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Dental Anatomy
and Occlusion 2009-2010
RESD 5004 (lecture portion) and 5005 (laboratory portion)
Course Director:
Edward Wright, D.D.S., M.S. (ext. 7-3697)
[email protected]
Restorative Dentistry Faculty, Room# 3.592U
This material falls under the copyright laws and can only be
reproduced within these
restrictions.
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Table of Contents Page
Course Syllabus, RESD 5004 (Lecture Portion)
........................................................... 7
Course Syllabus, RESD 5005 (Laboratory Portion)
..................................................... 13
Introduction
...................................................................................................................
20
Chapter 1. Human Dentition I
......................................................................................
21
A. Tooth Numbering Systems
.................................................................................
31
1. Universal Numbering System
........................................................................
31
B. Terms of Orientation
..........................................................................................
33
1. Tooth Surfaces
...............................................................................................
34
2. Combining Terms of Tooth Surfaces To Describe Angles
............................ 36
3. Division of Tooth Surfaces
............................................................................
41
Chapter 2. Human Dentition II
.....................................................................................
42
A. Crown Elevations
...............................................................................................
48
B. Crown Depressions
............................................................................................
53
C. Embrasures
.........................................................................................................
55
D. Proximal Contacts
..............................................................................................
58
Chapter 3. Anterior Teeth
.............................................................................................
60
A. Overview
............................................................................................................
60
1. Lobes
..............................................................................................................
60
2. Tooth Outlines
...............................................................................................
62
B. Incisor
.................................................................................................................
63
1. Line Angles
....................................................................................................
63
2. Proximal Contacts
..........................................................................................
70
3. Embrasures
.....................................................................................................
71
4. Contours
.........................................................................................................
74
C. Summary Maxillary Anterior Teeth
...................................................................
76
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1. Maxillary Central Incisors
.............................................................................
76
2. Maxillary Lateral Incisors
..............................................................................
79
3. Maxillary Canines
..........................................................................................
82
D. Review Maxillary Anterior Teeth
......................................................................
85
E. Summary Mandibular Anterior Teeth
................................................................
88
1. Mandibular Central and Lateral Incisors
....................................................... 88
2. Mandibular Canines
.......................................................................................
91
F. Review Mandibular Anterior Teeth
....................................................................
94
Chapter 4. Introduction to Your Articulator
.................................................................
97
Chapter 5. Occlusal Contact Relationships and Basic Mandibular
Movements .......... 107
A. Static Occlusal Relationships
.............................................................................
108
1. Cusp-to-Marginal Ridge and Cusp-to-Fossa Occlusion
................................ 109
2. Cusp-to-Fossa Occlusion
...............................................................................
111
B. Mandibular Movements
.....................................................................................
112
Chapter 6. Posterior Teeth
............................................................................................
115
A. Lobes and Associated Structures
.......................................................................
115
B. Angulations of Teeth
.........................................................................................
118
C. Occlusal Table
....................................................................................................
121
D. Vertical Line Angles
..........................................................................................
122
E. Marginal Ridges
.................................................................................................
124
F. Summary of Premolars
.......................................................................................
125
1. Maxillary First Premolar
................................................................................
125
2. Maxillary Second Premolar
...........................................................................
128
3. Mandibular First Premolar
.............................................................................
131
4. Mandibular Second Premolar
........................................................................
134
G. Review of Premolars
..........................................................................................
138
H. Summary of Molars
...........................................................................................
142
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1. Maxillary First Molar
.....................................................................................
142
2. Maxillary Second Molar
................................................................................
145
3. Mandibular First Molar
..................................................................................
148
4. Mandibular Second Molar
.............................................................................
150
I. Review of Molars
................................................................................................
153
Chapter 7 Primary Dentition
.......................................................................................
158
A. Formation and Calcification of the Primary Teeth
............................................ 158
B. Number of Teeth
................................................................................................
158
C. Designation of the Primary Dentition
................................................................
159
D. Comparison of Primary and Permanent Teeth
................................................... 159
E. Morphology of Individual Primary Teeth
.......................................................... 161
F. Norms of Primary Dentition Occlusion
..............................................................
165
G. Drawings of Primary Teeth
................................................................................
166
Chapter 8 Pulp Chambers and Canals
.........................................................................
169
A. Pulp Chambers
...................................................................................................
169
B. Root Canal System
.............................................................................................
170
C. Specific Teeth
.....................................................................................................
171
Chapter 9 Articulators
.................................................................................................
174
A. Non-adjustable Articulator
................................................................................
174
B. Semi-adjustable Articulators
.............................................................................
176
C. Fully-adjustable Articulator
...............................................................................
180
D. Summary of Articulators
....................................................................................
184
Chapter 10. Mandibular Positions and Movements
..................................................... 185
A. Mandibular Positions
.........................................................................................
185
1. Rest Position
..................................................................................................
185
2. Maximum Intercuspation (MI)
......................................................................
187
3. Centric Relation (CR)
....................................................................................
187
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B. Mandibular Border and Functional Movements
................................................ 188
1. Sagittal Plane
.................................................................................................
189
2. Frontal Plane
..................................................................................................
192
3. Horizontal Plane
...........................................................................................
196
Chapter 11. Dynamic Occlusal Relationships
..............................................................
201
A. Horizontal Plane
................................................................................................
202
B. Frontal Plane
......................................................................................................
206
C. Sagittal Plane
......................................................................................................
211
Chapter 12. Principles of Anterior Guidance of Occlusion
......................................... 212
Chapter 13. The Temporomandibular Joint
.................................................................
215
Chapter 14. Masticatory Muscles
.................................................................................
220
Appendix:
Dental Anatomy Waxing Instruments
...........................................................................
227
Drip Wax Block Exercise
.............................................................................................
230
Disinfect Extracted Teeth
..............................................................................................
232
Self Test 1
.....................................................................................................................
234
Self Test 2
.....................................................................................................................
235
Progressive Wax Block Exercise
..................................................................................
236
Self Test 3
.....................................................................................................................
238
Cast Landmark Exercise
...............................................................................................
240
#10 Mesial Half Exercise
..............................................................................................
242
#8 Full Crown Exercise
.................................................................................................
244
#8 Class 4 and 5 Composite Exercises
..........................................................................
245
#8 Full Crown Practical Exam
......................................................................................
247
Comparing Occlusal Contacts Exercise
........................................................................
248
#8 Maximum Intercuspation Exercise
..........................................................................
250
#6 Maximum Intercuspation Exercise
..........................................................................
251
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#4 Full Crown Exercise
.................................................................................................
252
#4 Maximum Intercuspation Exercise
..........................................................................
254
Identify Extracted Teeth
................................................................................................
255
#29 Maximum Intercuspation Exercise
........................................................................
256
#4 Full Crown Practical Exam
......................................................................................
257
#3 Full Crown Exercise
.................................................................................................
259
#3 Maximum Intercuspation Exercise
..........................................................................
261
#3 Full Crown Practical Exam
......................................................................................
262
#30 Full Crown Exercise
...............................................................................................
264
#30 Full Crown Practical Exam
....................................................................................
266
#30 Canine Guidance Exercise
.....................................................................................
268
Analysis of Mandibular Movements Exercise
..............................................................
270
Articulator Exercise
......................................................................................................
282
#30 Canine Guidance Practical Exam
...........................................................................
285
#6-11 Anterior Guidance Exercise
................................................................................
287
#11-14 Group Function Exercise
..................................................................................
290
Evaluating the Masticatory System
...............................................................................
293
Masticatory and Cervical Palpations
.............................................................................
294
#11-14 Group Function Practical Exam
........................................................................
296
Dental Anatomy Quick Reference
................................................................................
299
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Course Syllabus, RESD 5004 (Lecture Portion)
List of Topics Disinfecting Extracted Teeth
Human Dentition I & II
Anterior Teeth I, II, III
Restoring Contours with Composite
Introduction to Your Articulator
Occlusal Contacts and Basic Mandibular Movements
Posterior Teeth I & II
Tooth Identification
Primary Dentition
Pulp Chambers and Canals
Articulators
Mandibular Positions and Movements
Dynamic Occlusal Relationships
Your Articulator
Anterior Guidance of Occlusion
The Temporomandibular Joint
The Masticatory Muscles
Evaluating the Masticatory System
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Chapter 1. Human Dentition I
As the mouth or oral cavity is viewed from the front, it must be
noted that the right
side of the mouth is to the viewer's left and the left side of
the mouth to the viewer's right.
The teeth are in two arches - an upper and a lower. The upper
arch, or maxillary
arch, of teeth is set in the upper, immobile jaw (Figure 1-1).
The lower arch, or
mandibular arch, of teeth is set in the dynamic or movable
member of the jaws, the
mandible (Figure 1-2). Later as the individual teeth are
discussed, maxillary and
mandibular teeth will be described as moving across each other;
however, it must always
be remembered that only the mandibular arch is the movable
member.
Figure 1-1 Maxilla (left side) Figure 1-2 Mandible (left
side)
There are three planes of orientation utilized in anatomical
descriptions of the
skull. These are the frontal plane (parallel to the face),
horizontal plane (parallel to the
floor), and sagittal plane (parallel to the sides of the head),
Figure 1-3.
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Figure 1-3 Planes of orientation
Each arch is divided in half, as is the remainder of the head,
at the mid-sagittal
plane (midline). Each half arch is termed a quadrant. There are,
therefore, two quadrants
per arch and a total of four quadrants.
There are 16 permanent teeth in each arch. There are eight
permanent teeth in each
quadrant or half arch. Therefore, there are 32 teeth in the
permanent dentition or in a
complete set of permanent teeth.
Humans also have another set of teeth called the primary
dentition, or deciduous
teeth (baby teeth). Each of these two sets have characteristics
that are unique to each set
(primary or permanent) of teeth. Set traits are used to
distinguish between the two
dentitions. These will be discussed later.
Throughout the mouth, the teeth vary in size and shape,
providing differing
functions. The various teeth may be separated by characteristics
termed class traits. The
four classes of teeth are:
1. Incisors - These are eight teeth whose crowns are designed
for cutting or incising
(Figure 1-4). Their "biting" edges are termed incisal edges.
These are the first two
teeth closest to the midline in each quadrant, and are named the
Central Incisor
(first) and Lateral Incisor (second). Therefore, there are two
incisors in each
quadrant (a central and a lateral incisor); four incisors in
each arch (two central
incisors and two lateral incisors); and eight incisors in each
set.
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2. Canines (Cuspids) - These are four teeth with long pointed
crowns designed for
piercing, tearing or holding food (Figure 1-5); they also have
incisal edges. They
are the third teeth from the midline in each quadrant. There is,
therefore, one
canine in each quadrant; two canines in each arch; and four
canines in each set.
Figure 1-4 Figure 1-5
Maxillary and mandibular incisors Maxillary and mandibular
canines
3. Premolars (Bicuspids, older terminology) - These eight teeth
are holding and
grinding teeth (Figure 1-6). The premolars make the transition
from the thinner,
sharper incisors and pointed canines, to the large grinding
surfaces of the molars,
which are the largest teeth in the "back" of the mouth. The
premolars are the
fourth and fifth teeth from the midline in each quadrant and are
termed the first
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premolar and second premolar, respectively. Therefore, there are
two premolars in
each quadrant, four premolars in each arch, and eight premolars
in each set.
4. Molars - These are the 12 large grinding teeth (Figure 1-7).
They are the 6th, 7th
and 8th teeth from the midline in each quadrant. Named from
"front" to "back",
(anterior to posterior), they are the first molar (or 6 year
molar), second molar (or
12 year molar), and the third molar (or "wisdom" tooth).
Figure 1-6 Figure 1.7
Maxillary and mandibular premolars Maxillary and mandibular
molars
NOMENCLATURE:
When naming a specific tooth, the dentition or set is identified
first, then the arch,
quadrant, and specific tooth name are identified - IN THAT
ORDER, i.e., permanent
(set), maxillary (arch), right (quadrant), second premolar
(tooth).
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The primary or deciduous set of teeth will not be covered at
this time. In this course, if
"permanent" is omitted in naming a specific tooth, it should be
understood to be a
permanent tooth, i.e., mandibular left second molar.
A visual tour (Figure 1-8) of the maxillary and mandibular
dental arches from the
midline permits us to observe the various forms of the working
surfaces of the teeth.
Tooth form varies from having simple cutting edges (incisors),
to having single cusps
(canines), to a more complex makeup (premolars), and finally to
the most complex of all
teeth (molars), with their multi-cusp occlusal surfaces.
Figure 1-8 A. Incisors; B. Canines; C. Premolars; and D.
Molars.
INCISORS
As can be seen in Figure 1-9, the incisors have horizontal
cutting blades. The function of
the incisors is to cut the food that is passed into the mouth.
Figure 1-10 demonstrates
how the blades cut into the food, permitting the rest of the
dentition to continue the
process of mastication as the food is transported by the tongue
to the posterior teeth.
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Figure 1-9 Incisors in slight open Figure 1-10 Incising food
and closed positions
CANINES
The canines (or cuspids) have colloquially been called "eye
teeth." Each canine
has two blades which incline towards each other to form the
cusp.
The function of canines in mastication is to pierce, tear, and
rip the food as it is
introduced into the mouth. These teeth are able to handle great
physical stress, since they
are extremely strong and well anchored in the corners of the
arches. The cusp of the
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canine is called a "guiding cusp." According to some concepts of
occlusion, its purpose
is to separate the posterior teeth during chewing.
PREMOLARS
The premolars are characterized by two cone-shaped cusps. The
noted exception is
the mandibular second premolar, which often has a sharp lingual
developmental groove
dividing the lingual cusp. The premolars functions as millers,
mincers, and mullers of
food.
These teeth have cusps on the cheek (buccal) and tongue
(lingual) sides. Based
upon how the teeth occlude with the opposing teeth, the cusps
are classified as either a
supporting cusp (also called centric holding, functional, and
stamp cusp) or a guiding
cusp (also called non-functional and shear cusp). Note that
opposing teeth are in opposite
arches occluding each other, while adjacent teeth are in the
same arch next to each other.
When teeth are in correct alignment and the posterior teeth are
occluding, the
supporting cusp of the posterior teeth (Figure 1-11) is located
between a supporting and
guiding cusp of an opposing tooth. Conversely, the guiding that
is located buccal or
lingual to the occlusal table and forms one side of a fossa.
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Figure 1-11 Supporting and Guiding Cusps
The premolars mull food through the movement of the mandibular
supporting cusp
along the maxillary supporting and guiding cusps of their
opposing teeth, while the
maxillary premolar supporting cusps simultaneously mull the food
in a similar manner.
MOLARS
The molars are large, milling teeth with anatomical differences
that are related to
each molar's specific location within the dental arch. The
maxillary molars consist of: 1)
right and left first molars (six-year molars), each with three
large cuspids, a small cusp
located at the distolingual corner, and a fifth cusp on the
lingual surface of the
mesiolingual cusp (termed cusp of Carabelli); 2) right and left
second molars (twelve-
year molars), each of which follows the same pattern as the
first molar but is smaller and
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does not have the cusp of Carabelli; and 3) right and left third
molars (wisdom teeth),
each of which follows a similar pattern as the second molar but
is smaller (Figure 1-12).
The mandibular molars consists of: 1) right and left first
molars (six-year molars),
each of which is a large five-cusp tooth; 2) right and left
second molars (twelve-year
molars), each of which is usually a four-cusp tooth; and 3)
right and left third molars
(wisdom teeth), each of which is usually also a four-cusp tooth
(Figure 1-12).
Figure 1-12 The maxillary and mandibular molars
The molars have as their specific function the mastication of
food. They
principally accomplish this through the action of the supporting
and guiding cusps. The
sharp ridges and grooves of the guiding cusps are responsible
for the shearing, and the
movement of the supporting cusps in and out of their respective
opposing fossae provides
the milling action. Both the supporting cusps and the guiding
cusps of all the posterior
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teeth, particularly the molars, participate in the final mulling
of the food before the bolus
enters the digestive tract.
If we were to choose which teeth are the most important, we
would select the
canines and first molars. The maxillary and mandibular canines
are firmly buttressed in
the corner of the arches, and the maxillary first molars are
anchored in the zygomatic
processes of the maxilla (Figure 1-13).
Figure 1-13 Locations of the canine and the first molar
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A. Tooth Numbering Systems
A tooth numbering system enables us to rapidly identify the
teeth and speeds our
dental communication. The ability to rapidly associate each
number with the specific
tooth must be developed as soon as possible.
There are three prominent numbering systems, the Universal,
Palmer
(Zsigmondy/Palmer), and International Numbering Systems. The
Universal Numbering
System is the most common system used in the United States. The
Palmer Numbering
System uses brackets around the number to designate in which
quadrant the tooth is
located. Since this is not conducive to typewriters or
computers, it has fallen from favor.
The International Numbering System uses two numbers, one
identifies the tooth as
either primary or permanent and the quadrant in which the tooth
is located, and the other
number designates the tooth's location in the quadrant. This
numbering system has been
adopted by some international organizations, such as the World
Health Organization. So
you may encounter this system if you provide dental care in a
foreign country. Examples
of these numbering systems are provided in the review sections
for the various teeth.
1. Universal Numbering System In 1968 the American Dental
Association recommended the use of the Universal
Numbering System. It designates one letter (A through T) for
each primary tooth and one
number (1 through 32) for each permanent tooth (Figure 1-14).
The Universal
Numbering System will be utilized throughout this course and in
your predoctoral dental
education.
Numbering begins in the maxillary right quadrant with the third
molar being #1
and the second molar #2, the first molar #3, and so forth around
the maxillary arch to the
maxillary left third molar, which is #16. Numbering then drops
to the mandibular left
third molar (#17) and continues from left to right around the
mandibular arch to the
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mandibular right third molar (#32). The tooth need not be
present in the oral cavity to
receive its number. The maxillary right first molar is always #3
- whether present or not.
Figure 1-14 Universal Numbering System
It is good to learn the numbers of certain "key" teeth or groups
of teeth such as the
canines, which are numbered 6, 11, 22, and 27 and the first
molars which are numbered
3, 14, 19, and 30, (Figure 1-15). Then one may count from those
points to number the
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adjacent teeth (teeth next to each other) until sufficient
practice has been accomplished to
have rapid association of each tooth with its specific
number.
Figure 1-15 Key tooth numbers
B. Terms of Orientation
In orienting oneself between front and back, structures toward
the front of the
mouth are anterior, and structures toward the back are
posterior. Anterior teeth are
incisors and canines, while posterior teeth are premolars and
molars (Figure 1-16). The
term medial is used to orient structures toward the middle of
the head and the term lateral
indicates structures or movements away from the mid-sagittal
plane (Figure 1-17).
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Figure 1-16 Anterior and Figure 1-17 Mid-sagittal plane
posterior teeth
1. Tooth Surfaces The crown of the tooth can be thought of as
having five sides or surfaces (Figure 1-
18) and the various surfaces of the teeth have names (Figure
1-19). The surfaces of the
anterior teeth are named as follows:
a. Labial or facial - surface of a tooth toward the lips.
b. Lingual - surface of a tooth toward the tongue. For the
maxillary teeth only, the
term palatal surface is used interchangeably with the term
lingual surface; the
bone and soft tissue forming the "roof of the mouth" is the
palate.
c. Mesial - surface of a tooth toward the midline of the
arch.
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d. Distal - surface of a tooth away from the midline of the
arch.
e. Incisal edge - the biting or incising edge.
The mesial surface of one tooth normally contacts the distal
surface of the tooth
anterior to it. In the case of the central incisors, the mesial
surface of the right central
incisor contacts the mesial surface of the left central incisor
since they meet or contact at
the midline. The place where two adjacent teeth touch is termed
the contact area.
The posterior teeth also have 5 surfaces, named as follows:
a. Buccal or facial - the surface of the tooth toward the cheek
(corresponds to the
labial surface of anterior teeth). Facial may be used when
speaking of the outer
surface of anterior or posterior teeth and is interchangeable
with labial or
buccal.
b. Lingual - surface toward the tongue (same as anterior teeth).
For the maxillary
teeth only, the term palatal surface is also used
interchangeably with the term
lingual surface.
c. Mesial - surface of a tooth toward the midline of the arch
(same as anterior
teeth).
d. Distal - surface of a tooth away from the midline of the arch
(same as anterior
teeth).
e. Occlusal - the biting or chewing surface.
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Figure 1-18 Sides of teeth Figure 1-19 Surface names
Proximal surfaces are surface between two teeth. All proximal
surfaces are mesial
or distal surfaces, but not all mesial and distal surfaces are
proximal surfaces.
2. Combining Terms of Tooth Surfaces To Describe Angles
(Corners) Terms for the tooth surfaces are often combined to
indicate an area which includes
or is formed by two or more surfaces. For example, the
mesiolabial line angle is
understood to be the junction of the mesial and labial surfaces
forming a line and angle.
There are two types of tooth angles: line angles and point
angles. Two surfaces
make up a line angle, while three surfaces make up a point
angle. When the type of angle
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is not specified, the number of surfaces combined indicates the
type of tooth angle, i.e.,
mesiolabio-incisal angle is a point angle.
a. Tooth Line Angles
Line angles are corners or angles formed by the junction of two
surfaces which
form it. There are eight line angles for each tooth (Figures
1-18 and 1-20 to 1-22). The
line angles for the anterior teeth are:
1. Mesiolabial (or labiomesial) - the angle where the mesial and
labial surfaces
join.
2. Distolabial (or labiodistal) - the angle where the distal and
labial surfaces join.
3. Mesiolingual (or linguomesial) - the angle where the mesial
and lingual surfaces
join.
4. Distolingual (or linguodistal) - the angle where the distal
and lingual surfaces
join. (It gets a little obvious by now!!)
5. Labio-incisal (or incisolabial) - the angle where the labial
and incisal surfaces
join.
6. Linguo-incisal (or incisolingual) - the angle where the
lingual and incisal
surfaces join.
7. Mesio-incisal (or incisomesial) - the angle where the mesial
and incisal surfaces
join.
8. Disto-incisal (or incisodistal) - (guess what?) The angle
where the distal and
incisal surfaces join.
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Figure 1-20 Anterior line angles Figure 1-21 Anterior line
angles
The line angles for the posterior teeth are:
1. Mesiobuccal (or buccomesial)
2. Distobuccal (or buccodistal)
3. Mesiolingual (or linguomesial)
4. Distolingual (or linguodistal)
5. Bucco-occlusal (or occlusobuccal)
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6. Linguo-occlusal (or occlusolingual)
7. Disto-occlusal (or occlusodistal)
8. Mesio-occlusal (or occlusomesial)
Figure 1-22 Posterior line angles
NOTE: Some texts list only six line angles for anterior teeth,
because the mesial and
distal incisal angles of anterior teeth are rounded, the
mesio-incisal and disto-incisal line
angles are considered to be non-existent. They are spoken of as
mesial and distal incisal
angles only.
BUT: Eight line angles for each tooth will be utilized in this
course; however, one
should have an understanding of variations in terminology.
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b. Tooth Point Angles
Point angles are corners formed by the junction of three
surfaces. The point angle
takes its name from the surfaces which formed it. There are four
"point angles" for each
tooth (Figures 1-18 and 1-23).
The point angles of the anterior teeth are:
1. Mesiolabio-incisal
2. Distolabio-incisal
3. Mesiolinguo-incisal
4. Distolinguo-incisal
The point angles of the posterior teeth are:
1. Distobucco-occlusal
2. Mesiobucco-occlusal
3. Distolinguo-occlusal
4. Mesiolinguo-occlusal
Note that the order of the surfaces within the word describing
the point angle may
vary; e.g. mesiolabio-incisal may also be mesio-incisolabial,
labiomesio-incisal, labio-
incisomesial, incisolabio-mesial, or incisomesiolabial.
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Figure 1-23 Posterior point angles
3. Division of Tooth Surfaces Tooth surfaces, a portion of a
tooth, or contacts of teeth can be divided into
sections, commonly in thirds. The labial surface is routinely
divided into cervical or
gingival third, middle third, and incisal third (Figure 1-24).
The buccal surface is
similarly divided into cervical or gingival third, middle third
and occlusal third.
Figure 1-24 Division of facial surface with adjacent tooth
contacts marked
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Chapter 2. Human Dentition II
The bone that surrounds the teeth is termed the alveolar bone
(also referred to as
the alveolar process), Figure 2-1. The tooth socket is termed
the alveolus (plural -
alveoli).
Figure 2-1 Alveolar bone or alveolar process
Each tooth is attached to the alveolus (boney socket) by fibers,
which are
collectively termed the periodontal ligament. This fibrous
tissue extends from the walls
of the alveolus to the layer of bone-like tissue called
cementum, which covers the root of
the tooth. The remaining portion of the tooth not covered by
cementum is covered by the
hardest mineralized tissue in the body called enamel. The
portion of tooth covered by
enamel is the anatomical crown (Figure 2-2). The junction of the
enamel and cementum
is the boundary between anatomical crown of the tooth and the
root of the tooth and is
termed the cementoenamel junction (CEJ) or cervical Line. The
CEJ is not a distinct
structure, but merely a distinct location. Cervical lines have
great importance in dentistry
and will be covered later and in other courses.
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30
Figure 2-2 Crown, roots, and supporting tissues
The tissue covering the bone and surrounding the teeth is called
gingiva (gingival
tissue), and patients often refer to it as the gums. The gingiva
may be divided into
attached gingiva and free gingiva. The portion of the gingiva
adjacent to the teeth and
firmly attached to the alveolar bone is termed the attached
gingiva. Gingiva that extends
coronally (toward the crown) from the attached gingiva is the
free gingiva or marginal
gingival. The tissue covering the bone apical to the attached
gingiva is a thin vascular
tissue, not attached firmly to the underlying bone called the
alveolar mucosa (Figure 2-3).
The linear junction of the attached gingiva with the free
gingiva is termed the free
gingival groove. The junction of the attached gingival with the
alveolar mucosa is
termed the mucogingival junction.
The most occlusal or incisal extent of the gingiva on a tooth is
called the gingival
margin. It varies considerably according to many factors such as
age, health of tissue,
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31
tooth location, etc. You will need to understand the difference
between the terms
marginal gingiva (free gingiva) and gingival margin.
Figure 2-3 Free and attached gingiva
There is a very small space or potential space between the free
gingiva and the
tooth. This small space encircling the crown is the gingival
sulcus. It is bounded by the
tooth (usually the enamel of the crown) and the epithelium
covering the free gingiva. The
"bottom" of the gingival sulcus is the most occlusal extent of
the epithelial attachment
(Figure 2-4). This epithelial attachment is a bond around the
tooth where the gingival
epithelium forms a union with the tooth. This attachment is
extremely important and will
be discussed in many succeeding courses.
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32
Figure 2-4 Gingival sulcus and epithelial attachment
Periodontium is a collective term referring to all the tissues
(bone, gingiva, etc.)
that surround and support the teeth. When one views healthy
gingiva (collective term for
the gingival tissues), it should be noted that the gingiva
covers a portion of the anatomical
crown. The portion of the crown visible in the mouth (not
covered by the gingiva) is
termed the clinical crown. It is important to distinguish
between the clinical crown and
the anatomical crown.
The main inner bulk of the tooth is hard tissue termed dentin.
The dentin
surrounds the "nerve" or pulp of the tooth and is covered by
enamel in the anatomical
crown and by cementum in the root. The junction of the enamel
and dentin (inside the
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33
crown of the tooth) is termed the dentinoenamel junction (DEJ).
This would be visible as
a line in cross sections of the anatomical crown. The junction
of the dentin and
cementum (inside the root of the tooth) is termed the
cementodentinal junction, (CDJ),
Figure 2-4.
The soft pulp tissue containing the tooth's vascular as well as
the nerve supply,
occupies an irregular central cavity inside the tooth termed the
pulp cavity. The pulp
cavity can be divided into 3 general portions, 1) the central
portion in the anatomical
crown is termed the pulp chamber, 2) the thin channel(s)
extending from the pulp
chamber down the center of the root(s) is (are) termed the pulp
canal(s), and 3) the small
projections extending occlusally or incisally within the pulp
chamber are termed pulp
horns (Figure 2-5).
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34
Figure 2-5 Pulp cavity
Anatomical areas of the crown are often separated into crown
elevations and crown
depressions. Many surfaces of crowns are described as concave or
convex. Concave
surfaces are depressions. Convex surfaces bulge outward or are
elevated from the surface
(Figure 2-6).
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35
Figure 2-6 Convex and concave surfaces
A. Crown Elevations
a. Cusps - Elevated projections or points on the crowns of
teeth. They are the peaks of
the occlusal surfaces of posterior teeth and the incisal portion
of canine crowns.
Incisors do not possess cusps, while canines normally exhibit
one cusp, premolars
two or three cusps, and molars four or five. The cusp tip is the
most occlusal
termination of the cusp (Figure 2-7).
b. Mamelons - Small, rounded projections of enamel on the
incisal ridges of newly
erupted anterior teeth. They are the incisal terminations of the
three labial lobes.
They are usually worn away soon after eruption (Figure 2-8).
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36
Figure 2-7 Cusps and cusp tips Figure 2-8 Mamelons
c. Tubercles - Small bumps or cusp-like projections found on the
crowns of teeth. They
are variable in size and shape. Tubercles are often thought of
as mini-cusps. They are
not a consistent characteristic of teeth.
d. Lobes - One of the primary anatomical divisions of the tooth
crown, usually
separated by identifiable developmental grooves (discussed under
Crown
Depressions). Lobes are represented by cusps and mamelons and
cingula.
e. Cingulum (Plural: cingula) - The rounded eminence in the
cervical third of the
lingual surface of anterior teeth (Figure 2-9).
f. Marginal ridges - The linear elevations found at the mesial
and distal terminations
of the occlusal surface of posterior teeth. They are also found
on anterior teeth, but
are less prominent, forming the lateral margins of the lingual
surface (Figures 2-10
and 2-11).
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37
Figure 2-9 Cingulum Figure 2-10 Marginal ridges of maxillary
anterior teeth
Figure 2-11 Marginal ridges of posterior teeth
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38
g. Triangular ridges - Linear ridges on posterior teeth, which
run from the cusp tips to
the central area of the occlusal surface. In the mesiodistal
cross-section, they tend to
have a triangular shape (Figure 2-12).
h. Transverse ridge - A combination of two triangular ridges
which cross the occlusal
surface on a posterior tooth, one from the buccal and one from
the lingual. Thus a
transverse ridge is simply a union of two triangular ridges
(Figure 2-12).
i. Oblique ridge - A special type of transverse ridge (composed
of two triangular
ridges), only present on maxillary molars. It crosses the
occlusal surface in an
oblique direction from the distobuccal cusp tip to the
mesiolingual cusp tip (Figure 2-
12).
Figure 2-12 Triangular, transverse, and oblique ridges
j. Cusps ridges - Each cusp has four cusp ridges extending in
different directions
(mesial, distal, facial and lingual) from its tip. They vary in
size, shape and sharpness
(Figure 2-13). The cusp ridge which extends toward the central
portion of the
occlusal surface is a triangular ridge. The cusp ridges are
named by the direction
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39
toward which they extend from the cusp tip. Mesial and distal
cusp ridges are also
termed mesial and distal cusp arms (Figure 2-13). In this
course, the cusp ridge(s) on
the occlusal table will always be referred to as a triangular
ridge. The cusp ridge on
the buccal or lingual surface will be referred to as the buccal
or lingual ridge. The
ridges on the facial and lingual surfaces of the teeth are
rounded and not precise
ridges.
Figure 2-13 Posterior cusp ridges
k. Inclined plane - The sloping area partially bordered by the
crests of two cusp ridges.
Normally, each cusp has four inclined planes, two on the
occlusal table (form the
triangular ridge) and two form the buccal or lingual surfaces of
the cusp. Inclined
planes are named by combining the names of the two cusp ridges
between which they
lie (Figure 2-14).
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40
Figure 2-14 Inclined Planes and Occlusal Table
B. Crown Depressions
a. Fossa (Plural - fossae) - An irregular concavity, on the
surface of a tooth. There is
normally a rather large, shallow fossa on the lingual surface of
an anterior tooth
(Figure 2-10), while each posterior tooth exhibits two or more
fossae of varying size
and shape on the occlusal surface. There are no distinct borders
to locate a fossa.
Fossae are just deeper portions of the occlusal surface,
separated by various ridges
(Figure 2-15). It is important to note that all of the fossae on
the tooth's occlusal
surface are the same depth. This is a very important feature to
remember when you
begin to wax posterior teeth.
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41
Figure 2-15 Posterior Tooth Fossae and Grooves
b. Sulcus (Plural - sulci) - A long, narrow depression, usually
V-shaped in cross section,
located on the occlusal surface of each posterior tooth. A
primary developmental
groove is found at the bottom of the sulcus and the sides are
inclined planes of
triangular ridges.
c. Primary Developmental Groove - A groove or line which denotes
the border where
the primary parts, or lobes, of the tooth crown have coalesced.
The primary
developmental groove that travels mesiodistally along the center
of the tooth is called
the central developmental groove (Figure 2-15).
d. Supplemental (secondary) Developmental Groove - An auxiliary
groove that
branches from the primary developmental groove. Its location is
not related to the
junction of primary tooth parts. All grooves that are not
primary developmental
grooves are considered supplemental developmental grooves for
this course (Figure
2-15).
e. Triangular fossa - A depressed area that is formed by the
joining of three
developmental grooves. A pit is normally the deepest portion of
a fossa.
f. Pit - A small depressed point that is formed by two or more
grooves. The premolars
generally have mesial and distal pits at the base of the
triangular fossae. Molars
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42
generally have mesial and distal pits at the base of the
triangular fossae in addition to
a central pit formed by the convergence of developmental
groves.
C. Embrasures
The contact area is the area of interproximal contact between
two adjacent teeth.
Since the proximal surfaces of the teeth (mesial and distal) are
considerably larger in area
than the proximal contact area, there is a space between the two
teeth that surrounds the
interproximal contact where the teeth do not touch. This space
is termed an embrasure.
This space is actually a continuous space that surrounds the
contact area and
increases in width, as one moves facial, cervical, lingual or
occlusal from the
interproximal contact. Embrasures form an irregular area similar
to a "doughnut" with
the "hole" at the contact area (Figure 2-16).
Figure 2-16 Anterior Teeth Embrasures
Portions of this space (embrasure) are given several names
according to location.
The openings or spaces between the teeth, facial and lingual to
the contact area, are
termed the facial embrasure and lingual embrasure, respectively.
The small V-shaped
area between the teeth that is occlusal or incisal to the
contact area is termed the occlusal
or incisal embrasure.
The embrasure space cervical to the contact area is termed the
interproximal
embrasure, interproximal space, gingival embrasure, or cervical
embrasure. This
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43
triangular area between the crest of the alveolar bone and the
contact area is normally
filled by a pointed projection of the free gingiva termed the
interdental papilla or gingival
papilla (Figure 2-17).
Figure 2-17 Interdental papilla or gingival papilla
Embrasures serve as spillways for the food during mastication
and allow for proper
protection and stimulation of the periodontium necessary to
maintain healthy tissues. If
an imaginary line were drawn in a faciolingual direction
bisecting any embrasure space,
the two portions (a mesial portion and a distal portion) should
be approximately equal in
size and shape. It should follow from this that the portion of
each tooth that forms the
sides of the embrasures must be nearly mirror images of each
other. This is necessary to
provide our symmetrical embrasures.
1. Facial or Lingual View. a. The contact evenly divides the
embrasure space mesiodistally.
b. Gingival embrasures decrease in size (mainly occlusogingival
height) from anterior
to posterior. They increase in width (buccolingually) from
anterior to posterior
(Figures 2-18 and 2-19).
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44
Figure 2-18 Maxillary anterior tooth embrasures, labial view.
(This photo is of a
typodont; note that gingival embrasures would be filled with
gingival papillae in a
healthy patient).
Figure 2-19 Maxillary posterior tooth embrasures, buccal
view.
2. Incisal or Occlusal View. a. The interproximal contacts of
the anterior teeth are approximately centered
labiolingually for the thickness of the tooth at that height.
Lingual embrasures are
generally wider than labial embrasures (Figure 2-20).
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45
Figure 2-20 Maxillary central incisors reduced to expose
contact, incisal view.
b. The interproximal contacts of posterior teeth are generally
buccal to the buccolingual
center (Figure 2-21). The lingual embrasures are also wider than
the buccal
embrasures of the posterior teeth.
Figure 2-21 Maxillary posterior tooth embrasures, occlusal
view.
D. Proximal Contacts
The contacts between adjacent teeth (interproximal contacts) are
very important for
arch stability and the health of the periodontium. Their
buccolingual and occlusogingival
location, in addition to their size (surface area) are critical.
In a mesiodistal direction,
they should be centered over the interproximal space. This
allows the proximal
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46
embrasures to be divided into equal halves and allows a
symmetrical gingival papillae to
occupy the space.
Contact areas become more gingivally located from anterior to
posterior in each
quadrant when viewed from the facial or lingual. The majority of
this occlusogingival
effect is due to the crowns becoming shorter. On each tooth, the
distal contact area is
generally more cervical than the mesial contact area.
The surface area of the proximal contacts increases in size from
anterior to
posterior. Anterior teeth have relatively small proximal contact
areas that are centered
labiolingually, while posterior teeth have larger contact areas
that are generally located
buccal to the buccolingual center (Figures 2-18 through 2-21).
The contact areas become
larger with function (as an individual ages), because as one
chews, the adjacent teeth rub
against each other, causing contact areas to wear, and proximal
contact areas to increase
in size.
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47
Chapter 3. Anterior Teeth
A. Overview
When someone smiles or talks, the anterior teeth are the most
noticeable of the
dentition and their shape, alignment, and color are generally
extremely important to our
patients. It is tremendously difficult to make a single anterior
tooth or all of the anterior
teeth look natural and pleasing. Since esthetics is so important
to our patients, throughout
your dental career you will probably continually take classes on
how to improve your
anterior restorations.
When calipers are used to compare the mesial to distal
dimensions for the
maxillary central incisor and the maxillary lateral incisor,
this naturally occurring ratio
was found to be 1.2 to 1.0. There are other ratios that are used
by viewing the anterior
teeth from the front and other areas of the body. Additional
information can be obtained
by reading Chapter 3 of your Operative Dentistry Textbook.
1. Lobes Lobes are major anatomical divisions of the tooth and
understanding their extent
will help one better visualize the developmental grooves or
depressions that separate
them. The lobes are named according to their location, similar
to the way in which
surfaces and line angles are named.
All anterior teeth have four lobes: three labial lobes, termed
the mesiolabial,
middle labial (or simply labial) and distolabial lobe. The
fourth lobe is represented by the
cingulum and termed the lingual lobe (Figure 3-1).
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48
Figure 3-1 Maxillary anterior teeth lobes
In incisor teeth, mamelons are the rounded incisal terminations
of the three labial
lobes. Remember, these mamelons are usually worn away shortly
after the teeth erupt
into the mouth.
The separation of the three facial lobes creates two slight
vertical depressions in
the labial surface of anterior teeth. These are termed the
mesiolabial and distolabial
developmental depressions. The canines have larger, vertical
labial surface depressions
with a fairly prominent ridge (the middle labial lobe) between
them (Figure 3-2). The
lingual lobe of each anterior tooth forms the cingulum, and
there are only very subtle
depressions from its junction with the rest of the tooth.
Figure 3-2 Labial depressions on maxillary anterior teeth
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49
2. Tooth Outlines Geometric shapes (Figures 3-3 to 3-7) are used
to roughly describe the tooth shape
from various views. These shapes should be known for the
National Board Dental
Examination Part I that you will take next year.
Figure 3-3 General tooth outlines
Figure 3-4 Geometric shape for Figure 3-5 Geometric shape
for
incisal view of lateral incisor occlusal view of mandibular
first molar
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50
B. Incisors
Looking at a smiling mouth, one observes the facial surfaces of
the eight incisors.
The facial surface of each incisor crown has a trapezoidal
outline with the shorter of the
parallel sides at the gingival aspect and the longer at the
incisal (Figure 3-6). From a
proximal view (mesial or distal), all incisors have a triangular
outline (Figure 3-7). Try
to visualize this triangular-trapezoidal shape in three
dimensions to begin to form a visual
image of the incisors.
Figure 3-6 Trapezoidal facial outline Figure 3-7 Triangular
proximal outline
1. Line Angles All teeth have four vertical line angles (two
facial and two lingual). These form
the mesial and distal "boundaries" of the labial and lingual
surfaces. Surfaces and line
angles in the vertical plane are also described as axial
surfaces and axial line angles,
respectively. Examine the vertical line angles on the labial
surface (mesiolabial and
distolabial line angles) of the maxillary incisors.
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51
a. Labial Line Angles
From a facial view, the mesiolabial line angles of the maxillary
central incisors are
relatively long and straight when compared to the distolabial
line angles which are
somewhat shorter and more curved. The same relationship is true
for the maxillary
lateral incisor, although the lateral incisor shows more
curvature of both line angles
(Figure 3.8).
Figure 3-8 Maxillary anterior teeth's facial line angles
Viewing the incisal edges of these teeth, the maxillary central
incisor at the
mesiolabial line angle appears square or close to 90. The
maxillary central incisor at the
distolabial line angle is more rounded (greater than 90 angle),
Figure 3-9. Mesiodistally
along the facial surface between these boundaries, the incisal
one-third is relatively flat
except for two very slight vertical depressions.
If the teeth are tipped slightly to the lingual, and the middle
and gingival thirds of
the facial surface are observed, mesiodistally incisors have a
greater convexity as the
gingival margin is approached. The line angles also become
slightly more rounded (less
distinct) as the gingival line is approached (Figure 3-10). The
labial surface of the
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52
maxillary lateral incisor has a similar form to the maxillary
central incisor except the
lateral incisor is more round or more convex in all
locations.
Figure 3-9 Incisal edges Figure 3-10 Labial contours
When the mesiolabial and distolabial line angles of the
mandibular incisors are
observed from the facial aspect, they are fairly uniform and
straight (Figure 3-11). When
these line angles are observed from the incisal aspect, they are
very near 90. The labial
surfaces between these line angles are also relatively flat with
only slight rounding as the
dentinoenamel junction (DEJ) is approached.
Figure 3-11 Mandibular incisor facial line angles
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53
b. Lingual Line Angles
On the lingual surfaces of the maxillary incisors, observe how
the mesiolingual and
distolingual line angles coincide fairly well with the mesial
and distal marginal ridges
(Figure 3-12). Marginal ridges of anterior teeth were defined
previously as the mesial
and distal terminations of the lingual surfaces of anterior
teeth. Some maxillary central
incisors will have very prominent marginal ridges, while other
teeth have less distinct
marginal ridges.
The incisal one-third of the lingual surface between the
marginal ridges is flat to
slightly concave. In the middle and gingival thirds of the
lingual surface, this concavity
between the marginal ridges changes into a convexity, the
cingulum. The cingulum does
not lie in the center of the tooth, but is displaced distally.
The lingual surface of the
maxillary lateral incisor is similar except the marginal ridges,
fossa, and cingulum may
be slightly more distinct than for the central incisors (Figure
3-12).
Figure 3-12 Maxillary incisor lingual surfaces
The marginal ridges of some mandibular incisors are distinct,
while others are not
well defined. When well formed, the marginal ridges are only
distinct in the incisal third.
They blend into the cingulum as slight depressions in the middle
and gingival thirds. The
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54
remainder of the mandibular incisors lingual surface is less
concave and the cingulum is
less convex in comparison to the maxillary incisors (Figure
3-13).
Figure 3-13 Mandibular incisor lingual surfaces
c. Incisal Line Angles
When incisors erupt, they have mamelons, which rapidly wear
away. The
mandibular incisors often occlude with the lingual surfaces of
the maxillary incisors near
the incisal edges. As an individual protrudes and retrudes the
mandible, the incisal edges
rub across each other, forming a distinct wear pattern. The
incisal surfaces of the
maxillary incisors wear with an incline toward the lingual
surface, while the incisal
surfaces of the mandibular incisors wear with an inclination
toward the labial surface
(Figure 3-14).
The labio-incisal and linguo-incisal line angles are the incisal
boundaries of the
labial and lingual surfaces, respectively. Mesiodistally, these
line angles form fairly
parallel arcs (Figure 3-15).
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55
Figure 3-14 Incisal edge wear Figure 3-15 Incisal line
angles
Mesio-incisal and disto-incisal line angles are used to describe
the two incisal
"corners" as seen in a facial view. The mesio-incisal line angle
of the maxillary central
incisor is approximately a right angle, while the lateral
incisor's line angle is slightly
more rounded (Figure 3-16).
The disto-incisal line angle of the maxillary central incisor is
obtuse or more
rounded than its mesio-incisal line angle. Similarly, the
disto-incisal line angle of the
maxillary lateral incisor is more rounded than in the central
incisors (Figure 3-17).
Figure 3-16 Maxillary incisor Figure 3-17 Maxillary incisor
Mesio-incisal line angles disto-incisal line angles
The mesio-incisal and disto-incisal line angles of the
mandibular incisors are all
acute or approach 90. The disto-incisal angle of the mandibular
lateral incisors is the
only line angle that is slightly rounded (Figure 3-18).
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56
Figure 3-18 Mandibular incisor mesio-incisal and disto-incisal
line angles
The teeth tend to have a faciolingual taper (or lingual
convergence), which is
especially prevalent among the anterior teeth. In architecture,
if stone blocks are used to
build an arch, they must be wider on the outer surface than on
the inner surface (Figure 3-
19). This arch of blocks may be used to simulate an arch of
teeth. All but one of the
teeth are wider on their facial than on their lingual surfaces
(Figure 3-20). The one
exception: the maxillary first molar, which is wider on the
lingual aspect than on the
facial aspect.
Figure 3-19 Faciolingual taper Figure 3-20 Lingual convergence
of
maxillary teeth
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57
2. Proximal Contacts Proximal contacts must be observed from two
different views. From an incisal
view of anterior teeth, all contacts are centered labiolingually
in the incisal and middle
thirds of the teeth, depending on the location of the tooth in
the arch (Figure 3-21). From
a facial view, the contact between the maxillary central
incisors is near the incisal edge.
In the anterior teeth, the more distal the contact is from the
midline, the more cervical it is
located (Figure 3-22).
Figure 3-21 Maxillary incisor proximal Figure 3-22 Maxillary
incisor proximal
contacts, incisal view contacts, facial view
Although the exact location of proximal contacts vary, the
"average" dentition has
the contacts in the following locations and these will be used
in this course and may be
seen on your National Board Dental Examination Part I:
Maxillary Tooth Mesial Contact Distal Contact
Central Incisor I 1/3 I & M 1/3 Lateral Incisor I & M
1/3 M 1/3 Canine I & M 1/3 M 1/3
Definitions:
I 1/3 - Incisal one-third of proximal surface
M 1/3 - Middle one-third of proximal surface
I & M 1/3 - Junction of incisal and middle thirds of
proximal surface
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58
In the mandibular arch, the proximal contacts of the anterior
teeth are near the
incisal edge. In general, the proximal contacts move slightly
more gingival the more
distal the tooth's location. The middle one-third is not reached
until the distal of the
canine (Figure 3-23).
Figure 3-23 Mandibular incisor proximal contacts, frontal
view
Mandibular Tooth Mesial Contact Distal Contact
Central Incisor I 1/3 I 1/3 Lateral Incisor I 1/3 I 1/3 Canine I
1/3 M 1/3
3. Embrasures Place a large rubber band around the facial
surfaces of the maxillary dentiform
(Figure 3-24). It should be near the incisal edges of the
anterior teeth. This will make the
facial embrasures easier to visualize from an incisal view. Note
the curvature of the
rubber band around the anterior segment. The rubber band will
make the facial
embrasures appear as small triangular shaped spaces. Note the
shapes and relative sizes
of these embrasures. Note especially the shape of the portions
of the teeth that form the
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59
other two sides of this triangular space. Note the "regular" or
uniform appearance of the
embrasures (Figure 3-25).
Figure 3-24 Rubber band on typodont Figure 3-25 Rubber band
bordering
embrasures
For the embrasures to have this symmetrical form, the portions
of the two adjacent
teeth that form each embrasure must be of very similar form.
These adjacent parts of the
two teeth forming the embrasure are approximate mirror images of
each other.
Remove one of the maxillary central incisors from the dentiform.
Place a mouth
mirror against the mesial surface of the central incisor
remaining in the dentiform (Figure
3-26).
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60
Figure 3-26 Embrasures should "mirror image" each other
Study the embrasures formed between the central incisor and its
image. When
forming a tooth in wax, the borders of the wax pattern that form
the embrasure with the
adjacent tooth can be shaped to form an ideal embrasure. These
border positions can then
act as landmarks in forming the remainder of the tooth. This
ability to form the border
portions of teeth in proper relationship to adjacent structures
will be a skill vital to
success in carving teeth to correct form.
The incisal and gingival embrasures should also be studied at
this time. Review
the mesial and distal incisal angles of the incisors; these
angles are the "sides" of the
embrasures. Study the characteristics of each embrasure
individually, i.e., the incisal
embrasure between the two maxillary central incisors is a very
small, V-shaped area
(Figure 3-27). The characteristic shape is dictated by the
nearly square form of the
mesio-incisal angles and the location of the proximal contact in
the incisal one-third.
Compare the incisal embrasures among the other anterior teeth.
The incisal embrasures
in both arches generally become slightly wider (more open) the
more distal their location
is in the arch. Incisal embrasures also become slightly taller
as the proximal contacts
move gingivally.
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61
Figure 3-27 Incisal and gingival embrasures
4. Contours The tooth's contours are its convexities and
concavities. The height-of-contour is
the tooth's maximal bulge on the facial, lingual, mesial, or
distal surface, measured in the
incisocervical or occlusocervical direction. The
height-of-contour is usually expressed as
being in the cervical, middle, or occlusal third of the tooth.
These heights of contour
must be memorized for the facial and lingual surfaces and the
interproximal contacts for
the mesial and distal surfaces. These will be asked in test
questions for this course and
the National Board Dental Examination Part I.
In Figure 3-28, observe the tooth's contour coronal to the
gingival tissue and think
about the tooth's height-of-contour locations.
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Figure 3-28 Height-of-contour
Using the typodont, view the contour of the anterior teeth
immediately adjacent to
the gingiva on the facial and lingual surfaces. Note that the
tooth does not have a bulge
above the gingiva. Each height-of-contour is the convexity
incisal to the CEJ. It must be
noted that in an ideal gingiva to tooth relationship, the
undercut area (area cervical to the
height-of-contour) of the tooth is covered by the gingiva.
The angulations of the teeth in the arch also influence the
tooth contour. This is
best illustrated by removing a maxillary central incisor from
the arch and noting the bulge
of the cingulum when the tooth is positioned vertically. Replace
the tooth firmly into the
typodont and note the relationship of the lingual gingiva to the
cingulum. The height of
the gingiva and the tooth's labial angulation result in a tooth
that does not have undercuts
that would tend to retain plaque.
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C. Summary Maxillary Anterior Teeth
1. Maxillary Central Incisor Labial View (Figure 3-29)
1. Anatomical crown length is greater than width.
2. Facial crown outline is trapezoidal with shorter parallel
side at the cervical.
3. Incisal outline (edge) is relatively straight.
4. Mesial outline is only slightly convex (relatively
straight).
5. Mesial contact area is in incisal one-third.
6. Distal outline is more convex (more rounded) than mesial
outline.
7. Distal contact area is at junction of incisal and middle
thirds.
8. Mesio-incisal angle is acute or near right angle.
9. Disto-incisal angle is more rounded than mesio-incisal.
10. Single root is basically cone shaped with a blunt apex.
11. Apex of root is usually slightly distal to long axis of
tooth.
Lingual View (Figure 3-30)
1. There is shallow lingual fossa in the incisal and middle
one-third of the lingual surface.
2. Lingual fossa boundaries are the incisal ridge, mesial and
distal marginal ridges and the cingulum.
3. Cingulum is located slightly to the distal of center, or it
can be said that the mesial side of the cingulum is longer than the
distal side.
4. Crown and root taper lingually, therefore some of mesial and
distal surfaces can be seen from a lingual view.
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Figure 3-29 Maxillary central incisor, Figure 3-30 Maxillary
central incisor,
facial view lingual view
Mesial View (Figure 3-31)
1. The crown is triangular in outline with the base at the
cervical.
2. The labial outline is just slightly curved.
3. The lingual outline is slightly convex in the cingulum area
and reverses to be slightly concave in the incisal two-thirds.
4. The anatomical crown is widest labiolingually in the cervical
one-third.
5. A line drawn through the long axis of the tooth will bisect
the apex of the root and the incisal edge.
6. The cervical line is curved more incisally than on any other
tooth.
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Distal View (Figure 3-32)
Note: The distal view characteristics that are the same as the
mesial view are
not repeated, i.e., triangular outline, etc.
1. The incisal one-third of the crown appears to be thicker than
from a mesial view due to the more rounded curvature of the
distolabial area.
2. Curvature of cervical line is less than on mesial.
Figure 3-31 Maxillary central incisor, Figure 3-32 Maxillary
central incisor,
mesial view distal view
Incisal View (Figure 3-33)
1. The outline is roughly triangular with the base being the
broad labial surface and the tooth converging lingually.
2. Incisal edge is relatively straight mesiodistally and bisects
labiolingual diameter.
3. Crest of cingulum is located slightly to the distal of the
center of the lingual surface.
4. Mesial and distal contact areas are located near the centers
of the proximal surfaces labiolingually.
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5. Distolabial line angle is more obtuse than mesiolabial line
angle.
6. Slight developmental depressions are on the labial
surface.
Figure 3-33 Maxillary central incisor, incisal view
2. Maxillary Lateral Incisor Labial View (Figure 3-34)
1. Crown is smaller than the central incisors crown and the
difference between the crowns length and width is more apparent
than with the central incisor.
2. Crown outline is trapezoidal.
3. Incisal outline is more curved than the central incisor's
outline.
4. Mesial outline is slightly rounded.
5. Mesial contact area is in the incisal one-third.
6. Distal outline is very convex or rounded.
7. Distal contact area is in the middle one-third.
8. Mesio-incisal line angle is slightly rounded.
9. Disto-incisal line angle is distinctly curved or rounded.
10. Root is pointed and as long or longer than the central
incisors root.
11. Root apex is most often curved sharply to the distal.
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Lingual View (Figure 3-35)
1. Lingual fossa is usually deeper than the central incisors
fossa.
2. Mesial and distal marginal ridges are more prominent than the
central incisors marginal ridge.
3. The cingulum is more rounded than the central incisors
cingulum.
4. There is often a linguogingival fissure on the distal side of
the cingulum, that can
run below the CEJ and cause localized periodontal problems.
Figure 3-34 Maxillary lateral incisor, Figure 3-35 Maxillary
lateral incisor,
facial view lingual view
Mesial View (Figure 3-36)
1. The crown is triangular in outline with the base of the
triangle relatively narrower than the central incisors.
2. The labial outline is slightly curved.
3. The lingual outline is slightly concave in the middle and
cervical thirds.
4. The incisal edge and apex of the root are on a line through
the long axis of the tooth.
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Distal View (Figure 3-37)
1. As in the central incisor, the incisal one-third of the crown
appears thicker than in the mesial view due to the curvature of the
distolabial line angle to the lingual.
Figure 3-36 Maxillary lateral incisor, Figure 3-37 Maxillary
lateral incisor,
mesial view distal view
Incisal View (Figure 3-38)
1. The outline is similar to, but shows more convexity labially
and lingually than the central incisor. This provides more of an
ovoid outline compared to the central incisor's triangular
outline.
2. The incisal edge is slightly convex to the labial. The
incisal ridge is more prominent (curved more lingually) than with
the central incisors.
3. The crest of the cingulum is slightly to the distal of the
center of the tooth.
4. Mesial and distal contact areas are centered
labiolingually.
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Figure 3-38 Maxillary lateral incisor, incisal view
3. Maxillary Canine Labial View (Figure 3-39)
1. The cusp tip of is slightly mesial to center of crown.
2. Mesial outline is slightly convex.
3. Mesial contact area is at the junction of incisal and middle
one-third.
4. Distal outline is very convex at contact area with a concave
outline in the cervical third.
5. Distal contact area is in the center of the middle one-third
of the distal surface of the crown.
6. The mesial cusp arm (cusp arms are the length from the cusp
tip to the respective incisoproximal angle) is shorter than the
distal cusp arm. Both have slight developmental depressions.
Lingual View (Figure 3-40)
1. Has the most prominent cingulum in the mouth.
2. There is a well-developed lingual ridge in the center running
incisocervical from the cusp tip to the cingulum. It is most
prominent in the incisal one-third near the cusp tip and blends
into the lingual surface toward the cingulum.
3. Mesial and distal marginal ridges are well developed.
4. There are sometimes slight concave mesial and distal fossae,
bordered by the lingual ridge and the mesial and distal marginal
ridges.
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Figure 3-39 Maxillary canine, Figure 3-40 Maxillary canine,
facial view lingual view
Mesial View (Figure 3-41)
1. The outline of the crown is triangular.
2. The labial outline is slightly convex.
3. Lingual outline is a fairly straight slope in the incisal
one-half and very convex in
the cingulum area.
4. When wear has taken place, the worn cusp tip and cusp arm
will face lingually.
5. The cusp tip is labial to the root apex.
Distal View (Figure 3-42)
1. There is a definite concavity in the distal surface of the
crown between the contact area and the CEJ.
2. The distal marginal ridge is heavier than its mesial
counterpart.
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Figure 3-41 Maxillary canine, Figure 3-42 Maxillary canine,
mesial view distal view
Incisal View (Figure 3-43)
1. Mesial and distal contact areas are centered
labiolingually.
2. The cusp ridges (mesial & distal cusp arms) are
approximately centered labiolingually or slightly labial to the
center.
3. There are two developmental depressions on the labial
surface. The mesial developmental depression is very slight and
confined mainly to the incisal portion, while the distal is more
concave and extends more cervically than the mesial.
Figure 3-43 Maxillary canine, incisal view
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D. Review Maxillary Anterior Teeth
Figure 3-44 Review maxillary anterior teeth, labial, incisal and
lingual views
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Figure 3-45 Review maxillary anterior teeth, mesial and distal
views
1. Maxillary Central Incisor Right Left Proximal Contact
locations: Universal Code: 8 9 Mesial: incisal third International
Code: 1-1 2-1 Distal: junction of incisal and middle thirds Palmer
Notation: 1| |1 No. of terminal roots: 1 Height-of-Contour: No. of
pulp horns (facial view): 3 Facial: cervical third No. of cusps:
none Lingual: cervical third No. of developmental lobes: 4
Identifying characteristics: The largest and most prominent
incisor. Disto-incisal angle is more rounded than mesio-incisal.
Prominent lingual features are cingulum, lingual fossa, and
marginal ridges. It may have lingual pit. Has a large, simple pulp
cavity with one root canal. It is not likely to have longitudinal
grooves on root.
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Average Anatomic Average Average Mesiodistal Crown Height Root
Length Crown Width
10.5 mm 13.0 mm 8.5 mm
2. Maxillary Lateral Incisor Right Left Proximal Contact
locations: Universal Code: 7 10 Mesial: junction of incisal and
middle thirds International Code: 1-2 2-2 Distal: middle third
Palmer Notation: 2| |2 No. of terminal roots: 1 Height-of-Contour:
No. of pulp horns (facial view): 2 Facial: cervical third No. of
cusps: none Lingual: cervical third No. of developmental lobes: 4
Identifying characteristics: Is similar to, but smaller than the
maxillary central incisor. Has more prominent marginal ridge and
lingual fossa than central incisor and occasionally has a DL
developmental groove along the distolingual aspect that may travel
through the gingival attachment and sometimes along the root.
Usually has two rather than three pulp horns. Has apical accessory
canals more frequently than other incisors. Average Anatomic
Average Average Mesiodistal Crown Height Root Length Crown
Width
9.0 mm 13.0 mm 6.5 mm
3. Maxillary Canine Right Left Proximal Contact locations:
Universal Code: 6 11 Mesial: junction of incisal and middle thirds
International Code: 1-3 2-3 Distal: middle third Palmer Notation:
3| |3 No. of terminal roots: 1 Height-of-Contour: No. of pulp horns
(facial view): 1 Facial: cervical third No. of cusps: 1 Lingual:
cervical third No. of developmental lobes: 4
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Identifying characteristics: Is the largest single rooted tooth
in the mouth. Its cingulum is centered mesiodistally. Its prominent
facial ridge is off-center, toward the mesial. It has a distinct
lingual ridge running incisocervical, two lingual fossae on both
sides of the ridge, and a prominent cingulum. Average Anatomic
Average Average Mesiodistal Crown Height Root Length Crown
Width
10.0 mm 17.0 mm 7.5 mm
E. Summary Mandibular Anterior Teeth
1. Mandibular Central and Lateral Incisors Labial View (Figure
3-46)
1. The crowns appear to be approximately twice as long as they
are wide. The lateral incisor is wider (about 0.5 mm) than the
central incisor, with most of the extra width on the distal
surface.
2. The crown outline is trapezoidal.
3. Incisal outline is straight.
4. Mesial and distal outlines are straight.
5. The distal side of the lateral is often shorter than the
mesial side causing the incisal edge (which is straight) to slope
downward in a distal direction.
6. Mesial and distal contact areas are in the incisal one-third
near the incisal angles. The distal contact area of the lateral
incisor is slightly more cervical than the other three contact
areas.
7. The mesio-incisal angles of central and lateral incisors are
sharp.
8. The disto-incisal angle of the central is sharp and the
disto-incisal angle of the lateral is slightly rounded.
9. There are no developmental depressions on the labial
surface.
10. Roots are thin and tapered and often curved slightly to the
distal.
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Lingual View (Figure 3-47)
1. Lingual surfaces of both central and lateral are smooth and
rounded with no distinct lingual fossae.
2. Mesial and distal marginal ridges are only very minor
elevations.
3. Some mandibular incisors have distinct mesial and distal
marginal ridges. They are prominent only in the incisal
one-third.
4. The cingulum (or cingula) are much less distinct than in
their maxillary
counterparts.
Figure 3-46 Mandibular central and Figure 3-47 Mandibular
central and
lateral incisors, facial view lateral incisors, lingual view
Mesial and Distal Views (Figures 3-48 and 3-49)
1. The crowns have a very pointed triangular outline.
2. The labial outline of the crowns is curved in the cervical
one-third and is then straight from the crest of this curvature to
the incisal edge.
3. The incisal edge is lingual to the long axis of the
tooth.
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4. The incisal surface, when worn, angles to the labial.
5. The cervical lines extend about 1 mm more apically on the
lingual side than on the labial side.
6. The roots taper evenly to a blunt apex and have mesial and
distal depressions in the proximal root surfaces.
Figure 3-48 Mandibular central Figure 3-49 Mandibular
lateral
incisor, mesial view incisor, distal view
Incisal View (Figure 3-50)
1. The incisal edge of the central incisor is lingual to the
center of the tooth and
straight.
2. The incisal edge of the lateral incisor is lingual to the
center of the tooth, but slants to the distolingual to start the
curve of the arch.
3. Both teeth converge lingually.
4. The proximal contacts are centered labiolingually.
5. The lateral incisor appears twisted on its axis in a
distolingual direction in comparison to the symmetrical
central.
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Figure 3-50 Mandibular central and lateral incisors, incisal
view
2. Mandibular Canine Labial View (Figure 3-51)
1. Compared to the maxillary canine, the crown is narrower and
as long or longer.
2. The mesial outline is straight and in line with the mesial
outline of the root.
3. The mesial contact area is in the incisal one-third.
4. The distal outline is concave cervical to the contact area,
but not to the degree of that in the maxillary canine.
5. The distal contact area is at the junction of incisal and
middle one-third.
6. The mesial cusp arm is shorter and more horizontal than the
distal cusp arm. The distal cusp arm slopes apically.
Lingual View (Figure 3-52)
1. The lingual surface is relatively flat and smooth.
2. The cingulum is poorly developed.
3. The marginal ridges are only very slight elevations.
4. The root narrows more lingually than the root of the
maxillary canine.
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Figure 3-51 Mandibular canine, Figure 3-52 Mandibular
canine,
facial view lingual view
Mesial and Distal Views (Figures 3-53 and 3-54)
1. The labial outline is fairly straight incisal to the slight
cervical curvature.
2. The lingual outline is slightly more concave and slopes more
apically than the maxillary lingual outline due to the less
prominent cingulum in the mandibular.
3. The cusp tip is lingual to the root apex.
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Figure 3-53 Mandibular canine, Figure 3-54 Mandibular
canine,
mesial view distal view
Incisal View (Figure 3-55)
1. The labial outline is less convex than the maxillary
canine.
2. The cusp tip and mesial cusp arm are inclined slightly to the
lingual.
Figure 3-55 Mandibular canine, incisal view
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F. Review Mandibular Anterior Teeth
Figure 3-56 Review mandibular anterior teeth, labial, incisal
and lingual views
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1. Mandibular Central Incisor Right Left Proximal Contact
locations: Universal Code: 25 24 Mesial: incisal third
International Code: 4-1 3-1 Distal: incisal third ___ ___
Palmer Notation: 1| |1 No. of terminal roots: 1
Height-of-Contour: No. of pulp horns (facial view): generally 1
Facial: cervical third No. of cusps: none Lingual: cervical third
No. of developmental lobes: 4 Identifying characteristics: The
mesio-incisal and disto-incisal angles are very similar and acute.
Has less prominent lingual features than on maxillary incisors.
From a proximal view, the incisal edge is displaced toward the
lingual. The root is flat and the faciolingual wider than the
mesiodistal. Average Anatomic Average Average Mesiodistal Crown
Height Root Length Crown Width
9.0 mm 12.5 mm 5.0 mm
2. Mandibular Lateral Incisor Right Left Proximal Contact
locations: Universal Code: 26 23 Mesial: incisal third
International Code: 4-2 3-2 Distal: incisal third ___ ___
Palmer Notation: 2| |2 No. of terminal roots: 1
Height-of-Contour: No. of pulp horns (facial view):generally 1
Facial: cervical third No. of cusps: none Lingual: cervical third
No. of developmental lobes: 4 Identifying characteristics: Compared
to the mandibular central incisor, its crown is slightly wider
mesiodistally. The distal end of the incisal edge is rotated toward
the lingual. Its root is larger than the mandibular central incisor
root.
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Average Anatomic Average Average Mesiodistal Crown Height Root
Length Crown Width 9.5 mm 14.0 mm 5.5 mm
3. Mandibular Canine Right Left Proximal Contact locations:
Universal Code: 27 22 Mesial: incisal third International Code: 4-3
3-3 Distal: middle third ___ ___
Palmer Notation: 3| |3 No. of terminal roots: 1 or 2
Height-of-Contour: No. of pulp horns (facial view): 1 Facial:
cervical third No. of cusps: 1 Lingual: cervical third No. of
developmental lobes: 4 Identifying characteristics: Compared to the
maxillary canine, its crown is longer, narrower, and has with less
prominent lingual features. The cusp tip is inclined to the lingual
and the distal end of the incisal edge is rotated to the lingual.
It has the longest root in the mandibular