Objective To evaluate the effect of different convergence angles on the fitness of using selective laser melting( SLM) to fabricate the Co-Cr inner crown, and to compare it with Lost-wax( LW) technique. Methods 60 resin base teeth were prepared by CAD/CAM, comprising 3 types of occlusal convergence (6°,8°,12°) and 20 for each;then each type of the specimens was further di-vided into SLM and LW group ( selective laser melting or Lost-wax) to fabricate the Co-Cr inner crown; there are altogether 6 groups with 10 specimens for each group. Each specimen received the treatment of being cleaned, cemented, and cut. The cement thickness of the inner and outer chamfer edge was then measured by scanning electronic microscopy. Analysis of Variance was performed to deter-mine the differences using SPSS 17. 0 software package. Results With the convergence angles from 6°,8° to 12°, the cement thick-nesses of inner and outer chamfer edge of SLM groups (the outer edge:(59. 20±16. 14)μm, (46. 62± 8. 26)μm, (62. 66±14. 11)μm respectively;inner edge:(59. 74±21. 44)μm, (47. 69±13. 53)μm, (73. 38±23. 03)μm) were smaller than those of the LW groups (outer edge:(63. 52±13. 97) μm, (61. 06±16. 12) μm, (65. 57±13. 85) μm;inner edge:(67. 48±23. 06) μm, (62. 94± 18. 19) μm, (77. 84±17. 52) μm); and the difference was statistically significant(P<0. 05); whatever the crown making method was, the mean cement thickness of inner and outer chamfer edge was as follows:12°>6°>8°group, and the difference was statistically significant(P<0. 05). Conclusions As the convergence angles are within 12°, the marginal fitness of two different Co-Cr inner crown making methods are clinically acceptable. The selective laser melting inner crowns result in smaller marginal gaps than Lost-wax inner crowns, which shows that the marginal fitness of the selective laser melting inner crowns is better than that of the Lost-wax inner crowns.%目的 评价不同聚合度设计对选择性激光熔化技术(selective laser melting,SLM)固定义齿钴铬内冠适合性的影响,并与脱蜡法(Lost-wax,LW)铸造钴铬内冠进行比较.方法 通过CAD/CAM设备制作硬质塑料试件,设计3种聚合度:6°、8°和12°,每种20个;再将每种试件分为SLM组和LW组,分别制作钴铬内冠;共6小组,每组10个样本.每组试件通过清洗、粘接、切割,最后在扫描电镜下测量肩台内外缘粘结剂的厚度并进行统计分析.结果 聚合度从6°、8°到12°SLM组肩台内外缘粘结剂厚度(外缘分别为(59.20±16.14)μm、(46.62±8.26)μm、(62.66±14.11)μm;內缘分别为(59.74±21.44)μm、(47.69±13.53)μm、(73.38±23.03)μm)小于对应LW组(外缘分别为(63.52±13.97)μm、(61.06±16.12)μm、(65.57±13.85)μm;內缘分别为(67.48±23.06)μm、(62.94±18.19)μm、(77.84±17.52)μm);差别具有统计学意义(P<0.05);不论采用哪种内冠制作方法 肩台内外缘粘结剂厚度均值12°组>6°组>8°组,差别具有统计学意义(P<0.05).结论 聚合度控制在12°以内,两种方法 制作的钴铬内冠边缘适合性均在临床可接受范围内,而选择性激光熔化钴铬内冠的边缘适合性要好于脱蜡法铸造钴铬内冠.
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