UCSF

ABSTRACT

Surgically Assisted Rapid Palatal Expansion vs. Segmental Le Fort I Osteotomy: An Analysis of Transverse Stability Using Cone Beam Computed Tomography

William M. Yao, DDS

OBJECTIVE: To examine the immediate and subsequent skeletal and dental effects of surgical widening of the maxilla via two orthognathic procedures, Segmental Le Fort Osteotomy and Surgically Assisted Rapid Palatal Expansion (SARPE), using cone beam computed tomography (CBCT).

METHODS: A total of thirteen subjects satisfied the inclusion criteria for this study (9 Le Fort and 4 SARPE). Patient ages averaged 28.4 years (range 17.1 - 45.3) in the Le Fort group and 19.2 years (range 17.0 - 23.2) in the SARPE group. Three CBCT scans were taken at time-points defined as follows: Le Fort (T0 = preoperative, T1 = post-operative, T2 = 6+ months postoperative) and SARPE (T0 = preoperative, T1 = post-expansion retention, T2 = 6+ months). Skeletal and dental width measurements were recorded using 3D imaging software, Anatomage In Vivo 5.x (Anatomage, San Jose, CA).

CONCLUSIONS: Surgical expansion of the maxilla in the transverse dimension without performing separation of the pterygomaxillary junction resulted in less than 1 mm of skeletal expansion. During expansion with a multisegmental Le Fort procedure, more expansion occurred skeletally than dentally, with a posterior and anterior ratio of dental:skeletal expansion of 0.70 and 0.58, respectively. During expansion with a SARPE procedure, significantly more expansion occurred dentally than skeletally, with a posterior and anterior ratio of dental:skeletal expansion of 25.19 and 31.80, respectively. In both groups, relapse was more dental than skeletal, with the SARPE group showing a higher ratio of dental:skeletal change. The forces generated by expansion via a Hyrax appliance in a SARPE procedure may cause slight increase in width from T1 to T2 due to changes in the biomechanical system resulting from osteotomy.