Question 1

Each of the following is true of the permanent central incisor EXCEPT one.Which one is the EXCEPTION?

Accepted Answer

Root formation of the permanent central incisors is not complete until ten years of age.The remaining selections accurately describe this tooth.While development is usually normal,gemination,an infrequent anomaly,is a process where the tooth shows evidence of attempting to divide itself.Other anomalies include a short root or an unusually long crown.

Question 2

Teeth most likely to be peg-shaped are the mandibular lateral incisors because the distal developmental lobe is large and located more lingually than its mesial lobe.

Accepted Answer

Teeth most likely to be peg-shaped are the maxillary lateral incisors,which vary greatly in form.The reasoning provided in the question accurately describes the mandibular lateral incisors.Note that the lingual location of the large developmental lobe is the reason the mandibular lateral incisors curve distally to fit into the mandibular arch.

Question 3

The maxillary lateral incisor usually has a straight,thick,cylindrically shaped root.The root length of the maxillary lateral incisor is about 1.5 times the length of the crown.

Accepted Answer

It is the root of the maxillary central incisor that usually is straight,thick,and cylindrically shaped.Conversely,the root of the maxillary lateral appears thinner and often curves distally.As a rule the root of the maxillary lateral incisor is about 1.5 times the length of the crown.

Question 4

When incisors first erupt the incisal ridge is smooth.After teeth have been in function for several months,mamelons,which aid in mastication,develop on the incisal ridge.

Accepted Answer

When incisors first erupt,mamelons can be seen on the incisal ridge (later called the incisal edge).Mamelons are rounded portions of the incisal ridge of newly erupted incisors and form the incisal ridge portion of one of the labial primary lobes.Normal use eventually wears down the mamelons into a flat edge.At this point the incisal ridge is more appropriately called the incisal edge.Mamelons have no special function in mastication.

Question 5

The mandibular lateral incisors are wider mesiodistally than the mandibular central incisors because the mesial developmental lobe of the laterals is larger than that of the centrals.

Accepted Answer

The mandibular lateral incisors,nearly identical in form to the mandibular central incisors,are wider mesiodistally and longer gingivoincisally than the central incisors.This distinction occurs because the distal developmental lobe of the mandibular lateral incisors is larger than that of the centrals.

Question 6

Maxillary central incisors usually develop normally.Two anomalies that sometimes occur are a longer root or a shorter crown.

Accepted Answer

While the central incisors usually develop normally,two anomalies that sometimes occur are a shorter root and a longer crown.A third anomaly is germination,where the tooth shows evidence of attempting to divide itself.An additional note,the maxillary central incisors are the largest and most prominent incisors.

Question 7

Mandibular lateral incisors are generally smaller than mandibular central incisors.Mandibular lateral incisors have greater facial curvature than the central incisors.

Accepted Answer

Mandibular lateral incisors are larger,wider,and longer than the mandibular central incisors.They are wider both mesiodistally and longer gingivoincisally.The second statement is true because the endpoints of the mesiofacial line angle are farther apart than those of the distofacial line angle.

Question 8

Extracted mandibular central incisors are the easiest to identify as either right or left because they are located anteriorly and near the midline.

Accepted Answer

Mandibular central incisors are the most difficult to identify as either right or left because they are bilaterally symmetrical and difficult to differentiate.Their anterior location does not assist in right/left identification.An occasionally helpful feature is that the distofacial line angle is more rounded than the mesiofacial.

Question 9

Each mamelon forms the incisal edge of one of the primary labial lobes of the incisors.With wear,the rounded incisal edge becomes flat and is then referred to the incisal ridge.

Accepted Answer

The terms incisal edge and incisal ridge are reversed in the question.Each mamelon initially forms the incisal ridge of one of the three primary labial lobes.However,normal use eventually wears down the rounded ridge into a flat edge.At this point the term incisal edge is more appropriate than ridge.

Question 10

Which anatomical landmark could make an incisor more prone to dental caries?

Accepted Answer

Of the four selections,only the lingual pit is concave in nature;the remaining selections are primarily convex.Concavities provide ideal nurturing locale for plaque biofilms,primary etiologic factors of dental caries.

Question 11

The mandibular central incisor occludes with both the maxillary central incisor and the maxillary lateral incisor.Similar to other anterior teeth,a mandibular incisor is derived from five lobes,three facial lobes and two lingual lobes.

Accepted Answer

The mandibular central incisor,the smallest tooth in the mouth,occludes with only one opposing tooth,a maxillary central incisor.All anterior teeth are derived from four lobes,three facial and one lingual.Also pertinent,mandibular central incisors are the most difficult to identify as either right or left because they are bilaterally symmetrical.

Question 12

All incisors have two marginal ridges,a cingulum,and a lingual fossa.The mandibular central incisor has the least distinct lingual anatomy.

Accepted Answer

Marginal ridges,a cingulum,and a lingual fossa are standard anatomic features of incisors.The cingulum is a smooth convexity on the lingual surface immediately below the cervical line.The lingual fossa is mesially and distally confluent with the cingulum.Marginal ridges are rounded convexities that border the lingual fossa.Of the four incisors,the mandibular central has the least distinct anatomy as evidenced by a shallow surface with no prominent features.

Question 13

Which of the following are characteristic of one or both maxillary incisors (Select all that apply. )?

Accepted Answer

Linguoincisal attrition is characteristic of maxillary incisors because this surface contacts the mandibular teeth during normal function.The maxillary central incisors are the most prominent teeth in the mouth.Roots of mandibular incisors are thinner than those of the maxillary incisors.The contours of the mandibular teeth are such that the labiolingual crown dimension is wider than is the mesiodistal.

Question 14

The eruption time for both the maxillary central incisor and mandibular lateral incisor is

Accepted Answer

Both maxillary central and mandibular lateral incisors erupt at approximately 7 to 8 years of age.Maxillary lateral incisors erupt at approximately 8 to 9 years of age.Mandibular central incisors erupt at approximately 6 to 7 years of age.

Question 15

Which of the following are commonly found on roots of maxillary incisors?

Accepted Answer

Neither maxillary central nor lateral incisor roots show evidence of division,bifurcation,indentation,or proximal grooves.

Question 16

Each of the following statements correctly describes maxillary lateral incisors EXCEPT one.Which one is the EXCEPTION?

Accepted Answer

Maxillary lateral incisors vary in form more than any other teeth in the mouth except the third molars.If the variation is too great,it is considered a developmental anomaly.By contrast,the maxillary central incisors are much more likely to develop normally.The incisal aspect of the maxillary lateral incisors sometimes resembles that of the central incisors or a small canine because of developmental variation.

Question 17

Which incisor has a lingual pit?

Accepted Answer

The lingual anatomic features of the maxillary lateral incisor are similar to those of the central incisors but are more highly developed and have more prominent marginal ridges and deeper lingual fossae.More than any other incisor,laterals are more likely to have a lingual pit.Interestingly,the cingulum may be smaller or even almost absent.

Question 18

In an anterior crossbite,the maxillary central incisors would exhibit wear in which location?

Accepted Answer

In anterior crossbite,the smooth enamel of the slightly convex labial surface of maxillary central incisors would exhibit wear.While technically such wear would appear at the incisal edge of the labial surface,with extensive occlusal disharmony evidence of wear can involve more of the labial surface than the labioincisal edge.

Question 19

Which incisor is not derived from four primary lobes?

Accepted Answer

All incisor teeth are derived from four primary lobes,three facial and one lingual.Developmental lines on the labial aspect divide the surface into three parts,each developmental line separating a primary lobe.

Question 20

Which of the following are characteristic of one or both mandibular incisors (Select all that apply. )?

Accepted Answer

Mesial and distal contact areas for both the central and lateral incisors are located at the incisal third.Lingual surfaces of mandibular central incisors are smooth and shallow with no prominent features.Lingual surfaces of mandibular lateral incisors have slightly more definition.By contrast,lingual surfaces of maxillary incisors have much more pronounced anatomy.Slender roots are associated with mandibular incisors.

Quiz 12: Incisors