Journal of prosthodontic research最新文献

Purpose: To evaluate the trueness of denture bases fabricated using digital light processing (DLP) and milling methods using three-dimensional (3D) models with varying residual ridge morphologies.

Methods: Edentulous mandibular 3D models representing a well-rounded ridge (WR), knife-edge ridge (KR), and flat ridge (FR) were designed using computer-aided design (CAD) software. Denture bases for these models were created using dental CAD software and fabricated via DLP 3D printing at build angles of 0 and 45 degrees (DLP0 and DLP45) and by milling (MIL). A total of 90 denture bases were fabricated, with 10 bases per model-method combination. These bases were digitized and compared to their original CAD data to assess the adaptation across three regions: denture border, alveolar ridge, and retromolar pad. Measurements were performed at three time points: before water storage, after 1 day of water storage, and after 7 days of water storage.

Results: The MIL bases exhibited significantly lower 3D surface deviations than the DLP0 and DLP45 bases. The KR models generally exhibited greater 3D surface deviations than the WR and FR models. Temporal changes in the denture bases were significant across almost all ridge types and manufacturing methods.

Conclusions: The trueness of digitally fabricated denture bases is influenced by the residual ridge morphology and manufacturing method. Milling demonstrated superior trueness compared to DLP. Temporal dimensional changes were observed in almost all the bases.

Purpose: To elucidate how the combination of acidic and sulfur-based monomers enhances bonding to oxidized noble metal alloy surfaces.

Methods: Two types of gold alloys were used: one with a low copper content (DG) and the other with a high copper content (IV). Three primers were used: a sulfur-based monomer primer (VP), a phosphate-based acidic monomer primer (PZ), and a combination of both (MC). Two conditions were used: heated and non-heated. The shear bond strengths before and after thermocycling were determined and compared for each condition. Surface chemical analysis was performed using X-ray photoelectron spectroscopy (XPS).

Results: After thermocycling, the bond strength of MC was significantly higher than that of the VP under all conditions. In the comparison of alloys under heating conditions, IV showed a significantly higher bond strength than that of DG for the PZ and MC groups. XPS revealed peaks attributed to copper oxide (CuO) formation on the heated IV surface.

Conclusions: Multipurpose primers are effective for bonding oxidized noble metal alloys and acrylic resins. The formation of CuO improves the performance of 10-methacryloyloxydecyl dihydrogen phosphate, and its combination with sulfur-based monomers is particularly effective for noble metal alloy surfaces with high copper content.

Purpose: Extensive maxillectomy may result in rapid contour changes in the unsupported facial tissue, causing irreversible and severe aesthetic deformities. This technical report details a novel digital workflow for the fabrication of obturators with immediate facial support consistent with the existing maxillary contour.

Methods: Preoperative digital impressions were obtained using an intraoral scanner (IOS). A three-dimensional (3D) model of the presurgical maxillofacial hard tissue was constructed using cone-beam computed tomography (CBCT) and aligned with the IOS data. Surgical planning data were used to guide the separation and fusion of anatomical reference data for obturator design from the CBCT and IOS data. The obturator was designed using dental design software, and the existing maxillary morphology for facial support was transferred to the obturator. After the surgical resection, an immediate obturator with a surgical pack was placed at the defect site.

Conclusions: The implementation of a fully digital workflow demonstrated the potential to streamline the complex procedure traditionally required to restore harmonious facial contour support through the transfer of maxillary morphology to the immediate obturator. This method offers a promising and viable alternative to conventional techniques, with the potential to minimize long-term aesthetic compromise, facilitate adaptation and functional restoration, and simplify postoperative prosthetic care.

Purpose: This study aimed to determine whether the maximum compressive force exerted on denture base materials by test foods varies depending on the presence and type of resilient denture liners.

Methods: The maximum compressive forces of gummy jelly and peanuts were measured using a texture analyzer equipped with a 500 N load cell, operating at a crosshead speed of 9.78 mm/s. Tests were conducted on rectangular prism-shaped specimens (30 mm × 30 mm × 4 mm) fabricated from various denture base materials. Three commercial silicone-based resilient denture liners-Sofreliner Supersoft (SS), Sofreliner Mediumsoft (MS), and Sofreliner Tough Medium (TM)-and a conventional heat-cured acrylic resin (Urban, UR) were used. Additionally, the Shore A hardness of each material was measured using a hardness tester.

Results: The maximum compressive forces applied to gummy jelly and peanuts on UR specimens were significantly higher than those on TM, MS, and SS specimens. Similarly, the Shore A hardness of UR was higher than that of the other materials. A statistically significant positive correlation was observed between the maximum compressive force of the test foods and the Shore A hardness of the denture base materials.

Conclusions: The maximum compressive force applied to food varied according to the type of denture base materials. In particular, resilient denture liners effectively reduced the force transmitted to the food compared with conventional hard acrylic resin.

Purpose: The purpose of this study was to establish chevron-notched beam (CNB) finite element analysis (FEA) models to investigate the fracture toughness of zirconia ceramics.

Methods: Experimental four-point flexural strength data (n = 9; previously published) for 3 mol% yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP; 3M Oral Care, Seefeld, Germany) were combined with numerical data (calculated using the inverse finite element method) to evaluate the input material properties of the CNB-FEA models. These models (n = 8) were then simulated and validated against the CNB test data of specimens with the same geometries (n = 8). The validation criteria included the margin of error, coefficient of determination, and linear regression. FEA was used to evaluate the volumetric strain distribution during deformation.

Results: 3Y-TZP has static elastic modulus and fracture strain values of 144.5 GPa and 0.0056, respectively. The fracture toughness of the CNB-FEA models closely matched those of the corresponding test specimens (±3% error). Linear regression yielded a coefficient of determination (R²) of 0.94 (P < 0.05), demonstrating an excellent predictive performance. The CNB-FEA models accurately reflected the actual fracture behaviors of the zirconia ceramics, with the volumetric strain localized at the notch tip.

Conclusions: The volumetric strains of the CNB-FEA models could be determined using the FEA and measured four-point flexural strength data. Thus, CNB-FEA was found to be a valuable method for predicting the fracture toughness of zirconia ceramics.

Purpose: Masticatory exercise promotes systemic health and cognitive function. Although acute masticatory stimuli enhance prefrontal cortical activity, the effects of increased habitual chewing on cortical activity remain unclear. This study evaluated the effects of habitual chewing on cortical activity in young adults.

Methods: Forty-one young adults (aged 21-31 years) were randomly assigned to an intervention group, which used a wearable device to increase attentional chewing strokes during meals for 1 month, or a control group that did not use the device. We monitored the cortical activity during gum chewing using functional near-infrared spectroscopy at baseline and immediately after intervention. We recorded the number of chews per rice ball at baseline, immediately after intervention, and at 3 months post-intervention. Changes across different time points in each group were compared using one-sample t-tests with Bonferroni correction.

Results: The intervention group showed a significant increase in the number of chews after the intervention and at the 3-month follow-up, whereas the control group exhibited no changes. Moreover, the intervention group demonstrated significantly higher activity in the dorsolateral prefrontal cortex (DLPFC) and premotor cortex compared with the control group. A voxel-based correlation analysis revealed a positive correlation between increase in chewing strokes and activity in these brain regions in the intervention group (family-wise error-corrected, P < 0.05).

Conclusions: Intentional chewing, enhanced through an attentional intervention, led to increased activation in the DLPFC and premotor cortex during mastication. These results demonstrated the objective neural effects of interventions targeting habitual masticatory behavior.

Patients: This report presents a minimally invasive, adhesive-friendly approach for the esthetic rehabilitation of multiple anterior teeth using a modified direct-indirect technique with ultrathin composite resin veneers. A 43-year-old woman presented with esthetic concerns and disharmony of the maxillary anterior region. The treatment comprised ultrathin composite resin veneers fabricated using a modified direct-indirect technique, incorporating a fully digital workflow with a smile design and a three-dimensional-printed model used to create a translucent silicone index. Without tooth preparation, the index was filled with composite resin and intraorally positioned to replicate the planned morphology. The veneers were removed, post-cured, and extraorally completed before definitive adhesive cementation.

Discussion: Traditionally, the direct-indirect technique has been limited to single restorations that require enamel reduction and freehand stratification. This report describes a modified approach that enables the fabrication of multiple ultrathin veneers without tooth preparation, thereby preserving the enamel and promoting adhesive longevity. The innovative aspect lies in the integration of a fully digital workflow, ensuring precise replication of the morphology and control of the restoration thickness. Extraoral finishing of proximal contacts and margins before cementation improves clinical efficiency and esthetic predictability.

Conclusions: For patients requiring multiple composite veneers, the modified direct-indirect technique provides a conservative, precise, and predictable solution. It preserves sound tooth structure, optimizes adhesive performance, and enhances efficiency and esthetic outcomes through digital integration.

Purpose: Conventional handheld pH meters have measurement limitations. Therefore, this study aimed to continuously measure the salivary pH at two intraoral locations using a newly developed sensor system.

Methods: In this pilot study, we developed custom-made intraoral mouthguards (MG) with two pH sensors in the anterior region (Channel 1: Ch1) and the buccal side of the maxillary molar (Channel 2: Ch2) to continuously monitor salivary pH at two different locations in the oral cavity.

Results: The coefficient of determination (R²) for all MG sensor measurements was ≥0.99, with a high level of accuracy. Both sensor channels exhibited similar mean pH values for standard solutions, with small and constant variations. However, notable unstable differences in intraoral measurements were observed during rehydration owing to positional differences. Nonetheless, the MG sensors demonstrated excellent reliability with consistently high Intraclass Correlation Coefficients ranging from 0.977 to 0.999.

Conclusions: This pilot study provides valuable insights into salivary pH fluctuations, particularly during exercise, through continuous measurements using a sensor system for the simultaneous acquisition of real-time data from different anatomical sites. These results emphasize the potential of developing an intraoral sensor system that can detect subtle variations in salivary pH.

Purpose: This review examined clinical and technological factors that influence implant placement accuracy in computer-assisted implant surgery (CAIS) systems.

Study selection: A systematic search of PubMed, Scopus, and Embase identified English-language studies published between January 2015 and January 2025. The eligible studies included randomized controlled trials, observational studies, systematic reviews, in vitro investigations, and case reports. Data extraction focused on the coronal, apical, and angular deviations. Methodological quality was appraised using the Oxford Centre for Evidence-Based Medicine (CEBM) framework and validated bias assessment tools.

Results: Fifty-three studies were included. Accuracy was influenced by patient-related factors (arch type, bone density, and edentulous span), surgical variables (flap design, operator experience, and guide protocol), and technological parameters (imaging modality, fiducial markers, and calibration). Static systems achieved high accuracy in dentate cases with stable guide support, but were less reliable in posterior or edentulous jaws. Dynamic navigation provided intraoperative flexibility and consistent performance across arches, although outcomes depended on calibration precision and operator learning curves. Robotic-assisted systems achieved the lowest mean deviations through trajectory control and haptic feedback, although evidence remains limited to early clinical and in vitro studies.

Conclusions: Although all CAIS systems achieve high accuracy, their performance varies according to the design of the system and clinical context. Static systems are effective when stabilization is ensured, while dynamic navigation offers adaptable accuracy across scenarios, and robotics exhibit the greatest consistency by reducing operator variability. Further multicenter randomized trials and standardized reporting are needed to strengthen the available evidence and guide clinical selection.

Purpose: Hard reline procedures are commonly used to improve denture fit; however, the long-term durability of reline materials remains unclear. This study evaluated time-dependent changes in the surface properties and biofilm adhesion of light- and auto-polymerizing hard reline materials following long-term immersion in artificial saliva. The findings may help determine optimal timing for clinical intervention and enhance prosthesis longevity.

Methods: Specimens of three materials-light-polymerizing reline, auto-polymerizing reline, and heat-polymerizing denture base polymethyl methacrylate-were immersed in artificial saliva for up to 180 days. Auto-polymerizing materials continue to polymerize over time, whereas light-polymerizing materials require light irradiation. The surface properties were evaluated based on Vickers hardness, surface roughness, color stability, contact angle, and Candida albicans (C. albicans) biofilm adhesion.

Results: After 180 days, the light-polymerizing material exhibited a significant increase in hardness (P < 0.001), whereas the auto-polymerizing material exhibited an increase from day 120 (P < 0.001). Contrastingly, the heat-polymerizing PMMA exhibited a significant decrease in hardness. The surface roughness increased nearly threefold for the auto-polymerizing material, indicating pronounced degradation. Color changes in the light-polymerizing material were weaker than those in the auto-polymerizing material at all time points except at 60 and 150 days. C. albicans adhesion increased significantly in the auto-polymerizing material (P = 0.034), whereas the light-polymerized material showed no significant change (P = 0.258).

Conclusions: Time-dependent changes in surface characteristics were observed in both reline materials. The light-polymerizing material superior stability throughout the immersion period compared with that of the auto-polymerizing material, indicating superior long-term performance.