Development of occlusion
- 1. DEPT OF PEDODONTICS AND PREVENTIVE DENTISTRY KRISHNADEVARAYA COLLEGE OF DENTAL SCIENCES AND HOSPITAL
- 3. Development of occlusion is a genetically and environmentally conditioned process which shows a great deal of individual variations consequently for the development of an acceptable occlusion, quite a remarkable co-ordination of different events.
- 4. Whyyy??????
- 5. It is an attempt to concentrate mainly on clinical features of developing dentition and establishment of their relationship in a perfect and healthy occlusion in permanent dentition by guiding the development of the oral cavity.
- 6. Occlusion is defined as the ‘Relationship between all the components of the masticatory system in normal function, dysfunction and parafunction’. An ideal occlusion is the perfect interdigitation at the upper and lower teeth, which is a result of developmental process consisting of the main three events:- Jaw growth ,Tooth formation, Eruption. The interrelationship between the teeth essentially becomes established in childhood, it continues to change to some extent through out the life.
- 8. Refers to the period from birth to the eruption of the first deciduous teeth in the oral cavity.At the birth time the alveolar arches are called GUM PADS. The maxillary arch is horse-shoe shaped and the mandible is U-shaped. They are firm and pink in color.The gum pads develop in two parts :- 1)Labial portion(differentiates first) 2)Lingual portion(differentiates later)
- 10. Sometimes an infant is born with teeth which are precociously erupted.
- 11. In the first of life, human growth is more rapid than that of any time, the dentition is developing at a rapid rate. At birth, the dental arches are small with a subsequent crowding of tooth germs which are within the jaw bone. This is overcome by increased jaw growth and the buccal placement of tooth germs. During this period there is increased anterior positioning of the lower jaw with relation to the upper jaw.
- 13. 1) GENERAL CHARECTERESTICS • Both the dental arches are half round in shape or ovoid. • Almost no curve of spee is present. • Shallow cuspal interdigitation. • Slight overjet and overbite • Vertical inclination of the incisors. • Little or no crowding.
- 14. There are two types of spacing :- SPACING Spaced dentition Primate spaces Physiologic spaces Non spaced dentition
- 15. SPACED DENTITION:- Spaced dentition is supposed to be good as spaces in between the teeth can be utilized of for adjustment of permanent successors which are always larger in size compared to the deciduous teeth. These spaces are of two types:- o PRIMATE SPACES: These spaces are very prominent spaces present mesial to the maxillary deciduous canines and the distal surface of the mandibular deciduous canines. These are also called ANTHROPOID SPACES.
- 17. 2) PHYSIOLOGIC/DEVELOPMENTAL SPACES: o These spaces are present in between the primary teeth and play an important role in normal development of the permanent dentition. o The total space present may vary from O- 8mm with an average of 4mm in the maxillary and an average of 3mm in the mandibular arch.
- 19. Primary teeth are present without any spaces in between the teeth. This lack of space may be due to the narrowness of the dental arches or teeth are wider than usual. This type of dentition usually indicates to crowding in developing permanent dentition, it is not always the case .It may develop on the individual’s growth of the jaws.
- 20. The primary dentition is said to be complete after the eruption of second primary molar. The dental arch(i.e roughly half circular in shape) connects the most distal surfaces of the right and left secondary primary molar should be preserved for the permanent dentition. The primary dentition occlusal relationship is explained under PRIMARY MOLAR RELATIONSHIP in the form of TERMINAL PLANES
- 22. The distal surface of the upper and lower teeth are in straight plane(flush) and therefore situated on the same vertical plane. This is the most favourable relationship to guide the permanent molars.
- 23. The distal surface of the lower molar is more mesial to that of the upper tooth.Invariably it is favourable to guide the permanent molars into a class I relationship.
- 24. The distal surface of the lower molar is more distal t of the upper. This relationship is prognostically unfavorable as it guides the permanent molars into distal occlusion.
- 25. OVER BITE: It is the distance which the incisal edge of the maxillary incisors overlap vertically past the incisal edge of the mandibular incisors. The average overbite in the primary dentition is 2mm. OVER JET: It is the horizontal distance between the lingual aspect of the maxillary incisors and the labial aspect of the mandibular incisor when the teeth are in centric relation.The average in primary dentition is 1-2 mm.
- 26. The relationship of the maxillary and mandibular deciduous canine is one of the most stable in the primary dentition. CLASS I When the mandibular canine interdigitates between the embrasure of max.lateral incisor and canine. CLASS II When mandibular canine interdigitates distal to the embrasure.
- 28. ARCH DIMENSIONS: The size of primary dental arch can be measured by dental arch width between the primary canine and the second primary molars. ARCH WIDTH: The width does not show substantial increase across the arch,both the arches increase in width by growing posteriorly to accommodate the eruption of the permanent molars.
- 29. ARCH LENGTH: T he arch length can be measured from the labial surface of the primary central incisors to the canines and to the premolars . ARCH CIRCUMFERENCE: The circumference is measured by the length of the curved line passing over the buccal cusps or the incisal edges of the teeth,from the distal surface of the primary second molar around the arch to the distal surface of the other primary molar. ARCH HEIGHT: There is little or no increase in the arch height during the period of the primary dentition.
- 31. The period during which both the primary and permanent teeth are in the mouth together is known as mixed dentition. The permanent teeth erupting in place of previous deciduous teeth are the SUCCESSIONAL TEETH, where as those erupting posteriorly to the primary teeth are called ACCESSIONAL TEETH.
- 32. Firsttransitionalperiod *Emergence of the 1st permanent molar. *Incisors transition. *Establishment of occlusion Intertransitionalperiod *Containing both sets of dentition. *Four permanent incisors,left and right first permanent molars. *Deciduous canines and deciduous first and second molars. Secondtransitional period *Emergence of bicuspids,cuspids and second permanent molars. *Establishment of occlusion
- 33. Calcification of the permanent dentition begins between birth and three years of age. Second premolars may not begin calcification until five years of age. Eruptive movement does not begin before crown calcification is complete. Enamel calcification is usually is usually complete three to four years before eruption into the oral cavity. Tooth crowns pierce the bony alveolar crest when approximately,2/3rd of root development is complete
- 34. Teeth emerge into the when approximately 3/4th of the root development is complete. Root development is complete approximately 2-3 yrs after eruption
- 35. EMERGENCE OF THE FIRST PERMANENT MOLARS: By the time of the first permanent molars eruption any initial spaces between the deciduous molars and canines will generally have dimnished or dissappeared. In both the jaws the first permanent molars erupt more or less in a perpendicular orientation to the occlusal plane. They originate one above the other in the ramus and come downward with the maxillary permanent molars being accomadated by additions at the tuberosity.
- 37. EARLY MESIAL SHIFT LATE MESIAL SHIFT PRIMARY MESIAL SHIFT GUIDANCE FOR PERMANENT DENTITION
- 38. If the deciduous dentition is spaced dentition with flush terminal relationship of second deciduous molar,the eruptive force of the permanent molars causes a closing of any existing spaces between the primary molars or primate spaces affectively causing a decrease in arch length.
- 39. When no spaces exist,the erupting first permanent molar is not able to close spaces.In these spaces when the primary molar exfoliates the permanent molar migrates mesially to use up the Lee way space(the difference between the mesiodistal width of primary canine,first and second molars and their permanent successors). This averages 1.8 mm in the maxilla and 3.4 mm in the mandible
- 40. The primary second molar relationship can give clues to the eventual permanent molar relationship.If the deciduous arches terminate in a mesial step. At the time the primary second molars are lost, both the maxillary and mandibular molars tend to shift mesially into the leeway space, but the mandibular molar normally moves mesially more than its maxillary counterpart. This differential movement contributes to the normal transition from a flush terminal plane relationship in the mixed dentition to a Class I relationship in the permanent dentition.
- 42. The period of transition(6 ½ - 81/2) is critical for the development of dentition.During the transition there are a no. of factors that determine the successful alignment of the permanent teeth toward an ideal arch form.
- 43. Interdental spacing averages 4mm in the maxillary arch and 3mm in the mandibular arch. The amount of anterior spacing in the primary dentition is one of the first clinical observation in examining a young child.
- 44. Only negligible amounts of growth occur from three years(completion of primary dentition) to 6-7 years when the permanent mandibular incisors begin to erupt. SEX DENTAL ARCH WIDTH INCREASE BETWEEN 2- 18YEARS MALES MAXILLA MANDIBLE 6mm 4mm FEMALES MAXILLA MANDIBLE 4.5mm 4mm
- 45. When the permanent incisors erupt, they assume a somewhat more anteriorly inclined position(labial inclination) than the deciduous incisors averages 2.3mm and results in an increase in intercanine arch length of approximately 3mm without any change in intercanine width. The interincisal angle between the maxillary and mandibular incisors is about 150 degree in primary dentition, whereas it is about 123 degree in permanent dental arch which makes the circumference wider.
- 47. The permanent incisors are usually the most larger in total width than the primary incisors,they replace (the difference is incisal liability) The permanent canine,premolars are usually smaller in total width than primary canine and molar they replace(the diference is Lee way space) The sum of the mesiodistal width of the permanent lateral incisors is generally smaller than of the primary lateral incisors by about 1mm in the maxilla and 3mm in the mandible,this carries out a smooth exchange of the lateral incisors
- 48. In contrast to the anterior teeth, the permanent premolars are smaller than the primary teeth they replace . The mandibular primary second molar is on the average 2 mm larger than the second premolar, while in the maxillary arch, the primary second molar is 1.5 mm larger. The primary first molar is only slightly larger than the first premolar, but does contribute and extra 0.5 mm in the mandible. The result is that each side in the mandibular arch contains about 2.5 mm of what is called leeway space, while in the maxillary arch, about 1.5 mm is available on the average.
- 50. School children tend to look unusual during the exchange of the incisors especially in the upper arch, when the permanent incisors erupt, these appear to be much larger compared with the primary teeth with their longitudinal axis flared out like as an inverse “V”. Due to the pressure of erupting permanent canines in the developing roots of lateral incisors, the crowns of erupting incisors flare more laterally producing diastema.
- 52. The transitional mal-alignment during the exchange period of the upper anterior teeth is called as “UGLY DUCKLING STAGE”. This phenomenon is self correcting and normally, the incisors gradually straighten with the eruption of the lateral incisors and canines.
- 54. The inter transitional period lasts for about 1.5 years. Under the influence of the tongue, the mandibular lateral incisors attain the proper sites within the dental arch and their initially lingual location is eliminated. Small rotations are corrected by the pressure exerted by the tongue and lips if the spatial conditions in the dental arches permits these movement.
- 55. At around 9-10 years of the age, the second transitional period starts with shedding of the posterior teeth. Transition from the ugly duckling stage to a mature stage of dentition is called PREPUBERAL PERIOD. This is correlative with the maturation of the child as a whole. The most common sequence of eruption of permanent lateral teeth in the maxilla is 4-3-5 and in the mandible is 3-4-5.
- 56. Permanent canine is larger than the primary canine, crowding get alleviated after the exofoliation of the secondary primary molar. If this sequence of eruption is changed to 4-3-5 or 4-5- 3,the Lee way space will not be utilized as efficiently as in such cases. The arch circumference may also become shortened than that of the primary dental arch by the utilisation of the leeway space with the exchange of the secondary primary molar to the second premolar.
- 57. The permanent dentition is considered when all the permanent teeth(all 28 teeth) are seen in the dental arches. After the occlusion of the dentition has been established fairly minor changes related to teeth take place in sagittal, transverse and vertical interrelationship. SALIENT FEATURES OF PERMANENT DENTITION Horizontal overbite decreases. Dental arches become shorter due to proximal wear and often crowding develops in the ‘mandibular incisor reigon by 14 years of age’
- 58. Vertical overbite decreases upto the age of 18 years by 0.5mm. The alveolar process may grow in height beyond 16years of age. Overjet decreases by 0.7mm between 12 and 20 years of age.
- 59. After the teeth travelled in a safe path….we end up with a beautiful smile on our face
- 60. THANK YOU
- 61. TEXT BOOK OF PEDODONTICS-SHOBHA TANDON Ist EDITION TEXT BOOK OF PEDODONTICS-NIKHIL MARWAH 4th EDITION A GENERAL REVIEW OF LITERATURE ON CHILD’S OCCLUSION- Li Ping Zhang B.D.S. Beijing