Pre-treatment predictors for Non-extraction and first premolars extraction after Clark’s twin-block appliance therapy in class ii subjects–a retrospective cohort study

Objective: Determining whether to proceed with premolar extraction (PME) or non-extraction (NE) after Clark’s twin-block (CTB) appliance therapy remains a critical challenge in orthodontic treatment planning. The aim of the study was to identify the pre-treatment factors associated with the likelihood of PME versus NE following completion of CTB therapy in growing patients with skeletal Class II malocclusion. Materials and methods: After obtaining exemption from the ethical review committee (ERC), 52 orthodontic patients treated with CTB appliance were retrospectively analysed. Pre-treatment lateral cephalograms were used to assess skeletal, dental, and soft tissue parameters. Logistic regression analysis was executed to identify the factors that determine the need for PME and NE after CTB appliance therapy. Results: Several pre-treatment cephalometric variables demonstrated significant associations with PME in patients with skeletal Class II malocclusion treated with CTB appliance therapy (p-value ≤ 0.05). Patients with an increased ANB angle and GoGn-SN plane angle, while decreased interincisal angle were more likely to require PME following CTB appliance therapy. In multivariable analysis, interincisal angle demonstrated the strongest independent association with PME. Additionally, patients with a Class II molar relationship (OR = 3.4) were more likely to undergo PME, although this was not statistically significant. Conclusions: The cephalometric variables ANB angle, GoGn-SN plane angle, and interincisal angle were associated with PME following CTB therapy; however, interincisal angle demonstrated the strongest independent association. Soft tissue parameters may assist in refining extraction decisions, whereas occlusal variables were not significantly associated in this cohort.