Development of dentition and occlsion
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The document discusses the development of primary and permanent dentition in humans. It describes the characteristics of human dentition including dental formula. Tooth development occurs in three stages - bud, cap and bell stage. The primary teeth erupt in a sequence from 6-30 months. Characteristics of primary dentition include spacing, shallow overjet and overbite, and vertical inclination of anterior teeth. Molar relationships in primary dentition can be flush, mesial step or distal step.
Development of dentition and occlsion
- 1. DEVELOPMENT OF DENTITION and occlusion DONE BY: AMRITHA JAMES, CRI
- 2. introduction The purpose of knowing tooth development is to know the course of normal development, clinical features of dentition and the most common developmental disturbances.
- 3. Characteristics of human dentition Teeth of vertebrates are characterized depending on: Mode of attachment • Acrodont –teeth attached to jaws by connective tissue • Pleurodont- teeth are set inside the jaws • Thecodont – teeth are inserted in a bony socket. Number of successive teeth •Polyphyodont- multiple set of teeth. Eg:sharks •Diphyodont- two set of teeth. Eg: humans •Monophyodont- one set of teeth. Eg: sheep, goat Shape of teeth • Homodont – a single type of teeth • Heterodont – various types of teeth
- 4. Dental formula Permanent dentition: Primary dentition:
- 5. Development of tooth Tooth formation occurs in the 6th week of intrauterine life with the formation of primary epithelial band. At about 7th week the primary epithelial band divides into a lingual process called dental lamina & a buccal process called vestibular lamina. All deciduous teeth arises from dental lamina, later the permanent successors arise from its lingual extension & permanent molars from its distal extension
- 6. DENTAL LAMINA Around 6th week the infero-lateral border of the maxillary arch and the supero-lateral border of the mandibular arch show localized proliferation of the oral ectoderm resulting in the formation of the horse shoe shaped band of tissue called the dental lamina. The deciduous teeth are directly formed by the proliferation of the lamina. The permanent molars develop as a result of its distal proliferation. Succedenous teeth develop from a lingual extension of the lamina.
- 7. ENAMEL ORGAN The ectoderm in certain areas of the dental lamina proliferates and forms knob like structures that grow into the underlying mesenchyme. Each of these knobs represent a deciduous tooth and is called the enamel organ.
- 8. development of teeth is divided into 3 stages Bud stage. Cap stage. Bell stage.
- 9. BUD STAGE This is the initial stage of tooth development where the enamel organ resembles a small bud. The enamel organ consists of peripherally located low columnar cells and centrally located polygonal cells.
- 10. CAP STAGE The tooth bud continues to proliferate resulting in a cap shaped enamel organ. The outer cells of the cap covering the convexity are cuboidal – the outer enamel epithelium. The cells lining the concavity of the cap→ tall columnar – the inner enamel epithelium. The polygonal cells between the outer and the inner epithelium forms a cellular network – the stellate reticulum. The ectomesenchymal condensation ie:- dental papilla and dental sac are pronounced during this stage.
- 11. BELL STAGE Due to the continued uneven growth of the enamel organ it acquires a bell shape A few layers of flat squamous cells between the inner enamel epithelium and the stellate reticulum – stratum intermedium. As the enamel formation starts the stratum intermedium collapses to a narrow zone reducing the distance between the outer and the inner epithelium.
- 12. LATE BELL STAGE Inner enamel epithelium → ameloblasts ( tall columnar cells ) → enamel. Dental papilla → odontoblast (cuboidal cells then later columnar) → dentin. Outer enamel epithelium→ low cuboidal cells → capillary network. Dental sac → circular arrangement of fibers → periodontal ligament. The junction between inner enamel epithelium and odontoblast → dentinoenamel junction.
- 13. STAGES OF TOOTH BUD DEVELOPMENT: Initiation Phase of deciduous tooth- 5th month in utero. Phase of permanent tooth-6th month Phase of accessional tooth-4th month in utero to 4-5 yrs. Proliferation Histodifferentiation. Morphodifferentiation. Apposition.
- 14. NOLLA’S STAGES OF TOOTH DEVELOPMENT 1952: 0. Absence of crypt 1. Presence of crypt 2. Initial calcification 3. 1/3rd crown completion 4. 2/3rd crown completion 5. Crown almost completed 6. Crown completion 7. 1/3rd root completion 8. 2/3rd root completion 9. Root almost completed 10. Root completion
- 15. ERUPTION OF PRIMARY TEETH
- 16. ERUPTION OF PERMANENT TEETH
- 17. PRE EMERGENT ERUPTION Eruptive movements begin soon after the root begins to form. Two processes are necessary for pre emergent eruption:- 1. There must be resorption of bone and primary tooth roots overlying the crown of the erupting tooth. 2. The eruptive mechanism itself then must move the tooth in the direction where the path has been cleared.
- 18. POST EMERGENT ERUPTION Once the tooth erupts into the mouth it approaches the occlusal level and is subjected to the forces of mastication. The amount of tooth eruption after the teeth have come into occlusion equals the vertical growth of ramus in a patient who is growing normally
- 19. FACTORS AFFECTING DEVELOPMENT OF DENTITION Accelerating effect: • Hyperthyroididm • Hyperpituitarism • Turners syndrome Decelerating effect: • Hypothyroididm • Hypopituitarism • Downs syndrome • Hypovitaminosis • Amelogenesis imperfecta Systemic factors:
- 20. Local factors Aberrant tooth position Lack of space in the arch Early loss of predecessor Ectopic eruption Congenital absence of tooth Ankylosed tooth Retained deciduous Supernumerary tooth
- 21. PERIODS OF OCCLUSAL DEVELOPMENT 1. Pre-dental period. 2. The deciduous dentition period. 3. The mixed dentition period. a. First transitional period b. Inter transitional period c. Second transitional period 4. The permanent dentition period
- 22. PRE - DENTATE PERIOD (birth to 6 months)
- 23. GUM PADS The alveolar processes at the time of birth. Pink in colour, firm and are covered by a dense layer of fibrous periosteum. The upper gum pad is horse shoe shaped & the lower gum pad is U shaped and rectangular, characterized by:
- 24. Characteristics of gum pads: • Dental groove:-separates the labiobuccal and the lingual portion. • Transverse groove:-divides the gum pad into ten segments representing each deciduous tooth. • Gingival groove:-separates the gumpad from the palate and the floor of the mouth. • Lateral sulci:-present between the canine and the 1st molar.
- 25. When the upper and the lower gum pad are approximated there is a complete overjet all around. This infantile open bite is considered to be normal . It helps in sucking.
- 26. NATAL and NEONATAL TEETH Very rarely teeth are present at birth called as Natal Teeth. If they erupt during the 1st 30 days then they are called as Neonatal Teeth. 90% of precociously erupted teeth are primary, of which 85% are mandibular incisors.
- 27. Etiology: • Superficial position of tooth germ • Increased rate of eruption due to febrile incidents • Hormonal stimulation • Hereditary Complications : • Interfere with feeding • Risk of aspiration • Traumatic injury to the baby’s tongue and/or to the maternal breast • Riga-Fede disease- oral condition found, rarely in newborns manifests as an ulceration on the ventral surface of the tongue or on the inner surface of the lower lip. Caused by trauma to the soft tissue from erupted baby teeth. Riga-Fede disease
- 29. ERUPTION SEQUENCE The mandibular central incisors are the first to erupt around 6-8 months of age. The sequence of eruption is :- A – B – D – C – E. The primary dentition is usually established by the age of 3 years.
- 30. Chronology of Primary Dentition Primary (upper) First evidence of calcification (weeks in utero) Crown completed (Months) Eruption (months) Root completed (years) Central 14(13-16) 11/2 10 11/2 Lateral 16 21/2 11 2 Canine 17 9 19 31/4 1st molar 151/2 6 16 21/2 2nd molar 19 11 29 3
- 31. Primary (lower) First evidence of calcification (weeks in utero) Crown completed (Months) Eruption (months) Root completed (years) Central 14(13-16) 21/2 8(6-10) 11/2 Lateral 16 3 13(10-16) 11/2 Canine 17 9 19 31/4 1st molar 151/2 51/2 16(14-18) 21/4 2nd molar 18 10 27 3
- 32. CHARACTERISTICS OF DECIDUOUS DENTITION I. Spacing 2 types of dentition are seen: A) Spaced dentition: usually seen to accommodate the larger permanent teeth in the jaws. • More prominent in the anterior region, and are called ‘physiological spacing’ or ‘developmental spacing’. • Absence of spaces in the primary dentition is an indication that crowding of teeth may occur when the larger permanent teeth erupt.
- 33. Spacing invariably is seen mesial to the maxillary canine and distal to the mandibular canine. These spaces are called as Primate, Simian Or Anthropoid Spaces. This space is used for early mesial shift. The amount of primate space in maxilla is around 1.7mm. & in mandible 1.5 mm
- 34. B)Non- spaced dentition: Teeth are present without any spaces in between the teeth Due to narrow dental arches or if teeth are wider than usual May indicate crowding in developing permanent dentition Initially a deep bite may occur due to the fact that the deciduous incisors are more upright than their successors. Non- spaced dentition
- 35. II. Shallow overjet & overbite Initially a deep bite may occur due to the fact that the deciduous incisors are more upright than their successors. The lower incisal edges often contact the cingulum area of the maxillary incisors. This deep bite is later reduced by: 1. Eruption of deciduous molars. 2. Attrition of incisors. 3. Forward movement of the mandible due to growth deep bite
- 36. III. Almost vertical inclination of anteriors IV. Ovoid arch form
- 37. MOLAR RELATIONSHIP The molar relationship in the primary dentition can be classified into 3 types: 1. Straight/flush terminal plane. 2. Distal step. 3. Mesial step.
- 38. Flush terminal plane:If the distal surface of maxillary and mandibular deciduous second molars are in the same vertical plane; then it is called a flush terminal plane Mesial step:Distal surface of mandibular deciduous second molar is mesial to the distal surface of maxillary deciduous second molar. Distal step:Distal surface of mandibular second deciduous molar is more distal to the distal surface of the maxillary second deciduous molar
- 39. Canine relationship Relationship of maxillary & mandibular deciduous caninnes is one of the most stable in primary dentition Classified as: • Class 1 - mandibular canine interdigitates in embrasure between maxillary lateral and canine. • Class 2 - mandibular canine interdigitates distal to embrasure. Class 1 Class 2
- 40. THE MIXED DENTITION The mixed dentition period begins at around 6 yrs of age with the eruption of the 1st permanent molar. This period can be divided into the following 3 phases:- 1. 1st transitional period. 2. Inter transitional period. 3. 2nd transitional period
- 41. FIRST TRANSITIONAL PERIOD The first transitional period is characterised by: • Emergence of 1st permanent molar • Incisor transition • Establisment of occlusion
- 42. Emergence of 1st permanent molar The mandibular 1st molar is the first permanent tooth to erupt at around 6yrs of age. The location and relation of the 1st permanent molar depends on the distal relationship between the upper and lower 2nd deciduous molars.
- 43. EARLY and LATE MESIAL SHIFT Early mesial shift: The eruptive forces of the 1st permanent molar is sufficient to push the deciduous 1st and 2nd molars forward to close the primate spaces and establish class Ι molar relationship. Late mesial shift: In the cases when the primate spaces are absent the permanent 1st molar drift mesially utilizing the leeway space. Maxilla: 0.9 mm/segment = 1.8 mm. Mandible: 1.7 mm/segment = 3.4mm.
- 44. Primary molar guidance Flush terminal plane → class Ι (early and late mesial shift.) Mesial step → class Ι. Differential growth of mandible in forward direction persists → class ΙΙΙ. Distal step → class ΙΙ.
- 45. Exchange of Incisors During the 1st transitional period the deciduous incisors are replaced by the permanent incisors. The permanent incisors are considerably larger then the deciduous teeth they replace. This difference between the amount of space needed and the amount of space available is called as Incisal liability. The incisor liability is about 7mm in the maxillary arch and 5mm in the mandibular arch..
- 46. This is overcome by 3 factors :- 1. Inter-dental spaces. 2. Inter-canine width. 3. Incisor inclination
- 47. INTER-DENTAL SPACES The physiologic spaces seen in the primary dentition are utilized to partly account for the incisal liability. Maxillary arch- 4mm Mandibular arch- 3mm The permanent incisors are much more easily accommodated in normal alignment in cases exhibiting adequate inter-dental spaces
- 48. INTER–CANINE WIDTH During the transition from the primary incisors permanent incisors an increase in inter-canine width of both maxillary and mandibular arch is observed.
- 49. INCISOR INCLINATION The primary incisors are more upright than their permanent counterparts. Since the permanent incisors are more labially inclined they tend to increase the dental arch perimeter. The incisal angle in primary dentition is 1500 whereas it is about 1230 in permanent dentition.
- 50. INTER TRANSITIONAL PERIOD Contains both sets of dentition. Four permanent incisors, left and right first permanent molar Deciduous canines and deciduous first and second molars. This phase is relatively stable and no change occurs.
- 51. SECOND TRANSITIONAL PERIOD (9 to 10 years)
- 52. Characterised by: 1. Emergence of bicuspids, cuspids,and second permanent molars. 2. Establisment of occlusion
- 53. The second transitional period is characterized by the replacement of deciduous molars and canines by the permanent premolars and cuspids respectively. The combined mesio distal width of the permanent canines and premolars is less than that of the deciduous canines and molars. This excess space is called leeway space of Nance. 1.8mm – maxillary arch. 3.4mm – mandibular arch.
- 54. UGLY DUCKILNG STAGE (Broadbent phenomenon) A transient or self correcting malocclusion is seen in the maxillary incisor region between 8-10 yrs at the time of eruption of the permanent canines. Its typical features are: Flaring of the lateral incisors. Maxillary midline diastema As the developing permanent canines erupt they displace the roots of the lateral incisors mesially. This results in transmitting the force on roots of the centrals which also get displaced mesially. Hence a distal divergence of the two centrals causes midline spacing.
- 55. With the eruption of the canines, the impingement from the roots shift incisally thus driving the incisor crowns medially, resulting in closure of the diastemaas well as the correction of the flared lateral incisors.
- 56. THE PERMANENT DENTITION PERIOD The permanent dentition is considered when all permanent teeth are seen in the dental arches, often by the age of 12 to 14 years. Eruption sequence: Upper: 6-1-2-4-5-3-7-8 Lower: 6-1-2-3-4-5-7-8
- 57. Permanent (upper) First evidence of calcification (weeks in utero) Crown completed (Months) Eruption (months) Root completed (years) Central 3-4 mon 4-5 yr 7-8 yr 10 Lateral 10-12 mon 4-5 yr 8-9 yr 11 Canine 4-5 mon 6-7 yr 11- 12 yr 13-15 1st premolar 11/2 - 13/4 yr 5-6 yr 10-11 yr 12-13 2nd premolar 2-21/4 yr 6-7 yr 10-12yr 12-14 1st molar At birth 21/2-3 yr 6-7 yr 9-10 2nd molar 21/2-3 yr 7-8 yr 12-13 yr 14-16 3rd molar 7- 9 yr 12-16 yr 17-21 yr 18-25
- 58. Permanent (lower) First evidence of calcification (weeks in utero) Crown completed (Months) Eruption (months) Root completed (years) Central 3-4 mon 4-5 yr 6-7yr 9 Lateral 3-4 mon 4-5 yr 7-8 yr 10 Canine 4-5 mon 6-7 yr 9-10 yr 12-14 1st premolar 13/4 - 2 yr 5-6 yr 10-12 yr 12-13 2nd premolar 21/4-21/2 yr 6-7 yr 11-12yr 13-14 1st molar At birth 21/2-3 yr 6-7 yr 9-10 2nd molar 21/2-3 yr 7-8 yr 11-13 yr 14-15 3rd molar 8-10 yr 12-16 yr 17-21 yr 18-25
- 59. Self correcting anomalies Self correcting anomalies Correction(timing/factors involved) I. Predentate period a)Retrognathic mandible Corrects with differential and forward growth of mandible b)Anterior open bite Eruption of primary incisors c)Infantile swallowing pattern During the first year of life with introduction of solid foods in diet
- 60. Self correcting anomalies Correction(timing/factors involved) II. Primary dentition a)Anterior deep bite Corrects with: • Eruption of deciduous molars • Attrition of incisal edges • Forward and downward growth of mandible b)Flush terminal plane • Eruption of first permanent molar • Late shift- leeway space c)Spacing Eruption of first permanent molar d)Edge to edge Eruption of permanent incisors
- 61. Self correcting anomalies Correction(timing/factors involved) III. Mixed dentition a)Anterior deep bite Proprioceptive response condition of patient b)Mandible anterior crowding • Tongue pressure • Incrase in intercanine width c)Ugly duckling stage Maxillary canine eruption d)End on relation • With eruption of first permanent molars • Late mesial shift in non spaced dentition IV. Permanent dentition Overjet and overbite • Decrease with eruption of permanent molars • Differential growth of mandible