Comparative study of six different soft tissue analyses in evaluation of soft tissue profile in skeletal Class III malocclusion

Objective To find out the most sensitive cephalometric variable in the evaluation of the soft tissue profile in skeletal Class Ⅲ patients.Methods Cephalographs were taken in one hundred and forty-five individuals (including 65 subjects with normal occlusion,40 patients with skeletal Class Ⅲ malocclusion before treatment and 40 patients with skeletal Class Ⅲ malocclusion after treatment).Six different soft tissue analyses were employed and 14 variables were measured.Multiple factorial discriminate analysis and ROC (receiver operating characteristic curve) were used to find out the valuable diagnostic variables to evaluate the soft tissue profile.Results Multiple factorial discriminate analysis indicated that LL-Sn⊥ FH,UL-B,Lip-Diff and H angle were valuable in diagnosing skeletal Class Ⅲ profile.The further study of ROC indicated that LL-Sn⊥ FH was more powerful in diagnosing and the AUC (area under the curve) was 0.970,while Lip-Diff and H angle were better at evaluating the treatment effect of skeletal Class Ⅲ profile and the AUCs were 1.000 and 0.919,respectively.These three variables had high sensitivity and specificity.Conclusion Lip-Diff was the most efficient and convenient variable in the evaluation of Class Ⅲ profile. Key words: Soft tissue analyses; Class Ⅲ malocclusion; Cephalometric study