Journal of prosthodontic research最新文献

Purpose: This guideline aimed to make evidence-based clinical practice guidelines for the primary treatment of temporomandibular disorders (TMDs) for general practitioners who do not specialize in TMD.

Review process: Following the principles of evidence-based medicine, a systematic review and network meta-analysis (NMA) of multiple treatments was conducted, assessing the certainty of evidence using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach. Randomized controlled trials published between January 2000 and December 2020 were included. Patients diagnosed with TMD according to the Diagnostic Criteria for Temporomandibular Disorders were considered. Myalgia, arthralgia, and maximal mouth opening were selected as outcomes, and 12 treatments were included in the NMA. The modified Delphi method was used to reach a consensus on recommendations during clinical guideline panel meetings of the Japanese Society for the Temporomandibular Joint.

Results: Self-administered mouth opening exercises, stabilization-type oral appliances, and low-level laser therapy (LLLT) were recognized as effective primary treatments, although the evidence level was graded as "very low" (Grade 2D). During the clinical guideline panel meetings, decisions were developed based on the NMA results, and recommendations for clinical practice guidelines were finalized following consensus.

Conclusions: This guideline recommends mouth opening exercises and the use of stabilization-type oral appliances as primary treatments for TMD. Additionally, it suggests that LLLT be a conditional recommendation, supplemented with additional considerations.

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: The hyoid bone plays a key role in several physiological functions by interacting with the attached muscles. Understanding its kinematics and positional stability is essential for evaluating its functions: swallowing, mastication, intraoral transport, vocalization, and respiration. This study aimed to assess the position of the hyoid bone relative to the cranial base and mandible using cephalometric imaging and to examine its stability.

Methods: Cephalometric images of 140 patients were analyzed using specialized software. The positional relationship between the cranial base and hyoid bone was assessed by measuring the Porion-Hyoid distance (Po-Hy) and the angle between the Po-Hy and the Nasion-Porion line (∠CB-Hy). The relationship between the mandible and the hyoid bone and the cervical angle was also evaluated.

Results: The ∠CB-Hy showed a narrow distribution (mean ± SD: 89.2 ± 5.12°). A weak, but statistically significant, correlation was observed between age and the ∠CB-Hy. Additionally, a significant negative correlation was found between the number of missing molars and ∠CB-Hy, while a strong positive correlation was identified between the cervical angle and ∠CB-Hy. The relationship between the cervical angle and ∠CB-Hy was represented by the following linear regression equation: ∠CB-Hy = 0.484 × Cervical angle + 37.4.

Conclusions: Our findings suggest that the hyoid bone maintains a relatively stable position with respect to the cranial base with only slight variation. However, a significant relationship exists between ∠CB-Hy and cervical inclination. Clinicians and researchers should consider this relationship when assessing the hyoid position in clinical and research settings.

Purpose: This clinical study aimed to evaluate the effects of various head positions within physiological movement limits on occlusal contacts (OCs) in digital bite registrations (BRs) obtained using an intraoral scanner (IOS).

Methods: This study included 36 individuals with natural dentition without missing teeth. Maxillary and mandibular scans were performed using an IOS (Trios4). The natural (NHP), forward (FHP), and backward (BHP) head positions were determined using a manual goniometer, and three BRs were obtained using an IOS. A new assessment method, the "digital occlusion analysis" module (oJMA, Zebris), was used to assess the OCs in these BRs. Dental arch scans and BRs were imported into the digital occlusion module. OC evaluation was performed on buccal-lingual cross-sections obtained at 1 mm intervals on the four left and right posterior teeth of the mandible. Each section was evaluated for the number, intensity, and location of OCs between pairwise comparison groups of head positions.

Results: The number of OCs significantly decreased in the BHP-FHP group with respect to contact points (P = 0.03). OC intensity was similar among the three groups. However, OC location was significantly reduced in the NHP-BHP and NHP-FHP groups compared with the NHP group, specifically for functional cusp contacts (P = 0.03, P = 0.018).

Conclusions: Digital BRs obtained in different head positions showed significant differences only in the OC locations in the FHP and BHP compared with the NHP. The effect on the number of OCs was observed as the angle between the head positions increased from FHP to BHP.

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 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: 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: 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.