1. Chapter 6: Primary (and Mixed) Dentition

2. I. Background Information
Definitions
Dental Formulae
Functions of the Primary Dentition

3. A. Definitions Primary (or deciduous) dentition
Permanent (or secondary or adult) dentition

4. Primary Dentition: Location and Universal Identification with Letters

5. B. Dental Formulae for Primary Dentition Is a Ratio of the Number of Each Tooth Class per Maxillary Quadrant Over Mandibular Quadrant. Note: No Primary Premolars
Incisors = 2/2
Canines = 1/1
Molars = 2/2

6. Dental Formulae for Secondary (Adult) Dentition Is a Ratio of the Number of Each Tooth Class per Maxillary Quadrant Over Mandibular Quadrant
Succedaneous teeth
Incisors = 2/2 (same as primary)
Canines = 1/1 (same as primary)
Premolars = 2/2 (replace primary molars)
Molars = 3/3
(erupt distal to spaces filled with primary teeth so are not succedaneous)

7. C. Functions of Primary Dentition
Chewing (mastication)
Support for lips and cheeks
Formulation of speech
Maintain arch space and room for secondary teeth

8. Adult Tooth Crowding Due to Premature Primary Tooth Loss
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9. II. Developmental Data for Primary and Secondary Teeth
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Important times for eruption
Crown and root development

10. A. Tooth Eruption Times (Approximate)
Birth to 6 or 8 months: no teeth erupted
Primary teeth erupt from 6 months–2 years
All 20 primary teeth present from 2–6 years
Mixed dentition from 6–12 years
Only adult teeth after 12 years
Last permanent teeth erupt (third molars) = late teens/early 20s

11. B. Crown and Root Development (Primary Teeth)
Primary crowns begin to form at 6 months in utero
Crowns complete (about 10 months after beginning)
Root formation takes place during eruption process and emergence
Roots complete (1½–3 years after emergence)
Exfoliation and replacement with permanent (succedaneous) teeth (6–12 years)

12. Crown and Root Development (Secondary Teeth)
Secondary crowns begin to form/calcify (beginning at birth for first molars through 8–10 years for beginning third molars)
Crowns complete calcification about 3 (to 4+) years prior to eruption
Roots complete (about 3 years after emergence)

13. Order of Emergence of Primary Teeth (Between 6 Months and 2 Years)
First: Mandibular central incisor (6 months)
Second: other incisors (maxillary lateral incisors last)
Third: First molars
Fourth: Canines
Fifth: Second molars (at about 2 years)

14. Model Depicting 3-Year-Old (Note Tooth Crowns Forming in Jaw Bones)

15. Order of Emergence of Secondary Teeth (Between 6 Years and Late Teens/Early 20s)
First: First molars followed closely by mandibular central incisors (6 years)
Next: Other incisors (7–9 years)
Then: Mandibular canines (9 years)
Premolars (10–12 years)
Maxillary canines (12 years)
Second molars (12 years)
Third molars (late teens)

16. Model of 9-Year-Old (Note: Adult Incisors and First Molars Have Erupted)

17. 8-Year-Old (Adult Canines and Premolars Have Not Yet Erupted)
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18. III. Dentition Traits of All Primary Teeth (Compared to Secondary)
Smaller than secondary tooth of same name
Marked cementoenamel junction (CEJ) constriction and cervical crown bulges
Relatively long roots compared to crowns
More wear since less mineralized

19. Dentition Traits of All Primary Teeth (Compared to Secondary [cont.])
Thinner enamel and dentin layers
Whiter
Fewer anomalies

20. Prominent cervical ridges Prominent lingual cingula
Dentition Traits of Anterior Primary Teeth (Compared to Secondary [cont.])
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Anteriors:
Prominent cervical ridges
Prominent lingual cingula
No labial depressions, mamelons, or perikymata
Anterior roots: thin mesiodistally
Anterior roots bend labially in apical third

21. Dentition Traits of Primary Molars (Compared to Secondary)
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Prominent mesial cervical ridge (bulges) with exaggerated cervical line curve apically on facial
Crowns taper narrower toward occlusal with narrow occlusal table
Wide mesiodistally versus occlusogingivally

22. Primary Molars (Compared to Secondary [cont.])
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Shallow occlusal anatomy: few grooves or depressions
Second molars are larger than firsts
Enamel rods slope occlusally near CEJ

23. Primary Molar Roots (Compared to Secondary)
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Root furcations are near crown (small root trunks)
Roots thin and slender
Roots diverge considerably (to make room for forming adult premolars within the jaw bones)

24. IV. Class and Type Traits of Primary Teeth
Primary Incisor Traits (Central and Lateral)
Primary Canine Traits
Primary Molar Traits (First and Second)

25. A. Primary Incisor Traits
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26. 1. Incisors: Labial View
Outline: All are longer incisocervically than mesiodistally EXCEPT that maxillary central incisor is wider mesiodistally (otherwise similar to secondary incisors)

27. Incisors: Labial View [cont.]
Smooth surfaces, minimal depressions
Roots relatively much longer than crowns (before resorption) compared to secondary

28. 2. Incisors: Lingual View
Prominent, large cingula
Marginal ridges most prominent on maxillary central incisors; mandibular lingual anatomy less distinct

29. 3. Incisors: Proximal Views
Quite wide labiolingually in cervical third
Cervical line (CEJ) same shape as secondary: curve greater on mesial
All roots bend facially in apical third
Maxillary incisor roots also bend lingually in cervical half

30. 4. Incisors: Incisal View
Maxillary central is much wider mesiodistally than faciolingually compared to maxillary lateral
Mandibular incisors: mesiodistal almost = faciolingual

31. B. Primary Canines: Traits
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32. 1. Primary Canine: Labial View
Outline: maxillary = about as wide and long; mandibular = like secondary: longer incisocervically than mesiodistally
Cervical lines: similar to secondary
Roots taper to blunt apex

33. Primary Canine: Labial View (Maxillary)
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Contact areas: UNIQUE: mesial contact of maxillary canine crown more cervical than distal (only other tooth is mandibular first premolar)

34. Primary Canine: Labial View (Maxillary [cont.])
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Cusp ridges
Maxillary = pointed and UNIQUE: mesial cusp ridges longer than distal (only other tooth like this is secondary maxillary first premolar)

35. Primary Canine: Labial View (Mandibular)
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Cusp ridges
Mandibular = also quite pointed but similar to secondary canine: mesial cusp ridges shorter than distal

36. 2. Primary Canine: Lingual View
Maxillary ridges
Cingulum and marginal ridges more prominent
Lingual ridge with mesial and distal fossae (similar to secondary)
Mandibular ridges
Faint ridges

37. 3. Primary Canine: Proximal Views
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Outline: Cervical third even thicker than primary incisor
Pronounced labial and lingual cervical bulges with pronounced concave “S” shape on maxillary canines

38. Primary Canine: Proximal Views [cont.]
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Maxillary cusp tips positioned labial to root axis, but mandibular = lingual (as in secondary)
Cervical lines (CEJ) similar to secondary: more curve on mesial
Roots: roots bent labially in apical third

39. 4. Primary Canines: Incisal View
Maxillary canine wider mesiodistally than faciolingually (less so on mandibular)
Mandibular canine outlines are diamond shaped from incisal

40. C. Primary Molar Traits
Both types of maxillary molars have three roots (mesiobuccal, distobuccal, and palatal)
Mandibular molars have two (mesial and distal)

41. Primary Molar Traits [cont.]
All are wider mesiodistally than premolars that will replace them

42. Primary Molar Traits [cont.]
All have prominent buccal bulges (mesiobuccal)

43. Primary Molar Traits [cont.]
Cervical lines curve apically in mesial half of buccal surface

44. Primary Second Molar Traits
Primary second molars resemble secondary first molars

45. Primary Second Molar Traits [cont.]
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Primary second molars resemble the adjacent secondary first molar in that arch just distal to them after age 6
Primary second molars are smaller than permanent first molars

46. Primary Maxillary Second Molar (Type Traits)
Crown similar to secondary maxillary first molar but smaller
Four cusps plus Carabelli
Oblique ridge
Mesiobuccal cusp is almost equal to mesiolingual cusp (while mesiolingual cusp is largest on permanent first molars)

47. Primary Mandibular Second Molar (Type Traits)
Crown similar to secondary mandibular first molar but smaller
Five cusps: three buccal (mesiobuccal, distobuccal, distal) and two lingual (mesiolingual and distolingual)

48. Primary Mandibular Second Molar (Type Traits [cont.])
Crown similar to secondary mandibular first molar but smaller
However, distobuccal cusp is widest and mesiobuccal and distal cusps are almost same size (while distal cusp is smallest on permanent first molars)

49. Primary First Molar Traits
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Primary First Molar Traits
Primary first molar crowns are unique in shape
Occlusal view of a primary maxillary first molar somewhat resembles a maxillary premolar
Primary mandibular first molars resemble no other tooth
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50. Primary Maxillary First Molar (Type Traits)
Crown from occlusal view is similar to maxillary premolar (two prominent cusps = mesiobuccal and mesiolingual) but also very small distobuccal and distolingual cusps (as on secondary molars)
Crowns are slightly wider faciolingually than mesiodistally

51. Primary Maxillary First Molar (Type traits [cont.])
But from buccal: are wider than high (similar to secondary molars)
Occlusal grooves may form “H” pattern

52. Primary Mandibular First Molar (Type Traits)
Crown resembles no other tooth
Four cusps (mesiobuccal, distobuccal, mesiolingual, distolingual)
Wider mesiobuccally than high occlusocervically
Very prominent mesiobuccal cervical ridge or bulge with more apical cervical line in mesial half of buccal surface

53. Primary Mandibular First Molar (Type Traits [cont.])
Prominent mesial transverse ridge and mesial marginal ridge
Prominent mesiolingual cusp
Occlusal table wider buccolingually in distal half

54. Groove Patterns of All Primary Molars
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55. V. Pulp Cavities of Primary Teeth
Pulps are relatively larger in proportion to tooth than secondary pulps
Molar pulp chambers are located mostly in crown (due to short root trunk)
Narrow pulp horns located beneath cusps
Pulp size makes it easier to expose during tooth preparation

56. Estimate the Dental Age

57. Estimate the Dental Age
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58. Estimate the Dental Age

59. Identify the Teeth in this Mixed Dentition