冷热循环老化对不同光固化复合树脂表面微结构的影响

目的比较几种树脂冷热循环老化后表面形态的改变。方法1 种纳米树脂（Z350）和4 种微混合填料树脂（P60、Z250、
Spectrum、AP-X），以侧壁至中心分层填压固化法制备样块，研磨和抛光侧壁，经水浸泡及5/55 ℃冷热循环40 000次后，分析抛
光侧壁表面粗糙值（Ra）的变化，观察扫描电镜下的微结构变化。结果经冷热循环后，抛光面Ra值呈下降趋势。其中Spectrum
由0.164±0.024 μm降至0.140±0.017 μm（P<0.001），Z250由0.169±0.035 μm降至0.144±0.033 μm（P<0.001），Ra值接近抛光性
能较好的P60（0.121±0.028 μm）。扫描电镜下，5种树脂划痕与凹陷变浅，但Z350样块表面出现裂纹。结论水浸泡及冷热循环
可能对复合树脂产生抛光效应，但也可能导致纳米树脂表面产生裂纹。

Effect of thermal cycling on surface microstructure of different light-curing composite resins

Objective To evaluate the effect of thermal cycling on surface microstructure of different light-curing composite
resins. Methods A nanofilled composite (Z350) and 4 microhybrid composites (P60, Z250, Spectrum, and AP-X) were
fabricated from lateral to center to form cubic specimens. The lateral surfaces were abrased and polished before water storage
and 40 000 thermal cycles (5/55 ºC). The mean surface roughness (Ra) were measured and compared before and after thermal
cycling, and the changes of microstructure were observed under scanning electron microscope (SEM). Results Significant
decreases of Ra were observed in the composites, especially in Spectrum (from 0.164±0.024 μm to 0.140±0.017 μm, P<0.001) and
Z250 (from 0.169±0.035 μm to 0.144±0.033 μm, P<0.001), whose Ra approximated that of P60 (0.121±0.028 μm) with smoothly
polished surface. SEM revealed scratches and shallower pits on the surface of all the 5 resins, and fissures occurred on Z350
following the thermal cycling. Conclusions Water storage and thermal cycling may produce polishing effect on composite
resins and cause fissures on nanofilled composite resins.