6 I. Morphologic Variation Brunelle JA et al I. Morphologic Variation Brunelle JA et al.: Prevalence and distribution of selected occlusal characteristics in the US Population, , J Dent Res 1996;75:Third National Health and Nutrition Examination Survey (NHANES III)Age: 8-11 & y/on= 11,000Hx of ortho tx: 20%Crowding: Children 48-58% & Adults 57-67%
7 A. Sagittal Plane (Children and Youths) Angle I Normal: 30%Angle I Malocclusion: 55%Angle II Malocclusion: 15%Angle III Malocclusion: 1%
8 B. Horizontal Plane (Transverse) Posterior Crossbite: 9.1%
9 High Mandibular Plane Angle Tall lower faceSmile: maxillary teeth and gingival visibleLips postured to sealAnterior open bite tendency
18 Skeletal Effect:Canine Guidance: tend to have mandibular plane angle < 24oGroup Function: tend to have a mandibular plane angle > 24o(DiPietro GJ: J Prosthet Dent 38: , 1977; n=112)
19 2. Nonworking Side Contacts: Nonworking contacts identified in > 60% of a sample (Ingervall B, Archs Oral Biol 17: , 1977)
20 2. Nonworking Side Contacts: Nonworking interferences (contact only on the nonworking side) identified in 8% of a study sample (Ingervall B, Archs Oral Biol 17: , 1977)
21 C. Intercuspal Position Contacts: Ideal Size: small circular areas≤ 1 mm diameterLocation: cusp tips to flat fossae & marginal ridges; or balanced inclines.Number: n=26 or 66
22 C. IP Contact Biological Variation (Riise C & Ericsson SG: J Oral Rehabil 10:473-480, 1983.) Size: large irregular areasLocation: on cuspal inclinesNumber: average of 2 contacts/ molar, 1 contact/ premolar and <1 contact/ anterior tooth
23 Homo sapiens exhibit greater occlusal variation than any other primate
24 III. Biomechanical System Great population variabilityMasticatory system very adaptable to this variation but exhibits greater adaptive capacity with slow developmental change as compared to rapid change, I.e. restorative dentistry.
25 III. Biomechanical System Restorative Treatment: We as dentists can not control the biological adaptability but we can control mechanical characteristics. Therefore restorations are fabricated to an ideal occlusion within the scope or extent of the treatment.
26 Objectives CR Adjustment: Intercuspal Occlusion Eliminate CR-IP slide, “create new IP in CR”VDO slightly closed from original IP VDOSimultaneous posterior contactAxial loading of posterior teethAnterior lighter contact
27 Occlusal Adjustment: A Method Goal: All centric cusps contacting and every posterior tooth pairholding shimstock.