Study on Restorative and Preventive Methods of Root Surface Caries in vitro.

本研究探讨了评价牙本质粘接剂、改善牙缘闭合、预防牙根龋的最佳方法。实验结果如下：1。研制了一台精度高、重复性好、耐用的粘接疲劳试验机。用该仪器对四种牙本质粘接剂进行了评价。3个品牌的静剪切粘接强度相似，但动疲劳剪切粘接强度差异显著，Liner bond <@D1(]SY.encircledR。[)@>D1的静剪切粘结强度最高，无疲劳下降。为了提高光固化树脂复合修复体的边缘闭合性，对三组分倾斜增量技术进行了评价。采用增量法，延长浸水时间，树脂复合材料的边缘封闭性较好。为了防止铸造修复后的继发性龋病，在固牙前对牙本质腔壁进行apf -镧处理。apf -镧处理（APF-La Tx）是一种有效的预处理牙腔，以防止酸渗透和保护牙本质结构。为了表明APF-La Tx在牙本质表面抗脱矿的有效性，我们进行了扫描电镜研究。在脱矿前，APF-La处理过的牙本质表面被0.5-1.0 μ m厚的微小球形化合物完全覆盖，脱矿后这些化合物仍然存在并覆盖在牙本质表面。牙本质小管用牙本质塞封闭。APF- la Tx组病变形成较对照组和APF组浅。APF-La Tx表现出色，具有良好的表面结构，可抵抗随后的酸侵蚀。

In this study the most appropriate methods for evaluating the dentin adhesive agent, improving the marginal closure, and preventing root caries were examined.The results obtained were as follows :1. An accurate, reproducible, and durable adhesive fatigue testing machine was constructed. Four brands of dentine adhesives were evaluated using this machine. The static shear bond strengths of three brands were similar, but the dynamic fatigue shear bond strengths were significantly different from each other, and Liner Bond<@D1(]SY.encircledR.[)@>D1 showed the highest static shear bond strength with no fatigue decline.2. To improve the marginal closure of light-curing resin composite restoration, the three components inclined incremental technique was evaluated. Better marginal closure of resin composite was obtained when the incremental technique was used and the water immersion period was extended.3. To prevent the secondary caries of cast restoration, the APF-lanthanum treatment was applied onto the dentinal cavity walls before cementation. The APF-lanthanum treatment (APF-La Tx) is effective as a pretreatment of the cavity to prevent acid penetration and to preserve the dentin structure.4. To indicate the effectiveness of APF-La Tx onto the dentin surface against demineralization in vitro, a scanning electron microscopic study was performed. Before demineralization, APF-La treated dentin surface was completely covered with a 0.5-1.0 mum thick layer of minute spherical compounds, and these compounds still remained and covered the surface even after demineralization. Dentinal tubules were closed by dentinal plugs. APF-La Tx group showed a shallower lesion formation than the control and APF groups. The APF-La Tx was outstanding with a well preserved surface structure resistant against subsequent acid attack.