Loza-Herrero M A, Rueggeberg F A, Caughman W F, Schuster G S, Lefebvre C A, Gardner F M
Restorative Sciences Department, School of Dentistry, University of Puerto Rico.
J Dent Res. 1998 Feb;77(2):426-31. doi: 10.1177/00220345980770021201.
Physical property enhancement in light-cured resin composites from post-cure heating is attributed to free radicals created during initial photocuring, the number of which decreases following initial light-curing. Clinically, it is important to know when the number of remaining free radicals is too low to provide for additional conversion of monomer in post-cure-heated specimens. The hypothesis tested is that the potential for additional conversion in post-cure-heated resin composite restorations is dependent upon the time after initial light-curing at which the specimen is exposed to heat treatment. This research examined the effect of delay in post-cure heating after initial photo-activation on strength and monomer conversion of a commercial resin composite material. Discs (10 x 1 mm) of Herculite XRV (Kerr/Sybron, Orange, CA) were photocured at standardized conditions. One group was left unheated, and another was subjected to post-cure heating (Brilliant DI-500, Coltène AG, Altstätten, Switzerland) at the following times after being light-cured: 5 and 30 min, and 6, 24, 48, 72, 96, and 120 hrs. After the appropriate delay time, unheated and heated specimens (n = 10) were tested for biaxial flexural strength at a constant stressing rate. Recovered, fractured strength specimens (n = 10) were analyzed for cure by means of IR spectroscopy. Post-cure heating increased strength over that of the unheated specimens only for the shortest delay times: 5 or 30 min. Thereafter, strength values were statistically equivalent (p < 0.05). Delay in heating did not significantly enhance strength of post-cure-heated specimens, but delay in time did improve strength of the unheated groups. The greatest monomer conversion was obtained when post-cure heating was applied within 6 hrs following light-curing. The difference in cure between unheated and heated specimens remained significant up to 96 hrs of delay. Flexural strength of post-cure-heated specimens remained unchanged with time delay for heating specimens. Maximal monomer conversion of post-cured specimens is obtained only within 6 hrs of light-curing. The potential for additional conversion arising from post-cure heat treatment is dependent upon the time following initial curing at which heat is applied following initial light-curing. However, delay in heat application has no influence on flexural strength.
后固化加热使光固化树脂复合材料的物理性能增强，这归因于初始光固化过程中产生的自由基，而在初始光固化后，自由基的数量会减少。临床上，了解剩余自由基数量何时过低而无法使后固化加热的试样中的单体进一步转化非常重要。所检验的假设是，后固化加热的树脂复合材料修复体中进一步转化的潜力取决于初始光固化后试样接受热处理的时间。本研究考察了初始光活化后延迟后固化加热对一种商用树脂复合材料的强度和单体转化率的影响。将Herculite XRV（Kerr/Sybron，加利福尼亚州奥兰治）的圆盘（10×1毫米）在标准条件下进行光固化。一组不加热，另一组在光固化后的以下时间进行后固化加热（Brilliant DI - 500，Coltene AG，瑞士阿尔特施泰滕）：5分钟和30分钟，以及6、24、48、72、96和120小时。在适当的延迟时间后，对未加热和加热的试样（n = 10）以恒定的加载速率测试其双轴弯曲强度。对回收的断裂强度试样（n = 10）通过红外光谱分析固化情况。后固化加热仅在最短延迟时间（5或30分钟）时比未加热的试样强度有所提高。此后，强度值在统计学上相当（p < 0.05）。加热延迟并未显著提高后固化加热试样的强度，但时间延迟确实提高了未加热组的强度。当在光固化后6小时内进行后固化加热时，单体转化率最高。未加热和加热试样之间的固化差异在延迟96小时内仍很显著。后固化加热试样的弯曲强度随加热试样的时间延迟保持不变。后固化试样的最大单体转化率仅在光固化后6小时内获得。后固化热处理产生的进一步转化潜力取决于初始光固化后施加热量的时间。然而，加热延迟对弯曲强度没有影响。
