[Clinical research for non-extraction treatment of maxillary mild-to-moderate crowding with Damon technology　]

To compare the clinical efficacy of non-extraction treatment in maxillary mild-to-moderate crowding cases with Damon self-ligating system and Roth traditional brackets.

Sixty skeletalⅠorthodontic patients were selected in this study. They were divided into DamonⅠ, RothⅠ, DamonⅡ and RothⅡ group according to the bracket species and maxillary crowding degrees. Lateral cephalometric radiographs and models were measured before and after aligning and leveling to analyze the changes in dental arch and soft and hard tissue using SPSS 19.0 software package.

After non-extraction treatment of cases with mild (Ⅰ) crowding, significant increase was found in dental width ,dental length and upper incisor torque produced by two brackets. However, there was no significant difference between the two groups. After non-extraction treatment of cases with moderate(Ⅱ) crowding, the width of maxillary canines (1.81 mm) and premolars (2.29 mm) of Damon Ⅱ group were significantly greater than those of Roth Ⅱ group (1.66 mm, 1.80 mm) (P<0.05). The changes of arch length (3.19 mm)and upper incisor torque (9.1°) in Damon Ⅱ group were significantly less than those in Roth Ⅱ group (3.85 mm, 14.5°). There was no significant difference of increased widths between maxillary molars in the two groups.

With the increase of maxillary crowding level, the advantages of expansion and controlling the torque of anterior teeth are more obvious in non-extraction treatment using Damon self-ligating system.