Clinical crown height changes in adult patients after non-extraction, orthodontic treatment: a retrospective cohort study

Objective: To assess changes in clinical crown height (CCH) in adult orthodontic patients treated by fixed appliances to distalise the molars.Design: Retrospective case series study.Setting and patients: A total of 30 adults with healthy periodontal tissues who received orthodontic treatment at the Department of Orthodontics, Yokohama, Japan and its related orthodontic clinic were assessed.Methods: CCH was measured as the distance from the gingival margin to the crown plane perpendicular to the tooth axis. Treatment changes of CCH of each tooth were examined on the labial/buccal and lingual/palatal side.Results: In the upper dentition, on the labial/buccal side, the CCH of the lateral incisors, canines, first premolars, first molars and second molars were increased significantly (P < 0.01), with a median value of 0.41 mm, 0.43 mm, 0.28 mm, 0.43 mm and 0.55 mm, respectively. In contrast on the palatal side, the CCH of the central incisors, first molars, and second molars decreased significantly (P < 0.01), with a median value of -0.41 mm, -0.30 mm and -0.20 mm, respectively. In the lower dentition on the labial/buccal side, the CCH of the first premolars, second premolars and first molars were increased significantly, with a median value of 0.39 mm (P < 0.01), 0.43 mm (P < 0.01) and 0.19 mm (P < 0.05), respectively. The second molars exhibited a significant decrease in CCH with a median value of -0.26 mm (P < 0.05). On the lingual side, the CCH of the central incisors, lateral incisors, canines, first premolars, second premolars and first molars were increased significantly (P < 0.01), with a median value of 0.28 mm, 0.22 mm, 0.31 mm, 0.37 mm, 0.26 mm and 0.28 mm, respectively.Conclusion: Significant differences were observed in CCH before and after treatment for many teeth, the average change was less than 0.5 mm. The impact on the long-term health of the periodontal tissue is unknown.