Primary Dentition and Eruption

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  • 1.Primary Dentition:Primary Dentition: Anterior and PosteriorAnterior and Posterior Howard Chi, D.M.D.Howard Chi, D.M.D.

2. Learning Objectives Generals of primary dentition Anatomy of primary anteriors Anatomy of primary posteriors Eruption patterns of primary dentition and permanent dentition 3. Generals of Primary Dentition 4. Primary Dentition * Primary teeth emerge in children between the ages of 6 months and 2 years * Beginning at age 6 these teeth are gradually replaced by the permanent teeth 5. Primary Dentition * Primary teeth are often called deciduous teeth * From the Latin to fall off * Common nicknames are milk teeth or temporary teeth 6. Primary Dentition * The teeth function an average of 8 years for maxillary teeth * The teeth function an average of 7.6 years for mandibular teeth * Hold an important role in reserving space for permanent teeth 7. Important Functions Of Sound Primary Teeth 1) Efficient mastication of food 2) Maintenance of a normal facial appearance 3) Formulation of clear speech 4) Maintenance of proper diet 5) Avoidance of infection and pain 6) Maintenance of space and arch continuity 8. Eruption Time Of Primary Dentition * First primary teeth to erupt are usually mandibular central incisors at about 6 months * Last teeth to erupt are the maxillary second molars around 24 months 9. Mixed Dentition * First permanent teeth to erupt are the mandibular first molars and then maxillary first molars * They appear distal to the primary second molars * With their eruption commences the mixed dentition period 10. Mixed Dentition * The roots of primary teeth are completely formed 1 year after emergence of the crown into the mouth * The roots are short lived beginning to resorb in just three years * After exfoliation, the permanent teeth emerge within a few months 11. General Characteristics Of Primary Teeth 1) Primary teeth are smaller in size than permanent teeth 2) They are whiter in color than the analogous permanent teeth 3) They are less mineralized than permanent teeth 12. General Characteristics Of Primary Teeth 4) They have shorter crowns with respect to their roots 5) Crowns have a marked constriction at the cervix 6) The enamel seems to bulge close to the cervical line, rather than gradually tapering 13. General Characteristics Of Primary Teeth 7) The layers of enamel and dentin are thinner than on permanent teeth 8) The pulp cavities are proportionally larger 9) Primary teeth exhibit fewer anomalies 10) The crowns appear bulbous, often with labial or buccal cingula 14. Primary Anterior Dentition 15. General Characteristics Of The Anterior Teeth 1) Usually no depressions on the labial surface of the crowns of incisors 2) There are no mamelons on the incisal edges 3) Facial cervical ridges are prominent 16. General Characteristics Of The Anterior Teeth 4) Cingula are prominent and occupy 1/3 cervicoincisal length 5) The roots are long in proportion to the crown length, and narrow mesiodistally 6) The roots bend labially in their apical 1/3 to 1/2 as much as 10 degrees 17. Proximal Aspect Of Primary Incisors Root Shape * The roots of maxillary incisors are S-shaped, bending toward the lingual in the cervical third to half and then bend labially in the apical half * The roots of mandibular incisors are straight in the cervical half and bend labially in their apical half * This bend help provide space for the developing teeth 18. Primary Canines Uniqueness of Contact Areas: * Mesial and distal contacts are in the middle third of the crowns, with the mesial being located more cervical than the distal (a condition unique to the tooth and one other, which tooth?) D 19. Primary Canines Primary canine root: * Are bulky in the middle and cervical thirds, tapering in the apical third where they bend labially 20. Primary Posterior Dentition 21. 1) The molar crowns are wider mesiodistally, yet shorter cervico-occlusally 2) The second molars are much larger than the first molars 3) The molar crowns have a narrow chewing surface 4) The molar occlusal anatomy is shallow (cusps are short) 5) The buccal cusp tips are not pointed and their slopes meet at very obtuse angles General Characteristics Of The Posterior Teeth 22. 6) There are few grooves or depressions in the crowns 7) The root furcations are near the crown, with little or no root trunk 8) The roots are widely spread beyond the outlines of the crown 9) The roots are thin and slender 10) The second molar roots are spread more widely than the first molar roots General Characteristics Of The Posterior Teeth 23. Primary Molars * Primary first molars are smaller than primary second molars * Primary first molars are quite unique in their shape * Primary second molars have considerable likeness to permanent first molars * Maxillary molars have three roots and mandibular possess two 24. Primary Maxillary First Molar Uniqueness for primary maxillary first molar: 1. Resembles a permanent premolar* 2. Groove pattern is H shape 25. Primary Mandibular First Molar Uniqueness for primary mandibular first molar: 1. Resembles no other tooth in either primary or permanent dentition* 2. Two roots: Mesial and distal. With the Mesial root wider and longer than the distal (opposite of permanent mandibular molars (in length)) 26. Eruption Patterns:Eruption Patterns: Primary and PermanentPrimary and Permanent DentitionDentition 27. Eruption and Resportion Eruption: Historically denotes the eruption of tooth through the gingiva Resorption: The permanent tooth in its follicle attempts to force its way into the position held by its predecessor The pressure brought to bear against primary root causes resorption of the root until exfoliated 28. Dental Age Has been assessed on the basis of the number of teeth at each chronological age Calcification of the organic matrix, root formation, and tooth eruption are important indicators of dental age Dentition is the single best physiological indicator of chronological age in juveniles 29. Primary Tooth Eruption Sequence 1) Central Incisors 2) Lateral Incisors 3) First Molars 4) Canine 5) Second Molars 30. Primary Mandibular Incisors Centrals erupt at a mean age of 6 months Laterals erupt at a mean age of 7 months (occasionally, all lower incisors will erupt before the maxillary incisors) 1122 31. Primary Maxillary Incisors Maxillary central follow mandibular central by mean age of 1 months and erupt at 7 months 1122 22 32. Laterals erupt at a mean age of 9 months Primary Maxillary Incisors 1122 2233 33. Primary First Molars First molars erupt at a mean age 12-14 months Mandibular usually erupts first 1122 2233 44 55 34. Primary Canines Mandibular canine erupts at a mean age of 16 months Maxillary canine erupts at mean age of 18 months 66 77 1122 2233 44 55 35. Primary Second Molars Mandibular second molars erupt at a mean age of 20 months 66 77 1122 2233 44 55 88 36. Maxillary second molars erupt at a mean age of 24 months Primary Second Molars 66 77 1122 2233 44 55 88 99 37. Succedaneous Teeth (Teeth that replace a primary predecessor) 1) Permanent Incisors 2) Permanent Canines 3) Permanent Premolars 38. Permanent First Molar Begin to calcify at about the time of birth Emerge distal to primary second molar 39. First molars are the first to erupt Occurs at 6 years of age and are occasionally called "6-year molars" Permanent First Molar 11 22 40. Permanent Mandibular Central Incisor Second permanent tooth to emerge into the oral cavity Mandibular central erupt at 6 years 33 41. Permanent Maxillary Central Incisor 33 44 Maxillary central at age7-8 years 42. Permanent Mandibualr Lateral Incisor Mandibular lateral at 7-8 years (may erupt along with the maxillary central incisors) 33 44 55 43. Permanent Maxillary Lateral Incisor 33 44 55 66 Maxillary lateral at age8-9 years 44. Permanent Mandibular Canine Mandibular canines erupt following the lateral incisors between ages of 9-10 years 7711 22 33 44 55 66 45. Maxillary First Premolar Generally erupts at 10-11 years old following the mandibular canine 7711 22 33 44 55 6688 46. Maxillary Second And Mandibular First Premolars Follow the maxillary first premolars Generally erupt at 10-12 years old 7711 22 33 44 55 668899 1010 47. Mandibular Second Premolar And Maxillary Canine Follow the maxillary second premolars and mandibular first premolars Generally erupt at age 11-12 years 11 22 33 44 55 668899 10101111 1212 77 48. Permanent Second Molars Erupt at 11-13 years of age Mandibular usually erupts first called "12-year molar" 11 22 33 44 55 668899 10101111 1212 771313 1414 49. Permanent Third Molars Erupt at age 17 or later Considerable jaw growth required to allow room for these teeth 11 22 33 44 55 668899 10101111 1212 771313 1414 1515 1616