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).