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Introduction to Occlusion Occlusion 6800 & 6804 Course Introduction and Characteristics of an Ideal Occlusion Course Textbook & References ► Textbook: Management of Temporomandibular Disorders and Occlusion; Jeffrey P. Okeson. 5th Edition ► Secondary Reference: Course Manual ► Main Reference: PowerPoint Files Exam Format and Use of References: All examination questions will be obtained from the PowerPoint files that all students have access to. Textbook reading is secondary, but still somewhat essential to the understanding of the material. Exam questions are multiple choice format (40 for mid- term and 50 for final examination). Occlusion 6800 & 6804 Course Schedules Introduction to Occlusion Occlusion 6800 & 6804 - Evaluation Lecture & Lab Quizzes Occlusion 6800 & 6804 – Course Descriptions Moving Occlusion Diagrams Practical Examination: You will be given a flash card booklet with quadrant diagrams displaying various mandibular movements. This booklet will be the entire basis of the moving occlusion practical examination. The National Board has about 3 or 4 of these questions on the exam every year. Interferences and Muscle Actions Practical Examination: It is important for the student to know the location of various mandibular- maxillary tooth interferences and which muscles are involved as a result of these types of interferences. All of the questions for this practical examination will be taken from the PowerPoint exercise. D-1 Occlusion Download Site: http://www.carcoria.com/bcd-d1-occ-2012/d1occlusion-2012.htm Constant Communication from me to you. Updated at least once each week. Right click on your mouse and save the files to your drive **Note: this is a different web-site than the Dental Anatomy Course Introduction to Occlusion Criteria for Optimum Functional Occlusion Key Anatomical Landmarks: Temporal Bone: a portion of this bone forms the glenoid or mandibular fossa. The shape of this fossa determines many of the limits of mandibular movement Mandible: a moveable structure which is suspended by musculature and whose movement is limited by ligaments. Condyle: the portion of the mandible that articulates in the mandibular fossa. There is a right and left condyle, about which movement of the mandible occurs. The shape of the heads of the condyles determine many of the limits of mandibular movement. The mandible is the only bone in the human body that possesses two axes of rotation. Dentition: the size, shape and alignment of the teeth determine many of the limits of mandibular movements. The role of the dentition is considered to be secondary to the role of muscles, ligaments and the bony structures which comprise the temporomandibular joint. Basic Structure of the TMJ Two TMJ: When one moves, the other must move as well. Basic Structure of the TMJ Glenoid or mandibular fossa Articular Movement is characterized by position of condyle in glenoid fossa eminence Basic Structures of the Temporomandibular Joint Articular Disc Condyle >Mandibular/Glenoid Fossa >Articular eminence: 1) Posterior slope, 2) Steepness/flatness guides movement >Synovial cavities: 1) Joint lubrication, 2) boundary lubrication from motion Ligaments Supporting the TMJ and the Mandible •Limit movement •Protect muscles •Non-elastic Medial Side of Mandible (inside) Lateral Side of Mandible (outside) The Temporomandibular Joint Basic Structures Condyle Anatomic variations guide mandibular movement ► Retrodiscal tissue elasticity Highly innervated and vascular Loading is painful Trauma can cause inflammation The Temporomandibular Disc ► Fibrous connective tissue ► Interface between bones, somewhat pliable ► Bi-concave shape ► Collateral ligaments ► No Innervation ► No Vascularization Terminology Related to Mandibular Position and Tooth Position Basic Premises: ► When the mandible closes against the maxilla: 1. There is an ideal way for the teeth to contact 2. There is an ideal place for the condyle and disc to be situated. Our task is to accomplish these two criteria in as non-obtrusive fashion as possible Terminology Describing Tooth Position: MAXIMUM INTERCUSPATION ► a.k.a. centric occlusion (CO) ► Habitual occlusion, habitual centric ► Maximum intercuspation describes an occlusal relationship ► Teeth are contacting in a position that the patient finds the most comfortable ► Easily achievable, but not always reproducible, by the patient MAXIMUM INTERCUSPATION What is considered Ideal? Angle Class I: 1st Molars and Canines relationship Adequate Overlap Long axis of teeth Simultaneous contact ► Posterior tooth dominance ► Anterior tooth “passive” contact ► Multiple contacts on all teeth adequately distributes forces Term Describing Mandibular Position CENTRIC RELATION ► Centric Relation A condylar position Superior and Anterior Thin portion of disc Describes the most stable position of the condyle Superior and anterior position of the mandible with the disc properly interposed Terms Describing Mandibular Position ► Centric Relation Why a superior and anterior position? The Muscles of Mastication drive this process In an Ideal Occlusion, CR and MI Occur Simultaneously. Maximum Intercuspation ► An occlusal position ► If CR and MI do not coincide, the patient will have a “slide” ► Most patients have some degree of a slide into maximum intercuspation (approximately 1-2 mm) ► MI is simultaneous contact ► Forces concentrated on long axis ► Posterior contacts should dominate Slide from CR to MI ► Only 15% of the population have no CR to MI discrepancy ► After the first contact in CR (usually on 2 or more posterior teeth), the patient continues to close, and the teeth come together more completely (MI). The condyles must move out of their most ideal position when the teeth come fully together. An ideal occlusion… Basic Premises: ► When the mandible closes, 1. There is an ideal way for the teeth to contact 2. There is an ideal place for the condyle and disc to be situated. Characteristics of an Ideal Occlusion The condyle seats in CR simultaneous with the teeth occluding in MI. No slide occurs. Terms for Describing Eccentric Movements of the Mandible ► Protrusive - anterior movement of the mandible ► Retrusive - posterior movement of the mandible ► Eccentric - movement Protrusive away from a centric position (CR or MI) Terms for Describing Eccentric Movements of the Mandible In an ideal occlusion, protrusive movement is guided by anterior teeth. Early lateral movements are ideally canine-guided. Terms for Describing Eccentric Movements of the Mandible Lateral movements- moving the mandible to the left or to the right. Shown is a “left lateral movement” Terms for Describing Eccentric Movements of the Mandible Lateral movements- During a left lateral movement, the left side of the arch is considered to be the “working side”. Shown is a “left lateral movement” Terms for Describing Eccentric Movements of the Mandible Lateral movements- During a left lateral movement, the right side is considered to be the “balancing side” or ”non- working” side. Shown is a “left lateral movement” Terms for Describing Eccentric Movements of the Mandible Lateral movements are guided by either: canine guidance (ideal) group function (secondary choice) Terms for Describing Eccentric Movements of the Mandible Crossover is an extreme movement where the mandibular canine “crosses over” the maxillary canine. • This position is outside the envelope of function •It is critical to the success of anterior restorations. Extended lateral movements should smoothly transfer from the canines to the incisors Summary of Characteristics of an Ideal Occlusion ► CR and MI occur simultaneously ► All teeth contact simultaneously ► All occlusal forces are longitudinal ► Posterior tooth contacts dominate ► Eccentric movements are anterior- guided ► No cross-over contacts on posterior teeth Summary of Criteria for an Optimal Functional Occlusion ► Condylar position- Centric relation ► Tooth position- Maximum intercuspation ► Protrusive movements are guided by anterior teeth ► Lateral movements are canine guided. ► Axial loading of occlusal forces ► In MI, posterior tooth contacts dominate. ► During crossover, guidance is smoothly transferred to the incisors.
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