Bicalho Aline Aredes, de Souza Silas Júnior Boaventura, de Rosatto Camila Maria Peres, Tantbirojn Daranee, Versluis Antheunis, Soares Carlos José
Federal University of Uberlandia, Uberlandia, MG, Brazil.
University of Tennessee Health Science Center, Memphis, TN, USA.
Dent Mater. 2015 Dec;31(12):1523-32. doi: 10.1016/j.dental.2015.09.023. Epub 2015 Oct 28.
Evaluate the effect of environment on post-gel shrinkage (Shr), cuspal strains (CS), microtensile bond strength (μTBS), elastic modulus (E) and shrinkage stress in molars with large class II restorations.
Sixty human molars received standardized Class II mesio-oclusal-distal cavity preparations. Restorations were made with two composites (CHA, Charisma Diamond, Heraus Kulzer and IPS Empress Direct, Ivoclar-Vivadent) using three environment conditions (22°C/50% humidity, 37°C/50% humidity and 37°C/90% humidity) simulated in custom developed chamber. Shr was measured using the strain gauge technique (n=10). CS was measured using strain gauges. Half of the teeth (n=5) were used to assess the elastic modulus (E) and Knoop hardness (KHN) at different depths using microhardness indentation. The other half (n=5) was used to measure the μTBS. The composites and environment conditions were simulated in a two-dimensional finite element analysis of a tooth restoration. Polymerization shrinkage was modeled using Shr data. The Shr, CS, μTBS, KHN and E data were statistically analyzed using two-way ANOVA and Tukey test (significance level: 0.05).
Both composites had similar Shr, CS, μTBS and shrinkage stress. CHA had higher elastic modulus than IPS. Increasing temperature and humidity significantly increased Shr, CS and shrinkage stress. μTBS were similar for groups with lower humidity, irrespective of temperature, and higher with higher humidity. E and KHN were constant through the depth for CHA. E and KHN values were affected by environment only for IPS, mainly deeper in the cavity. Shrinkage stress at dentin/composite interface had high inverse correlation with μTBS. Shrinkage stress in enamel had high correlation with CS.
Increasing temperature and humidity caused higher post-gel shrinkage and cusp deformation with higher shrinkage stresses in the tooth structure and tooth/restoration interface for both composites tested. The chamber developed for simulating the oral environment conditions will improve the realism of in vitro studies. Clinical significance Simulating oral temperature and humidity is important to better determine the biomechanical behavior of composite resin restoration. Avoiding high humidity during restorative procedures using rubber dam isolation may reduce cuspal deformation and shrinkage stress and improve the bonding strength of posterior composite restorations.
评估环境对有大的二类洞修复体磨牙的凝胶后收缩率（Shr）、牙尖应变（CS）、微拉伸粘结强度（μTBS）、弹性模量（E）及收缩应力的影响。
60颗人磨牙接受标准化的二类近中-咬合-远中窝洞预备。使用两种复合树脂（CHA，Charisma Diamond，贺利氏古莎公司；IPS Empress Direct，义获嘉伟瓦登特公司）在定制开发的试验箱中模拟三种环境条件（22°C/50%湿度、37°C/50%湿度和37°C/90%湿度）制作修复体。使用应变片技术测量Shr（n = 10）。使用应变片测量CS。一半牙齿（n = 5）用于通过显微硬度压痕评估不同深度处的弹性模量（E）和努氏硬度（KHN）。另一半（n = 5）用于测量μTBS。在牙齿修复体的二维有限元分析中模拟复合树脂和环境条件。使用Shr数据对聚合收缩进行建模。使用双向方差分析和Tukey检验对Shr、CS、μTBS、KHN和E数据进行统计学分析（显著性水平：0.05）。
两种复合树脂的Shr、CS、μTBS和收缩应力相似。CHA的弹性模量高于IPS。温度和湿度升高显著增加Shr、CS和收缩应力。湿度较低的组，μTBS相似，与温度无关，湿度较高时μTBS较高。CHA的E和KHN在整个深度保持恒定。E和KHN值仅IPS受环境影响，主要在窝洞较深部位。牙本质/复合树脂界面处的收缩应力与μTBS呈高度负相关。釉质中的收缩应力与CS呈高度相关。
对于所测试的两种复合树脂，温度和湿度升高导致更高的凝胶后收缩率和牙尖变形，在牙齿结构和牙齿/修复体界面产生更高的收缩应力。为模拟口腔环境条件而开发的试验箱将提高体外研究的真实性。临床意义模拟口腔温度和湿度对于更好地确定复合树脂修复体的生物力学行为很重要。在使用橡皮障隔离的修复操作过程中避免高湿度可能会减少牙尖变形和收缩应力，并提高后牙复合树脂修复体的粘结强度。
