The International Journal of Prosthodontics, 02/2022

Purpose: To evaluate the survival rates and technical outcomes of minimally invasive full-mouth rehabilitations in patients affected by dental erosion and attrition. Materials and Methods: For this retrospective study, 28 subjects (8 women, 20 men; mean age: 45.6 years) who suffered from generalized erosions and attrition and who were treated according to the 3-step technique were invited to participate. The patient records were reviewed, and the restorations were clinically and radiographically examined. This part of the study (Part 1) evaluated restoration survival and technical outcomes using the modified United States Public Health Service criteria (mUSPHS). Survival analysis was performed using Kaplan-Meier survival statistics, and comparison between subgroups was made using log-rank test. For all other comparisons, cross tabulations of occurrence were performed, and significance was tested using Pearson chi-square test. The level of statistical significance was set at P < .05. Results: A total of 19 patients (3 women, 16 men; mean age: 45.6 years) agreed to participate. In these patients, 406 restorations (149 direct composites, 110 onlays, 147 veneers) supported by 365 teeth were examined. The mean time in service was 71.8 ± 28.6 months. Six failed restorations were identified; all were direct composites. The 6-year survival rates were 97.3% for direct composites, 98.2% for onlays, and 100% for veneers (P > .05). No differences were found among materials or locations of the restorations. Nineteen technical complications included 14 partial fractures, 3 fissures, 1 wear, and 1 decementation. The mUSPHS evaluation showed good technical outcomes. Presence or absence of a nightguard influenced restoration survival (P = .003). Conclusion: Minimally invasive rehabilitations of patients with erosions/attrition with the 3-step technique are a reliable treatment option in the medium term. Protective nightguards are recommended.

Purpose: To evaluate biologic and esthetic outcomes, as well as the patient-reported outcome measures (PROMs), of full-mouth rehabilitations in patients suffering from generalized erosive and/or abrasive tooth wear following the 3-step technique. Materials and methods: Patients who received a minimally invasive full-mouth rehabilitation according to the 3-step technique and who were treated at the University of Geneva and/or in a private practice were considered for inclusion. The minimum service time of the restorations was 12 months. The biologic outcomes were analyzed by assessing pocket probing depth (PPD), Plaque Index (PI), and bleeding on probing (BOP). Furthermore, secondary caries, tooth vitality, and sensitivity to temperature were evaluated using the modified United States Public Health Service (USPHS) criteria. The esthetic outcomes were rated with the White Esthetic Score (WES). Finally, PROMs were evaluated using visual analog scales (VAS). Results: A total of 19 patients with 406 restorations (149 direct composite resins, 110 indirect composite resin/ceramic onlays, and 147 composite resin/ceramic veneers) were examined after a mean follow-up of 71.8 ± 28.6 months. Periodontal parameters were good (mPPD = 2.9 ± 0.4; mPI = 0.1 ± 0.2; and mBOP = 0.05 ± 0.1). No secondary caries were found, and no abutment tooth had lost vitality. A total of 36 abutment teeth had moderate sensitivity, but none presented pronounced sensitivity. The rehabilitations exhibited good esthetic outcomes (mWES = 8.4 ± 1.9). Patients reported satisfying esthetic results of their rehabilitations (mean VAS = 9.2 ± 1.6) and considered their treatment as comfortable (mean VAS = 8.2 ± 2.1), while the least favorably rated parameter was the cost of treatment (mean VAS = 4.1 ± 3.2). Conclusion: Minimally invasive full-mouth rehabilitations of patients with generalized tooth wear by means of the 3-step technique exhibit very good clinical medium-term results with respect to biologic and objective/subjective esthetic outcomes. The patient satisfaction with this treatment was high.

Purpose: To assess the effect of stabilization splint (SS) thickness on temporomandibular disorders (TMDs). Materials and Methods: Participants were selected from patients who applied to the clinic with a complaint of temporomandibular disorders (TMDs). Symptoms were evaluated with the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD). Regarding the treatment plan, patients were divided into two groups: the 2-mm–thick splint group (2-mm TSG) and the 4-mm–thick splint group (4-mm TSG). They used SSs at night (8 hours) and were recalled 1, 2, 3, and 6 months after splint insertion. At the end of the study, 72 patients (2-mm TSG = 39, 4-mm TSG = 33) had completed the 6-month follow-up. The SPSS program was used for statistical analysis. The results of the analysis were evaluated at a significance level of .05. Results: Pain in the muscles decreased significantly in the muscle disorders and combined groups (both 2- and 4-mm TSG) after 6 months of treatment (P < .05). In the combined group, TMJ sounds significantly decreased after 6 months of treatment, and there was a statistically significant difference between the 2-mm TSG and the 4-mm TSG (P = .045). Also, in the combined group, maximum unassisted opening (MUO) values of patients treated with 2-mm–thick splints decreased after 6 months of treatment (P = .022). Conclusion: Both 2-mm–thick and 4-mm–thick splints were effective in the treatment of muscle disorders and disc displacements, especially in muscle-related pain and TMJ sound symptoms.

Purpose: To compare osteocalcin and crestal bone loss in implants placed under an immediate loading (IL) compared to a delayed loading (DL) protocol. Materials and Methods: This preliminary, split-mouth, randomized controlled trial included 14 participants who required replacement of both mandibular first molars opposing a completely dentate maxillary arch. Two implants were placed in each participant. According to the split-mouth randomization method, a temporary crown was used for the IL protocol and a healing abutment was used for the DL protocol in each participant. Definitive crowns were cemented 3 months after implant placement. Osteocalcin levels were determined using ELISA, and crestal bone loss was evaluated using radiographs at 2 weeks, 3 months, and 12 months after implant placement. Results: The mean osteocalcin level was significantly higher with IL than DL at each point (P < .001), with 95% CI of –262.89 to –439.10 (2 weeks); –238.02 to –375.98 (3 months); and –83.24 to –211.61 (12 months). Higher crestal bone loss was observed in IL when compared to DL implants at 2 weeks (P = .458, 95% CI: –0.10 to 0.21). Less crestal bone loss was observed with IL than DL at 3 months (P = .935) and 12 months (P = .42). Conclusion: Osteocalcin levels increased in both IL and DL implants, but higher levels were observed with IL. Higher crestal bone loss was observed with IL during the initial stages of treatment only.

Purpose: To determine whether a significant dimensional difference in labial soft tissue could be produced by maxillary anterior tooth restorations with diverse labial thicknesses. Materials and methods: Changes in the contour of the lips in each participant produced by provisional restorations with different labial thicknesses (1-4 mm) compared to baseline (0 mm) were assessed using 3D software and using a visual analog scale by a group of prosthodontists and a group of laypeople. Results: Significant enhancements in 3D deviation compared to baseline were present when the participants were wearing the labial provisional restorations. Negative correlations for labial thickness with nasolabial angle and distance from upper lip to E-plane measurements were found. However, the changes were most pronounced for the prosthodontist and laypeople groups when the labial veneer thickness was 2 mm or more. Conclusion: Prosthodontists and laypeople hardly recognized the lip profile changes when labial provisional restorations were below 2 mm. Therefore, restorations with limited labial thickness had a weak esthetic impact on lip morphology.

Purpose: To evaluate the microshear bond strength (μSBS) of different bonding protocols to commercially pure titanium (CP Ti) using two universal adhesives and Alloy Primer. Materials and Methods: A total of 120 cubes of CP Ti were airborne-particle abraded and then divided into 6 groups (n = 20 each) according to bonding protocol: (1) Scotchbond Universal (SU; 3M Espe), (2) Alloy Primer (AP; Kuraray) + SU; (3) G-Premio Bond (GP; GC); and (4) AP + GP. The specimens from groups 1 to 4 were cemented with RelyX Unicem (3M Espe), while those from groups 5 and 6 were cemented using Panavia F2.0 cement (PAN; Kuraray) without and with prior AP application, respectively. After 24 hours, half of the specimens were subjected to μSBS measurement and the other half to thermocycling (5,000 cycles) before testing. Data were analyzed using Shapiro-Wilk, two-way analysis of variance, Games-Howell, and independent samples t test (α = .05). Results: The μSBS values obtained from the AP + SU group were significantly higher than from the GP (P = .003) and the AP + GP (P = .022) groups. After thermocycling, the μSBS of both groups treated with SU were significantly higher than those of other groups (P < .001). The application of AP did not improve adhesion of resin cements to CP Ti. Thermocycling significantly reduced the μSBS values of the PAN group, whereas it noticeably enhanced the adhesion of SU and AP + SU. The predominant failure mode in all groups was adhesive. Conclusion: The application of AP, followed by SU, produced the most effective bonding to CP Ti, which was able to endure limited thermal aging.

Purpose: To test the push-out force and marginal leakage of different screw hole-sealing methods in monolithic zirconia implant crowns. Materials and methods: Ninety monolithic zirconia (Prettau, Zirkonzahn) specimens were milled with two different screw access hole designs: conventional smooth hole or threaded screw hole (for group PMMA-SC), and divided into five groups (n = 18) according to filling method: unbonded composite (UBC); bonded composite (BC); airborne-particle abrasion of screw hole and unbonded composite (ABR-UBC); airborne-particle abrasion of screw hole and bonded composite (ABR-BC); and PMMA screw plugs (PMMA-SC). Twelve specimens per group were subjected to static push-out force with a universal testing machine. Before testing, 6 specimens per group were stored in dry conditions, and 6 were kept in water storage (+37°C) for 7 days. For the remaining specimens (n = 6), cotton pellets were placed under the screw access hole fillings, and the specimens were immersed in 0.5% basic fuchsin solution for 2 weeks. Dye in cotton pellets was dissolved in 2 mL of water, and absorbances of the solutions were measured with a spectrophotometer at 465 nm. Data are reported as mean and SD. Statistical analysis was made using a generalized linear model with logarithmic transformation. Results: PMMA-SC specimens showed the highest push-out forces (P < .0001) and lowest fuchsin penetration (P = .009). Airborne-particle abrasion increased the push-out force and decreased the microleakage in composite groups. The storage conditions affected the results of both unbonded groups. Conclusion: The design and sealing method of the screw access hole affect push-out force and microleakage.

Purpose: To assess the shear bond strength of composite resin to poly(etheretherketone) (PEEK) after mechanical and chemical surface treatments. Materials and Methods: A total of 48 PEEK discs were fabricated and divided equally into four surface treatment groups (n = 12 each): (1) airborne-particle abrasion (APA) with 50-μm alumina particles at 2-MPa pressure for 10 seconds; (2) 98% sulfuric acid etching for 1 minute; (3) APA + sulfuric acid etching; and (4) no surface treatment. Specimens were conditioned, and then veneering composite resin was applied to the PEEK surfaces and polymerized. Bond strength was measured using a universal testing machine. One-way analysis of variance and Tukey post hoc test were applied for statistical analysis. Results: The mean shear bond strength values of the sulfuric acid etching group were higher than that of the APA + acid etching, APA, and control groups (P < .05). Mean shear bond strength values for the APA + acid etching samples were higher than for the control and APA groups (P < .05). Conclusion: There was no significant difference between the samples treated with APA and the control group. The bond strength was highest when PEEK was prepared with sulfuric acid etching alone.

Purpose: To investigate the volumetric facial soft tissue changes associated with wearing complete dentures using 3D facial scans. Materials and Methods: A total of 40 volunteers (20 men and 20 women) were recruited for this study and were treated with maxillary and mandibular complete dentures. Six facial scans were taken of each subject; three scans wearing a complete denture and three without the complete denture. The 3D facial scans were taken with the mouth in three positions: closed, relaxed, and smiling. Each scan was superimposed in order to analyze and quantify linear measurements involving 14 soft tissue landmarks and the total volume that the subject gained with the prosthesis. Results: Three variables were evaluated in each analysis: gender, mouth position, and age. In the analysis of the soft tissue landmarks, there was a significant effect of age, with patients > 75 years showing the greatest changes (P < .05). The landmarks that showed the most changes were those located around the mouth. In the volumetric analysis, the variable with the highest influence was gender, with men gaining more volume than women (P < .05). Conclusion: Complete dentures have a significant effect on volumetric changes in perioral tissues. These changes are more marked in patients > 75 years. Compared to women, men depicted greater volumetric changes with complete dentures. These results provide a new avenue for clinicians and developers using facial scans to design future restorations for edentulous patients.

Purpose: To investigate whether viewing distance influences the results of visual tooth color differentiation. Materials and methods: A total of 65 students underwent both theoretical and practical training by a standardized lecture on the use of an internet learning module (Toothguide Trainer, VITA Zahnfabrik) and a standardized training program (Toothguide Training Box) for visual shade-taking. Each student matched 10 randomly selected shade tabs presented at different viewing distances (arm's length distance [AL, 70 cm] and AL/2 [35cm]) under lateral, non-glare lighting at a 45-degree angle with a color differentiation lamp. The results were recorded as to what extent the presented and selected tabs of the color determination matched. Results: The overall median values of perceived color difference (ΔE) were 1.6 for AL/2 and 3.2 for AL, and these values were significantly different (P < .001). Conclusion: Within the limitations of this study, it was shown that the viewing distance had a significant influence on the color deviation in tooth color assessment. Therefore, a smaller viewing distance of 35 cm for shade determination is recommended.

Purpose: The purpose of this exploratory in vitro study was to compare and evaluate the load-bearing capacity (LBC) of ceramic-veneered zirconia and composite-veneered polyetheretherketone (PEEK) three-unit fixed dental prostheses (FDPs) with and without thermocycling (TC). Materials and methods: The study included 40 samples of three-unit FDPs replacing mandibular first molars. The four groups included were: ceZIR (feldspathic ceramic-layered zirconia), ceZIR TC (feldspathic ceramic-layered thermocycled zirconia), cPEEK (composite-layered PEEK), and cPEEK TC (composite-layered thermocycled PEEK) (n = 10 per group). All frameworks were CAD/CAM milled. Ten PEEK and 10 zirconia samples were subjected to TC (6,000 cycles). All 40 FDP specimens were loaded by applying static load, using a universal testing machine. The maximum load required to fracture the specimens denoted the LBC. The comparison of LBC between the four groups was done by using two-way ANOVA with Tukey's post-hoc analysis (α = .05). Results: There was no statistically significant difference between LBC of cPEEK and ceZIR (P > .001) without thermal aging. LBC values decreased considerably for thermally aged specimens. Statistically significant differences were observed between LBC of cPEEK TC and ceZIR TC (P < .001), cPEEK TC and cPEEK (P < .001), and ceZIR TC and ceZIR (P = .001). On fracture analysis, cPEEK showed delamination failures whereas ceZIR displayed catastrophic connector fractures. Conclusion: This comparative evaluation offers preliminary data highlighting substantial depreciation in the LBC of layered PEEK under simulated intraoral conditions, thus raising a question regarding the clinical longevity of layered PEEK multi-unit restorations. In contrast, feldspathic-layered zirconia can be suitable for use in posterior FDPs.

Purpose: To evaluate whether intraoral devices reduce the adverse oral and dental effects of radiotherapy in head and neck cancer patients. Materials and Methods: A systematic search of the Medline and Embase databases for articles published before March 2019 was performed by two independent reviewers. Studies published in English that evaluated whether intraoral devices reduced the risk of radiotherapy-related complications in patients receiving radiotherapy in the head and neck region were included. The kappa statistic was used to calculate the level of inter-reviewer agreement. Results: Five studies met the inclusion criteria, although only one was considered to be a low risk of bias. One study reported that intraoral devices did not reduce the severity of mucositis after 7 weeks. The remaining four studies reported that intraoral devices reduced the risk of xerostomia, mucositis, trismus, dysphagia, and dental caries over 2 to 6 months. Conclusion: There are limited data to support the use of intraoral devices in head and neck cancer patients undergoing radiotherapy. Well-designed clinical studies that consider long-term outcomes are necessary to draw definitive conclusions.

Purpose: To evaluate and compare the impact strength of 3D-printed resin to conventionally fabricated denture bases of heat-cure and cold-cure acrylic resin. Materials and Methods: Denture base materials were evenly divided into three groups (n = 25 each; N = 75): (1) 3D-printed material (Denture Base LP, Formlabs Dental); (2) Heat-cure acrylic resin (Lucitone 199, Dentsply Sirona); and (3) cold-cure acrylic resin (Lucitone HIPA, Dentsply Sirona). The 3D-printed specimens were designed with the dimensions 64 × 12.7 × 3.2 mm using computer-aided design software, then printed with a desktop stereolithography printer (Form 2, Formlabs). Heat-cure and cold-cure acrylic resin specimens were fabricated through conventional (compression and pouring) methods. The impact energy was read directly from the impact tester in joules, and the cross-sectional area of each specimen was used to calculate the impact strength in kJ/m2. Analysis of variance, Tukey multiple comparisons test, and a likelihood ratio α = .05 were conducted. Results: The average mean impact strength was 8.9 kJ/m2 for heat-cure acrylic resin, 11.2 kJ/m2 for 3D-printed resin, and 14.9 kJ/m2 for cold-cure acrylic resin. Tukey multiple comparisons test showed that the impact strength for the cold-cure group was significantly greater than for the 3D-printed resin and heatcure acrylic resin groups. Conclusion: Within the limitations of this study, the cold-cure acrylic resin showed the greatest impact strength, followed by the 3D-printed resin and conventional heat-cure denture base materials, respectively.