Purpose: This review critically examined the impact of various whitening toothpaste formulations on color stability, surface roughness, gloss, and microhardness of dental restorative materials.

Study selection: A comprehensive literature search yielded 101 articles from PubMed, 159 from Embase, and 617 from SCOPUS, spanning 1983–2024, of which 33 met the inclusion criteria.

Results: Studies have shown that whitening toothpastes influence color change and surface characteristics. Hydrogen peroxide (HP) formulations are generally effective in achieving color alteration, although their impact on microhardness and roughness varies. Charcoal-based toothpastes tend to increase surface roughness because of their abrasive nature, whereas blue covarine toothpaste provide some brightening effects but are also associated with higher roughness. Results regarding nanohybrid and microhybrid composites were mixed; some studies found nanohybrids to be superior in color stability, whereas others favored microhybrids. However, nanohybrids are more susceptible to roughness changes due to whitening agents, whereas nanofilled composites consistently demonstrate better surface integrity under abrasive conditions.

Conclusions: These findings highlight the importance of selecting toothpaste formulations that align with restorative material properties to optimize esthetic results without compromising durability. Although HP formulations show promise in balancing whitening efficacy with surface preservation, their long-term effects require further study. Additionally, continued research is needed to refine the formulations, particularly for charcoal and blue covarine, to reduce abrasiveness and extend restoration longevity.

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: We aimed to evaluate the trueness and adaptation of the intaglio surfaces of complete denture metal frameworks fabricated using selective laser melting (SLM) with different building orientations (0°, 45°, and 90°).

Methods: Cobalt-chromium maxillary complete denture metal frameworks were fabricated at 0°, 45°, and 90° using SLM. Trueness measurements were conducted using the best-fit alignment method of three-dimensional inspection software, and adaptation was evaluated using the silicone replica technique. Nonparametric Kruskal–Wallis and Bonferroni tests were performed to determine differences among the groups (P = 0.05).

Results: No significant differences were observed in the root mean square (RMS), positive, and negative deviation values between 0° and 45° group (P > 0.05), and the median, first quartile, and third quartile of each were considered clinically acceptable. For the 90° group, the RMS, positive deviation, and negative deviation values were significantly higher than those of the other groups (P < 0.05). The overall adaptation of the 45° group was better than that of the 0° and 90° groups (P < 0.05), whereas the 0° and 90° groups showed no significant difference (P > 0.05).

Conclusions: The trueness and adaptation of the intaglio surface of cobalt-chromium maxillary complete denture metal frameworks were affected by the building orientation through SLM. Considering both trueness and adaptation, 45° is recommended as the most efficient build orientation for clinical applications.

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: With the advancement in digital technology, post-and-cores can be produced using full-digital techniques. This study aimed to evaluate the accuracy of two full-digital impression techniques for scanning the post space with different root canal entrance diameters using an intraoral scanner (IOS) (TRIOS 3) with and without a scan post, compared to the half-digital impression technique.

Methods: Standard models of three intact teeth with varying root canal entrance diameters were prepared. Fifteen post-and-core designs per tooth were created using direct IOS and IOS with scan posts, with the half-digital technique as the control. All files were exported as standard tessellation language (STL) files, and the root mean square (RMS) deviations were analyzed between the experimental and control groups. Deviations were measured at standardized points across four regions: the occlusal external, occlusal internal, middle third, and apical third.

Results: No significant differences in the overall RMS were observed among the different root canal entrance diameters (3 mm, 4 mm, and 5 mm) for direct IOS and IOS with scan posts (P > 0.05). However, an independent samples t-test revealed a significant difference (P < 0.05) in both trueness and precision between the two experimental groups, with IOS with scan posts consistently showing lower RMS values.

Conclusions: For post space lengths less than 7.4 mm in single-rooted teeth, both direct IOS and IOS with scan posts can serve as viable alternatives to half-digital techniques. However, in deeper areas, IOS with scan posts are recommended as alternatives to the half-digital technique.

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: This study aimed to investigate the association between xerostomia severity and oral health-related quality of life (OHRQoL) across various functional occlusal statuses among older adults.

Methods: This cross-sectional study recruited 202 outpatients (130 females and 72 males) from a dental university hospital in Japan. Assessments included the Summated Xerostomia Inventory (SXI) for xerostomia, Oral Health Impact Profile-14 (OHIP-14) questionnaire for OHRQoL, saliva collection, and functional occluding units (FOUs). Analyses included Mann-Whitney U tests and regression models. A directed acyclic graph was constructed to identify potential confounders and mediators and ensure appropriate adjustment in the regression models.

Results: The mean age of the participants was 73.7 (SD: 7.6) years, ranging from 60–89 years, and 64.4% were females. The median SXI score was 7 (IQR: 6-8), and 14.4% had a score of 10 or more. The participants with xerostomia had higher OHIP scores than those without xerostomia (median, 15 vs. 9; P = 0.003). Salivary flow measures were not associated with the OHIP scores. However, SXI and FOUs were associated with the OHIP scores in the regression analysis (R²=29.7%). The subgroup analysis revealed that participants with a more FOUs had a stronger association between xerostomia and OHRQoL.

Conclusions: Among the older adults in this study, those with xerostomia and fewer functional occlusions had poorer OHRQoL. The relationship between dry mouth symptoms and OHRQoL was particularly robust among patients with better functional occlusion, suggesting that xerostomia management deserves attention even in patients with well-maintained dentition.

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 study aimed to investigate the effect of light-curing on the fracture load of glass-ceramic discs bonded to dentin.

Methods: IPS e.max CAD (lithium disilicate) and Celtra Duo (zirconia-reinforced lithium silicate) glass-ceramic discs, each 7 mm in diameter, were bonded to flattened dentin using three different cementation strategies. The discs varied in thickness, measuring 0.8 mm and 1.5 mm. The three strategies implemented were as follows: (1) SBU/ULT(AL): auto-cured adhesive and light-cured resin cement, (2) SBU/ULT(LL): light-cured adhesive and light-cured resin cement, and (3) resin composite, which served as the positive control. The fracture loads of eight specimens from each group were evaluated after storing the samples for one week and one year. Data were analyzed using linear mixed-effects models with a significance level of 0.05.

Results: The thickness of the ceramic material and the cementation strategy significantly influenced the fracture load (P < 0.05). Ceramics bonded using SBU/ULT(LL) and composite cement, regardless of thickness, demonstrated significantly higher fracture loads than those bonded using SBU/ULT(AL) (P < 0.05). Ceramics with a thickness of 0.8 mm bonded with either SBU/ULT(LL) or composite cement exhibited fracture loads comparable to those of 1.5 mm thick ceramics bonded with SBU/ULT(AL) (P > 0.05).

Conclusions: Light-curing the adhesive separately from the resin cement (SBU/ULT(LL)) and employing composite cement are recommended strategies for cementing glass ceramics with dentin to enhance fracture load resistance.

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: 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 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: 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: Supports are essential for ensuring dimensional accuracy in 3D printing; however, an excessive number of supports compromises printing efficiency. This study aimed to investigate how a varying number of support arrangements affects the precision and trueness of 3D-printed dentures.

Methods: Three denture base printing files were designed, each with different numbers of supports: 40 (group 40), 55 (group 55), and 70 (group 70). Thirty samples were printed and measured across the groups. Accuracy was evaluated by assessing trueness and precision using the root mean square error (RMSE). The error areas in each group were analyzed through micro-computed tomography (micro-CT) 3D imaging.

Results: Group 70 showed a significantly lower RMSE for trueness than Group 40 (P < 0.05), but showed no significant difference from Group 55 (P ≥ 0.05). For precision, Group 70 outperformed both Groups 40 and 55 (P < 0.05), which did not differ significantly (P ≥ 0.05). Micro-CT revealed no mismatches in the palatal region. Discrepancies—areas where the supports in Groups 40 and 55 did not accurately align with those in Group 70—were predominantly observed at initiation points of overhangs in thinner sections.

Conclusions: Based on these results, this study recommends placing support structures strategically around overhangs and thin-walled areas to enhance the accuracy of 3D-printed denture fabrication. These findings indicate that optimizing support placement, rather than merely increasing the number of supports, is crucial in improving the quality and reliability of 3D-printed dental prostheses.

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.

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: This study compared the scanned data obtained from four conventional silicone impressions using a laboratory scanner to investigate the effects of impression materials on accuracy and precision.

Methods: The master model was a gauge with four small height increments constructed from an assembly of ceramic gauge blocks. Impressions of the master model were made using four silicone impression materials (Imprinsis Regular: blue; Fusion II: pink; Fit Checker: white, Imprint3: yellow). The impressions were scanned under blue light using a laboratory scanner. The points of inquiry were 1) advisability of three-dimensional (3D) reconstruction, 2) reproducibility at the surface level, and 3) microstep detectability. Data were analyzed using a one-way analysis of variance and Tukey’s multiple comparison test.

Results: 3D reconstruction was achieved for all impressions except Imprint3. The scanning performance of the impression material affected the spectral reflection factor. There was no significant difference in surface reproducibility among the three impression materials, and the detectability of small step height in Imprinsis Regular was significantly better than that in other impression materials (P < 0.05).

Conclusions: The color of the impression material affected digitization when a blue-light scanner was used. The digitization accuracy of Imprinsis Regular was higher than that of the other impression materials. However, the digitization accuracy of the three impression materials that could be 3D-reconstructed was within clinical tolerance. These findings can broaden the clinical applications of digital dentistry and mitigate the errors associated with dental materials.