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Dental Occlusion

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Items of Occlusion

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Dental Occlusion

  1. 1. By Prof. Mohamad HelalProf. Mohamad Helal Head of Oral BiologyHead of Oral Biology DepartmentDepartment
  2. 2. Def.Def. Contact relationship of the upper and lower teeth during various activities of the mandible (mastication, swallowing and speech) .
  3. 3. •The relation of the upper and lower teeth when they are in maximum intercuspation during swallowing and the terminal position of the masticatory stroke.
  4. 4. •Is a position of the mandibule in which the condyles are resting in the most retrusive unstrained position in the glenoid fossa and related anteriorly to the distal slope of the articular eminence.
  5. 5. Why we study the occlusion? The study of occlusion helps in the treatment of malocclusion, Temporomandibular Joint problems, in proper construction of dentures and other dental restorations (e.g., crown and bridge, etc…).
  6. 6. To study the occlusion it must be include the following items: 1. Dental arch formation. 2. Compensatory curves of dental arches. 3. Compensatory curves of individual teeth. 4. Angulations of individual teeth in relation to various planes. 5. Functional form of the teeth at their incisal and occlusal thirds. 6. Facial relation of each tooth in one arch to its antagonist in centric occlusion. 7. Occlusal contact and intercuspation of all teeth of one arch with those in the opposing arch in centric occlusion. 8. Occlusal contact and interaction of all teeth during various functional movements. 1. Dental arch formation. 2. Compensatory curves of dental arches. 3. Compensatory curves of individual teeth. 4. Angulations of individual teeth in relation to various planes. 5. Functional form of the teeth at their incisal and occlusal thirds. 6. Facial relation of each tooth in one arch to its antagonist in centric occlusion. 7. Occlusal contact and intercuspation of all teeth of one arch with those in the opposing arch in centric occlusion. 8. Occlusal contact and interaction of all teeth during various functional movements.
  7. 7. 1. Dental arch formation: Outline of the maxillary arch is larger than mandibular arch • So, maxillary teeth overhang the mandibular teeth when the teeth are in centric occlusion •Permits overbite and overjet relation ship
  8. 8. OverbiteOverbite: vertical relation of the upper teeth to the lower teeth in centric occlusion . (increase efficiency of ant. teeth in biting Over jetOver jet: horizontal relation of the upper teeth to the lower teeth in centric occlusion . (increase duration of occlusal contact in protrusive and lateral movements in incision and mastication ) Importance:Importance: •Prevent soft tissue biting •Guide the mandible through various lateral movement
  9. 9. Overbite enables the disclusion of the posterior teeth during food incision and increases the efficiency of the anterior teeth in biting well. Overjet increases duration of occlusal contact in protrusive and lateral movements in incising and mastication.
  10. 10.  From occlusal aspect the outline following labial and lingual surfaces confirmed to a parabolic curves.parabolic curves. • the dental arches have three segments:the dental arches have three segments: 1.1.Anterior segmentAnterior segment : semicircularsemicircular line passing along facial surfaces of anterior teeth. 2.2.Middle segmentMiddle segment : straightstraight line continuous with semicircular segment , include 1st , 2nd , M half of 1st molar. 3.3.Posterior segmentPosterior segment : straightstraight line which is parallel to the median plane e including distobuccal half of 1st molar, B of 2nd and 3rd molars.
  11. 11. Phases in development of dental arches : 11stst phasephase:: 6 •6 years • 1st permanent molar take place post. to 2nd deciduous molar •Due to jaw growth Lead to : • 1- increase chewing efficiency 2- Serve to back up the deciduous teeth Mandibular one erupt firstly and max. one to established occlusion •1st permanent molar corner stonecorner stone 2nd phase:2nd phase: 1,2 •Central and lateral lingual to the deciduous predecessors.
  12. 12. 3rd phase:3rd phase: 4,5 •1st and 2nd premolar take place of deciduous molar. •Primate space the size of premolars are smaller than the larger teeth they replace. (Leeway space) 4th phase: 3,7 The canines (Keystones) and 2nd molars emerge. The forcing of the canine bet. Incisors & 1st premolars in both jaw with backing effect of 2nd molar 5th phase:5th phase: 8 •3rd molar distal to the 2nd molar.
  13. 13. Leeway spaceLeeway space • The erupting premolars are smaller in mesiodistal dimension than the primary molars. • The difference in sizes between the premolars and primary molars as well as the deciduous canines called “Leeway space’.
  14. 14. The average mesiodistal size of the deciduous molars in that area is 47mm, which when compared with the premolars dimension of 42.2 mm, indicates an average gain of 4.8 mm in available space. The leeway space must be utilized for alignment of the lower incisors as these teeth erupt with an average of 1.6 mm of crowding. The remainder of the space will be utilized by the mandibular molar.
  15. 15. This movement of the mandibular molars may correct an end-to-end molar relationship (normal for the mixed dentition) into a normal molar relationship in the permanent dentition, i.e., the mesiolingual cusp of the maxillary first molar occludes in the central fossa of the mandibular molar. This relationship is discussed later on.
  16. 16. 2- Compensatory Curvatures of the dental arches (Curved Occlusal Planes): The significant of these curve as guidance for mandible Movement to complement the condyle paths and for balance of mandible
  17. 17. •Curve of Spee • Sagittal planes. • Incisal Ridges of the anterior teeth and the B cusps of the posterior teeth follow a curve which end at the anterior surface of the condyle. • when the arches were observed from a point opposite 6.
  18. 18. Curve of Wilson • Coronal plane. • The occlusal surfaces of posterior teeth conform to a curved plane. • The crowns of mandibular posterior teeth must incline to the lingual while the crowns of maxillary posterior teeth must incline toward the buccal. • Deeper posteriorly molars inclination is greater than that of the premolar .
  19. 19. Curve of Monson • Combination of curve of Spee and the curve of Wilson. • coronal and sagittal planes. • concave for the mandibular arch and convex for the maxillary arch. • in centric occlusion form a segment of a sphere of 4 inches radius with the center of the sphere at the glabella
  20. 20. Bonwill TriangleBonwill Triangle • Describe the mandible and found that the mandibular dental arch adapts itself to an equilateral triangle of 4 inches length. • Apex at the mesial contact area of the lower central incisors • Angles of the base at the centers of each condyle
  21. 21. Importance of compensatory curves: Guidance for the mandible movement to complement the path of condyles for balance of the mandible.
  22. 22. 3- Compensating curvatures of individual teeth :  long axis of post. Teeth are not To a horizontal plane but show axial curvature  importance : 1- stability of teeth to resist force of mastication . 7, 8 distally inclined to prevent any distal drift of the posterior teeth. 7,8 mesially inclined to strike the maxillary molar
  23. 23. 3. Compensating curvatures of3. Compensating curvatures of the individual teeth:the individual teeth: When we observed theWhen we observed the dissected human jawdissected human jaw with their rootswith their roots exposed prove thatexposed prove that the long axis ofthe long axis of posterior teeth areposterior teeth are not perpendicular tonot perpendicular to a horizontal planea horizontal plane but show axialbut show axial curvature. Thiscurvature. This curvature iscurvature is essential for stabilityessential for stability of teeth in the dentalof teeth in the dental arches to resistarches to resist forces offorces of
  24. 24.  The maxillary 2The maxillary 2ndnd &3&3rdrd molars havemolars have distal inclinationdistal inclination to prevent anyto prevent any distal drift ofdistal drift of posterior teethposterior teeth while mandibularwhile mandibular 22ndnd & 3& 3rdrd molarmolar areare inclined mesiallyinclined mesially to strike theto strike the maxillary molarsmaxillary molars with a mesialwith a mesial direction of forcedirection of force
  25. 25. 4- Angulations of individual teeth4- Angulations of individual teeth in relation to various planesin relation to various planes The inclination ofThe inclination of a tooth from aa tooth from a vertical axis invertical axis in mesiodistal andmesiodistal and faciolingualfaciolingual directionsdirections 1- upper anterior:1- upper anterior: FL inclinedFL inclined linguallingual MD 1&2 inclinedMD 1&2 inclined slightly mesialslightly mesial but caninebut canine toward distaltoward distal
  26. 26. DefDef . Inclination of the tooth from a vertical axis in a MD and FL direction. (Considered root inclination so the crown inclined in opposite direction ). importance:importance: Proper occlusal function ( each tooth must be placed at the angle that best withstand forces during function )
  27. 27. 2-Maxillary premolars are slight lingual in FL, Distal in MD 3-Maxillary Molars roots have lingual inclination with distal inclination
  28. 28. 4-Mandibular4-Mandibular anterior haveanterior have greet lingualgreet lingual root inclinationroot inclination in FL. In MDin FL. In MD incisors areincisors are nearly straightnearly straight or minor rootor minor root inclinationinclination while caninewhile canine has distal roothas distal root inclinationinclination
  29. 29. 5- Mandibular5- Mandibular premolars In MDpremolars In MD have distalhave distal inclination but ininclination but in FL 1FL 1stst premolarpremolar incline lingually.incline lingually. But 2But 2ndnd premolarspremolars is offset buccallyis offset buccally 6-Mandibular molars6-Mandibular molars moderate to greatmoderate to great buccal and distalbuccal and distal toot angulationstoot angulations
  30. 30. Frontal view of the angulation of mandibular teeth:
  31. 31. Frontal view of the angulation of maxillary teeth:
  32. 32. Sagittal view of the angulation of maxillary & mandibular teeth:
  33. 33. FL angulations All teeth have lingual root inclination except the 2nd PM and mandibular M have buccal root inclination
  34. 34. MD angulations All teeth have distally root inclination except the upper incisors teeth have slight mesially root inclination and the lower incisors have slight mesial or straight .
  35. 35. 5. Functional form of the teeth at their5. Functional form of the teeth at their incisal and occlusal thirdsincisal and occlusal thirds There are no flat planes on the incisal or occlusalThere are no flat planes on the incisal or occlusal surface of any of the teeth unless they aresurface of any of the teeth unless they are created by wear or accident.created by wear or accident. The cusps and incisal ridges acts as cutting bladesThe cusps and incisal ridges acts as cutting blades when they are come to contact in centricwhen they are come to contact in centric occlusion, the concave surface opposing theocclusion, the concave surface opposing the ridges in circumscribed points or areas andridges in circumscribed points or areas and spaces appear all around this point which act asspaces appear all around this point which act as spillways or escapement spacespillways or escapement space So, this escapement space is provided in teeth bySo, this escapement space is provided in teeth by the form of cusps, ridges, DG, ISthe form of cusps, ridges, DG, IS
  36. 36. • Provided in teeth by cusps, ridges, DG , interdental spaces . • its location and form differ when occlousal relation is changed. • less space in centric occlusion and large space in lateral relation .
  37. 37. The location and form the escapement areThe location and form the escapement are changed when the occlusal relation ischanged when the occlusal relation is changeschanges In centric occlusion with less escapementIn centric occlusion with less escapement space available but in lateral relation thespace available but in lateral relation the escapement is increased but the numberescapement is increased but the number of contact point is decreasedof contact point is decreased
  38. 38. 6&7. The relation of each tooth in6&7. The relation of each tooth in one arch to its antagonist in theone arch to its antagonist in the opposing arch in centric occlusionopposing arch in centric occlusion Centric occlusion It is relation of the upper and lower teeth when they are intercuspated together and the condyle are in resting in most retrusive position in the glenoid fossa.
  39. 39. 11stst permanent maxillary molar followed bypermanent maxillary molar followed by mandibular one are a key of occlusion why??mandibular one are a key of occlusion why?? -1-1stst tooth permanent erupted in oral cavitytooth permanent erupted in oral cavity -Largest in dental arch-Largest in dental arch -Guided by its position the deciduous teeth-Guided by its position the deciduous teeth -Have no predecessors-Have no predecessors -Maxillary one more accurate than mandibular-Maxillary one more accurate than mandibular because it attached to fixed in base of skullbecause it attached to fixed in base of skull -In normal jaw relations and when teeth are of-In normal jaw relations and when teeth are of normal size and in the correct position, thenormal size and in the correct position, the mesiobuccal cusp of the maxillary first molarmesiobuccal cusp of the maxillary first molar occludes in the mesiobuccal groove of theoccludes in the mesiobuccal groove of the mandibular first molar. This normalmandibular first molar. This normal relationship of these two teeth is called therelationship of these two teeth is called the key of occlusionkey of occlusion ..
  40. 40. key of occlusionkey of occlusion
  41. 41. ANGLES CLASSIFICATION.Angle was a dentistANGLES CLASSIFICATION.Angle was a dentist who developed a classification of normal andwho developed a classification of normal and abnormal ways teeth meet into centric occlusion.abnormal ways teeth meet into centric occlusion. Angle came up with threeAngle came up with three classes, Class I, II and IIIclasses, Class I, II and III 1-Class I patient's profile is1-Class I patient's profile is characterized as normal.characterized as normal. 2-Class II patient's profile is2-Class II patient's profile is deficient in chin length anddeficient in chin length and characterized as a retrudedcharacterized as a retruded (retrognathic) profile.(retrognathic) profile. 3-Class III patient's profile is3-Class III patient's profile is excessive in chin length andexcessive in chin length and characterized as protrudedcharacterized as protruded (prognathic) profile.(prognathic) profile.
  42. 42. Class I Class II Class III Angle’s Classification:Angle’s Classification:
  43. 43. The centric relation of the teeth inThe centric relation of the teeth in centric occlusion :centric occlusion :Permanent toothPermanent tooth The median plane isThe median plane is coincident in two jawscoincident in two jaws Upper tooth has labialUpper tooth has labial relation to lower incisor inrelation to lower incisor in centriccentric - Incisal ridges is free of- Incisal ridges is free of contact and has labial relationcontact and has labial relation to labioincisal portion of lowerto labioincisal portion of lower central incisorcentral incisor - Cingulum above the lingual- Cingulum above the lingual embrasure of 1&2 lowerembrasure of 1&2 lower incisorincisor - Mesial outline is in line with- Mesial outline is in line with the mesial outline of lowerthe mesial outline of lower laterral incisorlaterral incisor The distal outline is centeredThe distal outline is centered
  44. 44. 6- Facial and lingual Relations of Each Tooth in6- Facial and lingual Relations of Each Tooth in One Arch to Its Antagonist in the Opposing Arch inOne Arch to Its Antagonist in the Opposing Arch in Centric Occlusion.Centric Occlusion. •In centric occlusion, each tooth occludes with two teeth in the opposing arch, except the mandibular central incisors and the maxillary third molars. •Importance:Importance: 1.Prevent the over eruption of the teeth of the opposing arch. 2.prevent the mesial migration of the teeth in the same arch. 3.Distribute occlusal forces to several teeth. mesial migration
  45. 45. Tooth Alignment and OcclusionTooth Alignment and Occlusion Normal Interarch RelationshipsNormal Interarch Relationships The mandibular first molar is positionedThe mandibular first molar is positioned mesial to the maxillary first molarmesial to the maxillary first molar Interarch relationship of opposing teeth Modified after Okeson Fig. 3-21 Contact Relationships-Contact Relationships- OcclusalOcclusal contacts of posterior teethcontacts of posterior teeth The mesiobuccal cusp of theThe mesiobuccal cusp of the mandibular first molar occludes in themandibular first molar occludes in the embrasure between the maxillaryembrasure between the maxillary second premolar and the first molarsecond premolar and the first molar The mesiobuccal cusp of the maxillaryThe mesiobuccal cusp of the maxillary first molar is opposite the mesiobuccalfirst molar is opposite the mesiobuccal (buccal) groove of the mandibular first(buccal) groove of the mandibular first molarmolar The mesiolingual cusp of the maxillaryThe mesiolingual cusp of the maxillary first molar occludes in the central fossafirst molar occludes in the central fossa of the mandibular first molarof the mandibular first molar
  46. 46. Tooth Alignment and OcclusionTooth Alignment and Occlusion Normal Interarch RelationshipsNormal Interarch Relationships Normal buccolingual relationship of the molars Modified after Okeson Fig. 3- 12  Normal buccolingual relationshipNormal buccolingual relationship allows forallows for  efficient use of musculature in chewingefficient use of musculature in chewing  Minimizing trauma from cheek or tongue-Minimizing trauma from cheek or tongue- bitingbiting  Functional cuspsFunctional cusps buccal cusps of Mandibularbuccal cusps of Mandibular posterior teethposterior teeth lingual cusps of Maxillarylingual cusps of Maxillary posterior teethposterior teeth  Centric cuspsCentric cusps  Centric holding cuspsCentric holding cusps  Stamp cuspsStamp cusps  Maintain vertical dimension or distanceMaintain vertical dimension or distance between the maxilla and mandiblebetween the maxilla and mandible
  47. 47. Tooth Alignment and OcclusionTooth Alignment and Occlusion Normal Interarch RelationshipsNormal Interarch Relationships Normal contacts in a Class I occlusion Modified after Okeson Fig. 3-23 Contact Relationships-Contact Relationships- MesiodistalMesiodistal • Occlusal contacts result from functioningOcclusal contacts result from functioning cusps contacting the opposing CF linecusps contacting the opposing CF line • Contacts will occur inContacts will occur in • Central fossaeCentral fossae • Comparable to a mortar and pestleComparable to a mortar and pestle (臼(臼 杵)杵) • Two dissimilar shaped surfaces meetTwo dissimilar shaped surfaces meet result in a spillway being produced andresult in a spillway being produced and masticatory efficiencymasticatory efficiency SUMMARY STATEMENTSSUMMARY STATEMENTS • Mesiolingual cusp of eachMesiolingual cusp of each maxillary molar occludes in themaxillary molar occludes in the central fossa of the opposingcentral fossa of the opposing mandibular molarmandibular molar • Mesiobuccal cusp of eachMesiobuccal cusp of each mandibular molar occludes on themandibular molar occludes on the mesial marginal ridge of themesial marginal ridge of the
  48. 48. Tooth Alignment and OcclusionTooth Alignment and Occlusion Normal Interarch RelationshipsNormal Interarch Relationships Normal contacts in a Class I occlusion Modified after Okeson Fig. 3-23 Contact Relationships-Contact Relationships- MesiodistalMesiodistal • Occlusal contacts result from centricOcclusal contacts result from centric cusps contacting the opposing CF linecusps contacting the opposing CF line • Contacts will occur inContacts will occur in • Central fossaeCentral fossae • Comparable to a mortar and pestleComparable to a mortar and pestle • Two dissimilar shaped surfaces meetTwo dissimilar shaped surfaces meet result in a spillway being producedresult in a spillway being produced and masticatory efficiencyand masticatory efficiency • Marginal ridges andMarginal ridges and embrasuresembrasures • Cusp tip is very convexCusp tip is very convex • Marginal ridge is slightly convex (flatMarginal ridge is slightly convex (flat by comparison)by comparison) • Actual contact is not cusp tip butActual contact is not cusp tip but 0.5mm area around it0.5mm area around it
  49. 49. Facial relation of the upper and lowerFacial relation of the upper and lower teeth in centric occlusionteeth in centric occlusion
  50. 50. lingual relation of the upper and lowerlingual relation of the upper and lower teeth in centric occlusionteeth in centric occlusion
  51. 51. Facial relation of the upper and lowerFacial relation of the upper and lower teeth in centric occlusionteeth in centric occlusion
  52. 52. lingual relation of the upper andlingual relation of the upper and lower teeth in centric occlusionlower teeth in centric occlusion
  53. 53. Centric occlusion relation of theCentric occlusion relation of the deciduous teethdeciduous teeth At age 3 years, the child has centric occlusion similar to permanent teeth
  54. 54. Centric occlusion relation of the deciduous teeth:Centric occlusion relation of the deciduous teeth: At age 3 years the child has centric occlusion similar to permanent teeth
  55. 55. Tooth Alignment and OcclusionTooth Alignment and Occlusion Contacts during Mandibular MovementsContacts during Mandibular Movements Anterior guidance Okeson Fig. 3-30 Contact Relationships-Contact Relationships- PROTRUSIONPROTRUSION • Potential posterior contacts in aPotential posterior contacts in a protrusive movement are theprotrusive movement are the • mesial inclines of mandibularmesial inclines of mandibular teeth (fossae and marginalteeth (fossae and marginal ridges)ridges) • distal inclines of the maxillarydistal inclines of the maxillary teeth (lingual cusps)teeth (lingual cusps) • These contacts are undesirable andThese contacts are undesirable and are calledare called ProtrusiveProtrusive interferencesinterferences
  56. 56. Tooth Alignment and OcclusionTooth Alignment and Occlusion Contacts during Mandibular MovementsContacts during Mandibular Movements Left laterotrusive movement (and right mediotrusive movement) Okeson Fig. 3-31 Contact Relationships-Contact Relationships- LATEROTRUSIVELATEROTRUSIVE MANDIBULAR MOVEMENTMANDIBULAR MOVEMENT • Desirable contacts in a leftDesirable contacts in a left laterotrusive movement arelaterotrusive movement are maxillary buccal cusps inmaxillary buccal cusps in contact with mandibularcontact with mandibular buccal cuspsbuccal cusps Working Side Non- working Side
  57. 57. Tooth Alignment and OcclusionTooth Alignment and Occlusion Contacts during Mandibular MovementsContacts during Mandibular Movements Left laterotrusive movement (and right mediotrusive movement) Okeson Fig. 3-31 Contact Relationships-Contact Relationships- LATEROTRUSIVELATEROTRUSIVE MANDIBULAR MOVEMENTMANDIBULAR MOVEMENT • Other contacts that mayOther contacts that may occur includeoccur include • WORKING SIDEWORKING SIDE (LATEROTRUSIVE)(LATEROTRUSIVE) INTERFERENCESINTERFERENCES • Outer inclines of maxillaryOuter inclines of maxillary lingual cuspslingual cusps • Inner inclines of mandibularInner inclines of mandibular lingual cuspslingual cusps • NON-WORKINGNON-WORKING (MEDIOTRUSIVE)(MEDIOTRUSIVE) INTERFERENCESINTERFERENCES • Inner inclines of maxillaryInner inclines of maxillary lingual cuspslingual cusps • Inner inclines of mandibularInner inclines of mandibular buccal cuspsbuccal cusps Working Side Non- working Side
  58. 58. 8-The Occlusal Contact and Intercusp8-The Occlusal Contact and Intercusp Relations of all the Teeth During the VariousRelations of all the Teeth During the Various Functional mandibular movements.Functional mandibular movements. Mandibular movements are: (rotating movement ) A.Symmetrical bilateral movements:A.Symmetrical bilateral movements: •Depression. •Elevation. •Protrusion. •Retrusion. B.Asymmetrical bilateral movements:B.Asymmetrical bilateral movements: •Right lateral movements. •Left lateral movements.
  59. 59. 8-the Occlusal Contact And Intercusp Relation8-the Occlusal Contact And Intercusp Relation Of All Teeth During The Various FunctionalOf All Teeth During The Various Functional Mandibular MovemMandibular Movem6464entent The mandibular movement are:The mandibular movement are: A) Symmetrical bilateral movement:A) Symmetrical bilateral movement: -Depression-Depression -Elevation-Elevation -Protrusion-Protrusion -Retrusion-Retrusion B) Asymmetrical bilateral movement:B) Asymmetrical bilateral movement: -Right lateral movement-Right lateral movement -Left lateral movement-Left lateral movement
  60. 60. Rest position of the mandible :Rest position of the mandible : •When the mandible is at rest lower teeth are not in contact with the upper teeth as there is a space of 2 mm in-between the two arches freeway space . •Not a functional relation. functional relations offunctional relations of mandibular movements:mandibular movements: 1.Protrusive occlusal relation. 2.Retrusive occlusal relation. 3.Right occlusal relation. 4.Left occlusal relation
  61. 61. •The mandibular arch bears a forward, anterioranterior relation to its centric relationcentric relation with the maxillary arch. •Biting or shearing food material 1)1) Protrusive occlusal relation:Protrusive occlusal relation:
  62. 62. •Retrusion of the mandible, •the mandibular teeth will have posteriorposterior relation to centric occlusioncentric occlusion with the maxillary arch. •Very limited and non functional movement. 2)Retrusive occlusal relation:2)Retrusive occlusal relation:
  63. 63. •The mandibular dental arch is placed in a right orright or leftleft lateral relation to centric occlusioncentric occlusion with the maxillary arch. 3) Right and left lateral occlusal relation:3) Right and left lateral occlusal relation:
  64. 64. The masticatory cycle of posteriorThe masticatory cycle of posterior teeth:teeth: •The working side shows the buccal cusps of maxillary and mandibular teeth to be in contact. •The balancing side shows contact of lingual cusps of the maxillary teeth with the buccal cusps of mandibular teeth. •Then both sides move to centric occlusion.
  65. 65. Working sideWorking side Balancing sideBalancing side
  66. 66. The masticatory cycle of anterior teeth:The masticatory cycle of anterior teeth: • In bitting • the functioning side is located at the anterior teeth • the balancing side at the posterior teeth.
  67. 67. When the two jaw are not in occlusion, thereWhen the two jaw are not in occlusion, there is a space of 2mm (freeway space)is a space of 2mm (freeway space) inbetween the two arches called Restinbetween the two arches called Rest positionposition 1- Protrusive occlusal relation:1- Protrusive occlusal relation: Mandible arch bear a forward relation to itsMandible arch bear a forward relation to its centric relation with maxillary arch. (bitingcentric relation with maxillary arch. (biting or sheering food material)or sheering food material) 2-Retrusive occlusal relation:2-Retrusive occlusal relation: Mandible will have posterior relation toMandible will have posterior relation to centric occlusion with upper arch. (limitedcentric occlusion with upper arch. (limited and non functional movement)and non functional movement)
  68. 68. Right and left lateral movement: achieved byRight and left lateral movement: achieved by lateral movement of mandible where is placed Rlateral movement of mandible where is placed R or L to centric occlusionor L to centric occlusion Musticatory cycle of posterior teeth: duringMusticatory cycle of posterior teeth: during movement, the posterior teeth are not in contact.movement, the posterior teeth are not in contact. SoSo the working sidethe working side shows buccal cusps of max.shows buccal cusps of max. and mandibular to be in contactand mandibular to be in contact InIn balanced sidebalanced side shows contact of lingual cusps ofshows contact of lingual cusps of max. with buccal cusp of mandibular teeth thenmax. with buccal cusp of mandibular teeth then come to centric occlusion. These movement iscome to centric occlusion. These movement is calledcalled musticatory movementmusticatory movement

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