Dentin Bonding Durability of Four Different Recently Introduced Self-Etch Adhesives.

The objectives of this study were to evaluate the bonding durability of four different self-etch adhesives to dentin after 24 h and thermal cycling (TC) and to measure the degree of polymerization conversion (DC) in situ. Two-step self-etch adhesives, Clearfil SE Bond 2 (SE2, Kuraray Noritake Dental) and G2-Bond Universal (G2B, GC), and one-step self-etch adhesives, Scotchbond™ Universal Plus Adhesive (SBU, 3M ESPE) and Clearfil Universal Bond Quick (UBQ, Kuraray Noritake Dental), were used. The labial surfaces of bovine teeth were ground to create flat dentin surfaces. The adhesives were applied according to the manufacturers' instructions. After resin composite buildup and 24 h water storage, the specimens were sectioned into beams and all groups were subjected to thermal stress for 0, 10,000 (10k), or 20,000 (20k) cycles followed by micro-tensile bond strength (µTBS) testing. In situ DC was investigated with a laser Raman microscope. The µTBS data were statistically analyzed and subjected to a Weibull analysis. The different groups were compared at the characteristic strength (63.2% probability of failure) (α = 0.05). Two-Way ANOVA was used to show the effect of different adhesives and thermal cycling on the mean DC% followed by Tukey's multiple comparison post hoc test. G2B/TC10k resulted in a significant increase in the µTBS compared to TC0. SBU/TC20k showed significantly higher µTBS compared to TC0. For comparison between different tested adhesives, SBU showed a significantly lower µTBS compared to G2B after TC10k. G2B and SBU showed a greater number of adhesive failures after TC. Mean DC% was different for each adhesive. The newly developed MDP- and HEMA-free 2-SEA showed similar bonding performance with the gold-standard 2-SEA. However, there is still room for further improvement in terms of SEAs.

Questionnaire survey on hands-on simulation training using a dental humanoid robot (SIMROID®).

INTRODUCTION: A dental humanoid robot, SIMROID®, is able to replicate the actions characteristic of human beings and enable training for communicating with patients and coping with unexpected situations. This study assessed user experiences via a survey questionnaire following hands-on training on the SIMROID®. MATERIALS AND METHODS: A total of 112 participants, consisting of 50 high school students who visited AUSD (Asahi University School of Dentistry) to participate in open campus events, 42 fourth-year students at AUSD and 20 dental students from Mexico State Autonomy University, University of Siena and Peking University took the survey. The participants observed the movements and reactions of a SIMROID® robot placed on a dental unit for approximately 20 min after which they completed a questionnaire survey. Both Japanese and English versions of the questionnaire were prepared for local and visiting foreign dental students. The questionnaire comprised 8 items, with a further two items for those undertaking dental training and an open comment field. RESULTS: All participants who observed the SIMROID® completed the questionnaire giving a 100% response rate. Generally, simulation training with SIMROID® was highly appreciated by all participants. The comprehensive evaluation score for SIMROID® was 4.56 ± 0.50 points for high school students, 4.05 ± 0.82 points for students at AUSD and 4.70 ± 0.47 points for foreign dental students, showing all participants had a very positive experience and impression of the SIMROID®. CONCLUSIONS: Therefore, simulation training using SIMROID® seems beneficial learning tool.

Saccharification of ß-chitin from squid pen by a fermentation method using recombinant chitinase-secreting Escherichia coli.

Two strains [BL21(DE3) and HMS174(DE3)] of Escherichia coli harboring the recombinant chitinase expression plasmid pVP-Chi, which contains Vibrio parahaemolyticus chitinase gene with an attached signal sequence, were prepared. These E. coli transformants produced a large amount of recombinant chitinase, which hydrolyzes chitin to yield di-N-acetylchitobiose (GlcNAc)2, under the presence of isopropyl-1-thio-ß-D-galactopyranoside (IPTG), and secreted the enzyme into their culture fluid with the aid of the signal peptide. Cultivation of these E. coli transformants in Luria-Bertani medium containing squid pen ß-chitin and IPTG gave rise to the decomposition of this polysaccharide and the accumulation of (GlcNAc)2 in the culture fluid. Through these experiments, we confirmed that the use of strain HMS174(DE3) was preferable for the stable accumulation of (GlcNAc)2 in the culture fluid during cultivation owing to lower (GlcNAc)2 assimilation compared to BL21(DE3). Next, using E. coli HMS174(DE3) transformants, we conducted saccharification of different forms (fluffy fiber, flake, and powder) of ß-chitin samples prepared from squid pens in Bacterion-N-KS(B)K medium containing 2 % of each sample under the presence of IPTG. In these experiments, (GlcNAc)2 was isolated with a more than 20 % stoichiometric yield from each culture supernatant through charcoal column chromatography followed by recrystallization.