Rueggeberg F A, Ergle J W, Lockwood P E
Department of Oral Rehabilitation, Medical College of Georgia, School of Dentistry, Augusta, USA.
Dent Mater. 1997 Nov;13(6):360-4. doi: 10.1016/s0109-5641(97)80107-8.
This study evaluated the effect of increased levels of photoinitiator components on biaxial flexural strength, monomer conversion, and dynamic thermal properties of an unfilled model resin system in both the light-cured only state as well as after post-cure heating.
Unfilled polymer discs were made using 50/50 mole% Bis-GMA and TEGDMA and were rendered photo-curable using a common (normal) concentration of photoinitiators (camphorquinone 0.3 wt% and DMAEMA 0.75 wt%) as well as twice and four-fold this amount. Specimens were light-cured and left unheated or were post-cure heated in a commercial unit. Biaxial flexural strength was obtained at a constant stressing rate (100 MPa/s), monomer conversion was determined using FTIR, and dynamic mechanical thermal properties (E', E", and Tg) were measured with DMA. Data were analyzed using ANOVA and Turkey-Kramer post-hoc test (p < 0.05).
Increased levels of photoinitiator above normal significantly increased monomer conversion and Tg values for unheated as well as for post-cure heated specimens. Biaxial flexural strength for light-cured only groups remained unaffected by change in initiator concentration, but was significantly increased by post-cure heating. Increase in initiator concentration did not affect E' values for post-cured specimens, but significantly increased values for the unheated, light-cured only groups. E" values for post-cure heated specimens were significantly lowered by increasing initiator concentration.
The clinical implications of these results indicate that increasing photoinitiator levels results in post-cure heated restorations with significantly higher Tg and monomer conversion values. Use of elevated initiator concentrations for post-cured resins could result in restorations with enhanced resistance to deformation at elevated oral temperatures as well as significantly lower amounts of leachable components.
本研究评估了光引发剂成分含量增加对未填充模型树脂体系在仅光固化状态以及后固化加热后的双轴弯曲强度、单体转化率和动态热性能的影响。
使用50/50摩尔%的双酚A双甲基丙烯酸缩水甘油酯（Bis-GMA）和三乙二醇二甲基丙烯酸酯（TEGDMA）制作未填充的聚合物圆盘，并使用常见（正常）浓度的光引发剂（樟脑醌0.3 wt%和甲基丙烯酸二甲氨基乙酯0.75 wt%）以及该浓度的两倍和四倍来使其具有光固化性。样本进行光固化，不加热或在商用设备中进行后固化加热。以恒定应力速率（100 MPa/s）获得双轴弯曲强度，使用傅里叶变换红外光谱（FTIR）测定单体转化率，并用动态热机械分析（DMA）测量动态力学热性能（储能模量E'、损耗模量E''和玻璃化转变温度Tg）。数据采用方差分析（ANOVA）和Turkey-Kramer事后检验（p < 0.05）进行分析。
光引发剂含量高于正常水平显著提高了未加热以及后固化加热样本的单体转化率和Tg值。仅光固化组的双轴弯曲强度不受引发剂浓度变化的影响，但后固化加热使其显著提高。引发剂浓度的增加对后固化样本的E'值没有影响，但显著提高了未加热的仅光固化组的值。后固化加热样本的E''值随着引发剂浓度的增加而显著降低。
这些结果的临床意义表明，增加光引发剂含量会使后固化加热的修复体具有显著更高的Tg和单体转化率值。在后固化树脂中使用更高浓度的引发剂可能会使修复体在口腔温度升高时具有更好的抗变形能力，以及显著减少可溶出成分的量。
