Effect of Clark’s twin block appliance and upper premolar extraction treatment modality on smile aesthetics in skeletal class II malocclusion: a retrospective cross-sectional study

Abstract

ABSTRACT Introduction Treatment undertaken during growth has various advantages over camouflage treatment including an improved profile and treatment stability. The objective of this study was to compare pre- and post-treatment smile variables in class II malocclusion population treated via functional appliance or upper first premolar extraction. Materials and methods A cross-sectional study was conducted at a tertiary care hospital that included frontal closeup smile (FCS) pictures of 40 patients treated with Clark’s twin block (CTB) appliance and upper premolar extraction (UPE). Smile ratios were calculated, and improvement in smile aesthetics were scored on a visual analogue scale (VAS) by a panel of raters of laypersons, general dentists and orthodontists with 20 subjects in each panel. Friedman and Wilcoxon signed rank tests were used to determine differences between pre-, mid- and post-treatment smile variables. Independent t-test was used to measure differences in improvement of smile aesthetic scores, while simple and multiple linear regression analyses were used to determine any associations between smile aesthetic scores and variables. Results CTB group showed highly statistically significant differences for smile index (SIR), interlabial gap ratio (IGR), visible dentition width ratio (VDWR), archform ratio (AFR), mandibular incisal show ratio (MnIR) and smile arc ratio (SAR). On comparison of post-treatment smile variables between the two treatment groups, statistically significant differences were observed for buccal corridor ratio (BCR) (p = 0.01) and AFR ratios. Conclusions Higher smile improvement scores were seen with CTB treatment with orthodontists rating it higher than UPE. Improvement in maxillary incisal ratio causes an increase in smile aesthetic scores.