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Jaw relation

  1. 1. CLASSIFICATION OF JAW RELATIONS : 1.Orientation relations establish the references in the cranium 2.Vertical relations establish the amount of jaw separation allowable for use for dentures 3.Horizontal relations establish front- to-back & side-to-side relations of one jaw to the other
  2. 2. Once you have accepted an impression, it will be packaged and sent to the Laboratory for fabrication of the: 1- Master Cast 2- Trial Denture Base with an Occlusion Rim
  3. 3. If the jaw relations are incorrect, the dentures will move in order to occlude with each other and – will subsequently be dislodged from the ridges during function.
  4. 4. ORIENTATION RELATIONS : 1. Occlusal plane orientation 2. Cranio-maxillary orientation, recorded either by: A. Following BONWILL triangle, or B. Using face-bow transfer with adjustable articulator
  5. 5. 1. OCCLUSAL PLANE ORIENTATION Occlusal plane represents the mean of the curvature of occlusal surfaces of teeth.
  6. 6. The Occlusal Plane
  7. 7. Factors affecting the orientation of Occlusal plane : 1. Esthetics A. Height of occlusal plane, ( interiorly ). B. Camper’s line , ( posteriorly ) C. Linea alba ( recently edentulous pt ) 2. Functions: Relation of occlusal plane to lower lip & tongue : A. Phonetics- production of F ,V ,PH sounds B. Chewing- the plane is below greatest convexity of tongue 3. Parallelism -parallel to both ridges 4. Anatomical factors A. Upper arch, no specific landmarks posteriorly B. Lower arch, ( Corner of the mouth & Retromolar pad )
  8. 8. Anteriorly : Occlusal plane parallel to interpupillary line Posteriorly : Occlusal plane parallel to ala-tragus line (Camper’s line) runs from inferior border of ala of nose to superior border of tragus of the ear
  9. 9. The Occlusal Plane Retromolar Pad
  10. 10. The Occlusal Plane Retromolar Pad
  11. 11. The Occlusal Plane Position of Anterior Teeth dictated by Esthetics and Phonetics
  12. 12. The Occlusal Plane Camper’s Line
  13. 13. The Occlusal Plane Retromolar Pad
  14. 14. Linea alba is hyperkeratinized zone occurs at level of occlusal interdigitation ( a landmark to verify occlusal plane ) Lower occlusal plane when projected behind must extend to the level between posterior 1/3 & anterior 2/3 retromolar pad
  15. 15. Characteristics of an ideal record base: - Strength and rigidity 1- Accuracy, The record base should not rock on the cast 2- Smooth, rounded well polished borders - Thickness of borders and palate must resemble those of the finished dentures 1- Palate must be 1-2 mm thick 2- Contour of the denture borders are defined by the land area of the master cast. 3- Record base must not extend onto land area of the cast
  16. 16. Completed record base check list: - Palate should be 1-2 mm thick and well adapted - Retromolar pad area is covered - Polished peripheries and palate - No porosity or voids - Flanges smooth and rounded -Tissue surfaces are well adapted Posterior aspect of upper rim can contact ascending ramus. If undetected, it can prevent accurate CR or sufficient freeway space to be obtained
  17. 17. Level of upper occlusal plane is a matter of judgement ( 2mm below lower margin of resting upper lip Occlusal plane guide ( Fox plane )
  18. 18. Occlusal plane must be parallel to ala-tragus line . Occlusal plane guide provides a useful method to asses the position of occlusal plane in relation to the face
  19. 19. Level of occlusal plane 1. It is located at the midpoint of interarch distance 2. Upper occlusal rim must be reduced 2mm below level of upper lip during speech . 3. Lower occlusal rim must be at level of lower lip & angle of the mouth. Posteriorly , it must be 2/3 height of retromolar pad.
  20. 20. Tentative occlusal plane is adjusted even after mounting on the articulator . Ideally , if it is parallel to upper & lower alveolar ridges, the denture will gain optimum stability
  21. 21. Too high occlusal rim ,hard to position food on occlusal surface
  22. 22. 1. A little lower occlusal plane with short lips 2. A little higher occlusal plane with long lips & in the elderly
  23. 23. Nasolabial angle of 90 is desirable depending on prominence of columella
  24. 24. Upper record block providing inadequate support to the upper lip –nasolabial angle is obtuse. Addition of wax to the labial face of the upper record block providing more support for the upper lip –nasolabial angle is 90º.
  25. 25. II VERTICAL RELATIONS Vertical dimension It is the vertical measurement of the face between any 2 points located , one above and one below the mouth ,in the midline
  26. 26. VERTICAL DIMENSION OF OCCLUSION- VDO It is the vertical dimension of the face when the teeth or occlusion rims are in contact in centric occlusion It is the position which must be determined before teeth arrangement & which must be established on articulator
  27. 27. VERTICAL DIMENSION OF REST- VDR It is the vertical separation of the jaws or the vertical dimension of the face when the teeth are not in contact & the mandible is in physiologic rest position. VDR is used clinically as a reference position to determine VDO of all prosthetic restorations :
  28. 28. Interocclusal distance ( freeway space) The distance between occluding surfaces of upper & lower teeth when the mandible is in its physiologic rest position Significance : 1. Relaxation of masticatory apparatus 2. Minimal activity in elevator & depressing muscles 3. No strain on TMJ capsules 4. Essential for the Health of periodontal tissues when natural teeth are present
  29. 29. Variability of rest position Due to hypotonicity & hypertonicity of muscles # Short term variables affected by 1. head posture 2. stress 3. extraction of teeth # Long-term variables are affected by 1. age & health status 2. bruxism
  30. 30. Upper lip area protrudes 4-6mm II Forehead, base of nose, chin are in line 2-4mm I Chin protrudes & upper lip area retrudes 0-2mm III
  31. 31. • Vertical dimension at Rest (RVD) • Vertical dimension at Occlusion (OVD) • Free Way Space (FWS)
  32. 32. Interocclusal distance : FREEWAY SPACE “VDR“-VDO” ” Distance between occluding surfaces of maxillary and mandibular teeth when the mandible is in its physiologic rest position Interocclusal distance
  33. 33. Reduction of freeway space results in : 1. Excessive loading of denture bearing tissues 2 . Elevator muscles are unable to return to their normal resting length 3 . Continuous muscular activity results in pain Increasing of freeway space results in : 1. Reduction of masticatory efficiency 2. Poor facial appearance & cheek biting 3. developing symptoms related to TMJ
  34. 34. Patient appeared as an Angle’s class III malocclusion & but this is caused by overclosure of the dentures
  35. 35. Overclosure of dentures
  36. 36. OVD is too great , face looks distorted & lips are incompetent OVD is too small , vermilion border appears thin & wrinkles occur around lips & protruded chin
  37. 37. Both patients are wearing CDs which are in occlusion facial appearance shows excessive VDO a gross loss of VDO freeway space is approximately 10mm
  38. 38. Excessive freeway space corrected VDO
  39. 39. Failure to provide an adequate VDO results in the anterior lower ridge assuming a more labial relationship to the upper ridge
  40. 40. Etiology: riboflavin deficiency, overclosure from loss of vertical dimension, oral skin bacteria and fungi (namely Candida)
  41. 41. METHODS OF DETERMINING VDR : 1. Esthetics, ( lips, angle of the mouth, labiomental angle ) 2. Phonetics 3. Patient’s tactile sense 4. Swallowing and Relaxation 5. Facial measurements (A) willi’s Measurements (B) Two dots technique 6. Electromyography
  42. 42. VERTICAL DIMENSION 1.Facial Measurements : -- patient sits comfortably, looking straight ahead -- insert maxillary record base -- place point of reference on nose & chin -- instruct patient to wet lips and swallow -- mandible comes to rest position -- measure the distance between reference points 2. Tactile Sense- where patient feels most comfortable 3. Phonetics- Repeat the letter “mm-mm” and relax 4. Facial Expression- recognize patient’s relaxed rest position 5. Anatomic landmarks- average measurements, *No one method for determining rest position can be accepted as being valid for all patient’s
  43. 43. Correct VD as the lips contact each other lightly before wax rims contact when the mouth is closed VD affects lips appearance: amount of vermilion border that is visible ,folds of corners Equal proportions of the forehead & middle of the face & lower face
  44. 44. WAX RIM CONTOUR Before adjustment After adjustment With lips at rest, wax rim must project 1-2 mm below the lip line.
  45. 45. Upper record rim trimmed well to provide a good labial support, that results in a more pleasing appearance
  46. 46. Pair of dividers will measure the distance between dots marked on the nose & chin
  47. 47. Methods of determining VDO 1. Pre-extraction records : a) Willi’s gauge b) Profile tracing c) Face masks d) Articulated study casts e) Profile photograph f) Radiogragh 2. Measurement of former denture 3. Power point ( BOOS Bimeter ) 4. Phonetics “ closest-speaking space “ 5. Ridge relationship
  48. 48. Willis gauge measures VDO before extraction & records the distance on the pt.’s chart for future reference
  49. 49. Effects of excessively increasing the VD (Over opening ) 1. Discomfort 2. Trauma 3. Instability 4. Loss of free way space 5. Clicking teeth 6. Appearance Effects of excessively reducing the VD ( Over closure ) 1. Appearance ( poor esthetics ) 2. Inefficiency 3. Cheek biting 4. Angular cheilitis 5. Pain in the TMJ 6. COSTEN’S Syndrome
  50. 50. 1. 1-Insufficient 2-Correct 2. 3. VD ,as pt. closes from rest position ( overclosure ) VD ,lips touch one another easily & naturally 3-Excessive VD, difficult to bring the lips together ( overopening )
  51. 51. HORIZONTAL RELATIONS CR & CO Significance of recording CR Eccentric relations
  52. 52. Significance of CR 1.CR is a definite learned position. 2.Pt. can voluntarily & reflexly return to this position. 3.CR can be recorded & repeated. 4.CR is a reference position in recording jaw relations & a starting point to develop occlusion. It is a point of return. 5.Edentulous pts. use CR in mastication & other mandibular activities ( such as swallowing). 6.Most of proprioceptors guiding the mandible in CO are lost in edentulous pt. So, opposing artificial teeth contact in CR due to loss of these guiding influences.
  53. 53. 7.CR can be verified 8.Occlusion is more stable if teeth occlude when the jaws are in CR. 9.Harmonizing CO to the established CR will arrange the teeth to meet evenly on both sides of dental arch during function. If we fail to register this CR, we build into our restorations premature contacts that will be very traumatic to the supporting structures 10.CR must be recorded correctly to permit accurate adjustments of condylar guidances for other eccentric movements . 11.CR is the only relation that can be repeatedly duplicated during treatment. 12.CR is prosthetically convenient.
  54. 54. Methods of recording CR : 1- Interocclusal check record method 2- Graphic methods 3- Functional methods ( chew-in method ) The primary requirements for making CR record: 1. Record horizontal relation of mandible to maxilla at proper VDO. 2. Exert equal vertical pressure while making the record. 3. Avoid distortion of record until casts are accurately mounted. 4. CR record can be repeated or verified
  55. 55. Interocclusal check record method
  56. 56. The commonly used materials for making interocclusal record are : wax, impression compound, ZOE and impression plaster
  57. 57. Graphic methods: Gothic arch tracers : 1. Extra oral tracers. 2. Intra oral tracers.
  58. 58. Extra oral Gothic arch tracer
  59. 59. Intra oral Gothic arch tracer
  60. 60. Obtaining a gothic-arch tracing intraorally
  61. 61. Functional methods ( chew-in method ) Require a tentative interocclusal wax record of CR at tentative VDO. Adjust recoding media at VD in excess to predetermined VDO. Correct VDO is obtained as pt. closes the jaws Patterson’s Method: -Trench or trough is made in lower occlusal wax rim -Abrasive-plaster mix is loaded into trench -Occlusal rims inserted & pt. performs mandibular movements to have compensating curves on abrasive-plaster mix Plaster-pumice rim with occlusal height greater than recorded height for wax rim
  62. 62. Jaw Relation Stage
  63. 63. Tooth Position Resting lip line. Smiling line. Speaki ng line.
  64. 64. High lip line: The greatest height to which the lip is raised in normal function or during the act of smiling broadly. Low lip line: The lowest position of the inferior border of the upper lip when it is at rest, OR, the lowest position of the superior border of the lower lip during smiling or voluntary retraction.
  65. 65. Horizontal relation • Types: A) Centric relation • Def, significance, ms involvement, • Relation C R to: vertical relation, hinge axis, centric occlusion • Complication in recording C.R. • Methods aid pt. to retrude mandible • Factors affect equalization of pressure • Methods of recording C R: • 1.Direct check bite method (wax wafer) • 2.Function methods: pumice& plaster, three studs, in wax ,petterson, Ganathodynmeter) • 3.Physiologic method • 4. Gothic arch method (intraoral& extraoral • 5.Recording condylar path( Stereographic& pantographic tracing • 6.Cephalometeric & ms conditioning