| According to the traditional endodontical therapy, pain was something unavoidable. Therefore, patients had to suffer a lot during the treatment. As the modern stomatological developments, "painless dental therapy" has become available, and it has shown great potential to achieve ideal result causing patients no pain. Cavity preparation technique without cut is one of the novel methods. Since its introduction into clinic, more and more patients have accepted it. However, it still remains controversial. In this study, SEM and micro-tensile bond strength examination were used to investigate such problems. The following experiments were carried out: 1. Morphological study on tooth surface change after air-abrasion Freshly extracted normal molars from orthodontic patients were gathered and cleaned after disposing of the soft tissue. Samples in Group 1 were prepared by air-abrasion after surface treatment on enamel and dentin. Samples in Group 2 were untreated as control. Surface of enamel was observed by naked eyes: enamel surface was quite. SEM results (+1.0k) showed enamel surface after air-abrasion was coarse,with peak-like ridges, and thin smear layer could be observed, while no integrated enamel columns were observed. SEM results (+500) showed dentin surface after air-abrasion was also coarse, with dene-like ridges, and thin smear layer could be observed. There were openings of dentin tubules observed vaguely, but no crackswhatsoever.2. Study on the impacts of different acid etching duration on the enamel surfaceFreshly extracted molars with Class 1 medium cavities localized in enamel from periodontal patients were gathered and cleaned after disposing of the soft tissue. Class 1 cavities were prepared by means of air-abrasion in enamel layer, 10ml/l pinkish red solution was used to evaluate whether caries was abraded. The enamel surface was etched by 37% phosphate acid for different length of time: 0 second for control, 15, 30, and 45 seconds for Groups 2, 3 and 4 respectively. Clean water was applied to wash the surfaces for 20 seconds. And the enamel surfaces were observed by naked eyes: cavities in all of the four groups showed chalky appearance, with irregular contour and rough parietal and bottom walls, soft caries having been wiped off completely. SEM (+1.0k) was carried out, and it showed that samples in Group 1 showed idiosyncratic enamel column structures on the rough surface, which were covered by white cloudy thin smear layer. Samples in Group 2 showed the rough surface became clearer, and part of the idiosyncratic enamel column structures could be seen, while the smear layer was not wiped off completely. Samples in Group 3 presented an obviously rough surfaceand scale-like enamel column structures; the smear layer was wiped off completely. Samples in Group 4 showed that the enamel column structures were destroyed.From the experiments, it could conclude that acid etching for 30s after air abrasionmight result in a better adhesive effect. In this group, the smear layer was wiped off; tooth surface became rough, while the enamel column structures remained.3. Study on the impacts of different acid duration on the dentin surfaceFreshly extracted molars with Class 1 medium cavities that affected dentin from periodontal patients were gathered and cleaned after disposing of the soft tissue. Class 1 cavities were prepared by means of air-abrasion in dentin, 10ml/l pinkish red solution was used to evaluate whether caries was abraded. Dentin surface was etched by 37% phosphate acid for different length of time: 0 second for control, 15, and 30 seconds for Groups 2, and 3 Respectively. Clean water was applied to wash the surface for 30 seconds. SEM (+1.0k) was carried out, it showed that samples in Group 1 had rough surface, which was covered by a thin smear layer, only small number of openings of dentin tubules with no embolism inside could be observed. Samples in Group 2 showed the surface was rough, while a small part of the smear layer remained, and most of the openings of de... |
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