Winter Week 3 Dentd 1532 2024 Occlusion PDF

STATIC OCCLUSION 1 REST POSITION and INTERMAXILLARY RELATIONS Jeffrey Wascher DDS  PART 1 OCCLUSION (Winter) 1. STATIC OCCLUSION I. REST POSITION AND INTER...

STATIC OCCLUSION 1 REST POSITION and INTERMAXILLARY RELATIONS Jeffrey Wascher DDS  PART 1 OCCLUSION (Winter) 1. STATIC OCCLUSION I. REST POSITION AND INTERMAXILLARY RELATIONS 2. STATIC OCCLUSION II. OCCLUSAL CONTACTS 3. DYNAMIC OCCLUSION I.MASTICATORY CYCLE & ENVELOPE OF FUNCTION 4. DYNAMIC OCCLUSION II. MANDIBULAR MOVEMENTS. 5. OCCLUSION REVIEW PART 2 (Spring) 1. OCCLUSIAL CONTACTS AND MANDIBULAR MOVEMENTS. CLINICAL CONSIDERATIONS 2. OCCLUSION REVIEW FOR FINAL  Learning Objectives 1. Differentiate between axial forces and shear forces 2. Differentiate different types of levers 3. Define centric relation 4. Define maximum intercuspation 5. Differentiate centric relation versus maximum intercuspation and rest position 6. Define vertical dimension 7. Explain the occlusal scheme most widely used in restorative dentistry 8. Classify Angle’s relation in a clinical scenario  OCCLUSION STATIC OCCLUSION I- REST POSITION AND INTERMAXILLARY RELATIONS OCCLUSION  This is occlusion! This also is occlusion! Occlusion is the static relationship between the incising or masticating surfaces of the maxillary and the mandibular teeth or tooth analogues. Journal of Prosthetic Dentistry- 2016  OCCLUSION Occlusion is the STATIC relationship of the teeth and is basic to ALL aspects of dentistry. Okeson, J 2020  DETERMINANTS OF OCCLUSION AND TOOTH POSITION Tooth Size Arch Width Muscular Influences- Lips, Cheeks, Tongue Oral Habits- Pipe, Musical Instrument Mesial Drift Occlusal Contact Periodontal Health  STATIC OCCLUSION Static occlusion is the study of contacts between the teeth when the jaw is NOT moving. The contacts are POINTS. They are not lines  STATIC OCCLUSION Static occlusion is the study of contacts between the teeth when the jaw is NOT moving. The contacts are POINTS. They are not lines Points indicate contact and no movement DYNAMIC OCCLUSION Dynamic occlusion is the study of the contacts that the teeth make when the mandible is moving. The contacts are not points; they are LINES. DYNAMIC OCCLUSION Dynamic occlusion is the study of the contacts that the teeth make when the mandible is moving. The contacts are not points; they are LINES. Lines indicate point contact transitioning into a movement  OCCLUSION Static occlusion and dynamic occlusion analysis shows a combination of point and line tracings on teeth and stone casts Lines indicate point Points indicate contact transitioning contact and no into a movement movement FORCES  FORCES A force is a power that causes an object to move or that causes movement http://dictionary.cambridge.org/dictionary/american-english/force_1  FORCES Compression Shear Tension COMPRESSION FORCES AXIAL FORCES Stable forces Along the long axis Found throughout the human body (spine, pelvis and teeth) Knudson, Dwayne. Fundamentals of Biomechanics. June 2021 pgs. 55-78  SHEAR FORCES LATERAL FORCES Unstable forces Not along the long axis Cause damage or injury Knudson, Dwayne. Fundamentals of Biomechanics. June 2021 pgs. 55-78 :22 TENSION FORCES PULLING FORCES Pulling forces acting from opposite sides Force is directed axially along the long axis Knudson, Dwayne. Fundamentals of Biomechanics. June 2021 pgs. 55-78 FORCES IN OCCLUSION AXIAL (COMPRESSION) Stable, on long axis of tooth. Turn into compressive forces  AXIAL FORCES Premolars and molars (posterior teeth) can only tolerate AXIAL (compressive) loads! Trabecular bone and the Periodontal Ligament absorbs and cushions compressive loads! FORCES IN OCCLUSION SHEAR (LATERAL) Unstable, not on long axis of tooth. Cause movement or breakage :22 SHEAR FORCES Found In Anterior Teeth FORCES IN OCCLUSION TENSION (LIFTING) Pulling forces acting from opposite sides Force is directed axially along the long axis FORCES IN OCCLUSION TENSION (LIFTING) Pulling forces acting from opposite sides Force is directed axially along the long axis AXIAL vs. SHEAR FORCE Axial Shear :22  AXIAL vs. SHEAR FORCE But we have posterior teeth to protect anterior teeth from shear forces! AXIAL vs. SHEAR FORCE If patient is missing posterior teeth, there is a high risk of fatigue and fracture of anterior teeth LEVERS  TYPES OF LEVERS The fulcrum is between the load The load is between the fulcrum The effort is between the load and the effort and the effort and the fulcrum  CLASS III LEVER Masticatory System FULCRUM (TMJ) FORCE LOAD (MUSCLES) (FOOD)  In a Class III Lever, the closer the load (food)is to the fulcrum (TMJ), the more efficient the lever system More power, more efficient Less power, less efficient  A High Occlusal Contact… Changes a Class III Lever to a Class I Lever  A High Occlusal Contact… Changes a Class III Lever to a Class I Lever High occlusal contact moves the fulcrum from the TMJ to the area of the high contact Turning a Class III into a Class I lever torques the TMJ complex out of position and is detrimental for masticatory system!  ANGLE’S CLASSIFICATION ANGLE’S CLASSIFICATION  ANGLE’S CLASSIFICATION Developed by Edward Angle (Father of Modern Orthodontics) in 1890 Is a tooth /tooth relationship Based on the relative position of the permanent MAXILLARY FIRST MOLAR Canine position is used if permanent first molars are not present ANGLE’S CLASSIFICATION Class I Class II Division 1 Division 2 Class III  ANGLE’S CLASS I Maxillary canine cusp tip is placed Class I molar in the embrasure between the mandibular canine and first premolar Mesiobuccal cusp of maxillary first molar is placed over the buccal groove of mandibular Class I canine first molar  ANGLE’S CLASS II DIVISION 1 The maxillary arch Excessive overjet! is positioned (horizontal overlap) anterior The maxillary canine The mesiobuccal cusp tip is positioned cusp of the anterior to the maxillary first embrasure space molar is placed between the anterior to the mandibular canine buccal groove of and the first premolar the mandibular first molar  ANGLES CLASS II DIVISION 2 The Maxillary arch Excess overbite! is positioned (vertical overlap) anterior The mesiobuccal The maxillary canine cusp of the maxillary cusp tip is placed first molar is placed anterior to the anterior to the embrasure between buccal groove of the the mandibular canine mandibular first and first premolar molar COMPARISON CLASS II DIVISION 1 AND DIVISION 2 CLASS II CLASS II DIVISION 1 DIVISION 2 :35 SURGICAL & ORTHODONTIC CORRECTION OF ANGLE’S CLASS II  ANGLE’S CLASS III The Maxillary Negative overjet! arch is positioned distally The mesiobuccal The maxillary canine cusp of the cusp tip is placed maxillary first distal to the molar is placed embrasure space distal to the between the mandibular mandibular canine mesiobuccal and the first premolar groove SURGICAL & ORTHODONTIC CORRECTION OF ANGLE’S CLASS III MANDIBULAR POSITION MANDIBLE POSITION Mandible position is influenced by: Muscles Temporomandibular Joint Ligaments Occlusal Contacts Gravity :35 MANDIBLE POSITION DEPENDS ON: Temporomandibular joint anatomy Occlusal contacts of opposing teeth  EFFECTS OF POSITIONING MUSCLES ON THE MANDIBLE Medial Pterygoid Muscle Masseter Muscle Powerful Elevator Temporalis Muscle of the Mandible Elevates and Lateral Pterygoid Muscle retracts Mandible Protrudes the mandible anterior Medial Pterygoid Muscle Bilateral contraction elevates and protrudes the mandible. Okeson, J 2020 Unilateral contraction moves the mandible to the opposite side. Superior Head often the cause of TMD muscle pain MANDIBULAR STATIC POSITIONS CENTRIC RELATION MAXIMUM INTERCUSPATION REST POSITION Centric Relation is the SINGLE MOST important factor in occlusion and the only condylar position that permits an interference-free occlusion Dawson 2006 CENTRIC RELATION POSITION  CENTRIC RELATION (CR) “Is the relationship of the mandible to the maxilla when condyle-disk assemblies are in the most anterior superior position”. P. Dawson This mandibular position is repeatable This position is independent of teeth contacts This position physiologically and biomechanically permits an interference-free occlusion  CENTRIC RELATION “ORTHOPEDIC PHYSIOLOGIC POSITION OF THE CONDYLES IN THEIR MOST SUPEROANTERIOR POSITIONS IN THE ARTICULAR FOSSAE, RESTING AGAINST THE POSTERIOR SLOPES OF THE ARTICULAR EMINENCES WITH THE ARTICULAR DISCS PROPERLY INTERPOSED”. Jeffrey Okeson, 2003  Centric relation IS NOT about the position of the teeth Centric relation IS about position of the condyles  IF TEETH ARE NOT PRESENT… CENTRIC RELATION CAN BE Edentulous mandible can be in CR if the condyle-disk are adequately seated.  MAXIMUM INTERCUSPATION POSITION  MAXIMUM INTERCUSPATION (MI) Is the position of the mandible determined by the teeth when both arches are interposed at maximum contact. MAXIMUM INTERCUSPATION (MI) This position is determined when the patient habitually self closes into complete intercuspation. Zana,2015  REST POSITION REST POSITION Photo courtesy Natalya Zhuravskaya, MD CLINICAL OBSERVATION OF BOTH CENTRIC RELATION AND MAXIMUM INTERCUSPATION  Notice that there is NO DISTALIZATION of the mandible! SPECIAL MANDIBLE MANIPULATION IS REQUIRED TO GUIDE PATIENT INTO A REPEATABLE CENTRIC RELATION POSITION Dawson, P. 2007  Dawson, P.2007 1.SINGLE HANDED 2.BIMANUAL Special manipulation is required to guide mandible into CR It is a repeatable position :47  Different occlusal contacts are present in Centric Relation and in Maximum Intercuspation positions CR Different joint positions are present in Centric Relation and in Maximum Intercuspation positions MI :47  THIS IS THE INITIAL CONTACT IN CENTRIC CR RELATION THESE ARE ALL CONTACTS IN MAXIMUM MI INTERCUSPATION  This is why CR does not always coincide with MI Rarely does CR= MI. CR The big question is “How important is this?” VERY IMPORTANT- We will get into this over the next 5 lectures MI :47 CENTRIC RELATION/ MAXIMUM INTERCUSPATION DESCRIPENCY CR/ MI discrepancy is present in up to 90% of the population International Journal Dental and Medical Sciences Research Volume 4, Issue 2, Mar-Apr 2022 pp 158-163 www.ijdmsrjournal.com ISSN: 2582-6018 Checking initial contact in CR requires a steep learning curve. Typically, the first contact discloses as heavy mark.  QUESTION: In which mandibular position should we restore our patients?  Answer: *Most of restorative treatments are performed in maximum intercuspation (MI), as we want to maintain the habitual bite- as long as it is functional. MI Some complex cases (full mouth rehabilitation, decreased vertical) require restoring in Centric Relation (CR)  VERTICAL DIMENSION  VERTICAL DIMENSION Upper third of the face OF OCCLUSION (VDO) Is the vertical measurement of Middle third of the face the face between two Lower third of the face arbitrary points when the teeth are contacting. Dawson, P. FunctionalOcclusion,2006  VERTICAL DIMENSION Upper third of the AT REST (VDR) face Is the vertical measurement of the Middle third of the face face between two arbitrary points Lower third of theface when the jaws are at rest. Dawson, P. Functional Occlusion,2006  VERTICAL DIMENSION AT REST VS. OCCLUSION Measure lower 1/3 of patient’s face from bottom of nose to chin VDO VDR Measure between two points at Measure between two points maximum intercuspation at rest Is always less measurement than Usually, larger measurement VDR than VDO  PUTTING IT ALL TOGETHER Vertical Dimension Vertical Dimension At Rest Of Occlusion Freeway Space (46mm) (Minus) (42mm) (Equals) (4mm) MEASURING VERTICAL DIMENSION Extraoral analysis of vertical dimension VDR VDO 46mm 43mm Vertical Dimension Of Occlusion It can decrease as a result of tooth wear, parafunctional habits like bruxism and some types of malocclusions But it can also be re-established by different treatments such as prosthetics, orthognathic surgery or orthodontia LOSS OF VERTICAL DIMENSION VERTICAL DIMENSION AT REST 46mm VERTICAL DIMENSION OF OCCLUSION 43mm Centric Relation / Maximum Intercuspation discrepancy MAIN TOPICS TO REMEMBER 1.Axial Forces vs. Shear Forces 2.Centric Relation 3.Maximum Intercuspation 4.Angle’s Classification 5.Vertical Dimension  I May Not Have All Of The Answers … But I Will Find Them And I Am Committed To Taking You There! Jeffrey Wascher DDS Jeffrey Wascher DDS Thank You Questions? [email protected]  Sources Zana, D. Difference between centric relation and maximum intercuspation… European Journal of dentistry 2015 Oct-Dec: 9:573-579 Okeson, J. Management of Temporomandibular Disorders and Occlusion 2020 8th edition Cambridge Academic Content Dictionary http://dictionary.Cambridge.org/dictionary/American-english./force_1 Khakian, M. Dental occlusion: slide from centric relation to maximum intercuspation following bilateral manipulation of the mandible. U tube video Da DDS Midwestern University Dawson, P. Functional Occlusion From TMJ to Smile Design 2007 Garcia, Carolina DDS. Midwestern University Knudson, Dwayne. Fundamentals of Biomechanics June 2021, pgs. 55-78. This presentation may contain copyrighted material (“Material”), the use of which may not have been specifically authorized by the copyright owner. Midwestern University is making the Material available through this presentation solely and strictly for illustrative purposes, including criticism, comment, and teaching, with the objective of advancing dental education. This use of the Material constitutes a “fair use” of any such copyrighted Material as provided for in Section 107 of the United States Copy Right Law. In accordance with Title 17 U.S.C. § 107, the Material is distributed without profit to those who have research and/or educational interests. Reproduction or dissemination of the Material, including this presentation, in any format or medium is prohibited. All rights reserved