Clinical analysis of occlusion

1. Clinical analysis of occlusion

2. Terminology Occlusion: This words is used to describe the static contact relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth

3. Terminology Articulation: Refers to the static and dynamic contact relationship of maxillary and mandibular teeth as they move against each other during function.

4. Terminology Balanced Occlusion: It refers to the bilateral, simultaneous, anterior, and posterior occlusal contact of teeth in centric and eccentric position.

5. Terminology Free Mandibular Movement: Any mandibular movement without interference.

6. Terminology Occlusal Harmony: A condition in centric and eccentric jaw relation in which there are no interceptive or defective contacts of occluding surfaces.

7. Terminology Occlusal Interference: Any tooth contact that inhibits the remaining occluding surfaces from achieving stable and harmonious contacts.

8. Terminology Occlusal Pattern: The form or design of the masticatory surfaces of a tooth or teeth based on natural or modified anatomic or non anatomic teeth

9. Terminology Maximal Intercuspal Position: The complete intercuspation of the opposing teeth independent of the condylar position.

11. Introduction Occlusion in complete denture must be developed to function effeciently and with the least amount of trauma to the supporting tissues.

12. Objectives • Preservation of the remaining tissues • Proper masticatory efficiency • Enhancement of denture stability, retention and support • Enhancement of phonetics and esthetics

13. Difference Between Natural and Artificial Occlusion • The teeth in natural dentitions are retained by periodical tissues that are uniquely innervated and structured. In complete artificial occlusion all the teeth are on bases seated on slippery tissues. • In natural dentitions the teeth receive individual pressures of occlusion and can move independently.

14. Difference Between Natural and Artificial Occlusion 3. Malocclusion of natural teeth may be uneventful for years. 4. Non vertical forces on natural teeth during function affect only the teeth involved and are usually well tolerated, whereas in artificial teeth the effect involved all of the teeth on the bases. It is usually traumatic to the supporting structures.

15. Difference Between Natural and Artificial Occlusion 5. Incising with the natural teeth does not affect the posterior teeth. Incising with artificial teeth affects all of the teeth on the base. 6. In natural teeth the second molar is the favored area for masticating hard foods. 7. In natural teeth bilateral balance is rarely found; If present it is considered balancing side interference.

16. Difference Between Natural and Artificial Occlusion 8. In natural teeth proprioception gives the neuromuscular system control during function.

17. Requirement of Complete Denture Occlusion • Stability of occlusion in centric relation. • Balanced for all eccentric contacts bilaterally for all eccentric mandibular movements. • Unlocking the cusp mesiodistally to allow for gradual but inevitable settling of the bases due to tissue deformation and bone resorption. • Control of horizontal forces by buccoligual cusp height reduction according to the residual ridge resistance and interridge space.

18. Requirement of Complete Denture Occlusion

19. Requirement of Complete Denture Occlusion 5. Functional lever balance by favorable tooth to ridge crest position

20. Requirement of Complete Denture Occlusion 6. Cutting and shearing effeciancy of the occlusal surface (sharp cusps or ridges) 7. Anterior clearance of teeth during mastication. Minimum occlusal contact between the upper and lower teeth to reduce pressure during function (linguilized occlusion)

21. Requirements for Incising Units These units should be sharp in order to cut effeciently. They should not contact during mastication. They should have as flat an incisal guidance as possible considering esthetics and phonetics. They should have horizontal overlap to allow for base settling without interference. They should contact only during prostrusive incising function.

22. Requirements for the Working Occlusal Units They should be effecient in cutting and grinding. They should have decreased buccal-lingual width to minimize the work force directed to the denture foundation. They should function as a group with simultaneous harmoniuos contacts at the end of the chewing cycle and during eccentric excursions.

23. Requirements for the Working Occlusal Units They should be over the ridge crest in the masticating area for lever balance. They should center the work load near the anteroposterior center of the denture. They should present a plane of occlusion as parallel as possible to the mean foundation plane.

24. Fundamentals for Artificial occlusion The smaller the area of the occlusal surface acting on food, the smaller will be the crushing force on food transmitted to the supporting structures. Vertical force applied to an inclined occlusal surface causes non vertical force on the denture base.

25. Fundamentals for Artificial occlusion Vertical force applied to a denture base supported by yielding tissue causes the base to slide when the force is not centered on the base. Vertical force applied outside (lateral to) the ridge crest creates tipping force on the base.

26. Balance occlusion Balance as related to complete denture occlusion: Balance occlusion in complete dentures can be defined as stable simultaneous contact of the opposing upper and lower teeth in centric relation position and a continuous smooth bilateral gliding from this position to any eccentric position within the normal range of mandibular function.

27. Balance occlusion Balance in complete dentures is unique and man made. The physical factors that apply to the relationship of the teeth to each other and that apply to the position of the teeth in the denture base as related to the ridge must be understood. The application of these physical laws can be expressed by the following:

28. Balance occlusion • The wider and larger the ridge and the closer the teeth are to the ridge, the greater the level balance. • Conversely, the smaller and narrower the ridge and the farther the teeth from the ridge, the poorer the level balance. • The wider the ridge and the narrower the teeth buccolingually, the greater the balance • The more lingual (inside) the teeth are place in relation to the ridge crest, the greater the balance

29. Balance occlusion 5. The more centered the force of the occlusion anteroposteriorly, the greater the stability of the base.

30. Types of Balance • Lever Balance – This is present when there is equilibrium of the base on its supporting structures when a bolus of food is interposed between the teeth on one side and a space exist between the teeth on the opposite side. This state of equilibrium is encouraged by the following: 1. Placing the teeth so that the resultant direction of force on the functioning side is over the ridge or slightly lingual to it.

31. Types of Balance 2. Having the denture base cover as wide an area on the ridge as possible. 3. Placing the teeth as close to the ridge as other factors will permit. 4. Using as narrow a buccolingual width occlusal food table as practical.

32. Types of Balance (b) Occlusal Balance Bilateral occlusal balance – this is present when there is equilibrium on both sides of the denture due to simultaneous contact of the teeth in centric and eccentric occlusion. It requires a minimum of three contacts for establishing a plane of equilibrium.

33. Types of Balance c)Protrusive occlusal balance – this is present when the mandible moves essentially forward and the occlusal contacts are smooth and simultaneous in the posterior both anterior teeth. It is slightly different from bilateral balance in that it requires a minimum of three contacts, one on each side and one anterior, and is dependently on the interaction of the same factors.

34. Types of Balance This total concept of balanced complete denture occlusion must be considered in terms of the following: • The tooth size and position in relation to the ridge size and shape. • The extent of denture base coverage. • Occlussal balance with stable contacts at the retruded border position and in an area (long centric)

36. Types of Balance • N.B. – In both natural and artificial dentition, when centric relation and centric occlusion do not coincide, it is desirable to create an area within the fossae that will allow freedom of tooth movement from centric relation to centric occlusion (this is called long centric or freedom in centric)

37. Types of Balance 4. Right and left eccentric occlusal balance by simultaneous contacts at the limit of functional and parafunctional activity. 5. Intermediate occlusal balance for all positions between centric occlusion and all other functional or parafunctional excursion to the right, left and protrusive.

38. Advantages of Balanced Occlusion • Distribution of load • Stability • Reduced trauma • Functional movement • Efficiency • Comfort

39. Factors Affecting the balanced occlusion (Laws of Articulation Hanau quint) There are five factors involved in eccentric occlusal balance in complete dentures. • Condylar guidance • Incisal guidance • The occlusal plane • The compensatory curves • Cusp angulation

40. Condylar guidance – it is definite anatomic feature that depends on the inclination of the floor of the glenoidfossa. It should be determined on the patient and set on the articulator by eccentric records so that the patients TMJ is in harmony with the occlusion programmed on the articulator. If the condylar angle (angle between the path of condyle and the Franfort horizontal plane) is steep, its difficult to produce balance occlusion because when the condyle travel downward and forward large space is created posteriorly when the anterior teeth are edge to edge. So compensation should be made by altering the other factors to otain the desired balanc.

41. 2. Incisal guidance – Incisal guidance is the effect of the contact of the upper and lower anterior teeth on the movement of the mandible. It is usually expressed in degrees of agulation from the horizontal by a line drawn in the sagittal plane between the incisal edges of the upper and lower incisor teeth when closed in centric occlusion. If the incisal guidance is steep, it requires steep cusp, a steep occlusal plane, or a steep compensating curve to effect an occlusal balance.

42. Factors affecting the incisal guidance angle. 1. Vertical overlap (over bite): the vertical overlap is directly proportional with the incisal angle. For complete dentures the incisal guidance should be as flat as esthetic and phonetics will permit.

43. For the following reasons: 1. To guard against loss of posterior teeth contact during prostrusive movement. 2. To allow the use of posterior teeth with reduced cusp angle and this will reduce the lateral stresses transmitted to the ridge. 3. To reduce the downward movement of the mandible during edge to edge position.

44. The incisal guidance is reduce by: • Setting the upper anterior teeth outside the ridge • Setting the lower anterior teeth inside the ridge without encroaching on the tongue space • Shorten the upper and lower anterior, if esthetics and phonetics allows.

45. When the arrangement of the anterior teeth necessitates a vertical overlap, a compensating horizontal overlap should be set to prevent anterior interference.

46. 3. Plane of Occlusion – the occlusal plane is established in the anterior by the height of the lower cuspid, which is nearly coincident with the commissure of the mouth, and in the posterior, by the height of the retromolar pad. It is also related to the related to the ala-tragus line. Its role is not as important as are the other determinants.

47. 4. Compensating curves -- Compensating curve is one of the more important factors in establishing a balanced occlusion so that the occlusal surface results in a curve that is in harmony with the movement of the mandible as guided posteriorly by the condylar path. A steep compensating curve for occlusal balance. A lesser compensating curve for the same condylar guidance would result in a steeper incisal guidance (anterior interference), which would cause loss of molar balancing contacts.

48. Height of cusps on teeth or inclination of cusp less teeth. Cusp angle – the angle made by the slopes of a cusp with a perpendicular line bisecting the cusp, measured mesio-distally or buccolingullay. Cusp Height – the shortest distance between the tip of a cusp and its base plane. Altering the cusp height by widening or narrowing a tooth alters the length of the cusp incline but does not change the relationship to the mean occlusal plane, i.e. cusp angle is not affected by a change in cusp width.

49. when we select a tooth with a certain xusp height or angle, it doesn’t mean anything until the tooth is positioned in the denture. For example, a particular tooth may be manufactured with a 30 degree inclination. However, by tilting the tooth in relation to the mean occlusal plane, one may create an effective inclination of greater or less than 30 degrees.

50. Interaction of the five factor Of the four that he can control two of them (the incisal guidance and the plane of occlusion) can be altered only a slight amount because of esthetic and physiologic factors. The important working factors for the dentist to manipulate are the compensating curve and the inclinations or cusp on the occlusal surfaces of the teeth.