1. Maxillo-Mandibular Relationships
Centric and Protrusive Records
This presentation includes images from the UCLA/APC/Ivoclar Educational Curriculum

2. No Easily Determined Reference Position
Unlike dentate patient where existing teeth establish:
Vertical height
Position of maximum intercuspation
Fine sensory input to find maximum intercuspation

3. Require a Reference Position to Set Teeth
When remove dentures, no easily determined position to set teeth
Differences in dentures and wax rims confuse some patients
Without rims, no way to record centric position

4. Difficulties Maxillo-mandibular Relationships
Difference in sensation (no teeth, changed lip support, height, contact with tissue)
Edentulous patients have more difficulty determining where their teeth should contact
No periodontal membrane

5. Finding a Treatment Position
Acceptable position should be:
Conducive to health
Relatively repeatable
position should be checked before dentures completed

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

7. Centric Relation (CR) Treatment Position
Centric position of mandible to maxilla
Defined by position of condyles, not teeth
Hinge position

8. Hinge Position is Repeatable
Relatively centered
Patient can find stable occlusal contacts easily
Allows change in vertical dimension

9. Centric Relation Treatment position
Not necessarily ‘ideal’ or ‘normal’

10. Centric Occlusion (CO)
Occlusion of opposing teeth when mandible in centric relation
Treatment position for Complete Dentures
Sometimes coincident with ‘maximum intercuspation’ in natural dentitions

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

12. Where is Centric Relation? Glossary of Prosthodontic Terms:
Independent of tooth contact
Clinically discernible when mandible is directed superiorly and anteriorly

13. Where is Centric Relation?
Glossary of Prosthodontic Terms:
Anterior-superior position against slope of the articular eminence

14. Where is Centric Relation? Glossary of Prosthodontic Terms:
Purely rotary movement about transverse horizontal axis

15. Why Anterior-Superior?
Thickening (buttressing) bone is present where joint articulation occurs
Thickest part of eminence is anterior portion of fossae

16. Why Anterior-Superior?
The articular disk is in a anterior-superior position

17. Why Anterior-Superior?
Cartilage covers articular surfaces
Fibrocartilage on anterior surface of glenoid fossae
Articular cartilage on superior and anterior of condyles

18. Why not Posterior Position?
Neurovascular supply of retro-discal pad is posterior to disk
If condyles articulated in a posterior position – impingement

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

20. Clinically dentist cannot determine actual position of condyles at time of jaw relations records

21. 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 CR=CO

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

23. 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)

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

25. When to Use Centric Relation
When entire occlusion being restored
No remaining posterior centric stops
When complete, fixed, or removable partial dentures involve entire occlusion

26. When to Not to Use Centric Relation
Stable occlusion
No pathology
Posterior centric stops present
No valid reason to change
Use maximum intercuspation

27. Patient Position Centric Relation
Patient in a slightly supine position

28. Stabilizing the Record Bases
Occlusion rim notched to aid stabilization

29. Centric Relation Bimanual Manipulation
Index fingers on the rim, thumbs under symphysis

30. Maxillo-Mandibular Relationships
Centric and Protrusive Records

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

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

33. Registering Centric Relation
Minimal closing pressure
(Yurkstas and Kapur)

34. Recording Centric Position

35. 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

36. Line up Marks Eliminate all contact with record bases
Must only be wax rim to wax rim contact

37. Videos
Centric Record
Mount Mandibular Cast

38. Review of Centric Record Procedure

39. Reference Notches In Wax Rims
Two sharp “V”-shaped notches in molar/premolar region of each side
Depth: 1-2 mm
1-2 mm

40. Ensure Proper Notches
Too Shallow
- no undercuts

41. Registering Centric Relation
Rehearse making record without recording medium
Place occlusion rims intraorally
PVS registration material over entire occlusal rim

42. Thin Layer of Material
Too Thick
Good

43. Thin Layer Want flat record, no excess on sides of rims
Material over sides of rim can cause deflection when checking record

44. Stabilize the Mandibular Record Base
Index fingers on flange (or recess in rim), thumbs under symphysis

45. Patient Active, Dentist Guides
Patient opens, relaxes,
and slowly closes

46. Recording Should Feel Relaxed
Gently arc mandible in a hinge-like motion
There should be NO:
Translation
Muscle splinting

47. If Mandible Has Retentive Rim or Natural Dentition
Implants, single denture, very retentive record base
Don’t need to stabilize
Operator places hands extraorally
Ensure no translation

48. Patient Instructions
Close until rims are almost touching (1 mm separation)
Stop as soon as this position has been reached
Some patients may not be able to determine contact

49. Patient Instructions Never instruct patient to bite firmly
Can cause translation or inaccuracy

50. Ensure Accurate Record
Keep hands on mandible to ensure no translation during setting
Hold position until set 1-2 min
Remove both rims together
Separate rims

51. Ensure Accurate Record
Registration Should be Sharp, Not Rounded
Ensure record is repeatable by repeating with record in place
If not repeatable, take another record and check repeatability again prior to mounting

52. Checking Centric Record
Have patient close into record
Ensure smooth arc of closure, no horizontal deviations
Use index fingers to stabilize lower record base

53. Prior to Mounting Mandibular Cast
Ensure
Only wax-rim to wax-rim contact
Casts should not contact
Record bases should not contact
If other contacts, mounting will be incorrect

54. Mounting Mandibular Cast
Stabilize wax rims together with
sticky wax and sticks
sticky wax directly - 4 spots
Critical for accurate mount

55. Mounting Mandibular Cast
Use mounting plaster
After set, remove record & adjust incisal pin to allow contact between rims
Occlusion rims should be touching evenly, over entire occlusal surface

56. Registering Centric Relation
Do not alter incisal pin after rims contact
Otherwise, height of correct vertical dimension can be lost

57. Take New Record to Check CR
Take new record, place on articulator
Release articulator centric locks
Should arc into record without any translation
If not the same, take 3rd record to see which one is reproducible

58. Protrusive Records Used to set condylar guidance
Helps setting teeth for best occlusal contacts

59. Amount of Protrusion Protrude a minimum of 5-6 mm
Ease of determination
Protrude less than 12 mm
Maximum travel of the condylar element on most articulators

60. Protrusive Records Close w. mandible positioned anteriorly
Posterior separation critical to capture
Not repeatable – determined by amount of protrusion

61. Record Requirements
Material must interdigitate with the opposing “V-shaped” notches
Record should cover entire rim surface

62. To Set Condylar Inclination
Condylar elements unlocked
Instrument protruded, rims closed into record
Only wax-rim to wax-rim contact on articulator – otherwise can’t set properly

63. Adjust Protrusive Guide for Maximal Interdigitation

64. Protrusive Record Video

65. Protrusive Records
Lateral component of condylar guidance (Bennett Angle) set arbitrarily at 15°

66. Protrusive Records Monoplane Occlusion
Protrusive record still required
Allows observation of posterior disclussion

67. Protrusive Records Monoplane Occlusion
May be advantageous to angle occlusal plane angle in patients with steep condylar guidance
Improves denture stability
Cannot be assessed if condylar guidance has not been set

68. Maxillomandibular Records for 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