Effect of sagittal position of maxilla and maxillary incisors inclination on the position of the upper lip

Abstract

Introduction: It is paramount to know the effect of change in maxillary incisor position and its correlation to upper lip position since this can affect treatment decision. The soft tissue paradigm also dictates the same emphasising on the position of the soft tissues as the most important determinant of any treatment modality. Hence, the purpose of this study was to determine a correlation, if any, between the skeletal position of maxilla and the upper lip, and inclination of maxillary incisors and the upper lip.

Material and Methods: This was a cross-sectional Comparative study conducted at Margalla College of Dentistry, Margalla Institute of Health Sciences, Rawalpindi. Duration of the study was 6 months. It was carried out on 55 pre orthodontic cephalometric radiographs. Age range was 16-28 years. All types of malocclusion were included in the study however; patients with Craniofacial anomalies were excluded. The Sella -Nasion- point A (SNA) angle, the Upper Incisor-Palatal Plane (UI-PP) angle and the Nasolabial Angle (NLA) were measured. The means and standard deviations were calculated for age, SNA, UI-PP angles and NLA. The Pearson’s correlation coefficient was determined for SNA and NLA and for UI-PP and NLA.

Results: The means and standard deviations for age, SNA, UI-PP and NLA were 20.1±3.07 years, 82.27±2.95^o, 116.87±9.9^o and 100.94±13.96^o respectively (Table 1). The Pearson’s correlation coefficient for SNA angle & NLA was -0.096 (P>0.05) and UI-PP angle & NLA was -0.298 (P<0.01).

Conclusions: The Pearson correlation coefficient between SNA and NLA shows an insignificant weak correlation (r=-0.096, p>0.05) probably due to a number of uncontrolled variables including but not limited to lip thickness, lip tonicity, actual maxillary length and the bony support of alar base. The Pearson correlation coefficient between NLA and UI-PP shows a weak but statistically significant correlation (r=-0.298, p<0.01), probably due to the nasal component of NLA which can act as a confounding factor.