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Maxillary dental arch changes following the leveling and alignment stage with lingual and labial orthodontic appliances: a preliminary report of a randomized controlled trial.

BACKGROUND
No randomized controlled trial has tried to compare transverse dental arch changes between the lingual and labial orthodontic fixed appliances in the early stage of treatment.


OBJECTIVE
To compare upper dental arch changes between lingual and labial fixed orthodontic appliances after leveling and alignment.


DESIGN, SETTING
Parallel-groups randomized controlled trial on patients with class I moderate crowding teeth treated at the University of Al-Baath Dental School in Hamah, Syria.


PARTICIPANTS
About 102 patients with crowded teeth and class I malocclusion were evaluated and 58 patients fulflled the inclusion criteria. Randomization was performed using computer generated tables; allocation was concealed using sequentially numbered opaque and sealed envelopes. About 52 participants were analyzed (mean age 21.5 ± 3.2 years). They were randomly distributed into two groups with 26 patients in each (1:1 allocation ratio).


INTERVENTION
Lingual vs labial fixed orthodontic appliances were used.


MAIN OUTCOME MEASURE
Intercanine width, interpremolar width, intermolar width, and arch length were measured on study models before brackets' placement (T1), at the end of leveling and alignment stage (T2).


RESULTS
Statistically significant increase was detected in the intercanine width in the lingual group (1.99 mm, p < 0.001) and in the labial group (1.22 mm, p < 0.001). The interpremolar width had a significant decrease in the lingual group (-0.70 mm, p < 0.001), whereas there was a significant increase in this width in the labial group (1.73 mm, p < 0.001). A significant decrease in intermolar width was detected in the lingual group (-0.79 mm, p < 0.001) whereas a significant increase was observed in the labial group (0.81 mm, p < 0.001). The differences between the two groups were significant for all comparisons (p < 0.001).


CONCLUSION
The labial appliance produced a significant increase in all horizontal transverse arch dimensions, whereas in the lingual appliance group the intercanine width increased significantly in conjunction with a significant narrowing of posterior segments.


FUNDING
The University of Al-Baath Postgraduate Research Budget (UBDS-00786223-PG).