27-Anatomical + Physiological features of primary teeth

Question 1

Primary teeth

Answer 1

20 in total

• 4 incisors per jaw
• 2 canines per jaw
• 4 molars per jaw

Crown

• Shorter crown than permanent teeth
• Blue-whitish colour
• Enamel + dentin layers thinner
• Pulp larger in relation to crown size
• Pulp horns closer to outer surface of tooth

Roots

• Shorter
• Roots of molar more diverging
• Canals are not narrowed w/age

Question 2

1° Mandibular incisors

Answer 2

• From buccal aspect ⇢ almost symmetrically flat
• No development grooves or mamelons
• Crown ⅓ length of root
• Cingulum on lingual surface
• Lateral incisor longer + narrower than central incisor
• Lateral incisor ⇢ distal incisal angle more rounded than central
• Pulp of lateral incisor has similar dimensions but smaller than central

Question 3

1° Maxillary incisors

Answer 3

• Crown shape is square
• Slightly rounded incisal edge in distal-incisal angle
• Lateral incisors ⇢ rectangular crown w/ expressed distal incisal angle
• Central incisor ⇢ only tooth in human dentition that has mesiodistal dimension > crown heights
• Flat labial surface + prominent lingual cingulum
• Root is conical + ∼2.5 x as long as crown height

Question 4

1° canines

Answer 4

• Crowns shape is square
• Distal incisal angle = slightly rounded incisal edge

Question 5

1° Molars

Answer 5

• Pulp horns exposed superficially, especially medial ones
• Larger pulp chamber
• Dentin layer over pulp thicker compared to permanent
• Longer + thinner roots
• Roots of molars diverging nearer to cervix
• Roots diverged strongly apically ⇢ creates space for development of permanent tooth germ
• Narrow occlusal surface + narrow neck in cervical distension
• Broad occlusal surface
• Buccal + lingual walls converge occlusally

Question 6

1st mandibular 1° molar

Answer 6

• overdeveloped mesial-gingival 5th cusp
• Wide + shallow mesial-buccal pulp horn ⇢ difficult to elaborate bucco-mesial cavity
• 3 distinct fossae ⇢ medial, medio-lingual cusp + central
• 3 or 4 pulpal horns ⇢ largest is bucco-mesial horn
• 2 roots + 3 canals
• medial root = 2 canals
• distal root = 1 canal

Question 7

1st maxillary 1° molar

Answer 7

• occlusal surface has 3 cusps
• gives tooth a square look
• 3 slender roots beneath each cusp tip
• Furcation of roots begins at CEJ
• 3rd distobuccal cusp
• Prominent buccal cervical ridge
• Mesiobuccal pulp horn most prominent
• 3 canals + 3 roots ⇢ 2 vestibular + 1 palatal

Question 8

2nd mandibular 1° molar

Answer 8

• 5 cusps ⇢ 3 buccal + 2 lingual
• Smaller than mandibular 1st molar
• Enamel uniformly 1.2mm thick
• Vestibular 3 cusps ⇢ central largest > medial > distal
• 2 roots ⇢ narrow mesiodistally, broad buccolingually
• 5 pulp horns for 5 cusp tips ⇢ mesiobuccal longest

Question 9

2nd maxillary 1° molar

Answer 9

• Last primary teeth to erupt
• Smaller than maxillary 1st molar
• 4 cusps ⇢ 2 buccal + 2 lingual
• Oblique ridge ⇢ connects distobuccal cusp + distal cusp ridge of mesiolingual cusp
• Carabelli’s cusp ⇢ medio-lingually in middle ⅓ of crown (5th cusp)
• 4/5 pulp horns ⇢ mesiobuccal largest
• 3 roots ⇢ 2 buccally + 1 orally