Oral Health Cooperative Research Centre, Melbourne Dental School, Bio21 Institute, The University of Melbourne, Australia.
J Dent. 2013 Jul;41(7):611-8. doi: 10.1016/j.jdent.2013.05.002. Epub 2013 May 15.
To investigate and clarify physical and chemical properties of enamel affected by molar incisor hypomineralisation (MIH).
A series of in vitro studies were performed on extracted molars affected by MIH and sound teeth for controls. Tooth sections underwent Vickers microhardness testing before lapping and subsequent transverse microradiographic analysis and examination under polarised light microscopy. Carbonate content was determined by CO2 release from acid digestion. Unprepared and fractured surfaces were examined under scanning electron microscopy.
MIH-affected molars demonstrated a severe degree of hypomineralisation with an average mineral content of only 58.8%vol% mineral. Vickers microhardness was significantly reduced in MIH compared with controls (1.8±1.1 v 4.4±1.0 GPa, p<0.05) and polarised light microscopy revealed the bulk of MIH lesions had a porosity of ≤5% but also substantial areas of ≥10% and smaller areas exceeding 25% porosity. A surface layer was frequently observed on both intact and broken-down lesions and cervical regions of MIH teeth were typically spared. Carbonate content of MIH enamel was higher than control samples (6.6±2.1 v 4.4±1.1 wt%, p<0.05). Scanning electron microscopy showed that both the enamel rod and surface ultrastructure were defective. Clinical characteristics did not consistently correlate with all properties.
The properties of MIH-affected enamel significantly differ from those of normal enamel and were highly variable, however some common characteristics were observed. Implications for aetiology and clinical management are discussed.
研究并阐明受磨牙-切牙矿化不全（MIH）影响的釉质的理化性质。
对受 MIH 影响的磨牙和正常磨牙进行了一系列体外研究。牙齿切片在研磨前进行维氏显微硬度测试，随后进行横向显微放射分析和偏光显微镜检查。通过酸消化释放的 CO2 来确定碳酸盐含量。在扫描电子显微镜下观察未经处理和断裂的表面。
受 MIH 影响的磨牙表现出严重的矿化不全程度，平均矿化含量仅为 58.8%vol%矿化。与对照组相比，MIH 中的维氏显微硬度显著降低（1.8±1.1 比 4.4±1.0 GPa，p<0.05），偏光显微镜显示 MIH 病变的大部分具有≤5%的孔隙率，但也有相当大的区域≥10%和较小的区域超过 25%的孔隙率。在完整和破裂的病变以及 MIH 牙齿的颈部区域经常观察到表面层，而这些区域通常不受影响。MIH 牙釉质的碳酸盐含量高于对照组样本（6.6±2.1 比 4.4±1.1 wt%，p<0.05）。扫描电子显微镜显示，釉质棒和表面的超微结构均有缺陷。临床特征并不总是与所有特性一致相关。
受 MIH 影响的牙釉质的性质与正常牙釉质有显著差异，且高度可变，但观察到一些共同特征。讨论了病因学和临床管理的意义。
