NBDE Part 1 - Dental Anatomy
What is Turner Tooth? - ANS - *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? - ANS *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? - ANS
What are the Differences between *Primary* teeth vs *Permanent* teeth? - ANS Primary vs Permanent
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 - ANS
What are the Characteristics of Primary Teeth? - ANS 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 - ANS - 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? - ANS 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? - ANS - Eruption of 4 teeth every 4 months
- Start with 4 teeth at 7 months
What are the Eruption Times for Permanent Dentition? - ANS
What Occurs in the Mixed Dentition Period - ANS *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 - ANS 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? - ANS 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? - ANS 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
What is Turner Tooth? - ANS - *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? - ANS *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? - ANS
What are the Differences between *Primary* teeth vs *Permanent* teeth? - ANS Primary vs Permanent
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 - ANS
What are the Characteristics of Primary Teeth? - ANS 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 - ANS - 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? - ANS 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? - ANS - Eruption of 4 teeth every 4 months
- Start with 4 teeth at 7 months
What are the Eruption Times for Permanent Dentition? - ANS
What Occurs in the Mixed Dentition Period - ANS *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 - ANS 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? - ANS 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? - ANS 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
