Effects of CBCT measurement of mandibular advancement on craniofacial morphology and natural head posture

Objective To assess the changes and correlation of craniofacial morphology, natural head posture after mandibula Bilateral Sagittal Split Osteotomy (BSSO) advancement. Methods In this retrospective study, we reviewed the CBCT scans of twenty five eligible patients with Angle’s Class Ⅱ developmental osseous malocclusion who had undergone mandibular advancemen procedure in craniofacial center, department of surgery, University of Illinois from March 2008 to March 2015. There were 4 males and 21 females with average age of (17.95±1.43) years, and they were divided into three study groups, including group A (single jaw mandibular BSSO advancement), group B (maxillary Le Fort I and mandibular BSSO advancement) and group C (maxillary Le For I and mandibular BSSO advancement with osseous genioplasty as a component). The radiographic time points at T1 (1-2 month prio to surgery), T2 (1.5 month to 3 month after surgery) and T3 (1-2 years after surgery) were used to evaluate the short-term and the long term changes. The data were analyzed via 3D anthropometric aspects in commercially available DICOM readers and the correlation of the morphological changes and NHP were statistically analyzed by Spearman analysis. Results There were significant differencesin craniofacial morphology at three different time points (T1, T2, T3), including NSPNS (P＜ 0.001), NSL (P=0.015), L-S_CP (P＜ 0.001), and L-S_CP (P=0.018), CSP-S_CP (P=0.03) was affected interactively among surgery groups. Meanwhile, the correlations of craniofacial morphology and NHP showed significant differences at three different time points (T1, T2, T3), including L-CIP (P=0.005), PNS-CSP (P＜ 0.001). NSC2 was positively associated with NSL in T1 (r=0.487, P=0.014), T2 (r=0.576, P=0.003), T3 (r=0.675, P＜ 0.001) phases. Conclusion Mandibular BSSO advancement impacts the craniofacial morphology, by permanently altering the patient’s natural head posture. This implies that the optimal way to observe the changes of craniofacial morphology is to superimpose the cranial base in 3D, which, to some extent, can contribute to better judgment and evaluation of craniofacial morphology changes.