The Effect of Tooth Loss on Craniofacial Morphology

Tooth loss (edentulism) is known to reduce biomechanical loading of the face, resulting in changes in craniofacial morphology and bone material properties. However, the effect of tooth loss on masticatory muscles and their bony attachments is less clear. We hypothesize that the craniofacial shape changes in humans following tooth loss are related to alveolar resorption in both the mandible and maxilla. We also anticipate a recession of bone at the insertion sites of the masticatory muscles, namely the zygomatic arch and mandibular ramus. CT scans (≥70 years) were obtained from the New Mexico Decedent Imaging Database. Edentulous individuals (0 teeth, n=10/sex) were compared to functionally dentate individuals (≥20 teeth, n=10/sex). 3D Slicer software was used to collect 3D fixed and sliding landmarks along the mandible and facial skeleton. A general Procrustes analyses (GPA) and principal components analyses (PCA) were used to compare the morphology of the two populations. Results show significant differences in facial and mandibular shape between the two groups. Between the sexes, shape differences followed similar tends between dentate and edentate individuals. However, the magnitude of these differences varied between the sexes. Variation within edentulous individuals suggests that the time since tooth loss and behavioral factors (e.g. denture wearing) may impact the degree of alveolar resorption. A superior elongation and posterior retraction of the coronoid process was observed in edentulous individuals, suggesting greater relative atrophy of the temporalis muscle relative to the masseter following tooth loss. Future studies will investigate the impact of tooth loss on chewing muscle morphology and force production.