{'fraction_non_alphanumeric': 0.03493191237418591, 'fraction_numerical': 0.02427471876850207, 'mean_word_length': 4.297805642633229, 'pattern_counts': {'":': 0, '<': 4, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Change in clinical crown height in adult patients treated by means of the multi-bracket appliance with extraction of four first premolars.

OBJECTIVE
To evaluate the gingival condition due to adult orthodontic treatment using the clinical crown height (CCH) as an index.


DESIGN
Retrospective study.


SETTING
Department of Orthodontics at a university.


PARTICIPANTS
A total of 21 adult female patients with healthy periodontal tissue were treated by means of the multi-bracket appliance with extraction of four first premolars.


METHODS
Three-dimensional (3D) digital dental models were reconstructed to assess the vertical movement of the free gingival margin caused by adult orthodontic treatment. Pre- and post-treatment CCH were measured, and changes in CCH due to treatment were examined.


RESULTS
The change in CCH by orthodontic treatment was able to be assessed objectively using 3D digital models of the dental casts. In the upper dentition, a significant reduction in CCH was found on the labial and lingual sides of the central incisor, with a mean of -0.28 mm and -0.34 mm, respectively (P < 0.001). In contrast, a significant increase in CCH was found on the labial side of the lateral incisor with a mean of 0.75 mm (P < 0.001). In the lower dentition, CCH on the lingual side of the canine, the second premolar and the first molar increased significantly (P < 0.001), with a mean of 0.41 mm, 0.45 mm and 0.50 mm, respectively. For the buccal side, the second premolar showed a significant increase in CCH with a mean of 0.61 mm (P < 0.001).


CONCLUSION
By using the CCH as an index, it was possible to assess the gingival condition after active orthodontic treatment.