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Maxillo-Mandibular Relationships Centric and Protrusive Records.

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Presentation on theme: "Maxillo-Mandibular Relationships Centric and Protrusive Records."— Presentation transcript:

1 Maxillo-Mandibular Relationships Centric and Protrusive Records

2 Problems Establishing Edentulous Maxillo-mandibular Relationships Edentulous patients have more difficulty determining where their denture teeth should contactEdentulous patients have more difficulty determining where their denture teeth should contact No periodontal membraneNo periodontal membrane Old dentures won’t fit on castsOld dentures won’t fit on casts Record base fit and wax rim changes confuse some patientsRecord base fit and wax rim changes confuse some patients Edentulous patients have more difficulty determining where their denture teeth should contactEdentulous patients have more difficulty determining where their denture teeth should contact No periodontal membraneNo periodontal membrane Old dentures won’t fit on castsOld dentures won’t fit on casts Record base fit and wax rim changes confuse some patientsRecord base fit and wax rim changes confuse some patients

3 Centric Position Acceptable position should be: Conducive to healthConducive to health Relatively repeatableRelatively repeatable position can be checked before dentures completedposition can be checked before dentures completed Acceptable position should be: Conducive to healthConducive to health Relatively repeatableRelatively repeatable position can be checked before dentures completedposition can be checked before dentures completed

4 Conducive to Health Relatively Symmetrical PositionRelatively Symmetrical Position Not ‘absolute’ symmetryNot ‘absolute’ symmetry Less chance of muscle strain which might occur in non-centered positionsLess chance of muscle strain which might occur in non-centered positions Relatively Symmetrical PositionRelatively Symmetrical Position Not ‘absolute’ symmetryNot ‘absolute’ symmetry Less chance of muscle strain which might occur in non-centered positionsLess chance of muscle strain which might occur in non-centered positions

5 Hinge Position is Repeatable relatively centeredrelatively centered patient can find stable occlusal contacts relatively easilypatient can find stable occlusal contacts relatively easily allows change in vertical dimensionallows change in vertical dimension relatively centeredrelatively centered patient can find stable occlusal contacts relatively easilypatient can find stable occlusal contacts relatively easily allows change in vertical dimensionallows change in vertical dimension

6 Centric Relation (CR) Centric position of mandible in relation to the maxillaCentric position of mandible in relation to the maxilla Defined by the position of the condyles, rather than the teethDefined by the position of the condyles, rather than the teeth Hinge positionHinge position

7 Centric Relation Treatment positionTreatment position Not necessarily ‘ideal’ or ‘normal’Not necessarily ‘ideal’ or ‘normal’

8 Centric Occlusion (CO) Maxillo-mandibular position determined by teethMaxillo-mandibular position determined by teeth Sometimes considered coincident with ‘maximum intercuspation’ or ‘habitual closure’Sometimes considered coincident with ‘maximum intercuspation’ or ‘habitual closure’

9 CR and CO have been defined differently by various investigators, and differently over different time periods

10 Where is Centric Relation? Glossary of Prosthodontic Terms: Independent of tooth contactIndependent of tooth contact Clinically discernible when the mandible is directed superiorly and anteriorlyClinically discernible when the mandible is directed superiorly and anteriorly Independent of tooth contactIndependent of tooth contact Clinically discernible when the mandible is directed superiorly and anteriorlyClinically discernible when the mandible is directed superiorly and anteriorly

11 Where is Centric Relation? Glossary of Prosthodontic Terms: Glossary of Prosthodontic Terms: Condyles articulate with thinnest, avascular portion disks Anterior-superior position against slope of the articular eminence Glossary of Prosthodontic Terms: Glossary of Prosthodontic Terms: Condyles articulate with thinnest, avascular portion disks Anterior-superior position against slope of the articular eminence

12 Where is Centric Relation? Glossary of Prosthodontic Terms: Purely rotary movement about the transverse horizontal axisPurely rotary movement about the transverse horizontal axis

13 Other definitions of centric relation have included: Rearmost, Uppermost, Midmost (RUM)Rearmost, Uppermost, Midmost (RUM) Most PosteriorMost Posterior Rearmost, Uppermost, Midmost (RUM)Rearmost, Uppermost, Midmost (RUM) Most PosteriorMost Posterior

14 Posterior positioning of the condyles is no longer considered desirable (Celenza)

15 Anterior-Superior Position Thickening (buttressing) occurs in areas of bone where articulation occurs Thickest part of the articular eminence is the anterior portion of the glenoid fossaeThickest part of the articular eminence is the anterior portion of the glenoid fossae

16 Anterior-Superior Position The articular disk is in a superior-anterior position

17 Anterior-Superior Position The neurovascular supply of the retro-discal pad is posterior to the articular diskThe neurovascular supply of the retro-discal pad is posterior to the articular disk If condyles articulated in a most posterior position – impingementIf condyles articulated in a most posterior position – impingement

18 Anterior-Superior Position Fibrocartilage on anterior, not posterior of the glenoid fossaeFibrocartilage on anterior, not posterior of the glenoid fossae Articular cartilage on superior and anterior of the condylesArticular cartilage on superior and anterior of the condyles Cartilage covers articular surfaces

19 Anterior-Superior Position Posterior-most positions require forcePosterior-most positions require force Pressure may force condyles down posterior slope, or cause flexure of mandiblePressure may force condyles down posterior slope, or cause flexure of mandible

20 For the purpose of fabricating complete dentures, the superior- anterior position of Centric Relation will be used

21 Clinically the dentist cannot determine the actual position of the condyles at the time jaw relations records are made

22 Centric Relation - Why? Allows function to all positionsAllows function to all positions Conducive to health (non-pathologic)Conducive to health (non-pathologic) Brill et al - pain & loss of occlusal sense when not in CRBrill et al - pain & loss of occlusal sense when not in CR Renyolds - 24% of normal population has CR=CORenyolds - 24% of normal population has CR=CO

23 Centric Relation - Why? Convenient - relatively centered (Celenza)Convenient - relatively centered (Celenza) More reproducible (Grasser)More reproducible (Grasser) Easier to set a stable occlusionEasier to set a stable occlusion

24 Centric Relation - Why? OVD can be changed and condylar inclination will not have to be readjusted (arcon articulators) (Celenza)OVD can be changed and condylar inclination will not have to be readjusted (arcon articulators) (Celenza) CR is not far from CO at same occlusal vertical dimension (Wilson and Nairn)CR is not far from CO at same occlusal vertical dimension (Wilson and Nairn)

25 Centric Occlusion - Why Not? Position is difficult to determine - not as reproducible Patients cannot tell where centric occlusion or a habitual position is with bulky wax rims in positionPatients cannot tell where centric occlusion or a habitual position is with bulky wax rims in position No habitual position with new wax rimsNo habitual position with new wax rims (Crum and Loiselle; Brill et al)

26 Centric Occlusion - Why Not? CO may be a dysfunctional positionCO may be a dysfunctional position Palpate muscles, TMJ to ensure no dysfunction (Brill et al)Palpate muscles, TMJ to ensure no dysfunction (Brill et al)

27 Centric Occlusion - Why Not? Not reproducible, so the influence of other variables on the centric record cannot be assessed: Wax consistencyWax consistency Biting forceBiting force Symmetry of guidanceSymmetry of guidance (Yurkstas and Kapur)

28 Centric Occlusion - Why Not? CO may lead to dysfunction - no studies to absolutely prove this hypothesis

29 When to Use Centric Relation When entire occlusion being restoredWhen entire occlusion being restored No remaining posterior centric stopsNo remaining posterior centric stops When complete, fixed, or removable partial dentures involve the entire occlusionWhen complete, fixed, or removable partial dentures involve the entire occlusion When entire occlusion being restoredWhen entire occlusion being restored No remaining posterior centric stopsNo remaining posterior centric stops When complete, fixed, or removable partial dentures involve the entire occlusionWhen complete, fixed, or removable partial dentures involve the entire occlusion

30 When to Not to Use Centric Relation Stable occlusionStable occlusion No pathologyNo pathology Posterior centric stops presentPosterior centric stops present No valid reason to changeNo valid reason to change Use maximum intercuspationUse maximum intercuspation

31 Registering Centric Relation Bimanual manipulation Patient in a slightly supine position

32 Registering Centric Relation Bimanual manipulation Occlusion rim notched to aid stabilizing the record basesOcclusion rim notched to aid stabilizing the record bases

33 Registering Centric Relation Bimanual manipulation Index fingers on the rim, thumbs under symphysisIndex fingers on the rim, thumbs under symphysis

34 Registering Centric Relation Jiggle the mandibleJiggle the mandible Mandible should freely arcMandible should freely arc Allow the patient to close into contactAllow the patient to close into contact

35 Registering Centric Relation Do NOT push the mandible or dislodge the record baseDo NOT push the mandible or dislodge the record base Medium must be dead softMedium must be dead soft (Yurkstas and Kapur)

36 Registering Centric Relation Minimal closing pressureMinimal closing pressure (Yurkstas and Kapur)

37 Recording Centric Position

38 Preparing Occlusion Rims Place 3 widely separated lines between the rims in the centric positionPlace 3 widely separated lines between the rims in the centric position CRITICAL! Check that record base heels/rims do not touchCRITICAL! Check that record base heels/rims do not touch

39 Line up Marks Eliminate contact with record basesEliminate contact with record bases

40 Registering Centric Relation Max & Mand Occusion Rims Two sharp “V”-shaped notches in the molar/premolar area of each sided waxTwo sharp “V”-shaped notches in the molar/premolar area of each sided wax Depth 1-2 mmDepth 1-2 mm 1-2 mm

41 Ensure Adequate Notch Depth Too Shallow - no undercuts

42 Registering Centric Relation Rehearse making the record without recording mediumRehearse making the record without recording medium Place occlusion rims intraorallyPlace occlusion rims intraorally PVS registration material (Memoreg) over entire occlusal rimPVS registration material (Memoreg) over entire occlusal rim

43 Thin Layer of Material Too Thick Good

44 Thin Layer Want flat record, no excess on sides of rimsWant flat record, no excess on sides of rims Excess material recording of the sides of the rim can cause deflection when checking recordExcess material recording of the sides of the rim can cause deflection when checking record

45 Making the Record Have patient close into recordHave patient close into record Ensure smooth arc of closure, no horizontal deviationsEnsure smooth arc of closure, no horizontal deviations Use index fingers to stabilize lower record baseUse index fingers to stabilize lower record base

46 Alternate Medium AlluwaxAlluwax Must be dead softMust be dead soft

47 Registering Centric Relation Place Alluwax into a 1- 2mm slot in maxillary rimPlace Alluwax into a 1- 2mm slot in maxillary rim Fill to slight excessFill to slight excess Ensure wax is dead softEnsure wax is dead soft Hot water bath for softening (use care)Hot water bath for softening (use care)

48 Keep Wax Neat

49 Registering Centric Relation Stabilize mandibular record base using index fingers on the flange (or in a recess in the rim) and the thumbs under the symphysis

50 Registering Centric Relation Patient opens, relaxes, and slowly closes

51 Registering Centric Relation Gently arc the mandible in a hinge-like motionGently arc the mandible in a hinge-like motion There should be:There should be: No translationNo translation No splintingNo splinting

52 Registering Centric Relation Patient slowly closesPatient slowly closes Operator uses tactile senses to ensure the mandible does not translateOperator uses tactile senses to ensure the mandible does not translate

53 Registering Centric Relation Patient closes until rims are almost touching (1 mm separation)Patient closes until rims are almost touching (1 mm separation) Ask patient to stop as soon as this position has been reachedAsk patient to stop as soon as this position has been reached Some may not be able to tell when they contactSome may not be able to tell when they contact

54 Registering Centric Relation Never instruct the patient to bite firmlyNever instruct the patient to bite firmly Causes translation or inaccuracy in the recordCauses translation or inaccuracy in the record

55 Registering Centric Relation Hold position until set 1-2 minHold position until set 1-2 min Remove both rims togetherRemove both rims together SeparateSeparate

56 Registration Should be Sharp, Not Rounded

57 Registering Centric Relation Mounting the Mandibular Cast Ensure record is repeatableEnsure record is repeatable Increase the height of incisal pin 1 mm, invert articulatorIncrease the height of incisal pin 1 mm, invert articulator Place wax rims together, lute with sticky wax - 4 spotsPlace wax rims together, lute with sticky wax - 4 spots

58 Registering Centric Relation Mount the mandibular cast with mounting plasterMount the mandibular cast with mounting plaster After mounting, remove the record & adjust the incisal pin to allow contact between rimsAfter mounting, remove the record & adjust the incisal pin to allow contact between rims Occlusion rims should be touching evenly, over the entire occlusal surfaceOcclusion rims should be touching evenly, over the entire occlusal surface

59 Registering Centric Relation Do not alter incisal pin after rims are contactingDo not alter incisal pin after rims are contacting Otherwise, height of correct vertical dimension can be lostOtherwise, height of correct vertical dimension can be lost

60 Check CR Record Take new record, place on articulatorTake new record, place on articulator Release articulator centric locksRelease articulator centric locks Should arc into record without any translationShould arc into record without any translation If doesn’t take 3rd record to see which one is reproducibleIf doesn’t take 3rd record to see which one is reproducible

61 Protrusive Records Used to set condylar guidanceUsed to set condylar guidance Helps setting teeth for best occlusal contactsHelps setting teeth for best occlusal contacts

62 Protrusive Records Protrude a minimum of 5-6 mmProtrude a minimum of 5-6 mm Ease of determinationEase of determination Protrude less than 12 mmProtrude less than 12 mm Maximum travel of the condylar element on most articulatorsMaximum travel of the condylar element on most articulators

63 Protrusive Records Registration material over entire rimRegistration material over entire rim Patient closes with mandible positioned anteriorlyPatient closes with mandible positioned anteriorly

64 Protrusive Records Material must interdigitate with the opposing “V-shaped” notchesMaterial must interdigitate with the opposing “V-shaped” notches Record should cover entire rim surfaceRecord should cover entire rim surface

65 Protrusive Records Condylar elements are released from hinge positionCondylar elements are released from hinge position Instrument protruded, and the rims closed into recordInstrument protruded, and the rims closed into record

66 Adjust Protrusive Guide for Maximal Interdigitation

67 Setting Condylar Angle

68 Protrusive Records The lateral component of condylar guidance (Bennett Angle) can be set arbitrarily at 15°

69 Protrusive Records Monoplane Occlusion Protrusive record may be omittedProtrusive record may be omitted If not obtained, set condylar guidance to 0°If not obtained, set condylar guidance to 0°

70 Protrusive Records Monoplane Occlusion May be advantageous to alter the occlusal plane angle in patients with steep condylar guidanceMay be advantageous to alter the occlusal plane angle in patients with steep condylar guidance Improves denture stabilityImproves denture stability Cannot be assessed if the condylar guidance has not been setCannot be assessed if the condylar guidance has not been set

71 Maxillomandibular Records for Complete Dentures Centric RelationCentric Relation Treatment positionTreatment position Operator assists to ensure a hinge positionOperator assists to ensure a hinge position Patient stops closure at initial contactPatient stops closure at initial contact ProtrusiveProtrusive Programs articulator to optimize occlusionPrograms articulator to optimize occlusion


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