A Three-dimensional Analysis of the Relationship Among Lower Facial Width, Bony Width, and Masseter Muscle Volume in Subjects With Prominent Mandible Angles

Abstract

Despite the fact that a face with a square appearance is determined by surface anatomic features, skin surface parameters and their relationship with inner anatomic features have not been evaluated owing to the challenge of accurately and consistently measuring skin landmarks.We introduce 2 surface distances of the lower face obtained from images of skin and bone thresholds from three-dimensional computed tomographic scans; these were realigned in identical positions using the Frankfurt horizontal plane. The selected parameters were skin surface (LFOP) and bony width (MOP) of the occlusal plane level, skin surface (LFBP) and bony width (MBP) of the bigonial plane level, masseter volume (MV), and soft tissue thickness. Ten subjects with mandible angle flaring and 10 control subjects without flaring were evaluated.The parameters LFOP, LFBP, MBP, and MV showed differences between the study and control groups (P < 0.05). Lower facial width of the occlusal plane was longer than LFBP in both groups (P < 0.005), and MOP was shorter than MBP in the study group (P < 0.005), whereas MOP was greater than MBP in the control group (P < 0.001). Correlation analysis revealed that skin surface width was significantly related to bony width only in the control group (r > 0.6). Masseter volume showed no significant relationship with any skin surface or bony parameter but with soft tissue thickness in the control group (r > 0.6).In conclusion, skin surface widths (LFOP and LFBP) along with MV and bony width differ between patients with flared and nonflared mandibles. Our findings suggest that the skin surface width of the lower face can be used as a valuable landmark.