:49-53.

8. Kugel G, Klettke T, Goldberg JA, Benchimol J, Perry RD, Sharma S. Investigation of a new approach to measuring contact angles for hydrophilic impression materials. J Prosthodont 2007;16:84-92.

9. Rupp F, Axmann D, Geis-Gerstorfer J. Effect of relative humidity on the hydrophilicity of unset elastomeric impression materials. Int J Prosthodont 2008;21:69-71.

10.Takahashi H, Finger WJ. Dentin surface reproduction with hydrophilic and hydro-phobic impression materials. Dent Mater 1991;7:197-201.

11.Revised American Dental Association specification no. 19 for non-aqueous, elas-tomeric dental impression materials. J Am Dent Assoc 1977;94:733-41.

12.Walker MP, Petrie CS, Haj-Ali R, Spencer P, Dumas C, Williams K. Moisture effect on polyether and polyvinylsiloxane dimen-sional accuracy and detail reproduction. J Prosthodont 2005;14:158-63.

13.Petrie CS, Walker MP, O’Mahony A M, Spencer P. Dimensional accuracy and sur-face detail reproduction of two hydrophilic vinyl polysiloxane impression materials tested under dry, moist, and wet condi-tions. J Prosthet Dent 2003;90:365-72.

14.Butta R, Tredwin CJ, Nesbit M, Moles DR. Type IV gypsum compatibility with five addition-reaction silicone impression mate-rials. J Prosthet Dent 2005;93:540-4.

15.Schelb E, Cavazos E, Jr., Troendle KB, Prihoda TJ. Surface detail reproduction of Type IV dental stones with selected polyvi-nyl siloxane impression materials. Quintes-sence Int 1991;22:51-5.

16.Fernandes CP, Vassilakos N. Accuracy, detail reproduction, hardness of gypsum casts produced from silicone impressions treated with glow discharge. J Prosthet Dent 1990:457-64.

17.Ragain JC, Grosko ML, Raj M, Ryan TN, Johnston WM. Detail reproduction, con-tact angles, and die hardness of elastomeric impression and gypsum die material combi-nations. Int J Prosthodont 2000;13:214-20.

18.Kanehira M, Finger WJ, Komatsu M. Surface detail reproduction with new elastomeric dental impression materials. Quintessence Int 2007;38:479-88.

19.Finger WJ, Kurokawa R, Takahashi H, Kom-atsu M. Sulcus reproduction with elastomeric impression materials: a new in vitro testing method. Dent Mater 2008;24:1655-60.

20.Johnson GH, Lepe X, Aw TC. The effect of surface moisture on detail reproduction of elastomeric impressions. J Prosthet Dent 2003;90:354-64.

21.German MJ, Carrick TE, McCabe JF. Surface detail reproduction of elastomeric impression materials related to rheological properties. Dent Mater 2008;24:951-6.

22.Rodriguez JM, Curtis RV, Bartlett DW. Surface roughness of impression materi-als and dental stones scanned by non-contacting laser profilometry. Dent Mater 2009;25:500-5.

23.Verran J RD, Boyd RD, Visualization and measurement of nanometer dimension surface features using dental impression materials and atomic force microscopy. Int Biodetorior Biodegradation 2003;51:221-8.

24.Cehreli ZC, Lakshmipathy M, Yazici R. Ef-fect of different splint removal techniques on the surface roughness of human enamel: a three-dimensional optical profilometry analysis. Dent Traumatol 2008;24:177-82.

25.DeLong R, Pintado MR, Ko CC, Hodges JS, Douglas WH. Factors influencing optical 3D scanning of vinyl polysiloxane impression materials. J Prosthodont 2001; 10:78-85.

26.Peutzfeldt A, Asmussen E. Impression ma-terials: effect of hydrophilicity and viscosity on ability to displace water from dentin surfaces. Scand J Dent Res 1988;96:253-9.

27.Stober T, Johnson GH, Schmitter M. Ac-curacy of the newly formulated vinyl silox-anether elastomeric impression material. J Prosthet Dent 2010;103:228-39.

28.Johnson GH, Mancl LA, Schwedhelm ER, Verhoef DR, Lepe X. Clinical trial investigat-ing success rates for polyether and vinyl polysiloxane impressions made with full-arch and dual-arch plastic trays. J Prosthet Dent 2010;103:13-22.

29.Raigrodski AJ, Dogan S, Mancl LA, Heindl H. A clinical comparison of two vinyl polysiloxane impression materials using the one-step technique. J Prosthet Dent 2009;102:179-86.

30.Brannstrom M, Linden LA, Johnson G. Movement of dentinal and pulpal fluid caused by clinical procedures. J Dent Res 1968;47:679-82.

31.Powers JM, Sakaguchi RL. Craig`s restor-ative materials. 12 ed. St Louis: Mosby; 2006. p. 270-312

32.Derrien G, Le Menn G. Evaluation of detail reproduction for three die materials by using scanning electron microscopy and two-dimensional profilometry. J Prosthet Dent 1995;74:1-7.

33.Duke P, Moore BK, Haug SP, Andres CJ. Study of the physical properties of type IV gypsum, resin-containing, and epoxy die materials. J Prosthet Dent 2000;83:466-73.

34.Kenyon BJ, Hagge MS, Leknius C, Daniels WC, Weed ST. Dimensional accuracy of 7 die materials. J Prosthodont 2005;14:25-31.

35.Derrien G, Sturtz G. Comparison of trans-verse strength and dimensional variations between die stone, die epoxy resin, and die polyurethane resin. J Prosthet Dent 1995;74:569-74.

36.Lorren RA, Salter DJ, Fairhurst CW. The contact angles of die stone on impression materials. J Prosthet Dent 1976;36:176-80.

37.Cullen DR, Mikesell JW, Sandrik JL. Wet-tability of elastomeric impression materials and voids in gypsum casts. J Prosthet Dent 1991;66:261-5.

38.Sauro S, Pashley DH, Montanari M, Cher-soni S, Carvalho RM, Toledano M, et al. Ef-fect of simulated pulpal pressure on dentin permeability and adhesion of self-etch ad-hesives. Dent Mater 2007;23:705-13. www.ncss.com39. Ayad MF. Effects of tooth preparation burs and luting cement types on the marginal fit of extracoronal restora-tions. J Prosthodont 2009;18:145-51.

40.McCabe JF, Carrick TE. Rheological proper-ties of elastomers during setting. J Dent Res 1989;68:1218-22.

Corresponding author:Dr Ozlem AcarBaskent Unıversıty Faculty of Dentıstry11. Sokak No.27 BahcelıevlerAnkaraTURKEYFax: +90-312-2152962E-mail: [email protected]

AcknowledgmentsThe authors thank Dr. Bulent Dayangac forvaluable help and encouragement for this study, the Zygo Corporation for use of the 3-D optical profiler systems, and Metin Yasin (Kettenbach GmbH & Co. KG) for providing test material without surfactant used in this study.

Copyright © 2012 by the Editorial Council for The Journal of Prosthetic Dentistry.



113August 2012


studies, showed a 117 ±5 degree ini-tial contact angle value, creating a hydrophobic state after 50 seconds of mixing time. This may account for the failure of the VPS impression material in the previous studies.12,13

In addition to the evaluation of the ability of impression material to reproduce detail, this study also ex-amined the transference of those de-tails to casts made of Type IV dental stone and polyurethane resin. The selection of polyurethane resin was based on the results of a pilot. In this study, polyurethane resin-based die material (Alpha Die Top; Schütz Dental Group, Rosbach, Germany) transferred the surface texture of im-pression material better than Type IV dental stone. This agrees with the findings of previous studies in which Derrien and Le Menn32 and Duke et al33 showed that gypsum materials caused loss of fidelity in details small-er than 17 µm and 20 µm. In the pres-ent study, dental stone showed higher roughness values than dentin and im-pression materials, probably because of the large particle size or micropo-rosity of dental stone. This corrobo-rates the finding of a previous study.10 However, the same investigators were able to demonstrate that Type IV den-tal stone could reproduce the main details of surfaces prepared with SiC paper, grit 240, by using SEM imag-es.10 The results of the present study also showed that polyurethane resin was able to reproduce detail similar to that of impression materials.32 The Ra value of the resin surface (PCNS/PP) was statistically higher than that of dentin, whereas it was not different from the impression surface (PCNS/PP). This means that the difference between the Ra values of the den-tin surface and the resin surface was caused by PCNS impression materi-als. In the current study, PE, because of its inherent hydrophilicity, and VPS, because of the presence of surfactant (PIC, PC), were both able to repro-duce surface detail despite different contact angle values (18, 0, and 63 degrees). There are limitations to this

study since clinical conditions such as humidity level, temperature effect, and sulcular area were not consid-ered. The impression materials tested were not used with a tray, which may affect their clinical success.28 Further clinical investigations are needed to investigate the clinical performance of newly formulated elastomeric den-tal impression materials.

CONCLUSIONS

Within the limitations of this study, the following conclusions were drawn:

1. Polyether impression material and surfactant-containing VPS im-pression materials showed decreasing contact angle values over time, where-as surfactant free VPS impression ma-terial showed constant contact angle values during polymerization.

2. VPS impression materials modi-fied by the addition of surfactant were better able to reproduce detail than surfactant free VPS impression mate-rials under simulated pulpal pressure design (P<.013).

3. Under simulated pulpal pres-sure design, surfactant modified VPS and the polyether impression materi-als tested (P>.013) may reproduce similar detail of the prepared dentin surface.

4. Polyurethane resin cast mate-rial accurately reproduced the detail of the impression materials (P≥.006).

REFERENCES

1. O’Brien WJ. Dental materials and their selection. 4th ed. Illinois: Quintessence Publishing Co, Inc.; 2008. p. 103-4

2. Anusavice KJ. Phillips’ science of dental ma-terials. 11th ed. St. Louis: Elsevier Mosby; 2003. p. 214-6, 225

3. Chai JY, Yeung TC. Wettability of nonaque-ous elastomeric impression materials. Int J Prosthodont 1991;4:555-60.

4. Pratten DH, Craig RG. Wettability of a hydro-philic addition silicone impression material. J Prosthet Dent 1989; 61:197-202.

5. Panichuttra R, Jones RM, Goodacre C, Munoz CA, Moore BK. Hydrophilic poly(vinyl siloxane) impression materials: dimensional accuracy, wettability, and effect on gypsum hardness. Int J Prosthodont 1991;4:240-8.

6. Vassilakos N, Fernandes CP. Surface prop-erties of elastomeric impression materials. J Dent 1993;21:297-301.

7. Mondon M, Ziegler C. Changes in water contact angles during the first phase of setting of dental impression materials. Int J Prosthodont 2003;16:49-53.

8. Kugel G, Klettke T, Goldberg JA, Benchimol J, Perry RD, Sharma S. Investigation of a new approach to measuring contact angles for hydrophilic impression materials. J Prosthodont 2007;16:84-92.

9. Rupp F, Axmann D, Geis-Gerstorfer J. Effect of relative humidity on the hydrophilicity of unset elastomeric impression materials. Int J Prosthodont 2008;21:69-71.

10.Takahashi H, Finger WJ. Dentin surface reproduction with hydrophilic and hydro-phobic impression materials. Dent Mater 1991;7:197-201.

11.Revised American Dental Association specification no. 19 for non-aqueous, elas-tomeric dental impression materials. J Am Dent Assoc 1977;94:733-41.

12.Walker MP, Petrie CS, Haj-Ali R, Spencer P, Dumas C, Williams K. Moisture effect on polyether and polyvinylsiloxane dimen-sional accuracy and detail reproduction. J Prosthodont 2005;14:158-63.

13.Petrie CS, Walker MP, O’Mahony A M, Spencer P. Dimensional accuracy and sur-face detail reproduction of two hydrophilic vinyl polysiloxane impression materials tested under dry, moist, and wet condi-tions. J Prosthet Dent 2003;90:365-72.

14.Butta R, Tredwin CJ, Nesbit M, Moles DR. Type IV gypsum compatibility with five addition-reaction silicone impression mate-rials. J Prosthet Dent 2005;93:540-4.

15.Schelb E, Cavazos E, Jr., Troendle KB, Prihoda TJ. Surface detail reproduction of Type IV dental stones with selected polyvi-nyl siloxane impression materials. Quintes-sence Int 1991;22:51-5.

16.Fernandes CP, Vassilakos N. Accuracy, detail reproduction, hardness of gypsum casts produced from silicone impressions treated with glow discharge. J Prosthet Dent 1990:457-64.

17.Ragain JC, Grosko ML, Raj M, Ryan TN, Johnston WM. Detail reproduction, con-tact angles, and die hardness of elastomeric impression and gypsum die material combi-nations. Int J Prosthodont 2000;13:214-20.

18.Kanehira M, Finger WJ, Komatsu M. Surface detail reproduction with new elastomeric dental impression materials. Quintessence Int 2007;38:479-88.

19.Finger WJ, Kurokawa R, Takahashi H, Kom-atsu M. Sulcus reproduction with elastomeric impression materials: a new in vitro testing method. Dent Mater 2008;24:1655-60.

20.Johnson GH, Lepe X, Aw TC. The effect of surface moisture on detail reproduction of elastomeric impressions. J Prosthet Dent 2003;90:354-64.

21.German MJ, Carrick TE, McCabe JF. Surface detail reproduction of elastomeric impression materials related to rheological properties. Dent Mater 2008;24:951-6.

22.Rodriguez JM, Curtis RV, Bartlett DW. Surface roughness of impression materi-als and dental stones scanned by non-contacting laser profilometry. Dent Mater 2009;25:500-5.

23.Verran J RD, Boyd RD, Visualization and measurement of nanometer dimension surface features using dental impression materials and atomic force microscopy. Int Biodetorior Biodegradation 2003;51:221-8.

24.Cehreli ZC, Lakshmipathy M, Yazici R. Ef-fect of different splint removal techniques on the surface roughness of human enamel: a three-dimensional optical profilometry analysis. Dent Traumatol 2008;24:177-82.

25.DeLong R, Pintado MR, Ko CC, Hodges JS, Douglas WH. Factors influencing optical 3D scanning of vinyl polysiloxane impression materials. J Prosthodont 2001; 10:78-85.

26.Peutzfeldt A, Asmussen E. Impression ma-terials: effect of hydrophilicity and viscosity on ability to displace water from dentin surfaces. Scand J Dent Res 1988;96:253-9.

27.Stober T, Johnson GH, Schmitter M. Ac-curacy of the newly formulated vinyl silox-anether elastomeric impression material. J Prosthet Dent 2010;103:228-39.

28.Johnson GH, Mancl LA, Schwedhelm ER, Verhoef DR, Lepe X. Clinical trial investigat-ing success rates for polyether and vinyl polysiloxane impressions made with full-arch and dual-arch plastic trays. J Prosthet Dent 2010;103:13-22.

29.Raigrodski AJ, Dogan S, Mancl LA, Heindl H. A clinical comparison of two vinyl polysiloxane impression materials using the one-step technique. J Prosthet Dent 2009;102:179-86.

30.Brannstrom M, Linden LA, Johnson G. Movement of dentinal and pulpal fluid caused by clinical procedures. J Dent Res 1968;47:679-82.

31.Powers JM, Sakaguchi RL. Craig`s restor-ative materials. 12 ed. St Louis: Mosby; 2006. p. 270-312

32.Derrien G, Le Menn G. Evaluation of detail reproduction for three die materials by using scanning electron microscopy and two-dimensional profilometry. J Prosthet Dent 1995;74:1-7.

33.Duke P, Moore BK, Haug SP, Andres CJ. Study of the physical properties of type IV gypsum, resin-containing, and epoxy die materials. J Prosthet Dent 2000;83:466-73.

34.Kenyon BJ, Hagge MS, Leknius C, Daniels WC, Weed ST. Dimensional accuracy of 7 die materials. J Prosthodont 2005;14:25-31.

35.Derrien G, Sturtz G. Comparison of trans-verse strength and dimensional variations between die stone, die epoxy resin, and die polyurethane resin. J Prosthet Dent 1995;74:569-74.

36.Lorren RA, Salter DJ, Fairhurst CW. The contact angles of die stone on impression materials. J Prosthet Dent 1976;36:176-80.

37.Cullen DR, Mikesell JW, Sandrik JL. Wet-tability of elastomeric impression materials and voids in gypsum casts. J Prosthet Dent 1991;66:261-5.

38.Sauro S, Pashley DH, Montanari M, Cher-soni S, Carvalho RM, Toledano M, et al. Ef-fect of simulated pulpal pressure on dentin permeability and adhesion of self-etch ad-hesives. Dent Mater 2007;23:705-13. www.ncss.com39. Ayad MF. Effects of tooth preparation burs and luting cement types on the marginal fit of extracoronal restora-tions. J Prosthodont 2009;18:145-51.

40.McCabe JF, Carrick TE. Rheological proper-ties of elastomers during setting. J Dent Res 1989;68:1218-22.

Corresponding author:Dr Ozlem AcarBaskent Unıversıty Faculty of Dentıstry11. Sokak No.27 BahcelıevlerAnkaraTURKEYFax: +90-312-2152962E-mail: [email protected]

AcknowledgmentsThe authors thank Dr. Bulent Dayangac forvaluable help and encouragement for this study, the Zygo Corporation for use of the 3-D optical profiler systems, and Metin Yasin (Kettenbach GmbH & Co. KG) for providing test material without surfactant used in this study.

Copyright © 2012 by the Editorial Council for The Journal of Prosthetic Dentistry.

1-s2.0-S0022391312601164-main o

Documents

scanning electron microscopy

pulpal pressure simulation

simulated pulpal pressure

contact angle values

elastomeric impression materials

simulate clinical conditions

vps impression materials

moisturized dentin surfaces