Mechanical test and two variable regression analysis of cavity design / 实用口腔医学杂志

ABSTRACT

Objective: To study the relationship between the depth and width of cavity design and to analyze the tendency of breaking load in preparations. Methods:Plaster models of mandibular first molar were prepared and magnified by 150%. Cavity on occlusal surface was designed and prepared in a cylinder shape with the depth(mm) of 3.0,4.5 and 6.0,and diameter(mm) of 3.0,4.5 and 6.0,respectively. 8 cavity samples were prepared for each design. The breaking load of the tooth models before and after restoration with self-curing resin was measured by Instron tester.Mechanical model static load test and two variable regression analysis were applied to study the mechanical property of the cavity design. Results:Before restoration, with the increase of depth and diameter, the incidence rate of tooth fracture increased. The width was the main factor. After restoration, the load was undertaken by restoration directly, and could be transfered to tooth and periodontal tissue through restoration uniformly. When the diameter of the cavity increased, the diameter of restoration also increased, and thus decreased the load on local structure of the tooth. With two-regression analysis, the regression equation and regression curve were obtained. Conclusion: The fracture of tooth before and after restoration is related to the diameter and depth of cavity design in cylinder shape. The regression equations of changing tendency of breaking load (Y) in preparation caused by the change of depth(X 1) and diameter(X 2) of cavity obtained by two-regression analysis are presented as follows Before restoration Y=1593.317-51.178 X 1-79.489X 2.After restorationY=1802.928 -192.461X 1+225.128X 2.