- Email: [email protected]
Effect of feldspathic porcelain layering on the marginal fit of zirconia and titanium complete-arch fixed implant-supported frameworks
RESEARCH AND EDUCATION
Effect of feldspathic porcelain layering on the marginal fit of zirconia and titanium complete-arch fixed implant-supported frameworks Burak Yilmaz, DDS, PhD,a Faris A. Alshahrani, BDS, MS, FRCD(C),b Ediz Kale, DDS, PhD,c and William M. Johnston, PhDd
ABSTRACT Statement of problem. Veneering with porcelain may adversely affect the marginal fit of long-span computer-aided design and computeraided manufacturing (CAD-CAM) implant-supported fixed prostheses. Moreover, data regarding the precision of fit of CAD-CAMefabricated implant-supported complete zirconia fixed dental prostheses (FDPs) before and after porcelain layering are limited. Purpose. The purpose of this in vitro study was to evaluate the effect of porcelain layering on the marginal fit of CAD-CAMefabricated complete-arch implant-supported, screw-retained FDPs with presintered zirconia frameworks compared with titanium. Material and methods. An autopolymerizing acrylic resinefixed complete denture framework prototype was fabricated on an edentulous typodont master model (all-on-4 concept; Nobel Biocare) with 2 straight in the anterior and 2 distally tilted internal-hexagon dental implants in the posterior with multiunit abutments bilaterally in canine and first molar locations. A 3-dimensional (3D) laser scanner (S600 ARTI; Zirkonzahn) was used to digitize the prototype and the master model by using scan bodies to generate a virtual 3D CAD framework. Five presintered zirconia (ICE Zirkon Translucent - 95H16; Zirkonzahn) and 5 titanium (Titan 5 - 95H14; Zirkonzahn) frameworks were fabricated using the CAM milling unit (M1 Wet Heavy Metal Milling Unit; Zirkonzahn).The 1-screw test was applied by fixing the frameworks at the location of the maxillary left first molar abutment, and an industrial computed tomography (CT) scanner (XT H 225 - Basic Configuration; Nikon) was used to scan the framework-model complex to evaluate the passive fit of the frameworks on the master model. The scanned data were transported in standard tessellation language (STL) from Volume Graphics analysis software to PolyWorks analysis software by using the maximum-fit algorithm to fit scanned planes in order to mimic the mating surfaces in the best way. 3D virtual assessment of the marginal fit was performed at the abutment-framework interface at the maxillary right canine (gap 3) and right first molar (gap 4) abutments without prosthetic screws. The facial or buccal aspects of the teeth on frameworks were layered with corresponding porcelain (Initial Dental Ceramic System; GC) and CT-scanned again using the same protocol. Marginal fit measurements were made for 4 groups: titanium (Ti) (control), porcelain-layered titanium (Ti-P) (control), zirconia (Zr), and porcelain-layered zirconia (Zr-P). 3D discrepancy mean values were computed and calculated, and the results were analyzed with a repeated measures 3-way ANOVA using the maximum likelihood estimation method and Bonferroni adjustments for selected pairwise comparison t-tests (a=.05). Results. The 3D fit was measured at gap 3 and gap 4. Statistically significant differences in mean 3D discrepancies were observed between Zr-P (175 mm) and Zr (89 mm) and between Zr-P and Ti-P (71 mm) (P<.001). Conclusions. Porcelain layering had a significant effect on the marginal fit of CAD-CAMefabricated complete-arch implant-supported, screwretained FDPs with partially sintered zirconia frameworks. 3D marginal discrepancy mean values for all groups were within clinically acceptable limits (<120 mm), except for the layered zirconia framework. (J Prosthet Dent 2017;-:---)
Supported by the Ohio State University Implant Research Fund. a Associate Professor, Department of Restorative Science and Prosthodontics, The Ohio State University College of Dentistry, Columbus, Ohio. b Assistant Professor, Imam Abdulrahman Bin Faisal University, College of Dentistry, Department of Substitutive Dental Sciences, Dammam, Saudi Arabia. c Assistant Professor, Department of Prosthodontics, Mustafa Kemal University, Hatay, Turkey. d Professor Emeritus, Division of General Practice and Materials Science, The Ohio State University College of Dentistry, Columbus, Ohio.
THE JOURNAL OF PROSTHETIC DENTISTRY
1
2
Volume
Clinical Implications Clinicians should carefully evaluate the marginal fit of CAD-CAM-fabricated complete-arch 4-implant-supported screw-retained zirconia frameworks particularly before and after porcelain layering.
Splinting dental implants has been an approach to treatment since Brånemark defined the principles of osseointegration.1,2 Splinting enables cost-effective implant therapy, mainly because fewer implants may be used,3 and improved prognosis based on favorable occlusal force distribution4-6 and reduced peri-implant stress levels.7-9 Therefore, decreased mechanical complications may be expected.10 However, biological and mechanical complications may occur if the passive-fit of the splinted implant framework is not achieved.11 Prosthetic or abutment screw loosening or fracture may occur because of inadequately fitting implant frameworks.11,12-15 In addition, bacteria in the microgaps at the abutment-framework interface may negatively affect periimplant tissues.16 Material, production, and even patientrelated outcomes may have different consequences, because the stress is believed to rise significantly, especially during prolonged function.7,12,17-19 Clinicians should fabricate frameworks to fit as accurately as possible,17 because the placement of an implant-supported prosthesis with higher precision will likely lead to fewer biological or technical complications.19 With the introduction of computer-aided design and computer-aided manufacturing (CAD-CAM) technology to prosthetic dentistry, implant-supported restorations fabricated with this technology have become popular.20 Owing to the advances in CAD-CAM and restorative materials, previously complicated and human errore prone production procedures have now been adapted to daily clinical practice, allowing for better accuracy of fit of long-span and large-volume restorations.21,22 Implantsupported fixed dental prosthesis (FDP) frameworks fabricated from various materials with CAD-CAM technology have been reported to fit accurately in completeand partial-arch rehabilitations.21-29 The passive fit and accuracy of long-span implantsupported CAD-CAMefabricated titanium restorations have been described,21,22,30 with studies also focusing on the effect of restoration fabrication stages on the precision of framework fit.31,32 Presintered zirconia CADCAMefabricated FDPs have been reported to exhibit accurate fit for single crowns or partial-arch prostheses.33-37 However, reports on the fitting performance of complete-arch tooth- or implant-supported presintered zirconia frameworks are sparse.21,34,35 Firing cycles and
THE JOURNAL OF PROSTHETIC DENTISTRY
-
Issue
-
veneering techniques may adversely affect the marginal fit of zirconia restorations because of distortion of the zirconia framework.38-41 However, the effect of sintering remains unclear in terms of whether the inherent shrinkage of presintered zirconia leads to any significant linear or volumetric distortion.21 The precision of fit of zirconia and titanium CAD-CAMefabricated implantsupported complete FDPs has been compared.21,42 However, information regarding the precision of fit of CAD-CAMefabricated implant-supported complete FDPs made of presintered zirconia frameworks before and after porcelain layering is lacking. The purpose of this study was to evaluate the effect of porcelain layering on the marginal fit of CAD-CAMe fabricated complete-arch implant-supported, screwretained FDPs with presintered zirconia and titanium frameworks. The null hypothesis was that no difference would be found in 3-dimensional (3D) marginal discrepancies on titanium and zirconia CAD-CAM frameworks before and after porcelain layering. MATERIAL AND METHODS This study followed the methodology of a previous publication.42 A typodont model (all-on-4 concept; Nobel Biocare) with 2 straight (0 degrees to vertical axis) and 2 distally tilted (30 degrees to frontal plane) internalhexagon dental implants (Nobel Active RP 4.3×13 mm; Nobel Biocare) was used to represent a clinical situation in which a completely edentulous maxilla was to be treated with screw-retained, implant-supported FDPs. Multiunit abutments (Multi-unit Abutment Plus Conical Connection RP 2.5 mm; Nobel Biocare) were used on the straight implants in the canine locations, and 30degreeeinclined multiunit abutments (30 Multi-unit Abutment Plus Conical Connection RP 3.5 mm; Nobel Biocare) were used for the tilted implants at the position of the first molars.42 Four abutment-level titanium copings (Temporary Snap Coping Multi-unit Plus; Nobel Biocare) for screw retention were used to support a prototype made of autopolymerizing acrylic resin (Pattern Resin LS; GC) based on a complete denture tooth arrangement. The tooth arrangement was duplicated in acrylic resin, and holes were prepared for titanium copings. The duplicated denture was placed on the model, and the titanium copings were picked up with acrylic resin. The voids around the copings were filled with the same acrylic resin, and the prototype was finalized with contours representing a complete-arch metal-acrylic resin implant-supported prosthesis. The passive fit of the resin prototype was facilitated by sectioning the prototype and reconnecting the pieces with acrylic resin. A controlled, even cutback of 1.5 mm was performed on the facial aspect of the prototype teeth (except for the molars) by using a silicone matrix. The
Yilmaz et al
-
2017
3
Figure 1. A, Scanned master model with screw-retained acrylic resin prototype. B, Digitized scan bodies representing 3-dimensional locations of abutments on master model.
master model with the screw-retained resin prototype on it (all 4 screws tightened) was coated with a scanning spray (Zirko Scanspray; Zirkonzahn) and digitized using a 3D laser scanner (S600 ARTI; Zirkonzahn) (Fig. 1A). Multiunit abutment scan bodies (Nobel Biocare Scanmarker NP-RP; Zirkonzahn) were used to digitize the 3D location of the abutments on the master model, and the resin prototype was scanned from all aspects separately (Fig. 1B). A virtual 3D CAD (Zirkonzahn Software; Zirkonzahn) model was designed from the scanned data (Fig. 2) and sent to a 5-axis +1 milling unit (M1 Wet Heavy Metal Milling Unit; Zirkonzahn) to fabricate 5 frameworks made from presintered zirconia blocks (ICE Zirkon Translucent - 95H16; Zirkonzahn) and 5 frameworks made from titanium blocks (Titan 5- 95H14; Zirkonzahn). All frameworks were finished according to the manufacturer’s instructions.42 The frameworks were subjected to the 1-screw test42-44 on the master model by an experienced prosthodontist (F.A.), who consecutively hand-tightened the prosthetic screws on the abutment on the maxillary left first molar implant and the right canine implant with a manual driver (Screwdriver Manual Multi-unit 25 mm; Nobel Biocare) until the first point of resistance (Fig. 3). The prosthetic screw at the location of the maxillary left first molar was further tightened with a calibrated torque wrench (Manual Torque Wrench - Prosthetic; Nobel Biocare) to a torque of 15 Ncm, and then the screw at the location of the maxillary right first canine was removed. An industrial computed tomography (CT) scanner (XT H 225 - Basic Configuration; Nikon) was used to scan the frameworks for 3D virtual quantitative assessment of the marginal fit of a specimen of each material without porcelain at the abutment-framework circular mating interface at the maxillary right canine (gap 3) and right first molar (gap 4) abutments without prosthetic screws on (Fig. 4).42 After CT scanning, the facial aspects of the zirconia and titanium frameworks (except for the molars) were veneered Yilmaz et al
Figure 2. Virtual 3-dimensional CAD design generated from scanned data.
with layering porcelain (Initial-Dental Ceramic System; GC) according to the manufacturer’s recommendations, mimicking a clinical treatment. Initially, a modifier (GC Initial Zr-FS Frame Modifier) was applied on the zirconia frameworks. Primary dentin (IN-44 Sand and IN-42 Terracotta) material was applied on the cervical and proximal surfaces. Another dentin layer (Fluo-Dentin, FD93) was applied on the incisal area and thinly over the entire labial surfaces. A thin layer of clear fluorescence porcelain (CL-F) was applied over the entire dentin layer. An enamel layer was applied on the CL-F layer to finalize the shape, and the restorations were glazed. A titanium bonding agent (Initial Ti Bonder; GC) was applied on the titanium frameworks. Then 2 opaque porcelain layers were applied. The remaining layers were applied following the same sequence for layering that was used for zirconia specimens, including the glaze layer. Porcelain layering and firing for the frameworks were performed by an experienced dental technician following the manufacturers’ instructions. The thickness of each layer of porcelain was determined with silicone THE JOURNAL OF PROSTHETIC DENTISTRY
4
Volume
-
Issue
-
Figure 3. A, Titanium framework: multiunit abutment interface on maxillary right canine (straight implant). B, Zirconia framework: multiunit abutment interface on maxillary right canine (straight implant).
keys and then with a digital micrometer (electronic micrometer no. 342-741-30; Mitutoyo). The layered specimens were also scanned with the same CT scanner using the same protocol. Four final groups (n=5/group) were established for marginal fit evaluation: titanium framework (Ti), zirconia framework (Zr), and their respective repeated-measures porcelain-veneered titanium framework (Ti-P) and porcelain-veneered zirconia framework (Zr-P) (Fig. 5). The scanned data were reconstructed to generate polygonal mesh models in standard tessellation language (STL) file format from Volume Graphics analysis software and then transported to PolyWorks analysis software in order to extract measurements at the specified locations. Each of the opposing 3D surfaces were fitted using a maximum-fit algorithm to mimic the mating surfaces in the best way.42,45 This method defines a plane by picking the first 3 points of contact as a virtual plane is brought into contact with the data, thus mitigating the common measurement issues related to measuring 2 nonparallel and not perfectly planar features. This method is the standard treatment of such features in metrology to determine gaps between planar features and simulates how 2 real (nonperfect) planar surfaces come into contact with each other.46 In this method, the first of the planar features is made the reference feature, and the second feature is then reduced to a single point at the centroid of that second planar feature. The resulting plane-to-point measurement is then unambiguously understood as the perpendicular or normal distance between them. The circular mating plane of the abutments at the abutment-framework interface was admitted as reference. The measurements were made by creating a line perpendicular to the reference plane surface that ended at the centroid on the surface of the opposing plane, the circular mating plane of the framework at the abutment-framework interface (Fig. 6). The length of the line was considered to be the 3D marginal discrepancy value or the shortest distance THE JOURNAL OF PROSTHETIC DENTISTRY
Figure 4. Four locations of 3-dimensional virtual quantitative assessment of passive fit with 1-screw test (gaps 2, 3, and 4).
between the 2 planar features. The entire 3D surface data for each side of the gap were used to determine this value. A maximal-fit plane rather than an average plane was used. All inspections were performed at a laboratory with ISO/IEC 1702547 accreditation by using equipment calibrated with standards traceable to the International System of Units through the National Metrological Institutes. The expanded measurement uncertainty was identified as 11+30L mm, where ‘L’ was a distance measured in meters. The expected uncertainty was detected at a level of confidence of approximately 95%. The 3D discrepancy value means and 95% confidence limits for gap 3 and gap 4 were calculated. The results were analyzed with a repeated-measures 3-way ANOVA with statistical software (SAS 9.3; SAS Institute) by using the restricted maximum likelihood estimation and Satterthwaite degrees-of-freedom methods. For this analysis, the between-subjects factor was the material and the within subjects factors were the porcelain and the gap; all interactions of these 3 main effects were included in the model. Bonferroni corrections were then applied to Yilmaz et al
-
2017
5
Figure 5. A, Zirconia framework on master model before layering. B, Layered zirconia and titanium frameworks.
Figure 6. A, Three-dimensional virtual view of reference plane surface and opposing circular mating plane of framework along with misfit present at abutment-framework interface. B, 3-dimensional marginal discrepancy values computed at different areas of abutment-framework interface at certain location with color map range of ±0.250 mm. (Note that circle not continuous in some areas. Areas of misfit as low as beyond precision of industrial computed tomography scanner used.)
justified pairwise comparisons using the Student t tests (overall a=.05). RESULTS The means and 95% confidence limits for all measured gaps are shown in Figure 7. Data for the Ti and Zr were reported in a previous study.42 The ANOVA indicated no statistically significant effect of the gap (P.075), but did indicate a statistically significant interaction between the material and the porcelain layering (P<.001). The mean discrepancies for Ti, Ti-P, Zr, and Zr-P were 88, 71, 89, and 175 mm, respectively, regarding both gaps 3 and 4. Statistically significant differences were found between Zr and Zr-P and between Ti-P and Zr-P (P<.001), but no such difference was found between Ti and Ti-P (P=.768). DISCUSSION The null hypothesis that no difference would be found in 3D marginal discrepancies before and after porcelain
Yilmaz et al
layering was rejected for zirconia CAD-CAMefabricated frameworks; however, no statistical difference was detected between the discrepancies of Ti and Ti-P. The passive fit of an implant-supported structure has been defined as the state in which a nonfunctioning structure sitting on the implants does not exert any strain on its supporting base; thus, the implants are stress-free as if they are in their preloaded condition.11,48,49 The 1-screw test is commonly used to assess whether the passive fit has been achieved.25,26,31 The criterion for clinical acceptability of this test, particularly applicable for complete-arch frameworks, is based on tightening the most distal abutment screw without creating a marginal discrepancy at the abutment-framework interface on any of the remaining implants.43,50 The nature of the 1-screw test is that it relies only on naked-eye observations, making the evaluation of passive fit a matter of debate.25,26,50 Brånemark2 was the first to bring objectivity to the definition of the phenomenon, quantifying the level of discrepancy by suggesting it should not be more than 10 mm. Subsequently, Jemt31
THE JOURNAL OF PROSTHETIC DENTISTRY
6
Volume
3D Distance (µm)
300
200
100
0 Gap: Porcelain: Material:
3 4 3 4 Without With Titanium
3 4 3 4 Without With Zirconia
Figure 7. Three-dimensional marginal discrepancy mean values with confidence limits.
proposed that discrepancies of about 150 mm may be clinically acceptable. Absolute passive fit is thought to be impossible to achieve.11 While a clinically acceptable threshold of marginal misfit for tooth- or implant-supported FDPs has not yet been supported by scientific evidence,25 it has been frequently claimed to be less than 120 mm.27,51,52 However, others28,53 have claimed, based on their clinical observations, that the limit of marginal misfit may be up to 200 mm. The 3D marginal discrepancy mean values in Zr-P were less than 180 mm with around 95% of the measurements under 200 mm for gap 3 and 85% for gap 4. Further research is needed to establish the optimum limits of passive fit for implant-supported restorations. Katsoulis et al21 investigated the passive fit of 10-unit CAD-CAM titanium frameworks on 6 implants with the 1-screw test. By scanning electron microscope observation, they found mean vertical discrepancy values between 17 and 24 mm on the implants most distant from the terminal screw-retained implant, which had been placed at the maxillary right canine and second premolar, corresponding to locations at gap 3 and gap 4 in the present study. Another study by Katsoulis et al25 using the same model revealed mean discrepancy values of 21 to 30 mm at the same locations for complete-arch CADCAMefabricated titanium frameworks. The maximum range of vertical discrepancy measured in these studies21,25 varied up to 49 and 83 mm considering all 5 implants without screws in place, except for 1. The results of Ti in the present study showed lower precision of fit compared with those studies, but still comparable with the clinically acceptable fit of less than 120 mm. The layering process had no significant influence on the passive fit of the control (Ti) group in the current THE JOURNAL OF PROSTHETIC DENTISTRY
-
Issue
-
study (P=.768). The insignificant effect of porcelain layering on complete-arch implant-supported CADCAM titanium frameworks is supported by the results of other studies.25,32 The maximum range of discrepancy of the complete-arch layered titanium frameworks measured at the implant level for passive fit has been reported to be between 38 and 62 mm.22,25 This discrepancy is lower than the Ti-P values in the current study. Nevertheless, the maximum range of all these studies is within clinically acceptable limits (120 mm). The effect of layering on the marginal fit of CADCAMefabricated complete-arch implant-supported, screw-retained FDPs with presintered zirconia framework was significant according to the results of this study. Katsoulis et al21 have investigated the passive fit of complete-arch implant-supported frameworks made of presintered zirconia on 6 implants by using the 1-screw test. The implant locations in that study were similar to those used in the current study. The mean vertical discrepancies in that study for the zirconia frameworks fabricated through 3D laser scanning and CAD-CAM, as in the current study, were reported to be 48 mm (maximum range: 93 mm) and 77 mm (maximum range: 142 mm) for the maxillary right canine and second premolar. The 3D marginal discrepancy means values for gap 3 and gap 4 obtained in the current study were 84 mm (maximum range: 104 mm) and 94 mm (maximum range: 133 mm). The results of both the current and Katsoulis et al21 studies are similar for zirconia frameworks before the layering process. The 3D marginal discrepancy mean values for all groups in this study were within the clinically acceptable threshold of 120 mm, except for group Zr-P (175 mm). Pak et al40 investigated the effect of porcelain layering on the marginal adaptation of presintered and postsintered zirconia crowns and reported that porcelain layering decreased marginal adaptation. Torabi et al41 reported that presintered zirconia crowns subjected to various veneering techniques, each involving repeated firing, significantly altered the marginal fit. However, none of the prostheses in those studies showed the large increase in mean marginal discrepancy values seen in the present study. This may be attributed to the larger volume of the prostheses in this study compared with that in previous studies. Reports further suggest that sintering alone may initiate distortion of the framework of long-span presintered zirconia prostheses.34,35 Further research is needed to improve knowledge on this subject. The expanded measurement uncertainty (11+30L mm) in this study should be considered in interpreting the results. If it was assumed by a rough computation that the L value was 0.001 m (1 mm), which is an overestimated value for 3D marginal discrepancy that might have been detected in the current study, then the expanded measurement uncertainty would be around Yilmaz et al
-
2017
11 mm, and that would be the maximum value. It was assumed that because gap 2 was closest to the tightened screw during the 1-screw test, the 3D marginal discrepancy mean values of gap 2 would potentially be lower than for gap 3 and gap 4. This would be consistent with the published literature, as similar results have been reported by previous studies.21,25 Therefore, only gaps that crossed the midline and were farthest from the test screw (gap 3 and gap 4) were considered when the discrepancy was measured. A limitation of the current study was the use of an indirect measurement technique; virtual assessment based on mathematically calculated values by means of software. An advantage of this analytic approach is 3D evaluation in different planes and dimensions of digitally superimposed scanned data. However, procedures like scanning and data transfer to generate STL virtual models may also present with errors, which should be considered when interpreting results.21,29 In addition, the frameworks were fabricated on a master model from a completely seated resin prototype. Therefore, the transfer of the implant positions from the clinical situation to the master model was not tested primarily to focus on the effect of the fabrication stages (CAM milling and layering) on the marginal fit. Both conventional and digital clinical transfer procedures of the implant positions to the master cast may also present with some inaccuracies and contribute to the final marginal discrepancy. Also, only 1 site (implant at maxillary right molar site) was used to secure the screw for the 1-screw test used in this study. The fit of the framework may differ when 1 screw is used in different implant sites to evaluate the fit discrepancy at other implant sites. Future studies should secure the screw at different sites to measure the discrepancies at the nonsecured interfaces. The results of this study should be interpreted considering that only 1 CAD-CAM system was used with its milling machine and blocks. Different systems may perform differently. CONCLUSIONS Within the limitations of this in vitro study, the following conclusions were drawn: 1. Absolute passive fit was not achieved at any stage of fabrication for the CAD-CAMefabricated completearch implant-supported, screw-retained FDPs with presintered zirconia or titanium frameworks. 2. Porcelain layering had an insignificant effect on the 3D marginal integrity of CAD-CAMefabricated titanium complete-arch implant-supported, screwretained FDP frameworks; however, the effect of porcelain layering on the marginal fit of partially sintered zirconia frameworks was significant. 3. Three-dimensional mean marginal discrepancy values for all groups were within the clinically Yilmaz et al
7
acceptable limits (<120 mm) except for the porcelainlayered zirconia frameworks. REFERENCES 1. Brånemark PI, Hansson BO, Adell R, Breine U, Lindström J, Hallén O, et al. Osseointegrated implants in the treatment of the edentulous jaw. Experience from a 10-year period. Scand J Plast Reconstr Surg Suppl 1977;16:1-132. 2. Brånemark PI. Osseointegration and its experimental back ground. J Prosthet Dent 1983;50:399-410. 3. Babbush CA, Kanawati A, Kotsakis GA, Hinrichs JE. Patient-related and financial outcomes analysis of conventional full-arch rehabilitation versus the All-on-4 concept: A cohort study. Implant Dent 2014;23:218-24. 4. Skalak R. Biomechanical considerations in osseointegrated prostheses. J Prosthet Dent 1983;49:843-8. 5. Guichet DL, Yoshinobu D, Caputo AA. Effect of splinting and interproximal contact tightness on load transfer by implant restorations. J Prosthet Dent 2002;87:528-35. 6. Clelland NL, Seidt JD, Daroz LG, McGlumphy EA. Comparison of strains for splinted and nonsplinted implant prostheses using three-dimensional image correlation. Int J Oral Maxillofac Implants 2010;25:953-9. 7. Bergkvist G, Simonsson K, Rydberg K, Johansson F, Dérand T. A finite element analysis of stress distribution in bone tissue surrounding uncoupled or splinted dental implants. Clin Implant Dent Relat Res 2008;10:40-6. 8. Wang TM, Leu LJ, Wang J, Lin LD. Effects of prosthesis materials and prosthesis splinting on peri-implant bone stress around implants in poorquality bone: A numeric analysis. Int J Oral Maxillofac Implants 2002;17: 231-7. 9. Shigemitsu R, Ogawa T, Matsumoto T, Yoda N, Gunji Y, Yamakawa Y, et al. Stress distribution in the peri-implant bone with splinted and non-splinted implants by in vivo loading data-based finite element analysis. Odontology 2013;101:222-6. 10. Jivraj S, Chee W. Treatment planning of implants in posterior quadrants. Br Dent J 2006;201:13-23. 11. Sahin S, Cehreli MC. The significance of passive framework fit in implant prosthodontics: current status. Implant Dent 2001;10:85-92. 12. Jokstad A, Shokati B. New 3D technologies applied to assess the long-term clinical effects of misfit of the full jaw fixed prosthesis on dental implants. Clin Oral Implants Res 2015;26:1129-34. 13. Yannikakis S, Prombonas A. Improving the fit of implant prosthetics: An in vitro study. Int J Oral Maxillofac Implants 2013;28:126-34. 14. Gunne J, Jemt T, Lindén B. Implant treatment in partially edentulous patients: a report on prostheses after 3 years. Int J Prosthodont 1994;7: 143-8. 15. Kreissl ME, Gerds T, Muche R, Heydecke G, Strub JR. Technical complications of implant-supported fixed partial dentures in partially edentulous cases after an average observation period of 5 years. Clin Oral Implants Res 2007;18:720-6. 16. Scarano A, Assenza B, Piattelli M, Iezzi G, Leghissa GC, Quaranta A, et al. A 16-year study of the microgap between 272 human titanium implants and their abutments. J Oral Implantol 2005;31:269-75. 17. de França DG, Morais MH, das Neves FD, Barbosa GA. Influence of CAD/ CAM on the fit accuracy of implant-supported zirconia and cobalt-chromium fixed dental prostheses. J Prosthet Dent 2015;113:22-8. 18. Kunavisarut C, Lang LA, Stoner BR, Felton DA. Finite element analysis on dental implant-supported prostheses without passive fit. J Prosthodont 2002;11:30-40. 19. Abduo J, Judge RB. Implications of implant framework misfit: A systematic review of biomechanical sequelae. Int J Oral Maxillofac Implants 2014;29: 608-21. 20. Venezia P, Torsello F, Cavalcanti R, D’Amato S. Retrospective analysis of 26 complete-arch implant-supported monolithic zirconia prostheses with feldspathic porcelain veneering limited to the facial surface. J Prosthet Dent 2015;114:506-12. 21. Katsoulis J, Mericske-Stern R, Rotkina L, Zbӓren C, Enkling N, Blatz MB. Precision of fit of implant-supported screw retained 10-unit computer-aideddesigned and computer-aided- manufactured frameworks made from zirconium dioxide and titanium: An in vitro study. Clin Oral Implants Res 2014;25:165-74. 22. Katsoulis J, Müller P, Mericske-Stern R, Blatz MB. CAD/CAM fabrication accuracy of long- vs. short-span implant supported FDPs. Clin Oral Implants Res 2015;26:245-9. 23. Takahashi T, Gunne J. Fit of implant frameworks: An in vitro comparison between two fabrication techniques. J Prosthet Dent 2003;89:256-60. 24. Berejuk HM, Shimizu RH, de Mattias Sartori IA, Valgas L, Tiossi R. Vertical microgap and passivity of fit of three-unit implant-supported frameworks fabricated using different techniques. Int J Oral Maxillofac Implants 2014;29: 1064-70.
THE JOURNAL OF PROSTHETIC DENTISTRY
8
25. Katsoulis J, Mericske-Stern R, Enkling N, Katsoulis K, Blatz MB. In vitro precision of fit of computer-aided designed and computer-aided manufactured titanium screw-retained fixed dental prostheses before and after ceramic veneering. Clin Oral Implants Res 2015;26:44-9. 26. Abduo J, Bennani V, Waddell N, Lyons K, Swain M. Assessing the fit of implant fixed prostheses: A critical review. Int J Oral Maxillofac Implants 2010;25:506-15. 27. Karatas¸li O, Kurso glu P, Capa N, Kazazo g lu E. Comparison of the marginal fit of different coping materials and designs produced by computer aided manufacturing systems. Dent Mater J 2011;30:97-102. 28. Reich S, Wichmann M, Nkenke E, Proeschel P. Clinical fit of all-ceramic three-unit fixed partial dentures, generated with three different CAD/CAM systems. Eur J Oral Sci 2005;113:174-9. 29. Hjalmarsson L, Ortorp A, Smedberg JI, Jemt T. Precision of fit to implants: A comparison of Cresco and Procera implant bridge frameworks. Clin Implant Dent Relat Res 2010;12:271-80. 30. Paniz G, Stellini E, Meneghello R, Cerardi A, Gobbato EA, Bressan E. The precision of fit of cast and milled full-arch implant-supported restorations. Int J Oral Maxillofac Implants 2013;28:687-93. 31. Jemt T. Failures and complications in 391 consecutively inserted fixed prostheses supported by Brånemark implants in edentulous jaws: A study of treatment from the time of prosthesis placement to the first annual checkup. Int J Oral Maxillofac Implants 1991;6:270-6. 32. Ortorp A, Jemt T, Bäck T, Jälevik T. Comparisons of precision of fit between cast and CNC-milled titanium implant frameworks for the edentulous mandible. Int J Prosthodont 2003;16:194-200. 33. Abduo J. Fit of CAD/CAM implant frameworks: A comprehensive review. J Oral Implantol 2014;40:758-66. 34. Beuer F, Neumeier P, Naumann M. Marginal fit of 14-unit zirconia fixed dental prosthesis retainers. J Oral Rehabil 2009;36:142-9. 35. Sachs C, Groesser J, Stadelmann M, Schweiger J, Erdelt K, Beuer F. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater 2014;30:817-23. 36. Kale E, Seker E, Yilmaz B, Özcelik TB. Effect of cement space on the marginal fit of CAD/CAM-fabricated monolithic zirconia crowns. J Prosthet Dent 2016;116:890-5. 37. Kale E, Yilmaz B, Seker E, Özcelik TB. Effect of fabrication stages and cementation on the marginal fit of CAD/CAM monolithic zirconia crowns. J Prosthet Dent 2017;118:736-41. 38. Abduo J, Lyons K, Swain M. Fit of zirconia fixed partial denture: A systematic review. J Oral Rehabil 2010;37:866-76. 39. Kohorst P, Brinkmann H, Dittmer MP, Borchers L, Stiesch M. Influence of the veneering process on the marginal fit of zirconia fixed dental prostheses. J Oral Rehabil 2010;37:283-91. 40. Pak HS, Han JS, Lee JB, Kim SH, Yang JH. Influence of porcelain veneering on the marginal fit of Digident and Lava CAD/CAM zirconia ceramic crowns. J Adv Prosthodont 2010;2:33-8. 41. Torabi K, Vojdani M, Giti R, Taghva M, Pardis S. The effect of various veneering techniques on the marginal fit of zirconia copings. J Adv Prosthodont 2015;7:233-9. 42. Al-Meraikhi H, Yilmaz B, McGlumphy EA, Brantley WA, Johnston WM. In vitro fit of CAD-CAM complete arch screw-retained
THE JOURNAL OF PROSTHETIC DENTISTRY
Volume
43. 44. 45.
46. 47.
48. 49. 50. 51. 52. 53.
-
Issue
-
titanium and zirconia implant prostheses fabricated on 4 implants. J Prosthet Dent July 2017;15. doi: 10.1016/j.prosdent.2017.04.023. [Epub ahead of print.] Eisenmann E, Mokabberi A, Walter MH, Freesmeyer WB. Improving the fit of implant-supported superstructures using the spark erosion technique. Int J Oral Maxillofac Implants 2004;19:810-8. White GE. Osseointegrated dental technology. London: Quintessence; 1993. p. 61,123-124,129. Al-Meraikhi H, Yilmaz B, McGlumphy EA, Brantley WA, Johnston WM. Distortion of CAD/CAM-fabricated implant-fixed titanium and zirconia complete dental prosthesis frameworks. J Prosthet Dent 3 May 2017. doi: 10.1016/j.prosdent.2017.02.003. [Epub ahead of print.] Figliola RS, Beasley DE. Dimensional measurements: Metrology. In: Figliola RS, editor. Theory and design for mechanical measurements. New York: Wiley; 1991. p. 417-25. International Organization for Standardization. ISO/IEC 17025. General requirements for the competence of testing and calibration laboratories. Geneva: International Organization for Standardization; 2005. Available at: http://www.iso.org/webstore.htm. Watanabe F, Uno I, Hata Y, Neuendorff G, Kirsch A. Analysis of stress distribution in a screw-retained implant prosthesis. Int J Oral Maxillofac Implants 2000;15:209-18. Karl M, Rosch S, Graef F, Taylor TD, Heckmann SM. Strain situation after fixation of three-unit ceramic veneered implant superstructures. Implant Dent 2005;14:157-65. Tan KB, Rubenstein JE, Nicholls JI, Yuodelis RA. Three-dimensional analysis of the casting accuracy of one-piece, osseointegrated implant-retained prostheses. Int J Prosthodont 1993;6:346-63. McLean JW, von Fraunhofer JA. The estimation of cement film thickness by an in vivo technique. Br Dent J 1971;131:107-11. Sorensen JA. A standardized method for determination of crown margin fidelity. J Prosthet Dent 1990;64:18-24. Wolfart S, Wegner SM, Al-Halabi A, Kern M. Clinical evaluation of marginal fit of a new experimental all-ceramic system before and after cementation. Int J Prosthodont 2003;16:587-92.
Corresponding author: Dr Ediz Kale Mustafa Kemal University Faculty of Dentistry, Department of Prosthodontics 31060 Antakya-Hatay TURKEY Email: [email protected] Acknowledgments The authors thank Dr Hadi Al-Meraikhi for his collaboration. Copyright © 2017 by the Editorial Council for The Journal of Prosthetic Dentistry.
Yilmaz et al
Effect of feldspathic porcelain layering on the marginal fit of zirconia and titanium complete-arch fixed implant-supported frameworks Burak Yilmaz, DDS, PhD,a Faris A. Alshahrani, BDS, MS, FRCD(C),b Ediz Kale, DDS, PhD,c and William M. Johnston, PhDd
ABSTRACT Statement of problem. Veneering with porcelain may adversely affect the marginal fit of long-span computer-aided design and computeraided manufacturing (CAD-CAM) implant-supported fixed prostheses. Moreover, data regarding the precision of fit of CAD-CAMefabricated implant-supported complete zirconia fixed dental prostheses (FDPs) before and after porcelain layering are limited. Purpose. The purpose of this in vitro study was to evaluate the effect of porcelain layering on the marginal fit of CAD-CAMefabricated complete-arch implant-supported, screw-retained FDPs with presintered zirconia frameworks compared with titanium. Material and methods. An autopolymerizing acrylic resinefixed complete denture framework prototype was fabricated on an edentulous typodont master model (all-on-4 concept; Nobel Biocare) with 2 straight in the anterior and 2 distally tilted internal-hexagon dental implants in the posterior with multiunit abutments bilaterally in canine and first molar locations. A 3-dimensional (3D) laser scanner (S600 ARTI; Zirkonzahn) was used to digitize the prototype and the master model by using scan bodies to generate a virtual 3D CAD framework. Five presintered zirconia (ICE Zirkon Translucent - 95H16; Zirkonzahn) and 5 titanium (Titan 5 - 95H14; Zirkonzahn) frameworks were fabricated using the CAM milling unit (M1 Wet Heavy Metal Milling Unit; Zirkonzahn).The 1-screw test was applied by fixing the frameworks at the location of the maxillary left first molar abutment, and an industrial computed tomography (CT) scanner (XT H 225 - Basic Configuration; Nikon) was used to scan the framework-model complex to evaluate the passive fit of the frameworks on the master model. The scanned data were transported in standard tessellation language (STL) from Volume Graphics analysis software to PolyWorks analysis software by using the maximum-fit algorithm to fit scanned planes in order to mimic the mating surfaces in the best way. 3D virtual assessment of the marginal fit was performed at the abutment-framework interface at the maxillary right canine (gap 3) and right first molar (gap 4) abutments without prosthetic screws. The facial or buccal aspects of the teeth on frameworks were layered with corresponding porcelain (Initial Dental Ceramic System; GC) and CT-scanned again using the same protocol. Marginal fit measurements were made for 4 groups: titanium (Ti) (control), porcelain-layered titanium (Ti-P) (control), zirconia (Zr), and porcelain-layered zirconia (Zr-P). 3D discrepancy mean values were computed and calculated, and the results were analyzed with a repeated measures 3-way ANOVA using the maximum likelihood estimation method and Bonferroni adjustments for selected pairwise comparison t-tests (a=.05). Results. The 3D fit was measured at gap 3 and gap 4. Statistically significant differences in mean 3D discrepancies were observed between Zr-P (175 mm) and Zr (89 mm) and between Zr-P and Ti-P (71 mm) (P<.001). Conclusions. Porcelain layering had a significant effect on the marginal fit of CAD-CAMefabricated complete-arch implant-supported, screwretained FDPs with partially sintered zirconia frameworks. 3D marginal discrepancy mean values for all groups were within clinically acceptable limits (<120 mm), except for the layered zirconia framework. (J Prosthet Dent 2017;-:---)
Supported by the Ohio State University Implant Research Fund. a Associate Professor, Department of Restorative Science and Prosthodontics, The Ohio State University College of Dentistry, Columbus, Ohio. b Assistant Professor, Imam Abdulrahman Bin Faisal University, College of Dentistry, Department of Substitutive Dental Sciences, Dammam, Saudi Arabia. c Assistant Professor, Department of Prosthodontics, Mustafa Kemal University, Hatay, Turkey. d Professor Emeritus, Division of General Practice and Materials Science, The Ohio State University College of Dentistry, Columbus, Ohio.
THE JOURNAL OF PROSTHETIC DENTISTRY
1
2
Volume
Clinical Implications Clinicians should carefully evaluate the marginal fit of CAD-CAM-fabricated complete-arch 4-implant-supported screw-retained zirconia frameworks particularly before and after porcelain layering.
Splinting dental implants has been an approach to treatment since Brånemark defined the principles of osseointegration.1,2 Splinting enables cost-effective implant therapy, mainly because fewer implants may be used,3 and improved prognosis based on favorable occlusal force distribution4-6 and reduced peri-implant stress levels.7-9 Therefore, decreased mechanical complications may be expected.10 However, biological and mechanical complications may occur if the passive-fit of the splinted implant framework is not achieved.11 Prosthetic or abutment screw loosening or fracture may occur because of inadequately fitting implant frameworks.11,12-15 In addition, bacteria in the microgaps at the abutment-framework interface may negatively affect periimplant tissues.16 Material, production, and even patientrelated outcomes may have different consequences, because the stress is believed to rise significantly, especially during prolonged function.7,12,17-19 Clinicians should fabricate frameworks to fit as accurately as possible,17 because the placement of an implant-supported prosthesis with higher precision will likely lead to fewer biological or technical complications.19 With the introduction of computer-aided design and computer-aided manufacturing (CAD-CAM) technology to prosthetic dentistry, implant-supported restorations fabricated with this technology have become popular.20 Owing to the advances in CAD-CAM and restorative materials, previously complicated and human errore prone production procedures have now been adapted to daily clinical practice, allowing for better accuracy of fit of long-span and large-volume restorations.21,22 Implantsupported fixed dental prosthesis (FDP) frameworks fabricated from various materials with CAD-CAM technology have been reported to fit accurately in completeand partial-arch rehabilitations.21-29 The passive fit and accuracy of long-span implantsupported CAD-CAMefabricated titanium restorations have been described,21,22,30 with studies also focusing on the effect of restoration fabrication stages on the precision of framework fit.31,32 Presintered zirconia CADCAMefabricated FDPs have been reported to exhibit accurate fit for single crowns or partial-arch prostheses.33-37 However, reports on the fitting performance of complete-arch tooth- or implant-supported presintered zirconia frameworks are sparse.21,34,35 Firing cycles and
THE JOURNAL OF PROSTHETIC DENTISTRY
-
Issue
-
veneering techniques may adversely affect the marginal fit of zirconia restorations because of distortion of the zirconia framework.38-41 However, the effect of sintering remains unclear in terms of whether the inherent shrinkage of presintered zirconia leads to any significant linear or volumetric distortion.21 The precision of fit of zirconia and titanium CAD-CAMefabricated implantsupported complete FDPs has been compared.21,42 However, information regarding the precision of fit of CAD-CAMefabricated implant-supported complete FDPs made of presintered zirconia frameworks before and after porcelain layering is lacking. The purpose of this study was to evaluate the effect of porcelain layering on the marginal fit of CAD-CAMe fabricated complete-arch implant-supported, screwretained FDPs with presintered zirconia and titanium frameworks. The null hypothesis was that no difference would be found in 3-dimensional (3D) marginal discrepancies on titanium and zirconia CAD-CAM frameworks before and after porcelain layering. MATERIAL AND METHODS This study followed the methodology of a previous publication.42 A typodont model (all-on-4 concept; Nobel Biocare) with 2 straight (0 degrees to vertical axis) and 2 distally tilted (30 degrees to frontal plane) internalhexagon dental implants (Nobel Active RP 4.3×13 mm; Nobel Biocare) was used to represent a clinical situation in which a completely edentulous maxilla was to be treated with screw-retained, implant-supported FDPs. Multiunit abutments (Multi-unit Abutment Plus Conical Connection RP 2.5 mm; Nobel Biocare) were used on the straight implants in the canine locations, and 30degreeeinclined multiunit abutments (30 Multi-unit Abutment Plus Conical Connection RP 3.5 mm; Nobel Biocare) were used for the tilted implants at the position of the first molars.42 Four abutment-level titanium copings (Temporary Snap Coping Multi-unit Plus; Nobel Biocare) for screw retention were used to support a prototype made of autopolymerizing acrylic resin (Pattern Resin LS; GC) based on a complete denture tooth arrangement. The tooth arrangement was duplicated in acrylic resin, and holes were prepared for titanium copings. The duplicated denture was placed on the model, and the titanium copings were picked up with acrylic resin. The voids around the copings were filled with the same acrylic resin, and the prototype was finalized with contours representing a complete-arch metal-acrylic resin implant-supported prosthesis. The passive fit of the resin prototype was facilitated by sectioning the prototype and reconnecting the pieces with acrylic resin. A controlled, even cutback of 1.5 mm was performed on the facial aspect of the prototype teeth (except for the molars) by using a silicone matrix. The
Yilmaz et al
-
2017
3
Figure 1. A, Scanned master model with screw-retained acrylic resin prototype. B, Digitized scan bodies representing 3-dimensional locations of abutments on master model.
master model with the screw-retained resin prototype on it (all 4 screws tightened) was coated with a scanning spray (Zirko Scanspray; Zirkonzahn) and digitized using a 3D laser scanner (S600 ARTI; Zirkonzahn) (Fig. 1A). Multiunit abutment scan bodies (Nobel Biocare Scanmarker NP-RP; Zirkonzahn) were used to digitize the 3D location of the abutments on the master model, and the resin prototype was scanned from all aspects separately (Fig. 1B). A virtual 3D CAD (Zirkonzahn Software; Zirkonzahn) model was designed from the scanned data (Fig. 2) and sent to a 5-axis +1 milling unit (M1 Wet Heavy Metal Milling Unit; Zirkonzahn) to fabricate 5 frameworks made from presintered zirconia blocks (ICE Zirkon Translucent - 95H16; Zirkonzahn) and 5 frameworks made from titanium blocks (Titan 5- 95H14; Zirkonzahn). All frameworks were finished according to the manufacturer’s instructions.42 The frameworks were subjected to the 1-screw test42-44 on the master model by an experienced prosthodontist (F.A.), who consecutively hand-tightened the prosthetic screws on the abutment on the maxillary left first molar implant and the right canine implant with a manual driver (Screwdriver Manual Multi-unit 25 mm; Nobel Biocare) until the first point of resistance (Fig. 3). The prosthetic screw at the location of the maxillary left first molar was further tightened with a calibrated torque wrench (Manual Torque Wrench - Prosthetic; Nobel Biocare) to a torque of 15 Ncm, and then the screw at the location of the maxillary right first canine was removed. An industrial computed tomography (CT) scanner (XT H 225 - Basic Configuration; Nikon) was used to scan the frameworks for 3D virtual quantitative assessment of the marginal fit of a specimen of each material without porcelain at the abutment-framework circular mating interface at the maxillary right canine (gap 3) and right first molar (gap 4) abutments without prosthetic screws on (Fig. 4).42 After CT scanning, the facial aspects of the zirconia and titanium frameworks (except for the molars) were veneered Yilmaz et al
Figure 2. Virtual 3-dimensional CAD design generated from scanned data.
with layering porcelain (Initial-Dental Ceramic System; GC) according to the manufacturer’s recommendations, mimicking a clinical treatment. Initially, a modifier (GC Initial Zr-FS Frame Modifier) was applied on the zirconia frameworks. Primary dentin (IN-44 Sand and IN-42 Terracotta) material was applied on the cervical and proximal surfaces. Another dentin layer (Fluo-Dentin, FD93) was applied on the incisal area and thinly over the entire labial surfaces. A thin layer of clear fluorescence porcelain (CL-F) was applied over the entire dentin layer. An enamel layer was applied on the CL-F layer to finalize the shape, and the restorations were glazed. A titanium bonding agent (Initial Ti Bonder; GC) was applied on the titanium frameworks. Then 2 opaque porcelain layers were applied. The remaining layers were applied following the same sequence for layering that was used for zirconia specimens, including the glaze layer. Porcelain layering and firing for the frameworks were performed by an experienced dental technician following the manufacturers’ instructions. The thickness of each layer of porcelain was determined with silicone THE JOURNAL OF PROSTHETIC DENTISTRY
4
Volume
-
Issue
-
Figure 3. A, Titanium framework: multiunit abutment interface on maxillary right canine (straight implant). B, Zirconia framework: multiunit abutment interface on maxillary right canine (straight implant).
keys and then with a digital micrometer (electronic micrometer no. 342-741-30; Mitutoyo). The layered specimens were also scanned with the same CT scanner using the same protocol. Four final groups (n=5/group) were established for marginal fit evaluation: titanium framework (Ti), zirconia framework (Zr), and their respective repeated-measures porcelain-veneered titanium framework (Ti-P) and porcelain-veneered zirconia framework (Zr-P) (Fig. 5). The scanned data were reconstructed to generate polygonal mesh models in standard tessellation language (STL) file format from Volume Graphics analysis software and then transported to PolyWorks analysis software in order to extract measurements at the specified locations. Each of the opposing 3D surfaces were fitted using a maximum-fit algorithm to mimic the mating surfaces in the best way.42,45 This method defines a plane by picking the first 3 points of contact as a virtual plane is brought into contact with the data, thus mitigating the common measurement issues related to measuring 2 nonparallel and not perfectly planar features. This method is the standard treatment of such features in metrology to determine gaps between planar features and simulates how 2 real (nonperfect) planar surfaces come into contact with each other.46 In this method, the first of the planar features is made the reference feature, and the second feature is then reduced to a single point at the centroid of that second planar feature. The resulting plane-to-point measurement is then unambiguously understood as the perpendicular or normal distance between them. The circular mating plane of the abutments at the abutment-framework interface was admitted as reference. The measurements were made by creating a line perpendicular to the reference plane surface that ended at the centroid on the surface of the opposing plane, the circular mating plane of the framework at the abutment-framework interface (Fig. 6). The length of the line was considered to be the 3D marginal discrepancy value or the shortest distance THE JOURNAL OF PROSTHETIC DENTISTRY
Figure 4. Four locations of 3-dimensional virtual quantitative assessment of passive fit with 1-screw test (gaps 2, 3, and 4).
between the 2 planar features. The entire 3D surface data for each side of the gap were used to determine this value. A maximal-fit plane rather than an average plane was used. All inspections were performed at a laboratory with ISO/IEC 1702547 accreditation by using equipment calibrated with standards traceable to the International System of Units through the National Metrological Institutes. The expanded measurement uncertainty was identified as 11+30L mm, where ‘L’ was a distance measured in meters. The expected uncertainty was detected at a level of confidence of approximately 95%. The 3D discrepancy value means and 95% confidence limits for gap 3 and gap 4 were calculated. The results were analyzed with a repeated-measures 3-way ANOVA with statistical software (SAS 9.3; SAS Institute) by using the restricted maximum likelihood estimation and Satterthwaite degrees-of-freedom methods. For this analysis, the between-subjects factor was the material and the within subjects factors were the porcelain and the gap; all interactions of these 3 main effects were included in the model. Bonferroni corrections were then applied to Yilmaz et al
-
2017
5
Figure 5. A, Zirconia framework on master model before layering. B, Layered zirconia and titanium frameworks.
Figure 6. A, Three-dimensional virtual view of reference plane surface and opposing circular mating plane of framework along with misfit present at abutment-framework interface. B, 3-dimensional marginal discrepancy values computed at different areas of abutment-framework interface at certain location with color map range of ±0.250 mm. (Note that circle not continuous in some areas. Areas of misfit as low as beyond precision of industrial computed tomography scanner used.)
justified pairwise comparisons using the Student t tests (overall a=.05). RESULTS The means and 95% confidence limits for all measured gaps are shown in Figure 7. Data for the Ti and Zr were reported in a previous study.42 The ANOVA indicated no statistically significant effect of the gap (P.075), but did indicate a statistically significant interaction between the material and the porcelain layering (P<.001). The mean discrepancies for Ti, Ti-P, Zr, and Zr-P were 88, 71, 89, and 175 mm, respectively, regarding both gaps 3 and 4. Statistically significant differences were found between Zr and Zr-P and between Ti-P and Zr-P (P<.001), but no such difference was found between Ti and Ti-P (P=.768). DISCUSSION The null hypothesis that no difference would be found in 3D marginal discrepancies before and after porcelain
Yilmaz et al
layering was rejected for zirconia CAD-CAMefabricated frameworks; however, no statistical difference was detected between the discrepancies of Ti and Ti-P. The passive fit of an implant-supported structure has been defined as the state in which a nonfunctioning structure sitting on the implants does not exert any strain on its supporting base; thus, the implants are stress-free as if they are in their preloaded condition.11,48,49 The 1-screw test is commonly used to assess whether the passive fit has been achieved.25,26,31 The criterion for clinical acceptability of this test, particularly applicable for complete-arch frameworks, is based on tightening the most distal abutment screw without creating a marginal discrepancy at the abutment-framework interface on any of the remaining implants.43,50 The nature of the 1-screw test is that it relies only on naked-eye observations, making the evaluation of passive fit a matter of debate.25,26,50 Brånemark2 was the first to bring objectivity to the definition of the phenomenon, quantifying the level of discrepancy by suggesting it should not be more than 10 mm. Subsequently, Jemt31
THE JOURNAL OF PROSTHETIC DENTISTRY
6
Volume
3D Distance (µm)
300
200
100
0 Gap: Porcelain: Material:
3 4 3 4 Without With Titanium
3 4 3 4 Without With Zirconia
Figure 7. Three-dimensional marginal discrepancy mean values with confidence limits.
proposed that discrepancies of about 150 mm may be clinically acceptable. Absolute passive fit is thought to be impossible to achieve.11 While a clinically acceptable threshold of marginal misfit for tooth- or implant-supported FDPs has not yet been supported by scientific evidence,25 it has been frequently claimed to be less than 120 mm.27,51,52 However, others28,53 have claimed, based on their clinical observations, that the limit of marginal misfit may be up to 200 mm. The 3D marginal discrepancy mean values in Zr-P were less than 180 mm with around 95% of the measurements under 200 mm for gap 3 and 85% for gap 4. Further research is needed to establish the optimum limits of passive fit for implant-supported restorations. Katsoulis et al21 investigated the passive fit of 10-unit CAD-CAM titanium frameworks on 6 implants with the 1-screw test. By scanning electron microscope observation, they found mean vertical discrepancy values between 17 and 24 mm on the implants most distant from the terminal screw-retained implant, which had been placed at the maxillary right canine and second premolar, corresponding to locations at gap 3 and gap 4 in the present study. Another study by Katsoulis et al25 using the same model revealed mean discrepancy values of 21 to 30 mm at the same locations for complete-arch CADCAMefabricated titanium frameworks. The maximum range of vertical discrepancy measured in these studies21,25 varied up to 49 and 83 mm considering all 5 implants without screws in place, except for 1. The results of Ti in the present study showed lower precision of fit compared with those studies, but still comparable with the clinically acceptable fit of less than 120 mm. The layering process had no significant influence on the passive fit of the control (Ti) group in the current THE JOURNAL OF PROSTHETIC DENTISTRY
-
Issue
-
study (P=.768). The insignificant effect of porcelain layering on complete-arch implant-supported CADCAM titanium frameworks is supported by the results of other studies.25,32 The maximum range of discrepancy of the complete-arch layered titanium frameworks measured at the implant level for passive fit has been reported to be between 38 and 62 mm.22,25 This discrepancy is lower than the Ti-P values in the current study. Nevertheless, the maximum range of all these studies is within clinically acceptable limits (120 mm). The effect of layering on the marginal fit of CADCAMefabricated complete-arch implant-supported, screw-retained FDPs with presintered zirconia framework was significant according to the results of this study. Katsoulis et al21 have investigated the passive fit of complete-arch implant-supported frameworks made of presintered zirconia on 6 implants by using the 1-screw test. The implant locations in that study were similar to those used in the current study. The mean vertical discrepancies in that study for the zirconia frameworks fabricated through 3D laser scanning and CAD-CAM, as in the current study, were reported to be 48 mm (maximum range: 93 mm) and 77 mm (maximum range: 142 mm) for the maxillary right canine and second premolar. The 3D marginal discrepancy means values for gap 3 and gap 4 obtained in the current study were 84 mm (maximum range: 104 mm) and 94 mm (maximum range: 133 mm). The results of both the current and Katsoulis et al21 studies are similar for zirconia frameworks before the layering process. The 3D marginal discrepancy mean values for all groups in this study were within the clinically acceptable threshold of 120 mm, except for group Zr-P (175 mm). Pak et al40 investigated the effect of porcelain layering on the marginal adaptation of presintered and postsintered zirconia crowns and reported that porcelain layering decreased marginal adaptation. Torabi et al41 reported that presintered zirconia crowns subjected to various veneering techniques, each involving repeated firing, significantly altered the marginal fit. However, none of the prostheses in those studies showed the large increase in mean marginal discrepancy values seen in the present study. This may be attributed to the larger volume of the prostheses in this study compared with that in previous studies. Reports further suggest that sintering alone may initiate distortion of the framework of long-span presintered zirconia prostheses.34,35 Further research is needed to improve knowledge on this subject. The expanded measurement uncertainty (11+30L mm) in this study should be considered in interpreting the results. If it was assumed by a rough computation that the L value was 0.001 m (1 mm), which is an overestimated value for 3D marginal discrepancy that might have been detected in the current study, then the expanded measurement uncertainty would be around Yilmaz et al
-
2017
11 mm, and that would be the maximum value. It was assumed that because gap 2 was closest to the tightened screw during the 1-screw test, the 3D marginal discrepancy mean values of gap 2 would potentially be lower than for gap 3 and gap 4. This would be consistent with the published literature, as similar results have been reported by previous studies.21,25 Therefore, only gaps that crossed the midline and were farthest from the test screw (gap 3 and gap 4) were considered when the discrepancy was measured. A limitation of the current study was the use of an indirect measurement technique; virtual assessment based on mathematically calculated values by means of software. An advantage of this analytic approach is 3D evaluation in different planes and dimensions of digitally superimposed scanned data. However, procedures like scanning and data transfer to generate STL virtual models may also present with errors, which should be considered when interpreting results.21,29 In addition, the frameworks were fabricated on a master model from a completely seated resin prototype. Therefore, the transfer of the implant positions from the clinical situation to the master model was not tested primarily to focus on the effect of the fabrication stages (CAM milling and layering) on the marginal fit. Both conventional and digital clinical transfer procedures of the implant positions to the master cast may also present with some inaccuracies and contribute to the final marginal discrepancy. Also, only 1 site (implant at maxillary right molar site) was used to secure the screw for the 1-screw test used in this study. The fit of the framework may differ when 1 screw is used in different implant sites to evaluate the fit discrepancy at other implant sites. Future studies should secure the screw at different sites to measure the discrepancies at the nonsecured interfaces. The results of this study should be interpreted considering that only 1 CAD-CAM system was used with its milling machine and blocks. Different systems may perform differently. CONCLUSIONS Within the limitations of this in vitro study, the following conclusions were drawn: 1. Absolute passive fit was not achieved at any stage of fabrication for the CAD-CAMefabricated completearch implant-supported, screw-retained FDPs with presintered zirconia or titanium frameworks. 2. Porcelain layering had an insignificant effect on the 3D marginal integrity of CAD-CAMefabricated titanium complete-arch implant-supported, screwretained FDP frameworks; however, the effect of porcelain layering on the marginal fit of partially sintered zirconia frameworks was significant. 3. Three-dimensional mean marginal discrepancy values for all groups were within the clinically Yilmaz et al
7
acceptable limits (<120 mm) except for the porcelainlayered zirconia frameworks. REFERENCES 1. Brånemark PI, Hansson BO, Adell R, Breine U, Lindström J, Hallén O, et al. Osseointegrated implants in the treatment of the edentulous jaw. Experience from a 10-year period. Scand J Plast Reconstr Surg Suppl 1977;16:1-132. 2. Brånemark PI. Osseointegration and its experimental back ground. J Prosthet Dent 1983;50:399-410. 3. Babbush CA, Kanawati A, Kotsakis GA, Hinrichs JE. Patient-related and financial outcomes analysis of conventional full-arch rehabilitation versus the All-on-4 concept: A cohort study. Implant Dent 2014;23:218-24. 4. Skalak R. Biomechanical considerations in osseointegrated prostheses. J Prosthet Dent 1983;49:843-8. 5. Guichet DL, Yoshinobu D, Caputo AA. Effect of splinting and interproximal contact tightness on load transfer by implant restorations. J Prosthet Dent 2002;87:528-35. 6. Clelland NL, Seidt JD, Daroz LG, McGlumphy EA. Comparison of strains for splinted and nonsplinted implant prostheses using three-dimensional image correlation. Int J Oral Maxillofac Implants 2010;25:953-9. 7. Bergkvist G, Simonsson K, Rydberg K, Johansson F, Dérand T. A finite element analysis of stress distribution in bone tissue surrounding uncoupled or splinted dental implants. Clin Implant Dent Relat Res 2008;10:40-6. 8. Wang TM, Leu LJ, Wang J, Lin LD. Effects of prosthesis materials and prosthesis splinting on peri-implant bone stress around implants in poorquality bone: A numeric analysis. Int J Oral Maxillofac Implants 2002;17: 231-7. 9. Shigemitsu R, Ogawa T, Matsumoto T, Yoda N, Gunji Y, Yamakawa Y, et al. Stress distribution in the peri-implant bone with splinted and non-splinted implants by in vivo loading data-based finite element analysis. Odontology 2013;101:222-6. 10. Jivraj S, Chee W. Treatment planning of implants in posterior quadrants. Br Dent J 2006;201:13-23. 11. Sahin S, Cehreli MC. The significance of passive framework fit in implant prosthodontics: current status. Implant Dent 2001;10:85-92. 12. Jokstad A, Shokati B. New 3D technologies applied to assess the long-term clinical effects of misfit of the full jaw fixed prosthesis on dental implants. Clin Oral Implants Res 2015;26:1129-34. 13. Yannikakis S, Prombonas A. Improving the fit of implant prosthetics: An in vitro study. Int J Oral Maxillofac Implants 2013;28:126-34. 14. Gunne J, Jemt T, Lindén B. Implant treatment in partially edentulous patients: a report on prostheses after 3 years. Int J Prosthodont 1994;7: 143-8. 15. Kreissl ME, Gerds T, Muche R, Heydecke G, Strub JR. Technical complications of implant-supported fixed partial dentures in partially edentulous cases after an average observation period of 5 years. Clin Oral Implants Res 2007;18:720-6. 16. Scarano A, Assenza B, Piattelli M, Iezzi G, Leghissa GC, Quaranta A, et al. A 16-year study of the microgap between 272 human titanium implants and their abutments. J Oral Implantol 2005;31:269-75. 17. de França DG, Morais MH, das Neves FD, Barbosa GA. Influence of CAD/ CAM on the fit accuracy of implant-supported zirconia and cobalt-chromium fixed dental prostheses. J Prosthet Dent 2015;113:22-8. 18. Kunavisarut C, Lang LA, Stoner BR, Felton DA. Finite element analysis on dental implant-supported prostheses without passive fit. J Prosthodont 2002;11:30-40. 19. Abduo J, Judge RB. Implications of implant framework misfit: A systematic review of biomechanical sequelae. Int J Oral Maxillofac Implants 2014;29: 608-21. 20. Venezia P, Torsello F, Cavalcanti R, D’Amato S. Retrospective analysis of 26 complete-arch implant-supported monolithic zirconia prostheses with feldspathic porcelain veneering limited to the facial surface. J Prosthet Dent 2015;114:506-12. 21. Katsoulis J, Mericske-Stern R, Rotkina L, Zbӓren C, Enkling N, Blatz MB. Precision of fit of implant-supported screw retained 10-unit computer-aideddesigned and computer-aided- manufactured frameworks made from zirconium dioxide and titanium: An in vitro study. Clin Oral Implants Res 2014;25:165-74. 22. Katsoulis J, Müller P, Mericske-Stern R, Blatz MB. CAD/CAM fabrication accuracy of long- vs. short-span implant supported FDPs. Clin Oral Implants Res 2015;26:245-9. 23. Takahashi T, Gunne J. Fit of implant frameworks: An in vitro comparison between two fabrication techniques. J Prosthet Dent 2003;89:256-60. 24. Berejuk HM, Shimizu RH, de Mattias Sartori IA, Valgas L, Tiossi R. Vertical microgap and passivity of fit of three-unit implant-supported frameworks fabricated using different techniques. Int J Oral Maxillofac Implants 2014;29: 1064-70.
THE JOURNAL OF PROSTHETIC DENTISTRY
8
25. Katsoulis J, Mericske-Stern R, Enkling N, Katsoulis K, Blatz MB. In vitro precision of fit of computer-aided designed and computer-aided manufactured titanium screw-retained fixed dental prostheses before and after ceramic veneering. Clin Oral Implants Res 2015;26:44-9. 26. Abduo J, Bennani V, Waddell N, Lyons K, Swain M. Assessing the fit of implant fixed prostheses: A critical review. Int J Oral Maxillofac Implants 2010;25:506-15. 27. Karatas¸li O, Kurso glu P, Capa N, Kazazo g lu E. Comparison of the marginal fit of different coping materials and designs produced by computer aided manufacturing systems. Dent Mater J 2011;30:97-102. 28. Reich S, Wichmann M, Nkenke E, Proeschel P. Clinical fit of all-ceramic three-unit fixed partial dentures, generated with three different CAD/CAM systems. Eur J Oral Sci 2005;113:174-9. 29. Hjalmarsson L, Ortorp A, Smedberg JI, Jemt T. Precision of fit to implants: A comparison of Cresco and Procera implant bridge frameworks. Clin Implant Dent Relat Res 2010;12:271-80. 30. Paniz G, Stellini E, Meneghello R, Cerardi A, Gobbato EA, Bressan E. The precision of fit of cast and milled full-arch implant-supported restorations. Int J Oral Maxillofac Implants 2013;28:687-93. 31. Jemt T. Failures and complications in 391 consecutively inserted fixed prostheses supported by Brånemark implants in edentulous jaws: A study of treatment from the time of prosthesis placement to the first annual checkup. Int J Oral Maxillofac Implants 1991;6:270-6. 32. Ortorp A, Jemt T, Bäck T, Jälevik T. Comparisons of precision of fit between cast and CNC-milled titanium implant frameworks for the edentulous mandible. Int J Prosthodont 2003;16:194-200. 33. Abduo J. Fit of CAD/CAM implant frameworks: A comprehensive review. J Oral Implantol 2014;40:758-66. 34. Beuer F, Neumeier P, Naumann M. Marginal fit of 14-unit zirconia fixed dental prosthesis retainers. J Oral Rehabil 2009;36:142-9. 35. Sachs C, Groesser J, Stadelmann M, Schweiger J, Erdelt K, Beuer F. Full-arch prostheses from translucent zirconia: Accuracy of fit. Dent Mater 2014;30:817-23. 36. Kale E, Seker E, Yilmaz B, Özcelik TB. Effect of cement space on the marginal fit of CAD/CAM-fabricated monolithic zirconia crowns. J Prosthet Dent 2016;116:890-5. 37. Kale E, Yilmaz B, Seker E, Özcelik TB. Effect of fabrication stages and cementation on the marginal fit of CAD/CAM monolithic zirconia crowns. J Prosthet Dent 2017;118:736-41. 38. Abduo J, Lyons K, Swain M. Fit of zirconia fixed partial denture: A systematic review. J Oral Rehabil 2010;37:866-76. 39. Kohorst P, Brinkmann H, Dittmer MP, Borchers L, Stiesch M. Influence of the veneering process on the marginal fit of zirconia fixed dental prostheses. J Oral Rehabil 2010;37:283-91. 40. Pak HS, Han JS, Lee JB, Kim SH, Yang JH. Influence of porcelain veneering on the marginal fit of Digident and Lava CAD/CAM zirconia ceramic crowns. J Adv Prosthodont 2010;2:33-8. 41. Torabi K, Vojdani M, Giti R, Taghva M, Pardis S. The effect of various veneering techniques on the marginal fit of zirconia copings. J Adv Prosthodont 2015;7:233-9. 42. Al-Meraikhi H, Yilmaz B, McGlumphy EA, Brantley WA, Johnston WM. In vitro fit of CAD-CAM complete arch screw-retained
THE JOURNAL OF PROSTHETIC DENTISTRY
Volume
43. 44. 45.
46. 47.
48. 49. 50. 51. 52. 53.
-
Issue
-
titanium and zirconia implant prostheses fabricated on 4 implants. J Prosthet Dent July 2017;15. doi: 10.1016/j.prosdent.2017.04.023. [Epub ahead of print.] Eisenmann E, Mokabberi A, Walter MH, Freesmeyer WB. Improving the fit of implant-supported superstructures using the spark erosion technique. Int J Oral Maxillofac Implants 2004;19:810-8. White GE. Osseointegrated dental technology. London: Quintessence; 1993. p. 61,123-124,129. Al-Meraikhi H, Yilmaz B, McGlumphy EA, Brantley WA, Johnston WM. Distortion of CAD/CAM-fabricated implant-fixed titanium and zirconia complete dental prosthesis frameworks. J Prosthet Dent 3 May 2017. doi: 10.1016/j.prosdent.2017.02.003. [Epub ahead of print.] Figliola RS, Beasley DE. Dimensional measurements: Metrology. In: Figliola RS, editor. Theory and design for mechanical measurements. New York: Wiley; 1991. p. 417-25. International Organization for Standardization. ISO/IEC 17025. General requirements for the competence of testing and calibration laboratories. Geneva: International Organization for Standardization; 2005. Available at: http://www.iso.org/webstore.htm. Watanabe F, Uno I, Hata Y, Neuendorff G, Kirsch A. Analysis of stress distribution in a screw-retained implant prosthesis. Int J Oral Maxillofac Implants 2000;15:209-18. Karl M, Rosch S, Graef F, Taylor TD, Heckmann SM. Strain situation after fixation of three-unit ceramic veneered implant superstructures. Implant Dent 2005;14:157-65. Tan KB, Rubenstein JE, Nicholls JI, Yuodelis RA. Three-dimensional analysis of the casting accuracy of one-piece, osseointegrated implant-retained prostheses. Int J Prosthodont 1993;6:346-63. McLean JW, von Fraunhofer JA. The estimation of cement film thickness by an in vivo technique. Br Dent J 1971;131:107-11. Sorensen JA. A standardized method for determination of crown margin fidelity. J Prosthet Dent 1990;64:18-24. Wolfart S, Wegner SM, Al-Halabi A, Kern M. Clinical evaluation of marginal fit of a new experimental all-ceramic system before and after cementation. Int J Prosthodont 2003;16:587-92.
Corresponding author: Dr Ediz Kale Mustafa Kemal University Faculty of Dentistry, Department of Prosthodontics 31060 Antakya-Hatay TURKEY Email: [email protected] Acknowledgments The authors thank Dr Hadi Al-Meraikhi for his collaboration. Copyright © 2017 by the Editorial Council for The Journal of Prosthetic Dentistry.
Yilmaz et al