Anatomy - Obj 6.1 - 6. (Week 3 PP) Flashcards
Anterior Permanent Dentition
- 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
Characteristics of Permanent Anterior Teeth
- 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)
Permanent Incisors
- 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
Maxillary Central Incisors
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
Maxillary Lateral Incisors
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
Pegged Maxillary Lateral Incisor
“stump tooth”
Mandibular Incisors
- 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
Mandibular Central Incisors
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
Mandibular Lateral Incisors
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
Permanent Canines
- 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)
Maxillary Canines
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
Mandibular Canines
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
Clinical Considerations with Canine s
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
Posterior Permanent Dentition
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
Permanent PreMolars
- 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
Maxillary First Premolars
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
Maxillary Second Pre-Molars
- Each maxillary second premolar (1.5 and 2.5) has
two cusps (buccal and lingual) and one root
Differences between Second and First Maxillary Premolars
- 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
Mandibular First Premolars
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
Mandibular Second Premolars
- 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)
Mandibular Second Premolar Groove Types
“U” Type
“H” Type
“Y” Type
Clinical Considerations with PreMolars
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
Permanent Molars
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
Maxillary Molars
- 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”
Maxillary First Molars
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
Maxillary Second Molars
- 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
Maxillary Third Molars
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
Clinical Considerations with Maxillary Molars
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
Mandibular Molars
- 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
Mandibular First Molars
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.
Mandibular Second Molars
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
Mandibular Third Molars
- 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
Clinical Considerations with Mandibular Molars
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
Permanent Eruption Dates
*6-7 Years
Mandibular Central Incisors
Maxillary 1st Molars
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
Occlusion
Relationship between maxillary and mandibular
teeth when upper and lower jaws are fully closed
and relationship between teeth in the same arch
Malocclusion
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
Centric Occlusion
- 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
Centric Relation
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
Curve of Spee
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
Overjet
- 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