Development of a Regression Model to Determine Tooth Size Dimensions from Finger Nail Beds- An Innovative Approach

Abstract

Introduction: Teeth selection is a crucial step and reflects the aesthetic quality of complete dentures and the prime responsibility to ensure their selection with maximum precision lies with the dentist. The anterior teeth reflect the overall aesthetic value of the denture, and hence the need to individualise maxillary anterior teeth was recognised, and the study was undertaken to find an alternative method of teeth selection. Aim: To establish an alternate/additional method of teeth selection for edentulous patients using extraoral landmarks. Materials and Methods: This observational cross-sectional study was conducted in School of Dental Sciences, Krishna Institute of Medical Sciences “Deemed To Be University”, Karad, Maharashtra for a time period of three months (April-June 2015). Dimensions of 402 maxillary central and lateral incisors were measured using a vernier caliper. The superior point selected was the gingival zenith of the teeth and the inferior point was the mid-point of the incisal edge. A line connecting these points determined the teeth length. Similarly, width was determined by marking the midpoint of the proximal surfaces and line connecting them. The points considered for recording the dimensions of the finger nail bed were the mid-points of the mesial and lateral surfaces of the nail bed and mid-points of the superior and inferior edges of the nail bed, respectively. The dimensions of maxillary right central incisor were correlated with the dimensions of right nail bed of index, ring and little finger. Similar procedure was followed for the left central incisor; left and right lateral incisors, respectively. The recorded data were statistically analysed using SPSS version 20 to find out Pearson’s correlation coefficient (r) between dimensions of maxillary incisors and finger nail beds. Further regression equation was derived to determine dimensions of maxillary incisors (dependent variable) from dimensions of nail beds (independent variables) for variables with significant correlations. The p-value less than or equal to 0.05 was taken significant. Results: In males, the central incisor length significantly correlated with little finger nail bed width (p=0.01*). The lateral incisor length had significant correlation with index finger nail bed width (p=0.03*), and little finger nail bed width (p=0.02*). The lateral incisor width had significant correlation with index finger nail bed width (p=0.01*). In females, the lateral incisor width had significant correlation with index finger nail bed width (p=0.01*) and ring finger nail bed length (p=0.002*). Further using the correlations for significant variables, regression formulae were developed. Conclusion: The regression model developed for male and female patients can be used to determine the dimensions of lateral incisor width in females, and central incisor length, lateral incisor length and width in males from the dimensions of index, ring and little fingers. The model stands true as a potential method of teeth selection for edentulous patients.