Simulation of occlusion in Restorative Dentistry

1. Simulation of occlusion in Restorative Dentistry 가천의대 길병원 치과센터 보철과 송승헌

2. 1.Fuctional of the Masticatory Organ

3. 1.Fuctional of the Masticatory Organ 1. chewing function 2. non-masticatory action ; verbal and non-verbal communication(facial musculature and the masticatory apparatus)

4. 1.1 Physiologic Function • occlusion ; any contact between maxillary and mandibular teeth • static occlusion; tooth contact without mandibular excursion • maximum intercuspation ; maximum interlocking of upper and lower cusps in static occlusion • habitual occlusion ; the static occlusion a persons’s teeth normally assume.

5. Under normal circumstance, habitual occlusion is identical with maximum intercuspation and the most cranial mandibular position as determined manually by dentists and dental technicians when positioning diagnostic cast • However, some patient are unable to achieve maximum intercuspation of mandibular and maxillary teeth ; either the habitual occlusal position does not correspond to maximum potential registration of the teeth rows, or diagnostic indicate different matching at “maximum” intercuspation

6. ‘Centric relation(CR)’ the foremost, upmost and midmost position of both condyles given a physiologic condyle-to-disc relationship and physiologic load application to the tissue involved • ‘Centric occlusion’ when combined with maximum intercuspation, this centric condyle position • ‘centric contact position’ Initial tooth contact in the centric condyle position

7. ‘hinge axis’ Fixed rotational axis involved in the opening and closing the mandible • ‘centric hinge axis’ The hinge axis determined in the centric condyle position • ‘hinge axis path’ Three-dimensional path of motion of the hinge axis in a skull-based coordinate system at the point of registration

8. ‘Condylar path’ Three-dimensional path of movement of the condyle in a skull-based coordinate system • ‘protrusion’ Every ventral movement of the mandible • ‘retrusion’ Every dorsal movement of the mandible • ‘mediotrusion’-movement of one side of the mandible • ‘mediotrusive side’- toward the medianplane • ‘laterotrusion’-movement aways from the median plane toward the laterotrusive side

9. ‘Bennett movement’ • lateral shift in the laterotrusive condyle • “immediate side shift” plus the “angle measured in the horizontal plane between the sagittal line and a line connecting the starting point to each point on the mediotrusive path of the condyle”– i.e. the bennett angle • Excursion of these mandibular movements in occlusion –dynamic occlusion

10. Incisal guidance Dynamic occlusion between anterior maxillary and mandibular teeth only • Canine-guided occlusion Guidance by canine only • Group guidance gliding contact(dynamic occlusion) of several teeth at the laterotrusive side

11. 1.2 Pathologic Function • Non-occlusion Lack of opposing contact and may thus involved single teeth, groups of teeth or entire sides of the dental arch • Premature contact the tooth or group of teeth with first contact during jaw closure • Condyle luxation movement of the condyle up to the articular tubercle and its retention in that position • Condyle hypermobility self-repositioning form of this disturbance

12. Disc dislocation - all non-physiologic disc to-condyle relation - Partial or total - Non-repositioning or self-repositioning - May occur either at maximum intercuspation or during excursive movement

13. Non-physiologic mandibular movement 1. limitation any restriction of physiologic mandibular movement due to non-repositioning disc dislocation 2. Deviation shift of the incisal point during mandibular movement with a return to the median plane 3. Deflection the same disturbance with non-repositioning of the incisal point to the median plane

14. 2. Diagnostics and Restorative Therapy To avoid unnecessary occlusal disturbance as well as any iatrogenic damage or exacerbation

16. 2.1 clinical examination • History • Oral inspection • Periodontal status • Condition of teeth and elementary occlusion status • Functional status of masticatory musculature and temporomandibular joints

18. 2.1.1 General History • One element common to most initial examination records • Mainly practical aspects and items of a general medical nature

19. 2.1.2 Special History • Pain, complaints, therapeutic wishes • Other discomforts in the cranimandibular and cranial area(valuable in diagnosis of functional disturbance)

20. 2.1.3 Extraoral Findings/Functional Analysis • Inspection for unusual swelling and odors, the functional analysis

21. Are the movement involved in opening and closing the mouth asymmetrical ? • Shifts to one or both sides with to the midline –deviation • Differentiated from shifts not followed by a return to the midline - deflection

22. Is the size of the oral aperture limited when intentionally opened? • Determined whether rotation and translation of the temporomandibular joint are hindered • General rule – more than 38mm

23. Do cracking or rubbing noises occur in the area of the temporomandibular joints • Differentiated as to their specific sound(rubbing or cracking), localization(left/rigt/bilateral), exactly when they occur during the particular movement(initial/intermediate/terminal) and the degree to which they can be influenced by specific application of pressure

24. Do asynchronous noises occur at gnathic closure? • In both habitual and centric occlusion, premature occlusal contacts cause asynchronous closure noises

25. Is palpation of the masticatory muscles painful? • the main chewing muscles m. masseter and m. temporalis anterior, digastric muscle(ventral, posterior) and the lateral pteygoid muscles

26. Is eccentric occlusion traumatic? • Pronounced facets of wear been formed due to parafunction habits and possibly leading to loss of canine-guided occlusion?

27. 2.1.4 intraoral finding /Oral Inspection • Oral inspection is openly and emphatically defined by US dentists as a cancer prevention measure ; function, sublingual space, buccal and pharyngeal space, soft tissue

28. 2.1.5 general Periodontal Finding

29. 2.1.6 Dental finding 1. Identification of carious lesions 2. Oriented occlusive pattern check(traumatizing contact) - check with thinnest occlusion, 8-10um thick, by having the patient make excursive and incursive movement -then making with a colored foil(red) -then preliminary centric contact can be detected -then habitual occlusion check(darker)

30. 2.1.7 Radiographic finding • Bite-wing X-ray – interproximal caries • Check for findings from other source and tentative dagnosis

31. 2.1.8 Tentative Diagnosis • Describes the situation of a “positive screening result before the results of more specific testing are available

32. 2.2 Concept for resotrative therapy • Dental technique used in treatment of functionallyphysiologic masticatory organs are also used in specific preliminary treatment of dysfunctonalmasticatory organs and in subsequent intergration of functionally adapted restoration

33. 2.2.1 Indication for restorative therapy • Indicate a probable dysfunction, no attempt should be made at restoration until a more specific examination • Latent dysfunction ; at first be left as the patient has tolerated it in the past. • the new restorations should be intergrated with an eye to functional harmonization

34. 2.2.2 Restoration Design • When it comes to material processing, both direct and indirect filling techniques are available • Direct fillings – include surface area and depth of the cavity - restricted to a maximum of 1/3 of the occlusal surface • Indirect fillings – extensive defect and weaken individual cusp - should be shortened and capped to avoid fracture

35. Critical weakening of the clinical crown due to deep plastic filling or enlargement of the preparation to cover more than 1/3 of the occlusal surface justifies the indication for a cast onlay

36. Avoid both static and dynamic occlusal contacts with the margins of the restoration • Broadened

37. Elastic deformation of the clinical crown and abrasion in dynamic occlusion by counterparts in the highs-stress posterior tooth area may also occurs.

38. purely occlusal restorations may fail due to secondary marginal defects, in patients with a tendency to bruxism • cover and surround the entire occlusal surface with cast restoration

39. ‘liberal’occlusion concept (interrelationships in static occlusion) • Harmonization of the habitual and centric condylar positions. • In full dentition, matching of the hinge axis position in habitual and centric occlusion at given points(“point centirc”) • Strict avoidance of premature contacts • Desirable cusp slope support pattern for occulsal contacts dictates bipodal or tripodal support at these points • Maxillary and mandibular incisors contacts should be “ as light as a feather”

40. Dynamic occlusion 1. canine-guided occlusion ; resulting in disclusion of all other teeth unilaterally balanced occlusion ; an occlusion concepts with guidance of all teeth on the laterotrusion side resulting in disclusion of all other teeth 2. anterior tooth protrusive movements are not necessary initial 3. absolute freedom from interference is necessary – at least within this narrow functional range

41. Requirements apply to restoration of posterior teeth with partial crown 1. within the framwork of therapeutic planning, evaluation of the interocclusal situation ; static occlusion, sufficient free guidance space in dynamic occlusion

42. Should avoidance of such balance contacts in dynamic occlusion lead to the loss of this support in static occlusion on the mediotrusive side, the therapeutic plan must include restoration of canine-supported occlusion

43. Balance contacts must be avoided entirely on the mediotrusive side

44. In posterior tooth preparations, sufficient amount of substance must be removed, in particular around the functional roof

45. “C-contacts” can be left out of consideration in static occulsion

46. In view of this situation, various authors have developed special wax buildup technique for additive ”programmed” design of functional occlusal surface • “harmony occlusion” ; by point-by-point matching of hinge axis position in habitual and centric occlusion(point centirc)

47. Wax buildup technique - by Thomas, Payne and Lundeen - modeling of steep-angle triangular ridges - it must be added that, using this method, interference free dynamic occlusion of the posterior teeth is feasible within narrow limits only

48. Biomechanical Wax Buildup technique(by Polz) - conventional triangular ridges– off near the cusp tips and an additional “backpack” in the central third of the triangular ridges - counterpart cusp is supported in static occlusion by the highly convex backpaks

49. If. Loss of anterior and canine-guided occlusion - lateral bruxism, premature contacts between posterior teeth occur on the laterotrusive side - additional balanced contacts can be expected on the mediotrusion side • avoid or eliminate these eccentric contact between posterior teeth with suitable new restoration designs Restoration of canine-supported occlusion

50. 2.3 Restoration-Material and Techniques