Evaluation of Hard Tissue, Soft Tissue and Airway Changes Post Twin Block Therapy: An In-vitro Study

Introduction: Aesthetic improvement happens to be one of the main reasons for seeking orthodontic treatment in patients with Angle’s Class II malocclusion. Prognathic maxilla, retrognathic mandible or a combination of both are the main aetiological factors for this malocclusion. Growth modification treatment with different methods can be performed in order to correct skeletal class II malocclusion. Appliance therapy to correct similar malocclusions should immaculately be directed towards addressing the dentoskeletal discord, in order to gain a favourable facial aesthetic result.

Aim: To assess the effects of twin block on mandibular length, soft tissue profile and Oropharyngeal Airway (OAW) dimensions in skeletal class II malocclusion patients.

Materials and Methods: An in-vitro study was carried out in the Department of Paedodontics in collaboration with Department of Orthodontics and Dentofacial Orthopaedics at Sardar Patel Postgraduate Institute of Dental and Medical Sciences, Lucknow, from June 2018 to March 2021. Study was done on lateral cephalograms of 15 growing children with Angle’s Class II Division 1 malocclusion in the age group of 9-12 years, who had undergone functional appliance therapy with twin block appliance. Standardised lateral cephalograms were evaluated at pretreatment (0 month) and postactive phase of twin-block therapy (9-12 months). Selected hard tissue, soft tissue and airway landmarks were marked and traced to evaluate hard tissue, soft tissue and airway changes. The data was analysed using Statistical Package for Social Sciences (SPSS) version 21.0.

Results: There was a statistically significant increase in effective mandibular length (Condyle-Gnathion) and mandibular base length Gonion-Pogonion (Go-Pog) values (p-value <0.001). Significant decrease in the facial convexity Glabella-Soft tissue Nasion (G-Sn) Soft tissue Nasion-Soft tissue Pogonion (Sn-Pog) was observed and airway dimensions showed significant increase after twin block therapy.

Conclusion: Correction of Class II malocclusion by twin block appliance resulted in significant cephalometric changes in the hard tissue profile (increase in mandibular length), together with clinically favourable soft tissue changes and OAW dimensions.