Changing of Maxillary Gingival Margin Locations Following Crown Lengthening Surgery

Objectives: The purpose of this study is to observe the changing of gingival margin locations of the maxillary anterior teeth during and after the crown lengthening surgery in Chinese patients. Also the influence of periodontal biotype on the stability of gingival margin locations was investigated.
Methods: Seventeen patients receiving the crown lengthening surgery at 45 maxillary anterior teeth were included. Clinical measurements were recorded at middle, mesial, and distal sites of facial gingival margins. All of the measurements were repeated at baseline, after reflecting the flaps, after suture, 2 weeks, 1 month, and 2 months after surgery.
Results: 1) After flap reflection, the gingival margin displaced apically by 1.10±0.68 mm at mesial sites, 0.77±0.41mm at middle sites and 1.00±0.59 mm at distal sites compared with the primary incisions (P<0.05). 2) After suture, there was statistically significant apical displacement of the margin by 0.93±0.80 mm, 0.58±0.62 mm and 0.89±0.76 mm compared with the primary incisions (P<0.05). 3) Compared with the location after suture, significant coronal displacement of the gingival margin occurred by 0.82±0.59 mm at medial sites, 0.48±0.35 mm at middle sites and by 0.72±0.60 mm at distal sites at 2 weeks (P<0.05); the corresponding changes were 1.17±0.48 mm 0.73±0.37 mm and 1.07±0.50 mm individually at 1 month (P<0.05); and 1.31±0.55 mm, 0.80±0.45 mm and 1.18±0.57 mm individually at 2 month (P<0.05).4) Two-month after surgery, gingival margins of the flaps of thick-flat biotype showed significantly more coronal displacement by 1.63±0.72mm, 1.23±0.26mm and 1.37±0.81mm respectively, compared with those of thin-scalloped biotype, 1.03±0.23mm, 0.55±0.33mm and 0.87±0.44mm respectively (P<0.05).
Conclusions: In Chinese patients, we found complex changing of gingival margin locations following crown lengthening surgery. 1) After flap reflection, there is a significant apical displacement of the gingival margins. 2) During the 2-month period of healing, the gingival margins show a tendency of coronal displacement compared with those after sutureduring the surgery. 3) Gingival margins with thick-flat biotype show more coronal displacement than those with thin-scalloped biotype.