1-s2.0-S0022391314003369-main

Effe

stre

a he

Catherine M. Go

aAssistant Professor, Division of ResbGraduate student, Department of RcGraduate student, School of MechadSenior Lecturer, School of Mechani

The Journal of Prosthetic

cts of repeated processing on the

ngth and microstructure of

at-pressed dental ceramic

rman, MSc,a Kate Horgan, BDentSc,b

Ruth P. Dollard, BSc, MSc,c andKenneth T. Stanton, BSc, MSc, PhD, CEngd

Dublin Dental University School and Hospital, Dublin, Ireland; Uni-versity Dental School and Hospital, University College Cork, Wilton,Cork, Ireland; University College Dublin, Dublin, Ireland

Statement of problem. The excess material produced after heat pressing a lithium disilicate glass ceramic restoration canbe either discarded or reused. The reuse of this material requires that any degradation of the material quality beinvestigated.

Purpose. The purpose of this study was to investigate the number of times that leftover lithium disilicate material can bere-pressed and to determine the effect that repeated use has on material properties.

Material and methods. A large (6.1 g) lithium disilicate ingot (A3.5) was heat pressed to yield a ceramic disk (15�1.5 mm)for testing. The leftover material was reused to produce a further 3 disks, with the number of pressings increasing for eachspecimen. An additional unpressed group was included to investigate the properties before pressing so that, in total, 5 groupswere established. Specimens were tested for biaxial flexural strength, Vickers hardness, and fracture toughness. X-raydiffraction was used to characterize the crystalline phase, scanning electron microscopy for the microstructure, anddifferential scanning calorimetry for the thermal properties.

Results. No significant difference was found in the biaxial flexural strength of the groups. The hardness of the materialdecreased, and no significant difference was seen in fracture toughness with repeated pressings. An increase in grain size wasobserved with increased pressings. By using x-ray diffraction analysis, lithium disilicate was identified as the main crystalphase, and no difference in crystalline composition was found with repeated processing.

Conclusion. This material can be reused while maintaining good mechanical properties and without significantly alteringthe chemical or crystalline composition in an adverse manner. (J Prosthet Dent 2014;112:1370-1376)

Clinical Implications

This study showed that heat-pressed lithium disilicate can be reused up to 4times. Routine mechanical strength tests revealed no adverse consequencesfor lithium disilicate when it is reused and that dental laboratories may beroutinely and unnecessarily discarding excess material.

Heat pressing of glass ceramic ma-terials for dental applications is aproven method of fabricating fixedprosthodontic restorations.1-20 Theserestorations are translucent because ofthe absence of a metal substructure

torative Destorativenical andcal and M

Dentis

and thus offer an excellent opportunityfor achieving life-like esthetic restora-tions. IPS Empress was the originalheat-pressed glass ceramic and leucite(SiO2, Al2O3, 4K2O) is the main crys-talline phase in this system.4,5 IPS

entistry and Periodontology, Dublin Dental UnDentistry, University Dental School and HospiMaterials Engineering, University College Dublaterials Engineering, University College Dublin.

try

Empress 2 has lithium disilicate(Li2O$2SiO2) as its main crystallinephase and is 60% crystalline whenprocessed (Ivoclar Vivadent, IPSEmpress 2 Scientific Documentation,1998). It offers higher strength, which

iversity School and Hospital.tal, University College Cork.in.

Gorman et al

December 2014 1371

extends its recommended use to shortspan partial fixed dental prostheses. IPSe.max Press material has now replacedIPS Empress 2; it has improved me-chanical properties and has signifi-cantly higher translucency (IvoclarVivadent, IPS e.max Press ScientificDocumentation, 2011). The micro-structure consists of 70% lithium dis-ilicate crystals embedded in a glassymatrix. These crystals are acicular inmorphology and measure 3 to 6 mm inlength. Recommendations for its clin-ical use remain unchanged. IPS e.maxPress is available in 4 different levels ofopacity and/or translucency, the selec-tion of which is determined by the re-quirements of the individual clinicaltreatment. It is supplied for heatpressing in 2 sizes, a small ingot thatweighs 3.2 g or a larger ingot thatweighs 6.1 g. It is more economical topress several restorations from 1 ingotat the same time. However, this often isnot possible and may result in aconsiderable amount of leftover mate-rial. The issue is thereby raised whetherthe leftover material should be dis-carded or reused. Concerns as to themechanical properties of the reusedmaterial for clinical use are valid.

Extensive research into the mechan-ical properties and clinical performanceof heat-pressed glass ceramics has beencarried out over the past 2 decades.1-20

In spite of this, only 2 studies thatexamined the mechanical and micro-structural properties of re-pressed ce-ramics were identified by the presentauthors.19,20 In the first of thesestudies, the re-pressing of both IPSEmpress and IPS Empress 2 was evalu-ated.19 The biaxial flexural strength(BFS) of the pressed and re-pressedmaterials was unchanged, although ahigher scatter of the data was reportedfor the re-pressed material. Weibullanalysis of the data indicated that therewas less reliability when the materialwas re-pressed. X-ray diffraction (XRD)revealed no differences in crystallinephase assemblage or x-ray reflectionintensities with re-pressing. Scanningelectron microscopy (SEM) revealedlarger crystals for the re-pressed IPS

Gorman et al

Empress 2; this was attributed to Ost-wald ripening, whereby larger crystalsgrow at the expense of smaller ones.The conclusion was that re-pressing thematerial did not result in lower me-chanical properties; however, thegreater scatter may predict a reductionin reliability for the materials. In thesecond study, a significant difference inBFS was observed for re-pressed IPSEmpress 2.20 These studies showpromising results and give good insightinto re-pressed materials. However,studies have only tested a single reuseof the material, whereas, in practice, itcould be reused several times, depend-ing on the amount of material left over.The null hypothesis of the present studyis that IPS e.max Press can be reusedwithout adversely affecting its mechan-ical properties.

MATERIAL AND METHODS

The aim of the current study was toinvestigate the reuse of IPS e.max Press.This was carried out by using themaximum amount of pressings obtain-able from the largest commerciallyavailable ingot while preparing speci-mens suitable for biaxial flexuraltesting. Information regarding the flex-ural strength, hardness, and indenta-tion fracture toughness was evaluated.The composition and microstructure ofthe reused material also was studied toevaluate changes that may haveoccurred. One lithium disilicate ingot(IPS e.max Press; Ivoclar Vivadent AG)was selected for testing before pressing(group 0). Ten ingots (6.1 g each) werethen pressed to give 10 disks (15�1.5mm) for testing BFS (group 1). Theleftover material was recovered forreuse to produce a further 3 disks(groups 2, 3, and 4; the number cor-responds to the number of pressings).Thus, each ingot was pressed 4 times,and 4 groups were established forbiaxial testing (n¼10), Vickers hardness(n¼5), and fracture toughness (n¼5).By using the Mead resource equation,21

a minimum sample size of 5 wasdeemed adequate for the statisticalvalidity of all tests.

The specimens were ground flat onboth sides by using 180-grit siliconcarbide (SiC) paper (Buehler-Met) andwere measured with a digital caliper(Milomex Ltd) for parallelism to �0.05mm, and the thickness (h) of eachspecimen was recorded. A standard testmethod was used for testing the BFS ofthe disks.22 The disk was placed on thesupport ring of the testing device, andclear adhesive tape was placed on thecompressive surface before the loadingring was applied. A thin piece ofnonrigid material (polyethylene film)was placed between the loading ringand the disk. A force was applied to thedevice with a tensometer (Tinius OlsenH10KS; Tinius Olsen Ltd) at a rate of0.75 mm/min in compressive modeuntil the material failed. A 10-kN loadcell was used with a load range of 50%.The load at failure was recorded foreach disk, and the fragments werecollected for further analysis. Tenspecimens were tested for each group.The BFS was calculated for each spec-imen by using the following equation.22

sf ¼ 3F2ph2

�ð1� vÞD

2S � D2

L

2D2

þ ð1þ vÞlnDS

DL

�;

where sf is the maximum tensile stress(MPa), F is the total load causingfracture (N), h is the specimen thicknessat fracture origin (mm), v is the Poissonratio (taken here to be 0.23), DL is theradius of the load ring (3 mm), DS is theradius of the support ring (6 mm),and D is the radius of the specimen(7.5 mm).

Fragments of broken disks fromflexural testing were retrieved andfurther prepared for Vickers hardnessand indentation fracture toughnesstesting. Specimens were cold mountedin an acrylic resin and serially wetground with 300, 600, 1200, and 4000-grade SiC paper. The specimens werefinally polished with 1-mm diamondpaste. A Vickers diamond indenter(Mitutoyo AVK e C2 Hardness Tester;Mitutoyo America Corp) was used tocreate an indent under a load of 49 N.

Table I. Summary of mechanical properties for groups 0-4

n Group 0 Group 1 Group 2 Group 3 Group 4 P

BFS, MPa 10 n/a 243.4 �45.9 252.7 �23.7 225.06 �35.3 214.8 �45.9 .137

Hardness, Hv/5 5 585.2 �6.42 548.8 �28.68 559.4 �8.68 526.4 �49.13 547.6 �13.39 .99

KIc, MPa.m0.5a 5 0.29 �0 1.13 �0.02 1.01 �0.13 1.05 �0.04 1.09 �0.05 <.001

n/a, not available; BFS, biaxial flexural strength; Hv, Vickers hardness; KIc, fracture toughness.aIf group 0 is omitted, then there was no statistically significant variation in fracture toughness (P>.05).

50

1 2 3 4

100

150

200

250

300

0

Bia

xial

Fle

xura

lSt

reng

th (

MP

a)

Press Number

1 Biaxial flexural strength for IPS e.max Press groups 0-4with 95% confidence intervals.

1372 Volume 112 Issue 6

The 2 indentation diagonals d1 and d2created in the material were measuredwith the microscope on the hardnesstester, and a mean was calculated.23

The Vickers hardness value was deter-mined according to the following:

Hv ¼2Fsin 136e

2

d2z1:854

Fd2

;

where Hv is the Vickers hardness inkgf.mm�2, F the load applied in kg, andd the arithmetic mean of the 2 di-agonals, d1 and d2 in mm.

The length of radial cracks pro-duced as a result of indents made in thematerial were measured, and theindentation fracture toughness (KIc)was calculated by using the followingequation24:

KIc ¼ jb

P

c32o

!;

where Jb ¼1/ (p3/2 tan J) and J isthe half angle of the Vickers indenter(68 degrees), P is the indentation loadin MN, and co is the radial crack lengthin meters.

XRD was carried out for each of thespecimen groups. Specimens wereplaced in the holder of a diffractometer(Diffraktometer D500; Siemens) andscanned with Cu Ka x-rays between 10and70degrees 2qwith a step size of 0.02degrees and a 2-second step interval.JCPDS card no. 40-0376 was used toidentify the lithium disilicate phase.

In preparation for SEM, specimenswere cleaned, etched with 2% hydro-fluoric acid for 90 seconds, and thendropped immediately into a water bathfor 15 seconds. Specimens were furthercleaned with isopropyl alcohol andacetone. Finally, the specimens were

The Journal of Prosthetic Dentis

dried and sputter coated with gold.SEM (Quanta 3D FEG DualBeam) wasused to examine the surface topographyof the specimens; it also served as ameans of assessing a change in thegrain width or length within the speci-mens after re-pressing. Grains werearbitrarily selected (n¼10) from 1micrograph for each pressing, and thewidth and length of each selected grainwas recorded.25 Optical microscopy(Leica DFC320) also was performed toassess indentations on the specimens.

Differential scanning calorimetry(Stanton-Redcroft STA 1500; Rheo-metric Scientific) was carried out foreach group in a flowing nitrogen at-mosphere; the specimens were placedin matched platinum-rhodium cruciblesand heated to 1200�C at 10�C/minand cooled at 10�C/min until a tem-perature of 25�C was reached. Whereapplicable, the results were statisticallyanalyzed with 1-way ANOVA (a¼.05).

RESULTS

The results of mechanical testingare presented in Table I. No BFS

try

measurements were available for group0 because specimens could not be madeto the required specifications for testingwithout processing. BFS appears todecrease slightly with an increasednumber of pressings (Fig. 1). However,this decrease was not found to be sig-nificant (P¼.137). Quite a large scatterin the data was found for group 1(144.29-309.74 MPa) and for group 4(114.41-260.79 MPa). The fracturetoughness data for each group are pre-sented in Figure 2. The KIc of group 0wassignificantly lower than the other groups,with ameasured value of 0.29MPa.m0.5,although the material was not engi-neered to be used in this condition. Thefracture toughness determined for allother groups was between 1.13 and 1.01MPa.m0.5 with no statistically significantvariation. For group 0, the scatter in thedata was found to be remarkably lowcompared with the pressed groups.Hardness values were found to be in therange of 550 to600Hv/5 (Fig. 3) anddidnot change significantly with the numberof pressings.

With XRD, lithium disilicate wasidentified to be the main crystalline

Gorman et al

700

600

500

400

300

200

1000

1 2 3 4 5

Har

dne

ss (

Hv/

5)

Group Number

3 Hardness for IPS e.max Press groups 0-4 with 95%confidence intervals.

0.2

Press 1 Press 2 Press 3 Press 4

0.4

0.8

0.6

1

1.2

1.4

0

Frac

ture

Tou

ghne

ss(M

Pa.

m0.

5 )

Press Number

2 Fracture toughness for IPS e.max Press groups 1-4with 95% confidence intervals.

10 20 30 40 50 60 70

Inte

nsit

y (a

rb.)

Degrees 2θ4 X-ray diffraction data for groups 0-4 exhibiting peaks at2q values of 24.19 degrees, 24.74 degrees and 46.54 de-grees. Note difference between group 0 and that of othergroups.

December 2014 1373

phase. The dominant peaks present forgroups 1 to 4 are shown in Figure 4.The major peaks for lithium disilicate(Li2Si2O5) were observed at 2q values of24.74 degrees, 24.19 degrees, and46.54 degrees. The dominant peak wasat 24.74 degrees, which corresponds tothe (040) crystallographic plane of thismonoclinic phase. The XRD data

Gorman et al

showed that, after repeated pressings,the crystalline phase assemblage didnot change. SEM images for all groupsare given in Figure 5. The complexity ofthe grain structure made it difficult toperform reliably accurate measure-ments of grain sizes or to otherwisequantify aspects of the microstructure.However, average grain sizes of 1.47

mm mean length and 0.19 mm meanwidth were apparent for group 0,whereas average grain sizes of 4.19 mmmean length and 0.69 mm mean widthwere apparent for group 4. Overall, asystematic grain growth was evidentwith an increased number of pressings(see Fig. 5A-E). Also evident in themicrostructure were secondary crystalsthat appeared to grow directly from theprimary crystals: a higher magnificationimage of an etched group 2 specimen ispresented in Figure 5F. The results ofDSC showed an endotherm thatoccurred at 960�C for all 5 groups (seeFig. 6 for a representative curve). Thisendotherm indicates melting of thematerial and no difference in the tracesfor any of the groups.

DISCUSSION

The null hypothesis that IPS e.maxPress can be reused without adverselyaffecting its mechanical properties wasaccepted. The results indicated the po-tential to re-press lithium disilicateglass ceramic several times and wasonly practically limited by the size of theingots. However, the handling charac-teristics of the material were observedto decline somewhat by the definitivepressing (group 4). This manifested it-self with the material becoming morebrittle; for example, care was requiredwhen cutting off sprues. To comparethe flexural strengths with those inthe literature, group 1 results wereconsidered because this corresponds tothe manufacturer’s recommendations.The mean � SD BFS for this group was243.4 �45.8 MPa, lower than thosevalues reported by the manufacturer orin other studies.13,14 The surface finish(180-grit SiC paper) may be responsiblefor this because flexural strength mea-surements have been shown to dependon the surface finish.26-28 In addition,residual stresses are normally present asa result of manufacturing processes,which can lead to the reporting ofartificial mechanical properties. Theannealing of specimens can relievethese residual stresses, which results inmore reliable mechanical data.28 The

5 Scanning electron microscopy images for IPS e.max Press. A, Group 0. B, Group 1. C, Group 2. D, Group 3. E, Group 4.Growth in grain size is evident from group 0 to group 4. F, Shows group 2 with increased magnification. Note increase insecondary crystals present. This is due to partial dissolution of crystals at 960�C.

1374 Volume 112 Issue 6

test method here (ASTM 1499-05) useda ring-on-ring testing device.22 This re-quires specimens to be parallel towithin 0.05 mm for the test to producevalid results. Accurate parallelism of theceramic disk was ensured in this studywith careful measurement of the heightat 3 intervals around the disk. A greaterspecimen number would permit acalculation of the probability of failure

The Journal of Prosthetic Dentis

(Weibull modulus), information thatcould be valuable in further deter-mining the clinical viability of reusingthis material several times over.

Flexural strength values were shownto decrease slightly with an increasednumber of pressings; however, the dif-ference was not found to be significant.The specimen number (n¼10) mayhave been too small to show

try

significance within the context of thenormal experimental variability thatwould be expected with this technique.The hardness of the material was notshown to vary significantly withincreased pressings (526.4-585.2 Hv/5,equivalent of 5162-5739 MPa). Frac-ture toughness was not found to varysignificantly with increased pressings,and the values obtained here were for

Gorman et al

–1.8500 600 700 800 900 1000

–1.7

–1.6

–1.5H

eat

Flo

w (

mw

/mg)

Temperature (degrees C)

–1.4

–1.3

–1.2

–1.1

6 Representative differential scanning calorimetry forIPS e.max Press group 3 showing dissolution at 960�C.

December 2014 1375

comparative purposes only. Because ofthe indentation method selected tomeasure this property, comparing theresults with absolute values determinedby other means in the literature isinadvisable.

XRD revealed that lithium disilicatewas present in all the groups, and nodifference existed among the patterns foreach group. Observations of the scan-ning electron micrographs indicated anincrease in crystal grain growth at theexpense of smaller crystals. This findingis in agreement with another study,which found that Ostwald ripeningoccurred when the material was reusedonce.19 The current study indicated thatgrain growth occurs and has anapproximately linear relationship withan increased number of pressings.

SEM revealed not only the expectedprimary lithium disilicate crystals (asconfirmed by XRD) but also secondarycrystals, which appeared in greaternumbers with an increased number ofpress cycles. In other systems, such sec-ondary crystals may be due to thenucleation of polymorphs of the primarycrystal type.29 In the present study, noadditional phases were seen withincreased pressings from XRD, whereasthe number of secondary crystals didappear to increase with the number ofpressings. Therefore, the secondarycrystals are likely to be due to recrystal-lization of the crystals after they eitherpartially melt or partially dissolve in theresidual glass phase during the processcycle. The DSC trace (Fig. 6) showedthat the melting endotherm begins at

Gorman et al

approximately 850�C, and, whenconsidering that the processing temper-ature during pressing is 920�C, the like-lihood that the secondary crystals are theoutcome of recrystallization is increased:indeed, the initial melting is almostcertainly necessary to enable pressing inthe first instance.

CONCLUSIONS

The optimum properties for IPSe.max Press are probably obtained withthe first pressing. However, no materialmechanical properties appear to varysignificantly with subsequent pressings.Although results of this study deter-mined that reusing the material ispossible, the authors did notice somequalitative differences in specimenhandling with increased reuse (up to 4times). As such, conclusive support isnot possible for its reuse to this extent.

REFERENCES

1. Cattell MJ, Clarke RL, Lynch E. The transversestrength, reliability and microstructural fea-tures of four dental ceramics: part 1. J Dent1997;25:399-407.

2. Gorman CM, McDevitt WE, Hill RG. Com-parison of two heat-pressed all-ceramicdental materials. Dent Mater 2000;16:389-95.

3. Cattell MJ, Knowles JC, Clarke RL, Lynch E.The biaxial flexural strength of two pressableceramic systems. J Dent 1999;27:183-96.

4. Dong JK, Luthy H, Wohlwend A, Scharer P.Heat-pressed ceramics: technology andstrength. Int J Prosthodontics 1992;5:9-16.

5. Probster L, Geis-Gerstorfer J, Kirchner E,Kanjantra P. In vitro evaluation of a glass-ceramic restorative material. J Oral Rehabil1997;24:636-45.

6. Höland W, Schweiger M, Frank M,Rheinberger V. A comparison of the micro-structure and properties of the IPS Empress 2and the IPS Empress glass-ceramics.J Biomed Mater Res 2000;53:297-303.

7. Kheradmandan S, Koutayas SO, Bernhard M,Strub JR. Fracture strength of four differenttypes of anterior 3-unit bridges after thermo-mechanical fatigue in the dual-axis chewingsimulator. J Oral Rehabil 2001;28:361-9.

8. Seghi RR, Denry IL, Rosenstiel SF. Relativefracture toughness and hardness of newdental ceramics. J Prosthet Dent 1995;74:145-50.

9. Sobrinho LC, Cattell MJ, Knowles JC. Frac-ture strength of all-ceramic crowns. J MaterSci Mater Med 1998;9:555-9.

10. Uctasli S, Wilson HJ, Unterbrink G,Zaimoglu A. The strength of a heat-pressedall-ceramic restorative material. J Oral Reha-bil 1996;23:257-61.

11. Wagner WC, Chu TM. Biaxial flexuralstrength and indentation fracture toughnessof three new dental core ceramics. J ProsthetDent 1996;76:140-4.

12. Albakry M, Guazzato M, Swain MV. Fracturetoughness and hardness evaluation of threepressable all-ceramic dental materials. J Dent2003;31:181-8.

13. Albakry M, Guazzato M, Swain MV. Biaxialflexural strength, elastic moduli, and x-raydiffraction characterization of three pressableall-ceramic materials. J Prosthet Dent2003;89:374-80.

14. Guazzato M, Albakry M, Ringer SP,Swain MV. Strength, fracture toughness andmicrostructure of a selection of all-ceramicmaterials. Part I. Pressable and aluminaglass-infiltrated ceramics. Dent Mater2004;20:441-8.

15. Stoll R, Cappel I, Jablonski-Momeni A,Pieper K, Stachniss V. Survival of inlays andpartial crowns made of IPS empress after a10-year observation period and in relation tovarious treatment parameters. Oper Dent2007;32:556-63.

16. Etman MK, Woolford MJ. Three-year clinicalevaluation of two ceramic crown systems: apreliminary study. J Prosthet Dent 2010;103:80-90.

17. Guess PC, Strub JR, Steinhart N,Wolkewitz M, Stappert CF. All-ceramic par-tial coverage restorations: midterm results ofa 5-year prospective clinical splitmouthstudy. J Dent 2009;37:627-37.

18. Gemalmaz D. Use of heat-pressed, leucite-reinforced ceramic on anterior and posterioronlays: a clinical report. J Prosthet Dent2002;87:133-5.

19. Albakry M, Guazzato M, Swain MV. Biaxialflexural strength and microstructure changesof two recycled pressable glass ceramics.J Prosthodont 2004;13:141-9.

20. Chung KH, Liao JH, Duh JG, Chan DC. Theeffects of repeated heat-pressing on proper-ties of pressable glass-ceramics. J OralRehabil 2009;36:132-41.

21. Mead R, Gilmour SG, Mead A. Statisticalprinciples for the design of experiments.Cambridge: Cambridge University Press;2012. p. 7-8.

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22. ASTM. C1499-05 Standard test method formonotonic equibiaxial flexural strength ofadvanced ceramic at ambient temperature.West Conshohocken, PA: ASTM; 2005.

23. ASTM. C1327-08 Standard test method forVickers indentation hardness of advancedceramics. West Conshohocken, PA: ASTMInternational; 2009.

24. ASTM. E1820-11 Standard test method formeasurement of fracture toughness. WestConshohocken, PA: ASTM International;2010.

25. Abramoff MD, Magelhaes PJ, Ram SJ. Imageprocessing with Imagej. Biophotonics Int2004;11:36-42.

Notewort

Peri-implantitis: A systematic rev

Pesce P, Menini M, Tealdo T, Bevi

Int J Prosthodont 2014;27:15-25.

Purpose. This systematic review considersrecent literature.

Materials and Methods. An electronic seatween January 2005 and September 2012

Results. The electronic and manual searchtitles and abstracts, 24 full texts were dowarticles (4 clinical studies and 6 animal stsufficient evidence to address the researchrelationship between peri-implantitis andunanimous regarding a specific peri-implawas cited as contributing to a higher inci

Conclusion. The available scientific literatuof peri-implantitis and its specific relationsits definition remain controversial.

Reprinted with permission of Quintessenc

The Journal of Prosthetic Dentis

26. Cattell MJ, Palumbo RP, Knowles JC,Clarke RL, Samarawickrama DY. The effect ofveneering and heat treatment on the flexuralstrength of Empress Ceramics. J Dent2002;30:161-9.

27. Chen HY, Hickel R, Setcos JC,Kunzelmann KH. Effects of surfacefinish and fatigue testing on thefracture strength of CAD-CAM andpressed-ceramic crowns. J Prosthet Dent1999;82:468-75.

28. Fischer H, Hemelik M, Telle R, Marx R. In-fluence of annealing temperature on thestrength of dental glass ceramic materials.Dent Mater 2005;21:671-7.

hy Abstracts of the Current Li

iew of recently published papers

lacqua M, Pera F, Pera P.

possible etiologic factors and definitions

rch of databases plus a hand search of thwere performed.

es yielded 640 and 14 titles, respectively. Frnloaded (18 clinical studies and 6 animaludies) were included in this review. Nonequestion, and no human clinical evidenc

bacterial accumulation and/or occlusal ovntitis etiology. However, a correlation betwdence of peri-implantitis.

re is characterized by an absence of a unanhip to periodontitis. Furthermore, both th

e Publishing.

try

29. Cashell C, Corcoran D, Hodnett BK. Effect ofamino acid additives on the crystallizationof L-Glutamic acid. Crys Growth Des 2005;5:593-7.

Corresponding author:Ms Catherine M. GormanDivision of Restorative Dentistry and PeriodontologyDublin Dental School and HospitalLincoln Place, Dublin 2IRELANDE-mail: [email protected]

Copyright ª 2014 by the Editorial Council forThe Journal of Prosthetic Dentistry.

terature

of peri-implantitis as reported in the

e most relevant journals published be-

om the independent doublecheck of thestudies). After reading the full texts, 10of the human articles selected providede is available to support a cause-effecterload. The animal literature is also noteen periodontitis and smoking histories

imous consensus regarding the etiologye choice of the term peri-implantitis and

Gorman et al