Anatomy - Obj 6.1 - 6. - Week 3 PP

Question 1

Anterior Permanent Dentition

Answer 1

• There are 12 anterior teeth in the permanent
  dentition, six in each dental arch
• The permanent anterior teeth include the central
  incisors, lateral incisors, and canines
• The central incisors are closest to the midline, the
  lateral incisors are the second teeth from the
  midline, and the canines are the third teeth from
  the midline
• All anterior teeth are succedaneous, replacing
  primary teeth of the same type

Question 2

Characteristics of Permanent Anterior Teeth

Answer 2

• All anterior teeth have a cingulum, a rounded,
  raised area on the cervical third of the lingual
  surface
• The lingual surface on anterior teeth has rounded,
  raised borders on the mesial and distal surfaces
  called marginal ridges
• Some anterior teeth have a fossa, which is a wide,
  shallow depression on the lingual surfaces (Bird &
  Robinson, 2021)

Question 3

Permanent Incisors

Answer 3

• There are eight permanent incisors
  ◦ Four maxillary
  ◦ Four mandibular
• The maxillary group comprises two central incisors
  and two lateral incisors, as does the mandibular
  group
• These teeth complement each other in form and
  function
• The central incisors erupt about a year or so
  before the lateral incisors do

Question 4

Maxillary Central Incisors

Answer 4

Maxillary central incisors (1.1 and 2.1) have unique
anatomical features
* Larger in all dimensions, especially mesiodistally, than
a permanent mandibular central incisor
* Root is short compared with the roots of other
permanent maxillary teeth
* All lingual surface features, including the marginal
ridges, lingual fossa, and cingulum, are more
prominent on the maxillary central incisor than on the
mandibular central incisor
The incisal edge is also known as the incisal surface or incisal plane
* When newly erupted, the central and lateral
incisors have three mamelons, or rounded enamel
extensions on the incisal ridge, or edge
* The mamelons usually undergo attrition shortly
after eruption

Question 5

Maxillary Lateral Incisors

Answer 5

The maxillary lateral incisors (1.2 and 2.2) are
smaller than the central incisors in all dimensions except root length
* They usually erupt after the maxillary central
incisors
* The crown of a maxillary lateral incisor has a single
root that is relatively smooth and straight but may
curve slightly distally
* Recognizing this feature is helpful in the mounting
of radiographs
The lateral incisors vary in form more than any
other tooth in the mouth, except the third molars,
and are often congenitally missing
* Because of the variations in form, the permanent
maxillary lateral incisors present challenges during
preventive, restorative, and orthodontic procedures
* Open contacts (spaces between teeth), called
diastema, often occur in this area because of the
variations in tooth size and position in the arch

Question 6

Pegged Maxillary Lateral Incisor

Answer 6

“stump tooth”

Question 7

Mandibular Incisors

Answer 7

• The permanent mandibular incisors are the
  smallest teeth of the permanent dentition and the
  most symmetric
• The central and lateral incisors of the mandibular
  arch resemble each other
• Generally, the lateral incisor is larger than the
  central incisor, in contrast to the teeth in the maxillary arch
• Supragingival tooth deposits, such as plaque, calculus, and stain, tend to collect in the lingual concavity of the mandibular incisors

Question 8

Mandibular Central Incisors

Answer 8

The mandibular central incisors (3.1 and 4.1) are
the smallest and simplest teeth and are bilaterally
symmetric
* Each has a small centered cingulum, subtle lingual
fossa, and equally subtle marginal ridges
* The crown of a mandibular central incisor is
narrower on the lingual surface than on the labial
surface
* Developmental horizontal lines on anterior teeth,
or imbrication lines, and developmental
depressions usually not present or very faint

Question 9

Mandibular Lateral Incisors

Answer 9

The mandibular lateral incisors (3.2 and 4.2) are
slightly larger than the mandibular central incisors
but otherwise similar to them
* The lateral teeth usually erupt after the mandibular central incisors
* The lateral incisors have a small, distally placed
cingulum
* Greater height of the cementoenamel junction
(CEJ) curvature on the mesial surface than on the
distal surface helps distinguish the right
mandibular lateral incisor from the left incisor

Question 10

Permanent Canines

Answer 10

• The permanent canines are the four anterior teeth
  located at the corner of each quadrant for each
  dental arch
  The permanent canines are the longest teeth in
  the dentition
• The root is usually the length of the crown
• This large root is externally manifested by the
  bony vertical ridge called the canine eminence
  (Bird & Robinson, 2021)

Question 11

Maxillary Canines

Answer 11

The maxillary canines (1.3 and 2.3) usually erupt
after the mandibular canines, after the maxillary
incisors, and possibly after the maxillary premolars
* The cusp tip is sharper on a maxillary canine
* The mesial cusp slope is usually shorter than the
distal cusp slope in both the maxillary and the
mandibular canines when they first erupt
* The length of these cusp slopes, and the cusp tip
can change with attrition

Question 12

Mandibular Canines

Answer 12

The mandibular canines (3.3 and 4.3) usually erupt
before the maxillary canines and after most of the
incisors have erupted
* A mandibular canine closely resembles a maxillary
canine
* Although the entire tooth is usually as long, a
mandibular canine is narrower labiolingually and
mesiodistally than a maxillary canine
* The lingual surface of the crown of the mandibular
canines is smoother than that of the maxillary canines
and has a less developed cingulum and two marginal
ridges

Question 13

Clinical Considerations with Canine s

Answer 13

The maxillary canines may erupt labially or
lingually in relation to the surrounding teeth
* The maxillary canines may also fail to erupt fully
and may remain impacted
* This occurs because the permanent maxillary
canines erupt after the maxillary incisors and
possibly after the premolars and their arch spaces
have closed

Question 14

Posterior Permanent Dentition

Answer 14

The permanent posterior teeth include the
premolars and molars
* The crown of each posterior tooth has an occlusal
surface, bordered distally and mesially by marginal
ridges
* The occlusal surfaces have two or more cusps
* Imagine each cusp as a mountain with sloping
areas, or cusp ridges, extending from the top of
the mountain; between the ridges are sloping
areas called inclined cuspal planes
Each shallow, wide depression on the occlusal
table is a fossa
* One type of fossa on posterior teeth, the central
fossa, is located where the cusp ridges converge in
a central point, where the grooves meet
* Another type of fossa is the triangular fossa
* Sometimes located in the deepest portions of the
fossa are occlusal developmental pits
◦ Each pit is a sharp pinpoint depression where two or
more grooves meet

Question 15

Permanent PreMolars

Answer 15

• There are eight premolars in the permanent
  dentition, two in each quadrant
• They are located posterior to the canines and
  immediately anterior to the molars
• There are two types of premolars
  ◦ First
  ◦ Second

Question 16

Maxillary First Premolars

Answer 16

A maxillary first premolar (1.4 and 2.4) is larger
than a maxillary second premolar
* Each maxillary first premolar has two cusps
(buccal and lingual) and two roots (facial and
lingual)
* Both maxillary premolars erupt earlier than the
mandibular premolars
The maxillary first premolar has a bifurcated root
(two roots: one buccal and one lingual)
* Some first premolars have roots that are joined, or
fused
* The roots are shorter in length and resemble the
roots of the molars

Question 17

Maxillary Second Pre-Molars

Answer 17

• Each maxillary second premolar (1.5 and 2.5) has
  two cusps (buccal and lingual) and one root

Question 18

Differences between Second and First Maxillary Premolars

Answer 18

• The cusps are closer in length on the second premolar
• The lingual cusp is slightly shorter, but not as short as
  the cusp on the maxillary first premolar
• The mesiobuccal cusp slope is shorter than the
  distobuccal cusp slope on the second premolar
• The cusps of the secondary premolar are not as sharp as
  those of the maxillary first premolar
• The second premolar has only one root and one root
  canal
• The second premolar is wider buccolingually than
  mesiodistally

Question 19

Mandibular First Premolars

Answer 19

Each mandibular first premolar (3.4 and 4.4) has a
long and well-formed buccal cusp and a small,
nonfunctioning lingual cusp
* The lingual cusp may be no larger than the
cingulum on some maxillary canines
* The mandibular first premolars are smaller and
shorter than the mandibular second premolars

Question 20

Mandibular Second Premolars

Answer 20

• The permanent mandibular second premolars (3.5
  and 4.5) erupt distal to the mandibular first
  premolars
• They are the succedaneous replacements for the
  primary mandibular second molars
• There are two forms of the mandibular second
  premolar
  ◦ Three-cusp type, or tricuspidate form
  ◦ Two-cusp type, or bicuspidate form (Bird & Robinson,
  2021)

Question 21

Mandibular Second Premolar Groove Types

Answer 21

“U” Type
“H” Type
“Y” Type

Question 22

Clinical Considerations with PreMolars

Answer 22

The maxillary and mandibular premolars work
with the molars in the chewing of food
* The first premolars help the canines in shearing or
cutting bits of food
* The premolars also support the corners of the
mouth and cheeks

Question 23

Permanent Molars

Answer 23

There are 12 molars, three in each quadrant, in
the permanent dentition
* The molar crowns have four or five short, blunt
cusps, and each molar has two or three roots that
help support the larger crown

There are three types of molars: First, second, and
third
* The first and second molars are also called the 6-
year and 12-year molars because of the
approximate ages at which they erupt

Question 24

Maxillary Molars

Answer 24

• Usually, the first permanent teeth to erupt into
  the maxillary arch
• Each maxillary molar usually has four major cusps,
  with two on the buccal portion of the occlusal
  table and two on the lingual
• Each maxillary molar has three well-separated and
  well-developed roots
• A tooth with three roots is said to be trifurcated,
  which means “divided into thirds”

Question 25

Maxillary First Molars

Answer 25

The maxillary first molars (1.6 and 2.6) are the first
permanent teeth to erupt into the maxillary arch
* They erupt distal to the primary maxillary second
molars and are therefore nonsuccedaneous (do not
replace the primary teeth)
* The maxillary first molar is the largest tooth in the
maxillary arch and also has the largest crown in the
permanent dentition
* This molar is composed of five developmental lobes,
two buccal and three lingual
* The fifth cusp is called the cusp of Carabelli

Question 26

Maxillary Second Molars

Answer 26

• The crown of the maxillary second molar (1.7 and
  2.7) is somewhat shorter than that of the first
  molar, and it usually has four cusps
• No fifth cusp is present
• There are three roots
• The roots of the secondary molars are smaller
  than those of the first molars
  ◦ The lingual root is still the largest and longest

Question 27

Maxillary Third Molars

Answer 27

The maxillary third molars (1.8 and 2.8) differ
considerably in size and contour
* The crown of the maxillary third molar is smaller
and the roots are usually shorter
* The roots of the maxillary third molar tend to fuse,
and the result is a single tapered root
* People sometimes refer to the maxillary third
molars as the “wisdom” teeth because they erupt
last

Question 28

Clinical Considerations with Maxillary Molars

Answer 28

The roots of the maxillary molars may penetrate
the maxillary sinus as a result of accidental trauma
or during an extraction
* The permanent maxillary third molars may fail to
erupt and may remain impacted within the
alveolar bone
* If the maxillary first molar is lost, the second molar
can tip and drift into the open space, causing
difficulty in chewing and furthering periodontal
disease

Question 29

Mandibular Molars

Answer 29

• The mandibular molars erupt 6 months to 1 year
  before the corresponding permanent maxillary
  molars
• The crowns of the mandibular molars have four or
  five major cusps, with two lingual cusps always of
  about the same width
• All mandibular molars are wider mesiodistally
  than buccolingually, similar to anterior teeth
  Each mandibular molar has two well-developed roots, one mesial and one distal
• A tooth with two roots is referred to as bifurcated,
  which means “divided into two”
• A bifurcation is the area at which the two roots
  divide

Question 30

Mandibular First Molars

Answer 30

The permanent mandibular first molars (3.6 and
4.6) erupt between 6 and 7 years of age
* These teeth are commonly the first permanent
teeth to erupt in the oral cavity
* The two roots, mesial and distal, of a mandibular
first molar are larger and more divergent than
those of a second molar (Bird & Robinson, 2021)
* 5 cusps: MB, DB, D, ML and DL
* Two facial (buccal) developmental grooves which
may end in pits.

Question 31

Mandibular Second Molars

Answer 31

The mandibular second molars (3.7 and 4.7) erupt
between 11 and 12 years of age
* These teeth erupt distal to the permanent first
molars and therefore are nonsuccedaneous
* The crown of the mandibular second molar is
slightly smaller than that of the first molar in all
directions
* The crown has four well-developed cusps

Question 32

Mandibular Third Molars

Answer 32

• The mandibular third molars (3.8 and 4.8) are
  similar to the maxillary third molars in that they
  vary greatly in shape
• There is no typical mandibular third molar
• This molar is usually smaller in all dimensions than
  the second molar
• The third molar consists of four developmental
  lobes
• A mandibular third molar has two roots that are
  fused, irregularly curved, and shorter than those
  of a mandibular second molar

Question 33

Clinical Considerations with Mandibular Molars

Answer 33

The lingual inclination of the crowns of the
mandibular molars can make it difficult to position
the oral evacuator
* The lingual inclination of the molar teeth can also
pose problems in oral hygiene for patients, who
may miss the lingual gingiva with the toothbrush

Question 34

Permanent Eruption Dates

Answer 34

*6-7 Years
Maxillary 1st Molars
Mandibular Central Incisors
Mandibular 1st molars

*7-8 years
Maxillary Central Incisors
Mandibular Lateral Incisors

*8-9 years
Maxillary Lateral Incisors

*9-10 years
Mandibular Cuspids

*10-11 years
Max 1st Premolar
Mandi 1st premolar

*10-12 years
Max 2nd premolar

*11-12 years
Max Cuspids

*11-13 years
mandi 2nd molar
Max 2nd molars

*12-13 years
Mandi 2nd premolars

*17-21 years (if at all)
mandi 3rd molar
Max 3rd molars

Question 35

Occlusion

Answer 35

Relationship between maxillary and mandibular
teeth when upper and lower jaws are fully closed
and relationship between teeth in the same arch

Question 36

Malocclusion

Answer 36

Abnormal or malposition relationships of maxillary teeth to mandibular teeth when they are in centric occlusion

is related to lack of an overall ideal form in the dentition while in CO

Question 37

Centric Occlusion

Answer 37

• Centric occlusion (CO) is the voluntary
  position of the dentition that allows the maximum contact when the teeth occlude

Each tooth of one arch is in occlusion with two others in the
opposing arch, except for the mandibular central incisors and maxillary third molars

Question 38

Centric Relation

Answer 38

Is the end point of closure of the mandible; the mandible is in the most retruded position to which it can be carried by the musculature and ligaments.
* Ideally, when the mandible is in CR, the dentition should be in CO (thus centric relation equals centric occlusion, or CR = CO)
* Independent of tooth contact

Question 39

Curve of Spee

Answer 39

When the maxillary and mandibular teeth come into CO, they align along anteroposterior and lateral curves.
* This is produced by the curved alignment of all the teeth and is especially evident when viewing the posterior teeth from the buccal view

Question 40

Overjet

Answer 40

• When the teeth usually occlude in CO, the
  maxillary arch horizontally overlaps the mandibular arch, which is referred to as overjet.
• Overjet is measured in millimeters with the tip of a periodontal probe, once a patient is in CO.
• The probe is placed at 90°or at a right angle to the labial surface of a mandibular incisor at the base of the incisal
  ridge of a maxillary incisor

Question 41

Overbite

Answer 41

• In CO, the maxillary arch also vertically overlaps the mandibular arch, which is referred to as overbite.
  The amount of vertical overlap, usually
  2 to 5 mm between the anterior sextants of the
  two arches, allows contact between the posterior teeth during mastication.
• It is usually expressed as a percentage at around 20% to 30%

Question 42

Severe overbite

Answer 42

When the maxillary arch and its incisors have a more pronounced overlap with the mandibular arch and its incisors, it causes a severe overbite (or deep overbite).

Question 43

Underbite

Answer 43

When the mandibular arch and its incisors extends beyond the maxillary arch and its incisors, it is causes an underbite

Question 44

Crossbite

Answer 44

Occurs when a mandibular tooth or teeth are placed
facially to the maxillary teeth

Question 45

Openbite

Answer 45

• Teeth do not occlude.

Question 46

End-to-End bite

Answer 46

Teeth occlude without the maxillary teeth
overlapping the mandibular teeth.

Question 47

Malocclusion Classification

Answer 47

• The Angle classification of malocclusion does not describe normal or even ideal occlusion, only malocclusion of the molars and canines.
• The basis of the Angle classification system was the simple hypothesis that the permanent maxillary first molar was the key to occlusion.
• Later, the relationship of the opposite arch canines was also evaluated
• In the Angle classification, most cases of malocclusion are grouped into three main classes, according to the position of the permanent maxillary first molar to the mandibular first molar.
• This classification system is based on the relationship of the teeth and not the skeletal considerations that are due to the disproportionate size or position of the jaws
  Three main classes are designated by Roman numerals (I to III), and they assume that both sides of the dentition are affected equally, unless specifically noted.
• Separate defining classifications can be made, depending on which side is affected

Question 48

Malocclusion: Gnathic Index

Answer 48

Each type of facial profile present (either mesognathic,
retrognathic, or prognathic) can be measured by the
gnathic index
* This measurement gives the degree of prominence of the
maxillae as opposed to the mandible

Question 49

Gnathic Index: Mesognathic

Answer 49

Perpendicular - jaw is in the middle

Question 50

Gnathic Index: Retrognathic

Answer 50

Jaw is inward

Question 51

Gnathic Index: Prognathic

Answer 51

Jaw is outward

Question 52

Class I Malocclusion (Angle Classification)

Answer 52

• All cases in a Class I malocclusion
  (neutroclusion) within a permanent dentition are characterized by an ideal MD relationship of the jaws and dental arches.
• the MB cusp of the maxillary first molar occludes with the MB groove of the mandibular first molar
• Class I malocclusion is due to dental malalignments, such as crowding (patients refer to these as “crooked
  teeth”) or irregular spacing within the jaws

Molar: Mesiobuccal cusp of maxillary 1st molar occluding with MB groove of mandibular 1st molar

Canines: Maxillary occluding with distal half of mandibular canine and mesial half of mandibular first premolar

Dental malalignment present - such as crowding or irregular spacing; mesognathic profile

Question 53

Class II Malocclusion (Angle Classification)

Answer 53

All cases in Class II malocclusion (distoclusion) within the
permanent dentition are characterized by the MB cusp of the maxillary first molar occluding (by more than the width of a premolar) mesial to theMB groove of the mandibular first molar

The major group of Class II malocclusion has
two subgroups, division I and division II,
based on the position of the anterior teeth,
shape of the palate, and resulting facial profile

Molar: MB cusp of maxillary first molar occluding (by more than width of premolar) mesial to MB groove of mandibular first molar

Canines: Distal surface of mandibular canine distal to mesial surface of maxillary canine

Division 1: Maxillary incisor protruding facially from mandibular incisors with severe overbite; retrognathic profile

Division 2: Maxillary central incisors either upright or retruded and maxillary lateral incisors either tipped labially or overlapping central incisors with sever overbite; mesognathic profile

Question 54

Class III Malocclusion (Angle Classification)

Answer 54

In all cases of a Class III malocclusion (mesioclusion) within a permanent dentition, are characterized by the MB cusp of the maxillary first molar occludes (by more than the width of a premolar) distal to the MB groove of the mandibular first molar

Molar: MB cusp of maxillary first occluding (by more than width of premolar) distal to MB groove of mandibular first molar

Canines: Distal surface of mandibular mesial to mesial surface of maxillary (by at least width of premolar)

Mandibular incisors protruding facially from maxillary incisors with underbite and are in complete cross bite; prognathic profile

Question 55

Primary Occlusion

Answer 55

The ideal molar relationship in the primary dentition,
when in CO, is referred to as the terminal plane

Question 56

Flush Terminal Plane

Answer 56

flush terminal plane - in which the primary maxillary and mandibular second molars are in an end-to-end relationship

Question 57

Mesial Step

Answer 57

a mesial step, in which the primary mandibular second molar is mesial to the maxillary second molar

With the presence of a mesial step, an ideal permanent molar relationship usually occurs after the eruption
of the permanent dentition.
* In about 80% of those individuals with mesial step less than 2 mm, Angle Class I molarrelationship will result

Question 58

Distal Step

Answer 58

A distal step relationship, in which
the primary mandibular second molar is distal to the
maxillary second molar, is not an ideal molar relationship in
the primary dentition and thus is not a type of terminal plane relationship