[The study on the influence of bovine enamel hardness measurement methods on the result evaluation]. 
The variation in hardness of enamel is a frequently used method to evaluate the influence of whiting materials on the enamel.  The purpose of this study is to improve the veracity on the evaluation tests caused by the tooth itself with point selection method.  Three kinds of testing point selection methods on enamel were carried out, i. e. random selection, grid measurement and symmetrical measurement, respectively.  The selected points were used to measure the micro hardness by Vickers.  The influence of the variation of tooth structure itself on the hardness measurements results can be reduced by using testing point selection methods of symmetry, and thus, the accuracy of the test method used in the evaluation of the influence of dental materials on tooth hardness will be guaranteed.