1️⃣ Indications
- Skeletal anterior open bite (AOB) with:
- Normal maxilla (no vertical maxillary excess)
- Short mandibular ramus with normal condyles
- Class II pattern requiring mandibular advancement
- Retrogenia (benefits from chin prominence with mandibular rotation)
- Patients unsuitable for or wishing to avoid bimaxillary surgery
2️⃣ Contraindications / Exclusions
- Thumb sucking or other parafunctional habits
- Macroglossia or tongue thrust contributing to AOB
- Active TMJ disorders or condylar resorption
3️⃣ Surgical Technique Highlights
- Approach: Bilateral sagittal split osteotomy (Obwegeser–Dal Pont/Hunsuck modification)
- Movement: Anticlockwise rotation of mandible to close AOB
- Fixation:
- Rigid internal fixation — 3 × 2.0 mm bicortical positional screws per side (preferred)
- Rigid fixation > wire > miniplates for stability
- Adjuncts: Extraction of third molars if required
4️⃣ Post-operative Findings
| Time point | Mean Incisal Relationship |
|---|---|
| Immediate | Class I overbite 1–2 mm |
| 1–2 weeks | Stable (1–2 mm) |
| 12 months | 10/12 stable Class I; 2 edge-to-edge; no AOB relapse |
- Slight relapse (≈ 1 mm) in high-angle cases (> 43° max-mand angle).
- No condylar resorption reported.
5️⃣ Clinical Pearls
- Rigid fixation minimizes relapse.
- “Short split” modification → partial attachment of medial pterygoid → reduces relapse forces.
- Avoids morbidity of Le Fort I and bimaxillary procedures.
- Aesthetic gain: enhances chin prominence, may eliminate need for genioplasty.
- Best suited for selected cases — not all open bites.
6️⃣ Summary Recommendation
In carefully selected Class II AOB cases with normal maxilla and retrogenia,
mandibular anticlockwise rotation via MSSO offers stability comparable to maxillary impaction,
with reduced surgical morbidity.
Dentowesome 