Purpose: Effective caries prevention management requires sustained oral health maintenance and patient motivation. Despite universal healthcare, Japan continues to report low dental check-up rates, highlighting the need for effective risk assessment and preventive strategies. This study applied the caries management by risk assessment (CAMBRA) protocol to evaluate caries risk and examined the impact of key assessment criteria.

Methods: A total of 114 patients (mean age: 61.5 ± 17.2 years) who visited the Departments of Conservative and Prosthetic Dentistry at Asahi University Medical and Dental Center between February and June 2024 were enrolled. Dental hygienists conducted structured interviews to assess oral hygiene and dietary habits. Caries risk was categorized into four levels (Low, Middle, High, and Extreme) based on CAMBRA criteria. The association between salivary flow and caries risk was analyzed using the Fisher-Freeman-Halton exact test (SPSS ver. 28).

Results: Among participants, 86.0% were classified as High or Extreme risk, with the high risk group comprising 53.5%. A significant association was found between reduced salivary flow and elevated caries risk (P < 0.05). However, no significant difference in salivary flow rate was observed across age groups.

Conclusion: For patients at elevated risk, targeted interventions such as dietary guidance and fluoride application are essential. Although xylitol gum is recommended, adherence remains low, emphasizing the need for more effective behavioral change strategies. Moving forward, a personalized caries prevention protocol, adapted from the CAMBRA model and tailored to Japan’s dental care context, should be developed.

Purpose: This study investigated bonding behavior of three resin cements to three dental substrates under dry and moist conditions, to explore material-dependent differences in bond strength in clinically relevant conditions.

Methods: Disk specimens (10 × 10 × 5 mm) of zirconia, build-up resin, and dentin were bonded to stainless-steel rods (5 mm diameter) with respective cements—RelyX Universal Resin Cement (UV), Panavia V5 (PV), or Super-Bond EX (SB)—after manufacturer-specified priming. Bonding was performed on dry or moist surfaces. Half the specimens were tested after 24 h in 37°C water; the remainder underwent 20,000 thermal cycling (5/55°C). Tensile bond strength (n = 11) was measured at 2 mm/min. Failure modes were classified stereomicroscopically. Nonparametric tests were employed (Mann-Whitney U for two groups, Kruskal-Wallis/Dunn for multiple groups). Debonded specimens prior to the bonding test were included as 0 MPa in the analysis.

Results: Under dry 24 h conditions, all cements bonded strongly to each substrate. After thermal cycling, bond strength significantly decreased for UV and PV on zirconia (P < 0.05), while SB showed no significant change. Under moist conditions, PV and UV exhibited significantly lower bond strength on both build-up resin and dentin (P < 0.05), with frequent interfacial failures. SB maintained high bond strength regardless of moisture or thermal cycling.

Conclusion: Bonding under a moist environment significantly affected the bond strengths and fracture modes for UV and PV, especially after thermal cycling. SB demonstrated high resistance to moisture and thermal stress, maintaining stable bond strength across all substrates.

Purpose: Swallowing is a complex biomechanical process requiring coordinated action of multiple anatomical structures. Traditional analyses classify swallowing into four functional phases based on bolus transit, but lack precise structural correlations. This study aimed to evaluate swallowing dynamics by redefining phase classification according to hyoid bone kinematics and visualizing coordinated motion of swallowing-related organs using four-dimensional computed tomography (4D-CT) and deep learning-based segmentation.

Methods: Ten healthy adults (aged 26-66 years) underwent 4D-CT scanning during mastication and swallowing of contrast-enhanced gummy jellies. A deep learning model based on the nnU-Net framework automatically segmented nine anatomical structures, including the hyoid bone, tongue, and soft palate. Swallowing phases were redefined using four static hyoid positions (SP1-SP4) and their corresponding dynamic intervals (SS1-SS4).

Results: The 4D-CT analysis successfully visualized dynamic movements of the hyoid bone, epiglottis, and other soft tissues across all stages. In most subjects, velopharyngeal closure by soft palate elevation was observed during SP2, and subsequently, the food bolus entered the pharynx during anterior hyoid translation (SP3). In elderly subjects wearing removable complete dentures and in those with posterior tooth loss, premature or delayed pharyngeal entry suggested altered coordination due to oral condition.

Conclusion: This study presents a hyoid-based classification framework for swallowing analysis. The approach, integrating 4D-CT with deep learning, provides higher structural and temporal resolution than conventional videofluoroscopy, yielding new insight into velopharyngeal timing and enhancing understanding of age-related and pathological swallowing variations, with potential applications in prosthodontics and oral rehabilitation.

Purpose: To determine the minimum radiation dose and imaging conditions required to visualize teeth and periodontal tissues in an adult dry skull using small field-of-view (FOV) dental cone-beam computed tomography (CBCT), and to explore dose reduction potential relative to national diagnostic reference levels (DRLs).

Methods: An adult dry skull phantom was imaged using a CBCT unit. Thirty-six imaging conditions were tested by combining three FOVs (4 × 4, 6 × 6, and 10 × 10 cm), four tube voltages (60-90 kV), and three tube currents (1, 3, and 5 mA). The radiation dose was quantified using the dose-area product (DAP). Three experienced evaluators rated diagnostic acceptability on a 5-point Likert scale across five criteria, including the visibility of the periodontal ligament space and lamina dura. An image was considered diagnostically acceptable when the total score across all evaluators was ≥85%.

Results: DAP values ranged from 19.4 to 1031.1 mGy·cm². Three imaging conditions achieved a diagnostic acceptability rate ≥85%: FOV 4 × 4 cm, 70 kV, 5 mA (DAP: 130.8 mGy·cm²); FOV 6 × 6 cm, 60 kV, 3 mA (DAP: 108.9 mGy·cm²); and FOV 6 × 6 cm, 90 kV, 3 mA (DAP: 274.2 mGy·cm²). When comparing the DAPs of these diagnostically acceptable conditions to the DRLs of Japan, Germany, and Estonia, a dose reduction ranging from 38 to 89% was achieved.

Conclusion: This study suggests the possibility of imaging with lower radiation doses compared to existing national DRLs while maintaining adequate image quality for evaluating adult teeth and periodontal structures.

Purpose: This study aimed to examine how positioning a simulated canine exhibiting infralabioversion affects the three-dimensional morphology of the upper lip, both at rest and during smiling.

Methods: This study included 20 adult female Japanese participants. Bilateral simulated canines with infralabioversion (experimental canines) were fabricated and attached to the labial surface between the maxillary lateral incisor and the canine. Three-dimensional facial soft tissue morphology was captured before and after applying the experimental canine, both at rest and during the three distinct smile types. Smiles were classified as small, medium, or large when the inferior margin of the upper lip was aligned with the cusp tip, widest buccolingual contour, and cervical portion of the experimental canine, respectively. The upper lip surface area and volume surrounding the experimental canine were measured. Differences in variables before and after experimental canine placement were evaluated statistically using a paired t-test. The average facial models before and after the procedure were superimposed to visualize shape differences.

Results: The upper lip surface area and volume around the experimental canine at rest and in small and medium smiles were significantly increased. In large smiles, the upper lip surface area and volume did not differ significantly before and after the addition of the experimental canine.

Conclusion: Placement of a simulated canine with infralabioversion altered the three-dimensional morphology of the upper lip at rest and during small and medium smiles.

This case report describes a patient with obstructive sleep apnea (OSA) who could not receive oral appliance therapy because of temporomandibular disorders and was instructed to perform tongue rotation exercises. The patient’s maximum tongue pressure, lip-seal strength, and subjective sleep quality improved post-intervention. Furthermore, apnea-hypopnea index and sleep architecture were improved after exercise compared with the baseline. These results suggest that tongue rotation exercises can improve not only oral function but also respiratory function during sleep and, thus, may be meaningful to introduce as an adjunctive therapy for OSA with impaired oral function or intolerance to conventional therapies.