The aim of this investigation is to assess effect of three different bleaching techniques on structural integrity, mineral density and volume of enamel via micro-computed tomography (micro-CT) and examine color changes by CIELAB and CIEDE2000 formulas. Twenty-four upper premolar teeth were randomly separated into three different groups (n = 8) (group 1, 35% hydrogen peroxide (HP) gel with Er,Cr:YSGG laser activation; group 2, 35% HP gel with diode laser activation; group 3, 35% HP gel with chemically activation). High-resolution micro-CT system (Bruker Skyscan 1275, Kontich, Belgium) was carried out to scan samples. Each tooth was scanned twice before-after application of bleaching with same scanning parameters. Structural thickness, structural separation, fragmentation index, mineral density, and mineral volume of enamel were calculated for each region of interest (ROI). Color changes were measured with spectrophotometer and calculated with CIELAB and CIEDE2000 formulas. Data analysis was made with one-way ANOVA with post-hoc LSD. Micro-CT analysis indicated that statistically significant differences were found in structural thickness, and separation, mineral density, and mineral volume of enamel for different ROIs before and after whitening for whole groups (P < .05). Significant differences were detected among inter-groups for these parameters in different ROIs (P < .05). There was no significant difference among groups for color alterations (P > .05). All bleaching applications exhibited similar efficiency on the enamel surface. Nevertheless, bleaching process with Er,Cr:YSGG laser had less negative effects on enamel as it showed less change in enamel compared to other bleaching treatments. Micro-CT analysis of histomorphometric parameters can be useful for further mineralization studies of dental hard tissues.

中文翻译：

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不同漂白处理后牙釉质结构的显微计算机断层扫描分析

本研究的目的是通过显微计算机断层扫描 (micro-CT) 评估三种不同漂白技术对釉质结构完整性、矿物质密度和体积的影响，并通过 CIELAB 和 CIEDE2000 公式检查颜色变化。将 24 颗上前磨牙随机分成三个不同的组 (n = 8)（第 1 组，35% 过氧化氢 (HP) 凝胶与 Er,Cr:YSGG 激光激活；第 2 组，35% HP 凝胶与二极管激光激活；第 3 组，具有化学活化的 35% HP 凝胶）。使用高分辨率显微 CT 系统（Bruker Skyscan 1275，Kontich，比利时）扫描样品。每颗牙齿在应用漂白前后扫描两次，扫描参数相同。结构厚度、结构分离度、破碎指数、矿物密度、计算每个感兴趣区域 (ROI) 的牙釉质和矿物质体积。使用分光光度计测量颜色变化并使用 CIELAB 和 CIEDE2000 公式计算。数据分析采用单向方差分析和事后 LSD。Micro-CT分析表明，全组美白前后不同ROI的釉质结构厚度、分离度、矿物质密度和矿物质体积均存在统计学差异。P  < .05）。在不同的 ROI 中，这些参数在组间之间检测到显着差异 ( P  < .05)。各组间颜色改变无显着差异（P  > .05）。所有漂白应用在搪瓷表面上表现出相似的效率。尽管如此，使用 Er,Cr:YSGG 激光的漂白过程对牙釉质的负面影响较小，因为与其他漂白处理相比，它对牙釉质的变化较小。组织形态学参数的显微 CT 分析可用于牙齿硬组织的进一步矿化研究。