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Optimal occlusion and muscles of mastication (2) /certified fixed orthodontic courses by Indian dental academy

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The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit www.indiandentalacademy.com ,or call
0091-9248678078

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  • 1. OptimalOptimal OcclusionOcclusion INDIAN DENTAL ACADEMY Leader in continuing dental education www.indiandentalacademy.com www.indiandentalacademy.comwww.indiandentalacademy.com
  • 2. RequiredRequired Reading • Okeson, JP. Management of Temporomandibular Disorders and Occlusion , 5th ed., (2003), Mosby. Chapter 5. www.indiandentalacademy.comwww.indiandentalacademy.com
  • 3. Criteria for Optimal OcclusionCriteria for Optimal Occlusion • What is the ideal functional relationship of teeth? • What is an ideal occlusion? • Several concepts have developed over time Esthetic smile BMC 59.1 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 4. Concepts of OcclusionConcepts of Occlusion • Balanced Occlusion • Gnathology • Dynamic Individual Occlusion Esthetic smile BMC 59.1 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 5. Concepts of OcclusionConcepts of Occlusion BalancedBalanced OcclusionOcclusion • Bilateral and balancing contacts through all excursive movements • Protrusive • Laterotrusive • Developed for complete dentures • Rationale was thought to provide stability to dentures through all excursive movements • Carried over to dentate patients Esthetic smile BMC 59.1 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 6. Concepts of OcclusionConcepts of Occlusion GnathologyGnathology • Unilateral laterotrusive (working side) contacts • Anterior tooth contact in protrusive movements • Developed as desirability of a balanced occlusion for a dentate patient was questioned • Science of mandibular movement and tooth contacts • Used in restoring the dentate patient and in eliminating occlusal problems • All patients with any deviation from the ideal occlusion were treated Esthetic smile BMC 59.1 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 7. Concepts of OcclusionConcepts of Occlusion DynamicDynamic Individual OcclusionIndividual Occlusion • Concept is based on function and health rather than any ideal occlusal arrangement • In the absence of pathology, no treatment to change a patient’s occlusion would be necessary • Developed in the late 1970’s Esthetic smile BMC 59.1 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 8. Optimal OcclusionOptimal Occlusion • Masticatory system is extremely complex • Contraction of the elevator muscles produces • Tooth contacts • Forces on each TM joint • Forces are significant • Potential for damage is present • What is the optimal orthopedic relationship of the TM joints and teeth that will • Minimize damage? • Prevent damage? • Eliminate damage? Esthetic smile BMC 59.1 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 9. Optimal Orthopedic JointOptimal Orthopedic Joint PositionPosition • The position of the joints where the a stable orthopedic position is achieved is called Centric Relation • Early definitions described it as the most retruded position of the condyles • Called a ligamentous position • Important in fabricating complete dentures • Reproducible maxillomandibular position • Determines position of teeth in maximum intercuspation Esthetic smile BMC 59.1 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 10. Optimal Orthopedic JointOptimal Orthopedic Joint PositionPosition • Definition of Centric Relation has changed • Condyle is in the most retruded position in the fossa • Condyle is in the most superior position in the fossa • Condyles should be positioned downward and forward on the eminencia • Clinically, it is a necessary position to determine for both dentate and edentulous patients Esthetic smile BMC 59.1 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 11. Optimal Orthopedic JointOptimal Orthopedic Joint PositionPosition Articular DiscArticular Disc • Dense fibrous connective tissue • Lacks blood vessels and nerves • Able to tolerate forces without damage or pain being produced • Provides protection to condyle and fossa during movements • Articular disc doesn’t determine position of joint stability Esthetic smile BMC 59.1 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 12. Optimal Orthopedic JointOptimal Orthopedic Joint PositionPosition MusclesMuscles • Determine positional stability of the joint • Direction of the forces of the muscles determine the orthopedically stable joint position • Primary TM joints stabilizers • Masseter (anterosuperior) • Medial pterygoid (anterosuperior) • Temporalis (superior) • Contributors to TM joint stabilization • Lateral pterygoid (anterior) Elevator muscle directional force in stabilizing the TM joint Okeson Fig. 5-2 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 13. Optimal Orthopedic JointOptimal Orthopedic Joint PositionPosition MusclesMuscles • Most stable orthopedic position • Condyles in the most anterosuperior position in the fossa • This position is without occlusal interferences • Called the musculoskeletal stable (MS) position of the mandible • This direction of forces is consistent with the regions of the fossa able to withstand loading forces • Anterior and superior roof of fossa has thick bone Elevator muscle directional force in stabilizing the TM joint Okeson Fig. 5-2 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 14. Optimal Orthopedic JointOptimal Orthopedic Joint PositionPosition MusclesMuscles • Most stable orthopedic position • Condyles in the most anterosuperior position in the fossa • This position is without occlusal interferences • Called the musculoskeletal stable (MS) position of the mandible • This direction of forces is consistent with the regions of the fossa able to withstand loading forces • Anterior and superior roof of fossa has thick bone • Posterior condylar position is not the most stable • Bone of posterior fossa is thin • Retrodiscal tissue has sensory innervation and is highly vascular • Not designed to withstand heavy forces Most anterosuperior position of the joint (solid) Posterosuperior joint position (dotted line) Okeson Fig. 5-3 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 15. Optimal Orthopedic JointOptimal Orthopedic Joint PositionPosition LigamentsLigaments • Not active in joint function • Function to limit joint movement • Ligamentous position is a border position • Not an ideal position for an optimal orthopedic position for the TM (or any other) joint Most anterosuperior position of the joint (solid) Posterosuperior joint position (dotted line) Okeson Fig. 5-3 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 16. Optimal Orthopedic JointOptimal Orthopedic Joint PositionPosition • MS (musculoskeletal) position and CR (centric relation) are the same • Most stable TM joint position is with the condyles in an anterosuperior position in the fossa Most anterosuperior position of the joint (solid) Posterosuperior joint position (dotted line) Okeson Fig. 5-3 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 17. Optimal Orthopedic JointOptimal Orthopedic Joint PositionPosition • Is there an anteroposterior range while the condyle is in its most superior position? • PK Dawson says no • True for a healthy, young joint • Okeson says possible if TM ligament is loose and posterior movement can occur • A healthy joint permits very little posterior movement from the MS position Most anterosuperior position of the joint (solid) Posterosuperior joint position (dotted line) Okeson Fig. 5-3 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 18. Optimal Orthopedic JointOptimal Orthopedic Joint PositionPosition • In a chewing cycle, the working condyle moves posterior to the ICP during closure • Therefore some posterior movement (1mm) is normal during function • This can increase if • the TM ligaments are elongated • there is a joint disorder Most anterosuperior position of the joint (solid) Posterosuperior joint position (dotted line) Okeson Fig. 5-3 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 19. Other Joint Position ConceptsOther Joint Position Concepts • A concept by Gelb* suggests that there is another optimal condyle position • Condyles are in an optimal position when they are slightly translated • Forces are dissipated where bone is thickest • Actually a protrusive mandibular movement • Inferior lateral pterygoid muscles are contracting with the elevators • Inferior lateral pterygoids would be in a constant state of contraction • Not a MS (musculoskeletal) position • Represents a muscle stabilized position • Not compatible with resting musculature *Gelb H. Clinical management of head, neck and TMJ pain and dysfunction, Philadelphia, WB Saunders (1977). Anterior and inferior movement of condyle Okeson Fig. 5-5 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 20. Other Joint Position ConceptsOther Joint Position Concepts • As muscle pain is common in masticatory disorders, a joint position that has increased muscle activity would seem to be contraindicated. • Not a position consistent with a • Muscular rest position • Physiologic position Anterior and inferior movement of condyle Okeson Fig. 5-5 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 21. Other Joint Position ConceptsOther Joint Position Concepts • Relaxed muscle position concept • Using electrical stimulation and relaxation of the elevator muscles, the lowest EMG activity can be determined • This places the condyles in an anterior and inferior position to the MS or CR anterosuperior position • This rest position is at about 7-8mm of opening If the patient’s occlusion were built with the condyles anterior and inferior, what teeth would be in contact if the elevators contract and the inferior lateral pterygoid muscles are relaxed? Anterior and inferior movement of condyle Okeson Fig. 5-5 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 22. Optimal Tooth ContactsOptimal Tooth Contacts • Occlusal contacts influence the muscular control of the position of the mandible • Occlusal contacts result in neuromuscular feedback to find a stable occlusal position • Muscles can generate forces much greater than are required for function • Occlusal relationships should be developed to minimize possibility of damage to • Teeth • Peridontium • Muscles • TM joints www.indiandentalacademy.comwww.indiandentalacademy.com
  • 23. Optimal Tooth ContactsOptimal Tooth Contacts • Unilateral contact with two molars (2 teeth) • Assume that 40 pounds of force is applied during function • Right molars provide a fulcrum • Results in increased vertical force in the left TM joint • Results in decreased vertical force in the right TM joint • Mandibular position is not stable • Overclosure occurs on the left side • Heavy forces can result in damage to the • TM joints • Teeth • Peridontium Muscle activity and mandibular movement with two molars present Okeson Fig. 5-6 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 24. Optimal Tooth ContactsOptimal Tooth Contacts • Bilateral molar contact (4 teeth) • Contact is achieved on both sides on closure • Even, simultaneous contact on closure occurs • Additional teeth decrease the load • Same 40 pound load is decreased to 20 pounds on each tooth • Results in a more stable occlusal condition than previous example • Less potential for damage to • TM joints • Teeth • Peridontium Muscle activity and mandibular movement with bilateral molar contacts Okeson Fig. 5-7www.indiandentalacademy.comwww.indiandentalacademy.com
  • 25. Optimal Tooth ContactsOptimal Tooth Contacts • Bilateral molar and second premolar contact (8 teeth) • Contact is achieved on both sides on closure • Additional teeth decrease the load • Same 40 pound load is decreased to 10 pounds on each tooth • Results in an even more stable occlusal condition than previous example • Less potential for damage to • TM joints • Teeth • Peridontium Muscle activity and mandibular movement with bilateral molar and premolar contacts Okeson Fig. 5-8www.indiandentalacademy.comwww.indiandentalacademy.com
  • 26. Optimal Tooth ContactsOptimal Tooth Contacts SummarySummary • Contact with all teeth should be of even magnitude and simultaneous • Forces on individual teeth are minimized with this arrangement • Condyles should be in their most anterosuperior position in the fossa (MS position or CR position) • Therefore ideally, ICP is coincident with CR (MS) • This is called orthopedic stability Muscle activity and mandibular movement with bilateral molar and premolar contacts Okeson Fig. 5-8www.indiandentalacademy.comwww.indiandentalacademy.com
  • 27. Optimal Force DirectionOptimal Force Direction • Bone reacts to pressure force by resorbing • Periodontal ligament suspends the tooth in its socket • Most PDL fibres run in an oblique direction • Pressure force is converted to a tension force and stimulates bone formation • PDL can be considered to be a shock absorber that protects bone from occlusal force Expanded view of periodontal ligament Okeson Fig. 5-9 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 28. Optimal Force DirectionOptimal Force Direction • Occlusal forces directed along a cusp tip or flat surface such as a fossa or marginal ridge directs the force through the long axis of the tooth • Vertically directed forces are called axial loading Expanded view of periodontal ligament Okeson Fig. 5-9 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 29. Optimal Force DirectionOptimal Force Direction • Occlusal forces directed along a cusp tip or flat surface such as a fossa or marginal ridge directs the force through the long axis of the tooth • Vertically directed forces are called axial loading Axially directed forces Okeson Fig. 5-10 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 30. Optimal Force DirectionOptimal Force Direction • Axial loading can be achieved in two ways • Develop contacts on cusp tips or flat surfaces (fossa or marginal ridges) Axially directed forces Okeson Fig. 5-12a and b • Develop three contacts surrounding a cusp tip as it contacts a fossa • Called tripodization www.indiandentalacademy.comwww.indiandentalacademy.com
  • 31. Optimal Force DirectionOptimal Force Direction • Both direct forces axially and eliminate non-axially directed forces • Non-axially directed forces produce tipping forces that result in A compression of the PDL B expansion of the PDL • Potential for bone resorbtion Non-axially directed forces Okeson Fig. 5-11 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 32. Optimal Force MagnitudeOptimal Force Magnitude • Mandibular movements include laterotrusive and protrusive movements • Allows horizontal forces to be placed on teeth • Forces are potentially damaging Are some teeth better than others to accept these horizontal forces? • Masticatory system is a lever system • Similar to a nutcracker • More force can be generated closer to the fulcrum Greater force magnitude can be produced closer to the fulcrum (TMJ) Okeson Fig. 5-13 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 33. Optimal Force MagnitudeOptimal Force Magnitude • Mandibular movements include laterotrusive and protrusive movements • Allows horizontal forces to be placed on teeth • Forces are potentially damaging Are some teeth better than others to accept these horizontal forces? • Masticatory system is a lever system • Similar to a nutcracker • More force can be generated closer to the fulcrum Greater force magnitude can be produced closer to the fulcrum (TMJ) Okeson Fig. 5-13 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 34. Optimal Force MagnitudeOptimal Force Magnitude • More force can be generated on posterior teeth than on anterior teeth • Damaging horizontal forces are best managed by the anterior teeth Which of the anterior teeth are best suited to accept horizontal forces in eccentric movements? • Central incisors • Lateral incisors • Canines Why? Greater force magnitude can be produced closer to the fulcrum (TMJ) Okeson Fig. 5-13 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 35. Optimal Force MagnitudeOptimal Force Magnitude Which of the anterior teeth are best suited to accept horizontal forces in eccentric movements? • Canines Why? • Longest and largest roots • Best crown:root ratio • Surrounded by dense compact bone compared to the medullary bone of posterior teeth • Due to sensory input, there is lower muscle activity when the canines are in contact • Therefore, the canines are the best teeth to be in contact during a laterotrusive movement • Arrangement is called canine guidance or canine rise occlusion Left laterotrusive movement illustrating canine guidance Okeson Fig. 5-14 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 36. Optimal Force MagnitudeOptimal Force Magnitude Which of the anterior teeth are best suited to accept horizontal forces in eccentric movements? • Canines Why? • Longest and largest roots • Best crown:root ratio • Surrounded by dense compact bone compared to the medullary bone of posterior teeth • Due to sensory input, there is lower muscle activity when the canines are in contact • Therefore, the canines are the best teeth to be in contact during a laterotrusive movement • Arrangement is called canine guidance or canine rise occlusion Lingual view of a right laterotrusive movement with canine guidance Okeson Fig. 5-14 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 37. Optimal Force MagnitudeOptimal Force Magnitude • Most patients have other teeth in addition to the canines in contact in a laterotrusive movement • If canines plus some other posterior teeth are in contact in a laterotrusive movement, it is called a group function occlusion • Best arrangement is canines, premolars and the MB cusp of the first molar • Additional posterior contacts are undesirable due to proximity to the fulcrum (TM joint) Left laterotrusive movement illustrating group function Okeson Fig. 5-15 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 38. Optimal Force MagnitudeOptimal Force Magnitude • Most patients have other teeth in addition to the canines in contact in a laterotrusive movement • If canines plus some other posterior teeth are in contact in a laterotrusive movement, it is called a group function occlusion • Best arrangement is canines, premolars and the MB cusp of the first molar • Additional posterior contacts are undesirable due to proximity to the fulcrum (TM joint) Lingual view of a right laterotrusive movement with group function Okeson Fig. 5-15 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 39. Optimal Force MagnitudeOptimal Force Magnitude • Protrusive movements can generate horizontal forces that are potentially damaging • Anterior teeth are best suited to dissipate these forces • Distance from the fulcrum • Anterior teeth should disclude the posterior teeth because of the • Amount of force on posteriors • Direction of force on posteriors • In a protrusive movement, only the anterior teeth should contact, not the posterior teeth Lingual view of a protrusive movement Okeson Fig. 5-17 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 40. Optimal Force MagnitudeOptimal Force Magnitude Summary • Anterior teeth cannot tolerate heavy forces on closure (due to axial inclination) • Posterior teeth are best able to withstand closing forces • Anterior teeth are best able to tolerate eccentric forces • Laterotrusive • Protrusive Vestibular view of posterior bite collapse Okeson Fig. 5-18a www.indiandentalacademy.comwww.indiandentalacademy.com
  • 41. Optimal Force MagnitudeOptimal Force Magnitude Summary • Anterior teeth cannot tolerate heavy forces on closure (due to axial inclination • Posterior teeth are best able to withstand closing forces • Anterior teeth are best able to tolerate eccentric forces • Laterotrusive • Protrusive Posterior bite collapse and heavy anterior forces Okeson Fig. 5-18a www.indiandentalacademy.comwww.indiandentalacademy.com
  • 42. Effect of Posture on ToothEffect of Posture on Tooth ContactsContacts • The postural position is maintained during periods of inactivity • Lips are together and teeth are apart • Usually there is a space of 2-4mm between the teeth • Posture influences tooth contacts • If occlusion is established with the patient reclined, a posteriorly positioned occlusion will be established • With the patient upright, the mandible will be positioned slightly forward to this and result in heavy anterior contact • Called the anterior envelope of function Functional movements during a chewing stroke Okeson Fig. 4- 19 www.indiandentalacademy.comwww.indiandentalacademy.com
  • 43. Summary of Optimal OcclusionSummary of Optimal Occlusion • The condyles should be in their most anterosuperior position in the fossa during closure (MS or CR position) • All teeth should contact evenly • All teeth should contact simultaneously • Anterior tooth contact should be lighter than posterior contact in MI • All tooth contact should provide axial loading • In a laterotrusive movement, the working side teeth should disclude the non-working side teeth • The best working side guidance is canine guidance • Anterior teeth should provide immediate disclusion of all posterior teeth in protrusion • In an upright head position, posterior tooth contacts are heavier than anterior tooth contacts in MI • This type of occlusion is called a mutually protected occlusion www.indiandentalacademy.comwww.indiandentalacademy.com
  • 44. www.indiandentalacademy.comwww.indiandentalacademy.com Thank you For more details please visit www.indiandentalacademy.com