Root bifurcation lesions generally appear in the root bifurcation area, can be based on the probe and X-ray to determine the degree of the lesion, according to the degree of the lesion is divided into the following four degrees: 1, I degree: belongs to the early stage of the lesion, the depth of periodontal pockets up to the root bifurcation, can be probed into the root bifurcation, but the bone resorption of the alveolar bone is slight, the X-ray shows that there is no bone resorption, the doctor with the probe can be probed into the root bifurcation, but not horizontally probed into the; 2, II degree: more than one root of the tooth Fork area there has been bone resorption, but not with the opposite side of the communication, X-ray shows only periodontal membrane widening, or reduced bone density, the doctor with the probe can be partially extended into the root fork, but the entire root fork is not connected; 3, III degree: inter-root alveolar bone resorption, the probe can pass through the periodontal pockets covered by soft tissue, not directly exposed to the oral cavity, the X-ray shows that the area of the bone disappeared, transmissible, the use of probes can be Horizontal through the root bifurcation, but can not be visualized in the oral cavity to the location of the root bifurcation; 4, IV degree: complete destruction of the inter-root bone spacing, gingival recession, the root bifurcation area is completely open, can be visualized, X-ray film is similar to the III degree of the lesion, with the eyes can be visualized root bifurcation, with the probe can be completely through the root bifurcation, at this time, suggesting that the alveolar bone, gingival atrophy is serious.