The ability of orthodontists and laypeople to discriminate mandibular stepwise advancements in a Class II retrognathic mandible

Abstract

ObjectivesThis study analysed the ability of orthodontists and laypeople to discriminate mandibular stepwise advancements. Materials and methodsFour pictures (in duplicate) were taken of a male patient with Class II malocclusion and mandibular deficiency with the mandible positioned in habitual maximum intercuspation (HMI) and with stepwise advancements of 2mm, 4mm and 6mm. These images were examined by orthodontists (n=30) and laypeople (n=30). The Wilcoxon signed-rank test was used to evaluate intra-examiner agreement. Intra-examiner ability to discriminate stepwise mandibular advancements was examined by Friedman's test. A Mann-Whitney's test was carried out to analyse score difference between orthodontists and laypeople. Type I error (alpha) was set as 5% for all statistical tests. ResultsWe observed a satisfactory to excellent level of methodological reliability. While laypeople were able to notice mandibular advancements ≥4mm (p<0.05), orthodontists were able to observe mandibular advancements ≥2mm (p<0.05). The orthodontists were more critical than laypeople with regard to the facial profile evaluation when facial convexity increased (p<0.001), but no significant difference was observed when the sagittal maxillo-mandibular relationship approached normality (p<0.05). ConclusionsConsidering that the mean sagittal mandibular growth due to the use of functional orthopaedic appliances is reported in the literature as 2mm, it seems that laypeople may not able to discriminate this amount of change in facial-profile attractiveness.