NBDE Part 1 - Dental Anatomy UPDATED ACTUAL Questions
and CORRECT Answers
What is Turner Tooth? - Focal Enamel Hypoplasia (underdevelopment of tissue/organ) resulting from
inflammation or trauma during development of an individual tooth
- Typically caused by local factors including injury to the developing permanent
tooth through extraction of primary, or infection of the primary tooth
- Permanent tooth erupts into mouth with hypocalcification spot due to insult
from abscessed predecessor
What are the Dentition Periods? 1. Primary Dentition = 6 months - 6 years
2. Mixed Dentition = 6 years - 12 years
3. Permanent Dentition = After last primary exfoliates
What is the Universal Tooth Designation System for
Primary Dentitions?
,What are the Differences between Primary teeth vs Primary vs Permanent
Permanent teeth? 1. Smaller in size
- Anterior: Wider M-D and shorter I-G
- Posterior: Thinner M-D and shorter I-G
2. Whiter enamel (↑ opacity)
3. Broad, flat contacts
- Flatter B/L surfaces
4. Prominent cervical bulge
- The primary central incisor exhibits prominent cervical ridge both on facial
and lingual
5. Smaller crown-to-root ratio
6. Narrower crowns/occlusal table at CEJ
7. Thinner, even layers of enamel & dentin
8. Enamel rods in gingival 1/3 extends occlusally from DEJ
- Permanent teeth extends gingivally
9. Roots narrower, longer, & more divergent
- Gives space for succedaneous tooth
10. Short root trunks
- Molars lack an identifiable root truck (small/absent)
11. Large pulp horns and pulp chambers
12. Pulp horns closer to outer surface of tooth (especially to mesial pulp horn)
- Shorter distance for cavity to reach pulp
Pictures of Primary Teeth
What are the Characteristics of Primary Teeth? 1. Primary teeth are less mineralized = more worn
2. Difference in arch space from primary and permanent is 2-4mm
3. . Mamelons that remain after age 10 indicate an open bite
4. . Calcification of primary roots completed at 3-4 years old
5. . Primary spacing for anterior teeth are most frequently caused by growth of
dental arch
6. Delayed resorption of primary incisors cause permanent incisors to erupt
lingually (shark teeth)
Age Estimates of Eruption Teeth - No teeth ~ 0-6 months old
- Lower central incisors erupting ~ 6 months old - - All primary incisors ~ 12-18
months old
- All primary teeth ~ 3 years to 6 years old
- Mobile lower central incisors ~ 6 years old
- Erupting permanent first molars ~ 6 years old
- Mixed dent. (12 primary/12 permanent) ~ 8-10 y/o
- All permanent dentition ~ 12+ years old
,What are the Eruption Times for Primary Dentition? 1. Last primary tooth to erupt is the Max. 2nd molar
2. First primary tooth to erupt are Mand. central incisors
3. Around 1 year, child is expected to have erupted primary Max and Mand.
incisors and M1s
- Parent notices new primary tooth at 12 months, most likely a Mand. M1 (12 month
molar)
4. Primary M2s expected to erupt around child's 2nd birthday
What are the Rule of 4? - Eruption of 4 teeth every 4 months
- Start with 4 teeth at 7 months
What are the Eruption Times for Permanent Dentition?
What Occurs in the Mixed Dentition Period Mixed Dentition = 6 years - 12 years
a) Age 6
- Get Mand. Molars at age 6
- By 6 have 20 primary and 4 permanent M1s
b) Age 7
- Have 18 primary and 6 permanent (4 perm molars, 2 mand. perm central
incisors)
c) Age 8
- 12 primary + 12 permanent
- Have Permanent M1s, central & lateral incisors, primary canines & molars
- Permanent Max. M1 have no distal contact yet
d) Age 9
- 12 Primary teeth remain in the mouth (primary canine and 2 molars per quadrant
x4)
e) Age 10
- Perm. teeth expected are central & lateral incisors, first premolars, M1s and
Mand. Canine
- Expect root of Perm M1 to be finished forming and calcifying (2-3 years after
eruption)
What are the 3 Cardinal Eruption Rules 1. Girls teeth erupt BEFORE Boys
2. Mandibular erupt BEFORE Maxillary
3. Teeth of slender kids erupt BEFORE fat kids (too much tissue)
, What are the Characteristics of Eruption? Eruption
1. The movement of tooth through the gums so that the clinical crown slowly gets
longer
- NOT exfoliation
2. Permanent teeth begin to form at 4 months in utero (Mand. M1)
3. First succedaneous to erupt is the Mand. Central incisors at 6-7 yr old
- NOT Mand. M1
4. Follicles of developing permanent incisors are in a position lingual to the
deciduous roots
- When a tooth is partially resorbed by the developing tooth underneath it, the
FACIAL part of the tooth is the longest and more securely attached to the gingiva
- First evidence of root resorption on a primary incisor is seen on the lingual root
surface
What are the Calcification Times? 1. Permanent Max and Mand. M1s begin to calcify at birth
- Begin to form at 4 months in utero
2. Initiation of calcification for mandibular central incisors is 3-4 months
3. Permanent M3s begin to calcify at 8-10 yrs of age
Primary Calcification Timeline in utero
1. Central incisors - 14 weeks
2. Lateral incisors - 16 weeks
3. Canines - 17 weeks
4. 1st Molar - 15.5 weeks
5. Lower 2nd molar - 18 weeks
6. Upper 2nd molar - 19 weeks
Permanent Initial Calcification
1. Both 1st molars at birth
2. Both central incisors: 3-4 months
3. Mandibular lateral: 3-4 months
- Maxillary lateral: 10-12 months
4. Both canines: 4-5 months
5. Both 1st premolars: 1.5-2 years
6. Both 2nd premolars: 2-2.5 years
7. Both 2nd molars: 2.5-3 years
8. Maxillary 3rd molar: 7-9 years
- Mandibular 3rd molar: 8-10 years
What is the Developmental Time for Teeth Formation? 1. Entire primary dentition initiated between 6-8 weeks embryonic develolpment
2. Succedaneous permanent teeth initiate between 5 month (20th week) in utero
and 10th month after birth
3. Permanent molars between 5 month (20 week) in utero (first molar) and 5th
year of life (3rd molar)
and CORRECT Answers
What is Turner Tooth? - Focal Enamel Hypoplasia (underdevelopment of tissue/organ) resulting from
inflammation or trauma during development of an individual tooth
- Typically caused by local factors including injury to the developing permanent
tooth through extraction of primary, or infection of the primary tooth
- Permanent tooth erupts into mouth with hypocalcification spot due to insult
from abscessed predecessor
What are the Dentition Periods? 1. Primary Dentition = 6 months - 6 years
2. Mixed Dentition = 6 years - 12 years
3. Permanent Dentition = After last primary exfoliates
What is the Universal Tooth Designation System for
Primary Dentitions?
,What are the Differences between Primary teeth vs Primary vs Permanent
Permanent teeth? 1. Smaller in size
- Anterior: Wider M-D and shorter I-G
- Posterior: Thinner M-D and shorter I-G
2. Whiter enamel (↑ opacity)
3. Broad, flat contacts
- Flatter B/L surfaces
4. Prominent cervical bulge
- The primary central incisor exhibits prominent cervical ridge both on facial
and lingual
5. Smaller crown-to-root ratio
6. Narrower crowns/occlusal table at CEJ
7. Thinner, even layers of enamel & dentin
8. Enamel rods in gingival 1/3 extends occlusally from DEJ
- Permanent teeth extends gingivally
9. Roots narrower, longer, & more divergent
- Gives space for succedaneous tooth
10. Short root trunks
- Molars lack an identifiable root truck (small/absent)
11. Large pulp horns and pulp chambers
12. Pulp horns closer to outer surface of tooth (especially to mesial pulp horn)
- Shorter distance for cavity to reach pulp
Pictures of Primary Teeth
What are the Characteristics of Primary Teeth? 1. Primary teeth are less mineralized = more worn
2. Difference in arch space from primary and permanent is 2-4mm
3. . Mamelons that remain after age 10 indicate an open bite
4. . Calcification of primary roots completed at 3-4 years old
5. . Primary spacing for anterior teeth are most frequently caused by growth of
dental arch
6. Delayed resorption of primary incisors cause permanent incisors to erupt
lingually (shark teeth)
Age Estimates of Eruption Teeth - No teeth ~ 0-6 months old
- Lower central incisors erupting ~ 6 months old - - All primary incisors ~ 12-18
months old
- All primary teeth ~ 3 years to 6 years old
- Mobile lower central incisors ~ 6 years old
- Erupting permanent first molars ~ 6 years old
- Mixed dent. (12 primary/12 permanent) ~ 8-10 y/o
- All permanent dentition ~ 12+ years old
,What are the Eruption Times for Primary Dentition? 1. Last primary tooth to erupt is the Max. 2nd molar
2. First primary tooth to erupt are Mand. central incisors
3. Around 1 year, child is expected to have erupted primary Max and Mand.
incisors and M1s
- Parent notices new primary tooth at 12 months, most likely a Mand. M1 (12 month
molar)
4. Primary M2s expected to erupt around child's 2nd birthday
What are the Rule of 4? - Eruption of 4 teeth every 4 months
- Start with 4 teeth at 7 months
What are the Eruption Times for Permanent Dentition?
What Occurs in the Mixed Dentition Period Mixed Dentition = 6 years - 12 years
a) Age 6
- Get Mand. Molars at age 6
- By 6 have 20 primary and 4 permanent M1s
b) Age 7
- Have 18 primary and 6 permanent (4 perm molars, 2 mand. perm central
incisors)
c) Age 8
- 12 primary + 12 permanent
- Have Permanent M1s, central & lateral incisors, primary canines & molars
- Permanent Max. M1 have no distal contact yet
d) Age 9
- 12 Primary teeth remain in the mouth (primary canine and 2 molars per quadrant
x4)
e) Age 10
- Perm. teeth expected are central & lateral incisors, first premolars, M1s and
Mand. Canine
- Expect root of Perm M1 to be finished forming and calcifying (2-3 years after
eruption)
What are the 3 Cardinal Eruption Rules 1. Girls teeth erupt BEFORE Boys
2. Mandibular erupt BEFORE Maxillary
3. Teeth of slender kids erupt BEFORE fat kids (too much tissue)
, What are the Characteristics of Eruption? Eruption
1. The movement of tooth through the gums so that the clinical crown slowly gets
longer
- NOT exfoliation
2. Permanent teeth begin to form at 4 months in utero (Mand. M1)
3. First succedaneous to erupt is the Mand. Central incisors at 6-7 yr old
- NOT Mand. M1
4. Follicles of developing permanent incisors are in a position lingual to the
deciduous roots
- When a tooth is partially resorbed by the developing tooth underneath it, the
FACIAL part of the tooth is the longest and more securely attached to the gingiva
- First evidence of root resorption on a primary incisor is seen on the lingual root
surface
What are the Calcification Times? 1. Permanent Max and Mand. M1s begin to calcify at birth
- Begin to form at 4 months in utero
2. Initiation of calcification for mandibular central incisors is 3-4 months
3. Permanent M3s begin to calcify at 8-10 yrs of age
Primary Calcification Timeline in utero
1. Central incisors - 14 weeks
2. Lateral incisors - 16 weeks
3. Canines - 17 weeks
4. 1st Molar - 15.5 weeks
5. Lower 2nd molar - 18 weeks
6. Upper 2nd molar - 19 weeks
Permanent Initial Calcification
1. Both 1st molars at birth
2. Both central incisors: 3-4 months
3. Mandibular lateral: 3-4 months
- Maxillary lateral: 10-12 months
4. Both canines: 4-5 months
5. Both 1st premolars: 1.5-2 years
6. Both 2nd premolars: 2-2.5 years
7. Both 2nd molars: 2.5-3 years
8. Maxillary 3rd molar: 7-9 years
- Mandibular 3rd molar: 8-10 years
What is the Developmental Time for Teeth Formation? 1. Entire primary dentition initiated between 6-8 weeks embryonic develolpment
2. Succedaneous permanent teeth initiate between 5 month (20th week) in utero
and 10th month after birth
3. Permanent molars between 5 month (20 week) in utero (first molar) and 5th
year of life (3rd molar)
