Department of Bioscience Research, College of Dentistry, University of Tennessee Health Science Center, Memphis, TN, USA.
Dent Mater. 2011 Feb;27(2):126-33. doi: 10.1016/j.dental.2010.09.007. Epub 2010 Oct 20.
Restorative materials exhibit contraction and expansion due to polymerization and water absorption. Each process deforms and stresses a restored tooth structure in opposite direction. This study evaluated the tooth deformations during these competing processes.
Large MOD cavities were prepared in 10 extracted molars. Five were restored with a hydrophobic resin composite (Filtek Supreme, 3M ESPE) and the others with a hydrophilic resin-modified glass-ionomer (Ketac Nano, 3M ESPE). The restored molars and two unrestored controls were stored in water for 24 weeks. The molars were digitized with an optical scanner at baseline, after preparation, restoration, and at 1, 2, 4, 8, 16, and 24 weeks water immersion. The digitized buccal, lingual, and restoration surfaces were analyzed to determine their deformation patterns. The results were statistically analyzed using ANOVA followed by Student-Newman-Keuls post hoc tests (p=0.05).
The buccal and lingual tooth surfaces moved 13-14 μm inward after restoration. After water immersion, cuspal deformation in the resin composite group gradually decreased, reversing the shrinkage deformation within four weeks. The immersed resin-modified glass ionomer group reversed shrinkage deformation within one week, and continued to expand further to 28 μm after 24 weeks. Cuspal deformations after water immersion were significantly different with the two restoratives. Restoration surfaces also expanded after water immersion, while the control teeth showed no significant deformation.
Polymerization shrinkage deformation was compensated by hygroscopic expansion within 4 weeks in teeth restored with a hydrophobic resin composite, while a hydrophilic restorative over-compensated polymerization shrinkage within 1 week causing tooth expansion.
修复材料由于聚合和吸水会发生收缩和膨胀。每个过程都会以相反的方向变形并对修复的牙体结构施加应力。本研究评估了这些竞争过程中牙齿的变形。
在 10 颗拔出的磨牙上制备大 MOD 腔。其中 5 个用疏水性树脂复合材料（Filtek Supreme，3M ESPE）修复，其余 5 个用亲水性树脂改性玻璃离子体（Ketac Nano，3M ESPE）修复。将修复后的磨牙和两个未修复的对照牙在水中储存 24 周。在基线、制备后、修复后以及在水浸泡 1、2、4、8、16 和 24 周时，使用光学扫描仪对磨牙进行数字化。分析数字化的颊面、舌面和修复面以确定其变形模式。使用方差分析（ANOVA）后进行学生-纽曼-凯斯（Student-Newman-Keuls）事后检验（p=0.05）对结果进行统计学分析。
修复后颊面和舌面牙体向内侧移动 13-14μm。水浸泡后，树脂复合材料组牙尖的变形逐渐减小，4 周内收缩变形得到逆转。浸水后的树脂改性玻璃离子组在一周内逆转了收缩变形，并在 24 周后继续扩张至 28μm。水浸泡后的牙尖变形在两种修复体之间存在显著差异。修复表面在水浸泡后也发生扩张，而对照牙没有明显的变形。
用疏水性树脂复合材料修复的牙齿在 4 周内通过吸湿膨胀补偿聚合收缩变形，而亲水性修复体在 1 周内过度补偿聚合收缩变形导致牙齿扩张。
