The International Journal of Prosthodontics, 04/2018

Purpose: This retrospective cohort study in an asymptomatic nonpatient population evaluated the prevalence of specific morphologic changes usually associated with the presence of degenerative joint diseases (DJD) using cone beam computed tomography (CBCT) and examined the associations between DJD and age, sex, and number of teeth present. Materials and Methods: CBCT images (268 TMJs) of 134 asymptomatic patients were studied. Patient data were obtained from clinical records, and calibrated examiners interpreted the CBCT images. The presence or absence of traditional radiographic signs of DJD (erosion, generalized sclerosis, osteophytes, and subchondral cysts) in the condyle and articular eminence of each TMJ were evaluated. The data were submitted to bivariate (chi-square and Fisher exact tests) and multivariate (Poisson regression) analyses (α = .05). Results: The sample was primarily composed of men (52.24%) and individuals aged ≥ 61 years (55.64%); 61.94% were partially edentulous with ≤ 12 teeth in the oral cavity. The most common DJD diagnoses were mandibular condyle osteophytes (30.22%) and erosion (12.69%), followed by articular eminence erosion (8.58%) and mandibular condyle subchondral cysts (7.09%). The bivariate analysis showed a statistically significant association between women and subchondral cysts (P = .007), between edentulous individuals and subchondral cysts (P = .008), and between individuals with ≤ 12 teeth and mandibular condyle erosion (P = .005). In the adjusted Poisson regression analysis, a significant association was found between DJD and gender (P = .015). Conclusion: Despite the limitations of this study, the results show a high prevalence of morphologic changes usually associated with the presence of DJD in asymptomatic subjects. Osseous TMJ abnormalities were most present in women, individuals with a lower number of teeth, and older individuals.

Purpose: To evaluate plaque accumulation, peri-implant soft tissue inflammation, and bone resorption in patients with immediately loaded implants supporting fixed full-arch prostheses. Materials and Methods: A convenience sample of 72 patients treated with fixed full-arch prostheses supported by four to six immediately loaded implants was selected. Bleeding on probing (BOP), Plaque Index (PI), and peri-implant bone loss were measured. The Sixth European Workshop on Periodontology definitions of mucositis and peri-implantitis were used, and collected data were analyzed using a nonparametric test (Spearman's rank correlation). Correlation coefficients (ρ) were defined as follows: 0.2 = very weak; 0.2 to 0.39 = weak; 0.4 to 0.59 = moderate; 0.6 to 0.79 = strong; 0.8 to 1.0 = very strong. Results: A total of 331 implants were analyzed. The mean follow-up observation time was 5.8 years (range: 1 to 14 years); mean PI and BOP were 61.7% and 21.1%, respectively; and mean bone loss was 0.89 mm (standard deviation [SD] 1.09). The mean probing depth was 1.8 mm (range: 0.5 to 5 mm). Five patients presented with one implant each affected by peri-implantitis (6.9%), and 15 patients presented with at least one implant affected by mucositis (20.8%). No correlation was found between PI and bone resorption (P = .08). Very weak correlations were found between BOP and bone resorption (ρ = 0.18; P = .001) and between PI and BOP (ρ = 0.13, P = .019). Conclusion: The results suggest that plaque accumulation is correlated with peri-implant mucositis; however, plaque accumulation alone does not appear to be associated with bone resorption.

Purpose: To investigate the mechanical properties and wear of nylon inserts and abutments in Locator-retained, implant-supported overdentures (L-IODs). Materials and Methods: Clinical wear of inserts and abutments was qualitatively rated in a group of 16 patients with L-IODs. The inserts were also subjected to microscopic analysis, differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). Results: Wear was identified in almost all inserts and abutments. These results were corroborated by DSC and TGA analyses, which showed significant mechanical deterioration of the inserts. Conclusion: Nylon inserts and Locator abutments show relevant signs of deterioration in clinical use, indicating that regular maintenance is an issue that should be addressed with the patients prior to treatment.

Utilizing intraoral bite blocks can aid in stabilizing the mandible during radiation treatment (RT) and minimizing side effects to healthy tissues. This report describes a technique to fabricate a customized acrylic repositioning immobilization bite block that was integrated into the clinical workflow of radiation appointments with no delay in starting RT and with increased patient comfort.

Purpose: To propose a revised Lekholm and Zarb classification that takes into account all possible combinations of compact and trabecular bone and to provide guidelines for increased reproducibility of the classification. Materials and Methods: Three new classes were added to the previous classification. The new classes have been designated as subclasses of bone types 2 and 3, as follows: Type 2b: Thick layer of compact bone surrounding a core of medium-density trabecular bone; Type 2c: Thick layer of compact bone surrounding a core of low-density trabecular bone; and Type 3b: Thin layer of compact bone surrounding a core of medium-density trabecular bone. Three interpretation guidelines were recommended to increase the reproducibility of the revised classification. Three experienced examiners were trained using the revised classification and provided with computed tomography (CT) sectional images of edentulous jawbones for classification. Each examiner classified the images twice with at least a 1-week interval. The intraobserver agreement was measured. Results: The kappa statistic for the intra-observer agreement of the examiners ranged from 0.835 to 0.919 (P .001). Conclusion: The high reproducibility of the proposed revised CT-based Lekholm and Zarb classification obtained in the current study suggests its efficacy in distinguishing between the various combinations of compact and trabecular bone.

Purpose: To analyze the marginal adaptation of computer-aided design/computer-assisted manufactured (CAD/CAM) porcelain laminate veneers. Materials and Methods: A total of 25 three-dimensional (3D) machine-milled laminate veneers were divided into five groups of five each according to fabrication material (E-max; Empress; Lava Ultimate; Suprinity; and Vita Mark II) and cemented in 25 prepared acrylic central incisors. Digital microscopy images (×7.5 magnification) were analyzed for gaps in the mesial/distal surfaces of the prepared tooth and in the cervical, medial, and incisal thirds. Results and Conclusion: All CAD/CAM laminate veneers except for Empress and Suprinity in the middle and incisal thirds showed good results (ie, gaps 120 μm in the cervical, middle, and incisal thirds).

Purpose: To assess the marginal fit of provisional polylactic acid (PLA) crowns obtained via three-dimensional (3D) printing using a profile projector. Materials and Methods: A stone cast was scanned, and 15 provisional dental crowns were designed and printed in PLA using a 0.2-mm nozzle and 135-degree build angle. The marginal fit was measured at six points on each crown using a profile projector. Results and Conclusion: Within the limitations of this study, the marginal fit of PLA provisional restorations was clinically acceptable, and the results were comparable to those observed with polymethyl methacrylate provisional restorations.

Purpose: To assess the efficacy of two experimental denture adhesive gels (adhesives 1 and 2) compared to a commercially available denture adhesive cream (positive control) and no adhesive (negative control). Materials and Methods: This was a single-center, randomized, four-treatment, examiner-blind, crossover study in participants with well-made and at least moderately well-fitting maxillary complete dentures. Incisal bite force until denture dislodgment was measured before application (baseline) and over the following 12 hours for each of the treatments. Between-treatment differences in the area over baseline (AOB) for the bite force at each time point were analyzed using an analysis of covariance model. Results: The efficacy and safety analyses were based on results from 48 participants. Compared to the negative control, adhesive 1 showed a statistically significantly higher bite force AOB over 12 hours (AOB_0-12h; primary endpoint), as well as for AOB_0-6h and AOB_0-9h (all P .05), but not for AOB_0-1h or AOB_0-3h. Adhesive 2 was not significantly different from the negative control or from adhesive 1 for any measure of AOB. The positive control was associated with a significantly higher bite force AOB than either of the experimental adhesives for all time points (P .05). Although the positive control was well tolerated, both experimental adhesives were associated with a larger number of oral adverse events. Conclusion: Only adhesive 1 was significantly better than the negative control, and its performance did not match that of the positive control. Adhesives 1 and 2 showed the largest number of oral adverse events.

Purpose: To compare the clinical outcomes of screw-retained vs cemented single crowns supported by customized zirconia abutments on implants. Materials and Methods: Thirtytwo patients received implant-supported (Regular Neck, Tissue-Level, Straumann AG), single-tooth restorations with customized zirconia abutments in the anterior areas. Participants were randomly assigned to the screw-retained (full-crown abutment [FCA]) group or the cemented (zirconia crown [ZrC]) group and followed up over a 10-year period. Prosthetic and biologic complications, marginal bone level (MBL), mucosal recession, and pink and white esthetic scores (PES and WES, respectively) were evaluated. Results and Conclusion: There were no implant failures during the study period; after 10 years, 94% of crowns were functional. Prosthetic complications were recorded in both groups (three FCA and two ZrC), and no significant difference was found (P = .65). Two cases of mucositis were recorded, one in each group. Esthetic outcomes were assessed using PES and WES scores. MBL was 0.95 mm in the ZrC group and 0.82 mm in the FCA group, with no significant difference between groups. These encouraging preliminary results need to be confirmed with long-term follow-up on larger study samples.

Purpose: To evaluate the influence of cobalt-chromium (Co-Cr) casting alloys' melting temperatures on the cast-to Co-Cr implant cylinders' marginal fit. Materials and Methods: Co-Cr alloys with different melting ranges were cast into 20 Co-Cr cylinders: 10 in a high-melting temperature (HMT) group and 10 in a low-melting temperature (LMT) group. Ten cylinders were used as received as a control group. Cylinders' marginal misfit and dimensional stability were evaluated using scanning electron microscopy (×500). Results and Conclusion: HMT cylinders showed significant differences in marginal misfit (2.48 ± 1.07 μm2) compared to LMT (1.53 ± 0.37 μm2) and control (1.27 ± 0.57 μm2) cylinders, but there were no differences in dimensional stability. HMT Co-Cr alloys produce implant-supported prostheses with poor marginal fit.

Purpose: To clarify the relationship between residual ridge morphology and pressure distribution of the alveolar bone surface during dental impression procedures. Materials and Methods: Seven experimental models of the mandibular posterior residual ridge with the same ridge morphology but different mucosa (ie, silicone material) thicknesses and bone (ie, plaster) shapes and sizes were fabricated. The pressure on the bone surface was recorded using a pressure sensor sheet. The data from each model were compared using the Kruskal-Wallis test, and P .05 was considered statistically significant. Results: Even with the same ridge morphology, the distribution of the impression pressure on the bone surface differed according to the mucosal thickness and bone shape and size. Pressure tended to concentrate on sharp edges and prominences of a slope and became more widely distributed as the mucosal thickness increased. Conclusion: Within the limitations of this experimental study, the morphology of the residual alveolar ridge (bone and mucosa) appears to be a significant influencing factor for the pressure distribution during impression procedures.

Purpose: To investigate the impact of software version on the accuracy of an intraoral scanning device. Materials and Methods: A master tooth was scanned with a highprecision optical scanner and then 10 times with a CEREC Omnicam scanner with software versions 4.4.0 and 4.4.4. Discrepancies were measured using quality control software. Results: Mean deviation for 4.4.0 was 36.2 ± 35 μm and for 4.4.4 was 20.7 ± 14.2 μm (P ≤ .001). Conclusion: Software version has a significant impact on the accuracy of an intraoral scanner. It is important that researchers also publish the software version of scanners when publishing their findings.

Intraoral scanning was used to capture the soft tissue surfaces of both maxillary and mandibular edentulous ridges and the denture borders. Additionally, an intraoral scanner was used to digitize existing dentures with their tooth positions and base forms and a centric relation record obtained with a Gothic arch-tracing device. These scans provided all the required records for fabrication of computer-aided design/computer-assisted manufacturing of complete dentures.

Purpose: To evaluate the long-term effects of preventive measures against denture fracture using clinical surveys of denture fracture cases from 1984 and 2009. Materials and Methods: This study included 128 patients who presented with a chief complaint of denture fracture and received denture repair treatment in 2009. The following data were collected: denture repair procedure; location of denture base fracture (with or without reinforcement); and period of denture use from insertion to repair. Significant differences in characteristics between patients treated in 1984 and 2009 were determined using the chi-square test (P .05). Results: In 2009, denture fractures comprised 55.5% of all repair cases. The most frequent location of denture fracture was around the clasp and metal in the denture base. Approximately 45% of all dentures were reinforced. The mean period from denture insertion to repair was 37 months. The number of denture fractures significantly decreased between 1984 and 2009 (P .05), and the number of dentures with reinforcement significantly increased (P .05). The mean period from denture insertion to repair also increased. Conclusion: These findings suggest that denture reinforcement as a preventive measure is effective against denture fracture, allowing patients to use their dentures more effectively.

Purpose: To evaluate the internal adaptations of cast crowns made from resin patterns produced using three different computer-aided design/computer-assisted manufacturing technologies. Materials and Methods: A full-crown abutment made of zirconia was digitized using an intraoral scanner, and the design of the crown was finished on the digital model. Resin patterns were fabricated using a fused deposition modeling (FDM) 3D printer (LT group), a digital light projection (DLP) 3D printer (EV group), or a five-axis milling machine (ZT group). All patterns were cast in cobalt-chromium alloy crowns. Crowns made from traditional handmade wax patterns (HM group) were used as controls. Each group contained 10 samples. The internal gaps of the patterns were analyzed using a 3D replica method and optical digitization. The results were compared using Kruskal-Wallis analysis of variance (ANOVA), a one-sample t test, and signed rank test (α = .05). Results: For the LT group, the marginal and axial gaps were significantly larger than in the other three groups (P .05), but the occlusal adaptation did not reveal a significant difference (P > .05). In the ZT group, the axial gap was slightly smaller than in the HM group (P .0083). All the means of gaps in all areas in the four groups were less than 150 μm. Conclusion: Casting crowns using casting patterns made from all three CAD/ CAM systems could not produce the prescribed parameters, but the crowns showed clinically acceptable internal adaptations.

Purpose: To explore the influence of perfectionism on the short-term changes in satisfaction with smile esthetics and quality of life (QoL) induced by tooth whitening. Materials and Methods: A total of 60 subjects were analyzed: 30 in the active group, in which the subject's anterior teeth were whitened with a photoactivated gel, and 30 in the placebo group. The Smile Esthetics-Related Quality of Life and Multidimensional Perfectionism Scale questionnaires were administered to all participants. Results: The active group demonstrated an increase in dental self-confidence and a decrease in dissatisfaction with color (P .05). The amount of color change did not correlate linearly with change in dissatisfaction or with QoL. In subjects with higher perfectionism, increasing the color change led to more decrease in dental self-consciousness. Conclusion: Perfectionism moderates perception of smile esthetics.

Purpose: To evaluate the effect of premolar axial wall height on the retention of adhesive, full-coverage, computer-aided design/computer-assisted manufacture (CAD/CAM) restorations. Materials and Methods: A total of 48 premolar teeth randomized into four groups (n = 12 per group) received all-ceramic CAD/CAM restorations with axial wall heights (AWH) of 3, 2, 1, and 0 mm and 16-degree total occlusal convergence (TOC). Specimens were restored with lithium disilicate material and cemented with self-adhesive resin cement. Specimens were loaded to failure after 24 hours. Results: The 3- and 2-mm AWH specimens demonstrated significantly greater failure load. Failure analysis suggests a 2-mm minimum AWH for premolars with a TOC of 16 degrees. Conclusion: Adhesive technology may compensate for compromised AWH.

Although digital technology has advanced the visualization of treatment planning and rehabilitation in prosthodontics, the field of maxillofacial prosthetics is in vital need of an accessible document for exchange of interactive three-dimensional (3D) model visualization without requiring installation of any additional software. This article introduces a 3D data documentation method for effective interactive digital visualization in maxillofacial prosthetics using a portable documentation format (PDF).