AIM: To observe the color changes of cervical and body part of teeth after bleaching. METH-ODS: Thirty-six freshly extracted teeth were bucco-lingually sectioned at the middle and randomly assigned to three groups: 380 mL/L HP 45 min/day×1 +150 g/L CP 8 h/day × 4 (group A); in-office bleaching group (group O) : 380 mL/L HP 45 min/day×2; at home bleaching group ( group H):150 g/L CP 8 h/day×14. The △E values of the body part,cervical part of buccal surface, and dentin near the boundary were analyzed by the Crystaleye spectrophotom-eter before and after bleaching. RESULTS: After three regimes of bleaching, the colors of the cervical and the body part of teeth and dentin on the opposite surface became lighter( P < 0.05). The colors of the body part of teeth were significantly lighter than those of the cervical part (P <0. 05). However, no significant difference was observed between cervical and body dentin color changes ( P > 0.05 ). The color changes of the cervical and the body part of tooth surfaces and the dentin color did not show significant difference (P > 0.05 ). CONCLUSION: The thickness of enamel has no influence on the color changes of dentin by bleaching agent. Dentin color change has no influence on tooth color changes. Enamal thickness may influence the color change of the teeth.%目的:探讨漂白后牙齿体部与颈部颜色变化不同的原因.方法:将36个新鲜拔除的人前磨牙沿唇(颊)舌方向中央剖开、去髓,随机分成3组,联合漂白组(A):380 mL/L过氧化氢(HP)45 min/d×1次+150 g/L过氧化脲(CP)8 h/d ×4次；诊室漂白组(O):380 mL/L过氧化氢(HP) 45 min/d×2次；家庭漂白组(H):150 g/L过氧化脲(CP)8 h/d×14次.3组分别于漂白前、后用Crystaleye电脑比色仪测量牙齿唇(颊)面靠近剖面中线区体部、颈部及相对应剖面靠近釉牙本质界牙本质漂白前后的△E值.结果:3种漂白方案疗程结束后,体部、颈部牙齿颜色及与其对应的剖面牙本质均出现了颜色变浅(P＜0.05),但体部牙齿颜色改变程度超过颈部(P＜0.05).体部、颈部牙本质颜色改变无显著性差异(P＞0.05)；体部、颈部牙齿表面与其分别对应的剖面牙本质颜色改变无显著性差异(P＞0.05).结论:漂白剂对牙本质的颜色改变不受釉质厚度的影响.牙本质颜色变化和漂白后体部、颈部牙齿表面颜色变化不相关.牙齿体部颜色改变慢于颈部可能是体部釉质厚度大于颈部及半透明性改变产生的.
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