Temporomandibular disorders (TMDs) are a multifactorial joint disease of the masticatory system. The possible etiological factors involved in the onset and progression of TMDs include oral parafunctional habits (OPFHs) and postural habits (PHs). However, little information is available on the association between OPFHs and PHs and a predisposition to TMDs. Thus, to investigate whether the presence of OPFH and PH predisposes individuals to TMDs, a survey-based cross-sectional cohort study of self-reported TMD was performed. A total of 2292 patients with TMD were recruited for the survey. Through one-to-one propensity score matching, 166 patients with and without sleep bruxism (SB) were selected. The SB group had a significantly higher risk of masticatory muscular pain or fatigue than the non-SB group (p = 0.018). Furthermore, the SB group without other OFPHs and PHs did not show a significantly higher risk of TMD symptoms than the non-SB group. Diurnal clenching and bad posture also affect the stomatognathic system, causing pain or fatigue; however, it did not result in TMDs in patients without any OPFHs and PHs. This implies that OPFHs and PHs may increase the risk of TMD symptoms in coexistence with other habits.

The purpose of this study is to investigate the precision and trueness of the occlusal contact record obtained with a dental CAD/ CAM device (ARCTICA). Sandblasted spherical steel balls with diameters of 10-20 mm were measured using ARCTICA and a three-dimensional measurement device (FN503). The radius of each steel ball was calculated from the measured value and the difference between the measured and nominal values was obtained. Upper/lower dental arch casts were measured and processed for occlusal contact image creation using both devices. The graphical images of the occlusal contacts at the intercuspal position obtained from both systems and an occlusal analysis device (BE-1) were compared with the occlusal contact area. Excellent correlation was observed between the measurement results of ARCTICA and FN503 (p<0.001, R 2 : 0.99). The occlusal contact areas were 186.0 mm 2 (ARCTICA), 192.8 mm 2 (FN503), and 196.1 mm 2 (BE-1). This study showed that ARCTICA is capable of conducting highly accurate measurements and generating a graphical image of occlusal contacts with good reliability.

IntroductionThis study aimed to evaluate and validate the educational effectiveness of a job shadowing class as a dental teaching programme for preclinical dental students through a questionnaire that assessed related student perceptions.Materials and MethodsA total of 124 preclinical (second year) dental students at Tokushima University participated in job shadowing placements from 2017 to 2019. Each student observed dental practice or surgery for 1 day in the university hospital. After shadowing, the students were requested to fill out a nine‐item questionnaire based on a five‐point scale. The first analysis was performed to calculate the correlation for each item. Furthermore, regression analysis for the categorical data was performed to show the relationship between eight questions (Items 1–8) and one question (Item 9: comprehensive evaluation). Next, factor analysis was performed to determine students' perceptions regarding the shadowing class.ResultsNinety‐eight students (response rate: 79%) completed the questionnaire. There was a strong relationship amongst Items 1, 8 and 9 (“interested in dentistry as a job,” “learning motivation” and “comprehensive evaluation” respectively) based on the results of the correlation and regression analysis. The factor analysis led to three student perceptions as latent factors, namely, “Interesting,” “Self‐awareness” and “Future Goal,” which had a relatively close inter‐factor correlation (0.465–0.772).ConclusionThe finding suggests that job shadowing may increase a students' interest in a dentistry career at an early stage of their education and learning motivation, along with generating self‐awareness. This programme may present possible educational effectiveness in dental education.

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CAD/CAM resin composite crowns are inexpensive tooth-colored prostheses that have been widely used. However, bonding between CAD/CAM resin composites and resin cements could be difficult since the resin composite is highly cross-linked. There is limited existing data on the resin cements’ bond strength with different monomers to CAD/CAM resin composites. In this study, CAD/CAM resin composite was bonded to an SUS rod with three different resin cements following treatment of the bonding surface using the manufacturer's recommended primer. After storing the specimens in water at 37 °C for 24 h, half of them were tested immediately and half were thermocycled for 10,000 cycles in water for a dwell time of 20 s at 5 and 55 °C. The means of the tensile bond strength and standard deviations were determined for each resin cement and testing condition. The data were compared using two-way ANOVA and Bonferroni's multiple comparison tests at 95% confidence level.