Comparative study of transverse dental changes induced by palatally-buccally applied 2K-loop appliance and palatally applied pendulum appliance

Introduction
Difference in design of distalization appliances resulted in a difference in dimensions of dental arch after ending of distalization.

Objectives
The current study aimed to evaluate transverse dental changes caused by using both 2K-loop and pendulum appliances, and to compare different effects of both appliances using transverse dental measurements.

Material and methods
Study group included 16 participants with dental bilateral full cusp or end-to-end class II molar relationship equally divided into two groups. First group, 2K-loop group, consisted of 5 girls and 3 boys (mean age, 10.8 ± 1.2 years) treated with PB applied 2K-loop appliance. Second group, pendulum group included 5 girls and 3 boys (mean age, 11.1 ± 1.1 years) treated with palatally applied pendulum appliance. Study models were taken at the beginning of treatment and at the end of molar distalization. Paired samples t-test was applied to evaluate mean changes during treatment in each group, and to compare measurement differences between the two groups.

Results
Statistical analysis of the measurements showed an increase in inter-molar distance of the first molars in the two groups. The increase was significant in the 2K-loop group, with 4.33 ± 0.81 mm, and not significant in the pendulum group (2.19 ± 2.00 mm). There was a significant distal rotation in the upper right first molars of 7.83° ± 2.92°, and 8.66° ± 2.73° on the left with PB 2K-loop appliance. Also, significant mesial rotation on the upper right first molars was observed with 4.83° ± 3.97°, and 4.83° ± 2.71° on the left with palatally applied pendulum appliance.

Conclusions
PB acting on 2K-loop appliance causes an increase in the inter-molar distance and distal rotation of maxillary first molars. Palatally acting pendulum appliance results in mesial rotation of maxillary first molars. In cases where maxillary molars need to be de-rotated and to increase inter-molar distance, PB 2K-loop appliance is a better choice.