牙槽骨吸收量对牙周膜面积、力学支点和桩核-牙根联合体抗折力学性能的影响

目的探讨牙槽骨吸收量对牙周膜面积、力学支点和桩核-牙根联合体抗折力学性能的影响。方法用108个相同长度、锥度和直径的有机玻璃模拟上中切牙牙根,常规铸造,粘固桩核,分成13组按不同牙槽骨吸收量和力学支点制作加载基底,并根据牙周组织解剖生理特点设计了三种牙周力学方式。以Instron4302力学测试机进行垂直于牙根长轴加载压缩测试,加载速度1 mm/m in,至桩核松动、脱位或牙根折断,记录最大载荷并计算牙周膜面积。结果牙槽骨吸收量和力学支点为0 mm和12/12,1 mm和11/12,2 mm和10/12,3 mm和9/12,3.5 mm和8.5/12,4 mm和8/12,4.5 mm和7.5/12 mm,5 mm和7/12,5.5 mm/和6.5/12,6 mm和6/12,7 mm和5/12,8 mm和4/12,9 mm和3/12组牙周膜面积(mm2)和抗折力均数(N)分别为178.95和232.90±25.93,159.64和195.58±12.46,141.18和173.92±13.51,123.27和154.00±11.74,106.14和132.25±14.29,89.67和96.86±6.20,73.90和59.14±7.28,58.82和52.52±5.82,44.44和45.90±7.40,30.76和58.60±6.63。牙槽骨失量(%)与牙周膜失量(%)呈线性关系、牙槽嵴吸收量与抗折力呈线性关系、牙周膜面积失量(%)与抗折力失量(%)呈线性关系、支点与抗折力失量(%)呈线性关系。结论牙槽骨吸收可引起牙周膜面积减小、力学支点下移和桩核-牙根联合体抗折力下降。

Effects of the Loss of Alveolar Bone on the Areas of Periodontal Ligament, Mechanical Fulcrum and Fracture Resistance of Root and Post-core System

OBJECTIVE: To assess the effects of loss of alveolar bone on the areas of periodontal ligament (PL), mechanical fulcrum and fracture resistance of root and post-core system. METHODS: One hundred and eight simulated roots in the same length, taper and diameter were made of polymethylmethacrylate and were divided into 13 groups. Then the wax patterns of post-cores were casted and cemented. Each specimen was embedded in acrylic resin in accordance with different loss of alveolar bone and different mechanical fulcrum. Base on the anatomic and physiological special features of the periodontal tissues, three mechanical methods were designed. The compress test was run by the speed of 1 mm/min and the fracture resistance was recorded. The areas of periodontal ligament were measured and calculated. RESULTS: When the loss of alveolar bone and the mechanical fulcrum were 0 mm and 12/12 group, 1 mm and 11/12 group, 2 mm and 10/12 group, 3 mm and 9/12 group, 3.5 mm and 8.5/12 group, 4 mm and 8/12 group, 4.5 mm and 7.5/12 group, 5 mm and 7/12 group,5. 5 mm and 6.5/12 group, 6 mm and 6/ 12 group, 7 mm and 5/12 group, 8 mm and 4/12 group, 9 mm and 3/12 group, the means of the areas of PL (mm2) and fracture resistance (N) were 178.95 and 232. 90 +/- 25. 93, 159. 64 and 195.58 +/- 12.46, 141.18 and 173.92 +/- 13.51, 123.27 and 154.00 +/- 11.74, 106.14 and 123.25 +/- 14.29, 89.67 and 96.86 +/- 6. 20, 73.90 and 59.14 +/- 7.28, 58.82 and 52.52 +/- 5. 82, 44.44 and 45.90 +/- 7.40, 30.76 and 58.60 +/- 6.63 (mm, N). The linear correlations were found between the percentage of the loss of alveolar bone and surplus areas of PL, the loss of alveolar bone and the fracture resistance of root and post-core system, the percentage of the areas of PL and the fracture resistance of root and post-core system, the distance of the fulcrum and the percentage of the loss of alveolar bone. CONCLUSION: The loss of alveolar bone caused the decrease in areas of PL, the dessent of mechanical fulcrum, and the diminution of the fracture resistance of root and post-core system.