不同酸蚀时间处理后年轻及成年恒牙釉质表面微观形貌及性质变化的观察研究

目的:探讨酸蚀时间对年轻及成年恒牙釉质表面性质结构的影响?方法:收集因正畸需要而拔除的新鲜前磨牙90颗,其中年轻恒牙(患者年龄为12~17岁)45颗,成年恒牙(患者年龄≥18岁)45颗?扫描电镜下观察不同酸蚀时间处理后年轻恒牙与成年恒牙釉质表面微观形貌的差异,分析釉质表层元素含量?显微硬度?托槽抗剪切强度?残留粘结剂指数(ARI)等性质的变化?结果:镜下形貌观察显示,年轻恒牙酸蚀15 s后柱间质已开始出现溶解,酸蚀30 s后釉柱宽度及高度均有降低,随着酸蚀时间的增加,釉柱间质溶解不断增多,釉柱正常结构逐渐被酸蚀破坏,酸蚀60 s后釉质表面正常结构几乎消失;成年恒牙酸蚀30 s后柱间质溶解逐渐明显,随酸蚀时间的延长,釉质表面形貌特点无明显差异?经检测,成年恒牙釉质表面的显微硬度值明显大于年轻恒牙?不同酸蚀时间处理后,年轻及成年恒牙托槽粘结后抗剪切强度均无显著差异,年轻恒牙钙磷含量和Ca/P比值无统计学差异,成年恒牙酸蚀60 s后釉质表层磷含量明显< 45 s组,Ca/P比值< 30 s?45 s组?结论:为了减少酸蚀对釉质表面的损害,年轻恒牙正畸临床酸蚀处理时间可适当减少至15 s,成年恒牙可延长至30 s?

Characterization of the surface microtopography and properties of immature permanent and permanent dental enamel after variable etch times

Objective:To investigate the effect of variable etch times on the surface structure characterization of immature permanent and permanent teeth. Methods:We collected 90 premolars extracted for orthodontic need,in which immature permanent teeth (patients aged 12 to 17) were 45 and permanent teeth (patients aged 18 or higher) were 45. The differences of enamel surface microtopography between immature permanent and permanent teeth after variable etch times were observed under scanning electron microscope (SEM),and the changes of enamel surface element content,microhardness,shear bond strength,and index of ARI,etc. were analysed. Results:SEM showed that the interprismatic substance of immature permanent teeth has started to dissolve after 15 s. The width and height of prism both decreased after 30 s. With the increase of etch time,substance dissolved gradually and normal structure of enamel prism was destroyed by acid step by step. After 60 s, normal structure of the enamel surface almost disappeared. The interprismatic substance of permanent teeth dissolved obviously after 30 s. No significant difference of the enamel surface morphology was observed with the time increased. The value of surface microhardness of permanent teeth was significantly greater than that of immature permanent teeth. After variable etch times,the shear bond strength of immature permanent and permanent teeth was of no significant difference. The calcium and phosphorus content and Ca/P ratio of immature permanent teeth showed no statistical difference,however,after 60 s the phosphorus content of permanent teeth was much smaller than that of the 45 s group,Ca/P ratio of the 60 s group was less than that of the 30 s and 45 s groups. Conclusion:In order to reduce the etched damage to the enamel surface,etch time of immature permanent teeth in the orthodontic clinic can be appropriately reduced to 15 s,and permanent teeth can be extended to 30 s.