热循环和机械循环对切削Ti2448和纯钛金瓷结合强度的影响

Effects of thermal and mechanical cycling on the metal-ceramic bond strength of machine-milled Ti2448 alloy and pure titanium

目的研究热循环和机械循环对切削Ti2448和纯钛金瓷结合强度的影响。方法按照ISO9693的标准分别制作纯钛和Ti2448烤瓷试件各30个，每种试件均随机分为3组，A组为对照组，在37℃水浴中保存24h；B组和C组在5～55℃水浴中热循环3000次，在每一个温度下保持60S，然后采用载荷50N、频率4Hz，机械循环20000次（B组）或40000次（C组）。采用三点弯曲实验测试试件的金瓷结合强度，通过扫描电镜和能谱分析金瓷剥脱面和金瓷结合界面的显微结构和成分组成，对结果进行两因素方差分析和Tukey检验。结果A组中，纯钛试件的金瓷结合强度（29．21MPa±2．20MPa）明显小于Ti2448试件（44．86MPa±1.75MPa）（P〈0．01）；纯钛试件和Ti2448试件中，C组与A组之间均有统计学差异（P〈0．01）。扫描电镜和能谱分析结果显示，Ti2448瓷剥脱面有明显的瓷残留，而纯钛瓷剥脱面无明显瓷残留。结论热循环和机械循环处理降低了Ti2448和纯钛的金瓷结合强度。

Objective To evaluate the effects of thermal and mechanical cycling on the metal-ceramic bond strength of machine-milled Ti2448 alloy and commercial pure titanium （cp Ti）. Methods Ceramic-cp Ti （n=30） specimens and ceramic- Ti2448 combinations （n=30） were prepared in accordance with ISO 9693. The specimens from each metal-ceramic combination were randomly divided into three subgroups. In group A or the control group, the specimens were only stored in distilled water for 24 h at 37 ℃; in groups B and C, the specimens were subjected to 3 000 cycles of thermal cycling between 5 and 55 ~℃for a dwell time of 60 s and to mechanical cycling of 20 000 or 40 000 cycles with 50 N load and 4 Hz in distilled water at 37 ℃. A crack initiation test was performed using a universal testing machine in accordance with ISO 9693. Failure types at the metal-ceramic interface and the morphological and elemental composition of this interface were analyzed using a scanning electron microscope and an energy dispersive spectrometer. Statistical analysis was performed via two-way ANOVA and Tukey＇s adjustment test （α=0.05）. Results The bond strength of the ceramic-Ti2448 combination was significantly higher than that of the ceramic-cp Ti combination regardless of fatigue conditions （44.86 MPa±1.75 MPa and 29.21 MPa±2.20 MPa for Ti2448 and cp Ti, respectively; P〈0.01）. The mean bond strengths of ceramic-cp Ti and ceramic-Ti2448 combinations in group C were significantly lower than that of group A （P〈0.01）. Although ceramic-cp Ti combination failed adhesively at the metal-ceramic interface without the ceramic on the substrate surface, Ti2448 frameworks exhibited cohesive failure; as a result, large amounts of residual porcelain were retained on the specimens, Conclusion The metal-ceramic bond strength of cp Ti and Ti2448 is decreased by thermal and mechanical cycling.