Purpose: This study evaluated the use of pre-sintered cobalt-chromium (Co-Cr) alloy discs in the fabrication of clasps for removable partial dentures, comparing their accuracy and mechanical properties, as determined via tensile testing, with those of conventional fabrication methods.

Methods: Accuracy of the clasps was assessed by obtaining three-dimensional (3D) data (design data) of the Akers clasp. The clasps were fabricated under three conditions: (1) pre-sintered, fabricated from pre-sintered Co-Cr alloy discs; (2) fully sintered, fabricated from fully sintered Co-Cr alloy discs; and (3) cast, fabricated via casting. For each method, 3D data were collected (fabrication data). The design and fabrication data were subsequently superimposed, and the accuracy of the clasps was investigated based on their inner surfaces. The mechanical properties were assessed via tensile testing of dumbbell-shaped Co-Cr alloy specimens fabricated under the same conditions used for accuracy testing (pre-sintered, fully sintered, and cast).

Results: Cast clasps typically exhibited the highest trueness values and fully sintered clasps exhibited the highest precision values. The pre-sintered clasps exhibited high trueness in every part of the rest area; however, the accuracy at the clasp tip was low. In terms of mechanical properties, the pre-sintered clasps exhibited the highest elongation, meeting the standards for Type 4 metals as specified by ISO 22674:2022.

Conclusions: The present study demonstrates that pre-sintered Co-Cr alloy discs are suitable for fabrication of clasps with good fit and mechanical properties, provided that the accuracy of the clasp tip is improved.

Purpose: To evaluate stress distribution in short-crowned molars with distal subgingival defects with various restorations and materials.

Methods: Residual crowns were restored using a post-and-core crown (model A), a full crown (model B), a fissure-post endocrown (model C), an endocrown (model D), an onlay (model E), and an overlay (model F). The ceramic materials used were IPS e.max (EM), Vita Enamic (VE), and Lava Ultimate (LU). Subsequently, finite element analysis was performed by applying 600 N vertical load (0° to the long axis) and 200 N oblique load (45° to the long axis) to simulate chewing loads.

Results: As the elastic modulus of the material increased, the stress on the restorations also increased, particularly under an oblique loading condition. Under vertical and oblique loading conditions, the peak maximum principal stress (MPS) in the dentin was lowest in Group A-EM (17.28 MPa and 5.61 MPa, respectively), following the trend A < B, C < D, F < E. The MPS within the cement was lowest in Group A-EM (2.74 MPa and 2.58 MPa under vertical and oblique loading conditions, respectively). The MPS within the cement in Group H (4.11 MPa) was reduced to approximately one-third of that in Group G (12.35 MPa).

Conclusions: EM exhibited a more uniform stress distribution than other materials and is a promising material for short-crowned molars. A fissure-post endocrown design is a potentially favorable restorative option for short-crowned molars. Fiber posts should be used with full crown restorations.

Purpose: To investigate the accuracy of static and dynamic computer-aided implant surgery (s/d-CAIS) for immediate implant placement for single-tooth replacement in healthy individuals with partially edentulous zones.

Study selection: A systematic search of six electronic databases for clinical studies reporting on Type 1 implant placement identified 15 eligible articles (seven RCTs, two prospective studies, and six retrospective studies) involving 383 patients. The focus question addressed population, intervention, comparison, and outcome criteria. A meta-analysis was performed using a random-effects model to obtain pooled estimates, presented as forest plots with weighted mean differences and 95% confidence intervals. Quality assessment was conducted using the Robin-I and RoB2 tools.

Results: The meta-analysis revealed that s/d-CAIS demonstrated significantly lower global platform and apex deviation compared to freehand placement, with mean differences of -0.70 mm (95% CI -0.74, -0.66; P < 0.001) and -0.86 mm (95% CI -1.00, -0.73; P < 0.001) respectively. The mean difference in platform depth deviation was statistically significant in favor of CAIS, with a mean difference of -0.73 mm (95% CI -1.04, -0.43; P < 0.001). High heterogeneity was observed across studies. The average global coronal, global apex, and angulation deviation for d-CAIS and s-CAIS were 0.72 mm, 0.81 mm, and 2.04 degrees, and 0.80 mm, 1.10 mm, and 2.12 degrees, respectively.

Conclusions: Data on Type 1 implant placement suggest that s/d-CAIS may enhance implant placement accuracy in several dimensions compared with freehand placement, with d-CAIS demonstrating marginally better control over angulation. However, the high heterogeneity across studies with a moderate-to-high risk of bias limits the generalizability of these findings.

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: 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 investigate the optimal post-polymerization temperature and time to enhance the mechanical properties of three-dimensional (3D)-printed nanocomposites.

Methods: A control group of pure 3D-printed resin was used to fabricate specimens post-polymerized at 40 °C for 15 min (n = 6). Next, 3-wt% functionalized yttria-stabilized zirconia (YSZ) nanoparticles were dispersed in a 3D-printed resin to fabricate YSZ-based nanocomposites for the experimental groups. The post-polymerization conditions of six experimental groups (n = 6) were set as two temperatures (40 °C and 80 °C) and three time periods (30, 60, and 90 min). The degree of conversion (DC), flexural strength, modulus, fractography, and hardness values of each group were evaluated. One-way and two-way analysis of variance were applied to analyze significant differences among the control and experimental groups and interaction effect of temperature and time of post-polymerization, respectively (α = 0.05).

Results: Significant reductions in DC values were noted in the experimental groups compared to the control group. The experimental groups demonstrated significantly higher flexural strengths and moduli than those of the control group. At 80 °C, no significant differences were observed for different post-polymerization times. Compared to post-polymerization at 40 °C, the flexural strength, modulus, and hardness were significantly enhanced when the post-polymerization temperature was increased to 80 °C.

Conclusions: Optimal mechanical properties of 3D-printed YSZ-based nanocomposites could be achieved under post-polymerization at 80 °C and 30 min.

Purpose: This study evaluated biomechanical behavior of endocrown and post-core restorations produced from computer aided design/computer aided manufacturing (CAD/CAM) and traditional materials in severely damaged teeth that lack a ferrule and assessed the associated failure risk of resin cement.

Methods: A phantom maxillary central incisor and mandibular second premolar were trimmed 1 mm coronally to the cemento-enamel junction, the root canals were enlarged, and the teeth were scanned. Data were transferred to a solid modeling software. Twenty-two models were constructed, including endocrowns (hybrid ceramic, lithium disilicate, and polyetheretherketone [PEEK]) and post-cores (glass-fiber post/composite core; glass-fiber single-piece post-core; PEEK single-piece post-core; gold single-piece post-core). Hybrid ceramic and lithium disilicate crowns were modeled on the post-cores. Loads of 100 N for the central incisor and 300 N for the premolar were applied in a 45° oblique direction. von Mises stresses were analyzed on both root dentin and restorations, and the failure risks for the resin cement were calculated.

Results: The highest stresses were found at the roots of the PEEK endocrown (37.6 MPa) for the central incisor and of the lithium disilicate endocrown for the premolar (40.0 MPa) among endocrown groups. PEEK endocrowns had the lowest stress within the restoration and presented a higher risk of cement failure. The glass-fiber post/composite core groups demonstrated the highest adhesive and cohesive failure risks for post cement.

Conclusions: For the central incisor and mandibular premolar, lithium disilicate and PEEK endocrowns, respectively, generated less stress at the root. However, PEEK endocrowns had a higher risk of cement failure.

Purpose: Human flourishing is a multidimensional concept that encompasses happiness and life satisfaction (happiness), mental and physical health (health), meaning and purpose (purpose), character and virtue (character), and close social relationships (social), which are characterized by comprehensive well-being. This cross-sectional study investigated the association of oral health, number of remaining teeth, and prosthesis use with multidimensional flourishing.

Methods: Data was sourced from the 2022 wave of the Japan Gerontological Evaluation Study, a population-based survey of independent individuals aged 65 years or older. This study utilized multilevel linear regression with multiple imputations. The covariates included sex, age, income, education, marital status, smoking status, diabetes history, instrumental activities of daily living, and depressive symptoms.

Results: This study included 87,201 participants with a mean age of 74.87 years [standard deviation (SD)=6.30], and mean±SD composite flourishing index of 6.77±1.64. Multilevel multivariable regression showed that individuals with dental prostheses or more teeth had a higher flourishing index. Among individuals without dental prostheses, those with >20 teeth showed a composite flourishing index of 0.34 units higher (95% confidence interval (95% CI): 0.26-0.42, P < 0.001) than those with 0-9 teeth. Among those with 0-9 teeth, individuals with dental prostheses showed 0.21 (95% CI: 0.12-0.29, P < 0.001) higher units compared to those without prostheses. The interaction analysis showed that dental prosthesis use was significantly associated with higher indices, especially among those with fewer teeth.

Conclusions: Teeth and prostheses were independently associated with multidimensional flourishing. Using dental prostheses may enhance multidimensional flourishing among individuals with fewer remaining teeth.

Purpose: This study aimed to investigate the association between denture restoration and cognitive impairment through a meta-analysis and to assess the correlation between different degrees of tooth loss.

Study selection: Observational studies exploring the association between denture restoration and cognitive function were systematically searched across six databases from January 2000 to January 2024. Two researchers independently searched electronic databases and extracted relevant studies from all articles.

Results: This study included 24,252 participants from six observational studies. The risk ratio and 95% confidence interval (CI) were used to compare the risk of cognitive impairment. Participants who experienced tooth loss without dentures had a 1.27-fold (95% CI: 1.20–1.38) higher risk of cognitive impairment, whereas those with dentures had only a 1.01-fold (95% CI: 0.92–1.12) higher risk. In the dose-response analysis, the risk of cognitive impairment in the non-denture group increased by 1.009 times (95% CI: 1.006–1.012) for each tooth lost, whereas the denture restoration group showed a 1.003 times (95% CI: 1.000–1.006) increased risk. The years of follow-up and clinical measurement tools simultaneously explained this heterogeneity.

Conclusions: This study provides detailed evidence of a potential association between denture restoration and a reduced risk of cognitive impairment. Furthermore, there was a correlation between denture restoration and a reduced impact of the number of teeth lost on the risk of cognitive impairment. Therefore, timely and reasonable denture restoration may contribute to prevent cognitive impairment.

Purpose: In this cross-sectional study, we aimed to investigate the association among dietary diversity, ingestible food profiles, and the type of prosthodontic treatment (i.e., removable partial or complete dentures [RD] vs. implant-supported dentures [ID], including implant-supported fixed prostheses and implant-assisted overdentures) in older Japanese outpatients.

Methods: We included 297 patients aged ≥65 years (mean age, 75.3 years) undergoing maintenance therapy for RD or ID. Dietary diversity was assessed using the Dietary Variety Score (DVS) questionnaire. The ingestible food profile, a subjective quantification of the ability to consume foods with high masticatory difficulty, was evaluated using a validated ingestible food questionnaire and assessed using the ingestible food score (IFS). DVS- and IFS-related factors were identified using multiple regression analyses.

Results: The median IFS of the ID group (100.0) was significantly higher than that of the RD group (84.5); however, the median DVS showed no statistically significant difference between the two groups. After adjusting for confounding factors, prosthodontic treatment type (RD) and the number of present teeth (≤20) were found to be significantly associated with low IFS, whereas young age and presence of cardiovascular disease were significantly associated with low DVS.

Conclusions: Older individuals with ID had a better ingestible food profile than those with RD; however, dietary diversity did not differ significantly between the two groups. RD is a potential risk factor for poor ingestible food profile, whereas the prosthodontic treatment type is not a direct risk factor for low dietary diversity.

Purpose: Spark-discharged anodic oxidation coating on commercially pure titanium (SAc.p.Ti) has been shown to promote bone conduction and bone matrix mineralization during new bone formation. This study hypothesized that the combination of SAc.p.Ti with dental pulp stem cells (DPSCs) would enhance new bone formation. The objective was to evaluate the effect of this combination in a rat bone defect model.

Methods: DPSCs were isolated from Sprague–Dawley (SD) rat incisors and cultured. Calvarial bone defects were created in SD rats, followed by transplantation of commercially pure titanium (c.p.Ti), SAc.p.Ti, or SAc.p.Ti combined with DPSCs. Bone formation was assessed using micro-computed tomography (micro-CT). Toluidine blue O staining was employed to evaluate bone-implant contact and the newly formed bone area. Hematoxylin–eosin (HE) staining was performed to identify osteoblast-like cells.

Results: Micro-CT analysis revealed hard tissue formation on the surface of SAc.p.Ti. Toluidine blue O staining showed significantly greater bone-implant contact and newly formed bone area in the SAc.p.Ti/DPSC group compared to the c.p.Ti and SAc.p.Ti groups. HE staining confirmed the presence of osteoblast-like cells at the defect margins, with evidence of new bone formation on the surface of SAc.p.Ti and in the SAc.p.Ti/DPSC groups.

Conclusions: The combination of SAc.p.Ti and DPSCs presents a promising strategy for promoting new bone formation in rat calvarial defect model.

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: 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: This study examined the effect of assistive device use on the precision of digital impressions for multiple implants placed in a fully edentulous maxilla in vivo.

Methods: A total of eight participants with fully edentulous maxillae and four implants at position #15, #12, #22, and #25 were included in the study. The assistive device was made using CAD/CAM technology. Digital impressions were obtained using an intraoral scanner with (AD+) and without (AD-) the assistive device that attached to the scan bodies. Each participant underwent five digital and conventional impressions (verification casts (VC)). Dimensional deviations for each impression method were measured using the least-squares best-fit method to assess precision. Statistical analysis was performed using one-way analysis of variance (ANOVA) with Tukey’s post-hoc adjustments for multiple comparisons.

Results: The dimensional deviations were as follows: AD- (37.56 ± 7.43 µm), AD+ (16.23 ± 2.56 µm), and VC (26.48 ± 5.13 µm). One-way ANOVA revealed significant differences between the groups (F = 31.04, P < 0.0001), which remained after Tukey adjustment (P < 0.01). The AD+ group exhibited the highest precision, while the AD- group had the lowest.

Conclusions: For implants placed in a fully edentulous maxilla in vivo, digital impressions with assistive devices demonstrated superior precision compared with those obtained without assistive devices or conventional impressions obtained with an implant indexing device.

Purpose: To determine the effects of K18 quaternary ammonium methacryloxy silane (QAS) on tissue conditioner materials and their antimicrobial properties.

Methods: 30% K18 QAS in methyl methacrylate (MMA; K18-MMA; 0%, 15%, and 20% w/w) was incorporated into a commercial tissue conditioner (Coe comfort). The degree of curing (Shore A hardness), hydrophilicity (contact angle), flow, liquid sorption, mass loss, and antimicrobial properties of Streptococcus mutans, Streptococcus sanguinis, and Candida albicans were determined. Statistical analysis included analysis of variance with Tukey HSD and Kruskal–Wallis with Bonferroni correction.

Results: Hardness increased significantly at higher K18-MMA concentrations. The contact angles did not differ between the groups. Although the control and K18-containing tissue conditioner flow decreased significantly at each successive time point and with increasing K18 QAS MMA concentration, the flow was still within the ISO 10139-1 specifications for class 2 (high-flow) soft lining materials until 2 min 30 s. The highest liquid sorption happened between 1 and 4 weeks. The controls absorbed more acid than water or base, and the K18 groups absorbed more water and acid than base. With increasing K18-MMA concentration, the mass loss increased at all times and in all three media, except in base, after 4 weeks. Both 15% and 20% K18-MMA showed significant antimicrobial activity against S. mutans, S. sanguinis, and C. albicans.

Conclusions: K18-MMA imparted significant antimicrobial properties to tissue conditioners against S. mutans, S. sanguinis, and C. albicans without compromising the flow, hardness, or hydrophilicity. However, K18-MMA addition led to increased water sorption and mass loss after 4 weeks.

Patient: A 26-year-old man with localized tooth wear and demand for aesthetic rehabilitation of the anterior teeth presented to our department. The patient reported excessive consumption of energy drinks. Furthermore, multiple trauma and tooth fractures have occurred in the past.

Discussion: In the present case, three-dimensional (3D)-printed restorations were used to restore the vertical dimensions according to the Dahl concept. An indirect build-up using noninvasive restorations has been demonstrated to be beneficial due to its pleasing aesthetic outcome and the advantage of the 3D printing process. Adhesive bonding was adapted from previous studies using direct composite materials. Thus far, whether, and to what extent, the color of these restorations changes remains unclear. Furthermore, the material wear should be evaluated in future studies.

Conclusions: Moreover, 3D-printed, noninvasive restorations made of a computer-aided design/computer-aided manufacturing hybrid material are suitable for the application of the Dahl concept. Aesthetic improvement in combination with minimally invasive pretreatment of the teeth and subsequent noninvasive restorations led to the rehabilitation of the vertical dimension of occlusion. After a follow-up period of two years, harmonious occlusal conditions were observed in the posterior region.

Purpose: This study investigated the bond strength between short fiber-reinforced resin composite (SFC) and dentin following air abrasion with various types of abrasive particles.

Methods: A total of 120 human molars were prepared for a shear bond strength (SBS) test of the resin composite. The teeth were divided into 12 groups (n = 10/group) based on the air abrasion particle used. Half of the groups underwent phosphoric acid etching (10 s) prior to air abrasion, while the other half received no pretreatment. Air abrasion was performed using five types of particles, after which a two-part adhesive (G2 Bond) and SFC were applied on the treated surfaces. The SBS test was performed using a universal testing machine at a crosshead speed of 1.0 mm/min until failure. Two additional specimens from each group were prepared to evaluate the air abraded surface using scanning electron microscopy after being stored in simulated body fluid (SBF) for two weeks. Statistical analysis was performed using two-way analysis of variance and the Tukey test (α = 0.05).

Results: The highest SBS values were observed in the control group (18.9 MPa), which did not undergo air abrasion. The use of different air abrasion particles affected the SBS of SFC to dentin (P < 0.05), as air abrasion with jet sand in the absence of pre-etching differed significantly from the other Cojet group (P < 0.05).

Conclusions: Air abrasion with various particles did not improve the bond strength between the SFC and dentin.

Purpose: This retrospective clinical study aimed to evaluate the clinical outcomes of surveyed monolithic computer-aided design and computer-aided manufacturing (CAD/CAM) zirconia crowns for abutment teeth in removable partial dentures (RPDs).

Methods: Patients who received monolithic surveyed zirconia crowns were clinically examined. The crowns were examined according to the modified United States Public Health Service criteria, and Kaplan-Meier survival was determined. The effect of different variables on the survival and success rates was assessed using Cox regression analysis (α = 0.05).

Results: A total of 297 crowns of 275 patients were evaluated over a mean period of 7 years. The cumulative survival and success rates were 95.6% and 91.2%, respectively. Complications were in the form of secondary caries (n=12), minor chipping (n=9), and debonding (n=5). A higher number of failures was observed in the mandibular molars (P < 0.05).

Conclusions: Surveyed monolithic zirconia crowns demonstrated high survival after 7 years of service. Monolithic zirconia is an excellent alternative to metal ceramic crowns for RPD abutments.

Purpose: This systematic review evaluated the effect of different printing orientations on the physical-mechanical properties and accuracy of resin denture bases and related specimens.

Study selection: Utilizing PRISMA 2020 guidelines, a comprehensive search of PubMed, Web of Science, Cochrane, and Scopus databases was conducted until June 2024. Included studies examined the accuracy, volumetric changes, and mechanical or physical properties of 3D-printed denture bases in various orientations. Studies without relevant data were excluded. Bias risk was assessed using a modified CONSORT checklist.

Results: This review included 24 studies on 3D-printed denture base resins, mainly based on stereolithography and digital light processing. Horizontal orientation (0°) generally enhanced flexural strength, while tilted and vertical orientations (90°) reduced it. Microhardness results varied due to differences in materials, layer thicknesses, and post-curing. Surface roughness was highest at 45°. Vertical orientation uses less material but is less time-efficient. Microbial adhesion, influenced by surface roughness, varied with printing orientation without a clear consensus on the optimal direction.

Conclusions: Printing orientation significantly impacts the physical and mechanical properties and accuracy of 3D-printed resin dentures. A horizontal orientation (0°) improved flexural strength, while accuracy and adaptability were better at 45° and 90°. Surface roughness, translucency, and chemical stability are also affected by orientation, post-curing, and material choice. Although a 90° orientation reduces material use, it increases printing time. Standardized study designs are recommended for drawing definitive conclusions in future research.

Purpose: We aimed to analyze the influence of different designs (inlay, onlay, and crown) on stress distribution and crack propagation in an endodontically treated cracked premolar.

Methods: Three-dimensional (3D) finite element analysis (FEA) was employed to model an endodontically treated cracked premolar with three different restorations (inlay, onlay, and crown). Six types of loadings (vertical loading of 600 N; hot thermal-600 N vertical coupling loading; cold thermal-600 N vertical coupling loading; oblique loading of 200 N; hot thermal-200 N oblique coupling loading; cold thermal-200 N oblique coupling loading) were applied to simulate the hot and cold food/beverages intake. The Von-Mises Stress (VMS) on the lower margin of the crack surface was measured at 20 points in each model, and the position of the stress concentration on the crack surface was analyzed.

Results: All three restoration types effectively improved stress distribution. The influence of different restorative modalities on the stress distribution at the crack tip exhibited different trends under different loading conditions. Lateral loading and/or hot thermal cycling increased the intensity of VMS, and crown restoration exhibited the highest stress concentration at the crack tip under lateral loading and hot thermal cycling.

Conclusions: From a mechanical perspective, the outcome of this study suggested that a full crown restoration is not the optimal choice for preventing further crack propagation. Additionally, it is recommended to reduce the consumption of excessively hot foods and beverages daily.

Patients: Three residents of a long-term care home volunteered to participate in a rehabilitation program involving a virtual reality blowgun game. The participants played the game 5 days a week as a new exercise routine. After 4 weeks of intervention, tongue pressure and forced expiratory volume in 1 s improved in all participants. In addition, the jaw-opening force and forced expiratory volume in 6 s improved in two participants. All three participants rated the virtual reality blowgun game as more enjoyable than their regular rehabilitation programs.

Discussion: Previous studies have shown that gamification can be useful in dysphagia rehabilitation. However, there are no previous reports describing the use of virtual reality in rehabilitation programs aimed at improving swallowing and respiratory functions in older adults while investigating participant motivation. The outcomes of the cases described herein suggest that such programs can be as effective as conventional expiratory training. Furthermore, gamification can enhance enjoyment, even in exercises designed to improve physical function.

Conclusions: These cases indicate that the virtual reality blowgun game may effectively improve swallowing and respiratory functions in older adults while being enjoyable.

Purpose: This study investigated the effects of femtosecond laser (FL) irradiation on the surface roughness and shear bond strength of high-translucency zirconia (6 mol% yttria-partially stabilized zirconia [6Y-PSZ]) and lithium disilicate (Li₂SiO₃) glass ceramics.

Methods: Fully sintered square-shaped specimens of 6Y-PSZ (7 groups; 20 specimens/group) and Li₂SiO₃ (8 groups; 20 specimens/group) were surface-treated via sandblasting (50-μm alumina sand or glass beads) or FL irradiation (20- or 40-μm dot or cross-line patterns) or using Monobond Etch & Prime (Ivoclar Vivadent AG; only for Li₂SiO₃ specimens). The surface roughness (arithmetic average [Sa] and developed interfacial area ratio [Sdr]) and shear bond strength after 24 h and 10,000 thermal cycles were measured and statistically analyzed.

Results: The surface roughness of both ceramics significantly increased after 40-μm cross-line FL irradiation. The Sdr also significantly increased after FL irradiation. The 20- and 40-μm cross-line laser-irradiated 6Y-PSZ samples showed the highest shear bond strength after 24 h and 10,000 thermal cycles, respectively. Li₂SiO₃ glass-ceramic specimens showed the highest shear bond strength after Monobond Etch & Prime treatment for both groups. The 40-μm cross-line laser-irradiated Li₂SiO₃ glass-ceramic specimens exhibited high shear bond strength after thermal cycling.

Conclusions: FL significantly increases the bonding efficacy of 6Y-PSZ and Li₂SiO₃ glass ceramics. Furthermore, Monobond Etch & Prime is effective for the surface treatment of Li₂SiO₃ glass ceramics. Therefore, FL can be used to effectively treat the surfaces of dental restorations in clinical settings, facilitating enhanced adhesion between the restoration and the tooth.

Purpose: Several studies have reported a close association between periodontal disease (PD) and diabetes mellitus (DM). In addition, the decline in masticatory function due to decreased occlusal support may worsen DM due to poor nutritional intake. We aimed to elucidate the relationship between PD, decreased occlusal support, and DM.

Methods: We surveyed 968 participants (411 men and 557 women) aged 50–79 years in the Suita study. An oral glucose tolerance test was performed with 75 g glucose, and fasting and 2 h post-challenge plasma glucose levels were measured. The participants were classified into following four groups: normal glucose tolerance, impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and DM. Occlusal support was evaluated by the Eichner Index. PD was assessed using the Community Periodontal Index, and participants were classified into two groups: without PD and with PD. Logistic regression analysis was performed using the incidence of IFG, IGT, and DM as objective variables in the without PD and PD groups.

Results: In the without PD group, body mass index (BMI) was significantly associated with IFG, IGT, and DM, and a history of hypertension was significantly associated with DM. In the PD group, male sex and BMI were significantly associated with IGT and DM, a history of hypertension was significantly associated with DM, and decreased occlusal support was significantly associated with IGT and DM.

Conclusions: Decreased occlusal support was associated with DM in patients with PD.

Purpose: Restoring ferrule-lacking, noncircular canal endodontically treated teeth (ETT) poses challenges owing to the increased susceptibility to root fracture and post dislodgement. We aimed to evaluate the influence of different post and core materials on the stress distribution and maximum Von Mises stress in ETT.

Methods: Four three-dimensional models were generated using different customized post and core materials: gold alloy, resin nanoceramic, polyetheretherketone (PEEK), and polyetherketoneketone (PEKK). A static load of 200 N was applied at an angle of 45 ° to the occlusal surface. The stress distribution and maximum Von Mises stress were analyzed using finite element analysis.

Results: The stress distribution patterns in all the models were concentrated in the tooth structure, post and core, and cortical bone. The gold model exhibited stress accumulation predominantly on the buccal side along the post length, with the highest maximum Von Mises stress value (330.69 MPa). The resin nanoceramic model exhibited an even stress distribution. The PEEK and PEKK models showed stress transfer to adjacent structures with the lowest maximum Von Mises stress values in the post and core sections (21.50 MPa and 29.46 MPa, respectively).

Conclusions: Different post and core materials influenced the stress distribution and maximum Von Mises stress values in ferrule-lacking, noncircular canal ETT. Resin nanoceramics have emerged as promising alternative materials, exhibiting an even stress distribution owing to their similar elasticity to dentin, thus potentially mitigating the risk of root fracture and post debonding.

Purpose: To perform vertical bone augmentation on rat parietal bone by coating the inner surface of dense polytetrafluoroethylene (d-PTFE) domes with hydroxyapatite (HA) using Erbium Yttrium Aluminum Garnet (Er:YAG) pulsed laser deposition in a rat model.

Methods: The d-PTFE plate surface, α-tricalcium phosphate (α-TCP) coating, and HA coating were measured using scanning electron microscopy and X-ray diffraction to confirm the replacement of α-TCP with HA via high-pressure steam sterilization. The dome was glued to the center of the rat parietal bone and closed with periosteal and epithelial sutures. The rats were euthanized at 4, 8, and 12 weeks postoperatively, and the d-PTFE dome and surrounding tissues were harvested for radiological and histological evaluation.

Results: In a group without HA coating (control group), a small amount of layered neosteum was observed in the d-PTFE dome. Conversely, a new balloon-shaped bone was observed in a HA-coated group (experimental group). Bone growth and number of bone beams were higher in the HA-coated group from 4 to 12 weeks postoperatively than those in the control group. However, no significant differences in bone mineral density values or bone bridge widths were observed.

Conclusions: The HA coating enhanced bone augmentation without bone replacement. Histological findings indicated that the new bone comprised normal bone tissue with cartilage lumen and matrix. Therefore, our results indicate that bone augmentation with a HA coating may be mediated by endochondral ossification, a process similar to that of ectopic ossification.

Purpose: The basal bone of the anterior maxilla plays a crucial role in maintaining primary stability of immediate implants. However, no consensus exists on the relationship between basal bone width and immediate implant success, unlike for basal bone length. This study presents a clinical scheme to predict the primary stability of immediate implants using the basal bone width.

Methods: Cone-beam computed tomography (CBCT) images were acquired from 1000 patients to determine the quantitative characteristics of the basal bone of the anterior maxilla. Basal bone dimensions, including the length and width along the tooth and bone axes, and immediate implant-related hard tissue indices, were measured on the sagittal sections. Descriptive statistics, frequency, multiple correlation, and canonical correlation analyses were performed.

Results: Basal bone indices were significantly greater in men than in women and exhibited different patterns of change with increasing age. Canonical correlation analyses revealed that the basal bone indices, especially basal bone width, correlated with other immediate implant-related indicators, among which the total width of the basal bone at 2 mm apical to the apex (Apical-2mm) exhibited the greatest contribution. Apical-2mm was positively correlated with the coronal bone dimensions, apical bone dimensions, basal bone length, and angulation.

Conclusions: The basal bone width of the maxillary anterior tooth may reflect the distribution of other implant-related anatomical indices, which may provide an additional reference for predicting the primary stability of an immediate implant.

Purpose: This retrospective cohort study evaluated the accuracy of analog versus virtual wax-ups in prosthetic-driven planning and guided surgery.

Methods: There were 73 patients with a single missing posterior tooth who underwent either an analog or virtual wax-up design following a prosthetic-driven concept. Intraoral scans of the final restoration were performed 1 year after completion of the restoration. The accuracy was assessed by comparing the deviation between the final restoration and the wax-up (analog or virtual) of each patient at the prosthetic level. The maximum deviation in six areas (buccal top, buccal mid, buccal bottom, lingual top, lingual mid, and lingual bottom) was recorded. The accuracy was also assessed at the implant level by comparing the deviation between the virtual new implant position, which was redesigned based on the final restoration as the new wax-up, and the planned position. The mean deviations in the coronal, apical, angular, and depth measurements were recorded. A two-tailed independent t-test and a one-way analysis of variance were used.

Results: Statistically significant differences were observed between the buccal (P = 0.03) and lingual tops (P = 0.03) at the prosthetic level. Significant differences were observed in the angular (P < 0.01) and coronal (P = 0.01) deviations at the implant level. There were smaller deviations between the analog wax-ups and final restorations regardless of the prosthetic or implant level.

Conclusions: Analog wax-ups were preferable to virtual wax-ups for preoperative design in computer-guided implant surgery.

Purpose: This study aimed to explore the association between oral function and mental health status in older adults and to determine the potential mediating roles of fruit and vegetable intake and social interaction.

Methods: This cross-sectional study included 478 community-dwelling older adults aged ≥75 years in Japan. Oral functions (occlusal force, masticatory performance, tongue pressure, tongue-lip motor function, and swallowing function), mental health status, dietary assessment, frequency of outings and interactions with others, and the following confounders were evaluated: educational level, financial satisfaction, residential status, comorbidities, and cognitive function. Structural equation modeling was used to assess the following: (a) a basic model, which hypothesized that oral function has a direct effect on mental health status, and (b) a mediation model, which hypothesized that fruit and vegetable intake and social interaction have potential mediating effects on the association between oral function and mental health status.

Results: The basic model revealed a positive direct association between oral function and mental health status (standardized coefficient = 0.10, P = 0.04). Fruit and vegetable intake and social interactions were identified as mediators; however, no direct association with oral function was observed in the mediation model (P = 0.28), indicating that oral function was indirectly associated with mental health status through the mediating effects of fruit and vegetable intake and social interactions.

Conclusions: Oral function showed a significant association with mental health status in community-dwelling older adults. Fruit and vegetable intake along with social interactions mediate this relationship.

Purpose: To compare the stress distribution in loaded zirconia resin-bonded fixed dental prostheses (RBFDPs) and periodontal tissue using finite element analysis, considering reduced alveolar bone levels and the number of retainers.

Methods: A human skull was micro-CT scanned. Three framework designs were tested: a 2-unit RBFDP using the maxillary left central incisor (#21) as an abutment, another using a canine (#23), and a 3-unit RBFDP using both #21 and #23. The models were categorized based on the distance from the cemento-enamel junction (CEJ) to the alveolar bone: M1 (1 mm), M2 (2 mm), M4 (4 mm), M6 (6 mm), and M8 (8 mm).

Results: The shear stresses in the adhesive resin cement were lower in the 2-unit designs than in the 3-unit design in the M4–M8 models. The maximum principal stresses in the framework were smaller in the 2-unit design than in the 3-unit design for all models. The maximum principal strains in the periodontal ligament and trabecular bone in #21 were greater in the 2-units than in the 3-units in the M4–M8 models.

Conclusions: This study suggests that cantilever RBFDPs may have a lower risk of framework fracture than 2-retainer RBFDPs, regardless of the reduction in alveolar bone levels. In cases with alveolar bone levels >4 mm below the CEJ, the cantilever RBFDPs had a smaller risk of debonding than the 2-retainer RBFDPs; however, it may increase the damage to periodontal tissue.

Purpose: Psoriasis is a complex, chronic inflammatory keratosis of unclear origin that is challenging to treat. In patients with psoriasis suspected of having metal allergies, the removal of oral metallic prostheses contributes to the alleviation of psoriasis symptoms. However, the relationship and mechanism of the metal removal effect and improvement in psoriasis symptoms in patients with metal allergies are unknown. This study aimed to investigate the relationship between metal allergies and psoriasis using an animal model.

Methods: In the metal allergy model, 4-week-old rats were sensitized and treated with nickel (II) chloride (NiCl₂) solution (provocation model). In the psoriasis model, imiquimod (IMQ) cream was applied to the shaved dorsal skin of rats (IMQ model). To create a psoriasis/metal-allergy composite rat model, we combined the provocation and IMQ models (provocation + IMQ model). Macroscopic observation, histological analysis, and quantitative gene expression analyses were performed to evaluate outcomes.

Results: In the IMQ model, psoriasis-like symptoms were visually observed from day 2 to day 9. In the provocation + IMQ model, psoriasis-like symptoms persisted for at least 11 days. Histological analysis revealed epidermal thickening and an increase in the number of interleukin (IL)-17-positive cells in the provocation + IMQ model on days 7 and 9. The gene expression of IL-17 in the submandibular lymph nodes and spleen increased in the provocation + IMQ model.

Conclusions: The induced state of Ni allergy may contribute to the maintenance of psoriasis pathology through IL-17 activity.

Purpose: Artificial intelligence (AI) may be used to learn and predict the maxillomandibular relationship, particularly when the number of occluding teeth pairs is insufficient. This study aimed to investigate the feasibility of training a new two-stage coarse-to-fine teeth alignment pipeline AI system in predicting maxillomandibular relationships based on the occlusal morphology of antagonistic teeth.

Methods: Maxillary and mandibular stone casts were collected and scanned at the maximal intercuspal position (MIP). A deep learning alignment network was trained using 90% of cast pairs. The remaining 10% of pairs were input into the trained AI system for validation. The maxillomandibular relationships predicted by the AI system were superimposed and compared with those of the mounted casts. Cartesian x-, y-, and z-coordinates were defined for each mandibular tooth scan with respect to (w.r.t.) its occlusal plane and dental midline. The discrepancy in the position of maxillary teeth scans was described based on rotation and translation.

Results: A total of 325 pairs of maxillary and mandibular stone casts were collected, with 300 pairs used for training and 25 for validation. For the AI-predicted maxillomandibular relationship, the mean rotational discrepancies w.r.t. the x-, y-, and z-axis were 1.407°±1.548°, 1.269°±8.476°, and 0.730°±1.334°, respectively. The mean translational discrepancies w.r.t. the x-, y-, and z-axis were 0.185±1.324 mm, 1.222±0.848 mm, -1.034±0.273 mm, respectively.

Conclusions: The AI-predicted maxillomandibular relationship for maxillary and mandibular teeth scans shows discrepancies of less than 1.3 mm and 1.5° compared to the actual relationships.

Purpose: The primary aim of this study was to determine the continuation and success rates of oral appliance (OA) therapy for patients in whom continuous positive airway pressure (CPAP) therapy failed. The secondary aim was to identify predictive factors for the long-term use of OA in patients with CPAP failure.

Methods: A total of 81 patients who failed with CPAP use were included in this study. Patients who had been using OA for more than 1 year at follow-up visits were assigned to Group S, whereas those who discontinued OA or were lost to follow-up within 1 year were assigned to Group D. We investigated the continuation and success rates of OA therapy, as well as predictive factors for its long-term use for those with CPAP failure.

Results: Of the 81 patients, 60 were in Group S and 21 were in Group D; 74.0% of patients with CPAP failure continued OA therapy for more than 1 year. The apnea-hypopnea index was reduced from 41.3±21.7/h to 12.4±6.5/h with OA therapy. The only significant predictor of long-term OA use in patients with CPAP failure was awareness of the effectiveness of OA therapy after 1 month (P = 0.003, odds ratio: 9.731, 95% confidence interval: 2.146–44.119).

Conclusions: Patients who recognized the effectiveness of OA treatment in the early stages were more likely to continue using OA therapy long-term.

Purpose: To determine the effect of wall thickness on the fracture load of hollow-structured zirconia teeth fabricated using 3D printing.

Methods: The geometry of an artificial ceramic tooth (mandibular right first molar) was copied and modified. The final test group design yielded wall thicknesses of 0.30, 0.50, 0.75, and 1.00 mm. Twenty zirconia specimens from each group were fabricated using a 3D printer. Artificial teeth were divided into subgroups of teeth that remained hollow (hollow teeth) or were filled with resin (filled teeth). Fracture load tests were performed, and each artificial tooth was examined using a digital microscope. Analysis of variance was used to compare the fracture resistance of the artificial zirconia teeth among the conditions, followed by pairwise Tukey’s tests. T-tests were used to compare the fracture resistance between the hollow and filled teeth within the test groups.

Results: The fracture resistance of artificial zirconia teeth decreased significantly (P < 0.001) with decreasing wall thickness. The mean fracture load reached ≥500 N for wall thicknesses of 0.75 mm and 1.00 mm. Resin filling of crowns significantly improved the fracture load of very thin walls. Microscopy revealed that most occlusal surfaces of the hollow teeth were completely fractured, whereas all the fracture surfaces of the filled teeth were incompletely fractured.

Conclusions: Artificial zirconia teeth offer sufficient fracture resistance for clinical use when the wall thickness is ≥0.75 mm, regardless of the presence of resin filling.