Question 1

Decay progresses quickly in deciduous teeth due to each of the following EXCEPT one. Which one is the EXCEPTION?

Accepted Answer

Enamel is deciduous teeth is not harder than that in permanent teeth. To clarify, if enamel were harder, this would make teeth more resistant to decay.

Question 2

The root of the mandibular canine is slightly shorter and more tapered than its maxillary counterpart. Both roots taper facially and apically.

Accepted Answer

The mandibular root is slightly shorter and more tapered than the maxillary. Both roots taper lingually and apically. Also pertinent, both roots are triangular in cross section and are almost twice as long as their crowns.

Question 3

Each of the following is true of deciduous teeth as compared with permanent teeth EXCEPT one. Which one is the EXCEPTION?

Accepted Answer

The enamel is much thinner, therefore less protective, in primary teeth than in permanent. Deciduous teeth, generally lighter in color, usually appear white with a bluish cast. The dentin, which makes up the body of the tooth, is thinner in deciduous teeth. Pulp horns extend quite high occlusally, placing them much closer to the enamel than the pulp horns in permanent teeth.

Question 4

Which of these deciduous molars are wider mesiodistally than faciolingually?

Accepted Answer

Both first and second mandibular molars are wider mesiodistally than buccolingually. First and second maxillary molars are wider buccolingually than mesiodistally.

Question 5

Primary teeth are whiter than their permanent successors. They are smaller in crown dimension but have roots approximately the same size as the permanent dentition.

Accepted Answer

Deciduous teeth, typically white in color with a bluish cast, are usually lighter in color than the permanent teeth. They are smaller in both crown and root dimension than their permanent counterparts.

Question 6

Which deciduous root has two canals?

Accepted Answer

Both the mandibular first and second molars have two root canals in their mesial root. Their distal root only has one canal. Like the mandibular molars, both maxillary molars have three canals, but the anatomy differs. Maxillary first and second molars have two canals in their buccal root and one canal in the lingual root. Canines and incisor have one root canal.

Question 7

The occlusal table is more narrow buccolingually because the buccal and lingual surfaces of deciduous molars taper occlusally.

Accepted Answer

The degree of tapering in the occlusal direction of the buccal and lingual surfaces of deciduous molars is significantly more than that of permanent molars. This results in a much more narrower occlusal table of the Occlusal surface buccolingually.

Question 8

Which of the following statements accurately describe the deciduous maxillary lateral incisor (select all that apply)?

Accepted Answer

Although the crown of the deciduous maxillary lateral is smaller than that of the central incisor in most dimensions, it closely resembles the central incisor. As compared with the central incisor, the root of the lateral appears much longer than the crown. The incorrect responses accurately describe the permanent maxillary lateral incisors, which show considerable variation in form and are often peg-shaped.

Question 9

Although it is much smaller, the deciduous maxillary second molar resembles its permanent molar successor because the deciduous maxillary second molar has two equal-sized cusps divided by a buccal groove.

Accepted Answer

The successor of the deciduous maxillary second molar is the permanent maxillary premolar! Note that the permanent molars are nonsuccedaneous or accessional. However, the deciduous maxillary second molar does resemble the permanent maxillary first molar primarily because of the equal-sized buccal cusps divided by a buccal groove. Note that the referenced deciduous molar is smaller than the referenced permanent molar.

Question 10

An extra margin of space is available for the eruption of the permanent canine as well as the first and second premolars because the formation of diastemas provides this extra space.

Accepted Answer

As the bone grows, the deciduous teeth develop spaces between them called primate spaces. Leeway spaces, the particular spaces between the deciduous canines and the first molars as well as those between the first and second molars, allow an extra margin of space for the eruption of the permanent canine and the first and second premolars. Diastema is a more broad term referring to any spacing between teeth in the same arch.

Question 11

The root of the mandibular lateral incisor has a mesial and distal longitudinal grove running in a circular fashion. The mandibular central incisor root does not have any grooves or depressions.

Accepted Answer

The root of the mandibular lateral incisor has a mesial longitudinal groove and a mesial depression running lengthwise.

Question 12

The teeth that erupt between 16-22 months of age are the deciduous

Accepted Answer

Primary (deciduous) canines erupt between 16 and 22 months. With the exception of the second molars, which erupt between 21 and 33 months, the canines are the last to erupt. In contrast, the first teeth to erupt are the central incisors between 6 and 12 months.

Question 13

The buccocervical ridges on the deciduous molars are quite pronounced. The second molar shows the most prominence.

Accepted Answer

The most pronounced buccocervical ridge occurs on first molars. These prominences give deciduous crowns a bulbous appearance and accentuate the narrow cervical portion of deciduous roots. Note that the cervical ridge of enamel at the cervical third of anterior crowns is also more prominent in the deciduous dentition.

Question 14

Which deciduous molar has three or four cusps, an oblique ridge, three roots, and often has no distal pit?

Accepted Answer

The maxillary first molar may have three or four cusps and has three roots. If four are present, two are buccal and two are lingual. If three are present, only one is lingual. On the three-cusp form, only a central and a mesial pit (no distal pit) is evident, and an oblique ridge often unites mesiolingual and distofacial cusps.

Question 15

At 3 to 4 years of age, the coronal aspect of the root begins to resorb and continues apically until the tooth is shed. The process of shedding the deciduous dentition and replacement by permanent successors is called exfoliation.

Accepted Answer

Exfoliation begins at 2 to 3 years of age. It is initiated by resorption of the apical end of the root and proceeds coronally until the entire tooth falls out (sheds).

Question 16

Which is the largest root on deciduous maxillary molars?

Accepted Answer

On both the deciduous maxillary first and second molars the lingual root is the largest. The distobuccal is the shortest on both molars. On the second molars, the mesiobuccal may be as long as the lingual.

Question 17

The longer and more slender deciduous roots also flare more than those of the permanent dentition because this arrangement allows room for the developing permanent tooth crowns.

Accepted Answer

The architecture of the deciduous roots enables the crowns of the permanent dentition to develop without being crowded or compressed. Note that a key aspect to this arrangement is the longer, more slender, and tapering deciduous roots.

Question 18

Which deciduous molars have three root canals (select all that apply)?

Accepted Answer

Although there is some variability, all deciduous molars have three root canals. The three roots of the maxillary molars, two buccal and one lingual, each have their own canal. The mandibular molars, each with two roots, also have three root canals. Two canals are in the mesial root and one canal is in the distal root.

Question 19

The deciduous lateral incisors erupt prior to the central incisors. Lateral incisors erupt between 13 and 19 months whereas central incisors erupt between 16 and 22 months.

Accepted Answer

In the deciduous dentition, central incisors erupt slightly prior to lateral incisors. The eruption timelines in the second statement apply to first molars and canines, respectively. Central incisors erupt between 6 and 12 months; laterals erupt between 7 and 13 months.

Question 20

Which of the following statements accurately describe the deciduous maxillary first molar (select all that apply)?

Accepted Answer

The deciduous maxillary first molar does not resemble any other tooth, deciduous or permanent. For this reason it is considered the most atypical of all molars. If four cusps are present, two are buccal and two are lingual. If three cusps are present, only one is lingual.

Quiz 16: Deciduous Dentition