The International Journal of Prosthodontics, 02/2023

Purpose: To evaluate the extent to which dentists elaborate removable partial denture (RPD) design themselves and what they leave to the dental laboratory, as well as to assess the quality of information transferred to the technicians. Materials and Methods: Data were collected using a questionnaire, and the responses of 211 dentists were analyzed. The categorized variables were analyzed using chi-square test and Fisher exact test. The significance level was considered as the standard P < .05. Results: More than half (59.0%) of the dentists reported making an accurate, clear design for the dental technician before fabrication of the metal-framework RPD; 191 dentists (91.0%) specified the abutment teeth, 70.8% chose the type of clasps, and 60.7% gave instructions for the major connectors. The respondents largely took into account periodontal hygiene considerations (82.4%), and about one-third (37.7%) reported they were sending clear, precise instructions to the lab. The denture design was sent to the technician mainly (65.0%) in both drawing and text form. About half of the dentists (55.6%) gave only guidelines and left more details to be defined by the dental technician. Most dentists took responsibility in case of esthetic problems, irrespective of whether the dentist or technician prepared the denture design. Conclusion: Everyday practice concerning RPD design is far from the professional, legal, and ethical guidelines and rules relating to the duties and responsibilities of the dentist in relation to RPD design, and the situation therefore needs to be improved.

Purpose: To assess (1) whether an occlusal splint (OS) or mandibular advancement splint (MAS) allowed better sleep quality and was more comfortable in individuals with sleep bruxism (SB); and (2) the relationship between sleep quality, comfort, and reduction in RMMA related to SB. Materials and Methods: Polysomnographic data from 21 SB subjects (mean ± SD age 25.6 ± 4.5 years) collected in two previous studies were compared. Morning self-reports on sleep quality and comfort of the oral device, polysomnographic data, and RMMA index data from no-device nights were compared to nights using an OS or MAS. The reduction ratio of the RMMA index was calculated for both devices. A responder to the oral device was identified when the RMMA index was less than 2 and when it showed a reduction of at least 50% from the no-device control night. Results: Self-reports for sleep quality and comfort of the oral device showed a mild advantage of the OS when compared to the MAS (r² = 0.47, r² = 0.32; P ≤ .01). In responders, the MAS induced a greater reduction in the RMMA index (P = .03) than the OS. Conclusions: In the short term, the comfort of the oral device seemed to influence sleep quality in SB individuals. However, despite the slightly higher degree of comfort offered by the OS, the MAS induced a greater effect on the RMMA index.

Purpose: To evaluate oral health–related quality of life (OHRQoL) in patients with temporomandibular disorders (TMDs) involving masticatory muscle pain, disc displacement with reduction, or both and to determine the associations of these disorders with anxiety. Materials and Methods: This study consisted of 150 patients with TMDs and 50 healthy controls. Patients were diagnosed according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) Axis I and then divided into three diagnostic groups: masticatory muscle pain (group MP), disc displacement with reduction (group DD), or both (group MPDD). The participants completed the Oral Health Impact Profile-14 (OHIP-14) and Generalized Anxiety Disorder-7 (GAD-7) questionnaires for assessment of OHRQoL and anxiety, respectively. Statistical analyses were performed using Kruskal-Wallis test and Mann-Whitney U post hoc paired-comparison tests. Results: A total of 121 of the patients (60.25%) were female and 79 (39.75%) were male, ranging from ages 18 to 68 years (mean age: 37.32 ± 13.62). Gender distribution, mean age, educational status, and occupational status were similar among groups. The OHIP-14 global and domain scores and distribution of GAD-7 levels were significantly different among groups (P < .001). For psychologic discomfort and disability domains, group MPDD statistically scored the highest, followed by group MP, group DD, and then the control group (P < .05). According to correlation analyses, there were positive correlations between the GAD-7 and all OHIP-14 scores (r = 0.438, P < .001) within group MPDD. Conclusion: OHRQoL is negatively affected by TMDs and worsens as the severity of anxiety increases. Therefore, physical conditions and anxiety levels in TMD patients should be simultaneously considered for treatment and maintenance.

Purpose: To present a minimally invasive treatment approach for the replacement of two missing adjacent teeth with two single-retainer resin-bonded fixed dental prostheses (RBFDPs). Materials and Methods: Two missing adjacent premolars were restored by two RBFDPs with an innovative design of the proximal section. Both RBFDPs were digitally designed and milled from monolithic 3Y-TZP zirconia ceramic using CAD/CAM. Following construction of the anterior RBFDP, a shallow interlock was designed in the area of proximal contact in the same insertion direction as the posterior RBFDP. In this way, different paths of insertion of the RBFDPs could be provided without compromising the proximal hygiene capability. Results: The presented minimally invasive restorations were successful over 5 years of clinical observation without any complications. Conclusion: The presented restoration design secures the transversal position of the RBFDPs while maintaining physiologic tooth mobility. In addition, it allows for varying paths of insertion while improving hygienic conditions. Last, in case of a unilateral debonding of one retainer wing, rebonding might be possible.

Purpose: To investigate and analyze the effects of different prosthetic protocols under different loading and occlusal conditions on the survival rates of single implants immediately placed into fresh extraction sockets of maxillary or mandibular premolars with single-stage surgery. Materials and Methods: Patients needing replacement of a single premolar in the maxilla or mandible were included and randomly divided into three groups based on the different loading protocols: group 1 = healing abutment; group 2 = provisional crown left out of occlusion without functional loading; and group 3 = provisional crown in functional occlusion in maximum intercuspation without contact in excursions. The hypothesis was that single implants inserted into fresh extraction sockets and immediately connected to a temporary crown under functional loading would demonstrate survival rates comparable to single implants placed in the same conditions connected to a healing abutment or to an immediate temporary crown left out of occlusion. Results: A total of 112 patients were treated, and 126 implants were placed (92 in the maxilla and 34 in the mandible). After a mean follow-up of 2.5 years (range 1 to 5 years), there were no failures in groups 1 or 2. Two implants failed in group 3 (one in the maxilla, one in the mandible). The cumulative survival rate was 98.5% across all groups, with 100% in groups 1 and 2 and 95% in group 3. Statistical analysis showed that group 3 displayed a survival rate comparable to groups 1 and 2 (P = .08). Conclusion: Within the limitations of this study, no significant differences were found in terms of implant survival rates between implants inserted into fresh extraction sockets without loading vs with immediate nonfunctional or functional loading.

Purpose: To investigate microtensile bond strength and characterization with the novel lithium disilicate coating technique compared to conventional air abrasion. Materials and Methods: Eight zirconia blocks were fabricated and assigned to two groups (n = 4 each): (1) Lithium disilicate coating followed by hydrofluoric acid etching and Monobond N Primer (LiDi group); and (2) alumina air abrasion (MUL group). For each group, two identically pretreated zirconia blocks were bonded together with Multilink Speed Cement and cut into 30 stick-shaped specimens (1 × 1 × 9 mm3). The 120 specimens were stored in water for 24 hours and assigned to one of three groups (n = 20/group): (1) short-term storage for 24 hours; (2) thermocycling for 5,000 cycles; and (3) thermocycling for 10,000 cycles. A microtensile bond strength test was performed and evaluated. The bond strength results were analyzed using two-way ANOVA followed by one-way ANOVA and Tukey HSD (α = .05). Energy-dispersive x-ray spectroscopy (EDS), Fourier-transform infrared (FTIR), x-ray diffraction (XRD), focused ion beam scanning electron microscopy (FIB-SEM), and scanning electron microscopy (SEM) were used for chemical, crystalline phase, and failure mode analyses. Results: The MUL groups recorded higher bond strength than the LiDi groups. Thermocycling significantly decreased the bond strength in both groups. Chemical analyses suggested that the lithium disilicate layer underwent hydrolysis, which compromised long-term bond strength. Conclusion: The bond between composite cement and alumina-abraded zirconia performed better than that with the lithium disilicate coating technique.

Purpose: To evaluate the effect of different abutment screw retightening procedures on the screw stability between the abutment and implant. Materials and Methods: External hexagon connection (EHC) and internal trichannel connection (ITC) implants were employed in this study. Each abutment screw was used for the following specific applications (n = 5 for each group): group 0 = abutment was tightened and retightened with a 10-minute interval; group 1 = abutment was tightened and retightened with a 10-minute interval, then loaded for 500,000 cycles; group 2 = abutment was loaded for 83,000 cycles during tightening and retightening, then loaded for 500,000 cycles; group 3 = abutment was loaded for 167,000 cycles during tightening and retightening, then loaded for 500,000 cycles; and group 4 = abutment was loaded for 250,000 cycles during tightening and retightening, then loaded for 500,000 cycles. Both tightening and retightening torques were set at 35 Ncm, and dynamic oblique loading between 0 N and 200 N was applied on the abutment in all groups. The settling values of the abutments after retightening and the abutment removal torque values (RTVs) after testing were measured. Results: No significant differences in settling values were found between EHC and ITC. There were significant differences in the RTVs of EHC implants, but ITC implants showed no difference in RTV with different prosthetic retightening applications. Conclusion: The retightening application affected the joint stability of EHC implants but did not affect the settlement and joint stability of ITC implants.

Purpose: To evaluate the effect of cavity tapering on marginal and internal adaptation of endocrowns fabricated from two different ceramic materials. Materials and Methods: Two mandibular molar model teeth were prepared with two different cavity tapers (5 and 10 degrees). A total of 40 endocrowns (four groups of 10 each) were milled using lithium disilicate and zirconia-reinforced lithium silicate ceramics for each cavity taper. The marginal and internal adaptation of endocrowns were measured by a stereomicroscope (×30) at 18 different points. The data were statistically analyzed using independent t test (P < .05). Results: A statistically significant difference was shown among the tested groups at 10 degrees of taper (P < .001). At 5 degrees of taper, the difference was insignificant. The greatest internal gap was observed at the pulpal floor in all tested groups. Conclusion: All materials had clinically acceptable internal and marginal gaps; however, lithium disilicate ceramic had significantly better adaptation at 10 degrees of taper.

Purpose: To investigate the discoloration and surface properties of four CAD/CAM composite resins following storage in various food solutions and exposure to cigarette smoke. Materials and Methods: A total of 74 specimens (N = 370) were prepared for five materials: Brilliant Crios (BC), Cerasmart (GC), Lava Ultimate (LU), Shofu Block HC (SH), and Sonic Fill 2 (SO). Discoloration (ΔE) was investigated with a spectrophotometer. Measurements were taken before immersion in storage media (carrot juice, curry, cigarette smoke, red wine, energy drink, and distilled water), after 2 weeks of immersion, and after manual polishing of the specimens following immersion. The average surface roughness (Ra) was measured with a profilometer. Qualitative surface observation was performed with scanning electron microscopy (SEM). Data were analyzed using Kolmogorov-Smirnov test, Mann-Whitney U test, and one-way ANOVA with Tukey post hoc test. Results: The highest influence on ΔE after immersion was observed for storage medium (η_P² = 0.878, P < .001), followed by the interaction between storage medium and material (η_P ² = 0.770, P < .001) and material (η_P ² = 0.306, P < .001). For ΔE after polishing, the highest influence was indicated by the interaction between material and medium (η_P ² = 0.554, P < .001), followed by medium (η_P² = 0.244, P < .001) and material (η_P² = 0.196, P < .001). Immersion in carrot juice led to the highest color change (ΔE: 8.0 to 10.4), whereas the lowest values were recorded in distilled water (ΔE: 2.0 to 2.4). Carrot juice and the energy drink caused the highest Ra values (0.120 μm to 0.355 μm). SEM pictures indicated a loss of the organic matrix after manual polishing. Conclusion: The different materials reacted dissimilarly to the various storage media in terms of discoloration. Surface roughness increased after immersion or polishing. Neither discoloration nor surface roughness could be reset to default by manual polishing.

Purpose: To evaluate the stress distribution in endocrowns and post-and-core crowns used as abutments for a Kennedy Class I removable partial denture constructed with different framework materials. Materials and Methods: 3D models of a Kennedy Class I mandible were constructed. Cobalt-chromium (Co-Cr) and polyether ether ketone (PEEK) frameworks were simulated for Models 1 and 2, respectively. An endocrown and a fiber post-and-core crown for the mandibular left and right second premolar abutments, respectively, were simulated for both models. Lithium disilicate porcelain was defined for the crowns. A 200-N occlusal force was applied in the vertical and 30-degree oblique directions. Results: The von Mises stresses were evaluated for the abutments and prostheses, and the principal stresses for the cortical bone under vertical and oblique loading. Endocrowns showed lower stress values than post-and-core crowns in both models. Postand- core crowns generated the highest stress in Model 2 under vertical loading. The PEEK framework caused higher stress values on the abutments than Co-Cr. Compressive stresses were higher than tensile stresses in cortical bone. The highest compressive stress was observed around the left premolar cortical bone area in Model 1 under oblique loading. Oblique loading caused lower stress values than vertical loading, except for on the minor connectors and cortical bone. Conclusion: From a biomechanical perspective, endocrowns may be more advantageous than post-and-core crowns when used as abutments for a Kennedy Class I removable partial denture. In addition, Co-Cr frameworks showed more favorable stress distribution on abutments than PEEK frameworks.

Purpose: To survey the materials favored by dentists for intraoral repair of cohesive chipping. Materials and Methods: From August 2019 to February 2020, dentists were surveyed to determine the frequency of cohesive chipping experienced within the last 3 months and to identify their preferred approaches for intraoral repair. Results: Of the participants, 42.5% observed chipping (n = 506). Participants favored the application of roughening devices, silane, and composite resins. Self-etching glass-ceramic primers or hydrofluoric acid were used for ceramic etching. Conclusion: Dentists apply a variety of materials for intraoral repair of chipping, including materials that are not approved for intraoral use.

Purpose: To determine the effect of scanning protocol, number of implants, and implant splinting on the accuracy of digital scanning in the edentulous arch. Materials and Methods: A resin-based model of an edentulous mandible with six implants was scanned with a coordinate measurement machine as a reference and then with two intraoral scanner (IOS) systems (Trios 3 and Primescan). Ten scans were taken per IOS for three experiments, and each scan was compared to the reference data to evaluate trueness and precision. Analysis involved measurement of linear and angular discrepanices using engineering software. In experiment 1, three scanning protocols were compared (curvilinear, zigzag, and half-arch). In experiment 2, three clinical situations were simulated (6 implants, 4 implants–short arch, and 4 implants–long arch). In experiment 3, the effect of implant splinting with a suture thread was measured. Normal distribution of data was examined with Shapiro-Wilk test. Levene test was used for equality of variance (α = .05). Statistical differences in distance and angular deviations were analyzed using Student t test or ANOVA with post hoc Tukey test (α = .05). Results: The best results in terms of trueness and precision were obtained with a linear scanning protocol and six implants. The results were as follows: Trios 3: trueness = 52 μm/0.42 degrees, precision = 40 μm/0.26 degrees; Primescan: trueness = 24 μm/0.28 degrees, precision = 18 μm/0.27 degrees. The scanning protocol did not significantly affect distance or angular deviation accuracy. Trueness and precision significantly decreased with four implants using Primescan and TRIOS 3. Splinting implants negatively affected accuracy with both IOS devices. Conclusion: Both IOS devices achieved clinically satisfying accuracy for distance (< 100 μm) and angular (< 0.5 degrees) deviations with six implants and a linear scanning protocol. With four implants, angular deviations sometimes differed between implants within the same group depending on the IOS and the clinical situation.

Purpose: To describe the treatment of malpositioned implants in the esthetic area using the angulated welded abutment (AWA) approach together with peri-implant soft tissue surgery. Materials and Methods: A clinical case with extreme buccal angulation of two implants in the anterior maxilla was used to illustrate the AWA technique. After implant impression-taking, digital analysis was used to determine the ideal prosthetic angulation of the abutment and the ideal position of its screw hole in relation to the gingival margin of the adjacent teeth. The AWA was designed in two combinable components that were meant to be welded together. Before the welding process, an angulated screw was included in the abutment. Since the angulated screw was inside the abutment, the screwdriver hole could be designed as narrow as possible and put in an ideal position. After periodontal and peri-implant surgery were carried out, the AWA was applied to the implants. Results: The AWA allowed correction of the prosthetic axis. Moreover, relocation of the screw hole allowed the gingival tissue to creep over the abutment. In this way, a new esthetic restoration can be placed after the mucogingival surgery. Conclusion: The excessive misangulation of the implants was efficiently recovered. Further studies are needed to evaluate long-term clinical success, and standardization of this technique is required for routine clinical use.