Development_of_Occlusion.pptx by Sahil khan...

Dental anatomy

1. Occlusion Development of occlusion By Md Ashiqur Rahman 1 st year pgt HIDSAR

2. Introduction The term occlusion is derived from the Latin word, ‘ occlusio’,defined as the relationship between all the component of the masticatory system in normal function,dysfunction and parafunction . Angle defined occlusion as the normal relation of the occlusal inclined planes of the teeth when the jaws are closed.

3. The static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues.( gpt )

4. Ideal occlusion :Preconceived theoretical concept of occlusal structural and functional relationship that includes idealized principles and characteristics that an occlusion should be Physiologic occlusion: one that deviates in one or more way from ideal yet it is well adapted to that particular environment and is esthetic and shows no pathological manifestation. Young Jl physiologic occlusion J Am Dent 1926

5. Functional occlusion: An arrangement of teeth which will provide highest efficiency during excursive movements of mandible which is necessary during function. Balanced occlusion: An occlusion in which balance and equal contacts are maintained throughout entire arch during all excursion of mandible.

6. Centric occlusion :Maximum intercuspation of dentition irrespective of condylar position Centric Relation: the position of condyle in glenoid fossa when they are in their most anterosuperior position against the slope of ementia with the articular disks properly interposed.Okeson describes it as most musculoskeletal stable position of condyle. Crawford S D Condylar axis position as determined by the occlusion and measured by cpi instrument sign and symptom of tmd

7. Brief history of occlusion In 1899, Edward Angle was the first to describe occlusal relationship. The first significant concept to developed to describe optimum functional occlusion was called “balanced occlusion”. It was developed for complete denture primarily. Okeson JP. Management of Temporomandibular Disorders and Occlusion. 6th ed. St. Louis: Mosby; 2003.

8. Unilateral balanced occlusion also known as group function. Widely accepted method in restorative dentistry. Concept originated by the works of Schuyler 1953. All teeth on working side to be in contact during lateral excursion.no teeth contact on non working side.

9. The absence of contact on the non working side prevent those teeth from being subjected destructive oblique force found in non working interference . It also saves the centric holding cusp from excessive wear.

10. In early 1960 mutual protected occlusion was advocated by Sears and Stallard . In this posterior teeth comes in contact at the end of chewing stroke, minimizing horizontal loading on teeth. Concurrently posterior tooth acts as vertical stop when the mandible returns to maximum intercuspation . It cant be used in crossbite .

11. In 1970 , dynamic individualized occlusion emerged. It centers around the health and function of the masticatory system and not on any specific occlusal configuration. Okeson JP. Management of Temporomandibular Disorders and Occlusion. 6th ed. St. Louis: Mosby; 2003.

12. Stages of occlusal development Predental stages or mouth of neonate (0-6months) Deciduous dentition stage(6months -6years) Mixed dentition stages(6years-12years) -First transitional stage -inter transitional stage - Second transitional stage permanent dentition stage

13. Pre-dentate stage Pre dentate stage refers to the period from birth t ill the eruption of first deciduous tooth in the oral cavity. Ideally ranges from birth to 6 months but a delay in eruption of first deciduous teeth by 4-10 months is considered normal.

14. Gum Pad The alveolar process at the time of birth are known as gum pads. These are pink, firm and are covered by fibrous periosteum .

15. Gingival groove - Dental groove- Transverse grooves- Lateral sulcus -

16. The lateral sulcii are useful in judging the inter arch relationship at a very early stage. The lateral sulcus of mandibular arch is normally more distal to that of maxillary arch.

17. Friel.S Development of Ideal Occlusion of the gum Pad and teeth 1954

18. Relation of gum pads At rest A nterior open bite Contact occurs between upper and lower arch in the first molar region Tongue is interposed between the space. The upper gum pad is larger anteroposteriorly and transversely than the mandibular gum pad so there is overlap at the front and the sides .

19. Primary Dentition stages(6months -6years)- - Development of primary dentition and occlusion the primary teeth begins to erupt at the age of about 6 months. The eruption of all primary teeth is completed by 2 half – 3 half years of age when the second deciduous molars come into occlusion. The mandibular central incisor are the first teeth to erupt in oral cavity. The sequence of eruption of deciduous dentition is A-B-D-C-E.

20. Spacing in deciduous dentition Space usually exist between deciduous teeth. physiological spaces or developmental spaces.

21. Nelson SJ,Ash MJ “wheeler Dental Anatomy,physiology and occlusion”9:279;2010

22. Spacing is invariably seen mesial to maxillary canine and distal to mandibular canines. These physiological spaces or simian space or anthropoid space as they are commonly seen in primates

23. Features Deep bite-when the primary incisors erupt the over bite is deep. T his could be due to the vertical inclination of the primary incisors.over the period of time,this deep bite reduces due to two reasons- 1.eruption of primary molars 2.Rapid attirit i on of incisors. 3. Forward movement of mandible due to growth At about six years of age ,there may be an edge to edge relationship. Overjet - overjet is initially more in primary dentition.The overjet decrease with the movement of the whole dental arch anteriorly . The av e rage overjet in primary dentition is 1 to 2mm.

24. Terminal plane relations (Baume’s classification)1950  Baume LJ. Physiologic tooth migration and its significance for the development of occlusion. J Dent Res. 1950;29:123–32

25. Mixed dentition stage-the tr an sitional years (6-12 years of age) Transition form the primary dentition to the permanent dentition begins at 6years of age with the eruption of the permanent first molars and permanent incisors.Early during this period of time ,many children experience the eruption of four permanent first molars and the exfoliation of the mandibular central incisors. It is the period during which both primary and permanent teeth are present in the mouth.

26. This stage of occlusal development can be divided into the three stages - 1) First t rasitional period 2) inter - trasitional period 3) second trasitional period.

27. First trasitional period- This period makes the first exchange of teeth which begins by 6 years of age and is usually completed within two years. important steps - The eruption of first permanent molars T he replacement of incisors.

28. The location and relationship of the first permanent molar depends much upon the distal surface relationship between the upper and lower second deciduous molars. The first permanent molar guided into position by distal surfaces of the second deciduous molar

29. The mesio distal relation between the distal surfaces of the upper and lower 2 nd deciduous molar can be of 3 types . Flush terminal plane. The shift in molar from a flush terminal plane to a class I relation can occur in 2 ways. Early sift occurs during the early mixed dentition period. The eruptive force of the first permanent molar is sufficient to push the deciduous first and second molar forward in the arch to close the primate space and there by establish class1 molar relationship. since this occurs early in the mixed dentition period it is called early shift.

30. Mesial step: In this type of relationship the distal surface of lower second deciduous molar is more mesial than the upper . Then the Ist permanent molar erupts directly into Angle class I occlusion. This type of mesial step terminal plane most commonly occurs due to early forward growth of the mandible. If the differential growth of the mandible in a forward direction persists, it can lead to an angle Class III molar relation . If the forward growth of mandible is minimal it can establish a class I molar relation

31. Distal step terminal plane : This is characterized by the distal surface of the lower 2 nd deciduous being more distal to that of the upper. Thus the erupting 1st permanent molar may be in Angle class II occlusion.

32. Influence terminal plane on 1 st Molar Proffit RW “contemporary Orthodontics”

33. Flush terminal plane Mesial step Distal step Class1 56% Class II 44% Class I > ClassIII Class II Nelson SJ,Ash MJ “wheeler Dental Anatomy,physiology and occlusion”9:279;2010

34. Replacement of the incisors /incisor liability- Sir W arren mayne ( 1969 ) The deciduous incisors are replaced by the permanent incisors.The permanent incisors are considerably larger than the deciduous ones . The difference in amount of space needed for the accommodation of the incisors and the amount and the amount of space available is available is called incisal liability The incisal liability is about 7mm for maxillary arch and 5mm for mandibular arch.

35. Incisor liability is overcome by following factor: Utilization of interdental space seen in primary dentition Increase in inter canine width : During the transition from primary to permanent incisors an increase in inter canine width has been observed

36. Change in incisor inclination : one of the difference between primary and permanent incisors is their inclination. The primary incisors are more upright than the permanent incisors . Since the permanent incisors erupt more labially inclined they tend to increase the dental arch perimeter

37. Ugly duckiling stage Broadbent phenomenon 1937 Self correcting annomaly

38. Inter transitional stage In this period the maxillary and mandibular arches consist of sets of deciduous and permanent teeth. Between the permanent incisor and 1 st molar are the deciduous molar and canine. This period is relatively stable. The anteroposterior relation between the 2 jaws is not fixed in occlusion . A fixed intercusp relationship is absent in absence of interference the mandibular teeth attains more mesial position.

39. Second transitional period- R eplacement of the primary canines and molars. 10-12 years of age.

40. Leeway space of Nance The combined mesiodistal width of the deciduous canine,I and II primary molars is greater than the combined mesiodistal width of the permanent canine ,I premolars and II premolars. This is called leeway space of nance . In the maxillary arch - 0.9mm on one side,totaling to 1.8mm. I n the mandibular arch - 1.7mm on one side,totaling to 3.4mm.

41. Change in molar relationship from mixed dentition to permanent dentition- There are two important contributors to the molars transition- 1. late mesial shift of the molar- After the shedding of primary II molar,the first permanent molar shift mesially.This mesial shift of the lower molar is more when compared to upper molars because of the more amount of leeway space. 2. Differential growth of mandible relative to maxilla is the second contributor.Because of the cephalocaudal growth,mandible grows more than maxilla.

42. Permanent dentition All the 28 permanent teeth are seen in dental arch. 12-14 yrs of age. The eruption sequence maxillary arch 6-1-2-4-3-5-7 Mandibular arch 6-1-2-3-4-5-7

43. The last major change that occurs in the occlusion of the permanent teeth is the result of wear-wear of the cusps and interproximal wear. The wear of the cusps shortens the height of the teeth so that in occlusion the mandible swings further up, and consequently forward, and the incisors meet edge to edge.

44. The interproximal wear appears to reduce the mesiodistal diameters of the maxillary and mandibular teeth, so that the length of the arches decreases. Individual variation are considerable.

45. Andrew`s Key to Normal Occlusion Andrew 1972 Key 1 Molar relationship The distal surface of the distobuccal cusp of the upper first permanent molar made contact and occluded with the mesial surface of the mesiobuccal cusp of the lower second molar. The mesiodistal cusp of the upper first permanent molar fell within the groove between the mesial and middle cusps of the lower first permanent molar. (The canines and premolars enjoyed a cusp-embrasure relationship buccally , and a cusp fossa relationship lingually .)

46. Key II Crown Angulation “ Mesiodistal tip” The gingival part of the long axis of the crown must be distal to the occlusal part of the line The long axis of the crown for all teeth,except molars, is judged to be the middevelopmental ridge, which is the most prominent and centermost vertical portion of the labial or buccal surface of the crown. The long axis of the molar crown is identified by the dominant vertical groove on the buccal surface of the crown .

47. Key III Crown Inclination ( labio -lingual) The maxillary incisors exhibit a positive crown inclination while the mandibular incisors show a very mild negative crown inclination. The maxillary and mandibular posteriors have a negative crown inclination

48. Key IV Absence of Roatation

49. Key V Tight contact

50. Key VI Occlusal plane Acc to Andrew it should be flat not exceeding 1.5mm

51. Conclusion In simplest way occlusion is the way the maxillary and mandibular teeth articulate but in reality dental occlusion is much more complex relationship because it involves morphology and angulation of teeth,the muscles of mastication, the skeletal structure, the TMJ and the functional jaw movement. Understanding it would help us to provide restoration which is harmonious with the oral health.

52. Reference Young Jl physiologic occlusion J Am Dent 1926 Crawford S D Condylar axis position as determined by the occlusion and measured by cpi instrument sign and symptom of tmd Nelson SJ,Ash MJ “wheeler Dental Anatomy,physiology and occlusion”9:279;2010 Proffit RW “contemporary Orthodontics”  Baume LJ. Physiologic tooth migration and its significance for the development of occlusion. J Dent Res. 1950;29:123–32 Friel.S Development of Ideal Occlusion of the gum Pad and teeth 1954 Okeson JP. Management of Temporomandibular Disorders and Occlusion. 6th ed. St. Louis: Mosby; 2003. Dawson TMJ smile and design Balaji 5th edition