[A primary observation of the long-term effect of modified crown lengthening procedure].

Objective: To observe the effect of modified surgical crown lengthening procedure and discuss the factors which could affect the periodontal health of the operated teeth.
Methods: Seventeen patients, a total of 20 teeth, who received the modified crown lengthening surgery were recruited in a retrospective study (1 - 6 years). The periodontal status of the operated teeth was compared with the adjacent and the contralateral natural teeth respectively.
Results: One out of seventeen patients appeared root fracture after surgery, one patient wasn't satisfied with the color of the molar's metal crown, other fifteen patients were satisfied with the esthetics and function of the teeth. The sites where probing depth was 4 mm just accounted for 4% (5/120) of the operated teeth, and the probing depth of the other sites was less than or equal to 3 mm. Although 83% (33/40) of buccal and lingual sites of the teeth exhibited various degrees of bleeding index, the periodontal indices of the operated teeth and the adjacent teeth. The position of the crown margin had a significantly negative correlation with the bleeding index (r = -0.742), and the plaque index was moderately correlated with the bleeding index (r = 0.480).
Conclusions: The modified surgical crown lengthening indicated a good effect, which could be an alternative method to save the residual crown and root. The position of crown margin might be the main factor which influences the periodontal health of the teeth.