The International Journal of Prosthodontics, 06/2003

Purpose: The purpose of this in vivo study was to evaluate the marginal fit of inlay and crown abutments for fixed partial dentures (FPD) made from a new all-ceramic material. Materials and Methods: Sixteen patients were selected for the study. After abutment preparation, impressions were made and master dies were fabricated. FPDs were made with the experimental heat-pressed lithium-disilicate glass-ceramic following the manufacturer's recommendations. At random, one abutment of each FPD was chosen for evaluation (11 crown and 8 inlay abutments). Impressions of the restoration margins were taken before and after adhesive cementation. Replicas of the abutment margins were investigated by SEM. The marginal discrepancies were evaluated in sections of 200 µm. The highest value of each section was applied, and the mean of all sections of each replica was used for statistical analysis. Results: The median of the marginal discrepancies before cementation was 96 µm for crowns and 89 µm for inlays. After adhesive cementation, the median increased for crowns to 130 µm and for inlays to 92 µm, a significant increase in the marginal discrepancies caused by cementation for crowns, but not for inlays. There were no significant differences between the discrepancies of crowns and inlays before or after cementation. Conclusion: The maximum marginal discrepancies found in this study were between 50 and 265 µm before cementation and between 70 and 285 µm after cementation, with no significant differences between the means for crowns and inlays. Adhesive cementation caused a significant increase of the marginal discrepancies for crown, but not inlay, abutments.

Purpose: This study prospectively evaluated the clinical performance of three types of translucent posts over a follow-up period of between 2 and 3 years. Materials and Methods: Selected were 225 patients with one premolar in need of endodontic treatment, followed by restoration with a fiber post and porcelain crown. The sample was randomly divided into three groups of 75 patients each. The same type of post was used in all patients within a group: group 1 = Aesthetic Plus; group 2 = DT; and group 3 = FRC Postec. For bonding the post, a light-curing adhesive (One-Step) and a dual-curing resin cement (Duo-Link) were applied in group 1 and 2 roots, whereas self-curing materials (Excite DSC as adhesive and MultiLink as resin cement) were used in group 3. After 6, 12, and 24 months, patients were recalled, and a clinical and radiographic examination was performed. For some patients, 30-month follow-up data were also collected. Results: Debonding of the post occurrred in eight cases (3.5%); in another six cases, a recurrence of the periapical lesion was reported. Conclusion: The statistical analysis did not reveal any significant difference in the survival rate of the tested posts, suggesting that all are equally and sufficiently reliable for clinical use.

Purpose: This study investigated the cytotoxicity of various types of dental casting alloys after they had been conditioned in distilled water. Materials and Methods: The casting alloys investigated included one high-noble alloy (Bioherador N) and six base-metal alloys, including four Ni-Cr alloys (Remanium CS, Heranium NA, Wiron 99, CB Soft), one Co-Cr alloy (Wirobond C), and one Cu-based alloy (Thermobond). Ten disks from each alloy were conditioned in distilled water at 37°C for either 72 or 168 hours. The cytotoxicity of the alloys was then tested on Balb/C 3T3 fibroblasts, which were exposed to the alloys for 3 days at 37°C. Cell viability was determined by the MTT method. The data were analyzed by ANOVA, and follow-up comparison between the groups was carried out using Tukey and ttests. Results: ANOVA revealed a significant effect of alloy type and conditioning time ( P .001). Bioherador N was significantly less toxic than all the other alloys in the 72-hour conditioned group. After 168 hours of conditioning, its cytotoxicity was not different ( P> .05) from that of Remanium CS, Wiron 99, and Wirobond C. Thermobond and CB Soft were significantly more toxic than the other alloys at both conditioning times. Conclusion: Conditioning of base-metal alloys, other than those containing Cu, for 168 hours in distilled water makes their cytotoxicity levels comparable to that of the high-noble alloy.

Purpose: This prospective investigation studied the clinical and radiographic performance of mandibular fixed prostheses supported by osseointegrated implants over more than 20 years. Materials and Methods: A total of 273 standard Brånemark implants (10 mm long) were placed in 47 patients between 1978 and 1982. Clinical and radiographic data collected at several examinations over the 20-year observation period have been reported previously. This study presents the outcome of the latest follow-up after 20 to 23 years. Results: Thirty patients (64%; 75% of those still alive) attended the 20-year follow-up examination. Three implants were lost during the entire observation period, and the 20-year implant cumulative survival rate was 98.9%. All patients had continuous prosthesis function, but two had their mandibular prostheses remade during the 20 years. No implants or prostheses were lost or fractured during the last 5 years, and only a few prosthodontic complications were noted. The mean bone level was 1.6 mm (SD 0.90) below the reference point after 20 years, and mean bone loss was 0.2 mm (SD 0.22) between the 15- and 20-year follow-ups. Thirtyseven implants (24%) showed more than two exposed threads at the 15-year follow-up examination, but only four implants (3%) presented pain and/or bone loss exceeding one thread (0.6 mm) during the last 5 years. Conclusion: The successful treatment result after 15 years continued up to more than 20 years in function. During the last 5 years, a majority of the implants with several exposed implant threads could be maintained without any complications, and the frequency of implants showing signs of ongoing peri-implantitis was less than 3%.

Purpose: This study compared the chewing difficulty of foods in diets of denture wearers with mandibular conventional and implant-supported overdentures. Materials and Methods: One-week dietary logs were evaluated for 58 subjects with controlled diabetes at baseline with their original dentures and with new dentures 6 months after treatment completion. Subjects received new maxillary and mandibular complete dentures, 21 with mandibular conventional dentures and 37 with implant-supported overdentures. A 10-point chewing difficulty rating scale (10 for most difficult-to-chew foods) was used to rate food items in the dietary logs. Results: ANOVA showed no differences between the chewing difficulty mean scores for all foods consumed either at baseline or posttreatment for the two groups. However, the mean scores for the combined consumption frequency of difficult-tochew foods (6 to 10) showed a significant decrease following treatment with both types of dentures. This decline did not differ significantly between the denture types. With original dentures, more than 91% of subjects consumed foods with chewing difficulty scores of 6 to 10 at least seven times per week. With study dentures, only 21% maintained this level of consumption, with the frequency decreasing to four to six times per week in 24% and one to three times per week in 43% of subjects. The declines in consumption frequency of more difficult to chew foods with study dentures were in a higher percentage of subjects in the implant than in the conventional group. Conclusion: After 7 months of adaptation to new dentures, patients consumed fewer difficult-to-chew foods than with their original dentures. This decline was more frequent with mandibular implant-supported overdentures than with conventional dentures. Dietary counseling should be considered as part of implant and complete denture therapy.

Purpose: The aim of this study was to evaluate the effectiveness of microwave irradiation sterilization on hard chairside reline resins. Materials and Methods: Specimens of three reline resins (Kooliner, Tokuso Rebase, and Ufi Gel Hard) were fabricated and subjected to ethylene oxide sterilization. The specimens were then individually inoculated (107 cfu/mL) with Tryptic Soy Broth media containing one of the tested microorganisms (C albicans, S aureus, B subtilis,and P aeruginosa).After 48 hours at 37°C, the samples were vortexed for 1 minute and allowed to stand for 9 minutes, followed by a short vortex to resuspend any organisms present. After inoculation, 40 specimens of each material were immersed in 200 mL of water and subjected to microwave irradiation at 650 W for 6 minutes. Forty nonirradiated specimens were used as positive controls. Replicate specimens (25 µL) of suspension were plated at dilutions of 10-3 to 10-6 on plates of selective media appropriate for each organism. All plates were incubated at 37°C for 48 hours. After incubation, colonies were counted, and the data were statistically analyzed by the Kruskal-Wallis test. Twelve specimens of each material were prepared for SEM. Results: All immersed specimens showed consistent sterilization of all the individual organisms after microwave irradiation. SEM examination indicated an alteration in cell morphology after microwave irradiation. Conclusion: Microwave sterilization for 6 minutes at 650 W proved to be effective for the sterilization of hard chairside reline resins.

Purpose: The aim of this article was to study frequencies and distribution of remakes of all-ceramic inlays/onlays, veneers, and crowns occurring before and after cementation. Materials and Methods: A total of 2,069 sintered feldspathic ceramic restorations (Colorlogic) and 1,136 pressure-molded ceramic restorations (IPS Empress 1 and 2) were produced during the study period by one dental laboratory. The laboratory gave an unqualified and unlimited guarantee for their ceramic restorations. The outcome variable was reports from the clinicians to the dental laboratory about any problems related to the restoration, necessitating remake. Results: Problems occurring before cementation occurred in 4.4% of the restorations. Veneers were remade more frequently than the other types of restorations (6.6%). After cementation, the overall 2-year rate of remakes was 1%, indicating a survival rate of the ceramic restorations of 99%, with inlays/onlays exhibiting the highest (99.8%) and crowns the lowest (98.4%) rates. This difference in rates was significant. No significant differences in remakes between ceramics or tooth categories were found. Conclusion: There were few problems in a short- to medium-term perspective that, in the opinion of general practitioners, necessitated remakes of allceramic restorations.

Purpose: The aim of this study was to evaluate the clinical performance of customized ceramic single-implant abutments in combination with two different techniques for fabricating crowns. Materials and Methods: Twenty consecutive patients were provided with 24 single-implant restorations with customized ceramic abutments. The restorations were either cemented to the abutment (n = 13) or fabricated with the veneering material fused directly onto the ceramic abutment (n = 11). The patients were evaluated at 6 and 12 months with radiographs and clinical parameters for complications and soft tissue response. Results: All implants and restorations were still in function after 1 year. Few clinical problems were reported during the follow-up period. The interproximal soft tissue recovered to near normal size. The mean marginal bone loss was similar for both groups, reaching an average of 0.3 mm (SD 0.71) after 1 year in function. Conclusion: The shortterm results indicate that customized ceramic abutments are successful and have comparable function, regardless of fabrication method.

Purpose: The aim was to clarify the associations among subjective symptoms, clinical signs of temporomandibular disorders (TMD), and radiographic findings in the mandibular condyles of elderly people during a 5-year follow-up. Materials and Methods: As part of a comprehensive medical survey of a random sample born in 1904, 1909, and 1914 (Helsinki Aging Study), 364 subjects living in Helsinki participated in the dental part of the examination during 1990 and 1991; after 5 years, 103 of these were reexamined. Comprehensive data on TMD were available for 94 subjects, and radiographic data were available for 88. TMD were assessed by Helkimo's anamnestic and clinical indices, and radiographic status was assessed by panoramic radiographs. Results: During the 5-year follow-up, reported anamnestic symptoms of TMD for men changed little (9%); among women, the change from baseline was 42%. When the unchanged indices were compared, the gender difference was obvious. At baseline, 5% of the women, but no men, had severe signs (clinical index III) of TMD. At the end of follow-up, none showed severe signs. Comparison of radiographic findings between baseline and follow-up showed no differences, nor did differences appear in associations between radiographic findings and anamnestic or clinical indices. Conclusion: During the 5-year follow-up, signs and symptoms of TMD in these elderly individuals became milder or vanished. The radiographic status of the condyles remained stable, and no association appeared between radiographic findings and signs and symptoms of TMD.

Purpose: This laboratory study compared the shear bond strength between three indirect resin composites and a noble alloy using their respective bonding systems. Materials and Methods: One hundred twenty disks cast in a medium-gold, high-noble metal-ceramic alloy (V-Deltaloy) were divided equally into four groups and received different treatments for veneering: Conventional feldspathic porcelain (Omega) was applied on one set of specimens to be used as a control, and three indirect resin composites (Artglass, Sculpture, Targis) with their respective bonding systems were used for the other groups. The specimens were tested in a parallel shear test, 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. The fractured specimens were evaluated to determine the nature of the failure. Results: The mean shear bond strength values (in MPa), before and after wet storage and thermocycling, were 30 and 23 for the metal-ceramic group, 29 and 23 for the Artglass group, 20 and 19 for the Sculpture group, and 17 and 14 for the Targis group, respectively. The metal-ceramic and Artglass groups exhibited significantly higher bond strengths than the other two groups. All specimens, with the exception of the Sculpture group, showed a significant decrease in bond strength after wet storage and thermocycling. Conclusion: No group exceeded the shear bond strength of the metal-ceramic group, but the Artglass group with its respective metalresin bonding system exhibited similar bond strengths. The Sculpture group showed a stable bond after water storage and thermocycling.

Purpose: A prospective, randomized, controlled 5-year multicenter study evaluated the long-term clinical function of CerAdapt ceramic abutments compared to titanium abutments on Brånemark implants supporting short-span fixed partial dentures (FPD). Materials and Methods: Initially, 105 Brånemark implants were placed in a total of 32 patients at three different clinics; 103 implants remained after initial healing. Fifty-three ceramic and 50 titanium abutments were connected to support 36 FPDs, 19 on ceramic and 17 on titanium abutments. Results: Thirty patients with 29 FPDs were examined after 5 years. There was a cumulative success rate of 97.2% for FPDs (94.7% for ceramic and 100% for titanium abutment-supported FPDs). One of 53 ceramic and none of 50 titanium abutments failed, giving survival rates of 98.1% and 100%, respectively. There was a mean marginal bone loss of 0.3 mm and 0.4 mm, respectively, for ceramic and titanium abutments. Soft tissues around abutments and adjacent teeth appeared healthy, and no significant differences were recorded for mucosal bleeding and plaque between ceramic and titanium abutments. Crown margins at FPD insertion were positioned as follows: 21% submucosally, 33% at the mucosal margin, and 46% supramucosally. Changes in mucosal level were recorded at 12% of the abutments, with 73% of all changes recorded at ceramic abutments. There was a balance between more or less exposed crown margins during the first 2 years, in contrast to the 2- to 5-year period, when all changes meant less exposed margins. Conclusion: Safe long-term functional and esthetic results can be achieved with CerAdapt alumina ceramic abutments on Brånemark implants for short-span FPDs.

Purpose: This research determined whether there is a measurable effect of local geometry factors on leucite content of dental porcelain in fixed partial dentures (FPD). Materials and Methods: Four-unit FPD frameworks (n = 36) were fabricated using a nickel-chromium alloy (Rexillium III). Body porcelain (Crystar, shade A2) was applied in one increment and subjected to two simulated body firings, followed by a simulated glaze firing to achieve a thickness of 1.5 to 2.0 mm. The completed FPD specimens were randomly assigned to three groups of 12 specimens each: (1)simulated post-soldering, (2)multiple firing, and (3) control. The FPDs from each test group were sectioned into individual units: canine retainer, premolar pontic, molar pontic, and molar retainer. The porcelain was removed from each unit, and the leucite content was measured via quantitative x-ray diffraction. Results: Porcelain cracking indicated that the soldering simulation had successfully reproduced conditions in the dental laboratory that result in porcelain cracking during soldering. The leucite content was not significantly different between the retainer and pontic units for either the soldering simulation or control FPDs, although the canine retainer units did have a slightly lower leucite content than the pooled values of the other units. Comparison of the pooled data for the three groups indicated statistically significant differences among the leucite contents. Conclusion: Compared to the control, the simulated post-soldering procedure produced a significant increase in leucite, and the multiple firing group exhibited a significant decrease in leucite. Increases in leucite weight fraction during post-soldering operations-and the larger thermally induced stresses that accompany these leucite increases-are responsible for the cracking that occurs.

Purpose: This study investigated fracture load of computer-aided design/manufacturing (CAD/CAM)-generated slot-inlay fixed partial dentures (FPD) machined from ceramic and composite. Materials and Methods: Ninety slot-inlay FPDs were machined in groups of 15 specimens each using the same design on a Cerec 3 unit. Materials were assigned to groups: (1)Mk II feldspathic ceramic, (2)ProCAD glass-ceramic, (3)glass-ceramic 1, (4) glass-ceramic 2, (5)composite 1, and (6)composite 2. The slot-inlay FPDs were placed on models with two abutment teeth without cementation and loaded to fracture. For control, test bars (n = 15) were machined from each of the materials, and flexural strength was examined using three-point bending. Data were statistically analyzed using ANOVA and Scheffé tests. Results: Fracture load of groups 4 (1,557 N, SD 236), 5 (1,048 N, SD 77), and 6 (1,512 N, SD 106) was significantly higher than that of groups 1 (652 N, SD 53) and 2 (773 N, SD 65). Flexural strength of group 4 (256 MPa, SD 20) was significantly higher than that of groups 1 (103 MPa, SD 6), 2 (127 MPa, SD 15), 3 (162 MPa, SD 32), 5 (178 MPa, SD 18), and 6 (170 MPa, SD 20). Conclusion: Fracture loads of glass-ceramic 2 and composite 2 appear adequate for CAD/CAM slot-inlay FPDs.

Purpose: The purpose of the study was to determine the changes in bone mineral density of the mandible in complete and removable free-end saddle denture wearers over a 6- month period. Materials and Methods: Twenty removable partial denture patients and 20 complete denture wearers participated. Two dental panoramic radiographs were taken from each patient, the first prior to denture delivery and the second after 6 months of denture wearing. Bone mineral density measurements were performed on panoramic radiographs with a five-step copper stepwedge attached to each film cassette. Bone mineral density values of the measured regions of interest were expressed in equivalents of the stepwedge thickness (mm). Results: The results revealed minor changes in bone mineral density values of the examined regions in the 6-month period. Under the distal end of complete denture saddles, the bone mineral density values decreased, whereas the values under the distal end of removable partial dentures increased. However, the difference between the first and second measurements was not significant. In each of the examined groups, the bone mineral density values at the gonion increased significantly by approximately 20%. This was attributed to the increased strain forces of the masseter muscle at the gonion after denture delivery. Conclusion: Significant increase of bone mineral density values was registered 2 mm above the gonion in both complete and removable partial denture wearers. Age and gender were not related to the bone mineral density changes over a 6-month period.