The International Journal of Prosthodontics, 01/2004

Purpose: The purpose of this study was to determine if the Procera pressed-powder method can be used to fabricate titanium copings. Materials and Methods: Commerciallypure titanium powder was used to prepare the copings. The powder was pressed onto an enlarged tooth preparation die of aluminum using cold isostatic pressing. The outer shape of the coping was formed using a Procera milling machine, and the copings were vacuum sintered. Results: Titanium copings could be prepared using this method. The density of the sintered copings reached 97% to 99%+ of theoretic density, and the copings show edductile behavior after sintering. Enlarging the tooth preparation die to compensate for the sintering shrinkage could optimize the final size of the copings. Conclusion: Ductile and dense titanium dental copings can be produced with powder-metal processing using coldisostatic pressing, followed by milling and sintering to final shape. The forming technique has, if properly optimized, a potential of becoming a more cost-efficient production method than spark erosion.

Purpose: The aim of this study was to evaluate the clinical performance of a ceromer (Targis) in indirect inlay restorations. Materials and Methods: Ninty-nine Targis inlays (37premolars, 62 molars) were placed in 51 patients (mean age 27 years). Twenty-nine percent of the restorations were placed in patients with parafunctional habits such as bruxism or clenching. All restorations were in occlusion and were placed using Variolink (43 Variolink Ultra, 56 Variolink II high viscosity) in combination with the Syntac Classic adhesive system under rubber dam isolation. The restorations were evaluated according to modified USPHS criteria at baseline and for a recall period of 6 to 53 months after insertion. Results: There were two clinically unacceptable failures in total. Fracture was registered in one molar at 38months, and one molar needed endodontic treatment 7 months after insertion. Based on Kaplan-Meier statistical analysis, the estimated survival rate of the inlays was 97.9% (97.7%for Variolink Ultra, 98.2% for Variolink II high viscosity). It was apparent that deterioration occurred in the surface texture of the inlays, since a slightly pitted surface was observed in29% of the inlays at recall examinations. Conclusion: In this in vivo study, Targis inlaysluted with both resin luting agents functioned satisfactorily, with a relatively low fracturerate over a mean evaluation period of 28 months.

Purpose: The purposes of this study were to: (1) investigate the correlation between thecolor difference of bilayer porcelain veneers over white and black backgrounds (ΔE1) andtheir opacity (contrast ratios); (2) determine whether there is a recommendable thresholdcontrast ratio above which the color difference is clinically acceptable (when ΔE = 5); and (3) compare the ability of porcelain veneers to mask a color change from white to blackbackgrounds (ΔE1) and their ability to mask a color change from white to clinicallydiscolored teeth (ΔE2). Materials and Methods: Forty-four maxillary anterior teeth of eightpatients with severe tetracycline discoloration were prepared for bilayer porcelain veneersin shade A2 porcelain. The cores were 0.25 mm thick. The color (CIE L*a*b*) and reflectance (Y) of the midbuccal region of each veneer were measured over white and blackbackgrounds using a colorimeter under artificial daylight. The veneers were bonded todiscolored teeth, and their color was measured after 1 week. Results: The mean colordifference ΔE1 was 10.6 (SD 2.6). The mean contrast ratio was 0.75 (SD 0.1). There was a close and statistically significant correlation between ΔE1 and contrast ratio. The determined threshold contrast ratio was 0.91. The mean color difference ΔE2 was 11.6 (SD5.5). A paired ttest showed no difference between ΔE1 and ΔE2. Conclusion: There was a significant correlation between the masking ability of veneers (ΔE1) and their opacity(contrast ratio). There was no significant difference in the ability of the porcelain veneers inmasking a color change from white to black backgrounds compared to their ability to maskthe color change from white to the discolored teeth.

Purpose: This study evaluated outcome and quality of treatments with telescopic crown-retained dentures. Materials and Methods: A total of 72 subjects (27 men and 45women; mean age 67 years) wearing 75 telescopic crown-retained dentures (18 in the mandible and 57 in the maxilla) participated in the study. There were a total of 368abutment teeth, 272 in the maxilla and 96 in the mandible. Each patient was clinically examined. Using the CDA evaluation system, four calibrated evaluators also examined,independently, the inner crowns for margin integrity and the superstructure for retention,occlusion, stability, wear, and esthetic appearance. Observer consistency was measured with Cohen's κ. Results: The observation period varied from 9 months to 9.3 years (mean3.8 years). One telescopic crown-retained denture was lost, and 24 abutment teeth (7%) were extracted during the observation period. In 49 abutment teeth (13%), technical complications had occurred, and a total of four framework fractures (5%) were observed.Based on the CDA criteria, most of the characteristics were evaluated as satisfactory. The characteristics "condition of denture-supporting soft tissue" and "superstructure wear"showed the highest frequencies of not acceptable ratings, 44% and 45%, respectively. Conclusion: In this retrospective follow-up study, satisfactory outcome was found for tooth supported telescopic crown-retained dentures over a mean observation period of 3.8 years.

Purpose: The purpose of this study was to evaluate the clinical performance of In-Ceram Zirconia posterior fixed partial dentures (FPD) after 3 years in service. Materials and Methods: Eighteen In-Ceram Zirconia FPDs were fabricated in 16 patients. The FPDs were placed between January and April 1999. The CDA quality evaluation system was used for assessment of surface and color, anatomic form, and marginal integrity. Bleedingon probing was also recorded. Results: One of the 18 posterior FPDs was lost because ofa root fracture. All remaining FPDs were rated as either excellent or acceptable after the observation period. Bleeding was more often recorded at crowned abutments with In-Ceram Zirconia than at contralateral teeth. Conclusion: In-Ceram Zirconia posterior FPDs seem to be an acceptable treatment alternative in a 3-year perspective. However, more clinical long-term follow-up studies must be performed before the system can be recommended as an alternative to conventional FPDs.

Purpose: This study investigated whether tooth wear status can predict bruxism level. Materials and Methods: Sixteen Japanese subjects (eight bruxers and eight age- and gender-matched controls; mean age 30 years) participated in this study. From dentalcasts of these subjects, the tooth wear was scored by Murphy's method. Bruxism level inthese subjects was also recorded for 5 consecutive nights in the subject's home environment using a force-based bruxism detecting system. The relationship between the tooth wear score and bruxism data was evaluated statistically. Results: Correlation analysis between the Murphy's scores of maxillary and mandibular dental arch and bruxism event duration score revealed no significant relationship between tooth wear and current bruxism. Conclusion: Tooth wear status is not predictive of ongoing bruxism level as measured by the force-based bruxism detection system in 30-year-old Japanese subjects.

Purpose: The present study was designed to determine the cytotoxic effects of some widely used dental base-metal casting alloys (Ni-Cr and Co-Cr) on the cytoskeleton in cultured human fibroblasts, and to evaluate whether any structural alteration is associated with the application of these alloys. Materials and Methods: Ten specimens from six different alloys were prepared as 5-mm disks. Five of ten samples from each group were polished; the remaining five samples were left sandblasted with 50-µm Al2O3. All samples were directly exposed to human fibroblasts in a 24-well cell culture dish for 120 hours. Then, cells were fixed and stained with antibodies against major cytoskeletal elements-actin, vimentin, and microtubules-by immunofluorescent staining methods. Cells were analyzed in 3-D to document the cytoskeletal alterations using a laser confocal microscope. Results:Disintegration of actin filaments was observed in lamellipodia of fibroblasts by the effect of both polished and sandblasted Ni-Cr and Co-Cr samples, with the exception of the polished Co-Cr alloy (Wirocast). Moreover, intracytoplasmic actin-decorated stress fibers were found bent and occasionally tangled in the sandblasted Ni-Cr (Wiron 99) and Co-Cr alloys (Wirocast and Co-Cr Degussa). Vimentin, a mesenchymal cell intermediate filament protein normally showing an intracellular meshwork pattern, was not affected by any of the polished or sandblasted alloys. Microtubules mainly remained intact in all dentalalloy-treated groups. Conclusion: Taken together, it is possible to postulate that Ni-Cr andCo-Cr dental alloys, especially sandblasted forms, may have detrimental effects on the actin-based cytoskeleton, at least tested in vitro.

Purpose: This retrospective study documented the 5-year cumulative survival rate (CSR) of 5-mm-diameter wide-bodied implants in posterior jaws as related to identified risk factors and relative host bone site dimensions. Materials and Methods: Sixty-four wide-bodied implants placed consecutively in the posterior jaws of 43 patients were matched using several identified risk factors with 64 regular-diameter implants (3.75-mm or 4-mm diameter) placed in the posterior jaws of 25 of the same patients and 14 others. Life table analyses were undertaken to examine the difference in CSR between the groups. Multivariate Cox regression was conducted to assess the relationship between potential risk factors and overall CSR. Results: Ten of the wide-bodied implants failed (CSR 80.9%), while two of the regular-diameter implants failed (CSR 96.8%). The difference between the groups was statistically significant. Multivariate analysis demonstrated a significant predictive relationship between overall CSR and the ratio of implant volume to remaining bone volume. This suggests that relative determinants of critical bone volume to implant dimensions may need to be considered when planning implant surgery. Conclusion: Wide-bodied implants placed in the posterior jaw can suffer a significantly elevated risk of implant failure compared to regular-diameter implants. This susceptibility may relate to either implant design or the relative relationship of implant to host bone dimensions.

Purpose: The aim of this study was to determine in vitro the internal and marginal fit of zirconium dioxide ceramic copings manufactured using a recently introduced CAD/CAM based technique (Denzir). Materials and Methods: Two master models were produced in metal, representing the maxillary right central incisor and first premolar. Two A-silicone impressions were used for each of the master models, and from each of the impressions five stone dies with the corresponding ceramic copings were produced, for a total of 20copings. The A-silicone replica of the misfit of the ceramic coping to the corresponding stone die and master model was sectioned buccolingually and mesiodistally. The obtained sections were measured at occlusal, axial, and marginal locations under lightmicroscopy. Twenty-four measurements for each replica were made. The Student's test was used to detect significant differences between coping-stone die and coping-mastermodel misfits. Results: For any combination, the marginal fit was superior to the axial and occlusal fit. In general, the misfit between the coping and the stone die did not differ significantly from the misfit detected between the coping and the master model. However, a better fit was recorded for the first premolar at the occlusal portion in the coping-stone die combination compared to the coping-master model combination. The mean marginal discrepancy between the copings and master models was clearly below50 µm, with a range of 0 to 115 µm. Conclusion: The accuracy achieved by the Denzir manufacturing process for the production of zirconium dioxide copings is well within the range of clinical acceptability.

Purpose: This study compared the effects of an antimicrobial agent (Asepto-Sol) on the physical properties of types III, IV, and V gypsum casts made from two types of impression materials. Materials and Methods: Selected physical properties of five gypsum-based dental stones (Prima-Rock, Ortho Stone, New Fujirock, Die-Keen, Microstone) and two resin-based dental stones (Resin-Rock, Instone) were evaluated using an addition silicone impression material (Reprosil) and an irreversible hydrocolloid (Jeltrate Plus). In group 1, Asepto-Solsolution replaced water as the gauging liquid for the seven dental stones. The mixed gypsum was poured directly onto impressions of two master dies using two impression materials. In group 2, impressions made with both impression materials were sprayed with the Asepto-Sol solution, left for 10 minutes, rinsed for 30 seconds with tap water, and poured with each dental stone mixed with deionized water. In group 3 (control), the gypsums were mixed with deionized water and the mixed stone was poured directly into impressions, with no exposure to Asepto-Sol. The physical properties evaluated for the gypsum specimens were linear dimensional change, detail reproduction, Knoop hardness,and transverse strength. Results: The linear dimensional stability, detail reproduction, and transverse strength tests were relatively unaffected by the use of Asepto-Sol, with few exceptions. Detail reproduction appeared to be least affected by Asepto-Sol, and changes in Knoop hardness were noted but results differed among the seven dental stones. However, New Fujirock was not ideally matched with Jeltrate Plus, and no stone specimens could be produced. Conclusion: Whether mixed with the gypsum powder or sprayed on impressions, Asepto-Sol solution did not adversely affect the physical properties of the dental stones tested.

Purpose: This study observed occlusal contacts and determined their areas on the mandibular teeth, especially the molars, during voluntary lateral excursions. Materials and Methods: Occlusal contact areas were estimated with a measurement system combining 3-D tracking of mandibular movements with 3-D digitization of tooth shape. Sixteen women with sound permanent dentitions participated. Results: At the intercuspal position, estimated occlusal contact areas of the first and second mandibular molars were on average 12.6 mm2 and 9.0 mm2, respectively. However, after 3.0 mm of lateral excursion, their areas were sharply reduced to 2.2 mm2 and 1.5 mm2 on the working side, and 0.4 mm2 and 1.1 mm2 on the nonworking side, respectively. Conclusion: These results suggest that the occlusal contact areas on working- and nonworking-side molars differ from each other as lateral excursion proceeds.

Purpose: This laboratory study compared the effect of different surface treatments of amedium-gold, high-noble alloy on the shear bond strength of an indirect, highly filled resincomposite to the alloy and on the elemental composition of the alloy surface. Materials and Methods: Ninety disks, cast in a medium-gold, high-noble porcelain-fused-to-metal alloy (VDeltaloy), received three different surface treatments: sandblasting with 50-µm Al2O3 (group1) or 250-µm Al2O3 (group 2) and chemical agents, or with 250-µm Al2O3 without chemicalagents (group 3) prior to bonding of an indirect resin composite (Artglass, and chemicalagents Siloc-pre and Siloc-bond). The specimens were tested in shear, half of them after 24-hour dry storage at room temperature and the rest after 10-day storage in normal saline solution at 37°C and thermocycling (2,500 cycles between 5 and 55°C). Morphologic and qualitative changes on the alloy surface after sandblasting with 50- or 250-µm Al2O3 weree xamined by SEM using EDS analysis and compared with polished specimens. Statistical analysis was performed using two-factor ANOVA. Results: The mean shear bond strengths (in MPa) after dry or wet storage and thermocycling were 29 and 24 for group 1, 21 and 18for group 2, and 17 and 12 for group 3, respectively; there was a statistically significant difference among the groups. Sandblasting of the alloy surface led to statistically significant changes in elemental composition. These changes were of greater magnitude when 50-µmAl2O3 particles were used. Conclusion: The particle size used for sandblasting influences the shear bond strength between a high-noble alloy and a highly filled indirect resin composite,as well as the elemental composition of the alloy surface.

Purpose: This study systematically searched the dental literature to identify and classify articles on the influence of prosthodontic and dental implant treatment on patient satisfaction and oral health-related quality of life according to their level of evidence. Materials and Methods: A literature search was carried out for articles published between1960 and February 2003 using an electronic key word search complemented by hand searching. The retrieved articles were subjected to inclusion and exclusion criteria. Only experimental studies were included; articles that did not focus on the effect of therapy on the patient were excluded from further processing. The levels of evidence of the articles were classified following the guidelines of the US Agency for Health Care Policy and Research. Results: A total of 207 publications were identified, of which 114 reports investigating 24,863 patients met the inclusion criteria. Data from the studies were analyzed using SPSS 9.0. Two thirds of the publications showed a low evidence level of III; most were conducted in patients who were edentulous or restored with complete dentures (59% of all studies). Mostly, nonstandardized, custom-made questionnaires(80%) were used. On average, 9 (SD 4.2) outcome variables were used within each trial,but clinical criteria were more often used than psychosocial criteria. The most frequently used questions concerned "chewing function" (86%), esthetics (77%), speech (68%), and general satisfaction (67%). Validated instruments, such as the Oral Health Impact Profile,were increasingly used in recent studies, which were also methodically more sufficient. Conclusion: Few studies with high levels of evidence were found. Research in this field is still in a phase of development.

Purpose: The aim of the present study was to compare the fracture resistance ofendodontically treated maxillary premolars with mesio-occlusodistal (MOD) cavities restored using various restorative materials and luting agents. Materials and Methods: Eighty extracted human maxillary premolars satisfying certain predetermined criteria were subjected to seven different restoration methods (10 premolars per method). After endodontic treatment, an MOD cavity was prepared in each specimen, and restoration was carried out by one of the following methods: group 1 = control (intact premolars); groups 2and 3 = restoration using a photo-cure resin composite with and without bonding,respectively; groups 4 and 5 = restoration using a cast-metal inlay with zinc phosphate and adhesive resin cements, respectively; groups 6 and 7 = restoration using a cast-metal onlay with zinc phosphate and adhesive resin cements, respectively; and group 8 = restoration using a hybrid resin onlay. A fracture test was conducted to determine the fracture resistance and fracture mode of each specimen. Results: Fracture resistance was greatest for teeth restored using a cast-metal onlay cemented with adhesive resin cement, but those fractures that did occur were generally unrestorable. Fracture resistance of teeth restored using a cast-metal inlay was also high. Fracture resistance for teeth restored using a resincomposite was significantly lower, but the majority of these fractures were restorable. Conclusion: Endodontically treated maxillary premolars with MOD cavities could be successfully restored by cast onlay and inlay restorations luted with adhesive resin cement,but their failure mode was often unfavorable.