The International Journal of Prosthodontics, 05/2018

Purpose: To report retro-prospective data on the prevalence of overall implant failure in a large number of edentulous patients treated at one referral clinic over a 30-year period and to analyze possible associations between implant failure and basic clinical variables. Materials and Methods: Altogether, 24,781 implants were consecutively placed in 4,585 edentulous arches between 1986 and 2015. All implant failures identified at the clinic during follow-up were consecutively recorded, and a multivariate logistic regression analysis was performed to identify possible associations between implant failure and different clinical factors. Results: Altogether, 1,333, 688, and 249 treated arches were followed up for 15, 20, and 25 years, respectively. Cumulative survival rates (CSR) for the treated arches were 86.2% and 83.8% after 15 and 25 years, respectively. Most patients lost only one implant each (58%). Loss of all implants was reported in 68 arches, with total failure rates of 1.9% and 2.2% after 15 and 25 years, respectively. The strongest associations with increased risk for implant failure were maxilla (hazard ratio [HR] 4.76; 95% confidence interval [CI] 3.70 to 6.25) and implant surface (HR 2.38; 95% CI 1.59 to 3.57). Age at surgery, implant surgeon, calendar year of surgery, and time of follow-up also showed significant associations with risk of implant failure (P < .05). A completely steady-state level in implant survival was not observed, but few implants were lost up to the last years of follow-up. Conclusion: There is a higher risk for implant failure in the maxilla compared to the mandible. Risk is reduced when using implants with a moderately rough surface. The highest risk for failure was observed during the first year. This was followed by a reduced failure rate, which never reached a steady-state level.

Purpose: To quantify the depth of penetration of Candida albicans (C albicans) into a denture base resin and to investigate its viability after disinfection. Materials and Methods: Heatpolymerizing polymethyl methacrylate plates were contaminated with C albicans, then washed, dried, and prepared for scanning electron microscopy (SEM). Vertical surfaces were cut, and the depth of any penetration was measured. For viability after disinfection, plates were contaminated, subjected to one of two disinfection techniques, and subcultures were taken to determine viability. Results: The results showed that at 7, 14, and 21 days after exposure, the mean depth of penetration of C albicans was 33.9, 96.9, and 97.0 μm, respectively. The depth of penetration was time dependent, with the deepest being 631 μm at 21 days. Daily subcultures for 10 days revealed that penetrated cells remained viable and were not affected by the disinfectant. Conclusion: To the present authors' knowledge, this is the first time that the viability of denture base-penetrated C albicans has been shown, even after disinfection. The implication of these results is that denture resin is likely to be penetrated, especially in patients with chronic or recurrent denture stomatitis. If the C albicans remain viable, then the infected denture-fitting surfaces may have to be replaced by removing at least a 1-mm layer of contaminated resin.

Purpose: To quantify the strain development of a new prefabricated implant-supported mandibular full-arch reconstruction. Materials and Methods: Five resin models reflecting edentulous mandibles were each restored with three interforaminal implants and prefabricated frameworks with a novel compensation mechanism, cast frameworks, and computer-aided design/computer-assisted manufacturing (CAD/CAM)-fabricated frameworks. Strains were recorded during superstructure fixation. Statistical analyses (analysis of variance, t tests; α = .05) were based on level of misfit and distribution of misfit. Results: Cast restorations showed significantly higher levels of misfit and a significantly more uneven distribution of misfit compared to prefabricated and CAD/CAM restorations (P < .05 for all comparisons). Prefabricated and CAD/CAM frameworks showed a similar low level and distribution of misfit (P = .24145 and P = .2837, respectively). Conclusion: The compensation mechanism of the prefabricated frameworks provides a level of fit comparable to CAD/CAM superstructures.

Purpose: To analyze the clinical fit of monolithic zirconia single crowns (MZSCs) in a prospective cohort study. Materials and Methods: A total of 30 posterior teeth were restored with MZSCs. Silicone replicas were made to measure the clinical fit using a stereomicroscope. Measurements were conducted at 17 points per crown at the marginal and occlusal surfaces. Results: The mean clinical fit was 0.104 mm at the crown margin and 0.101 mm at the occlusal surface. Measured distances at the marginal and occlusal surfaces were comparable. Conclusion: MZSCs showed acceptable clinical fit.

Purpose: This study aimed to evaluate treatment outcomes of mandibular overdentures retained by two different mini-implant systems with ball attachments under a two-step immediate loading protocol. Materials and Methods: This clinical trial investigated treatment outcomes of mandibular mini-implant overdentures in 45 edentulous patients. MDI implants (3M ESPE) and SlimLine implants (Dentium) were randomly selected for placement in the anterior mandible in each group (MDI = 21; SlimLine = 24) with a flapless surgical approach. The side of the tissue in the region of the complete mandibular denture where mini-implants were placed was immediately relined with soft reliner (COE-SOFT). The female components were attached on the dentures 2 months after implant placement. Clinical and radiographic data were collected during follow-up. Statistical analyses were performed using SPSS software version 22.0 (α = .05). Results: A total of 177 mini-implants were inserted in the anterior mandibles of 45 totally edentulous patients. There were five implant failures (97.2% success rate) and no significant differences between the two implant groups. Most mini-implants showed stable initial Periotest values (a mean ± standard deviation of 1.03 ± 3.65 mm) and a mean marginal bone loss of 0.50 ± 0.75 mm at 12 months. Multiple regression analysis revealed that implants ≤ 2.4 mm in diameter had higher Periotest values than those ≥ 2.8 mm. Intial Periotest values significantly influenced implant failure (P < .05). Conclusion: There were no significant differences in treatment outcomes between patients treated with MDI or SlimLine implants. Mini-implants with wider diameters showed higher initial stability than those with narrow diameters, which may influence implant survival.

Purpose: To evaluate the load at fracture and influence of artificial aging of posterior teeth occlusal veneers ("table tops") made of two different ceramics. Materials and Methods: A total of 80 table tops were produced from feldspathic ceramic (VM) and zirconia-reinforced lithium silicate ceramic (CD) using computer-aided design/computer-assisted manufacturing (CAD/CAM). Half of the specimens from each ceramic were aged prior to the load test. Results: Mean ± standard deviation (SD) load at fracture was significantly higher for CD (1,571.1 N ± 297.0 N) than for VM (573.6 N ± 86.4 N) (P < .001). After aging, load at fracture increased significantly to 1,819.0 N (± 310.6 N) for CD and to 745.2 N (± 168.3 N) for VM. Conclusion: The use of zirconia-reinforced lithium silicate ceramic for molar nonprep table tops should be uncomplicated according to the high load-at-fracture values. Mechanical stability of either ceramic is not compromised by aging.

Purpose: To assess bond strength and failure patterns of carbon fiber-reinforced composite (CFRC) and veneering materials. Materials and Methods: A total of 20 samples were prepared: 10 veneered with polymethylmethacrylate (group A) and 10 with composite resin (group B). Shear bond strength (SBS) was measured, and failed samples were microscopically observed. Results: The mean ± standard deviation (SD) SBS of specimens in group A was slightly higher (7.39 ± 0.24 MPa) than specimens in group B (5.68 ± 0.29 MPa). Microscopic observation showed an adhesive fracture pattern at the CFRC-adhesive interface in both groups. Conclusion: Adhesion between CFRC and veneering material is reliable and predictable, although a specific protocol needs to be developed to improve adhesion.

Purpose: Methods for removing temporary cement with an antibacterial effect might improve prosthetic treatment prognosis. Materials and Methods: Three removal methods were assessed: (1) immersion of an acrylic provisional restoration in a temporary cement dissolver (Temp-off); (2) mechanical removal with a dental explorer; and (3) sandblasting. Two temporary cements, one with eugenol (Temp-Bond) and one without eugenol (Temp-Bond NE) and of two thicknesses (100 μm and 250 μm), were examined. Results: Immersion in Temp-off produced the most effective bacterial count decrease compared to the other methods (P < .05). No significant difference was found between the two cement types, although the decrease in count was more evident in the thicker (250 μm) cement layer. Conclusion: Temp-off dissolving liquid used for removal of temporary cement exhibited an antibacterial effect and nonmechanical cleaning ability.

Purpose: The purpose of this retrospective clinical study was to evaluate the clinical outcomes of nonprecious alloy (NPA) vs precious alloy (PA) telescopic crown-retained removable partial dentures (TRPDs), the factors influencing survival, and the type and number of maintenance procedures required during the observation period. Materials and Methods: This retrospective clinical study is based on 462 patients with a total of 572 TRPDs on a total of 1,946 abutment teeth. The following parameters were analyzed with Kaplan-Meier analysis: sex; alloy type; denture location; number and distribution of abutment teeth (Kennedy Class); vitality of abutment teeth; dentition in the opposing arch; and participation in follow-up visits. Results: The mean observation period was 3.87 ± 3.15 years (2.99 ± 2.52 years for NPATRPDs and 5.36 ± 3.53 years for PA-TRPDs; maximum 11.01 years). During the observation period, 4.2% (n = 24) of the TRPDs ceased functioning and 8.3% (n = 161) of the abutment teeth had to be removed. The calculated 5- to 10-year survival probabilities were 96.1% and 84.0%, respectively, for the TRPDs. The number of abutment teeth was the only parameter that significantly (P < .05) impacted this probability, whereas the vitality of the abutment teeth and the type of alloy significantly (P < .05) impacted the survival probability of the abutment teeth. NPA-TRPDs needed significantly earlier initial treatment than PA-TRPDs (P < .05). Conclusion: The type of alloy seems to have no impact on TRPD survival, but seems to have an influence on the survival of the abutment teeth. There are also differences in maintenance between NPA- and PA-TRPDs.

Purpose: To investigate whether ultra-low-dose multidetector computed tomography (MDCT) combined with the reconstruction techniques filtered backprojection (FBP), adaptive statistical iterative reconstruction (ASIR), or model-based iterative reconstruction (MBIR) alters the subjective classification of revised Lekholm and Zarb (LZ) bone types at prospective dental implant sites. Materials and Methods: Three cadavers underwent a reference MDCT examination using a standard dose volume (CT dose index [CTDIvol]: 29.4 mGy) and reconstructed with FBP in addition to five test protocols (LD1-LD5) using ultra-low doses (CTDIvol: 4.19, 2.64, 0.99, 0.53, and 0.29 mGy, respectively) and reconstructed with FBP, ASIR 50, ASIR 100, and MBIR. Transverse cross-sectional images of the jawbones were obtained, and three examiners subjectively classified the bone type in each image using the revised LZ classification. The bone type classifications obtained using the reference examination were compared with those obtained from the test protocols for each examiner, and kappa statistic was used to analyze the level of agreement between the reference and test protocols. The clinical significance of the differences was analyzed with Wilcoxon signed rank test. Results: Examiners 1 and 2 found moderate to strong agreement between the reference and test protocols, while Examiner 3 found strong to almost perfect agreement (P < .001). The Wilcoxon signed rank test did not demonstrate a clinical significance of the differences between the reference and test protocols for any of the three examiners. Conclusion: MDCT dose reductions of up to 99% did not significantly alter the subjective classification of bone at dental implant sites.

Several attachment systems for implant-supported removable dental prostheses (ISRDPs) are currently available. The bar attachment option includes cast or milled alloyed male and female parts. Replaceable slide attachments made from elastic materials can be inserted into the female part of the bar to counter loss of friction that develops due to wear. Another approach involves milling the female part from organic thermoplastic polymers. In the present case history report, an edentulous maxilla was restored with a digitally fabricated ISRDP with the female part of the bar milled from polyether ether ketone (PEEK) polymerized into a zirconia framework.

Purpose: This study was conducted to compare the fit and retention of implant-supported, metal-free copings fabricated from zirconia, polyetheretherketone (PEEK), or composite, as well as to evaluate the possible correlation between internal adaptation and retention. Materials and Methods: A total of 36 copings were milled from zirconia, PEEK, or composite blanks (n = 12 in each group). Marginal and internal gap were evaluated by replica technique, and the pull-out test was used to evaluate retention. One-way analysis of variance, post hoc Tukey tests, and Pearson correlation coefficient test were used to analyze the data. Results: Zirconia had significantly better marginal/internal adaptation (P < .05) than the other materials. There was no statistically significant difference in mean retention force between the different groups (P > .05). No correlation was found between internal adaptation and retention. Conclusion: In the metal-free copings tested, zirconia showed the best adaptation. The retention of copings was not influenced by internal fit or material type.

Purpose: To evaluate the fracture resistance of computer-aided design/computer-assisted manufactured (CAD/CAM) glass-ceramic incisor crowns fabricated on reverse-tapered preparations. Materials and Methods: Resin abutments with known total occlusal convergence angles (-8, 0, and 12 degrees; n = 20) were scanned with the TRIOS scanner, and glass-ceramic crowns were fabricated with KaVo Arctica, stored in water for either 1 or 30 days, and submitted to fracture test. Results: The fracture resistance of crowns made on reverse-tapered preparations was not significantly different (P = .471) from crowns fabricated over abutments with 0- or 12-degree tapers, irrespective of the water storage period. Conclusion: The fracture resistance of anterior glass-ceramic crowns fabricated over reverse-tapered preparations was similar to that of crowns made on abutments with 0- or 12-degree tapers.

Purpose: To investigate the effects of over-the-counter products on the healing of dentureinduced ulcerations and patients' self-reported pain. Materials and Methods: A total of 140 patients with acute denture-induced ulcerations were randomized into seven treatment groups: denture grinding (control); topical application of corn oil gel (placebo); triester glycerol oxide gel; D-panthenol gel; D-panthenol mouthwash; L-arginine mouthwash; and hyaluronic acid gel. Healing and self-reported pain were assessed after 1, 3, and 7 days of treatment. Results: The percentage of healed lesions in the mandible and maxilla after 7 days was 67% and 65%, respectively. The only significance in healing was for mandibular lesions at 3 days after application of L-arginine mouthwash; at this period, the healing rate was significantly higher than d-panthenol gel, d-panthenol mouthwash, and hyaluronic acid gel (P < .05). Conclusion: Denture grinding as the current protocol for acute denture-induced ulcerations should remain as the default.

Purpose: This study aimed to assess dentists' views of the utility of an unrestored shortened dental arch (SDA) compared to the utility of various prosthetic treatment options. Materials and Methods: A total of 142 dentists working at four sites in Riyadh, Saudi Arabia, were interviewed and presented with 18 scenarios for patients of different ages with SDAs that lost molar teeth. Participants were asked to indicate on a standardized visual analog scale (VAS) how they would value the health of the patient's mouth if the SDAs were left unrestored or restored with five prosthetic dental restorations. Results: With a utility value of 0.0 representing the worst possible health state for a mouth and 1.0 representing the best, dentists' mean utility value for unrestored SDAs was 0.43 (standard deviation [SD] = 0.28). For implant-supported fixed dental prostheses (ISFDPs), cobalt-chromium removable partial dentures (RPDs), acrylic RPDs, cantilever conventional fixed dental prostheses (CFDPs), and cantilever resin-bonded fixed dental prostheses (RBFDPs), the mean utility values were 0.64 (SD = 0.27), 0.54 (SD = 0.20), 0.48 (SD = 0.20), 0.42 (SD = 0.28), and 0.39 (SD = 0.27), respectively. Neither patient age nor dentists' clinical experience had an impact on dentists' perceptions of the utility of unrestored SDAs and outcomes of this treatment concept (P > .01). Conclusion: Restoration of SDAs by ISFDPs received the highest utility value among the surveyed group of dentists. Although the assigned value for unrestored SDAs was low, this value was comparable to the value of SDAs that were restored by acrylic RPDs or cantilever FDPs of either type.

Purpose: To compare the effects of different screw-tightening sequences and torque applications on stresses in implant-supported fixed complete dentures supported by five abutments. Materials and Methods: Strain gauges fixed to the abutments were used to test the sequences 2-4-3-1-5; 1-2-3-4-5; 3-2-4-1-5; and 2-5-4-1-3 with direct 10-Ncm torque or progressive torque (5 + 10 Ncm). Data were analyzed using analysis of variance and standardized effect size. Results: No effects of tightening sequence or torque application were found except for the sequence 3-2-4-1-5 and some small to moderate effect sizes. Conclusion: Screw-tightening sequences and torque application modes have only a marginal effect on residual stresses.

Purpose: The purpose of this cross-sectional study was to describe the oral status and prosthetic treatment needs of dependent, functionally impaired individuals and dependent elderly individuals in comparison with the general population. Materials and Methods: A total of 355 subjects, sampled from the register of increased financial support for dependent and functionally impaired individuals in the north of Sweden, were examined. The variables were number of teeth, Eichner Index, type and condition of prostheses, and treatment needs. Statistical analyses were carried out using an independent samples t test for means and chi-square tests for proportions. Comparisons were made with the results of an earlier study (EPI-Norr) of 908 patients from the general population in the same county. Results: The study group had fewer teeth compared with the general population (20% edentulous in the study group vs 7% in the general population; P < .001), as well as more dentures and fewer tooth- and implant-supported prostheses. A total of 42% of the dentures in the maxilla and 51% of the dentures in the mandible were in poor condition. There was no difference in complications from dental implants between the groups. Conclusion: The results of this study suggest that since the Swedish system for financial support enables dental care to the patient groups in question, the situation is probably better in Sweden than in many other countries. As more accentuated differences can be assumed between these population groups in other countries, these findings are also interesting from an international perspective.

Purpose: This retrospective cohort study examined factors affecting the periodontal condition and survival of remaining teeth 5 years after removable partial denture (RPD) placement using multivariate analyses. Materials and Methods: Of 231 patients who received RPDs at Tohoku University Hospital, 108 patients who had agreed to undergo a 5-year follow-up were examined. The outcomes of RPD treatment were assigned to one of three categories: successful (n = 58), remake (n = 36), and failure (n = 14). A total of 80 patients in the successful and remake groups were included in this study. The parameters analyzed to evaluate the periodontal condition were probing depth, Miller index of tooth mobility, and bone resorption level. Criterion variables were the outcome of each periodontal condition, deterioration, and tooth loss. Independent variables were sex, age, smoking habit, number of periodic maintenance appointments, location of RPD, number of abutment teeth, denture base material, design, and existence of a denture in the opposite jaw. Bivariate analyses were performed using chi-square test, and multivariate regression analysis was used to assess significance. Results: Sex and frequency of maintenance care were independently associated with deterioration of the periodontal condition. Sex and existence of a denture in the opposite jaw were independently associated with tooth loss. Conclusion: The findings suggest that periodic maintenance care and condition of the opposite jaw are essential for maintaining the condition of the remaining teeth.