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MaxilloMandibular Relationships

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Problems Establishing Edentulous Maxillo-mandibular Relationships ... Jiggle the mandible. Mandible should freely arc. Allow the patient to close into contact ... – PowerPoint PPT presentation

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Title: MaxilloMandibular Relationships


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
    contact
  • No periodontal membrane
  • Old dentures wont fit on casts
  • Record base fit and wax rim changes confuse some
    patients

3
Centric Position
  • Acceptable position should be
  • Conducive to health
  • Relatively repeatable
  • position can be checked before dentures completed

4
Conducive to Health
  • Relatively Symmetrical Position
  • Not absolute symmetry
  • Less chance of muscle strain which might occur in
    non-centered positions

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

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

7
Centric Relation
  • Treatment position
  • Not necessarily ideal or normal

8
Centric Occlusion (CO)
  • Maxillo-mandibular position determined by teeth
  • 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 contact
  • Clinically discernible when the mandible is
    directed superiorly and anteriorly

11
Where is Centric Relation?
  • 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 axis

13
Other definitions of centric relation have
included
  • Rearmost, Uppermost, Midmost (RUM)
  • Most 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 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 disk
  • If condyles articulated in a most posterior
    position impingement

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

19
Anterior-Superior Position
  • Posterior-most positions require force
  • Pressure 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 positions
  • Conducive to health (non-pathologic)
  • Brill et al - pain loss of occlusal sense when
    not in CR
  • Renyolds - 24 of normal population has CRCO

23
Centric Relation - Why?
  • Convenient - relatively centered (Celenza)
  • More reproducible (Grasser)
  • Easier 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)
  • 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
    position
  • No habitual position with new wax rims
  • (Crum and Loiselle Brill et al)

26
Centric Occlusion - Why Not?
  • CO may be a dysfunctional position
  • 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 consistency
  • Biting force
  • Symmetry 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 restored
  • No remaining posterior centric stops
  • When complete, fixed, or removable partial
    dentures involve the entire occlusion

30
When to Not to Use Centric Relation
  • Stable occlusion
  • No pathology
  • Posterior centric stops present
  • No valid reason to change
  • Use 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 bases

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

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

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

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

37
Recording Centric Position
38
Preparing Occlusion Rims
  • Place 3 widely separated lines between the rims
    in the centric position
  • CRITICAL! Check that record base heels/rims do
    not touch

39
Line up Marks
  • Eliminate 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 wax
  • Depth 1-2 mm

41
Ensure Adequate Notch Depth
  • Too Shallow

- no undercuts
42
Registering Centric Relation
  • Rehearse making the record without recording
    medium
  • Place occlusion rims intraorally
  • PVS 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 rims
  • Excess material recording of the sides of the rim
    can cause deflection when checking record

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

46
Alternate Medium
  • Alluwax
  • Must be dead soft

47
Registering Centric Relation
  • Place Alluwax into a 1-2mm slot in maxillary rim
  • Fill to slight excess
  • Ensure wax is dead soft
  • 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 motion
  • There should be
  • No translation
  • No splinting

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

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

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

55
Registering Centric Relation
  • Hold position until set 1-2 min
  • Remove both rims together
  • Separate

56
Registration Should be Sharp, Not Rounded
57
Registering Centric RelationMounting the
Mandibular Cast
  • Ensure record is repeatable
  • Increase the height of incisal pin 1 mm, invert
    articulator
  • Place wax rims together, lute with sticky wax - 4
    spots

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

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

60
Check CR Record
  • Take new record, place on articulator
  • Release articulator centric locks
  • Should arc into record without any translation
  • If doesnt take 3rd record to see which one is
    reproducible

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

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

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

64
Protrusive Records
  • Material must interdigitate with the opposing
    V-shaped notches
  • Record should cover entire rim surface

65
Protrusive Records
  • Condylar elements are released from hinge
    position
  • Instrument 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 omitted
  • 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 guidance
  • Improves denture stability
  • Cannot be assessed if the condylar guidance has
    not been set

71
Maxillomandibular Recordsfor Complete Dentures
  • Centric Relation
  • Treatment position
  • Operator assists to ensure a hinge position
  • Patient stops closure at initial contact
  • Protrusive
  • Programs articulator to optimize occlusion
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