Treatment effects and lip profile changes following premolars extraction treatment vs fixed functional treatment in Class II division 1 malocclusion: A randomized controlled clinical trial.

Objective: The objective of this two-arm parallel randomized controlled trial was to evaluate the treatment effects and lip profile changes in skeletal Class II patients subjected to premolars extraction treatment versus fixed functional treatment.

Methods: Forty six subjects fulfilling inclusion criteria were randomly distributed into Group PE (mean age 13.03±1.78 years) and Group FF (mean age 12.80±1.67 years) (n=23 each). Group PE was managed by therapeutic extraction of maxillary first premolars and mandibular second premolars, followed by mini-implant-supported space closure; and Group FF, by fixed functional appliance therapy. Skeletal, dental, and soft-tissue changes were analyzed using pre and post-treatment lateral cephalograms. Data obtained from this open label study was subjected to blind statistical analysis.

Results: Extraction treatment resulted in greater increase of nasolabial angle (NLA: 3.1 [95% CI 2.08, 4.19], p<0.001), significant improvement of upper lip (UL-E line: -2.91 [95% CI -3.54, -2.28], p<0.001, UL-S line: -2.50 [95% CI -2.76, -2.24], p<0.001, UL-SnPog': -2.32 [95% CI -2.90, -1.74], p<0.01) and lower lip position (LL-E line: -0.68 [95% CI -1.36, 0.00], p<0.01, LL-S line: -0.55 [95% CI -1.11, 0.02], p<0.01, and LL-SnPog': -0.64 [95% CI -1.20, -0.07], p<0.01), lip thickness (UL thickness: 2.27 [95% CI 1.79, 2.75], p<0.001; LL thickness: 0.41 [95% CI -0.16, 0.97], p<0.01), upper lip strain (UL strain: -2.68 [95% CI -3.32, -2.04], p<0.001) and soft tissue profile (N'-Sn-Pog': 2.68 [95% CI 1.87, 3.50], p<0.01). No significant difference was observed between the groups regarding skeletal changes in the maxilla and mandible, growth pattern, overjet, overbite, interincisal angle and soft tissue chin position (p>0.05). Premolar extraction treatment demonstrated significant intrusion-retraction of maxillary incisors, better maintenance of maxillary incisor inclination, and significant mandibular molar protraction; whereas functional treatment resulted in retrusive and intrusive effect on maxillary molars, marked proclination of mandibular anterior teeth, and significant extrusion of mandibular molars. Both treatment modalities had similar treatment duration. Implant failure was seen in 7.9% of cases, whereas failure of fixed functional appliance was observed in 9.09% of cases.

Conclusions: Premolar extraction therapy is a better treatment modality, compared to fixed functional appliance therapy for Class II patients with moderate skeletal discrepancy, increased overjet, protruded maxillary incisors and protruded lips, as it produces better dentoalveolar response and permits greater improvement of the soft tissue profile and lip relationship.