Influence of facial types on sliding mechanics

Background/objectives/aims: The present study considered the effect of orthodontic friction in an evaluation of the relationship of craniofacial pattern and surface micro-roughness of fixed appliances as determinants of treatment response and time. Methods: Brachyfacial (BF; N = 17) and dolichofacial (DF; N = 18) patients treated by canine retraction using sliding mechanics, were identified. One archwire and one bracket per patient (those of the hemi-arch showing the fastest space closure of 4 mm) were subjected to confocal scanning microscopic analysis. Total treatment duration, sliding time, tooth movement rate, topographical surface average roughness (Ra), root mean square roughness (RMS), surface-kurtosis (SK), and surface-skewness (SS) were recorded and compared between groups using the Mann-Whitney U test. Correlations between final micro-roughness and treatment time were investigated using Pearson’s coefficient within each craniofacial type (α = 0.05). The post-treatment appliance surfaces were examined by SEM. Results: BF patients recorded a significantly higher sliding time, lowest retraction rates, and greatest final Ra and RMS (p < 0.001). A comparison of total treatment time and final SK and SS values yielded no significant differences. Significant positive correlations between sliding time and final Ra were identified in both groups. Conclusions: Compared with DF subjects, BF patients registered higher friction between the orthodontic components, required longer sliding time, and showed lower retraction rates.