Occlusion in dentistry

Occlusion in dentistry is so important to be understood in its full perspective.

1. OCCLUSION IN DENTISTRY PRESENTED BY – DR. ANAMIKA ABRAHAM GUIDED BY – DR. DESHRAJ JAIN

2. TABLE OF CONTENTS DEFINITIONS THERAPEUTIC AND PHYSIOLOGIC OCCLUSION IDEAL OCCLUSION CONCEPTS OF OCCLUSION BILATERAL BALANCED UNILATERAL BALANCED/ GROUP FUNCTION CANINE GUIDED OCCLUSION BASICS FROM DENTAL ANATOMY IMPORTANCE OF OCCLUSION IN PEDODONTICS ORTHODONTICS ORAL SURGERY RESTORATIVE DENTISTRY PERIODONTICS PROSTHODONTICS TYPES OF OCCLUSAL ERROR AND ITS CORRECTION PATHOGENIC OCCLUSION CONCLUSION REFERENCES

3. Key terms & Definitions Occlusion: is derived from the Latin word “ Occlusio ” meaning act of closure or being closed. According to ANGLE “occlusion is a normal relation of occlusal inclined planes of the teeth when jaw is closed . GPT: static relation between incising and masticating surfaces of maxillary & mandibular teeth or tooth analogues.

4. “Occlusion is the act or process of closure or of being closed or shut off” Ramfjord and Ash : Occlusion = Contacts between teeth “ Multifactorial functional relationship between the teeth and other components of the masticatory system as well as with other areas of the head and neck that directly or indirectly relate to function, parafunction or dysfunction of the masticatory system’’

5. Masticatory system Teeth Periodontium Articulatory system TMJ Muscles Occlusion

6. A therapeutic occlusion is one in which the arrangement of teeth and their opposing surfaces satisfy functional and esthetic requirements while distributing and directing forces of occlusion over as many teeth as possible during functions of the mandible. Physiologic occlusion- Occlusion that deviates in one or more ways from ideal, yet it is well adapted to that particular environment, is esthetic and shows no pathologic manifestation

7. Ideal Occlusion Guichet (1970) described standards for ideal occlusion and said that there was no one ideal occlusion pattern for all individuals but an appropriate pattern can be found based on these criteria . Criteria I- Incorporate into the occlusion those factors which have to do with the reduction of vertical forces. Criteria II- Provide a maximum intercuspation of teeth with the condyles in centric relation position. Criteria III- Provide for horizontal movement of the mandible from the centric position

8. Concepts of the Occlusion Historically, the study of occlusion and articulation has undergone an evolution of concepts.

9. Bilaterally Balanced Occlusion It is based on the work of Von Spee and Monson. Teeth should contact in all excursive positions of the mandible. On the nonworking side it’s important to prevent tipping of the complete denture. Subsequently, the concept was applied to natural teeth in complete occlusal rehabilitation.

10. Definition : The simultaneous contacting of the maxillary and the mandibular teeth on the right and left side and in the posterior and anterior occlusal areas in centric and eccentric positions, developed to lessen or limit the tipping or rotating of the denture base in relation to the supporting structures.

11. An attempt was made to reduce the load on individual teeth by sharing the stress among as many teeth as possible. It was soon discovered, however, that this was a very difficult type of arrangement to achieve. As a result of the multiple tooth contacts that occurred as the mandible moved through its various excursions, there was excessive frictional wear on the teeth

12. The Demise Of Balanced Occlusion In Restoring Natural Dentition Bilateral balanced occlusion Fixed Prosthodontics High rate of failure Failure was due to Increased occlusal wear. Increased/accelerated periodontal breakdown. TMJ and neuromuscular disturbances.

13. Unilateral Balanced / Group Function Occlusion In a unilaterally balanced occlusion , excursive contact occurs between all opposing posterior teeth on the laterotrusive (working) side only. This concept had its origin in the work of Schuyler

14. Definition:- Multiple contact relations between maxillary and mandibular teeth, in lateral movements on the working side, whereby simultaneous contact of several teeth acts as a group to distribute occlusal forces.

15. The most desirable group function occlusion consists of contact of canine,premolar and mesiobuccal cusp of first molar. Any laterotrusive contact more posterior than mesial portion of first molar are not desirable because of the increased amount of force that can be placed as its near the fulcrum and force vectors .

16. Advantages Group function of the teeth on the working side distributes the occlusal load . The absence of contact on the nonworking side prevents those from getting subjected to destructive ,obliquely directed forces found in nonworking interferences.

17. It also saves centric holding cusps that is mandibular buccal cusps and maxillary palatal cusps from excessive wear. Group function was felt to be goal for occlusal adjustments and has easy application. In the presence of anterior bone loss or missing canines, mouth should be restored to group function.

18. Disadvantages:- Group Function Occlusion doesn’t fulfill criteria for ideal occlusion

19. Characteristics of Group Function Given by BEYRON (1954) Teeth should receive stress along the tooth long axis . Total stress should be distributed among the tooth segment in lateral movement. No interferences occur from closure into intercuspal position

20. Mutually Protected Occlusion During the early 1960s, this occlusal scheme was advocated by Stuart and Stallard , based on earlier work by D’Amico. In this arrangement, centric relation coincides with the maximum intercuspation position.

21. Definition:- An occlusal scheme in which the posterior teeth prevent excessive contact of the anterior teeth in maximum intercuspation , and the anterior teeth disengage the posterior teeth in all mandibular excursive movements.

22. Posterior teeth function most effectively in stopping the mandible during closure whereas anterior teeth function most effectively in guiding the mandible during eccentric movements. It is apparent that the posterior teeth should contact slightly more heavily than anterior teeth in centric relation.

23. Lucia in 1961- Advantages Minimum amount of tooth contact is involved –therefore better penetration of food. A cusp to fossa relationship produces an interlocking of upper and lower components- giving a maximum support in centric relation in all directions. The force is clearly closer to the long axis of each tooth. The arrangement of the marginal,transverse and oblique ridges have a shearing action -make a more efficient

24. OCCLUSION BASICS FROM DENTAL ANATOMY

25. Based on arrangement of teeth Type of occlusal contact: Cusp- fossa occlusion Cusp-embrasure occlusion Ideal cusp- fossa relationship A, Mesiolingual cusp of maxillary first molar occludes in the central fossa of the mandibular first molar. Distal buccal cusp of mandibular first molar occludes in the central fossa of the maxillary first molar. B, Concept of occlusion in which all supporting cusps occlude in fossae

26. Normal intercuspation of maxillary and mandibular teeth . 1, Central incisors (labial aspect). 2, Central incisors ( mesial aspect). 3, Maxillary canine in contact with mandibular canine and first premolar (facial aspect). 4, Maxillary first premolar and mandibular first premolar (buccal aspect). 5, Maxillary first premolar and mandibular first premolar ( mesial aspect). 6, First molars (buccal aspect). 7, First molars ( mesial aspect). 8, First molars (distal aspect)

27. Types Of Cusps Centric holding cusps The buccal cusps of the mandibular posterior teeth and the lingual cusps of the maxillary posterior teeth occlude with the opposing CF areas . Non supporting cusp The buccal cusps of the maxillary posterior teeth and the lingual cusps of the mandibular posterior teeth are called the guiding or noncentric cusps.

28. OCCLUSAL SURFACE SHOWING CONTACT POINTS

29. IMPORTANCE OF OCCLUSION

30. PEDODONTICS The development of occlusion is the most dynamic phenomenon in the mouth. Development of normal dentition and occlusion depends upon dentoalveolar , skeletal and the neuromuscular factors. The emergence (eruption) of the primary dentition into the oral cavity is an important time for the development of oral motor behavior and the acquisition of masticatory skills.

31. STAGES OF OCCLUSAL DEVLOPMENT NEONATAL PERIOD PRIMARY DENTITION MIXED DENTITION PERMANENT DENTITION

32. FLUSH TERMINAL PLANE DISTAL STEP MESIAL STEP

33. FACTORS AFFECTING OCCLUSAL DEVELOPMENT General factors Skeletal factors Muscle factor Dental factor Local factors Aberrant developmental position Supernumerary teeth Hypodontia Habits Localized soft tissue anomalies

34. RESTORATIVE DENTISTRY Occlusal restorations should be such that it provides a definate centric stop for the opposing cusp at the central fossa If the centric stops are on the incline , the teeth are apt to move and new interferences will be created Common mistake is to overcarve the restoration –leading to interferences in lateral excursions Occlusal restorations should have the same hardness and potential for wear as the teeth Faulty interproximal contacts – disturb the occlusal relationship

35. PERIODONTICS Abnormal occlusion is a contributary factor in accelaration of periodontal breakdown OCCLUSAL TRAUMA – Defined as injury to the periodontium resulting from occlusal forces that exceeds the reparative capacity of the attachment apparatus.

36. Occlusion becomes a factor for consideration when the occlusal forces acting on a tooth produce displacement of the root in the socket which results in an injury to the supporting periodontal ligament. This periodontal tissue injury from occlusal forces has been defined as the lesion of trauma from occlusion The essential requirements for the co-destructive factor effect are the production of a traumatic lesion immediately subjacent to an established marginal periodontitis

37. ORAL SURGERY The treatment of maxillofacial fractures usually requires control of dental occlusion with the application of wires/arch bars for interdental wiring to orient and stabilize the fracture Important principle which is followed ‘ RESTORATION OF PREINJURY OCCLUSION ’

38. ORTHODONTICS Andrews , in 1972, observed the presence of six common characteristics, known as “six keys to normal occlusion” : Molar relationship Mesiodistal crown angulation Labiolingual crown inclination Absence of rotation Tight contacts Curve of spee

39. In 1976, Roth presented the following functional aspects of the occlusion as being fundamental for completion of the orthodontic cases: 1. Teeth must present maximum intercuspal (MI) position with the jaw in centric relation (CR); 2. In centric relation, all posterior teeth must present axial occlusal contacts, and the anterior teeth must maintain a distance of 0.0005 inches between them; 3. During laterotrusion , the canines must disocclude the posterior teeth (canine guidance); 4. During protrusion, the upper anterior teeth must occlude with the lower anterior teeth and the first premolar or the second premolar (in extraction cases), aiming at disoccluding all posterior teeth (immediate anterior guidance); 5. No interference must be present on the balancing side

40. WHY?? canine guidance at orthodontic completion the strategic positioning of the canine in the arch the favorable root anatomy presence of a better crownroot proportion the presence of dense and compact bone around the root, which better tolerates the occlusal forces compared with the medullar bone of the posterior teeth the sensorial pulse that activates less muscles when the canine teeth are in contact than when posterior teeth contact each other Therefore, when the jaw is in a right or left laterotrusive movement, the upper and lower canines are the appropriate teeth to contact and to dissipate the horizontal forces, while promoting the disocclusion of the posterior teeth.

41. The occlusion school- According to Kingsley, proper occlusion is a key factor in determining the stability of newly moved teeth. THEORIES OF RETENTION - By REIDEL Theorum 4 – Proper occlusion is a potent factor in holding teeth in their corrected positions. Aim of orthodontic treatment is to achieve good functional occlusion i.e. Harmonious occlusal contacts during functional movements of the jaws.

42. CONCEPTS OF COMPLETE DENTURE OCCLUSION Static concept The static relations in occlusion include centric occlusion, protrusive occlusion, right and left lateral occlusion. All of these relations must be balanced with the simultaneous contacts of all the teeth on both sides of the arch at their very first contact. The cuspal inclines should be developed so that the teeth can glide from a more centric occlusion to eccentric positions without interference and without the introduction of rotating or tipping forces.

43. Dynamic concept The dynamic concept of occlusion is primarily concerned with opening and closing movements involved in mastication. Jaw movements and tooth contacts are made, as the teeth of one jaw glide over the teeth of the opposing jaw. Movements of the mandible which occur when the teeth are not in contact are termed as free movements.

44. RPD opp prosthesis (Tooth/tooth-tissue supported ) 45 Partial Complete Centric Eccentric Working Non-working/Balancing Simultaneous bilateral contacts of opposing posterior teeth Kennedy”s Class III Kennedy”s Class I Kennedy”s Class II Kennedy”s Class IV Bilateral balanced occlusion in centric and eccentric positions. Max Mand + + + + contact of opposing anterior teeth in the planned intercuspal position occlusion seen in a harmonious natural dentition

45. Hanau’s Laws of Articulation and Hanau’s Quint . In 1925, Rudolph L. Hanau presented a discussion paper entitled, “Articulation: Defined, analyzed, and formulated ’’ FACTORS AFFECTING OCCLUSAL BALANCE : Condylar inclination. Incisal guidance. Height of the cusps Plane of orientation. Prominence of compensating curve.

46. Condylar inclination. Hanau states: “the inclination of the condylar guidance or condylar inclination is a definite , anatomical conception.” It is the one factor which the edentulous patient presents and can in no way be modified by the operator. The condylar path is determined on the patient by a protrusive record and set on the instrument

47. The degree of condylar inclination registered results from: 1. The incline of the articular eminence of the TMJ. 2. Action of muscles in mandibular movement. 3. Limitations of movements effected by the attaching ligaments. Among all the factors condylar inclination is most important in securing balanced articulation and form one of the end-controlling factor.

48. Incisal guidance. Second end- controlling factor formed by the inclination of the incisal guide angle. Hanau stated “the inclination of the incisal guidance is given by the angle of the lingual surface of the incisors with the horizontal plane of reference”.

49. INCISAL GUIDE ANGLE [GPT9] 1: anatomically, the angle formed by the intersection of the plane of occlusion and a line within the sagittal plane determined by the incisal edges of the maxillary and mandibular central incisors when the teeth are in maximum intercuspation 2: on an articulator, that angle formed, in the sagittal plane, between the plane of reference and the slope of the anterior guide table, as viewed in the sagittal plane

50. With the establishment of two end-controlling factors, a balanced articulation is obtained when a harmonious relationship is established between these two angles and cusp angles.

51. HEIGHT OF THE CUSP Hanau states “ The change of the cusp height in comparison with the masticatory surface formation as a whole is an auxiliary magnitude”. “In the establishment of the balanced articulation , we are primarily interested in the length and the inclination of the effective cusp inclines.”

52. Cusp height exerts its influence by determining the range of tooth contact during eccentric movements. The higher the cusp, the longer the effective tooth incline, and therefore greater range of tooth contact during eccentric movements.

53. Plane of orientation. Hanau states that “ plane of orientation is purely a geometrical factor. It is a plane assumed to pass through three dental landmarks or points; namely, the central incisal contact point and summits of the mesiobuccal cusps of the molars”.

54. Compensating curve. It is determined by the inclination of the posterior teeth and their vertical relationships to the occlusal plane 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.

55. COMPENSATING CURVE 1. The anteroposterior curving (in the median plane) and the mediolateral curving (in the frontal plane) within the alignment of the occluding surfaces and incisal edges of artificial teeth that is used to develop balanced occlusion 2. The arc introduced in the construction of complete removable dental prostheses to compensate for the opening influences produced by the condylar and incisal guidance’s during lateral and protrusive mandibular excursive movements

56. A steep condylar path requires a steep compensating curve for occlusal balance. A lesser compensating curve for the same condylar guidance would result in a steeper incisal guidance, which would cause loss of balance.

57. Occlusion in Implant supported prosthesis Factors that give rise to occlusal overloading excessive crown-to-implant length ratio over-sized occlusal surfaces unfavourable direction of axial forces cantilever effects

58. Single-tooth implants Aim – to ensure that occlusal loads are directed as much as possible along the longitudinal axis of the implant to ensure that loads are small If there is a tooth contact of light or medium intensity in maximum intercuspation position, a clearance of 30µm should be left between the occlusal face of the implant and the opposing arch.

59. This clearance aims to compensate for the different biomechanics of the tooth and the implant and to avoid overloading of the implant, since under heavy loads the tooth may intrude into the alveolus, whereas the implant-borne prosthesis will not intrude into the bone. In protrusive and lateral movements the occlusal face of the implant should not be loaded, in order to minimise the transverse forces that can act on implants

60. IMPLANT supported Fixed partial dentures Occlusion goals will vary depending on location (anterior or posterior) and on whether it has a unilateral- or bilateral free end

61. IMPLANT PROTECTED OCCLUSION Given by Misch Methods to reduce implant overloading : narrowed occlusal table, reduced cuspal inclination, correction of load direction, reduced non-axial loading, reduced length of the cantilever lighter occlusal contacts on implant prostheses

62. FULL MOUTH REHABILITATION OBJECTIVE reconstruction and restoration of the worn out dentition maintenance of the health of the entire stomatognathic system. Full mouth rehabilitation should re-establish a state of functional as well as biological efficiency where teeth and their periodontal structures, the muscles of mastication, and the temporomandibular joint (TMJ) mechanisms all function together in synchronous harmony.

63. The first step before any restorative treatment is to decide on which occlusal scheme there are two approaches: Conformative approach Indicated when original occlusion is not to be changed and the same patient's MIP will be used. It is recommended when a small restoration or bridge will be constructed or when there is no need to restore the entire occlusion at once. Advised when unprepared teeth provide the MIP and vertical stop. It is the favoured approach, because it is simple, predictable and safe, as little or no adaptation of the patient's neuro -muscular system is needed. This is true even in the presence of a slight discrepancy between the MIP and CR .

64. 2.Reorganised approach Indicated when construction of a new occlusal scheme is needed. The patient's occlusion is altered to a new occlusal scheme using the CR as a starting point for the treatment position. Aim- simultaneous occlusal contacts on both sides of the jaws when the mandible is in the CR. The occlusion is also designed to achieve an MIP that coincides with the CR position. It is considered in the following situations: ■ when the MIP is not satisfactory; ■ when an increase in vertical dimension is required; ■ when full mouth rehabilitation is required to reconstruct a severely damaged dentition; ■ when a large fixed prosthesis is needed to replace multiple missing teeth.

65. Sequence of ‘ Occlusal Rehabilitation’ 1. Quadrant arch technique — one quadrant is treated at a time. Advantage - the vertical dimension can be maintained and lengthy appointments are avoided. 2. Simultaneous arch technique — maxillary and mandibular arches are reconstructed simultaneously. The occlusion can be better established, aesthetics achieved is better, and number of appointments is reduced. However, this is more complicated, requires a skilled operator and technician, and may be difficult for beginners. 3. Segmented simultaneous arch technique — has advantages of the both the above techniques and is able to provide the best alternative .

66. TYPES OF OCCLUSAL ERROR

67. IN CENTRIC RELATION -3 TYPES Any pair of opposing teeth can be too long and hold the other teeth out of contact CORRECTION- The fossa of the teeth are deepened by grinding so the teeth will ,in effect telescope into each other. The cusps are not shortened

68. 2. Maxillary and mandibular teeth nearly end to end CORRECTION- Grinding is done on the inclines so as to move the maxillary cusp inclines buccally and mandibular cusp inclines lingually In the process ,central fossa are made broader, the lingual cusp of the maxillary tooth is made narrow by grinding from lingual side and buccal cusp of mandibular tooth is made more narrow by grinding from buccal side The cusps are not shortened

69. 3. Maxillary teeth too far buccal in relation to mandibular teeth CORRECTION- Lingual cusp of the maxillary teeth is made more narrow by broadening the central fossa In effect, the maxillary lingual cusp is moved lingually and mandibular buccal cusp is moved buccally Cusp are not shortened

70. TYPES OF WORKING SIDE OCCLUSAL ERRORS – 6 TYPES Both the maxillary buccal cusp and lower lingual cusp are too long The buccal cusp make contact but lingual cusp do not. The lingual cusp make contact but buccal cusp do not. Maxillary buccal or lingual cusp are mesial to their intercuspating position Maxillary buccal or lingual cusp are distal to their intercuspating position Teeth on the working side may not contact

71. TYPES OF BALANCING SIDE ERRORS – 2TYPES Balancing side contact is so heavy that working side teeth are held out of contact There is no contact on the balancing side

72. Pathogenic Occlusion A pathogenic occlusion is defined as an occlusal relationship capable of producing pathologic changes in the stomatognathic system. In such occlusions, sufficient disharmony exists between the teeth and the TMJs to result in symptoms that necessitate intervention .

73. Hypersensitivity to light Headache Ear ache Tinnitus Sensitivity to noise TMJ Problems Neck pain Difficulties in swallowing Bruxism

74. CONCLUSION The perfection of skill required to provide sophisticated yet an ideal treatment of complex occlusal problems may take years to acquire. However, the minimum expectation of the competent practitioner is the ability to diagnose and treat simple occlusal disharmonies. 85

75. REFERENCE Occlusion – Ramjford and Ash Textbook of dental anatomy – Wheelers Orthodontics The Art and Science – Bhalajhi Fundamentals of fixed prosthodontics – Shillingburg Contemporary Fixed Prosthodontics – Rosensteil Prosthodontic Treatment of Edentulous patients – Zarb Bolender Guidelines for occlusion strategy in implant-borne prostheses. A review International Dental Journal (2008) 58, 139-145 Present Status of Occlusion and Occlusal Therapy in Periodontics Fundamentals of occlusion and restorative dentistry. Part II: occlusal contacts, interferences and occlusal considerations in implant patients Rehabilitation strategies for partially edentulous - prosthodontic principles and current trends Implant protected occlusion: A comprehensive review Occlusal Concepts in Full Mouth Rehabilitation: An Overview

76. Thank you