Dr. Dao Quang Huy, DDS

Extraction Treatment of Severe Bimaxillary Incisor Protrusion in a High-Angle Class II Patient: Three-Dimensional Torque Control Using ART and Ricketts Bioprogressive Mechanics

Bimaxillary incisor protrusion is one of the most common conditions affecting facial esthetics in adolescent patients, particularly when associated with lip protrusion, mentalis muscle strain, and a convex facial profile [1,2]. In many cases, extraction-based orthodontic treatment is indicated to reduce incisor protrusion and improve the soft tissue profile. However, in patients with a vertical growth pattern (high-angle pattern), space closure following extractions is often more challenging due to an increased risk of anterior tooth extrusion, clockwise mandibular rotation, reduced occlusal stability, and difficulty in controlling the soft tissue profile [3–5]. From a biomechanical perspective, in the majority of extraction cases, the space-closing force is applied below the center of resistance of the anterior segment, thereby generating unfavorable moments, particularly negative torque. Consequently, the crowns tend to tip posteriorly while the roots are displaced anteriorly and labially, increasing the risk of labial cortical bone contact or periodontal complications such as fenestration and dehiscence, especially in the mandibular incisor region [6–9]. This risk is further exacerbated when the mandibular incisor roots are initially positioned close to the labial cortical plate, significantly narrowing the biological envelope available for lingual tooth movement [10–12].