Comparative Evaluation of Soft Tissue Chin Thickness in Adult Patients with Skeletal Class II Malocclusion with Various Vertical Growth Patterns: a Cephalometric Study

Abstract

Introduction: Facial soft tissue thickness is important not only for plastic surgeons but also for orthodontists to plan the treatment procedure. Genioplasty, an orthognathic surgery in combination with orthodontic treatment is indicated to restore adequate shape and projection of the chin in the face. It has been performed to enhance soft tissue contours related to disproportion between soft and hard tissue. These treatments require the critical information regarding the relation between soft and hard tissues for proper treatment plan-ning. However, there is very minimal documentation on comparison of soft tissue characteristics particularly in Class II malocclusion.  Aim: To evaluate and compare soft tissue chin thickness in class II subjects with various growth patterns. To evaluate soft tissue chin thickness difference in males and females and compare the results with previous studies.  Materials and methods: The study comprised 150 adults aged between 18 and 26 years (mean age 21 years). Based on FH/MP angle the study sample was allocated into three groups: group I - low (hypodivergent), group II – average, and group III - high (hyper-divergent). Radiographs were traced manually. Angular measurements were computed to determine the vertical position of the maxilla and mandible in relation to anterior cranial base, to true horizontal and to each other. Soft tissue chin thickness was measured at three different levels.  Results: Hyperdivergent group showed greater soft tissue chin thickness at Pog-Pog’ than the hypodivergent and average angle groups. Hypodivergent group showed greater soft tissue chin thickness at Me-Me’ and Gn-Gn’ as compared to average and hyperdivergent groups. Males showed greater soft tissue chin thickness at hypodivergent, average and hyperdivergent group than females.  Conclusions: Soft tissue thickness measurements were smaller in adult patients of hyperdivergent group compared to adult patients in clinically average and hypodivergent groups. All STC measurements were greater in men than in women. The findings suggested that STC thickness in hyperdivergent pattern should be considered differently at its most anterior point (Pog) relative to its inferior landmarks (Gn and Me).