The International Journal of Prosthodontics, 02/2020

Purpose: To assess the correlation between RDC/TMD Axis I and Axis II diagnoses and whether pain could mediate a possible correlation between these two variables. Materials and Methods: Data of both RDC/ TMD axes were collected from 737 consecutive patients who sought TMD advice at the University of Padova, Italy. A descriptive analysis was used to report the frequencies of Axis I and II diagnoses, and Spearman test was performed to assess the correlation between the axes. Subsequently, the sample was divided into two groups (painful vs nonpainful TMD). Frequencies were reported using descriptive analysis, and chi-square test was used to compare groups. The painful TMD group was then divided based on the level of painrelated impairment (low = Groups I and II; high = Groups III and IV). Then, frequencies of depression and somatization were reported using descriptive analysis for each disability group, and chi-square test was used to compare groups. Results: No correlation levels were found between Axis I and any of the Axis II findings (Graded Chronic Pain Scale, depression, and somatization). The painful TMD group presented higher levels of depression and somatization (P < .05). Comparisons of depression and somatization frequencies between pain-impairment groups showed a significantly higher prevalence of abnormal scores for the severe painimpairment group. Conclusion: There is no correlation between specific Axis I and Axis II findings. The presence of pain, independent of the muscle or joint location, is correlated with Axis II findings, and higher levels of pain-related impairment are associated with the most severe scores of depression and somatization.

Purpose: To evaluate the clinical outcomes of monolithic CAD/CAM–fabricated polymer-infiltrated ceramic network (PICN) single crowns (SC) after 3 years. Materials and Methods: A total of 34 patients who received 76 single crowns were included in this cohort study. Full-coverage crown preparation with reduced thickness (1.0 to 1.5 mm) was applied. All monolithic PICN SCs (VITA Enamic) were manufactured using a CAD/CAM system and adhesively seated. Clinical follow-up evaluations were performed at 6, 12, 24, and 36 months after insertion using modified United States Public Health Service (USPHS) criteria. Kaplan-Meier survival and success methods were applied to calculate absolute and relative failures. To determine effects of time and restoration, a mixed logit model was adjusted for the modified USPHS criteria (P < .05). Results: PICN SCs revealed an estimated Kaplan-Meier survival rate of 93.9% after 3 years. Four clinically unacceptable fractures occurred, which resulted in replacement of the affected SCs. Neither secondary caries nor debonding were recorded. The 3-year Kaplan-Meier success rate was 92.7%. Significant increases in marginal discoloration (P = .0002) and surface roughness (P < .0001) were noted over time. Color match, anatomical form, and marginal adaptation remained favorable over the given observation period. Conclusion: PICN CAD/CAM crowns with reduced thickness showed acceptable survival and success rates over a service time of 36 months. However, extended clinical follow-up periods are needed to evaluate the long-term performance.

Purpose: To investigate the long-term (up to 20 years) outcomes of customized post copings (PC) and to evaluate potential factors influencing the risk for complications. Materials and Methods: Patients treated with PC-retained overdenture prostheses (OD) in a university setting were selected. Data collected included dental and periodontal parameters, periapical radiographs, and assessment of the OD design. Patientreported satisfaction levels were evaluated using visual analog scales (VAS), and 20-year cumulative survival and success rates were calculated. Results: A total of 73 patients with 81 ODs and 152 PCs were included. PC survival rate was 80.9%, and the success rate amounted to 64.5% after a mean observation period of 105.4 (± 67.9; range: 6 to 240) months. The 20-year cumulative PC rates were 91.5% for survival and 79.3% for success. Activation of matrices was more frequent with ball attachments than with cylindrical retention (odds ratio [OR] 0.43; 95% confidence interval [CI] 0.2 to 0.94; P = .034). Cylindrical retention was rated significantly better at 96% (interquartile range [IQR] 89.5% to 100%) compared to ball attachment at 88% (IQR 79% to 98.2%; P = .012). The risk for PC complications was higher for OD designs with coverage of the periodontal tissues compared to open designs (OR 0.34; 95% CI 0.15 to 0.78; P = .010). Conclusion: Customized PCs on natural abutment teeth for the retention of ODs are a valid treatment in partially dentate patients. Correct prosthesis design and integration into a regular dental hygiene program are mandatory factors for long-term success.

Purpose: To evaluate the survival and success rates of post-and-core restorations supporting fixed dental prostheses (FDPs) after a mean time in function of 7 years and to assess the incidences of biologic and technical complications. Materials and Methods: Patients from the National Dental Center Singapore (NDCS) with endodontically treated premolars restored with post-retained FDPs from 2007 to 2009 were recruited from the Endodontic Registry and evaluated by three clinicians. A total of 265 patients with 329 treated premolars were examined clinically. Digital radiographs were also obtained. Complications were classified as tooth- or prosthesis-related. Failure and complication rates were calculated based on person-time-at-risk. Results: The mean time in function was 7.1 years. A total of 25 teeth in 23 patients were lost, resulting in a 7-year survival rate of 92.7% (95% CI: 89.5%, 95.0%). The corresponding success rate was 75.1% (95% CI: 70.5%, 79.1%). A total of 40 FDPs failed, resulting in a 7-year prosthetic survival rate of 88.6% (95% CI: 84.8%, 91.5%). Common complications observed were recurrent periodontal disease (3.9%), periapical pathology (7.3%), caries (3.9%), porcelain chipping (9.9%), and tooth fractures (5.0%). For the incidence of tooth fracture, a risk analysis yielded significant associations with the number of occluding teeth (odds ratio: 4.2; 95% CI: 1.1, 16.7) and the number of adjacent teeth (odds ratio: 4.0, 95% CI: 1.5, 10.9). Conclusion: Restoration of premolar teeth requiring root canal treatment with a post and core and crown is a viable treatment when premolar teeth have adjacent teeth.

Purpose: To analyze the current evidence on bone loss in the posterior edentulous mandible restored with complete dentures (CDs), two-implant–supported overdentures (2-IODs), or four-implant–supported overdentures (4-IODs). Materials and Methods: A search was conducted in the Ovid MEDLINE, Embase, Web of Science, CINAHL, and Cochrane databases for clinical studies comparing bone loss in posterior edentulous mandibles restored with CDs, 2-IODs, or 4-IODs. A meta-analysis was performed using statistical software to estimate the mean differences in bone loss with 95% CI. The level of significance was set at P < .05. Results: The search strategy identified 2,806 articles, of which 14 met the inclusion criteria. The meta-analysis included 7 two-arm studies comparing CDs vs 2-IODs or 2-IODs vs 4-IODs. No statistically significant difference was found in bone loss between 2-IODs and CDs (mean difference –0.25 [95% CI –0.85 to 0.36]; P = .43), whereas bone loss was significantly lower with 4-IODs than with 2-IODs (mean difference –0.96 [95% CI –1.86 to –0.06]; P = .04). Overall, the data were highly heterogenous (I2 > 74%). Conclusion: 4-IODs can benefit the patient by decreasing bone loss in the posterior edentulous mandible. However, 2-IODs may not be superior to CDs in reducing bone loss in the posterior mandible. A validation of these results is needed through well-designed RCTs.

Purpose: To determine the accuracy of direct digital impressions in vivo and compare it to that of conventional impressions in order to assess whether intraoral scanners could be a legitimate alternative for the manufacturing of fixed prosthodontics. Materials and Methods: An electronic systematic search was conducted in the PubMed, Web of Science, Embase, and Cochrane Library databases using query terms such as digital impression; intraoral digital impression; intraoral scanner; intraoral digital scanner; conventional impression; analogue impression; and accuracy. The outcomes were the trueness and precision of digital impressions in comparison to those of high-precision conventional impressions in vivo. Results: Six studies matched the inclusion criteria. Four studies investigated the precision of digital impressions, while two studies focused on their trueness. Even if all the authors agreed that conventional impressions were more accurate than digital impressions in vivo, they gave different opinions on using intraoral scanners in a clinical context without causing misfit of the final restoration. Conclusion: According to the results of the present review, conventional impressions performed using high-precision impression materials showed greater accuracy than digital impressions. However, additional studies assessing the accuracy of digital impressions in a wider variety of clinical situations are highly recommended.

Purpose: To evaluate the amount of residual cement (ECL) around the margins of zirconia crown copings after careful luting and cleaning procedures and to investigate these factors in relation to two tested luting materials. Materials and Methods: An experimental model of a maxillary arch was selected for this in vitro study. The maxillary first molar was prepared to receive an all-ceramic, single, full-crown restoration with a finish line located 1 mm below the artificial gingiva. After scanning of the prepared tooth, 20 paired zirconia coping–abutment assemblies were CAD/CAM fabricated. A slot in the model allowed for insertion and removal of the assemblies for each new test. Specimens were divided into two groups according to the cementation procedure: half (n = 10) were luted using a resin-modified glass-ionomer (RMGI) (Ketac-Cem Plus) (GI group), and the other half with a dual-curing self-adhesive resin agent (RelyX Unicem 2) (UN group). The substructures were loaded with cement, and a customized preseating device was adopted for preliminary reduction of excess. The zirconia copings were finally seated on their respective abutments located on the simulation model. A blinded investigator attempted to remove all excess cement with clinically available instruments. The amount of excess cement left in situ after cleaning procedures was weighed in grams. Dislodging forces of luted coping-abutment assemblies were obtained by using pull-off tests in a universal testing machine (crosshead speed of 0.5 mm/minute) after 24 hours of water storage. Means and standard deviations were calculated for ECL and for retention force values, and Mann-Whitney and ANOVA tests were carried out to detect significant differences (α = .05) among groups. Results: Cement remnants were found in all specimens despite the cleaning procedures, with a typical distribution in interproximal areas. Mean ECL values for the GI and UN groups were 0.0079 ± 0.0060 and 0.0107 ± 0.0081, respectively. No statistically significant differences were found between tested cements (P = .3284). Removal stress values (MPa) were significantly higher (P = .0313) for the UN group (12.4 ± 6.5) than for the GI group (6.57 ± 4.69). Conclusion: Similar amounts of undetected cement remnants were discovered around the esthetic margins of zirconia crown copings regardless of cement type. The luting procedure using the self-adhesive resin cement provided significantly higher early retention values than the RMGI material.

Purpose: To evaluate the effect of different concentrations of hydrofluoric acid (HF) on the surface roughness of a ceramic reinforced by lithium disilicate and on the bond strength formed between the ceramic and self-adhesive resin cement. Materials and Methods: A total of 100 disks of IPS e.max Press ceramic (Ivoclar Vivadent) reinforced by lithium disilicate were prepared as follows: group 1 remained untreated (control group); in groups 5-20, 5-40, and 5-60, the surfaces were etched with 5% HF for 20, 40, and 60 seconds, respectively; in groups 10-20, 10-40, and 10-60, the surfaces were etched with 10% HF for 20, 40, and 60 seconds, respectively; and in groups 10-20P, 10-40P, and 10-60P, the surfaces were etched with 10% HF for 20, 40, and 60 seconds, respectively, followed by treatment with 37% phosphoric acid for 5 seconds. Surface roughness and bond strength were analyzed with confocal microscopy and microshear testing, respectively. The values obtained were statistically analyzed using paired t test and two-way ANOVA followed by Tukey post hoc test at a 5% significance level. Results: Surface roughness was influenced by the concentration and exposure time of acid applied (P < .05) and by the combination of these two factors (P < .05). Treatment with 10% HF for 40 seconds (group 10-40) achieved the highest roughness value. In contrast, bond strength was affected only by the acid exposure time (P < .05). Conclusion: Conditioning of lithium disilicate ceramics can change the surface morphology, thereby affecting bond strength with resin cement.

Purpose: To evaluate the surface roughness values of zirconium oxide samples that were gradually polished using a commercially available polishing system and polishing paste. Materials and Methods: A total of 50 rectangular specimens of predetermined size (10 × 10 × 3 mm) were sintered from zirconium oxide. Samples were randomly assigned to one of five groups (n = 10 each): control, coarse (Co), fine (F), super fine (SF), or polishing paste (PP). In the control group, no polishing was done; in the Co group, a coarse polisher was used; and the specimens in the remaining three groups underwent additional processing with a fine rubber abrasive. For SF and PP samples, subsequent treatment with a super fine polisher was applied. Finally, for the PP group, a goat-hair brush with diamond polishing paste was used. An optical profilometer was used to evaluate roughness average (Ra) in micrometers (μm). ANOVA and Games-Howell post hoc tests were utilized to detect differences between groups. The significance level was set to α = .05. Results: Surface roughness gradually decreased with further polishing throughout the groups: control Ra = 0.525 ± 0.099 μm; Co Ra = 0.252 ± 0.038 μm; F Ra = 0.196 ± 0.035 μm; SF Ra = 0.114 ± 0.031 μm; and PP Ra = 0.054 ± 0.020 μm. Statistically significant differences were detected among all groups (P < .05). Conclusion: A surface roughness of 0.054 μm can be achieved if a full zirconia polishing protocol is used. Zirconium oxide can be polished to various surface roughnesses using commercially available polishing products.

Purpose: To develop a new digital method for color-mixing analysis and to evaluate the validity of this method for quantifying masticatory performance. Materials and Methods: Specimens of red-green (RG) chewing gum were prepared as a bicolor test food. A total of 300 specimens were masticated by 20 healthy volunteers for different numbers of mastication cycles (from 1 to 25). The boluses were flattened and scanned, and the digital images were analyzed using ImageJ software. Two parameters (spatial and value) of color mixing were measured, and multiple regression analysis was performed to estimate the number of mastication cycles. The estimated number of mastication cycles that the healthy reference cohort needed to achieve a certain degree of color mixing was proposed as the mastication index (MI). The validity of this method was assessed using Pearson correlation between the MI and concurrent measurements with ViewGum software (variance of hue) within a group of 10 healthy subjects and 10 complete denture wearers. Results: Independent samples t test showed a significant difference in MI between healthy subjects and denture wearers (P < .001). A significant correlation was observed between the MI and ViewGum outcomes (r = −0.95, P < .001). Conclusion: The new proposed method proved to be valid and has the potential for evaluating masticatory performance in both research and clinical settings.

Currently, 3D printers, especially digital light processing (DLP) printers, are widely used in clinical dentistry. However, due to the shrinkage property of resin, their accuracy is not optimal for full-arch dental model printing. To overcome these limitations, fused deposition modeling (FDM) with filament that undergoes minimum shrinkage was introduced. Accordingly, a combination of FDM printing with the specific tooth die output of DLP printing for the full-arch dental model is proposed in the present report.

Milling complete dentures is becoming a popular option for clinicians because subtractive technology can make the fabrication of high-quality dentures faster and easier. Additive technology is one of the newest techniques for making complete dentures, and its primary advantage is that a printer is more financially accessible than a milling machine. Printing and milling technologies as methods for denture fabrication have similar steps and time frames for their processes. The production of immediate complete dentures also follows similar procedures for both systems. The aim of this article is to compare subtractive and additive technologies for the manufacture of immediate complete dentures and to present two case reports.