Journal of prosthodontic research最新文献

Purpose: Excessive occlusal forces resulting from inadequate dental prosthesis, along with periodontal infection (PI), lead to severe periodontitis; however, the roles of senescent cells and their involvement in the mechanisms underlying this process remain unclear. Therefore, this study aimed to elucidate the roles of senescent cells and their cell types in severe periodontitis with excessive force (occlusal trauma [OT]).

Methods: To determine whether senescent cells exacerbate alveolar bone resorption, we developed a severe periodontitis rat model by inducing PI and OT and assessed the presence of senescent cells and bone resorption. Senolytics (dasatinib + quercetin [DQ]) were administered to evaluate the changes in the appearance of senescent cells and bone resorption.

Results: PI and OT + PI increased senescent cells as well as osteoclasts. Furthermore, p21 and receptor activator of nuclear factor-kappa B ligand (RANKL) co-expressing cells were observed in the OT + PI group rats, suggesting a correlation between bone resorption and senescent cells. Cell type analysis identified osteoblasts and Th17 cells as RANKL⁺ cells expressing p21 or p16. DQ administration reduced senescent cells and osteoclasts, thereby preventing alveolar bone resorption.

Conclusions: RANKL⁺ senescent osteoblasts and Th17 cells are involved in osteoclastogenesis and bone resorption. Our findings highlight a new target for the prosthetic treatment of severe periodontitis.

Purpose: This study was aimed at investigating the thermal stresses in monolithic zirconia crowns (MZC) of various thicknesses and elucidating their thermal behavior under cooling or heating changes in the oral cavity. Additionally, the clinical availability and potential issues of MZC were examined by comparing them with other crown materials.

Methods: Finite element models comprising MZC (0.5-, 1.0-, and 1.5-mm thick), cement layers, and abutment teeth were subjected to thermal changes from 37 to 5 °C or 60 °C. Using a thermal distribution at 5 s, the thermal stress was calculated and compared with those of gold alloy and resin composite crowns. The loads corresponding to the thermal stresses were also estimated by comparing them with the stresses induced by vertical loading on the occlusal surface.

Results: Tensile stress occurred primarily in the crowns and cement during cooling, whereas compressive stress was generated during heating. Thermal stresses increased from 16.0 to 27.2 MPa with decreasing crown thickness from 1.5 to 0.5 mm and varied with different materials. Although the MZC exhibited the highest thermal stress, the estimated load (200 N) corresponding to the thermal stress was smaller than that of the resin composite (1280 N).

Conclusions: Thinner crowns exhibited higher thermal stress, suggesting an increased risk of failure owing to thermal changes. Despite the higher thermal stress in thinner MZC, the stresses were below the fatigue strength of the material, indicating sufficient resistance to thermal changes in the oral cavity.

Purpose: To clarify the intra- and inter-examiner reliability of an occlusal force-measuring device equipped with a capacitive-type pressure-mapping sensor sheet in older adults.

Methods: Thirty-eight individuals (23 women) aged ≥65 (mean ± SD: 79.3±6.1) years were included. The numbers of present and functional teeth were visually examined. Occlusal force was measured using the Oramo-bf device (Sumitomo Riko Co., Aichi, Japan). To evaluate intra-examiner reliability, one dentist measured each participant's occlusal force thrice and calculated the intraclass correlation coefficient (ICC; case 1) and the coefficient of variation (CV). To examine inter-examiner reliability, three dentists measured the occlusal force once per participant and calculated the ICC case 2.

Results: The median (first quartile-third quartile [Q1-Q3]) numbers of present and functional teeth were 22.5 (18-27) and 28 (26-28), respectively. The median (Q1-Q3) occlusal force measured by a single examiner across the measurements was 604.8 (261.7-731.5) N. The ICC for a single measurement by one examiner based on all three measurements per participant was 0.982 (95% confidence interval [CI]: 0.969-0.990). The ICC (1,3) for the mean of three repeated measurements by one examiner was 0.994 (95% CI: 0.990-0.997). The mean ± SD CV was 0.052 ± 0.046. The ICC (2,1) for inter-examiner reliability was 0.950 (95% CI: 0.917-0.972).

Conclusions: This study revealed high intra- and inter-examiner reliability of measurements obtained using an occlusal force-measuring device equipped with a capacitive-type pressure-mapping sensor sheet. This device may provide reliable results with a single measurement, regardless of the examiner.

Purpose: To evaluate the clinical use of CAD/CAM hybrid ceramics in patients with severe tooth wear.

Methods: Forty-nine patients with severe tooth wear underwent prosthetic management with 116 hybrid ceramic restorations. The restorations were evaluated at 1 week and at 3, 6, 12, 18, 24, 30, and 36 months after placement. The amount of wear on the restorations, antagonist teeth, and opposite teeth was compared using digital superimposition analysis. A questionnaire was used to evaluate participants' satisfaction with the restorations. Complications were recorded, and survival rates were estimated using Kaplan-Meier analysis.

Results: The clinical performance of the restorations was stable for esthetic, functional, and biological parameters up to 3 years, except for greater changes in "surface and margin staining" and "fracture and retention." There was no significant difference in the amount of progressive wear among the restorations, antagonist teeth, and opposite side teeth until 18 months; however, the wear on the restorations increased gradually up to 36 months. Higher scores and identical satisfaction results were obtained for the chewing efficiency and cleanability during the observation period. The most common complications were restoration dislodgement (5.2%) and partial marginal chipping (4.3%), which were clinically repaired. Four restorations (3.4%) were extensively fractured and replaced. The estimated survival rate of the hybrid ceramic restorations at 3 years was 88.0%.

Conclusions: The clinical use of hybrid ceramic restorations in patients with severe tooth wear improved chewing efficiency and esthetics, provided adequate resistance for load-bearing, and delivered a stable treatment outcome after functional use.

Patients: A 22-year-old female patient presented with a lower right first molar exhibiting an extensive carious lesion beneath an old direct resin composite restoration. Radiographic evaluation revealed pulpal involvement with a periapical infection, accompanied by grade II mobility and a circumferential probing depth of <3 mm. The compromised molar rehabilitation was carried out using a multichromatic 3D-printed onlay. A fully digital workflow was employed, enabling the completion of the procedure in a single clinical session. Following endodontic and restorative treatments, intraoral scans were acquired using a Trios5 scanner. The restoration was digitally designed and 3D printed from STL files using the DWS Systems Dfab printer. The hybrid composite onlay was adhesively luted using a universal self-adhesive resin cement (Panavia SA, Kuraray). Clinical evaluations at 6 months and 1 year demonstrated favorable outcomes, with high patient satisfaction.

Discussion: 3D printing represents a digital evolution in the fabrication of dental restorations, introducing an additive manufacturing approach distinct from the subtractive processes used in traditional CAD/CAM systems. In cases of severely compromised teeth, 3D-printed, adhesively bonded partial restorations represent a viable treatment option. The hybrid composite used in this study demonstrated favorable clinical and esthetic performance, enabling minimally invasive preparations while preserving sound tooth structure.

Conclusions: Chairside 3D printing technology presents an alternative approach for the fabrication of indirect composite restorations in posterior teeth. Although 3D printing is not yet widely adopted in restorative dentistry, its versatility may offer significant advantages for both clinicians and patients in the production of indirect partial restorations.

Purpose: This study aimed to investigate the characteristics of jaw movement trajectories in the horizontal plane and the maximal activities of the masseter muscle during grinding events associated with rhythmic masticatory muscle activity (RMMA), as a potential biomarker for the diagnosis of sleep bruxism.

Methods: The biological signals and jaw movement data of eight participants were recorded using a custom-developed intraoral sensor, a six-degree-of-freedom magnetic jaw-tracking device, and polysomnography. These recordings were synchronized using Global Positioning System time data. Jaw movement data during grinding events were compared with simulated grinding (lateral excursion) data obtained before sleep, focusing on deviations from the anteroposterior direction in the horizontal plane. Additionally, the timing of the maximal masseter muscle activity was examined.

Results: No sleep disturbances were reported by the participants. During tooth grinding, the jaw movement trajectories of the lateral excursions in the horizontal plane frequently deviated from the simulated grinding trajectories, indicating variability among participants. Notably, the deviations were more pronounced during lateral excursions to the lateral side, with movements diverging both anteriorly and posteriorly from the simulated grinding trajectories. Regarding the masseter muscle activity, greater activity was observed on the balancing side. Peak masseter muscle activity increased when the jaw movement trajectories deviated posteriorly from the simulated grinding trajectory, on both the working and balancing sides.

Conclusions: Excursions deviating posteriorly during RMMAs from the simulated grinding were associated with significantly greater masseter muscle activity than either excursions deviating anteriorly or those along the simulated grinding trajectory.

Purpose: To assess the predictability of using the roots of the maxillary anterior teeth in advantageous positions to guide immediate implantation and enhance the positioning precision of placed implants.

Methods: Existing root canals were used in the test group for manual preparation of the implant bed, whereas traditional freehand techniques were employed in the control group. The three-dimensional position of the placed implants was measured using radiological images taken on the day of surgery and again six months post-surgery and evaluated using self-developed rating criteria for the radiographic positions of the implants. The spatial relationship between the axial orientation of the implant and prosthetic crown was assessed using a self-developed scoring scale. Statistical analysis of the three-dimensional positional imaging scores of the implants was conducted immediately after surgery and at six months post-implantation. Intergroup statistical analysis was conducted on the scores reflecting the spatial relationship between the axial orientation of the implants and their prostheses.

Results: The test group demonstrated significantly higher scores for the labial-palate and horizontal positions, both immediately following surgery and at six months post-implantation, than the control group. Furthermore, the test group significantly outperformed the control group in terms of scores reflecting spatial relationships.

Conclusions: Utilizing the roots of the anterior teeth in advantageous positions as guides for preparing implant beds can lead to more ideal implant placement than traditional manual techniques.

Purpose: This was a prospective study conducted alongside a randomized controlled trial (RCT) that evaluated the incidence of fractures and associated risk factors in single-implant overdentures (1-IOD) compared with two-implant overdentures (2-IOD).

Methods: The participants received either a mandibular 1-IOD or 2-IOD (attachments: Straumann® retentive anchor and elliptical titanium matrix with gold insert; implants: 4.1 mm diameter, Straumann® Standard Plus SLActive® Regular Neck), within the context of a randomized clinical trial. The primary outcome of interest was the incidence of IOD fractures at 5-year follow-up. Prosthetic factors, such as area and cervico-incisal height in the attachment region, and volume at the inter-canine region, were measured. Patient-related factors including age, sex, handgrip strength, manual dexterity, bite force, and chewing performance were assessed. Data analysis included descriptive statistics, bivariate tests, Kaplan-Meier plots, and linear discriminant analysis with log₁₀ transformation for variable normalization.

Results: A total of 47 patients were recruited, and 34 (n = 34, 1-IOD = 16, 2-IOD = 18; mean-age: 63.9 ± 8.6 years; 79.4% women) completed the 5-year follow-up. There were no differences in the incidence of fractures between the 1-IOD and 2-IOD groups (P < 0.05). Fractures were more frequent in younger patients, and reduced cervico-incisal IOD height was significantly associated with fractures (P = 0.040). Linear discriminant analysis predicted fractures with 84.4% accuracy and identified cervico-incisal height and age as key predictors.

Conclusions: There were no significant differences in the incidence of overdenture fractures between groups. Reduced cervico-incisal denture height in the attachment region of ball-retained IODs was associated with mandibular IOD fractures. Further studies with larger cohorts are recommended to identify additional risk factors for mandibular IODs.

Patients: A 56-year-old man with a left-sided cleft lip and palate was referred to our department due to mastication and speech difficulties. His existing prostheses have become unstable owing to changes in the remaining dentition over 10 years. For the fabrication of the new interim maxillofacial prostheses, a digital impression technique was selected as the conventional technique posed medical risks due to hypermobile teeth and maxillary defects. New interim maxillofacial prostheses were fabricated using a combination of the digital impression technique and a bite-seating impression, performed with trial prostheses and impression material. The patient has been using the new interim prostheses comfortably since delivery. The oral functional evaluation yielded favorable results.

Discussion: Patients with cleft lip and palate should use their existing maxillofacial prostheses during the fabrication of new ones, even if they are of suboptimal quality. Although addressing these issues using conventional techniques is challenging, digital technology provides a viable solution. However, impression material is essential for capturing mucosal defects and complex anatomy in cleft lip and palate cases; therefore, digital data should be supplemented by either well-adjusted existing prostheses or bite-seating impressions using impression material before new prostheses fabrication. Although his occlusal force was lower than the criterion for the oral hypofunction test, his masticatory performance remained favorable. Speech analysis revealed persistent air leakage; however, all scores improved with the prostheses.

Conclusions: Digital technology has enabled the safe fabrication of interim maxillofacial prostheses, resulting in improved masticatory and speech performance.

Purpose: Evaluation of the impact of ultraviolet (UV) photofunctionalization on titanium-cement interfaces, specifically its ability to transform titanium into a high-energy surface and enhance crown retention.

Methods: Commercial titanium abutments (standard: 4.0 mm; long: 5.5 mm) were treated with vacuum UV (VUV) light at 172 nm for 1 min. Milled polymethyl methacrylate crowns were cemented using resin-modified glass ionomer cement. Tensile testing quantified the maximum tensile load and interfacial energy. Surface changes were analyzed using contact angle measurements and X-ray photoelectron spectroscopy (XPS). Post-failure interfaces were examined via scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX).

Results: UV-treated standard-length abutments exhibited a 4.1-fold increase in maximum tensile load and 27-fold increase in bonding energy compared with untreated control counterparts. UV-treated long abutments showed a 4.6-fold increase in maximum tensile load and 54-fold increase in bonding energy. UV treatment rendered the titanium surface superhydrophilic and low in carbon, whereas untreated specimens remained carbon-rich and hydrophobic. UV-treated long abutments exhibited 3.1-fold higher energy than UV-treated standard abutments. Notably, long abutments without UV treatment did not outperform standard untreated abutments. SEM and EDX confirmed extensive residual cement on UV-treated abutments, indicating cohesive failure and strong interfacial bonding.

Conclusions: A 1-min UV photofunctionalization transforms titanium into a superhydrophilic, high-energy surface that significantly enhances cement bonding. This physicochemical surface strategy outperforms geometric modifications alone. As a rapid, non-invasive approach, UV photofunctionalization may establish a new standard for durable implant-supported restorations, reducing prosthetic failure and influencing both material selection and clinical and laboratory workflows.