PHYSICOCHEMICAL CHANGE OF TOOTH STRUCTURE AND CLINICAL PROBLEMS IN DENTAL ESTHETIC BLEACHING

用含6%过氧化钠和可见光光催化剂二氧化钛的漂白剂对牙釉质或牙本质进行漂白，漂白后立即或1天后，用Clearfil MEGA Bond粘结剂粘结一个直径为0.79mm，高1 mm的复合树脂（Clearfil AP-X，A3）圆柱体。30天后，在通用测试机（EZ测试）中进行微剪切粘结强度测试。漂白后即刻或1天，用同样的粘接剂系统，将相同的复合树脂圆柱体（φ3.18mm，高3 mm）粘接在两个表面上。将这些样本浸入0.5%碱性品红中。在染料渗透中进行边缘泄漏试验。结果表明：1.牙釉质微剪切强度分别为48.38±13.93MPa（对照组）、54.72 ±15.21MPa（漂白后1d）和37.55±12.92MPa（漂白后即刻），漂白后保存1d后恢复; 2.牙本质微剪切强度分别为44.16±13.13MPa（对照组）、44.16 ±9.55MPa（漂白后1d）和35.71±12.21MPa（漂白后即刻），漂白后保存1d后恢复; 4.漂白后放置1d并不影响染料的渗透性。5.漂白后的边缘问题会引起许多临床问题，因此边缘渗漏试验的结果对临床有重要意义。

Enamel or dentin was bleached by the bleaching agent containing 6% sodium peroxide and titanium dioxide that is visible-light-responsive photocatalyst.Immediately or 1 day after bleaching the adhesive system (Clearfil MEGA Bond) was applied and a cylinder(φ0.79mm, height 1mm) of composite resin (Clearfil AP-X, A3) was bonded on each surface. After 30 days the micro-shear bond strength test was performed in a universal-testing machine (EZ test). Specimens without bleaching procedure were prepared as controls.Immediately or 1 day after bleaching the same adhesive system was applied and cylinder (φ3.18mm, height 3mm) of the same composite resin was bonded on each surface. These specimens were immersed in 0.5% basic fuchsine. The marginal leakage test was performed in a dye penetration. Specimens without bleaching procedure were prepared as controls.The results were followed :1.The enamel micro-shear bond strengths were 48.38±13.93MPa(control),54.72±15.21MPa(1day after bleaching) and 37.55±12.92MPa (immediately after bleaching), and retuned after 1 day of storage after bleaching.2.The dentin micro-shear bond strengths were 44.16±13.13MPa (control),44.16±9.55MPa (1day after bleaching) and 35.71±12.21MPa (immediately after bleaching), and retuned after 1 day of storage after bleaching.3.The marginal leakage test showed the frequency of dye penetration increased in the order of immediately after bleaching, 1day after bleaching and control. This order was clear in enamel surface.4.1 day of storage after bleaching might not decrease the dye penetration.5.Marginal troubles of restorations cause many clinical problems, so the result of marginal leakage test is important for clinic.