Nasolabial Angle Modifications Following Maxillary Surgery

Abstract

The nasolabial angle is the angle formed by a line tangent to the upper lip and a line tangent to the columella. A value of 90 to 120 degrees is considered normal in adults.1 The nasolabial angle is determined by several factors including the anteroposterior position of the maxilla, the anteroposterior position of the maxillary incisors, the vertical position or rotation of the nasal tip, which can result in a more obtuse or acute nasolabial angle, and by the soft tissue thickness of the maxillary lip that contributes to the nasolabial angle. A thin upper lip favors a flatter angle, while a thicker upper lip favors an acute angle.2 Therefore this angle is a common parameter that is considered when treatment planning for maxillary surgery. While there is a general consensus within the literature on these values, there appears to be inconsistencies in describing changes to the nasolabial angle that occur following maxillary surgery. Previous reports have described changes as acute, more acute, more obtuse, less obtuse, open vs. closed, leading to confusion among the readers in determining if the angle actually increases or decreases in size.3,4 This study aims to evaluate the changes to this angle that occur following maxillary surgery, including whether the angle decreases or increases and clarify the terminology that is used to describe the changes found. This retrospective chart review evaluated twenty patients who underwent maxillary surgery for correction of dentofacial abnormalities from July 2009 to December 2013 at the Department of Oral and Maxillofacial Surgery, University of Florida Health Science Center, Jacksonville, Florida. Lateral cephalograms and lateral profile photographs taken in the pre and post-operative period for each patient were obtained for analysis and processed using Dolphin Imaging Software. Analysis of these films included measurement of the amount of anteroposterior movement of the maxilla and measurement of nasolabial angle changes following maxillary surgery. Subjective analysis has shown that the nasolabial angle increases in the majority of subjects evaluated at our institution. These increases in the nasolabial angle were also found to correlate with the amount of anteroposterior advancement of the maxilla.By clarifying the terminology, it allows for a consistent method of defining post-operative changes to the nasolabial angle and avoids confusion among practitioners when communicating treatment plans with one another.