Rode Kátia Martins, Kawano Yoshio, Turbino Miriam Lacalle
Department of Restorative Dentistry, School of Dentistry of São Paulo, University of São Paulo (USP), São Paulo, Brazil.
Oper Dent. 2007 Nov-Dec;32(6):571-8. doi: 10.2341/06-163.
This study evaluated the influence of the curing tip distance on cure depth of a resin composite by measuring Vickers microhardness and determining the degree of conversion by using FT-Raman spectroscopy. The light curing units used were halogen (500mW/cm2) and LED (900mW/cm2) at a conventional intensity and an Argon laser at 250mW. The exposure time was 40 seconds for the halogen light, 20 seconds for the LED and 20 and 30 seconds for the Argon laser. The curing tip distances of 0, 3, 6 and 9 mm were used and controlled via the use of metal rings. The composite was placed in a black matrix in one increment at a thickness of 1 mm to 4 mm. The values of microhardness and the degree of conversion were analyzed separately by ANOVA (Analysis of Variance) and Tukey test, with a significance level set at 5%. Correlations were analyzed using the Pearson test. The results obtained conclude that greater tip distances produced a decrease in microhardness and degree of conversion values, while increasing the resin thickness decreased the microhardness and degree of conversion values. A higher correlation between microhardness and the degree of conversion was shown. This study suggests that the current light curing units promote a similar degree of conversion and microhardness, provided that the resin is not thicker than 1 mm and the light source is at a maximum distance of 3 mm from the resin surface.
本研究通过测量维氏显微硬度并使用傅里叶变换拉曼光谱法测定转化率，评估了固化头距离对树脂复合材料固化深度的影响。所使用的光固化设备包括常规强度的卤素灯（500mW/cm2）、发光二极管（LED，900mW/cm2）以及功率为250mW的氩激光。卤素灯的曝光时间为40秒，LED为20秒，氩激光为20秒和30秒。通过使用金属环来控制固化头距离为0、3、6和9毫米。将复合材料以1毫米至4毫米的厚度逐层放置在黑色模具中。分别采用方差分析（ANOVA）和Tukey检验对显微硬度值和转化率进行分析，显著性水平设定为5%。使用Pearson检验分析相关性。所得结果表明，更大的固化头距离会导致显微硬度值和转化率降低，而增加树脂厚度也会降低显微硬度值和转化率。显微硬度与转化率之间呈现出较高的相关性。本研究表明，只要树脂厚度不超过1毫米且光源与树脂表面的最大距离为3毫米，当前的光固化设备就能实现相似程度的转化率和显微硬度。
