Verticle jaw rel challenge to dentist


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Verticle jaw rel challenge to dentist

  1. 1. INDIAN DENTAL ACADEMY Leader in continuing dental education
  2. 2. Recording correct vertical dimension in complete denture patients: a challenge!
  3. 3. • It is common to hear a wide variety of opinion as to where vertical dimension should be… and how to determine this position???
  4. 4.
  5. 5. • A crucial and debated aspect of CD construction is the determination of maxillo-mandibular relations especially VDO. Reasons…..
  6. 6. Variety of methods available. Methods are subjective rather than objective. None is documented to be ideal and perfect. Lacunae in every method. No objective method is universally accepted
  7. 7. • VARIOUS METHODS: • Mechanical Pre- extraction records • Profile radiographs • Casts of teeth in occlusion • Facial measurements
  8. 8. Ridge relation • Distance from the incisive papilla • Parallelism of ridges
  9. 9. • Physiological: Physiological rest position Swallowing phenomenon Phonetics Closing forces Tactile sense Patient reported sense of comfort
  11. 11. • Wright recommended the use of pre- extraction records/old photographs of patients in determining and establishing VDO .
  12. 12. • Boos determined VDO by measuring maximum biting force
  13. 13. Shpuntoff demonstrated that the muscles controlling the mandible become tense when any type of mechanical recording device is placed in mouth. Registration of mandibular position made under such circumstances would reflect the strain induced.
  14. 14. • Silverman used closest speaking space to determine VDO.
  15. 15. • Swerdlow believed that phonetic methods were consistently more reliable than the swallowing technique for determination of interocclusal distance.
  16. 16. • Shanahan used “ physiological method” of swallowing for determining VDO and centric relation.
  17. 17. • Physiologic rest position- main starting point used to measure VDO • VDR = VDO + IOG
  18. 18. • But the concept is unreliable for 2 reasons: 1.The rest position is not constant and continuously changes, and so it is not a logical baseline from which to measure the fixed dimension at maximum intercuspation. 2.The interocclusal freeway space is highly variable from one patient to another, and so there are no set dimensional relationships that could be used to find VDO even if the rest position could be determined with consistent accuracy.
  19. 19. • CONTROVERSY???
  20. 20. • CONCEPT OF CONSTANCY OF REST POSITION: Gillis (1941) “mandibular rest position is not artificially established. The interocclusal clearance averages about 3mm as measured at central incisors and doesn't vary greatly between different individuals” He defined rest position from which all mandibular movements begin and to which they
  21. 21. Niswonger postulated that rest position remains constant throughout life. Thompson (1954): “He stated “ the rest vertical dimension established by mandible in its rest position is greater than VDO and is constant in most instances regardless of the status of dentition” .
  23. 23. Loeff (1950): • Stressed that muscle tone rather than muscle length controls rest position and muscle tone can and does vary e.g muscle tone can be increased by exercise and decreased by rest.
  24. 24. Atwood (1950): • Performed a longitudinal radiographic analysis of face height before and after extraction in 42 subjects. He demonstrated variability within a sitting, between different sittings and readings with and without dentures. • When opposing occlusal contacts were removed there was a decrease in VDR. The degree of variability depended on relative values of and complete interplay of 30 influential factors
  25. 25. Duncan and Williams (1959): • Used lateral cephalometric measurement to study rest position as a guide in prosthetic treatment. A general decrease in height of face with mandible in rest position was observed on removal of occlusal contacts. • They concluded that rest position is a poor guide for establishing the vertical dimension of occlusion.
  26. 26. Perry (1956), Garvick (1962): • Studied EMG activity of facial muscle and also formed the concept of postural range. • Clinically recorded rest position is usually 2-3 mm below intercuspal position, doesn't correspond to that recorded in EMG activity. • EMG rest position is several millimeters lower than in the clinical rest position.
  27. 27. • Moreover certain measurements of vertical dimension and EMG study have shown that many slow changes in vertical dimension can occur without change in electrical activities of the muscle involved. • Thus, these research works favor the concept of postural rest position as a range of positions rather than a single and absolute one.
  28. 28. • Shephard and Shephard reported that the rest position of edentulous mandible tended to vary even over a short span of time following cephalometric examination. • Garnick and Ramrjord demonstrated a variation of 1.5mm in rest position in 13 of 20 subjects from start to finish of their experimental period(45 mints).
  29. 29. Thompson and Kendrick: demonstrated a significant change in both vertical dimensions within 1 year in all of their 71 participants.
  30. 30. • Balance of forces: • At any given point of time a balance between active and passive forces determine rest position of mandible.
  31. 31. • Passive forces: Elasticity of muscle fibers and connective tissue elements Emotions Posture Gravity Elastic property of capsule and ligament of TMJ
  32. 32. • Active forces:  Continuous low grade motor activity in muscles. Elevators show more such activity due to activation of stretch reflex and increased motor unit activity of mandible increases due to insertion of lower denture when mandible tends to drop and elevator muscles are stretched.  Changes in head and neck position  External factors (emotions, drugs)  VDR decrease by - adrenaline, caffeine  VDR increase by - barbiturates and during sleep
  33. 33. • This raises question against reliability of rest position in establishing VDO. • Still it is universally believed that when used properly mandibular rest position may help establish a satisfactory esthetic and functional VDO especially in edentulous patients.
  34. 34. • CONCLUSION: • There is no universally accepted method of determining VDO. • There seem to be no significant advantages of one technique but it is the end result that matters. • It should be satisfactory to the dentist and patient from esthetic point of view and not induce degenerative changes from a functional standpoint.
  35. 35. • Finding a reliable method to determine appropriate jaw relations has always been a goal of researchers in the field of CD Prosthodontics. • However, there has been a decline in scientific work in this aspect of prosthetic dentistry. This may be in part due to changing scenario with more clinicians preferring to practice implantology and ultra conservative restorative dentistry.
  36. 36. • However, in developing countries like India, much of Prosthodontic practice entails construction of complete denture. • Thus, basic concepts like vertical dimension still need to be developed and studied….
  37. 37.