S12-04 SESSION 12: FACIOCRANIOSYNOSTOSIS – PART II INFLUENCE OF MONOBLOC/LEFORT III DISTRACTION ON THE DEVELOPING POSTERIOR MAXILLARY DENTITION AND ITS RESULTANT EFFECT ON ORTHOGNATHIC SURGERY.

Abstract

Introduction: Patients with syndromic craniosynostosis often undergo midface advancements with distraction, such as a Lefort III or Monobloc, while posterior maxillary dental formation is ongoing which may indirectly damage developing tooth buds. The purpose of this study is to evaluate the dental development of the posterior maxilla after monobloc or lefort III and its clinical implications on orthognathic surgery. Methods: We evaluated the medical records and imaging (CT +/- Panorex) of all syndromic craniosynostosis patients treated at our institution from 1999–2018. Those patients without at least 1 year follow-up, incomplete medical records, or incomplete imaging were excluded from the study. Those patients who also underwent orthognathic surgery between 2014–2018 were also reviewed. Statistical comparisons of demographic, procedural, dental status and imaging data were performed. Results: 90 patients underwent midface advancement during the study period and 32 met the inclusion criteria. Average age of surgery was 7.2years. 65% (21/32) had radiographic evidence of posterior maxillary dental pathology. Increased age at time of surgery was significantly correlated with a decreased risk of dental injury (p=0.034, OR=0.55) (see attached graph). Damage to either second or third maxillary molar was significantly associated with a younger age at time of surgery (p=0.021 and p=0.034), and surgery at age seven and above trended towards being protective of the posterior maxillary dentition (Fischer exact p=0.074). There was no significant age relationship with time of surgery and injury to the first molar (p=0.173). 5 patients, average age of 17 years old, who had a previous monobloc/lefort III distraction underwent orthognathic surgery between 2014–2018. All needed adjunctive oral surgery procedures involving posterior maxillary teeth (extractions, dental exposure, anchorage of maxillary molars), and all have at least one quadrant with only first molar or no molar occlusion. Pre-orthognathic surgery orthodontics averaged 38.6 months. Conclusion: Monobloc and Lefort 3 distraction for syndromic craniofacial patients has obvious functional benefits. Early intervention is significantly associated with injury to the growing posterior maxillary dentition, and waiting until at least age 7 trends towards being protective. Damage to developing permanent maxillary molars may affect timing of orthodontic management and treatment planning for orthognathic surgery.