One hundred patients who had eight maxillary and mandibular molars(third molars excluded) were consecutively selected for the study subjects. The subjects provided a total of 800 molars, i.e., 400 maxillary and 400 mandibular molars. A decision about root fusion was made on the radiographic examination. Probing depth, plaque index, gingival index and mobility were measured.

The results were as follows.

1. 15.9% of the molars had a fused root. 22% of the maxillary molars and 9.8% of the mandibular molars had a fused molars.

2. In maxillary molars, the results of probing depth, plaque index, gingival index, mobility are more higher in test group than in control group, and there was a significantly difference except plaque index of maxillary first molars group(p<0.01).

3. In mandibular molars, the results of probing depth, plaque index, gingival index, mobility are more higher in test group than in control group, and there was a significantly difference(p<0.01).

As a result of this study, it can be concluded that, in management of molars with a root fusion, we should detect the molars through the precise radiographic examination, early periodontal treatment and systematic treatment plan should be chosen. And postoperative continuing supportive periodontal therapy is needed.