Anatomy of Primary Teeth Flashcards
What are the typical characteristics of primary central incisors (MX and MN) that differ from the permanent set?
Mamelons are not visible
The CEJ is squashed- creating a labial and lingual bulge called a cervical constriction
The roots are round in cross section, but not often seen because they are reabsorbed
MX: M→D is equal or wider than C→I dimension = short and wide crown. M-I angle is sharper, D-I is more round and blunt. Also a shallow lingual fossa.
MN: Crown flares a lot. With M→ D blunt/round
What is the developmental sequence for Central Incisors and Lateral Incisors?
Central: MN proceeds MX
1st calc = 4 months in utero (Lateral: 4.5 months in utero)
Emerge = 8-10 months (Lateral: 9-13 months)
Exfoliate = 6-7 years (Lateral: 7-8 years)
What are the typical characteristics of the Lateral Incisors (MN and MX)?
MX: Labial is smaller than 5,1.
MN: Labial is more flared distally= bigger than 7,1
Root = compressed M→D = oval in cross section
No mamelons
What is the developmental sequence of canines MX and MN?
1st calc = 5 months utero
Emergence = 18 months
Exfoliation = 12 years MX, 9 years MN
What are the distinguishing characteristics of the MX vs MN canines?
And how does the root differ to the incisors?
Crown Labial:
MX= Shorter and bulbous
*mesial cusp slope is longer than distal = pointy sharp cusp tip
MX = longer than MX
*mesial slope shorter than distal
Roots are long, more triangular that central and laterals.
What are the main distinguishing features of the primary anterior teeth compared to permanent anterior teeth?
- Smaller and whiter
- Crowns are wider M→D than C→I (permanent teeth are longer and narrower)
- Prominent cervical ridge (bulge at CEJ) - due to cervical constriction.
- Roots are longer and slender
- No mamelons present incisors
Describe the Mx 1st primary molar (5, 4)
- 4 cusps, MP is the tallest and sharpest, DP can be missing
- 2 fossae, central and medial- linked by developmental groove.
- 3 roots- splayed
- May have oblique ridge linking MP→DB
- CEJ- cervical constriction = buccal bulge
Describe the roots of the MX primary molars
X3 roots= M + D root (buccal) and 1 palatal which is the longest
Roots are more splayed in second molar.
Describe the MX 2nd Primary Molar (5,5) and compare it to the MX 1st Permanent Molar (1,6)
- It is larger than 1st MX molar.
- Cusps are sharper and smaller than in 1,6.
- MP cusp is biggest and has oblique ridge DB→MP like 1,6
- Marked cervical bulge constriction= pronounced on buccal aspect
- May have tubercle on MP cusp
- Root trunk is short and 1 root canal. Root gets reabsorbed.
What are the differences between MX primary 1st molar and MX permanent 1st molar?
- Pronounced cervical constriction = buccal bulge
- Root trunk is smaller
- Roots are longer and slender, more splayed
What are the differences between MX primary 1st molar and MX 1st premolar?
- Cervical constriction- buccal bulge
- Primary has 3 roots that are more splayed, not 2 roots.
- Primary has 4 cusps, not 2 cusps
- Primary may have oblique ridge
Identify this primary molar and describe its typical features
Mandibular 1st Primary Molar- (7,4)
- Most unique looking tooth,
- 4 cusps, Mesial crown is high - MB cusp and MP cusp (sharper) are both more developed
- *Noticeable buccal curve/bulge at cervical ⅓ → CEJ dips apically at mesial root.
- ZigZag developmental groove
- Roots are often twice as long as crown, flare and short root trunk
When do mandibular molars erupt?
After lower incisors, skips canines
Describe the MN 2nd Primary Molar
7.5
- Much larger than 7,4.
- Resembles MN permanent 1st molar - though crown is rounder
- Cervical constriction- bulge
- 5 cusps, (x3 buccal cusps like 3,6)
- 2 roots
- Roots are twice as long as crown, flare and short root trunk
What are the main differences between primary vs permanent molars?
- Predecessors of premolars, though morphologically more similar to permanent molars = 2nd primary molar MX has oblique ridge like 1,6. 2nd primary molar MN has 3 buccal cusps like 3,6.
- Constricted cervical region = buccal bugle
- Roots twice as long as crown, more flared
- Roots undergo resorption
- Pulpal forms are higher
- Enamel is thinner and more consistent in thickness
Draw and compare Central incisors MN and MX
Draw and compare lateral incisors MN and MX
Draw and compare upper and lower canines
Draw MX Primary 1st Molar and Permanent 1st Molar FROM Proximal view
Draw occlusal view of MX 1st and 2nd Molars
Draw the proximal and occlusal view of MN 1st and 2nd molars
What is the Leeway Space of Nance?
Premolars are smaller than primary molars for space, to prevent crowding in mixed dentition. Specifically, 1st permanent molar will move mesially-
1.5 mm for MX
and 2.5 mm for MN
When do teeth finish erupting?
2.5 years
What is the importance of primary teeth?
- list 4 things
- Growth and development of muscles of mastication + Bones of MN and MX
- For location, alignment and occlusion of permanent dentition
- For speech
- For eating
What is the emergence generally of primary teeth?
6-8 months to 2.5 years
What is exfoliation and where does it begin?
The shedding of primary dentition.
Begins at the apical end of the tooth root- resorption.
The root is resorbed- tooth root structure is taken back by the body.
What are the main differences between morphology of primary and permanent teeth?
x6
Primary teeth:
- enamel and dentin is thinner
- whiter in colour
- broad and flat contact areas
- Cervical constriction- bulge prominent
- Smaller overall size
- Narrower roots- more splayed
- Enamel rods in cervical area are directed occlusally, compared to cervically in permanent
How does the cavity preparation Class 2 restoration in primary teeth differ to permanent teeth?
What other structure do you need to consider in primary teeth?
In primary teeth enamel rods in cervical area are directed occlusally, compared to cervically in the permanent teeth.
Pulp cavity. Because pulp has a higher volume and enamel and dentine is thinner- therefore it’s easier to get to with caries .
Draw and identify the visual differences between primary and permanent molars
Why can you sometimes see the permanent tooth directly as primary tooth exfoliates?
Resorption of primary teeth (root) guides the succedaneous tooth into correct alignment.
The tooth can follow the resorbing root until the primary tooth exfoliates
