This study aimed to compare the insertion torque (IT), resonance frequency (RF), and removal torque (RT) among three microimplant brands. Thirty microimplants of the three brands were used as follows: Type A (titanium alloy, 1.5-mm × 8-mm), Type B (stainless steel, 1.5-mm × 8-mm), and Type C (titanium alloy, 1.5-mm × 9-mm). A synthetic bone with a 2-mm cortical bone and bone marrow was used. Each microimplant was inserted into the synthetic bone, without predrilling, to a 7 mm depth. The IT, RF, and RT were measured in both vertical and horizontal directions. One-way analysis of variance and Spearman's rank correlation coefficient tests were used for intergroup and intragroup comparisons, respectively. In the vertical test, the ITs of Type C (7.8 Ncm) and Type B (7.5 Ncm) were significantly higher than that of Type A (4.4 Ncm). The RFs of Type C (11.5 kHz) and Type A (10.2 kHz) were significantly higher than that of Type B (7.5 kHz). Type C (7.4 Ncm) and Type B (7.3 Ncm) had significantly higher RTs than did Type A (4.1 Ncm). In the horizontal test, both the ITs and RTs were significantly higher for Type C, compared with Type A. No significant differences were found among the groups, and the study hypothesis was accepted. Type A had the lowest inner/outer diameter ratio and widest apical facing angle, engendering the lowest IT and highest RF values. However, no significant correlations in the IT, RF, and RT were observed among the three groups.
This study aimed to evaluate the bond characteristics of 6-MHPA monomer-based primer in a temporary tooth coating material set (BeautiCoat, Shofu, Kyoto, Japan), applied to various conditioned enamels. The buccal enamel of thirty premolars was ground flat and the teeth were divided into six groups. This research bleached two groups, acid-etched two groups, and did not condition the remaining two groups. BeautiCoat primer was applied alone, or with activator on the ground and bleached enamel. BeautiCoat primer and FLBond were applied on the acid-etched enamel. FL-Bond adhesive on acid-etched enamel served as the control. BeautiCoat flowable resin was then piled on the enamel surfaces and light-cured. The microtensile bond strength (μTBS) was measured and the superficial demineralization, the resin-enamel interface, and failure mode were evaluated with a scanning electron microscope. The μTBS obtained in the non-acid-etched groups was more than half of that obtained in the acid-etched groups (p < 0.05). FL-Bond adhesive on acid-etched enamel showed the highest μTBS values. Marked improvements in μTBS were not observed when activator was combined with primer. No significant difference in μTBS could be found between BeautiCoat primer and FL-Bond adhesive on acid-etched enamel, or among BeautiCoat primer applied with/without activator on the ground and bleached enamel. The cohesive enamel failure ratio was low with the BeautiCoat primer or in the primer and activator groups but high in the FL-Bond group. The adhesive of BeautiCoat provided favorable bond strength with minimal risk of damage to the enamel.
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