[Prospective study on results of the surgical crown lengthening and its associated factors]

To observe the results of surgical crown lengthening procedure and the factors which affected the success of the surgery.

Crown lengthening surgery was performed on 27 teeth. The distance between margin of tooth and bone crest (MT-B) was obtained greater than 4 mm during the surgeries on 10 teeth which were considered as satisfying group. The other 17 teeth were as temporized group with MT-B < or = 3 mm. The position of the tooth margin was evaluated before surgery, immediately after suturing, and at 4 - 6 weeks after surgery. The occlusal force and tooth mobility were measured immediately after restoration, at 3 and 6 months after surgery.

MT-B was obtained > or = 4 mm and all margins and sites of the teeth were exposed in satisfying group (10/10). At least 1 site with MT-B < 3 mm in temporized group in which there still were 11 sites (16%) in 5 teeth (29%) with subgingival tooth margin at 4 - 6 weeks after surgery. There were more teeth showing increased mobility in temporized group (12/17) than in satisfying group (1/10) after surgery (P < 0.05). The occlusal force of the teeth after surgery and restoration in temporized group was significantly lower than that of their counterpart teeth (P < 0.01), but it was not the case in satisfying group (P > 0.05).

It is suggested that ideal exposure of tooth margin could be obtained if 4 mm from tooth margin to alveolar crest could be created during the crown lengthening surgery. The teeth both with 4 - 5 mm subgingival margin sites and factors limiting surgical performance are not the suitable indications for the surgical crown lengthening.