Abstract：
OBJECTIVE: Molar incisor malformation (MIM) is a dental anomaly rendering first permanent molar pulps inflamed/necrotic at a young age. It often affects permanent incisors, primary second molars and less frequently other teeth. The purpose of this study was to investigate the anatomy and histology of MIM in seeking insight into its pathogenesis.
METHODS: Five MIM first permanent molars were examined with micro-computed tomography (micro-CT) for 3D morphology, with scanning electron microscopy for microanatomy, with energy-dispersive X-ray spectrometer (EDS) for chemical composition and for histology with optical microscopy. Composition differences were statistically determined using one-way ANOVA.
RESULTS: Micro-CT confirmed dentin abnormalities in the middle and cervical third of the crown in the form of the radiodense \'cervical mineralized diaphragm\' (CMD). This was peripherally intertwined with enamel fjords and projections severely disrupting the integrity of pulp chamber and its continuity with root canals. EDS showed increased Ca in CMD compared to dentin. The histological examination revealed anomalous osteodentin-like hard tissue with denticles in the CMD.
CONCLUSIONS: An interconnection of anomalous cervical enamel with crown CMD dentin preceded to the severe pulp chamber and root dysplasias in MIM molar teeth.
METHODS: Five MIM first permanent molars were examined with micro-computed tomography (micro-CT) for 3D morphology, with scanning electron microscopy for microanatomy, with energy-dispersive X-ray spectrometer (EDS) for chemical composition and for histology with optical microscopy. Composition differences were statistically determined using one-way ANOVA.
RESULTS: Micro-CT confirmed dentin abnormalities in the middle and cervical third of the crown in the form of the radiodense \'cervical mineralized diaphragm\' (CMD). This was peripherally intertwined with enamel fjords and projections severely disrupting the integrity of pulp chamber and its continuity with root canals. EDS showed increased Ca in CMD compared to dentin. The histological examination revealed anomalous osteodentin-like hard tissue with denticles in the CMD.
CONCLUSIONS: An interconnection of anomalous cervical enamel with crown CMD dentin preceded to the severe pulp chamber and root dysplasias in MIM molar teeth.
摘要：
目的：磨牙切牙畸形（MIM）是一种牙齿异常，使第一恒磨牙牙髓在年轻时发炎/坏死。它经常影响永久门牙，初级第二磨牙和其他牙齿较少。目的探讨MIM的解剖学和组织学特点，以寻求对其发病机制的认识。
方法：用显微计算机断层扫描（micro-CT）检查五个MIM第一恒磨牙的3D形态，用扫描电子显微镜进行显微解剖，使用能量色散X射线光谱仪（EDS）进行化学成分和光学显微镜进行组织学检查。使用单向ANOVA统计学确定组成差异。
结果：Micro-CT证实牙冠中部和颈部三分之一的牙本质异常呈放射性致密\'宫颈矿化膈\'（CMD）的形式。这与牙釉质峡湾和突起交织在一起，严重破坏了牙髓腔的完整性及其与根管的连续性。与牙本质相比，EDS显示CMD中的Ca增加。组织学检查显示CMD中有异常的骨沉蛋白样硬组织，有齿。
结论：在MIM磨牙中，异常的宫颈釉质与牙冠CMD牙本质的相互联系在严重的牙髓腔和牙根发育不良之前。
方法：用显微计算机断层扫描（micro-CT）检查五个MIM第一恒磨牙的3D形态，用扫描电子显微镜进行显微解剖，使用能量色散X射线光谱仪（EDS）进行化学成分和光学显微镜进行组织学检查。使用单向ANOVA统计学确定组成差异。
结果：Micro-CT证实牙冠中部和颈部三分之一的牙本质异常呈放射性致密\'宫颈矿化膈\'（CMD）的形式。这与牙釉质峡湾和突起交织在一起，严重破坏了牙髓腔的完整性及其与根管的连续性。与牙本质相比，EDS显示CMD中的Ca增加。组织学检查显示CMD中有异常的骨沉蛋白样硬组织，有齿。
结论：在MIM磨牙中，异常的宫颈釉质与牙冠CMD牙本质的相互联系在严重的牙髓腔和牙根发育不良之前。
