3D Analysis at Completion of Orthodontics following Class III Surgery

OBJECTIVES: A comparison using 3D cone-beam CT (CBCT) of post-surgical orthodontic treatment phase changes for patients treated by maxillary advancement only or by two jaw osteotomies for correction of Class III malocclusion.

METHODS: CBCTs were obtained pre-surgery, at splint removal 6 weeks post-surgery and at the end of orthodontic treatment (~1 year post-surgery) for 40 patients: 20 patients who received maxillary advancement and mandibular setback (BSSO); and 20 patients maxillary advancement only. Dolphin3D software was used to calculate 13 3D linear and 7 3D angular measurements to describe the transverse, antero-posterior, and vertical changes. General linear models were to analyze the differences between the two surgical procedures, the changes over time, and the interaction between procedure and time. RESULTS: The change over time for the ANB angle differed between the two surgical procedure groups as expected (p<0.02). The antero-posterior, vertical, and transverse changes for the maxilla did not differ between the two groups (p> 0.06). Overall, changes in condylar position as measured by 3D linear and angular measurements were statistically significant regardless of surgical procedure used. However, the pattern of change for medial pole inter-condylar width and inter-ramus width over time was statistically different for the two surgical procedures (p < 0.004 and 0.012 respectively) while the positional transverse changes over time at the lateral pole of the condyles did not differ for the two groups (p > 0.5).

CONCLUSIONS: Adaptive post-surgical changes at the condyles occurred in both surgical groups. The analysis in this study assessed 3D positional changes, but 3D linear and angular measurements cannot assess condylar surface remodeling. Future studies are needed to further investigate condylar remodeling during the post-surgical orthodontic treatment phase.

Support: NIDCR DE017727 and DE005215.