Residents' journal review

Abstract

The position of the lower incisors to the underlying mandibular symphysis should be maintained in a healthy relationship throughout orthodontic treatment. The aim of the current study was to analyze and determine if there is a statistically significant correlation between facial growth pattern, Holdaway ratio, symphyseal morphology, and lower incisor position, as well as validate a previous analysis performed by Aki et al. A sample of 100 white adult patients was randomly selected from the University of Seville in Spain. Manual measurements were made from the pre-treatment cephalograms at four different time points by two separate operators. The operators assessed symphyseal height/width (H/A) ratio using the Aki analysis, symphyseal morphology (constructed by point B–menton line and the mandibular plane), and facial growth pattern (determined using the Jarabak-MSE analysis retro-occlusion variable). Facial growth pattern, the Holdaway ratio, and H/A were found to be statistically significant (P < 0.05). The study concluded that anterior mandibular bone support and lower incisor position differs among patients, and that symphyseal morphology is related to both facial growth pattern and lower incisor inclination. Dolichofacial patterns trend towards a narrower symphysis, while broader symphyses are indicative of brachyfacial patterns. These facial patterns can then be further related to lower incisor position using the Holdaway ratio and symphyseal H/A ratio, which showed that larger degrees of lower incisor proclination are associated with dolichofacial patterns and a narrow symphysis, and more upright lower incisors are associated with brachyfacial patterns and a wider symphysis. Therefore, orthodontists must understand the limitations on lower incisor movements depending on each patient's symphyseal morphology and facial growth pattern.