Surgical crown lengthening: a 12-month clinical wound healing study

Surgical crown lengthening has been proposed as a means of facilitating restorative procedures and preventing periodontal injuries in teeth with structurally inadequate clinical crowns or exposing tooth structure in the presence of deep, subgingival pathologies which may hamper the access for proper restorative measures. The few clinical studies in the current literature on postsurgical soft tissue modifications after crown lengthening procedures report conflicting results. The present study was designed to assess the alterations of the marginal periodontal tissues as an immediate outcome of surgical crown lengthening and over a 12-month healing period.

The patient sample included 30 patients (84 teeth) who presented with various conditions hampering proper restorative measures in one or more teeth and, therefore, requiring surgical exposure of tooth substance. After initial supportive therapy, the patients were recalled for a baseline examination, and the following parameters were evaluated at interproximal and buccal/lingual sites of each experimental tooth: plaque index, gingival index, position of the gingival margin, probing depth, and attachment level. After baseline examination, the patients underwent apically positioned flap surgery with osseous and connective tissue attachment resection. During surgery, the amount of resection and the achieved lengthening of the clinical crown were evaluated. The patients were enrolled in a maintenance program including professional tooth cleaning every 2 to 4 weeks. The patients were reexamined 1, 3, 6, 9, and 12 months postoperatively.

1) Immediately after surgery, a significantly (P < 0.001) increased clinical crown length of 3.7 +/- 0.8 mm (mean) at interproximal and 4.1 +/- 0.9 mm (mean) at buccal/lingual sites was achieved; 2) healing resulted in a statistically significant coronal displacement of the gingival margin of 3.2 +/- 0.8 mm at interproximal (P < 0.001) and 2.9 +/- 0.6 mm at buccal/lingual (P < 0.002) sites; and 3) as a consequence of this postsurgical soft tissue regrowth, the amount of the available tooth structure immediately after surgery decreased to 0.5 +/- 0.6 mm at interproximal sites (P < 0.0015) and to 1.2 +/- 0.7 mm at buccal/lingual sites (P < 0.001) at the 12-month examination.

The results of the present clinical investigation demonstrated that during a 1-year period of healing following surgical crown lengthening, the marginal periodontal tissue showed a tendency to grow in a coronal direction from the level defined at surgery. This pattern of coronal displacement of the gingival margin was more pronounced (P < 0.001) in patients with "thick" tissue biotype and also appeared to be influenced by individual variations in the healing response (P < 0.001) not related to age or gender.