Journal of prosthodontic research最新文献

Purpose: To investigate the remnant cement in the subgingival regions (RCS) of abutments fabricated with different CAD/CAM parameters, including margin curvature radius, convergence angle, top fillet radius, and subgingival abutment shape.

Methods: Twelve experimental groups were fabricated to test the following parameters: abutment margin curvature radii of 0.8 mm, 1.2 mm, and 1.6 mm; convergence angles of 4°, 8°, and 12°; top fillet radii of 0.6 mm, 1.0 mm, and 1.4 mm; and subgingival abutment shapes of straight, S-curve, and concave. A constant amount of cement was injected into each crown. Vertical and continuous loads were applied to each specimen using a universal machine. RCS values were measured using a 3D intraoral scanner and an analytical balance. Statistical analysis was performed using one-way analysis of variance followed by post hoc Tukey test (α = .05).

Results: Regarding margin curvature radius, RCS values were significantly higher in the order of 1.6 mm, 1.2 mm, and 0.8 mm (P < 0.001). For convergence angle, higher RCS values were observed at 12° > 8° > 4°(P < 0.001). Among subgingival abutment shapes, concave yielded the highest RCS values, followed by S-curve and straight (P < 0.001). No significant differences in RCS values were found among the groups with different top fillet radii (P > 0.05).

Conclusions: Within the limitations of this study, a smaller margin curvature radius, smaller convergence angle, and straight subgingival shape were associated with reduced RCS length, surface area, and weight.

Purpose: This study evaluated the cytotoxicity of clinically available dental cements containing resin: conventional adhesive resin cement (ARC), self-adhesive resin cement (SARC), and resin-modified glass-ionomer cement (RMGIC), focusing on their degree of conversion (DC) and effects on cellular responses.

Methods: The DC of all the groups was measured over two weeks under light-free conditions. Cell viability, morphology, and apoptosis were assessed in gingival fibroblasts, dental pulp stem cells, and macrophage cells after exposure to extracts from specimens with different DC values. Eluate analysis was performed using attenuated total reflectance-Fourier transform spectroscopy and gas chromatography/mass spectrometry.

Results: The DC increased rapidly within 20 min for ARC and SARC, reaching a plateau at 24 h, while RMGIC showed a slower increase. ARC and SARC exhibited significant cytotoxicity at lower DC levels, with improved cell viability as DC increased. RMGIC displayed minimal cytotoxicity across all DC levels. Analysis revealed unreacted monomers and other substances contributing to cytotoxicity, with apoptotic effects correlating to their concentration in the eluates.

Conclusions: DC significantly influences the cytotoxicity of resin-containing dental cements, with ARC and SARC showing higher cytotoxic effects at lower DC levels compared with RMGIC. Considering DC levels may guide clinicians in minimizing adverse effects when selecting these cements. Dental cements containing resin can release substances that may affect cell viability.

Purpose: To establish the relationship between rhythmic masticatory muscle activity (RMMA) of the masseter muscle during sleep bruxism (SB) and occlusal wear and distortion in the stabilization occlusal appliance (OcA) used for its treatment.

Methods: Seventeen adults with SB wore OcAs composed of polymethyl methacrylate for 28 days. Weekly recordings included electromyography (EMG) of the masseter muscle using a wearable EMG device, evaluation of SB variables, and 3D scanning of the OcA using a 3D dental model scanner. The awake bite force at the time of recruitment was measured using a film-based bite force measurement system. The 3D data collected weekly before and after wearing the OcA were superimposed, and the weekly deformations in the coronal-apical directions were calculated. The masseter muscle activity per hour (RMMA index) and OcA deformation were compared weekly. Finally, we investigated the relationship between the frequency and intensity of the masseter muscle activity patterns and OcA deformation.

Results: No significant differences were observed in weekly RMMA index; however, all OcA deformations were significant. Apical deformation, including occlusal wear, was positively correlated with awake bite force. Coronal deformation reflecting distortion was positively correlated with the number of sustained tonic masseter muscle activities and maximum masseter muscle activities.

Conclusions: OcA deformation measured using this system reflects the frequency and intensity of the RMMA and masseter muscle activity in patients with SB, suggesting its potential as a novel clinical diagnostic tool for SB.

Purpose: Measuring enamel depth distribution (EDD) is of great importance for preoperative design of tooth preparations, restorative aesthetic preview and monitoring enamel wear. But, currently there are no non-invasive methods available to efficiently obtain EDD. This study aimed to develop a machine learning (ML) framework to achieve noninvasive and radiation-free EDD predictions with intraoral scanning (IOS) images.

Methods: Cone-beam computed tomography (CBCT) and IOS images of right maxillary central incisors, canines, and first premolars from 200 volunteers were included and preprocessed with surface parameterization. During the training stage, the EDD ground truths were obtained from CBCT. Five-dimensional features (incisal-gingival position, mesial-distal position, local surface curvature, incisal-gingival stretch, mesial-distal stretch) were extracted on labial enamel surfaces and served as inputs to the ML models. An eXtreme gradient boosting (XGB) model was trained to establish the mapping of features to the enamel depth values. R² and mean absolute error (MAE) were utilized to evaluate the training accuracy of XGB model. In prediction stage, the predicted EDDs were compared with the ground truths, and the EDD discrepancies were analyzed using a paired t-test and Frobenius norm.

Results: The XGB model achieved superior performance in training with average R² and MAE values of 0.926 and 0.080, respectively. Independent validation confirmed its robust EDD prediction ability, showing no significant deviation from ground truths in paired t-test and low prediction errors (Frobenius norm: 12.566-18.312), despite minor noise in IOS-based predictions.

Conclusions: This study performed preliminary validation of an IOS-based ML model for high-quality EDD prediction.

Purpose: This meta-analysis answers the research question, how does the accuracy of additive manufacturing (AM) compare to that of subtractive manufacturing (SM) for fabricating zirconia fixed dental prostheses (FDPs)?

Study selection: Relevant studies were systematically searched in PubMed, ScienceDirect, Cochrane Library, Scopus, and Web of Science and screened following the PRISMA 2020 guidelines; the inclusion criteria include studies that evaluate the accuracy of FDPs fabricated using AM and SM. Studies were excluded if they did not compare AM and SM, did not use zirconia, or did not assess accuracy. Study quality was assessed using the methodological index for nonrandomized studies, and publication bias was assessed using Egger's and Begg's tests.

Results: Sixteen in vitro studies were included. The meta-analysis revealed that FDPs fabricated via AM demonstrated significantly lower trueness compared to that of SM in the intaglio surface (P < 0.01; SMD: 1.37; 95% CI: [0.80, 1.95]; I² = 90%, P < 0.01), marginal area (P < 0.01; SMD: 1.83; 95% CI: [1.17, 2.49]; I² = 91%, P < 0.01), and external surface (P < 0.01; SMD: 2.15; 95% CI: [1.19, 3.12]; I² = 91%, P < 0.01). AM demonstrated significantly higher precision compared to that of SM (P < 0.01; SMD: -1.89; 95% CI: [-2.77, -1.01]; I² = 77%, P < 0.01).

Conclusions: AM technologies exhibit lower trueness compared to that of SM and offer superior precision. Material jetting achieves trueness comparable to that of SM. Both AM and SM satisfy clinical accuracy requirements.

Purpose: Jaw movements in sleep bruxism (SB) presumably play a functional role in salivary stimulation and oral tissue protection. This study aimed to investigate the relationships between SB, oral wetness, and salivary flow.

Methods: Participants underwent polysomnography in a sleep laboratory, during which rhythmic masticatory muscle activity (RMMA) and swallowing were recorded. The degree of oral moisture was measured before sleep, during sleep, and upon waking. The unstimulated salivary flow rate (USFR) and stimulated salivary flow rate (SSFR) were measured before sleep and upon waking. Correlations between the RMMA index, degree of oral moisture, and salivary flow were examined.

Results: Seventeen participants (10 males, 7 females, 28.2 ± 8.6 years old) were included. The degree of oral moisture and USFR were not significantly correlated with the RMMA index. The SSFR before sleep demonstrated a significant moderately negative correlation with the RMMA index (ρ = -0.637). The frequency of RMMA that occurred with swallowing per hour demonstrated a significant negative correlation with the SSFR before sleep and upon waking (ρ = -0.703, -0.527, respectively). Swallowing occurred significantly more frequently in the last one-third of the RMMA episodes, and the frequency of phasic and mixed types of RMMA that occurred with swallowing demonstrated a significant negative correlation with the SSFR before sleep (ρ = -0.583, -0.511, respectively).

Conclusions: These results suggest a relationship between SB and the ability to secrete stimulated saliva. SB may have a functional role in stimulating saliva secretion, and an increase in SSFR may alleviate SB.

Purpose: To compare abutment and scan body subsidence and determine the appropriate tightening torque value for a scan body that can accurately replicate abutment subsidence.

Methods: An internally tapered connection implant was placed in a bone model. The titanium abutment (Ti Abut), polyetheretherketone scan body (PEEK SB), and titanium scan body (Ti SB) were tightened to torque values of 10 or 35 Ncm, with the 10 Ncm models used as reference models. Both the 10 and 35 Ncm models were scanned using a laboratory scanner. The vertical displacements of the Ti Abut, PEEK SB, and Ti SB at each torque value were determined using three-dimensional analysis software.

Results: Upon tightening the scan bodies and abutment to 35 Ncm, the displacement was significantly greater than when tightened to 10 Ncm (P < 0.01). At 35 Ncm, Ti SB and Ti Abut showed significantly greater displacements than PEEK SB, whereas no significant difference was observed between Ti SB and Ti Abut.

Conclusions: The titanium scan bodies, when tightened at 35 Ncm, accurately replicated titanium abutment subsidence, unlike the PEEK scan bodies.

Purpose: To evaluate the effect of proximal box depth and adjacent tooth distance on intraoral scans for inlays.

Methods: Inlay preparation models were designed using a three-dimensional (3D) printing software (Materialise Magics) and manufactured using digital light processing. The models were categorized into three groups based on proximal box depths (4, 6, and 8 mm) and three groups according to adjacent tooth distances (1.2, 1.6, and 2.0 mm). Intraoral scans were performed 10 times using CEREC Primescan (Dentsply Sirona) and TRIOS 3 (3Shape). Reference scan data were obtained using a laboratory scanner (D900L; 3Shape). 3D comparisons between the scan data were performed using 3D analysis software (Geomagic Control X). The root mean square value was calculated to evaluate the trueness of the intraoral scans. Two-way analysis of variance and post-hoc testing with the Bonferroni correction were performed in trueness (α=0.05). Color-coded maps were obtained for the qualitative analysis of deviation.

Results: As proximal box depth increased from 4 mm to 8 mm, the deviation in trueness significantly increased. Similarly, the 1.2 mm distance group showed a greater deviation than the 1.6 and 2.0 mm distance groups. No statistically significant difference was observed between the 1.6 and 2.0 mm distance groups.

Conclusions: The accuracy of intraoral scans is affected by proximal box depth and adjacent tooth distance. A shallow proximal box and a greater distance to adjacent tooth enhance scanning accuracy. However, beyond a certain threshold, further increases in the distance from the adjacent tooth does not improve the scanning accuracy.

Purpose: To investigate the association of removable partial denture (RPD)/complete denture (CD) and fixed partial denture (FPD) use with health-related quality of life (HRQoL), evaluated using the EuroQol 5-dimension, 5-level instrument (EQ-5D-5L) among older adults with tooth loss.

Methods: Cross-sectional data from the 2022 Japan Gerontological Evaluation Study. Participants were classified as RPD/CD users, FPD users, or nonusers. Generalized linear regression models stratified by the number of teeth were used to explore the association of RPD/CD and FPD use with the HRQoL evaluated using the EQ-5D-5L. The interactions among the number of teeth, RPD/CD, and FPD use were examined.

Results: After adjusting for all covariates, RPD/CD and FPD users with 5-19 teeth had higher predicted HRQoL utility scores than nonusers (RPD/CD [n=14,297]: 0.837 vs. 0.850; FPD [n=7,476]: 0.858 vs. 0.861 [nonusers vs. users]). The interaction between number of teeth and RPD/CD and FPD use revealed that differences in HRQoL between users and nonusers were greater among those with 1-14 teeth for RPD/CD use and among those with 10-14 teeth for FPD use (RPD/CD: β = -0.008, P < 0.01; FPD: β = -0.008, P = 0.183).

Conclusions: RPD/CD and FPD users with 5-19 teeth had a higher HRQoL than nonusers, with differences appearing to depend on the number of teeth. The World Health Organization has promoted the incorporation of oral health into universal health coverage (UHC). Given the minimal HRQoL difference between CD users and nonusers among edentulous individuals, unconventional dentures may merit inclusion in UHC.

Purpose: Comminution of food into small particles through mastication is important for safe swallowing. However, few studies have evaluated the functional improvement provided by newly fabricated removable dentures in terms of changes in the comminution of food at the swallowing threshold (CF-ST). This prospective cohort study aimed to clarify the changes in CF-ST associated with the fabrication of newly removable dentures.

Methods: Eighty patients (age: 57.3 ± 11.9 years) requiring new removable dentures were enrolled. Masticatory performance (MP) and CF-ST were assessed before and after new denture insertion. MP and CF-ST were defined as the increase in surface area of 5.5 g of test gummy jelly after 30 chewing cycles and after chewing until the premeasured swallowing threshold, respectively. Other oral functions, including tongue pressure, oral diadochokinesis, and stimulated salivary flow rate, were measured concurrently. All evaluation items were compared before and after new denture insertion. Multiple regression analysis was performed to identify factors affecting changes in CF-ST.

Results: CF-ST, MP, and other oral functions significantly improved after new denture insertion. Multiple regression analysis identified changes in MP (β = 0.467), number of chewing cycles at the swallowing threshold (β = 0.322), and belonging to Eichner index C group (β = 0.245) as significant factors influencing changes in CF-ST.

Conclusions: Newly fabricated removable dentures have the potential to improve CF-ST. This improvement may result from enhanced masticatory function and changes in masticatory behavior, such as increased chewing.