Penetration Capacity, Color Alteration and Biological Response of Two In-office Bleaching Protocols

Abstract Hydrogen peroxide (H2O2) penetrates into the dental hard tissues causing color alteration but also alterations in pulpal tissues. Hard-tissue penetration, color alteration and the pulp response alterations were evaluated for two in-office bleaching protocols with H2O2. For trans-enamel/dentin penetration and color alteration, discs of bovine teeth were attached to an artificial pulp chamber and bleached according to the groups: BLU (20% H2O2 - 1x50 min, Whiteness HP Blue); MAX (35% H2O2 - 3x15 min, Whiteness HP Maxx); Control (1x50 min, placebo). Trans-enamel/dentin penetration was quantified based on the reaction of H2O2 with leucocrystal violet and the color analyzed by CIELab System. Twenty Wistar rats were divided into two groups (BLU and MAX) and their maxillary right molars were treated according to the same protocols of the in vitro study; the maxillary left molars were used as controls. After 2 days, the animals were killed and their maxillae were examined by light microscopy. The inflammation of pulp tissue was scored according to the inflammatory infiltrate (1, absent; 2, mild; 3, moderate; 4, severe/necrosis). Data were analyzed by statistical tests (α=0.05). MAX showed higher trans-enamel/dentinal penetration of H2O2 (p<0.05). The color alteration was similar for both groups (p>0.05), and different when compared to Control group (p<0.05). MAX showed severe inflammation in the upper thirds of the coronal pulp, and BLU showed moderate inflammation (p<0.05). In-office bleaching protocols using lower concentrations of hydrogen peroxide should be preferred due to their reduced trans-enamel/dentinal penetration since they cause less pulp damage and provide same bleaching efficiency.

摘要：过氧化氢（Hydrogen peroxide, H₂O₂）可渗透进入牙体硬组织（dental hard tissues），引发牙齿色泽改变，同时也会对牙髓组织（pulpal tissues）造成损害。本研究针对两种含过氧化氢的诊室美白方案（in-office bleaching protocols），评估了其硬组织渗透、色泽改变及牙髓组织反应情况。为检测釉质/牙本质渗透量与色泽改变，将牛牙（bovine teeth）圆盘固定于人工牙髓腔（artificial pulp chamber），按以下分组进行美白处理：BLU组（20%过氧化氢，单次50分钟，Whiteness HP Blue）、MAX组（35%过氧化氢，分3次给药，每次15分钟，Whiteness HP Maxx）及对照组（单次50分钟，安慰剂）。釉质/牙本质渗透量通过过氧化氢与亮甲酚蓝（leucocrystal violet）的反应进行定量，色泽则通过CIELab色彩系统（CIELab System）分析。将20只Wistar大鼠（Wistar rats）随机分为BLU组与MAX组，以上颌右侧磨牙（maxillary right molars）作为受试牙，按照体外实验相同的美白方案处理；上颌左侧磨牙作为空白对照。于处理后2天处死大鼠，取上颌骨进行光学显微镜（light microscopy）观察。根据炎性浸润（inflammatory infiltrate）程度对牙髓炎症进行评分：1分（无炎症）、2分（轻度炎症）、3分（中度炎症）、4分（重度炎症/坏死）。采用统计学检验（statistical tests）对数据进行分析，显著性水平设定为α=0.05。结果显示，MAX组的过氧化氢釉质/牙本质渗透量显著高于BLU组（p<0.05）。两组的牙齿色泽改变程度无显著差异（p>0.05），但均与对照组存在显著差异（p<0.05）。MAX组可见冠髓上部出现重度炎症，BLU组则为中度炎症（p<0.05）。综上，低浓度过氧化氢的诊室美白方案因釉质/牙本质渗透量更低，可减少牙髓损伤，且美白效率与高浓度方案相当，因此更值得推荐。