EFFECT OF FIRST PREMOLAR EXTRACTION ON MANDIBULAR THIRD MOLAR ANGULATION IN ORTHODONTICALLY TREATED BIMAXILLARY PROTRUSION CASES: A RETROSPECTIVE CEPHALOMETRIC STUDY

Abstract

Context: Mandibular third molars are prone to impaction given their late eruption chronology and limited retromolar space. Whether orthodontic extraction of first premolars favourably influences third molar angulation in bimaxillary protrusion patients remains debated, making objective cephalometric evaluation clinically important.

Aims: To assess angular changes of the mandibular third molar following fixed orthodontic treatment with versus without first premolar extraction in patients presenting with bimaxillary dentoalveolar protrusion.

Settings and Design: Retrospective observational study conducted at the Department of Orthodontics and Dentofacial Orthopaedics, Inderprastha Dental College and Hospital, Sahibabad, Ghaziabad.

Materials and Methods: Pretreatment (T1) and posttreatment (T2) lateral cephalograms of 34 patients (mean age 18–35 years) with bimaxillary protrusion were analysed. Group A (n = 17) underwent all four first premolar extractions combined with fixed MBT appliance therapy; Group B (n = 17) received non-extraction fixed orthodontic treatment. Four angular variables were measured: mandibular third molar long axis relative to the sella–nasion (SN) plane, occlusal plane (OP), mandibular plane (MP), and mandibular second molar (M2).

Statistical Analysis Used: Intragroup pretreatment-to-posttreatment differences were evaluated using paired t-tests. Intergroup comparisons of mean angular changes employed independent-samples analysis with F-statistics. The significance threshold was set at P ≤ 0.05 (95% confidence interval).

Results: Neither group showed statistically significant intragroup angular changes (P > 0.05), yet directional trends consistently favoured uprighting in Group A. Intergroup comparison revealed significantly greater and more favourable angular improvements in Group A for all four variables: M3–SN (F = 14.101; P = 0.001), M3–OP (F = 83.849; P < 0.001), M3–M2 (F = 97.263; P < 0.001), and M3–MP (F = 74.739; P < 0.001).

Conclusions: First premolar extraction in bimaxillary protrusion cases produces significantly more favourable mandibular third molar angular changes than non-extraction therapy, suggesting a potential reduction in impaction risk and improved long-term orthodontic stability.