| Objective: The aim of this study was to observe the morphological characteristics of enamel in pit and fissure of primary molars etched by Er:YAG laser with different power under scanning electron microscope(SEM) and select the appropriate laser power for clinical application. The sealant retention by laser etching was investigated and the patients' satisfaction was evaluated. This study provided basic and clinical data for the application of Er:YAG laser in children.Methods:1 Morphological characteristics of enamel in pit and fissure of primary molars etched by Er:YAG laserTwelve extracted primary molars without caries and restoration were collected and divided into 6 groups randomly. There were two primary molars in each group. The preparation of teeth in each group was as following: 1. the blank control group(untreated primary teeth), 2. phosphoric acid etching group(treated by 35% phosphoric acid), 3. laser ? group(treated by Er:YAG laser etching with parameter 100mJ/10HZ/100%water/20s), 4. laser ? group(treated by Er:YAG laser etching with parameter 200mJ/10HZ/100% water/20s), 5. laser ? group(treated by Er:YAG laser etching with parameter 300mJ/10HZ/100%water/20s), 6. laser ? group(treated by Er:YAG laser etching with parameter 400mJ/10HZ/100%water/20s). After preparation, the samples were observed under SEM.2 Pit and fissure sealants of primary molarsThere were 37 children of 3-6 years old who had at least two healthy same name teeth selected. The self control design was used in this study. One side primary teeth were prepared by 35% phosphoric acid etching and the other sides were etched by Er:YAG laser with parameter 300mJ/10HZ/100%water/20 s. The teeth were followed up in 3, 6, 12 months after the operation and the retention of sealants was investigated respectively.3 The evaluation of patients' satisfactionThe patients' satisfaction about laser etching and acid etching was investigated by Wong-Baker facial pain scale after the pit and fissure sealant immediately.Results:1 Morphological characteristics: The enamel surface of untreated primary teeth was smooth and flat. The enamel surface in phosphoric acid etching group was clean, no smear layer and uniform honeycomb structure, at the bottom of which there were many small structures like burr. A clean rough surface with irregular fissure and no smear layer was shown in all Er:YAG laser etching groups. It was shown that pits on the enamel surface were non-uniform and the sizes were significantly different in laser ? group. Pits on the enamel surface in laser ? group were larger than that of laser ? group and were non-uniform. Pits on the enamel surface in laser ? group were uniform honeycomb structures larger than that of laser ? group and the bottom of honeycomb structure was rough. There was melting on the enamel surface in laser ? group.2 The comparison of sealant retention in primary teeth: After 3 months of the operation, the full sealant retention rate was 91.21% in laser etching group and 96.55% in acid etching group respectively, and there was no statistically significant difference in the two groups(P=0.139). After 6 months, the full sealant retention rate was 86.21% in laser etching group and 86.75% in acid etching group, and there was no statistically significant difference in the two groups(P=0.918). After 12 months, the full sealant retention rate was 80.77% in laser etching group and 78.95% in acid etching group, and there was no statistically significant difference in the two groups(P=0.778).3 The result of patients' satisfaction: The patients' satisfaction was investigated immediately after the pit and fissure sealant. There were 30 children restored among 37 children. Fifty-three percent of the children considered that laser etching was more comfortable. Twenty percent of the children considered that there was no difference in the two etching methods. The Er:YAG laser etching was more comfortable than acid etching significantly(P=0.035).Conclusions:1 The parameter of laser etching the enamel surface of primary molar which was similar to acid etching was 300mJ/10HZ/100%water/20 s.2 There was no statistically significant difference in the sealant retention rate between laser etching group and acid etching group in 3, 6, 12 months.3 Er:YAG laser etching was considered more comfortable compared with acid etching in children. |
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