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Abstract：
OBJECTIVE: To construct the three-dimensional structure of the isolated teeth of patients with dentinogenesis imperfecta type Ⅱ (DGI-Ⅱ) and dentin dysplasia type Ⅰ (DD-Ⅰ) by using Micro-CT and explore internal structure and hard tissue mineralization density.
METHODS: The three-dimensional structures of the third molars collected from patients with DGI-Ⅱ and DD-Ⅰ and healthy individuals of the same age were reconstructed by using Micro-CT (Mimics 17.0). The internal structures of the affected teeth along the sagittal and transverse planes were observed. The grayscale values of the enamel, crown dentin, and root dentin were calculated. Then, the mineralization densities of the different parts of the teeth of the three groups were analyzed.
RESULTS: The detailed three-dimensional models of the mandibular third molars with hereditary dentin defects were successfully constructed. The models contained the models of the enamel cap, dentin core, and pulp cavity. Sagittal and transverse section scans revealed that in patients with DGI-Ⅱ, the pulp cavity was incompletely calcified and the root canal was narrow, whereas in those with DD-Ⅰ, the pulp cavity and root canal were obliterated and the root of the tooth was absent. The analysis of the grayscale values showed that compared with those in the healthy group, the grayscale values of the enamel, crown dentin, and root dentin were lower in the DGI-Ⅱ and DD-Ⅰ groups (P<0.01). No significant differences in the grayscale values of the enamel and crown dentin were found between the DGI-Ⅱ and DD-Ⅰ groups (P>0.05), whereas the grayscale value of the root dentin showed statistically significant differences between the two groups (P<0.01).
CONCLUSIONS: The application of Micro-CT provided a simple and accurate method for the three-dimensional structure reconstruction and quantitative analysis of the mineralization density of isolated teeth with hereditary dentin defects. Although the dentin mineralization density of DGI-Ⅱ and DD-Ⅰ teeth decreased, the decrement shown by DD-Ⅰ teeth was more significant than that shown by DGI-Ⅱ teeth. The pulp cavity had abnormal calcifications, and the root canal was narrow or even occluded.
目的: 采用Micro-CT构建Ⅱ型牙本质发育不全（DGI-Ⅱ）和Ⅰ型牙本质发育不良（DD-Ⅰ）离体患牙的三维结构，研究该类患牙的内部结构及硬组织矿化密度的变化。方法: 收集同龄DGI-Ⅱ、DD-Ⅰ患者及健康者的第三磨牙，运用Micro-CT对3份样本逐一扫描并通过Mimics 17.0重建三维结构；截取矢状面和横断面观察患牙的内部结构；分别计算釉质、冠部牙本质以及根部牙本质的灰度值，分析牙齿不同部位的矿化密度。结果: 成功构建包括牙釉质帽、牙本质核和牙髓腔模型在内的DGI-Ⅱ、DD-Ⅰ患者的下颌第三磨牙三维精细模型；矢状面和横断面扫描显示DGI-Ⅱ患牙髓腔未完全钙化、根管狭窄，DD-Ⅰ患牙髓腔及根管闭锁、牙根缺如；灰度值分析发现DGI-Ⅱ、DD-Ⅰ患牙釉质、冠部牙本质及根部牙本质灰度值较正常对照组低（P<0.01）；DGI-Ⅱ、DD-Ⅰ两组相比，釉质、冠部牙本质灰度值差异无统计学意义（P>0.05），根部牙本质的灰度值差异有统计学意义（P<0.01）。结论: Micro-CT技术为遗传性牙本质发育缺陷离体患牙的三维结构重建及其矿化密度定量分析提供了简单而精确的方法。其中DGI-Ⅱ、DD-Ⅰ患牙的牙本质矿化密度均降低，DD-Ⅰ患牙降低更显著，髓腔内均有异常钙化物质，根管狭窄甚至闭塞。.
METHODS: The three-dimensional structures of the third molars collected from patients with DGI-Ⅱ and DD-Ⅰ and healthy individuals of the same age were reconstructed by using Micro-CT (Mimics 17.0). The internal structures of the affected teeth along the sagittal and transverse planes were observed. The grayscale values of the enamel, crown dentin, and root dentin were calculated. Then, the mineralization densities of the different parts of the teeth of the three groups were analyzed.
RESULTS: The detailed three-dimensional models of the mandibular third molars with hereditary dentin defects were successfully constructed. The models contained the models of the enamel cap, dentin core, and pulp cavity. Sagittal and transverse section scans revealed that in patients with DGI-Ⅱ, the pulp cavity was incompletely calcified and the root canal was narrow, whereas in those with DD-Ⅰ, the pulp cavity and root canal were obliterated and the root of the tooth was absent. The analysis of the grayscale values showed that compared with those in the healthy group, the grayscale values of the enamel, crown dentin, and root dentin were lower in the DGI-Ⅱ and DD-Ⅰ groups (P<0.01). No significant differences in the grayscale values of the enamel and crown dentin were found between the DGI-Ⅱ and DD-Ⅰ groups (P>0.05), whereas the grayscale value of the root dentin showed statistically significant differences between the two groups (P<0.01).
CONCLUSIONS: The application of Micro-CT provided a simple and accurate method for the three-dimensional structure reconstruction and quantitative analysis of the mineralization density of isolated teeth with hereditary dentin defects. Although the dentin mineralization density of DGI-Ⅱ and DD-Ⅰ teeth decreased, the decrement shown by DD-Ⅰ teeth was more significant than that shown by DGI-Ⅱ teeth. The pulp cavity had abnormal calcifications, and the root canal was narrow or even occluded.
目的: 采用Micro-CT构建Ⅱ型牙本质发育不全（DGI-Ⅱ）和Ⅰ型牙本质发育不良（DD-Ⅰ）离体患牙的三维结构，研究该类患牙的内部结构及硬组织矿化密度的变化。方法: 收集同龄DGI-Ⅱ、DD-Ⅰ患者及健康者的第三磨牙，运用Micro-CT对3份样本逐一扫描并通过Mimics 17.0重建三维结构；截取矢状面和横断面观察患牙的内部结构；分别计算釉质、冠部牙本质以及根部牙本质的灰度值，分析牙齿不同部位的矿化密度。结果: 成功构建包括牙釉质帽、牙本质核和牙髓腔模型在内的DGI-Ⅱ、DD-Ⅰ患者的下颌第三磨牙三维精细模型；矢状面和横断面扫描显示DGI-Ⅱ患牙髓腔未完全钙化、根管狭窄，DD-Ⅰ患牙髓腔及根管闭锁、牙根缺如；灰度值分析发现DGI-Ⅱ、DD-Ⅰ患牙釉质、冠部牙本质及根部牙本质灰度值较正常对照组低（P<0.01）；DGI-Ⅱ、DD-Ⅰ两组相比，釉质、冠部牙本质灰度值差异无统计学意义（P>0.05），根部牙本质的灰度值差异有统计学意义（P<0.01）。结论: Micro-CT技术为遗传性牙本质发育缺陷离体患牙的三维结构重建及其矿化密度定量分析提供了简单而精确的方法。其中DGI-Ⅱ、DD-Ⅰ患牙的牙本质矿化密度均降低，DD-Ⅰ患牙降低更显著，髓腔内均有异常钙化物质，根管狭窄甚至闭塞。.
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