Effect of Diet Consistency on Rat Mandibular Growth: A Geometric Morphometric and Linear Cephalometric Study

Abstract

Background: Our study intended to investigate the null hypothesis that there is no effect of diet consistency on rat mandibular growth.

Methods: A total sample of 24 female wistar rats, 30 days old, was used in this study. In the first group, the rats were fed soft diet and in the second group, they were fed hard diet for 60 days. On the 60th day, the rats were sedated and lateral cephalometric X-rays were taken. Lateral cephalometric X-rays were digitized with 7 craniofacial landmarks for the linear measurements, as well as with 12 curves and 90 landmarks, of which 74 were semilandmarks and 16 were fixed landmarks for morphometric analysis. These landmarks were exposed to Procrustes superimposition and Principal Component Analysis (PCA) to describe the shape variability of the mandible.

Results: Means measurements of the soft diet group compared to those of the hard diet group were significantly different in linear and morphometric analysis measurements. The soft diet group of wistar rats revealed significant changes on the condyle (smaller), the angle of the mandible, and on the body of the mandible.

Conclusions: Diet consistency affects the craniofacial growth of rats. Soft diet could be responsible for less mandibular growth.

Keywords: growth; hard diet; mandible; soft diet.

Figure 1

Traced X-ray for linear mesasurement. The landmarks we used are the most posterior-superior point on the mandibular condyle (Co), the most posterior point of the angular process of the mandible (Go), the point on the most inferior contour of the angular process of the mandible (Go’), the most posterosuperior point of condylar process (Coronoid), the most inferior and anterior point of the lower border of the mandible (Me), the most inferior and anterior point on the alveolar process of the mandible (Id) and the most anterior edge of the alveolar bone on the convexity of the lower incisor (I’).

Figure 2

Traced lateral X-ray for Geometric morphometric analysis. 12 curves and 90 landmarks, of which 74 were semilandmarks and 16 were fixed landmarks were used for morphometric analysis. The fixed landmarks are the most posterior-superior point on the mandibular condyle (Co), the most posterior point of the angular process of the mandible (Go), the point on the most inferior contour of the angular process of the mandible (Go’), most prominent point between incisal edges of lower incisors (il), most prominent point between incisal edges of upper incisors (iu), most posterior point of lower molars (LMP), most anterior point of lower molars (LMA), the most inferior-anterior point of the lower border of the mandible (Me), the most posterior point of squama occipitalis (Oc), the most superior point of parietal bone (Pa), the internal curvature of the frontal bone (pfs), the point corresponding to anatomic porium (Po), The deepest point of the nasopremaxillary suture (R), the most inferior point of tympanic bone (T), the most posterior edge of the alveolar bone on the convexity of the upper incisors (i) and the most inferior-anterior point on the alveolar process of premaxilla (sd).

Figure 3

Plot of sample and corresponding superimposition of the mean tracings of the two groups. Blue tracing corresponds to soft diet group and red tracing corresponds to hard diet group.