• 临床研究 •

### 辅助固位形对低矮磨牙全冠修复体固位力和边缘适合性的影响

1. 1.山东大学口腔医院修复科，山东省口腔组织再生重点实验室；2.山东大学齐鲁医院口腔科，济南 250012
• 收稿日期:2015-03-25 修回日期:2015-06-02 出版日期:2015-10-01 发布日期:2015-10-01
• 通讯作者: 高旭，副教授，博士，E-mail：gaoxu@sdu.edu.cn
• 作者简介:杨丽媛，硕士，E-mail：757047026@qq.com

### Effect of auxiliary resistance forms on the resistance and marginal fitness of complete crowns for short molar preparations

Yang Liyuan1, Liu Cuiling2, Zheng Zheng1, Zhu Shujin1, Gao Xu1.

1. 1. Dept. of Prosthodontics, School of Stomatology, Shandong University; Shandong Provinical Key Laboratory of Oral Tissue Regeneration, Jinan 250012, China; 2. Dept. of Stomatology, Qilu Hospital, Shandong University, Jinan 250012, China
• Received:2015-03-25 Revised:2015-06-02 Online:2015-10-01 Published:2015-10-01

Abstract:

Objective  To evaluate the effect of different auxiliary resistance forms on the resistance and marginal fitness of complete crowns for short molar preparations. Methods  A total of 70 Nissin resin teeth were prepared with 20° total occlusal convergence, 2.5 mm of occlusocervical height, and a shallow finish line on a milling machine. The milled preparations were then randomly assigned to 7 groups of 10. The first group was used as the control group. A total of 30 dies were modified by preparing interproximal grooves with angles of 0°, 6°, and 20° centered on the mesial and distal surfaces of the dies. The rest of the teeth were prepared with occlusal holes in the center of the occlusal surface milled with the same burs to form 0°, 6°, and 20° holes. Cobalt–chromium copings were fabricated for all specimens. The marginal gap of specific points on the axial surface was measured before and after cementation. The resistance of each specimen was evaluated by applying an external force at an angle of 45° to the long axis of the die by using a universal testing machine in a lingual to buccal direction. The maximum force applied before crown dislodgement was measured. Data were analyzed using the SAS 9.2 software. Results  The results showed that the 0° groove, 0° hole, and 6° hole were effective in improving the resistance of the complete crowns (P<0.05). The 0° groove, 6° groove, 0° hole, 6° hole, and 20° hole had significant difference with the control group in terms of marginal discrepancies (P<0.05). Conclusion  Auxiliary resistance forms with less degree indicate greater resistance force but worse marginal fitness. In clinical practice, if the resistance of a preparation is enough, the auxiliary resistance forms should be avoided from being used.