Date of Award

Spring 2001

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)



First Advisor

Bradley, Thomas

Second Advisor

Iacopino, Anthony

Third Advisor

Stier, Erwin


Asymmetry of the human mandible is well-documented. Although both genetic and environmental factors have been identified, little evidence exists to describe how the absence of teeth contributes to asymmetry. Some authors report these asymmetries as having a sidedness, where as, others have found asymmetry to be random in nature. Van Valen proposed a hypothesis that observed asymmetry is a case of "fluctuating asymmetry' in which either the right or left side can be larger. Another hypothesis describes mechanical activity of the jaw to be the impetus in developing asymmetries by translating forces to the craniofacial complex during mastication and other activity. The latter hypothesis has been thought to contribute to continuous remodeling of the mandible. This continuous remodeling has been demonstrated not only in the mandible but also the temporomandibular joint (TMJ). Bjork demonstrated how loss of teeth increased the bony attachments of the lateral pterygoid muscle on the condyle and condylar neck. He proposed the increased muscle tension was needed to keep the condyle in the condylar fossa since no teeth were available to contribute. It is thought that increased activity of the lateral pterygoids is associated with temporomanclibular joint dysfunction (TMD). An increased horizontal condylar angle has also been associated with TMD. A logical progression is that an increased condylar angle might be related to increased lateral pterygoid activity, and hence, tooth loss might cause an increased condylar angle. The purpose of this study is to evaluate a cause and effect relationship of the number of teeth in the mandible to mandibular asymmetry and also to study the relationship of condylar angle to tooth loss and other mandibular anatomical structures in a specific racial population.



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