METALS AND MATERIALS International, Vol. 10, No. 6 (2004), pp. 549~553 Effects of Surface Coating on the Screw Loosening of Dental Abutment Screws Chan-Ik Park 1 , Han-Cheol Choe 2 * and Chae-Heon Chung 1 1 Department of Prosthodontics, College of Dentistry, Chosun University, Gwangju 501-759, Korea 2 Department of Dental Materials & Research Center of Nano-Interface Activation for Biomaterials, Chosun University Regardless of the type of performed restoration, in most cases, a screw connection is employed between the abutment and implant. For this reason, implant screw loosening has remained a problem in restorative practices. The purpose of this study was to compare the surface of coated/plated screws with titanium and gold alloy screws and to evaluate the physical properties of coated/plated material after scratch tests via FE-SEM (field emission scanning electron microscopy) investigation. GoldTite, titanium screws provided by 3i (Implant Inno- vation, USA) and TorqTite, titanium screws by Steri-Oss (Nobel Biocare, USA) and gold screws and titanium screws by AVANA (Osstem Implant, Korea) were selected for this study. The surface, crest, and root of the abutment screws were observed by FE-SEM. A micro-diamond needle was also prepared for the scratch test. Each abutment screw was fixed, and a scratch on the surface of the head region was made at constant load and thereafter the fine trace was observed with FE-SEM. The surface of GoldTite was smoother than that of other screws and it also had abundant ductility and malleability compared with titanium and gold screws. The scratch tests also revealed that teflon particles were exfoliated easily in the screw coated with teflon. The titanium screw had rough surface and low ductility. The clinical use of gold-plated screws is recommended as a means of preventing screw loosening. Keywords: screw loosening, screw surface treatment, coated screw, scratch test 1. INTRODUCTION In recent years, the use of osseointegrated implants has been popular in single-tooth restoration, and partially eden- tulous and fully edentulous restoration. Regardless of the type of performed restoration, in most cases, a screw con- nection is used between the abutment and implant. For this reason, implant screw loosening has remained a problem in restorative practices [1,2]. Abutment screw loosening was reported in a large number of studies and ranges from 2 to 45 % of the abutment [3-6]. One suggested reason for the high incidence of screwl oos- ening from early studies was that the abutment screw was made of titanium, and devices capable of providing counter torque during tightening were not available. These problems appeared to be solved through the use of a gold alloy abut- ment screw that yields a higher screw preload when properly torqued [2]. Current gold screws vary between manufactur- ers, ranging in gold content from 64.1 to 2 %, with a yield strength of 1,270 to 1,380 N [7]. In an effort to further reduce frictional resistance, dry lubricant coating has been applied to the abutment screw. The most notable screws in this regard are GoldTite (Implant Innovation, 3i) and TorqTite (Nobel Biocare, Steri-oss) [8]. GoldTite is a standard gold-alloy screw with a plating of 0.76 thickness of pure gold. With a tightening torque of 32 Ncm, the manufacturer reported a 24 % increased preload for the gold-plated screw [9]. TorqTite is a Teflon-coated titanium alloy screw, with a reported reduction of the fric- tional coefficient of 60 % [6,10]. Will et al. noted that GoldTite and TorqTite abutment screws with enhanced surfaces that help reduce the coeffi- cient of friction produced greater rotational angles and pre- load values than conventional gold alloy and titanium alloy screws [2]. Jeong et al. reported that in the case of GoldTite, the implant and screw had relatively close and tight contact without the presence of a large gap. In the case of TorqTite, the abutment screw and implant interface demonstrated incom- plete seating and only partial contact of threads between the implant and screw [5]. Rachel et al. noted that the mean val- ues for a combined anodizing abutment versus a non-anod- ized group in an ITI system were 27.9 and 33.9 Ncm, and *Corresponding author: [email protected]
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
METALS AND MATERIALS International, Vol. 10, No. 6 (2004), pp. 549~553
Effects of Surface Coating on the Screw Loosening of Dental Abutment Screws
Chan-Ik Park1, Han-Cheol Choe2* and Chae-Heon Chung1
1 Department of Prosthodontics, College of Dentistry, Chosun University, Gwangju501-759, Korea
2 Department of Dental Materials & Research Center of Nano-Interface Activation for Biomaterials, Chosun University
Regardless of the type of performed restoration, in most cases, a screw connection is employed between theabutment and implant. For this reason, implant screw loosening has remained a problem in restorative practices.The purpose of this study was to compare the surface of coated/plated screws with titanium and gold alloyscrews and to evaluate the physical properties of coated/plated material after scratch tests via FE-SEM (fieldemission scanning electron microscopy) investigation. GoldTite, titanium screws provided by 3i (Implant Inno-vation, USA) and TorqTite, titanium screws by Steri-Oss (Nobel Biocare, USA) and gold screws and titaniumscrews by AVANA (Osstem Implant, Korea) were selected for this study. The surface, crest, and root of theabutment screws were observed by FE-SEM. A micro-diamond needle was also prepared for the scratch test.Each abutment screw was fixed, and a scratch on the surface of the head region was made at constant loadand thereafter the fine trace was observed with FE-SEM. The surface of GoldTite was smoother than thatof other screws and it also had abundant ductility and malleability compared with titanium and gold screws.The scratch tests also revealed that teflon particles were exfoliated easily in the screw coated with teflon.The titanium screw had rough surface and low ductility. The clinical use of gold-plated screws is recommendedas a means of preventing screw loosening.
Keywords: screw loosening, screw surface treatment, coated screw, scratch test
1. INTRODUCTION
In recent years, the use of osseointegrated implants hasbeen popular in single-tooth restoration, and partially eden-tulous and fully edentulous restoration. Regardless of thetype of performed restoration, in most cases, a screw con-nection is used between the abutment and implant. For thisreason, implant screw loosening has remained a problem inrestorative practices [1,2].
Abutment screw loosening was reported in a large numberof studies and ranges from 2 to 45 % of the abutment [3-6].One suggested reason for the high incidence of screwl oos-ening from early studies was that the abutment screw wasmade of titanium, and devices capable of providing countertorque during tightening were not available. These problemsappeared to be solved through the use of a gold alloy abut-ment screw that yields a higher screw preload when properlytorqued [2]. Current gold screws vary between manufactur-ers, ranging in gold content from 64.1 to 2 %, with a yieldstrength of 1,270 to 1,380 N [7].
In an effort to further reduce frictional resistance, drylubricant coating has been applied to the abutment screw.The most notable screws in this regard are GoldTite (ImplantInnovation, 3i) and TorqTite (Nobel Biocare, Steri-oss) [8].
GoldTite is a standard gold-alloy screw with a plating of0.76 thickness of pure gold. With a tightening torque of32 Ncm, the manufacturer reported a 24 % increased preloadfor the gold-plated screw [9]. TorqTite is a Teflon-coatedtitanium alloy screw, with a reported reduction of the fric-tional coefficient of 60 % [6,10].
Will et al. noted that GoldTite and TorqTite abutmentscrews with enhanced surfaces that help reduce the coeffi-cient of friction produced greater rotational angles and pre-load values than conventional gold alloy and titanium alloyscrews [2]. Jeong et al. reported that in the case of GoldTite,the implant and screw had relatively close and tight contactwithout the presence of a large gap. In the case of TorqTite, theabutment screw and implant interface demonstrated incom-plete seating and only partial contact of threads between theimplant and screw [5]. Rachel et al. noted that the mean val-ues for a combined anodizing abutment versus a non-anod-ized group in an ITI system were 27.9 and 33.9 Ncm, and*Corresponding author: [email protected]
��� Chan-Ik Park et al.
anodization of the abutment surface reduced the resistance toloosening by approximately 20 % [11].
These studies demonstrated that surface treatments (coat-ing, plating, anodizing) play a role in preventing the screwfrom loosening in the implant screw mechanism.
The purpose of the present study is to compare the surfaceof coated/plated screws with titanium and gold alloy screwsand to evaluate the physical properties of coated/plated mate-rial after scratch tests.
2. EXPERIMENTAL PROCEDURE
2.1. MaterialsThe abutment screws selected for this study are as follows:
GoldTite and titanium screw (Implant Innovation) providedby 3i Co, USA, TorqTite and titanium screw (Nobel Bio-care) by Steri-Oss Co, USA, gold screw and titanium screw(Osstem Implant) by AVANA Co, Korea. Fig. 1 and Table 1show the type of screws and the manufacturer of screws usedin this study.
2.2. Methods2.2.1. FE-SEM investigation of surface of new abutment screw
The new screws were provided by their respective manu-facturers. A tungsten tip was used where micromanipulationof the specimens was carried out by using FE-SEM (Nether-land, Phillips Co, model: XL 30 SFEG). Care was taken notto contact the thread surface of abutment screw so as toavoid contamination of the surface. Each abutment screwsurface was observed at ×100 magnification; the screw crest,root, and slope were subsequently observed at ×1000 magni-fication.
2.2.2. FE-SEM investigation of scratched abutment screw surface A micro-diamond needle was prepared for the scratch test.
When each abutment screw was fixed, a scratch was madeon the surface of the head region at constant load and thenthe fine trace was observed with FE-SEM.
3. RESULTS
3.1. FE-SEM investigation of surface of new abutment screw Observing the surface of new abutment screws with FE-
SEM at ×100 magnification, we determined that all screwsvaried with respect to external form and the amount of sur-face roughness and foreign-material. GoldTite had a verysmooth surface (Fig. 2) and TorqTite had a rough surface duelargely to the coated material on the surface (Fig. 4). There
Fig. 1. Type of screws: (a) GoldTite of 3i, (b) titanium screw of 3i, (c)TorqTite of Steri-Oss, (d) titanium screw of Steri-Oss, (e) gold screwof AVANA, and (f) titanium screw of AVANA.
Table 1. Manufacturers and type of screws used in this study
Implant manufacturer Type of screw Type of alloy Implant innovation
(3i Co)Gold titetitanium
Gold-plated gold-palla-dium titanium
Nobel biocare(Steri-Oss Co)
Torq titeTitanium
Teflon-coated titaniumTitanium
Osstem implant(AVANA Co)
Goldtitanium
Goldtitanium
Fig. 2. FE-SEM micrographs of GoldTite screw surface of 3i, ImplantInnovation: (a) magnification ×100, (b) screw crest ×1000, and (c)screw root ×1000.
Fig. 3. FE-SEM micrographs of titanium alloy screw surface of 3i,Implant Innovation: (a) magnification ×100, (b) screw crest ×1000,and (c) screw root ×1000.
Fig. 4. FE-SEM micrographs of TorqTite screw surface of Steri-Oss,Nobel Biocare: (a) magnification ×100, (b) screw crest ×1000, and (c)screw root ×1000.
Fig. 5. FE-SEM micrographs of titanium alloy screw surface of Steri-Oss, Nobel Biocare: (a) magnification ×100, (b) screw crest ×1000,and (c) screw root ×1000.
Related Documents
