The International Journal of Prosthodontics, 01/2018

Purpose: To determine a possible association between asymptomatic temporomandibular joint (TMJ) condylar erosion and the number of missing posterior teeth and their location, as well as the number of dental quadrants with missing posterior teeth. Materials and Methods: This case-control study involved 210 patients (male to female ratio = 98:112) aged 16-74 years, with 105 asymptomatic patients with TMJ condylar erosion and a control group of 105 patients without TMJ condylar erosion. Cone beam computed tomography images were evaluated to classify the severity of TMJ condylar erosion as grade 0 (absence of erosion), grade I (slight erosion), grade II (moderate erosion), or grade III (extensive erosion). Results: The number of missing posterior teeth (mean ± standard deviation [SD]; 2.7 ± 2.4 vs 0.7 ± 1.2) (P < .001), number of dental quadrants with missing posterior teeth (1.5 ± 1.3 vs 0.6 ± 0.9) (P < .001), and bilateral location of missing posterior teeth (41 ± 39.0 vs 10 ± 9.5) (P < .001) were all significantly higher in patients with erosion than in those without erosion. The condylar erosion grade was significantly associated with the number of missing posterior teeth (odds ratio [OR] = 1.24; P = .006), the number of dental quadrants with missing posterior teeth (OR = 1.36; P = .006), and the bilateral occurence of missing posterior teeth (OR = 3.03; P = .002). Conclusion: The findings from this study suggest a possible association between TMJ condylar erosion grades and the number of missing posterior teeth, the number of quadrants with missing posterior teeth, and the bilateral occurence of missing posterior teeth.

Purpose: To compare prosthesis and implant failures and marginal bone loss (MBL) resulting from submerged vs nonsubmerged dental implant protocols. Materials and Methods: Electronic and manual searches of two databases (MEDLINE [PubMed] and Cochrane) were conducted to identify randomized controlled trials (RCTs) comparing submerged to nonsubmerged dental implant protocols. Data were independently extracted by two reviewers, and meta-analyses were performed for the included RCTs. The Cochrane Risk of Bias tool was used to assess the quality of included studies. Results: Eight RCTs were identified, and six were included. Four of the included studies were considered to be at high risk of bias, one at unclear risk, and one at low risk. The meta-analysis for studies reporting MBL revealed significantly more bone loss around submerged implants (I2 = 0%, P = .04; mean difference: 0.12; 95% confidence interval: 0.00, 0.24); however, there were no differences in implant or prosthesis failures between the two interventions. Conclusion: Two conclusions were made: (1) There were no differences between the two interventions regarding implant or prosthesis failures, and (2) submerged implants exhibited statistically significantly more MBL, but this difference was not clinically relevant. These conclusions should be interpreted with caution, since the present review is underpowered and the included RCTs were considered to be at high risk of bias.

Purpose: This study describes the development of a methodology for using three-dimensional (3D) image superimposition to measure volumetric changes in bone level around dental implants in comparison with linear measures. Materials and Methods: The sample was comprised of 46 dental implants of 6-mm length and 4.1-mm diameter placed in the posterior maxilla and posterior mandible in 20 patients. All implants received screw-retained single crowns. Radiographic images were taken using cone beam computed tomography (CBCT) and digital periapical radiography after implantation and after 12 and 24 months of functional loading (after crown placement). Tridimensional reconstructions of the bone perimeter closest to the implant were developed, superimposed, and volumetrically measured. Linear measures of bone levels were recorded in periapical radiography images. A multilevel regression model tested volumetric and linear bone loss. Results: The mean peri-implant linear bone loss for the first and second years was 0.2 ± 0.4 mm and 0.1 ± 0.2 mm, respectively, and the mean volumetric bone loss for the first and second years was 7.2 ± 6.1 mm3 and 6.4 ± 7.8 mm3, respectively. It was estimated that an increase of 1 mm of linear bone loss was associated with a mean volumetric bone loss of approximately 14 mm3 (P < .001). Conclusion: The findings showed that linear and volumetric bone loss measures are related. Measuring volumetric bone changes around implants is possible provided that the CBCT images have proper contrast and sharpness, particularly around the implant outline. Improvements in image quality and in the filters for bone tissue detection would be important for this methodology to be made faster and used clinically.

Dental rehabilitation of acute cases of enamel renal syndrome is challenging due to the absence of clinical reports. In the present case history report, examination of an 18-year-old patient revealed a complete lack of permanent teeth, as well as irregular and swollen bone and gingival morphology. Radiographs showed multiple impacted teeth in both arches. Creating a 1.5- to 2-cm interarch space was necessary for setting complete dentures. The ideal occlusal plane was chosen by combining two techniques (cephalometric radiograph and modification of the mandibular occlusal rim according to anatomical guidelines). Extraction of impacted teeth and recontouring of the alveolar process were performed simultaneously. The mandibular denture was connected through Locator abutments to two symphyseal implants. This pioneering clinical report will provide guidance to practitioners in the surgical intervention of patients with FAM20A (family with sequence similarities 20 A) gene mutations.

Purpose: To investigate the clinical survival and success rates of conventionally luted three- and four-unit fixed dental prostheses (FDPs) with zirconia frameworks (Cercon Smart Ceramics, DeguDent) after a mean observation period of 119 ± 36 months. Materials and Methods: A total of 75 patients were treated in the Department of Prosthodontics at the University of Goettingen, Germany, and a total of 99 posterior FDPs were inserted and luted with zinc phosphate cement. Time-dependent survival and success rates were calculated using Kaplan- Meier curves, and their relationships with the type of veneer (ceramic), location (maxilla vs mandible), and span length (three-unit vs four-unit) were analyzed with a Cox regression model (P < .05). Results: Of the 99 inserted FDPs, 24 were lost to follow-up, 51 remained functional and passed the 10-year examination (overall survival rate: 75.0%; 95% confidence interval [CI]: 0.64, 0.85), and 13 were absolute failures caused by technical events (technical survival rate: 84%; 95% CI: 0.64, 0.85). In 50 FDPs, relative failure required a clinical intervention to maintain function (overall success rate: 40%; 95% CI: 0.29, 0.52). For 35 of these FDPs, the relative failure was caused by technical events (technical success rate: 61%; 95% CI: 0.49, 0.73). None of the evaluated factors showed an association with overall or technical survival or success. Conclusion: Zirconia-based posterior FDPs produced with a first-generation computer-assisted manufacturing (CAM) system revealed high rates of absolute and relative failure, mainly due to technical events, after a mean observational period of 10 years. Further clinical studies with updated computer-assisted design (CAD)/CAM systems are needed to determine the long-term performance of zirconia-based FDPs.

Purpose: This review aimed to compile and enumerate all the factors described in the literature that may affect the decision to use either cemented or screw-retained restorations and to determine the relative weights of each factor by type of retention and prosthesis. Materials and Methods: The literature was reviewed, and the factors were classified as either determining (present in a clinical situation in which one of the retention mechanisms was clearly more suitable than the other) or conditioning (present in clinical situations in which one type of restoration was not clearly more advantageous than the other). Results: Three determining factors (esthetic outcome, retention, and biologic risk) and five conditioning factors (passive fit, fracture strength, occlusal area, complications, and retrievability) were identified. Conclusion: Although there is not a clearly better alternative for all clinical situations, determining factors in certain scenarios can render one of the two approaches more recommendable. For esthetic reasons, when the implant angle cannot be corrected to conceal the access hole, cementation is more suitable; however, screw retention is the better option when the occlusal space is under 6 mm or margins cannot be located supra- or equigingivally. In the absence of determining factors, the decision should be based on conditioning factors, which carry different weights depending on the type of prosthesis.

Purpose: To compare operating time and patient perception of conventional impression (CI) taking and intraoral scanning (IOS) for manufacture of a tooth-supported crown. Materials and Methods: A total of 19 patients needing indirect full-coverage restorations fitting the requirements for a split-mouth design were recruited. Each patient received two lithium disilicate crowns, one manufactured from CI taking and one from IOS. Both teeth were prepared following the manufacturers' recommendations. For both impression techniques, two retraction cords soaked in 15% ferric sulphate were used for tissue management. CIs were taken in a full-arch metallic tray using one-step, two-viscosity technique with polyvinyl siloxane silicone. The operating time for each step of the two impression methods was registered. Patient perception associated with each method was scored using a 100-mm visual analog scale (VAS), with 100 indicating maximum discomfort. Results: Median total operating time for CI taking was 15:47 minutes (interquartile range [IQR] 15:18 to 17:30), and for IOS was 5:05 minutes (IQR 4:35 to 5:23). The median VAS score for patient perception was 73 (IQR 16 to 89) for CI taking and 6 (IQR 2 to 9) for IOS. The differences between the two groups were statistically significant (P < .05) for both parameters. Conclusion: IOS was less time consuming than CI taking, and patient perception was in favor of IOS.

This case history report describes the fabrication of a mandibular prosthesis for an edentulous patient with four implants. Impressions were made with a photogrammetry system, and the framework was manufactured using cobalt-chromium laser sintering, later milled at the implant connection level, and then coated with a composite resin. The described protocol suggests that the employed manufacturing technologies readily lend themselves to routine management of the edentulous mandible, although further research and long-term clinical data are clearly needed.

The utilization of additive manufacturing (AM) technology for the production of auricular prostheses has been widely acknowledged. However, few studies and case history reports have evaluated the esthetic outcomes of AM prostheses compared to those of conventionally manufactured prostheses. In this case history report, three manufacturing approaches- conventional, indirect, and direct mold preparation-were assessed for their esthetic outcomes in the same patient.

Purpose: The literature shows that the performance of densely sintered zirconia single crowns seems to be unaffected by the cement material. The purpose of this study was to evaluate the effects of various cement materials on the stress distribution in a monolithic translucent zirconia crown. Materials and Methods: A crown-cement-dentin complex was modeled. Six cements were evaluated: zinc phosphate, glass-ionomer, resin-modified glass-ionomer, dualcure resin, calcium aluminate-based, and a theoretical or conceptual cement with mechanical properties close to those of dentin (ie, monoblock cement). Results: While varying stress concentrations were found within the cements, the stress concentrations in the crown and dentin were consistent irrespective of cement material. Conclusion: Within the limitations of this study, it can be concluded that cement material had a negligible effect on stress distribution in the monolithic zirconia crown.

Purpose: This study compared the marginal gaps of computer-aided design/computeraided manufacture (CAD/CAM)-fabricated all-ceramic crowns constructed from scanned impressions and models and with two different occlusal reduction designs. Materials and Methods: Two typodont mandibular first molars were prepared to receive CAD/CAM- fabricated all-ceramic crowns. Both molars were prepared to ideal crown reduction, the first with anatomical occlusal reduction (AOR) and the second with completely flat occlusal reduction (FOR). Nine polyvinyl siloxane impressions (PVS) were taken, and nine stone replicas fabricated for each preparation. All impressions and stone models were scanned using a laser scanner (Planmeca Planscan, E4D technologies), and 36 lithium disilicate (IPS e.max CAD) crowns were milled. The marginal gap was measured in four locations using a light stereomicroscope. Results: Crowns constructed from preparations with both occlusal reduction designs demonstrated similar marginal gaps (FOR = 97.98; AOR = 89.12; P = .739). However, all crowns constructed from scanned impressions presented significantly larger marginal gaps than the crowns fabricated from scanned models (impressions = 109.26; models = 77.84; P = .002). Conclusion: Scanning stone models produced all-ceramic crowns with significantly smaller marginal gaps than scanning impressions, irrespective of the occlusal reduction design.

Purpose: The purpose of this in vitro study was to evaluate wear and fracture strength of chairside-milled new ceramic resins after artificial aging in a chewing simulator. Materials and Methods: Two ceramic resins (Lava Ultimate and Vita Enamic) and two conventional ceramics (IPS Empress CAD and Celtra Duo) were tested. For analysis of wear, baseline and follow-up scans of the specimens were made, the scans were superimposed, and the wear was calculated. To determine fracture strength, the specimens were loaded until they fractured. Results: Lava Ultimate showed the highest wear, caused the lowest wear of the opposing dentition, and showed statistically significantly higher fracture strength than conventional ceramics after cyclic loading. Conclusion: New ceramic resins for chairside milling are a good alternative to conventional ceramics.

Purpose: This study aimed to compare the long-term outcomes of two different nonimplant treatments in the bilateral shortened dental arch (SDA). Materials and Methods: In a multicenter randomized controlled clinical trial, patients with complete molar loss in one arch were assigned to one of two different nonimplant treatments. In the partial removable dental prosthesis (PRDP) group, patients were provided with a distal-extension prosthesis retained with precision attachments. In the SDA group, patients were treated according to the SDA concept by preserving or restoring a premolar occlusion. Results: Of the 152 treated patients, 82 reached the 10-year examination independent of their dental or prosthetic status. In the intention-to-treat analysis, the survival rates for tooth loss at 10 years were 0.44 (95% confidence interval [CI]: 0.30 to 0.56) in the PRDP group and 0.52 (95% CI: 0.37 to 0.65) in the SDA group. For tooth loss in the study arch, the survival rates were 0.67 (95% CI: 0.52 to 0.78) in the PRDP group and 0.60 (95% CI: 0.45 to 0.73) in the SDA group. The number of teeth lost was higher than expected. In a multivariate analysis using a multiple Cox regression model, the covariates age (unit: 1 year, Hazard Ratio [HR]: 1.033, P = .03) and DMFT value (unit: 1 tooth, HR: 1.121, P = .03) were significant for time to first tooth loss in the study arch. Conclusion: The results suggest an overestimation of the influence of the prosthetic management of the bilateral SDA. In treatment decisions, patient preferences should be considered with appropriate weight.