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Why study Diet?. Utility for model building?. Food provides energy necessary to sustain life and allow for reproduction. Main activity of most animals’ lives. Major component of natural selection: “obtain food and keep from becoming food”. Why study teeth?. Utility for model building?.
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Why study Diet? Utility for model building? • Food provides energy necessary to sustain life and allow for reproduction • Main activity of most animals’ lives • Major component of natural selection: “obtain food and keep from becoming food”
Why study teeth? Utility for model building? • Indicate foods consumed • Indicate size & behavior • Well preserved in the fossil record • Growth & development patterns • Sexual dimorphism characteristics • Non-dietary indicators
Tooth Types Human Dentition
Roles of the teeth Differential use in heterodont dentition Incisors & canines -- • ingestion, get the food into the mouth • seizing, stripping, squashing, puncturing Premolars & molars -- • preparation of food for digestion • food is chopped up to increase surface area • molars are a series of cutting blades and crushing basin
Extant vs Extinct Data collection from the living primates
Diagnostic features Features of the skull used to determine dietary category • Incisors & canines • Molars & premolars • Cusps & crests • Enamel thickness • Massiter & temporalis muscles • Body size
Large incisors indicate • frugivore • Small incisors = carnivore • or insectivore Incisors & Canines Anterior Dentition • Get food in the mouth • Grooming • Scraping • ~~~~~~~~~~~~~~~~~~~~
Premolars & Molars Posterior Dentition • Folivores = low or high • Insectivores = tall, pointed • Carnivores = tall, pointed • Frugivores = low, rounded • Omnivore = low, rounded
Premolars & Molars Premolars& Molars
Cusps & Crests Molar & premolar morphology cusp crest
Enamel thickness Thickness of the hard mineral surface covering the teeth
Dental Attrition Enamel wear
Body size Diet dictates primate body size • Body-size tends to • correlate w/ dietary • regime • Folivore = largest • Insectivore = smallest • Frugivore = medium to large
Dietary strategies Categories of Diet for the Primates • Folivore - plants • Frugivore - fruit • Carnivore - meat • Insectivore - insects • Omnivore - mixed
Age Changes Subadult Dentition
temporalis massiter 1. Temporal bone 2. Mandibular condyle Human Chewing Anatomy of the TMJ
Human Chewing Movement of the TMJ • held in place by a sheath of tendon and muscles • glides on cartilage • Bursa helps absorb some forces • Literal double joint
Human Chewing Motions of the Mandible …but subject to very complex movements and forces.
Human Chewing “Disarticulation” of the TMJ
Human Chewing Nerves & Blood Vessels around TMJ
Human Chewing Disorders of the TMJ & Associated Structures Fibro-Osseous Disorders Fibrous dysplasia Paget’s disease Luxation & Subluxation Developmental Condylar Hyperplasia Hyperplasia Agensis Infectious Spread Tuberculosis Syphillis Gonorrhea Staphylococcal Infection Streptococcal Infection Inflammatory rheumatoid arthritis Psoriatic arthritis Reiter’s syndrome Systemic lupus erthematosis Familial Mediterranean fever Degenerative osteoporosis Traumatic Condylar Fracture Ankylosis Internal rearrangement Metabolic Gout Pseudogout TMJ Pain Dysfunction Neoplastic Benign Tumors
Human Chewing Clinical Aspects • Burt Reynolds • “In” malady • drew attention to the extent of the disorder
Human Chewing Treatments
Human Chewing Measuring Mandibular Angle
Human Chewing Molar & Incisal Chewing
Human Chewing Hylander’s Lever Action Model • Trouble w/TMJ: • Chew on the same side as pain • Trouble w/molar: • Chew on the opposite side
Human Chewing condyle pathology
Human Chewing Categories Studied • Age • Sex • Complete Socket Resorption • Active Pathologies • Dental Attrition
Human Chewing Age Changes in the Mandible Lateral View Dorsal View
TMJ PATHOLOGY - + AGE 34.47 35.12 male 26.40 47.60 SEX female 70.60 52.40 Human Chewing Age & Sex Relationships
Human Chewing Complete Socket Resorption
Human Chewing Complete Socket Resorption
abcess caries partial socket resorption
TMJ PATHOLOGY + - ABCESS 0.24 0.79 CARIES 0.71 1.39 2.27 2.88 PARTIAL RESORPTION Human Chewing Dental Caries & Abcesses
Human Chewing Dental Attrition tooth wear
Human Chewing Results • Significantly more females affected compared to males • Greater wear found on the same side as TMJ damage • Greater wear found on side opposite carious lesions • Trends similar to clinical findings