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Development of occlusion

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The active supervision of the developing dentition is a responsibility of the pedodontist. Seeing things from the beginning is most advantageous. By making a detailed study of dentition from initiation through eruption till functional occlusion, we may be able to obtain a clear concept of how occlusion develops and how its development can be guided. Knowledge of the normal development of the dentition and an ability to detect deviation from the normal are essential pre-requisites for pedodontic diagnosis and a treatment plan.

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Development of occlusion

  1. 1. DEVELOPMENT OF OCCLUSION. PRESENTED BY –DR KOMAL BAGDE 1ST YEAR PG PEDODONTICS.
  2. 2. CONTENTS INTRODUCTION CLASSIFICATION PERIODS OF OCCLUSAL DEVELOPMENT NEONATAL PERIOD PRIMARY DENTITION PERIOD MIXED DENTITION PERIOD PERMANENT DENTITION PERIOD CONCLUSION.
  3. 3. Introduction Occlusion of the teeth is the key to normal oral function. From birth until adulthood and beyond, dental occlusion undergoes significant changes. It is important for the clinician to understand and recognize the scope of the changes that are normally occurring in the dentition to be able to diagnose any abnormal developments.
  4. 4. And yet, what may be abnormal for one age may be normal for another., eg: time linked nature of normalcy such transient malocclusions, as crowding during eruption of incisors, the ugly duckling stage, end-on molar relationship tendencies before loss of the deciduous second molars and lingual inclination of erupting mandibular second molars before the tongue has had a chance to influence the erupting teeth.
  5. 5. OCCLUSION The literal meaning of occlusion is closing -‘ (Oc- Up; Clusion – Closing) According to Angle - • Occlusion is the normal relation of the occlusal inclined planes of the teeth when jaws are closed. According to Bishara - • Occlusion is the way in which the maxillary and mandibular teeth articulate. According to American Association of Orthodontists - • Occlusion is the relationship of the maxillary and mandibular teeth as they are brought into functional contact. Graber TM. Orthodontics: principles and practice. 3rd ed. Philadelphia: WB Saunders; 1972 Bishara SE. Textbook of Orthodontics. Philadelphia: WB Saunders; 2001 AAO Glossary 2012, American Association of Orthodontists,2012
  6. 6. “The changing interrelationship of the opposing surfaces of the maxillary & mandibular teeth which occur during movements of the mandible & terminal full contact of the maxilla & mandibular arches.” Salzmann & Gregory : ‘‘Relationship between all components of masticatory system in normal function, dysfunction & parafunction.’’ Foster: Occlusion- the static relationship between the incising or masticating surfaces of the maxillary or mandibular teeth or tooth analogues. The Glossary of prosthodontics 8
  7. 7. • The term occlusion refers to the relationship of the teeth of the maxilla and mandible when the jaws are closed and the condyles are at rest in the glenoid fossae. -Sheldon Friel • Normal occlusion is defined as the structural composite fundamentally consisting of jaw, teeth and characterized by the normal relationship of the so called occlusal inclined planes that are individually and collectively in architectural harmony with their basal bone and cranial anatomy, exhibit correct proximal contacting and axial positioning and have associated with them normal growth, development, location and correlation of all environmental tissues and parts. -Strang and Thompson, 1940
  8. 8. CLASSIFICATION Pediatric Occlusal therapy: a scientific approach to comprehensive interceptive orthodontist for the general practitioner Quintessence International 1978;9:39-46 According to BARNETT :
  9. 9. CLASSIFICATION According to van der Linden : 1. Complete deciduous dentition 2. Mixed Dentition Period: • The First Transition Period • Intertransitional Period • The Second Transitional Period 3. The Permanent Dentition Period Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983
  10. 10. PRE-NATAL DEVELOPMENT Post natal dental arch is described as catenary curve. The pre-natal dental arch • changes shape at 6 to 8 weeks , • anteroposteriorly it is flattened, • no catenary curve. By the Bell stage of the tooth germs , anterior segment of arch elongates Approaches the catenary curve by 4th month .
  11. 11. Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 Four different arrangements of deciduous teeth in both jaws before birth.
  12. 12. • At birth ,maxilla and mandible are small in size in comparison to other structures of face. • Lower jaw is present dorsally to the upper jaw. • Region of both jaws that contain tooth bud grows during first 6 to 8 months of post-natal life. • Anterior crowding disappears after birth, instead space is present and diastemata is present between all teeth. • Transverse development of both jaws is mainly due to: 1. Median palatal suture of maxilla 2. Symphysis of mandible Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983
  13. 13. NEO-NATAL PERIOD Pre-dental period /Gum pad stage- after birth. Teeth absent.
  14. 14. • Gum pads are pink, firm and covered by a dense layer of fibrous periosteum. • Horse shoe shape • Dental groove separates labio- buccal portion and the lingual portion. • Transverse groove divides gum pad in 10 segments- consisting 1 developing
  15. 15. • The groove between the canine and the 1st molar region is called the lateral sulcus, useful for judging the inter arch relationship at a very early stage. • Gingival groove, separates gum pad from the palate and floor of mouth in corresponding upper n lower jaws.
  16. 16. Relationship of gum pads. • At rest gum pads are separated by tongue and protrudes over the lower gum pads to lie immediately behind the lower lip. • Class II pattern with maxillary gum pad being more prominent and retropositioned lower gum pad. • Complete overjet. • Anterior open bite is seen at rest with contact only at
  17. 17. • The lateral sulcus of mandibular arch is normally distal to that of maxillary arch. • Mandibular functional movements are mainly vertical, and to a little extent antero-posterior. Lateral movements are absent. • The gum pads grow rapidly during the 1st year of life & the growth is more in the transverse direction. • Length increases, mostly in Relationship of gum pads.
  18. 18. Precociously Erupted Primary Teeth Natal Teeth present at birth Neo-natal Teeth erupt within 30 days of birth SHAFERS
  19. 19. Natal and Neo-natal teeth • Incidence – 1:1000 • 85% of natal teeth are mandibular incisors,11% maxillary incisors. • Etiology: - superficial positioning of tooth germ - increased rate of eruption due to febrile incidents - hormonal stimulation - heredity • Syndrome associated: Rigafede syndrome Hallermann-Streiff syndrome Chondroectodermal dysplasiaSHAFERS
  20. 20. • COMPLICATIONS :  Interfere with feeding  Risk of aspiration  Traumatic injury to the baby’s tongue and/or to the maternal breast. • DIAGNOSIS:  A radiographic verification of the relationship between a natal and/or neonatal tooth and adjacent structures, nearby teeth, and the presence or absence of a germ in the primary tooth area would determine whether or not the tooth belongs to the normal dentition  Most natal and neonatal teeth are primary teeth of the normal dentition and are not supernumerary teeth  Correspond to teeth of the normal primary dentition in 95% of cases, while 5% are supernumerary SHAFERS
  21. 21. TREATMENT  If the erupted tooth is diagnosed as a tooth of the normal dentition -- maintenance of these teeth in the mouth is the first treatment option, unless this would cause injury to the baby.  Their removal should be indicated only when they interfere with feeding or when they are highly mobile, with the risk of aspiration. SHAFERS
  22. 22. SELF-CORRECTING ANOMALY Retrognathic mandible. • Differential and forward growth of mandible. Anterior open bite. • Eruption of primary incisors. Infantile swallowing pattern. • Introduction of solid food in diet.
  23. 23. The eruption of primary teeth begins at about 6 months after birth and all the primary teeth are usually erupted by 2 ½ years of age i.e. when the second molars come to occlusion. At this stage the roots of the second molars are usually not yet complete. Therefore the establishment of the primary dentition is usually considered to take place at about 3 years of age when the root completion takes place and lasts until 6 years of age when first permanent tooth begins to erupt Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983
  24. 24. DEVELOPMENT OF DENTAL ARCHES AND DECIDUOUS TEETH Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 • At birth. • Mandibular central incisor - 6 to 8 months. • Maxillary central incisor- 7 to 9 months. • U & L lateral incisors – 1 yr.
  25. 25. Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 E. 1st molar – 16 months. F. Canine – 20 months. G. 2nd molar – b/w 24 to 30 months. H. Complete deciduous dentition with successors within the jaws.
  26. 26. SEQUENCE OF ERRUPTION A B D C E A B D C E
  27. 27. Primary Dentition Period From around the 6th month to 6 years Both dental arches are half round or ovoid shape. In the anterior and posterior region, teeth are oriented perpendicular to occlusal plane .
  28. 28. Characteristic features a. Half round in shape. Diastema is present in adjacent teeth. b. Mandibular teeth occlude lingually to the maxillary ones. Diastemata- mesial to 1st deciduous molar, between latter, & 2nd deciduous molar. c. The vertical overjet varies between 0-2mm.In the anterior region,The deciduous teeth are oriented perpendicular to occlusal plane in MD and LL directions. d. Same applies to deciduous molars. The mandibular teeth occlude slightly mesially to the corresponding maxillary teeth.
  29. 29. Spacing Baume in 1950 divided primary dentition in two parts. A. Spaced dentition B. Non spaced dentition LOUIS J. BAUME , Physiological tooth migration & its significance for the development of occlusion.J Dent Res.1950;29:123,331-4,440
  30. 30. It is supposed to be good as spaces in between the teeth can be utilized for adjustment of permanent successors, which are always larger in size compared to the deciduous teeth. The spaces present are of two types:-  Primate spaces  Physiological spaces
  31. 31. Primate spaces Simian spaces’- Baume 1940 Primate spacing –Bokya 1968 ‘Anthropoid spaces’- Foster and Hamilton 1969 • Maxillary arch-exists between deciduous lateral incisor and deciduous canine. =1.7 mm • Mandibular arch- exists between deciduous canine and 1st deciduous molar=1.5mm
  32. 32. Importance of Primate spaces Spaced primary arches generally produce more favorable alignment of the permanent incisors whereas 40% of the arches with out anterior spacing produce crowded anterior segment. The presence of mandibular primate space is conductive of proper molar occlusion by means of an early shift of mandibular molars (primary) into this primate space on eruption.
  33. 33. The mean increase in intercanine widths brought about by lateral and frontal alveolar growth is lesser in spaced arches than non-spaced arches, so that there is no excessive space for the erupting permanent incisors. The width of the permanent incisors is greater than their deciduous counterparts, primate spaces help to accommodate these wider teeth.
  34. 34. Physiologic spaces First described by Dellabarre 1819 ‘physiologic spaces’-Khorkhous and Norman Developmental spaces’-Faber 1962 Spaces present between all the primary teeth. • Maxillary arch-The total space present may vary from 0-8mm, average – 4mm. • Mandibular arch- the total space present may vary from 1-7 mm, average 3mm.
  35. 35. Non-Spaced dentition • Lack of space between primary teeth either due narrowness of the arches or wider than usual teeth. • This type of dentition may indicate crowding in developing permanent dentition, but its not always the case. • It may depend on individuals growth of the jaw.
  36. 36. Development of molar relationship Cone funnel mechanism: The first vertical support associated with inter- digitation the interlocking of the maxillary and mandibular posterior teeth-the 1st deciduous molars attain contact. It seldom happens that antagonists erupt in such a way that no displacement is needed to arrive at good intercuspation.
  37. 37. Cone-funnel mechanism In most instances, the large palatal cusp of the maxillary first deciduous molar arrives with its cone shaped within the fossa of the mandibular first molar. The fossa will function as a funnel by which both the teeth are directed towards each other in proper position. The adjustment of the eruption direction occurs more in the maxilla than in the mandible; the morphology of the mandible is less suited for the purpose.
  38. 38. Cone-funnel mechanism Vander linden (a) No translation needed. (b) Lower molar functions as funnel. (c) Less translation of lower molar than of upper. (d) Resulting occlusion.
  39. 39. Molar relationship The mesio-distal relation between the distal surfaces of maxillary and mandibular 2nd deciduous molars is called the terminal plane. This is of three types:  Flush terminal plane  Mesial step terminal plane  Distal step terminal plane
  40. 40. Flush Step The distal surface of deciduous 2nd maxillary and mandibular molars are in a straight plane (flush) and therefore situated in same vertical plane. Most favorable relationship to guide the permanent molars in class I Seen in 74%
  41. 41. Mesial step Distal surface of mandibular deciduous 2nd molar is mesial to the distal surface of maxillary deciduous 2nd molar. Favorable to guide permanent molars in class I relationship. It can proceed to end- on/half cusp relationship or class III relationship with continued mandibular growth.
  42. 42. Distal Step Distal surface of mandibular 2nd deciduous molar is more distal to the distal surface of the maxillary 2nd deciduous molar It is prognostically unfavourable as it guides the permanent molars in class II relationship. Seen in 10%.
  43. 43.  Acc. to a study by Bishara et al , the distribution of terminal plane relationships was found to be: Distal step - 10% Flush terminal plane- 29% Mesial step of 1-0 mm -42% Mesial step > 1-0 mm -19% Samir E Bishara – ‘Changes in molar relation between deciduous and permanent dentition –a longitudinal study . Am J Orthod 1988;93:19-28
  44. 44. The molar relationship on emergence depends upon: 1. A-P relationship between two molars in the jaw before eruption. 2. Relationship between maxilla & mandible in sagittal plane. 3. M-D crown dimension ratio of maxillary and mandibular deciduous molars.
  45. 45. Canine relationship Yilmaz Y, Primary Canine and Molar Relationships in Centric Occlusion in Three to Six Year-Old Turkish Children: A Cross-Sectional Study The Journal of Contemporary Dental Practice, Volume 7, No. 3, July 1, 2006 Class I: The cusps tip of the maxillary primary canine tooth is in the same vertical plane as the distal surface of the mandibular primary canine. Class II : The cusp tips of maxillary primary canine tooth is mesial to the distal surface of mandibular primary canine. Class III: The cusp tip of the maxillary primary canine tooth is distal to the distal surface of the mandibular primary canine.
  46. 46. Anterior relationship Overbite: the vertical overlap of incisiors. Average- 2mm Overjet : the horizontal overlap of incisors. Average-0-4mm Decreases with age.
  47. 47. Arch Dimension s• These were first measured by Zsigmondy in 1890. • Primary arches are ovoid. • Generalized interdental spacing-decreases with age. • Both maxillary and mandibular arches increases in width by growing posteriorly to accommodate the
  48. 48. Arch width: width between primary canines and primary 2nd molars. Increment of 0.5 mm in less than 20% of cases. Arch circumference: determined by measuring the length of curved line passing over the incisal edges and buccal cusps of teeth from distal surface of primary second molar around the arch to the distal surface of primary 2nd molar on other side.
  49. 49. Self correcting anomalies of Deciduous dentition Anterior deep bite Correction:  Forward and downward growth of mandible.  Attrition of incisal edges.  Eruption of permanent molars.
  50. 50. Primate spaces  Early mesial shift. Flush terminal plane  Early mesial shift.  Late mesial shift. Physiologic spaces  Permanent incisor accommodation.
  51. 51. REFERENCES Graber TM. Orthodontics: principles and practice. 3rd ed. Philadelphia: WB Saunders; 1972 Bishara SE. Textbook of Orthodontics. Philadelphia: WB Saunders; 2001 AAO Glossary 2012, American Association of Orthodontists,2012 occlusal therapy: a scientific approach to comprehensive interceptive orthodontist for the general practitioner Quintessence International 1978;9:39-46
  52. 52. REFERENCES Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 The Glossary of prosthodontics 8 vol 94 number 1 pge no 54 LOUIS J. BAUME , Physiological tooth migration & its significance for the development of occlusion.J Dent Res.1950;29:123,331-4,440. Yilmaz Y, Primary Canine and Molar Relationships in Centric Occlusion in Three to Six Year-Old Turkish Children: A Cross-Sectional Study The Journal of Contemporary Dental Practice, Volume 7, No. 3, July 1, 2006
  53. 53. DEVELOPMENT OF OCCLUSION. PRESENTED BY –DR KOMAL BAGDE 1ST YEAR PG PEDODONTICS.
  54. 54. Development of occlusion Content: Apical area of van der Linden. Mixed dentition period. Permanent Dentition Conclusion References.
  55. 55. van der Linden’s concept of apical area The relationships between the developing dentition and the growth of the jaws and the problems that can originate therefrom are easier to understand if the jaws are not considered in totality, but are taken in subdivisions. Extraclarity is gained when the region in which teeth were formed initially and in which the roots are later located, is given prominence in such consideration. In 1979,van der linden introduced the concept of apical area : DEVELOPMENT OF THE HUMAN DENTITION:AN ATLAS Frans P. G. M. van der linden and Herman S. Duterloo New York, 1976,
  56. 56. The apical area of infants :the forming parts of the deciduous and permanent teeth In deciduous dentition: apices of the deciduous teeth& forming parts of the permanent teeth. In mixed dentition: the roots of the deciduous and permanent teeth and forming parts of the non- erupted permanent teeth. In adult state :apices of the fully formed teeth can be normally seen. DEVELOPMENT OF THE HUMAN DENTITION:AN ATLAS Frans P. G. M. van der linden and Herman S. Duterloo New York, 1976,
  57. 57. DEVELOPMENT OF THE HUMAN DENTITION:AN ATLAS Frans P. G. M. van der linden and Herman S. Duterloo New York, 1976, anterior • between the mesial surface of forming parts of permanent canines and those of apices after eruption is completed middle • Between anterior part and mesial surface of the forming part of the 1st permanent molar. posterior • Situated dorsally to the middle section and includes maxillary tuberosity and lingual tuberosity in mandible. Apical area is further divided into:
  58. 58. Changes in apical area. Size of apical area increases markedly in the 1st year of life. Tooth germs move within the growing jawbones- increase in apical area in transverse and ventral directions is restricted, decidedly, particularly in mandible. Only through apposition and resorption enlargement of mandible occurs. The anterior part of lower border of mandible undergoes no changes except for the increase in thickness of the bone. DEVELOPMENT OF THE HUMAN DENTITION:AN ATLAS Frans P. G. M. van der linden and Herman S. Duterloo New York, 1976,
  59. 59. In maxilla, the mid palatal suture continues to offer possibility for increase in width. In the region, posterior to the canine and 1st premolar maxilla can be still built outwards by apposition and resorption. Posterior section of maxilla and mandible ,it gradually increases in size and is built up dorsally from birth to the end of facial growth. Considerable variation in size is encountered in each 3 sections, classified as large, medium or small. The size of apical area has important consequence for • the positions of the teeth in the jaws when they have not yet emerged, • for the process of transition & • for the ultimate situation after development of the dentition. DEVELOPMENT OF THE HUMAN DENTITION:AN ATLAS Frans P. G. M. van der linden and Herman S. Duterloo New York, 1976,
  60. 60. Mixed dentition Period. Emergence of the First Permanent Molars & the Transition of the Incisors -The first transition period The Dentition in the Intertransition period The Transition of the Posterior Teeth,Canine and the Emergence of the Second Permanent Molars -The second transition period. Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983
  61. 61. Emergence of the First Permanent Molars & the Transition of the Incisors -The First Transition Period. Prior to the transition of incisors,6 years of age 1st permanent molar erupt. In both the jaws, 1st permanent molars erupt – perpendicular orientation to the occlusal plane(MD & BL) MD crown dimension of maxilla =MD crown dimension of mandible: mesial step MD crown dimension of maxilla < MD crown dimension of mandible :flush terminal plane Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983
  62. 62. Ideally, the eruption of permanent molar into a class I relationship is desired. Since the flush terminal relationship is more common in deciduous dentition, it is more common for permanent molars to erupt into an end-to-end relationship. The desired class I can be established by the following ways; A. early mesial shift B. late mesial shift Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983
  63. 63. Early mesial shift In children with spaced primary dentition, the mandibular 1st molars close the primate space distal to canine. Thereby, the flush terminal plain gets converted into a mesial step. This allows the permanent maxillary first molars to erupt into Class 1 molar relationship. This is called “early mesial shift”.
  64. 64. Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 Late mesial shift In non spaced dentition and lack of primate spaces, the erupting 1st molars are not able to establish class I relationship as they erupt. In these cases, the molars establish class I relation by drifting mesially and utilizing the leeway space after exfoliation of deciduous molars.
  65. 65. Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 Transition of the Incisors. During the first transitional period the deciduous incisors are replaced by the permanent incisors. The mandibular central incisors are usually the first to erupt. M-D width of permanent 4 incisors>M-D width of deciduous 4 incisors. The difference between the amount of space needed for the accommodation of the incisors and amount of space available for this is called Incisal Liability.
  66. 66. Anterior Relationship Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 a. The deciduous incisors are oriented approximately perpendicular to the occlusal plane. Permanent Incisors are located lingually to the roots of their predecessors and are labially inclined. Resorption of deci. roots is associated with the eruption of succesors. b. First the mandibular first permanent molar emerges,then the mandibular central incisor.The maxillary central permanent incisor emerges some weeks after the loss of its predecessor. c. The maxillary first permanent molar has emerged
  67. 67. Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 Anterior Relationship • The lower lip touches the incisal margins of the maxillary central incisor and covers 1 to 3 mm of its labial surface. • Continuing jaw growth and increase of the pressure exerted by the perioral musculature result in a more upright position
  68. 68. Transition of the mandibular incisors in a medium anterior section of the apical area
  69. 69. Transition of the maxillary incisors in a medium anterior section of the apical area
  70. 70. Transition of the maxillary incisors in a medium anterior section of the apical area (e) In accordance with the positions at initial formation, the apices of fully erupted lateral permanent incisors are located more palatally and also more occlusally than those of the central incisors.(f) The permanent incisors are distally angulated and there is a large central diastema. Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983
  71. 71. Transition of the mandibular incisors in a large anterior section of the apical area
  72. 72. Transition of the maxillary incisors in a large anterior section of the apical area
  73. 73. Transition of the mandibular incisors in a small section of the apical area
  74. 74. Transition of the maxillary incisors in a small section of the apical area
  75. 75. Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 Some of the factors that help in alignment of incisiors by gaining space are: 1. Utilization of interdental spacing of primary incisors: average 4mm in maxillary arch and 3mm in mandibular arch 2. Increase in intercanine arch width: this occurs due to growth of the jaws. Intercanine width increases markedly with eruption of lateral incisors. Males 6mm for maxilla females 4.5mm for maxilla 4mm for mandible 4mm in mandible
  76. 76. By the end of the 9th year in girls and 10th year in boys, the mandibular intercanine arch width dimensions is essentially completed. In the maxilla there is little anterior maxillary arch width increase in girls after 12 years of age. The difference in increase of maxillary dimension is due to the fact that the pubertal growth spurt in girl is from 10 to 12 years of age. While in boys it is from 12 to 18 years of age. Textbook of craniofacial growth,Sridhar Premkumar Intercanine width
  77. 77. Textbook of craniofacial growth,Sridhar Premkumar The final horizontal growth increments in the mandible, particularly in the males, causes a forward movement of the mandibular base with its teeth. The basal change eliminates any flush terminal plane tendencies that have persisted beyond the mixed dentition. But the bodily mandibular thrust forward is unmatched by comparable maxillary horizontal growth changes. Hence the maxillary intercanine dimension serves as a safely valve for this basal discrepancy. Intercanine width increase during : Maxilla – emergence of central incisor Mandible-emergence of lateral incisor
  78. 78. Textbook of craniofacial growth,Sridhar Premkumar 3. Intercanine arch length: The permanent incisiors assume some what anterior(labial) position than deciduous dentition. The incisor position averages 2.3mm in maxilla and 1.3 mm in mandible. 4. Interincisal angulation: The angle between maxillary and mandibular incisiors is 150 degrees in primary dentition, whereas its 123 degrees in permanent dentition, thus more proclination and gaining space for incisor alignment.
  79. 79. Intertransitional period This period lasts for 1.5 yrs Asymmetry in emergence and associated difference in levels of clinical crowns of corresponding left and right side is made-up. There is wearing of deciduous teeth with attrition of cusp tips. Small rotations are corrected by pressure exerted by the tongue and lips.
  80. 80. The second transitional period is characterized by the replacement of the deciduous molars and canines by the premolars and permanent canines respectively. At around 10 years of age the deciduous canines shed, but just before the shedding there is a transient or self correcting malocclusion seen in the maxillary incisor region between the age of 8 – 9 years. Second transition period
  81. 81. Nnace HN.the limitations of orthodontics treatment.I. Mixed dentition diagnsis and treatment . Am J Orthod 1947;33:177-223 Leeway space of NANCE Described by Nance in 1947 M-D width of: C+D+E> 3+4+5 Leeway space = (C+D+E )- (3+4+5) Maxilla: 0.9 mm/segment = 1.8 mm. Mandible: 1.7 mm/segment = 3.4mm.
  82. 82. Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 Ugly Duckling Stage (Broadbent’s phenomenon) Around the age of 8 - 9 years, a midline diastema is commonly seen in the upper arch, which is usually misinterpreted by the parents as a malocclusion. Its typical features are: o Flaring of the lateral incisors. o Maxillary midline diastema
  83. 83. ` Crowns of canines on young jaws impinge on developing lateral incisor roots, thus driving the roots medially and causing the crowns to flare laterally.
  84. 84. Ugly Duckling Stage ctd.. The roots of the central incisors are also forced together, thus causing a maxillary midline diastema. With the eruption of the canines, the impingement from the roots shift incisally thus driving the incisor crowns medially, resulting in closure of the diastema as well as the correction of the flared lateral incisors
  85. 85. Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 Second transition period The most common sequence of eruption of cuspids and bicusipds in maxilla is 4-3-5 , in mandible is 3-4-5. If the sequence of eruption is changed to 4-3-5 or 4-5-3 in mandible the leeway space will not be utilized as efficiently and in such cases the dentition will become crowded without the leeway space helping to improve. After the eruption of cuspids and bicuspids the dental arch is established . The second molars begins to erupt. The dental arch reduces just prior to eruption of 2nd molar by mesial forces. Therefore its possible that the crowding will accentuate if its already present.
  86. 86. The second Transitional period 8-9 years 9-10 years 10-11 years 10-12 years 11-12 years 12-13 years
  87. 87. Self correcting developmental anomalies: Mandibular anterior crowding  Spacing,  intercanine width increase,  tongue pressure
  88. 88. • Ugly duckling stage  Maxillary canine eruption. • End-on molar relation of permanent 1st molar  Late mesial shift 8 years 11 Year
  89. 89. Permanent dentition The permanent dentition forms within the jaws soon after the birth, except for cusps of the first permanent molars, which forms before birth. This period is marked by the eruption of the four permanent second molars Sequence of eruption
  90. 90. Chronology of tooth development.
  91. 91. British standard classification of INCISOR RELATIONSHIP (1983) CLASS I : The lower incisal edge occlude with or lie immediately below the cingulum plateau of upper incisor.
  92. 92. Class II: The lower incisor edge lie posterior to the cingulum plateau of the upper central incisor. Division 1: The overjet is increased and the upper central incisors are proclined. Division 2: The overjet is minimal or increased with retroclined upper central incisors.
  93. 93. Class III: The lower incisor edges lay anterior to the cingulum plateau of the upper central incisor. The overjet is reduced or reversed.
  94. 94. Canine relationship Class I: When the mesial slope of upper canine coincides with distal slope of lower canine.
  95. 95. Class II: When the mesial slope of upper canine is ahead of distal slope of lower canine.
  96. 96. Class III: When the mesial slopes of the upper canine lies behind the distal slope of the lower canine
  97. 97. The curvatures of teeth and arches Curve of Spee. Curve of Monson
  98. 98. CURVE OF SPEE Ferdinand Spee (1890) “The anatomic curve established by the occlusal alignment of teeth, as projected onto the median plane beginning with the cusp tip of canine and following the buccal cusp tips of Premolars & Molars teeth, continuing through the ant. border of ramus , ending in the condyle” GPT-7
  99. 99. Occlusal plane An excessive curve of spee restrict the amount of space available for the upper teeth results in crowding. A flate curve of spee is most receptive for normal occlusion .(the mandibular curve of spee should not be deeper than 1.5mm) A reverse curve of spee creates excessive space in upper jaw.
  100. 100. CURVE OF MONSON George Monson (1920) “ the curve of occlusion in which each cusp and incisal edge touches or conforms to a segment of a spear of 8 inches in diameter with its center in the region of the glabella.” - GPT-7
  101. 101. The six keys to n,ormal occlusion Lawrence F. Andrews, D.D.S. San Diego, Calif. Keys of occlusion Andrew in 1970 put forward keys to occlusion after studying 120 patients with ideal occlusion. He hypothesized that the presence of the following 6 features is necessary for an ideal occlusion. I. Molar interarch relationship II. Mesiodistal crown angulations III. Labiolingual crown inclination IV. Absence of rotation V. Tight contacts VI. Curve of spee
  102. 102. The six keys to n,ormal occlusion Lawrence F. Andrews, D.D.S. San Diego, Calif. MB cusp of the max 1st molar falls into the mesiobuccal groove of the mand 1st molar and that the distal surface of the DB cusp of the upper first permanent molar should make contact and occlude with mesial surface of the MB cusp of the lower second molar.ML cusp of upper 1st molar should occlude in central fossa of lower first molar Key I. Molar relationship
  103. 103. The six keys to n,ormal occlusion Lawrence F. Andrews, D.D.S. San Diego, Calif. Key II-Mesiodistal crown angulation The gingival part of the long axis of the crown must be distal to the occlusal part of the axis. ‘plus reading’-gingival portion of the long axis of crown is distal to the insical portion. ‘minus reading’- gingival portion of the long axis of crown is mesial to the insical portion Add image
  104. 104. The six keys to n,ormal occlusion Lawrence F. Andrews, D.D.S. San Diego, Calif. Key III. Labiolingual crown inclination If the gingival portion of the crown’s labial surface is lingual to the occlusal portion, its referred as positive crown inclination. Seen in maxillary incisors. If the gingival portion of the crown’s labial surface is labial to the occlusal portion, its referred as negative crown inclination. Seen in mandibular incisors and maxillary &mandibular posteriors.
  105. 105. The six keys to n,ormal occlusion Lawrence F. Andrews, D.D.S. San Diego, Calif. Key IV. Absence of Rotations Teeth should be free from undesired rotations. Rotated Posterior teeth occupy more space in dental arch while rotated anterior teeth occupy less space in the arch.
  106. 106. The six keys to n,ormal occlusion Lawrence F. Andrews, D.D.S. San Diego, Calif. Key V . Tight contacts contact points should be tight (no spaces). In absence of abnormalities such as genuine tooth size discrepancies, contact point should be tight.
  107. 107. The six keys to n,ormal occlusion Lawrence F. Andrews, D.D.S. San Diego, Calif. Key VI – Occlusal plane or curve of spee The curve of Spee should have no more than a slight arch. Intercuspation of teeth is best when the plane of occlusion is relatively flat. A deep curve of spee results in a more contained area for the upper teeth, making normal occlusion impossible.
  108. 108. Key VII . Correct tooth size or the bolton’s ratio Bennett and McLaughlin in 1993 gave seventh key to normal occlusion. i.e. the upper and lower tooth size should be correct.
  109. 109. conclusion The active supervision of the developing dentition is a responsibility of the pedodontist. Seeing things from the beginning is most advantageous. By making a detailed study of dentition from initiation through eruption till functional occlusion, we may be able to obtain a clear concept of how occlusion develops and how its development can be guided. Knowledge of the normal development of the dentition and an ability to detect deviation from the normal are essential pre-requisites for pedodontic diagnosis and a treatment plan.
  110. 110. References DEVELOPMENT OF THE HUMAN DENTITION:AN ATLAS.Frans P. G. M. van der linden and Herman S. Duterloo New York, 1976. Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 British standard classification of INCISOR RELATIONSHIP (1983) Wheeler’s dental anatomy physiology and occlusion.Ash nelson.Occlusion pgno-437. Graber TM. Orthodontics: principles and practice. 3rd ed. Philadelphia: WB Saunders; 1972 Bishara SE. Textbook of Orthodontics. Philadelphia: WB Saunders; 2001 The six keys to n,ormal occlusion .Lawrence F. Andrews, D.D.S. San Diego, Calif.
  111. 111. MD crown dimension of maxilla equal to MD crown dimension of mandible: mesial step
  112. 112. conclusion The active supervision of the developing dentition is a responsibility of the pedodontist. Seeing things from the beginning is most advantageous. By making a detailed study of dentition from initiation through eruption till functional occlusion, we may be able to obtain a clear concept of how occlusion develops and how its development can be guided. Knowledge of the normal development of the dentition and an ability to detect deviation from the normal are essential pre-requisites for pedodontic diagnosis and a treatment plan.
  113. 113. REFERENCES Graber TM. Orthodontics: principles and practice. 3rd ed. Philadelphia: WB Saunders; 1972 Bishara SE. Textbook of Orthodontics. Philadelphia: WB Saunders; 2001 AAO Glossary 2012, American Association of Orthodontists,2012 occlusal therapy: a scientific approach to comprehensive interceptive orthodontist for the general practitioner Quintessence International 1978;9:39-46 Development of the dentition Frans PGM van der Linden Quientessence Publishing Co., Inc 1983 The Glossary of prosthodontics 8 vol 94 number 1 pge no 54 LOUIS J. BAUME , Physiological tooth migration & its significance for the development of occlusion.J Dent Res.1950;29:123,331-4,440

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