Browsing by Subject "geometric morphometrics"
Item Nasal Septal Deviation and Nasofacial Skeletal Form: A Cross-Sectional CBCT Study of a 7-18 Year-Old Cohort(2016-10) Goergen, MatthewObjective: The objective of this study was to examine the relationship between nasal septal deviation and the shape of the nasofacial skeleton during ontogeny. Materials and Methods: Nasal septal size was retrospectively measured on existing cone-beam computed tomograms (CBCT) in 66 mixed-sex orthodontic patients of European ancestry aged 7-18 years. First, the septum was manually segmented using CBCT reconstructions and the volume of the structure calculated. Next, a midsagittal volume that followed the borders of the septum was constructed as a model for a non-deviated septum. Nasal septal deviation was then calculated for each individual. Nasofacial skeletal form was quantified using a series of coordinate landmarks of the facial skeleton in the nasal region and the cranial base. Using geometric morphometric techniques, size and shape information was distilled from the landmark data. Multivariate regression analyses were used to assess the interactions between the septum and the nasofacial skeleton. Results: There was no significant correlation between nasal septal deviation and age or nasofacial size. Nasofacial shape changes correlated with septal deviation followed a different pattern than allometric shape changes. In individuals with a deviated septum, the sphenoid body was anteriorly positioned, reducing the size of the nasofacial skeleton. This pattern of morphological variation was independent of the stage of development. Conclusion: Normal developmental changes in nasal cavity and cranial base form are not related to an increase in nasal septum deviation. Rather, a nasofacial skeletal configuration with anterior displacement of the sphenoid may place spatial constraints on the growth of the septum, resulting in deviation.Item Understanding Primate Mandibular Symphyseal Fusion: Function, Integration, And Ontogeny(2017-12) Knigge, RyanUnderstanding the function-shape relationships of the primate masticatory apparatus has been a focus of anthropological research for many decades. One particular feature of the masticatory apparatus, mandibular symphyseal fusion, is investigated in this work because symphyseal fusion has the potential to provide important information on masticatory function and mandibular fragments are often preserved in the fossil record. Regardless of the attention this anatomical feature has received, a complete understanding of the underlying mechanisms driving the evolution of symphyseal fusion remains elusive. The research presented in this dissertation tackles this dilemma by investigating the functional, integrative, and ontogenetic elements of symphyseal fusion. Function and morphology are linked through innovative approaches using the burgeoning geometric morphometric toolkit to challenge previously held notions about mandibular symphyseal fusion and generate new hypotheses. Ultimately, this work acknowledges similar underlying mechanisms for symphyseal fusion in different primate lineages which were previously thought to be different, questions the utility of symphyseal fusion for reconstructing evolutionary relationships of primates, and finds potential evidence for the independent evolution of symphyseal fusion within the crown anthropoid clade.