Deciduous Dentition Morphology

Question 1

What is the shedding process called? When does this process occur?

Answer 1

Exfoliation, usually begins 2-3 years post complete root formation

Question 2

What are some differences between primary and permanent teeth?

Answer 2

• Primary has a smaller crown/root ratio
• Primary molars wider mesiodistally than permanent premolars
• roots are narrower at the CEJ in primary
• cervical ridges are more bulky
• narrower occlusal table
• lighter in colour - white to bluish hue
• pulp chambers are large, horns are high
• thinner dentin and enamel

Question 3

Why are primary teeth important?

Answer 3

They hold the eruption space for the permanent teeth. Spaces that develop between them are called primate spaces.
Spaces between primary canines and first molars and also those between the 1st and 2nd molar are called the leeway spaces. This allows an extra margin of space for the permanent canine and premolars to erupt

Question 4

What is resorption?`

Answer 4

When the permanent tooth resorbs the roots of primary teeth. Primary teeth molars are so flared so there is space for the permanent tooth to come into place

Question 5

If primary molars are lost prematurely, how can we keep other primary or permanent molars from mesially drifting into the space?

Answer 5

Space maintainers

Question 6

Why are primary teeth so susceptible to decay?

Answer 6

Because the enamel and dentin is thinner in primary teeth, so the decay can travel quicker through the enamel to the pulp, can cause in early loss of the tooth

Question 7

Primary maxillary central incisor

Answer 7

• short and stubby - is wider mesiodistally than incisocervically. This is the only tooth in either dentition with these dimensions
• have no mamelons
• wider mesiodistally than labiolingually
• single rooted, single canal
• roots are twice as long as the crown and taper at the apex

Question 8

Primary maxillary lateral incisors

Answer 8

• crown is similar to central incisors, but much smaller in all dimensions
• cervicoincisal length is greater than the mesiodistal width
• incisal angles are more rounded than on the central incisor
• root is longer in proportion to its crown and its apex is shaper than the central

Question 9

Primary mandibular central incisors

Answer 9

• crown of the primary mandibular central incisors resembles the lateral more than it does in the permanent
• extremely symmetrical
• smaller than the lateral mesiodistally
• not as constricted at the CEJ
• lingual surface is smooth and tapers toward the prominent cingulum
• root may be 2-3 times longer than the height of the crown

Question 10

Primary mandibular lateral incisors

Answer 10

• incisal edge slopes distally
• distoincisal angle is more rounded
• root many have a more distal curvature in its apical third
• cingulum is more pronounced

Question 11

Primary mandibular canines

Answer 11

• roots of canines are 2 x the crown length
• canine root is slightly shorter and more tapered than maxillary canine root
• much smaller than in the permanent dentition

Question 12

Primary maxillary canines

Answer 12

• sharp cusp
• root about 2 x as long as the crown and is more slender in appearance than the mandibular canine’s root
• lingually, the mesial, distal, incisal and cingulum ridges are more pronounced
• lingual ridge divides the lingual surface into mesiolingual and distolingual fossa
• canine is much wider than the incisors at the cervical third
• tip of the cusp may be slightly distal to the centre of the tooth

Question 13

Primary mandibular canines

Answer 13

• resembles the primary maxillary canine
• distal cusp slope is longer than the mesial cusp slope
• lingual surface of the primary mandibular canine is marked by shallow lingual fossa

Question 14

Primary maxillary molars

Answer 14

• 3 roots, which are thinner and have greater flare than those of the permanent maxillary molars
• small tubercle can be present on the mesiolingual cusp but is not called a cusp of Carabelli because it is too small (called a tubercle of Carabelli)

Question 15

Primary maxillary first molars

Answer 15

• crown does not resemble any other crown in either dentition - blend of a premolar and a molar
• cervical line is not straight, more of a wave
• mesiolingual is the longest and sharpest, distobuccal root is the longest
• crown appears triangular
• may have 3 or 4 cusps
• 3 cusps - forms only a central grove and a mesial pit, oblique ridges unite the DB and ML cusps
• 3 roots (2 buccal and 1 lingual) that are long, slender and flared
• furcation starts apical to the cervix

Question 16

Primary maxillary second molars

Answer 16

• 2nd molar is larger than 1st in both crown and root formation
• tooth most closely resembles the form of the permanent maxillary 1st molar but is smaller in all dimensions
• 2 equal size buccal cusps
• mesiolingual and distolingual cusp and tubercle of Carabelli
• DL cusp is still small in comparison to the three other cusps
• tubercle of Carabelli is small and is located on the ML cusp separated by a groove
• lingual groove is present separating the ML and DL cusps
• occlusal resembles a permanent first molar
• 3 roots - 2 buccal and 1 lingual
• distobuccal root is the shortest

Question 17

Primary mandibular molar

Answer 17

• crown is unlike any other tooth in either dentition
• 4 cusps, mesial is larger
• 2 flared roots (m and d), mesial may curve distally at apical 3rd
• mesiobuccal marginal ridge is pronounced, mesial marginal ridge is well developed
• narrow occlusal surface
• distal root is shorter and has 1 root canal
• mesial has 2 root canals

Question 18

Primary mandibular second molar

Answer 18

• larger than the first molar
• 5 cusps
• most closely resembles the form of the permanent mandibular first molar but is smaller
• 3 buccal cusps, nearly equal in size
• oval occlusal shape
• bifurcation starts at the cervix
• short lingual groove that separates the ML and DL cusps
• lingual not as wide as the 3 buccal cusps
• all cusps are approx. equal in length
• Y shaped pattern on occlusal table
• large central groove and supplemental grooves
• mesial marginal ridge more pronounced than the distal marginal ridge
• 2 roots that are 2 x as long as the crown
• mesial root has 2 canals and distal root has 1