The haptic 3D virtual reality dental training simulator has been drawn attention as a educational strategy in Covid-19 pandemic. The purpose of this study is to investigate the feature of the haptics simulator in comparison with a conventional mannequin simulator by analyzing the assessment of products prepared by dental students using these two kinds of simulator. The subjects were 30 students in the sixth-year classes of the faculty of dentistry. Abutments for a full cast crown were prepared by each subject using two kinds of simulator; one is the haptics simulator and the other is a mannequin simulator. For the resulted products, occlusal surface form, margin design, surface smoothness, taper angle, total cut volume and overall impression were rated by 3 evaluators. Score differences between two simulators were statistically analyzed. The kinds of simulator affected subject performance for margin design and total cut volume. The differences in cutting feeling between the simulators as well as variation of stereoscopic ability in subjects were considerable reasons. Evaluators’ rating was affected by difference in simulators for occlusal surface form, total cut volume, and overall impression. This may have been due to variation of stereoscopic ability in evaluators. The unique characteristics of virtual reality, such as the simulated cutting sensation and the simulated three-dimensional images created by stereo viewers, affect operators’ performance and evaluators’ rating. It was suggested that educational programs need to be constructed taking account of the characteristics of virtual reality to make the best use of the haptics simulator.

Objective: The purpose of the present study was to investigate the tensile strengths of dentin after laser irradiation using three kinds of dental lasers to elucidate the laser-irradiation effect on dentin properties. Background data: Different kinds of laser devices have been developed in dentistry. The characteristics of each laser are determined by its original wavelength; however, one common feature is to generate heat in irradiated tissues, and such heat possibly affects dentin collagen, which contributes to tensile strength of the tissues. Materials and Methods: Er:YAG, CO2, and diode (GaAlAs) lasers were used to irradiate bovine dentin. Subsequently, tensile test specimens were made from the irradiated dentin and tensile tests were conducted. The tensile strengths were analyzed using the paired-t test and Weibull analysis. Irradiated dentin was also observed transversally using light microscopy. Results: The tensile strengths of the lased dentin and the control group for the Er:YAG, CO ₂ , and diode lasers were 73.1 and 78.5, 70.3 and 74.3, and 64.3 and 71.0 MPa, respectively. The tensile strength of the dentin had a tendency to decrease with laser irradiation. Weibull analysis indicated that the laser influence was different among the three kinds of laser apparatuses and seemed to correspond to the depths the laser beam reached, which were suggested by light microscopy observation. Conclusion: Laser irradiation could possibly decrease dentin tensile strength, which suggests the importance of careful use of laser for hard tissue treatment, considering its energy-transforming characteristics.

Incident reports are important for improving the quality and safety of medical care. Healthcare workers with less than one year of work experience have been reported to cause the most incidents, and the most common incident is “drug-related”. However, few studies have comprehensively analyzed incidents in dentistry, and the characteristics of dental incidents have not been understood. In this study, to understand the characteristics of dental incidents, we comprehensively analyzed 1291 incident reports submitted to the Tokyo Medical and Dental University Dental Hospital from April 2014 to March 2019. As a result, dental outpatient and dental wards had different types of incidents. In outpatient wards, incidents included many dentistry-specific incidents related to “procedures”. Among them, “poor physical condition of the patient during dental treatment” was the most common incident. In contrast, the most common incident from subjects with less than one year of work experience was “damage to soft tissues around the teeth”. Thus, to improve the quality and safety in dentistry, it is was considered necessary to analyze and understand the characteristics of dentistry-specific incidents and to take appropriate measures and educate dental professionals.

The purpose of this study was to describe the protein profile of pepsin-digested carious and sound dentine using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Carious and sound dentine powder was decalcified using 10% EDTA at pH 7.4 for 48 h. The decalcified pellet was digested using pepsin at pH 2 under sequenced conditions: at 4°C for 24 h, a further 24 h at 23°C, and finally for 24 h at 37°C. After every step, the soluble fraction was separated by centrifugation and analyzed in 15% SDS-PAGE. Two bands at 56 and 62 kDa could be observed in carious dentine digests and were considered specific carious bands. Similar bands could be observed in sound dentine samples, but only after pepsin digestion at higher temperatures (23°C and 37°C). Pepsin digests non-helical collagen and the triple helix structure of collagen is lost when the temperature rises. The bands at 56 and 62 kDa in sound dentine specimens thus represent pepsin-cleaved collagen. There is a possibility that the specific carious bands in carious dentine represent collagen decomposed in a manner similar to the way pepsin digests native dentine collagen at 23°C and 37°C.