OCCLUSION- Occlusion is a complex phenomenon involving the teeth, periodontal ligament, the jaws, the temperomandibular joint, muscle and the nervous system

Angle defined occlusion as the normal relation of the occlusal inclined planes of the teeth when the jaws are closed.

Occlusion is a complex phenomenon involving the teeth, periodontal ligament, the jaws, the temperomandibular joint, muscle and the nervous system.

1. OCCLUSION

2. Angle defined occlusion as the normal relation of the occlusal inclined planes of the teeth when the jaws are closed. Occlusion is a complex phenomenon involving the teeth, periodontal ligament, the jaws, the temperomandibular joint, muscle and the nervous system. Introduction

3. The term occlusion has both static and dynamic aspects. Static refers to form alignment and articulation of teeth with in and between arches and the ralationship of teeth to their supporting structure. Dynamic refers to the function of stomatognathic system as a whole comprising teeth, supporting structure, temporomandibular joint, neuromuscular and nutritive systems.

4. 1] Centric holding cusps 2] Non supporting cusps 1] Centric holding cusps The facial cusps of mandibular and palatal cusps of maxillary posterior teeth occlude into central fossae and marginal ridge of opposing teeth. Also called stamp cusps. Types of cusps

5. 2] Non supporting cusps The maxillary buccal and mandibular lingual cusps are called non supporting cusps. They contact and guide the mandible during lateral excursions and shear food during mastication. Hence they are also called shearing or guiding cusps.

6. Human dentition exhibits two types of tooth arrangement when the upper and lower teeth occlude with one another. They are a. Cusp – fossae occlusion b. Cusp – embrasure occlusion Arrangement of teeth

7. Cusp – fossa occlusion Stamp cusp of one tooth occludes in a single fossa of a single opponent. The upper stamp cusp fit into all except the mesial fossae of the lower teeth while the lower stamp cusp fit into all upper fossae except the distal one of bicuspids. Cusp – embrasure contacts Also known as tooth to two teeth occlusion. Here each tooth occludes with two opposing teeth.

8. Balanced occlusion An occlusion in which balanced and equal contacts are maintained through out the entire arch during all excursions of mandible. Physiologic occlusion This refers to an 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 of dysfunction. Terminology

9. Traumatic occlusion It is an abnormal occlusal stress which is capable of producing or has produced an injury to the periodontium . Trauma from occlusion It is defined as periodontal tissue injury caused by occlusal forces through abnormal occlusal contacts.

10. Curve of Spee (Ferdinand Graf von Spee ) It refers to the antero posterior curvature of the occlusal surfaces beginning at the tip of the cuspid and following the cusp tips of the bicuspids and molars continuing as an arc through the condyle . If the curve is extended, it would form a circle of about 4 inch diameter. A flat or mild curve of Spee was essential to an ideal occlusion.[ Imaginary occlusal planes and curves

11. Curve of Spee

12. Curve of Wilson The curve that contacts the buccal and lingual cusp tips of the mandibular buccal teeth. It is medio lateral on each side of arch. It results from the inward inclination of lower posterior teeth. The upward (U-shaped) curvature of the maxillary and mandibular occlusal planes in the coronal plane.

13. Curve of Wilson

14. It helps in two ways 1] Teeth are alighned parallel to the direction of medial pterygoid for optimum resistance to masticatory forces. 2] The elevated buccal cusps prevent food from going past occlusal table.

15. Curve of Monson It is obtained by extending the curve of Spee and curve of Wilson. Curve of Monson is defined as  a proposed ideal curve of occlusion in which each cusp and incisal edge touches or conforms to a segment of the surface of a sphere 8″ in diameter with its center in the region of the glabella .

16. The six keys keys to normal occlusion are 1] Molar inter arch relationship The mesio buccal cusp of upper first molar should occlude in the groove between the mesial and medial buccal cusp of lower first molar. The mesiolingual cusp of upper first molar should occlude in the central fossa of lower first molar ANDREW’S SIX KEYS TO NORMAL OCCLUSION

17. 2] Mesio distal crown angulation A line that passes along the long axis of the crown through the most prominent part in the centre of labial or buccal surface is called long axis of the clinical crown. For the occlusion to be considered normal, the gingival part of the long axis of the crown must be distal to the occlusal part of the line.

18. 3] Labio lingual crown inclination If the gingival area of crown is more lingually placed than the occlusal area, it is referred to as positive crown inclination. Gingival area of crown is more labially or buccally placed than the occlusal area it is referred to as negative crown inclination.

19. Maxillary incisors exhibit a positive crown inclination while mandibular incisors show a mild negative inclination. Maxillary and mandibular posteriors have a negative crown inclination.

20. 4] Absence of rotation Normal occlusion is characterised by absence of any rotation. Rotated posterior teeth occupy more space in the dental arch while rotated incisors occupy less space in the arch.

21. 5] Tight contacts To consider an occlusion as normal, there should be tight contact between adjacent teeth. 6] Curve of Spee A normal occlusal plane according to Andrews should be flat, with the curve of Spee not exceeding 1.5 mm.

22. Occlusal development can be divided into the following developmental periods. 1] Pre - dental period 2] The deciduous dentition period 3] The mixed dentition period 4] The permanent dentition period Development of occlusion

23. 1] Pre dental period The alveolar process at the time of birth are known as gumpads . They are horse shoe shaped and develop in two parts – labio buccal portion and lingual portion. The two portions are divided by dental groove. The gumpads are divided into ten segments by certain grooves called transverse grooves.

24. The lateral groove between canine and deciduous first molar is called lateral sulcus . The upper gum pad is both wider as well as longer than the mandibular gum pad. When the upper and lower gum pads are approximated, there is a complete overjet all around.

25. Gum pads

26. Contact occurs in first molar region and space excists between them in the anterior region. This infantile open bite is considered normal and it helps in suckling.

27. The initiation of primary tooth bud occurs during first six weeks of intra uterine life. The primary teeth begin to erupt at the age of about 6 months. Eruption is completed when the second deciduous molars come into occlusion by 21/2 to 3 ½ years of age. 2] Deciduous dentition period

28. Spacing in deciduoud dentition – Spacing usually excist in deciduous teeth. These spaces are called physiological or developmental spaces. Absence of spaces in primary dentition is an indication that crowding may occur when larger permanent teeth erupts.

29. Physiologic spaces

30. Spacing seen mesial to the maxillary canine and distal to mandibular canine. These physiologic spaces are called primate spaces or simian spaces or anthropoid space as they are commonly seen in primates. These spaces help in the placement of the canine cusps of the opposing arch.

31. PRIMATE SPACE

32. Flush terminal plane – In deciduous dentition the distal surfaces of the upper and lower second deciduous molars are in the same vertical plane.

33. Deep bite – It occurs during initial stages of development. The lower incisal edges often contact the cingulum area of the maxillary incisors. Deep bite later reduced due to 1] Eruption of deciduous molars 2] Attrition of incisors 3] Forward movement of mandible due to growth

34. Begins at approximately 6 years of age with eruption of first permanent molar. During this period, deciduous teeth along with some permanent teeth are present in oral cavity. 3] Mixed Dentition period

35. Mixed dentition is divided into three stages 1] First transitional period 2] Inter transitional period 3] Second transitional period

36. First transitional period It is characterised by the emergence of permanent molars and the exchange of the deciduous incisors with the permanent incisors. The first permanent molars are guided into the dental arch by the distal surface of second deciduous molars.

37. Flush terminal plane The distal surface of upper and lower second deciduous molar are in one vertical plane. Erupting permanent molars will also be in flush or end on relation. For the transition of end on molar relation to class I molar relation, the lower molar has to move forward by 3-5 mm relative to upper molar. This occurs by utilization of physiologic spaces and leeway space in lower arch and by differential forward growth of the mandible.

38. The mesio distal relation between the distal surfaces of the upper and lower second deciduous molars can be of three types. a] Flush terminal plane b] Mesial step terminal plane c] Distal step terminal plane

39. The shift can occur either in early or late shift. Early shift occurs during early mixed dentition period. The eruptive force of the first molar is sufficient to push the the deciduous first and second molars forward in the arch to close primate space and establish class I molar relation. Since this occurs early in the mixed dentition period, it is called early shift.

40. Some children lack primate space and thus erupting permanent molars drift mesially utilizing the leeway space. This occurs in the late mixed dentition period and is called late shift.

41. Distal surface of the lower second deciduous molar is more mesial than that of the upper. Thus permanent molars erupt directly into Angles Class I occlusion. This commonly occurs due to early forward growth of the mandible. If the forward growth is minimal, it will result in a class I molar relation. If forward growth persists, it will result in class III molar relation. B. Mesial step terminal plane

42. It is characterised by the distal surface of the lower second deciduous molar being more distal to that of upper. C. Distal step terminal plane

43. Exchange of incisors During the first transitional period the deciduous incisors are replaced by permanent incisors. The permenent incisors are larger than the deciduous teeth they replace. The difference between the amount of space needed for the accomodation of the incisors and the amount of space available for this is called incisal liability . The incisal liability is about 7 mm in maxillary and 5mm in mandibular arch.

44. Incisal liability is overcome by the following factors A] Utilization of interdental spaces seen in primary : Physiologic spaces are utilized to partly account for the incisal liability. B] Increase in inter canine width : The increase in inter canine width helps to accommodate larger permanent canines of both maxillary and mandibular arches. C] Primary incisors are more upright than the permanent incisors. It increases the dental arch perimeter and it helps in accomodating the larger permanent incisors.

45. During this period there is both deciduous and permanent teeth. Both permanent incisors and first permanent molars and deciduous molars and canines. Inter transitional period

46. It is characterised by the replacement of the deciduous molars and canine by the premolars and permanent cuspids respectively. The combined mesio distal width of permanent canine and premolar is usually less than that of the deciduous canines and molars. This surplus space is called Leeway space of Nance. The second transitional period

47. It is more in mandible than maxilla. The amount of Leeway space is 1.8 mm in maxillary arch and 3.4 mm in the mandibular arch. The excess space available after the exchange of the deciduous molars and canine is utilized for mesial drift of mandibular molars to establish class I molar relation.

48. Ugly Duckling stage Transient of self correcting malocclusion seen in the maxillary incisor region between 8-9 years of age. It is seen during the eruption of permanent canines. As the permanent canines erupt, they displace the roots of lateral incisors mesially . The force is transmitted to roots of central incisors which gets displced mesially .

49. The resultant divergence of crowns of two central incisors cause midline spacing. This situation described by Broadbent as ugly duckling stage as children tends to look ugly during this phase of development. This condition is self corrected when the permanent canine erupts into oral cavity

50. Ugly Duckling Stage

51. Permanent denition forms with in jaws soon after birth except for cusps of first permanent molars which form before birth. Permenent incisors develop lingual to deciduous incisors and move labially as they erupt. Premolars develop below the diverging roots of deciduous molars. 4] Permanent dentition period

52. When two teeth in the same arch are in contact, their curvatures adjacent to contact areas form spillways called embrassures . They are continuous with the interproximal spaces between teeth. EMBRASSURE/ SPILLWAY

53. Above contact areas incisally and occlusally , the spaces bound by marginal ridges are called incisal or occlusal embrassures . These embrassures and the labial or buccal and lingual embrassures are continuous.

54. It has following functions 1] Provides spillway for food during mastication 2] Prevent food from being forced through contact areas 3] Enhances the self cleansing property of teeth.

55. Embrassure is constant in sectional areas of dental arches. These sections are named maxillary anterior, mandibular anterior, maxillary posteriorand mandibular posterior section.

56. Embrassures are reflection of form of teeth involved. A line bisecting canine create an anterior half mesially resembling the half of an anterior teeth and posterior half that resembles a posterior teeth.

57. Deglutition (Swallowing) Figure 22.13a-c

58. Two types of swallowing 1] Infantile swallowing 2] Adult swallowing

59. infantile (or immature) swallow has the following characteristics: 1. The jaws are apart, with the tongue between the gum pads; 2 . The mandible is stabilized mainly by contraction of the facial muscles and the interposed tongue. 3. Disappears with age. 4 . The swallow is guided and to a great extent controlled by sensory interchange between the lips and the tongue

60. Features of Adult Swallow 1] Tip of the tongue ‐palatal rugae Mid portion‐hard palate Posterior aspect‐45degree against posterior pharyngeal wall 2] Facial muscles‐passive 3] Mandibular elevators ‐ contracted

61. THANK YOU