[Efficacy of early maxillary slow expansion in mixed dentition on maxillary teeth and alveolar crest in the central segment].

Purpose: To study the effect of slow maxillary expansion(SME) appliance on the development of premolar tooth germ, primary molar and alveolar crest in the central segment of maxilla in the mixed dentition.

Methods: According to the inclusion and exclusion criteria, 17 children (average age 7.41±0.80 years old ) with maxillary transverse deficiency were selected for SME. Before and after treatment, based on cone-beam CT(CBCT) and Dolphin Imaging software, the position of maxillary premolar tooth germ, the position of maxillary primary molar, the shape of maxillary alveolar crest in the central segment were analyzed. SPSS 21.0 software package was used for data analysis.

Results: There was no significant change in the buccal-lingual movement and inclination of the tooth germs of the maxillary first and second premolars relative to the maxillary alveolar bone cortex after expansion(P＞0.05).After expansion, the maxillary alveolar crest in the central segment had an obvious expansion effect(P＜0.05). There was an arch expansion effect in the alveolar crest bottom of the maxillary second primary molar(P＜0.05), but there was no significant difference in the alveolar crest bottom of the maxillary first primary molar before and after treatment. Buccal cusp width of maxillary first and second primary molars increased after arch expansion (P＜0.05) without inclination of alveolar crest(P＞0.05).

Conclusions: SME in the mixed dentition did not affect the position of premolar tooth germ in alveolar bone. SME can expand and buccally tilt central alveolar crest and dental arch, and buccal inclination is greater than that of skeletal expansion and buccal inclination. The closer tooth site is to the first molar, the greater the skeletal effect of arch expansion is at this site. SME is an effective treatment for early maxillary expansion in the clinic.