单端粘结桥不同固位型设计的应力分析

STRESS ANALYSIS ON DIFFERENT RETAINER DESIGNS OF CANTILEVER RESIN-BONDED FIXED PARTIAL DENTURES

目的分析不同固位型设计对单端粘结桥抗力值和失败模式的影响。方法将54颗离体上颌第一前磨牙按不同固位型设计随机分为C组(传统固位型)、D组(传统固位型+面连接杆)、L组(传统固位型+舌尖覆盖)3组,牙体预备后制作54个镍铬合金单端粘结桥,PANAVIA F粘固。24h后分别测量和观察单端粘结桥试件在垂直向加载和45°舌向加载后的抗力值及失败模式(脱粘、基牙断裂、修复体断裂)。结果垂直加载时,D组、L组抗力值均高于C组,差异有显著性(F=28.059,q=6.390、6.580,P<0.01)。45°舌向加载时,D组、L组抗力值均高于C组,差异有显著性(F=17.066,q=3.907、5.715,P<0.01)。每组的垂直加载与45°舌向加载的抗力值比较,差异均有显著性(t=3.351～6.090,P<0.01)。C组的失败模式均为脱粘,D组、L组的失败模式主要为基牙断裂。结论不同固位型设计可影响单端粘结桥的抗力值和失败模式。与C组相比,D组、L组固位型可更有效地提高单端粘结桥的抗力值。与垂直向外力相比,45°舌向外力对单端粘结桥的破坏更大。

Objective To evaluate the influence of different retainer designs on resistance value and failure mode of canti- lever resin-bonded fixed partial denture. Methods Fifty-four maxillary first premolars were randomly divided into three groups： control group, group D （traditional retainer design＋ occlusal bar）, group L （traditional retainer design＋ lingual cusp coverage）. After abutment preparation,54 nickel-chromium alloy specimens of cantilever resin-bonded fixed partial denture were made and ce- mented with PANABIA F, 24 hours later the subgroups of nine specimens were loaded under vertical and 45 ° lingual direction, re- spectively. Resistance value and failure mode （debonding, abutment fracture, prosthesis fracture） were determined for three de- signs. Results When loaded under vertical direction, both groups D and L showed a significantly higher resistance value than group C （F=28. 059 ;q= 6. 390,6. 580 ;P〈0.01）. When loaded under 45 ° lingual direction, both groups D and L showed a signifi- cantly higher resistance value than group C （F= 17. 066 ;q= 3. 907,5. 715 ; P〈0.01）. The difference between vertical loaded group and 45° lingual loaded group in all three groups was significant （t=3. 351-6. 090,P〈0.01）. Predominant failure was debonding for group C and abutment fracture for both groups D and L. Conclusion Different retainer designs affected the resistance value and failure modes of cantilever resin bonded fixed partial dentures. Compared with group C, retainer design in groups D and L was more effective to improve resistance value of cantilever resin-bonded fixed partial dentures than conventional C retainer design. Force in vertical direction was more harmful than force in 45° lingual direction to cantilever resin bonded fixed partial dentures.