光固化复合树脂在MO洞型中聚合收缩的体外实验研究

目的利用电子散斑干涉技术测试临床中常用的5种光固化复合树脂的聚合收缩。方法取15颗新鲜拔除且牙体组织完整、大小相似的下颌第三磨牙，制备MO洞，洞宽为颊舌牙尖距的1／3，洞深为2mm，然后采用GRADIADIRECT—P、Z350、Z250、P60和P90树脂随机充填窝洞（除P90采用其自带的粘接剂，其余都采用G-BOND粘接剂处理洞壁），在650mW／cm^2光源下，光照固化40S后采用电子散斑干涉技术对树脂修复体验面、近中邻面收缩和牙齿颊面的变形进行测量分析。结果树脂收缩形态与窝洞外形一致，验面最早的收缩条纹出现在MO洞鸠尾的头部，然后沿着窝洞的方向扩展。近中邻面最早的收缩条纹发生在靠近粘结面处，并向中央扩展。五种树脂中GRADIADIRECT—P的收缩量最大，P90的收缩量最小。牙齿的颊面条纹首先出现在近中颊尖的牙尖处，并向远中颊尖扩展。GRADIADIRECT—P导致的近中颊尖变形量最大，而P90最小。结论电子散斑干涉技术能有效动态测量树脂修复体聚合收缩和牙齿变形。不同种类的光固化复合树脂，其固化收缩状况和导致的牙齿变形存在着差异。

An in vitro investigation of composite polymerization shrinkage in MO cavities

Objective To evaluate the polymerization shrinkage of 5 commercially available dental resin composites using the electronic speckle pattern interferometry （ESPI）. Methods Fifteen freshly extracted human mandibular third molars were collected and MO cavities with width of 1/3 of buccolingual cusp distance and depth of 2 mm were prepared in the occlusal surface. Cavities were treated with G-BOND bonding system except for P90 with its own bonding system; then filled with GRADIA DIRECT-P, Z350, Z250, P60 or P90 respectively, the curing shrinkages of the 5 compositeswere measured by the ESPI immediately after light cured for 40 s under the 650 mw/cm^2. Results The shrinkage of the tested composites was fit the shape of the cavities. In the occlusal part, contraction occurred in the head of dovetail firstly and spread along the cavity. In the proximal part, contraction occurred near the bonding interface and spread to the central. Among 5 tested resin composites, GRADIA DIRECT-P showed the largest polymerization shrinkage and P90 showed the minimal. Tooth structure deformation occurred firstly in the adjacent tooth cusp. GRADIA DIRECT-P caused the biggest deformation of the tooth structure, while P90 caused smallest, Conclusion The ESPI can effectively measure polymerization shrinkage of dental resin composites. Different resin composites show difference in polymerization shrinkage and tooth deformation induced.