Heterodont: Man is a heterodont, which means that he has differentshaped

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DR. Huda Msaed Lafta Dental anatomy

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Introduction to Dental Anatomy

The field of dental anatomy is dedicated to the study of teeth including their development, eruption, morphology, classification, nomenclature and function.

Terminology:

Dense: tooth.

Dental: anything related to teeth.

Diphyodont: A condition where two generations of teeth are present in a lifetime (deciduous/primary dentition and permanent dentition).

Heterodont: Man is a heterodont, which means that he has different- shaped teeth.

Deciduous/Primary Dentition: The primary dentition is called so since they are the first set of teeth to appear in the oral cavity. The term deciduous implies that they are shed/fall off naturally.

The primary dentition consists of a total of 20 teeth, 10 in each jaw.

The primary teeth begin to emerge into the oral cavity at about 6 months of age and the child would have his/her complete set of primary teeth by 2½ to 3 years.

(Fig.1) Primary dentition

Dental Formula for Primary/Deciduous Dentition

The primary dentition has the following dental formula: (on each side).

I: Incisors (central and lateral) C: Canines

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M: Molars (first and second)

(Expressed as 2:1:2, i.e. two: one: two).

Each quadrant in primary dentition has five teeth; beginning from the midline they are the central incisor, the lateral incisor, the canine, the 1st molar and the 2nd molar.

Permanent/Secondary/Succedaneous Dentition

There is a total of 32 teeth in the permanent dentition, 16 in each jaw. The permanent teeth are also called as succedaneous teeth/secondary teeth since they replace or succeed the primary teeth.

• The permanent teeth begin to emerge at 6 years of age and gradually replace the smaller primary teeth. The eruption process is completed by 12 to 13 years except for the posterior most teeth, the four 3rd molars which erupt around 18 to 25 years of age.

• The permanent molars are not succedaneous teeth as they do not have predecessors.

Fig. 2 permanent teeth

Dental Formula for Permanent Dentition

In permanent dentition, the premolars are present in addition to incisors, canines and molars; the number of molar teeth is increased to three. The dental formula for permanent dentition is as follows:

(On each side)

I: Incisors (central and lateral) C: Canines

P: Premolars (first and second) M: Molars (first, second and third)

(Expressed as 2:1:2:3, i.e. two: one: two: three)

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The permanent dentition consists of 16 teeth in each jaw and 8 in each quadrant. The teeth present in each quadrant from the midline are; central and lateral incisors, canine, 1st and 2nd premolars, followed by 1st, 2nd and 3^rd molars.

The Jaws

The jaw is the bone which carries the teeth. There are two jaws:

1. The upper jaw, which is fixed, and is called “The Maxilla”.

2. The lower jaw, which is movable, and is called “The Mandible”.

Arrangement in the Dental Arches

1. The teeth in the upper jaw" the maxilla" are called the maxillary or upper teeth.

2. The teeth in the lower jaw, "the mandible" are called the mandibular/

lower teeth.

Anterior and Posterior Teeth Teeth are grouped into:

1. Anterior teeth which include the incisors and the canines.

2. Posterior teeth which include the premolars and molars.

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LEC.2 TOOTH NOTATION SYSTEMS DR. HUDA MSAED

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Tooth Notation Systems

In clinical practice, some “short-hand” system of tooth notation is necessary for recording data. When identifying a specific tooth, one has to list the dentition, dental arch, quadrant, and the tooth name.

Tooth notation provides:

1. Standard and an easy way of communication among dental professionals, students, and care providers.

2. It also gives a convenient method of record keeping in dental practice.

Although there have been more than 32 different tooth notation

systems, 3 systems are commonly in use and they are discussed in this lecture.

UNIVERSAL NOTATION SYSTEM

This system uses continuous numbers and letters to denote each tooth.

In this system, irrespective of the dentition, numbering always starts from the last tooth in the upper right quadrant and ends with the last tooth in the lower right quadrant.

A- Permanent teeth: for the permanent dentition, the maxillary teeth are numbered from 1 through 16, beginning with the right third molar. Beginning with the mandibular left third molar, the teeth are numbered 17through 32.

Left

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17

Right

Mandibular Maxilla

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Examples:

# 23: permanent mandibular left lateral incisor.

#6: permanent maxillary right canine.

#18: permanent mandibular left second molar.

B- Deciduous teeth: for the primary dentition uses uppercase letters for each of the primary teeth: For the maxillary teeth, beginning with the right second molar, letters A through J, and for the mandibular teeth, letters K through T, beginning with the left mandibular second molar. The universal system notation for the entire primary dentition is as follows:

Examples:

#B: primary maxillary right first molar.

#F: primary maxillary left central incisor.

#R: primary mandibular right canine.

A B C D E F G H I J T S R Q P O N M L K

Right

Maxillary

Mandibular Left

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Zsigmondy-Palmer SYSTEM/ quadrant system/grid system

In the Palmer system, the mouth is divided into 4 sections called the quadrants. The system uses a unique ‘L’ shaped symbol/grid. (┌,

┐,└, ┘) to depict in which quadrant the specific tooth is found. The vertical line segment of the ‘symbol’ indicates the patient’s midline and the horizontal line indicates the occlusal plane that separates the upper and lower arches.

• Maxillary right quadrant... ┘

• Maxillary left quadrant... └

• Mandibular right quadrant... ┐

• Mandibular left quadrant... ┌

A- Permanent Dentition: beginning with the central incisors, the teeth are numbered 1through 8 in each arch.

Examples:

8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8

Right

Maxillary

3 Permanent mandibular left canine

7 Permanent maxillary right second molar

6 Permanent mandibular right first molar

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4 Primary maxillary right second molar.

Primary mandibular right lateral incisor.

Primary mandibular left canine.

B- Deciduous Dentition:beginning with primary central incisors, the teeth are numbered A through E in each arch.

Examples:

E D C B A A B C D E E D C B A A B C D E

Right

Maxillary

B E

C

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FDI NOTATION SYSTEM/Two-digit System

The FDI system uses two-digit for each tooth—permanent and primary.

The first-digit always denotes the quadrant: each quadrant is assigned a number 1 to 4 for the permanent dentition and 5 to 8 for the primary dentition. The quadrant code denotes the dentition, arch, and side in which the tooth is present. The second digit denotes the tooth (1 to 8 for permanent teeth and 1 to 5 for deciduous teeth). The teeth are numbered from the midline to posterior. The two-digit combination of quadrant code and tooth code gives the notation of a specific tooth.

A- permanent teeth

# 17: permanent maxillary right second molar.

# 31: permanent mandibular left central incisor.

# 44: permanent mandibular right first premolar.

18 17 16 15 14 13 12 11 21 22 23 24 25 26 27 28 48 47 46 45 44 43 42 41 31 32 33 34 35 36 37 38 Right

Maxillary

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B. Deciduous Teeth

# 61: deciduous maxillary left central incisor.

#53: deciduous maxillary right canine.

#85: deciduous mandibular right second molar.

PARTS OF TOOTH

Any tooth has two main parts:

Anatomic crown: Anatomic crown is defined as the part of the tooth that is covered by enamel.

Anatomic root: Anatomic root is that portion of the tooth that is covered by cementum the crown and the root joined the cement enamel junction (CEJ)or cervical line.

CEJ 55 54 53 52 51 61 62 63 64 65 85 84 83 82 81 71 72 73 74 75

Right

Maxillary

85

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Clinical crown: Clinical crown is the part of a tooth that is visible in the oral cavity.

Clinical root: Clinical root is that part of a tooth which is under the gingiva and not exposed to the oral cavity.

Dental pulp: is the specialized connective tissue that carries blood and nerve supply to the tooth.

Pulp chamber: Is the portion of the pulp in the crown.

Pulp canal: is the portion of the pulp in the root.

The number of roots:

1. Single root: in all anterior teeth, mandibular premolars and maxillary second premolar.

2. Two roots with bifurcation: in mandibular molars and maxillary first premolar.

3. Three roots with trifurcation: in maxillary molars.

STRUCTURE OF TOOTH

Enamel: is the hardest substance in the human body consisting of more than 96 percent inorganic material.

Dentin: forms the major bulk of the tooth. It is present in both crown and root portions.

Cementum: is a hard avascular tissue that covers the roots of teeth.

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Surfaces of Teeth

Five surfaces can be recognized on the crowns of all the teeth.

1. Labial/Buccal Surface

Labial surface: Is the surface of the teeth toward the lips (incisors and canine) anterior teeth.

Buccal surface: Is the surface of teeth toward the cheeks (premolars and molars).

2. Lingual Surface:

Is the surface of a tooth facing the tongue.

It is used for both maxillary and mandibular teeth. In the case of maxillary teeth, the term palatal surface.

3. Mesial and Distal (Proximal)

Proximal surfaces: are the surfaces of the teeth that facing toward the adjacent teeth in the same dental arch.

The mesial surface: is the surface of the tooth that is nearest to the median line.

Distal surface: the surface of the tooth that is away from the median line.

4. Incisal/Occlusal Surface

The surfaces of teeth that come in contact with those in the opposing jaw during mastication are called the incisal surface in case of anterior teeth and occlusal surface in case of posterior teeth.

Line Angles:

A line angle is formed by the junction of two surfaces. It is named from the combination of the two surfaces that join, e.g. the

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junction of mesial and buccal walls of a tooth is called the mesiobuccal line angle.

Point Angles:

A point angle is formed where three surfaces meet on the crown, and the name is derived from the same.

DIVISIONS OF CROWN AND ROOT INTO THIRDS

Divisions of crown: The crown may be divided into thirds in three directions:

1. Mesiodistally: it is divided into the mesial, middle, and distal thirds.

2. Cervico-occlusally/cervicoincisally: The crown is divided into an incisal or occlusal third, a middle third.

3. Faciolingually. Labial or buccal third, middle third, lingual third.

DIVISIONS OF THE ROOT

Divisions of the root mesiodistally and faciolingually are exactly similar to that of the crown.

Cervico-occlusally, the root may be divided into:

•• Cervical third

•• Middle third

•• Apical third.

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Lec 3 Dental Anatomy dr. Huda Msaed

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Anatomical Landmarks

In order to study an individual tooth, we must be able to recognize all landmarks of importance by name. These include:

Cusp, tubercle, cingulum, ridge, marginal ridge, oblique ridge, triangular ridge, transverse ridge, fossa, sulcus, developmental groove, supplemental groove and lobe.

1. Cusp: it is an elevation or mound on the crown portion of a tooth making up a divisional part of the occlusal surface Cusps are present in the posterior teeth and the canines.

2. Tubercle

It is a smaller elevation on some portion of the crown produced by an extra formation of enamel. A tubercle may be found on the lingual surface of a maxillary lateral incisor.

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3. Cingulum: Cingulum (Latin word for “girdle”) is a mound on the cervical third of the lingual surfaces of anterior teeth.

4. Ridges:

A ridge is any linear elevation on the surface of a tooth. It is named according to its location.

a. Marginal ridge:All teeth have two marginal ridges; mesial and distal. These are rounded borders of enamel that form the mesial and distal margins of the occlusal surface of posterior teeth. In case of anteriors, the mesial and distal ridges form the mesial and distal margins of the lingual surfaces.

1

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b. Triangular ridges: Triangular ridge is found on the occlusal surface of premolars and molars. It is the ridge that descends from each cusp tip towards the center of the occlusal surface of a

posterior tooth. Triangular ridges are so named because the

inclined planes on either side of the ridge resemble two sides of a triangle. They take the name of the cusp they belong to, e.g.

triangular ridge of the buccal cusp of mandibular permanent 1st premolar.

c. Transverse ridge: it is the union of two triangular ridges crossing transversely the surface of a posterior teeth.

D. Oblique ridge: oblique ridge is a ridge crossing obliquely the occlusal surfaces of maxillary molars and formed by the union of the

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triangular ridge of the distobuccal cusp and the distal cusp ridge of the mesiolingual cusp

5. Fossa: it is an irregular depression or concavity.

(a) Lingual fossa: it is located on the lingual surface of anterior teeth and lower first premolar.

(b) Central fossa: it is located on the occlusal surface of molars.

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it is located on the occlusal surfaces of molars and c) Triangular fossa:

(

premolars, mesial or distal to marginal ridges

6. Sulcus

A sulcus is a long depression or valley in the surface of a tooth between ridges and cusps, the inclines of which meet at an angle.

7. Developmental groove: A developmental groove is a sharply defined groove or line separating the lobes or the primary parts of the crown or root, the central developmental groove running mesiodistally on the occlusal surface of a molar separates the buccal and lingual cusps

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8. Supplemental groove: it is a less distinct, shallow linear depression on the surface of a tooth, but is supplemental to a developmental groove and does not mark the junction of primary parts.

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9. Pit: it is a small pinpoint depression located at the junction of developmental grooves or at terminals of those grooves, e.g., central pit is a term used to describe a landmark in the central fossa of molars where developmental grooves join.

10. Mamelon: it is any one of the three rounded protuberances found on the incisal ridges of newly erupted incisor teeth.

11. Lobe: it is one of the primary sections of formation in the development of the crown. Cusps and mamelons are representative of lobes.

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LANDMARKS ON THE ROOT

Root trunk is present only in multirooted teeth. It is the undivided part of the root near the cervical line. Root trunk is very short and nearly absent in primary molars.

Furcation is the place on multirooted teeth where the root trunk divides into separates roots. Mandibular molars and maxillary 1st premolars are bifurcated while the maxillary molars are trifurcated.

The apex of the root is the tip at the end of the root.

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Lec 4 permanent incisor DR. zainab mahmood

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In the maxillary arch, the central incisor is larger than the lateral incisor, whereas in the mandibular arch the lateral incisor is larger. All the incisors have single root so There are eight incisors; four in each arch and two in each quadrant. .

FUNCTIONS OF INCISORS

 biting, cutting and shearing the food during masticatory process

 They are of great importance in esthetics

 phonation

Common characteristics of all incisors:

 Incisal ridge and edge: Incisal ridge is that portion of the crown which makes up the complete incisal portion.

The term Incisal edge is used when an angle is formed by the occlusal wear which creates flattened surface linguo-incisally.

edge implies an angle formed by the merging of two flat surfaces.

 The newly erupted incisors have three rounded eminences on their incisal portion called the mamelons. The mamelons disappear as soon as the incisal surface of the tooth gets worn by mastication.

 Marginal ridges are longitudinally positioned .

 incisors have cingulum at the cervical portion of their lingual aspects and concave lingual fossa at the center of lingual surfaces.

 The cervical lines on their proximal surfaces exhibit greater curvature than on other teeth.

 •• They have single, cone shaped tapering roots

Maxillary central incisor

Labial aspect: trapezoidal

 The mesial outline of the crown is only slightly convex, with the crest of curvature (representing the contact area) approaching the mesioincisal angle

 Distal outline: is more convex than the mesial outline. The distoincisal angle is more rounded.The crest of curvature of the distal outline (distal contact, area) is higher towards the cervical line, at the junction of incisal and middle third of the crown.

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pg. 2

 The labial surface of maxillary central incisor is smooth and convex both mesiodistally and cervicoincisally.

 A line drawn through the center of the root and crown tends to parallel the mesial outline of the crown and root.

It is the widest anterior tooth mesio-distally 



Lingual Aspect

General shape of lingual aspect is also a trapezoid

 The cervical outline curves apically.

 Lingual surface of crown and root is narrower than the labial surface as the mesial and distal walls taper towards lingual aspect (lingual convergence).

 Because of this lingual convergence, the labial line angles can be viewed from lingual aspect.

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pg. 3

 Unlike labial aspect, lingual surface is irregular with convexities and a concavity.

 The convexity found immediately below the cervical line is called the “cingulum”which is found on lingual surfaces "of all

anteriors" immediately below the cervical line. It occupies the cervical third of lingual surface. And the central concavity is the

“lingual fossa”.

 Lingual fossa is bordered cervically by the cingulum, mesially by the mesial marginal ridge, distally by the distal marginal ridge and incisally by the incisal ridge.

Mesial Aspect

 Proximal aspect of maxillary central incisor is wedge shaped or triangular. Base of the triangle is at the cervix and the apex of the triangle is towards the incisal ridge.

 Labial outline: is convex and curves smoothly from the

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pg. 4

cervical line to incisal ridge

 Height of labial and lingual contour of the crown is at the cervical third.

 Mesial contact area is at the incisal third.

 A line which bisects the crown will bisect the root.

Distal Aspect

 Distal surface within the outline is similar to mesial surface except that the Curvature of cervical line is less in extent on distal surface than on mesial

surface. This feature is same for all other teeth.

 Distal contact area is at the junction of incisal and middle thirds of the crown

cervicoincisally and at the center labiolingually.

Incisal Aspect.

 From this aspect, the crown appears bulkier than other aspects.

Most of the labial surface is seen from this aspect, which is more convex cervically and flatter incisally

 The cingulum forms a smaller convex arc and the crown tapers rapidly from the labial surface towards the cingulum

 The mesiolabial and distolabial line angles are prominent from this aspect

 The incisal ridge/edge is at right angles to a line bisecting the tooth labiolingually

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pg. 5

ROOT Number

Permanent maxillary central incisor has single root.

. Form

 Root of central incisor is cone-shaped, tappering gradually from cervical line to apex

 Root surface is narrower on lingual aspect.

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Lec 5 Permanent Maxillary lateral incisors Dr.zainab mahmood

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Permanent maxillary lateral incisors

The maxillary permanent lateral incisor has close resemblance to maxillary permanent central incisor as it supplements the centrals in

function. It is smaller than the central incisor in all dimensions except root length,Maxillary lateral incisors vary in form more than any other tooth in the mouth except the third molar

Principal Identifying Features

1. The crown is more rounded, shorter and narrower mesio-distally than the maxillary central incisor.

2. It has a single root with a tapered, distally curved, pointed apex.

3. The lingual fossa is more concave than that of the maxillary central incisor.

4. this tooth may show considerable variance in its crown form; the root form may be more characteristic

Labial Aspect

 Trapezoid similar to labial aspect of maxillary permanent central incisor.

 Labial surface is about 2 mm narrower and 2 to 3 mm shorter than the maxillary permanent central incisor.

 It is more convex than that of maxillary permanent central incisor.

 Mesial outline of: is similar to that permanent maxillary central incisor except that mesioincisal angle is more rounded. Height of mesial contour is at the junction of middle and incisal thirds.

 Distal Outline: is shorter than mesial outline

 It is more rounded than found in permanent maxillary central incisor with more rounded distoincisal angle.

 The height of distal contour is at the center of the middle third.

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Lingual Aspect

•Trapezoid similar to the labial aspect.

. Marginal ridges are more prominent and stronger than found on central incisor

. Lingual fossa is deeper and well-circumscribed.

Cingulum is more prominent.

.There may be a deep developmental groove crossing the distal side of the cingulum extending on the root for a varying length. This groove is called as palatogingival groove.

.

The linguoincisal ridge is well developed

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Mesial Aspect: Triangle or wedge-shaped.

* Labial outline of permanent maxillary lateral incisor is less convex than labial outline of permanent maxillary central incisor with crest of

curvature at cervical third.

* Lingual outline is similar to that of central incisor.

* Cervical line shows marked curvature incisal.

* Incisal portion appears thicker than that of maxillary permanent central incisor as incisal ridge is heavily developed.

* Mesial contact area is at junction of the incisal and middle thirds.

*the labiolingual measurement of the crown and root is a millimeter or so less than that of the maxillary central incisor of the same mouth

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Distal Aspect:

 Triangle or wedge shaped similar to the mesial aspect.

 The curvature of cervical line on distal side is 1 mm less in extent than on mesial surface.

 The crown appears thicker from distal aspect.

 Palatogingival developmental groove may be seen on distal side of crown extending onto the root.

 Distal contact area is at the middle third.

Incisal Aspect

•• Triangularoutline of permanent maxillary lateral incisors resembles permanent maxillary central incisors from this aspect.

•• oval outline Some permanent maxillary lateral incisors resemble small maxillary permanent canines from incisal aspect. due to their prominent large cingulum and incisal ridges.

**All maxillary lateral incisors exhibit more convexity labially and lingually from the incisal aspect than do the maxillary central incisors.

•• Symmetry: A line bisecting the incisal ridge in mesiodistal direction is always straight and bisects the short arches representing mesial and distal contact areas.

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Root:

Permanent maxillary lateral incisor has single root.

•• Root tapers evenly from cervical line up to two-thirds of root length

•• Apical third of root usually shows distal curvature and the apex of maxillary permanent lateral incisor is usually pointed.

ANOMALIES

1. Congenitally missing laterals: Most common tooth to be missing next to 3rd molars

2. Peg shaped laterals: Small conical pointed crown.

3-One type of malformed maxillary lateral incisor has a large, pointed tubercle as part of the cingulum;

4- some have deep developmental grooves that extend down on the root lingually with a deep fold in the cingulum;

5- some show twisted roots

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Lec 6

دومحم بنيز د Permanent Mandibular incisors teeth

Common characteristics:

1. Mandibular incisors are the first permanent teeth to erupt.

2. They have smaller mesiodistal dimensions than all other teeth.

3. Among mandibular incisors, the lateral is larger than the central incisor.

4. The crowns of these teeth exhibit lingual inclination over the root.

5. These are the teeth that show very few developmental grooves and lines.

PERMANENT MANDIBULAR CENTRAL INCISOR

• Mandibular central incisors are the smallest teeth in the permanent dentition.

• The mandibular central incisors have their mesial surfaces in contact with each other just like their maxillary incisors.

• Mesial and distal incisal angles are sharp.

• Mesial and distal contact areas are at same level near mesial and distal incisal angles

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• Viewed incisally, the incisal ridge is perpendicular to the line bisecting the crown labiolingually.

Labial aspect:

trapezoidal

• Mesial and distal outlines taper evenly from mesioincisal and distoincisal angles to the narrow cervix.

• Heights of contour of mesial and distal outlines are at incisal third.

This places both the contact areas at the same level (incisal third of crown). Both angles are sharp and at right angles.

• The incisal ridge is straight and at right angles to the long axis of the crown.

• A newly erupted tooth shows mamelons on the incisal ridge.

• The cervical line on labial aspect is convex pointing apically.

• Labial surface is narrow and bilaterally symmetrical.

• The surface is smooth, convex in the cervical third and flattened in the incisal third.

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Lingual Aspect

: Trapezoidal

• The outline is similar to the labial aspect

• The lingual surface is narrower than the labial surface because of lingual convergence of the crown.

• The surface is smooth, flat in the incisal third and convex in the cervical portion near cingulum

• The marginal ridges are ill defined.

• The lingual fossa between marginal ridges and cingulum is a smooth shallow concavity devoid of developmental grooves.

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Mesial Aspect

: Triangular

• Labial outline: is straight except at the cervical third, where it is convex. Height of contour of labial outline is at the cervical third.

• Lingual outline is concave incisally and is convex in the cervical region. Its height of contour is at cervical third on the cingulum.

• In a tooth with occlusal wear, there is a flat incisal edge sloping labially. Incisal surface of mandibular incisors have a labial slope and occlude with lingually sloping incisal edges of the maxillary incisors during mastication.

• Cervical line on the mesial aspect shows a marked curvature towards incisal ridge.

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• The crown appears to be inclined lingually. The incisal ridge is placed lingual to a vertical line drawn through the center of the tooth

• The lingual inclination of crown is a feature mandibular teeth to facilitate normal overjet

• The mesial contact area is at incisal third of the crown.

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Distal Aspect

Distal aspect is similar to mesial aspect except that the extent of curvature of cervical line on distal aspect is 1 mm less than on the mesial

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Incisal Aspect

: oval labiolingually.

• Labiolingual dimension is always greater than mesiodistal

dimension. Bilateral symmetry of this tooth is easily appreciated from this aspect. From this aspect, more of labial surface is seen than of the lingual surface because of lingual inclination of the crown.

• The labial surface of crown at incisal third is convex, whereas the lingual surface of the crown at incisal third is concave.

• When viewed occlusally, incisal ridge is at the right angles to the line bisecting the crown labiolingually.

.

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ROOT Number

Single root.

Form

•• Developmental grooves are seen on both mesial and distal surfaces of root and the groove is deeper on the distal surface. The root has a pointed apex.

•• Apical third of root usually is straight sometimes, the root exhibits distal curvature.

Mandibular permanent lateral incisor:

Principal identifying features

1. Slightly larger than the mandibular central incisors.

2. The crown is slightly longer, but the root is considerably longer than the mandibular central incisors.

3. The mesial side of the crown is longer than the distal side, causing the incisal ridge to slope downward in a distal direction.

Labial aspect:

• The crown is not bilaterally symmetrical. Distal half of the crown is slightly larger

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• The mesiodistal width of crown is approximately 1 mm more than that of mandibular central incisor

• Mesioincisal angle forms a right angles but the distoincisal angle is more rounded

• Labial surface is smooth, convex cervically and flattened incisally.

Lingual aspect:

• Lingual surface is similar to that of mandibular central incisor but is wider mesiodistally.

• The crown tapers lingually making the lingual surface narrower than the labial surface.

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• The lingual surface is smooth devoid of developmental grooves, and is convex near cingulum.

• Lingual fossa is shallow and marginal ridges are relatively well- formed.

Mesial Aspect: triangular.

• Labial outline is convex near cervical line and is straight from up to incisal ridge.

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• Height of labial contour is at cervical third.

• Lingual outline is straight in the incisal third, slightly concave in middle third and is convex at cervical third. Height of contour on lingual outline is also at cervical third on the cingulum.

• Mesial contact area at the incisal third near to the incisal ridge.

Distal Aspect:

Distal aspect is similar to mesial aspect except the following features:

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•• Cervical line on distal surface is less curved.

•• Distal contact area is still within incisal third but is more cervically placed than the mesial contact area.

Incisal Aspect: oval labiolingually.

• Labiolingual dimension is greater than mesiodistal dimension.

• Unlike the mandibular centrals, the crown is not bilaterally symmetrical.

• The incisal aspect provides the identification feature of mandibular lateral incisor.

• The incisal ridge is at an angle to the line bisecting the tooth labiolingually rather than being perpendicular to it. This arrangement allows the incisal edge to follow the curvature of mandibular arch.

***** This characteristic feature of lateral incisor helps in differentiating it from similarly looking mandibular central incisor. The incisal ridge of the mandibular lateral incisor is at an angle with the labiolingual bisecting line, curves distally while in mandibular central incisal When viewed occlusally, incisal ridge is at the right angles to the line bisecting the crown labiolingually

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Root:

• Mandibular lateral incisor has a single root which resembles the mandibular central incisor root in every aspect but is considerably longer.

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Lec8 permanent maxillary premolars Dr. Huda Msaed

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Some characteristic features to all posterior teeth: those characteristics that differentiate posterior teeth from anterior teeth are as follows:

1. Greater relative faciolingual measurement as compared with the mesiodistal measurement.

2. Broader contact areas.

3. Contact areas nearly at the same level.

4. Less curvature of the cervical line mesially and distally.

5. Shorter crown cervico-occlusally when compared with anterior teeth.

PREMOLARS

There are eight permanent premolars; four in each dental arch and two in each quadrant.

The premolars are named so since they are located anterior to the molars in the permanent dentition.

1. The maxillary premolars have shorter crowns and shorter roots than those of the maxillary canines.

2. The maxillary first premolar is larger than the maxillary second premolar.

3. Premolars are named so because they are anterior to molars in permanent dentition. They succeed the deciduous molars (there are no premolars in deciduous dentition).

4. They are also called “bicuspid -having two cusps “, but this name is not widely used because the mandibular first premolar has one

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functional cusp and the mandibular 2nd premolar frequently has three cusps.

The premolars are intermediate between molars and canines in:

Form: The labial aspect of the canine and the buccal aspect of premolar are similar.

Function: The canine is used to tear food while the premolars and molars are used to grind it.

Position: The premolars are in the center of the dental arch.

Maxillary First Premolar

Principal identifying features:

1. The permanent maxillary 1st premolar has two cusps: buccal and lingua. The buccal cusp is longer than the lingual cusp by 1 mm.

2. Mesial slope of the buccal cusp is longer than the distal slope.

3. It has two roots. The bifurcation is at the middle third of the root.

Sometimes, it can have a single root with two pulp canals.

4. Developmental depression on the mesial surface of the crown extending to the root.

5. Central developmental groove interrupts the mesial marginal ridge.

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Buccal Aspect

From this aspect, the crown is roughly trapezoidal in shape.

1. The mesial outline of the crown is slightly concave from the cervical line to the mesial contact area.

2. The crest of curvature of the mesial contact area is occlusal to the center of the middle third.

3. The distal outline of the crown is straighter than that mesially.

4. The distal contact area has a broader curvature than that found mesially with its position slightly more occlusally. In spite of that, the contact areas are nearly at the same level with each other.

5. The mesial slope of the cusp is straight and longer than the distal slope, which is shorter and more curved.

6. Buccal surface of the crown is convex showing a strongly developed middle buccal lobe. The ridge which is continuous from the tip of the cusp to the cervical line is called the buccal ridge.

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Lingual Aspect:Trapezoidal like buccal aspect

1. The crown tapers toward the lingual because the lingual cusp is narrower than the buccal cusp.

2. The lingual cusp is smooth and spheroidal. The cusp tip is pointed with mesial and distal slopes meeting at a right (90^o) angle.

3. The mesial and distal outlines lingually are convex being continuous with the slopes of the lingual cusp.

4. The lingual cusp is shorter than the buccal cusp.

5. The apex of the lingual root of a two-root specimen tends to be more blunt than the buccal root apex.

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Mesial Aspect

1. The crown is roughly trapezoidal, with the longest uneven side is toward the cervical line, and the shortest is toward the occlusal portion.

2. Mesial surface shows both the cusps and the cusp tips are well within the confines of the root trunk.

3. The lingual cusp is shorter than the buccal cusp by 1 mm or more.

4. The buccal outline is convex and the crest of curvature is within the cervical third (near the junction between the cervical and middle thirds) and then become less convex till the cusp tip.

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5. The lingual outline is convex and the crest of curvature is within the middle third (near the center of the middle third).

6. The mesial marginal ridge is at the level of the junction of the middle and occlusal thirds and is crossed by the mesial developmental groove.

7. The root is bifurcated for half of its total length.

8. The mesial developmental depression starts from the contact area to the bifurcation area.

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Distal Aspect

The differences between distal and mesial aspects are:

1. The curvature of the cervical line is less distally than mesially.

2. There is no developmental groove crossing the distal marginal ridge.

3. There is no developmental depression.

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Occlusal Aspect

1. It resembles an unequal hexagon (six-sided figure). The buccal sides are equal, the mesial side is shorter than the distal side and the mesio- lingual side is shorter than the disto-lingual side.

2. The distal crest of curvature is buccal to the mesial crest of curvature.

3. The bucco-lingual dimension is much greater than the mesio-distal dimension.

4. The occlusal surface is circumscribed by the cusps and marginal ridges.

5. A central developmental groove divides the crown into buccal and lingual parts. It extends from near the distal marginal ridge to the mesial marginal ridge where it joins the mesial marginal developmental groove.

6. In the mesial and distal triangular fossae, there are two developmental grooves (mesio-buccal and disto-buccal grooves respectively) that join the central groove. The junctions of these grooves make the developmental pits (mesial and distal developmental pits respectively).

7. The lingual cusp is sharper and more pointed than the buccal cusp.

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Maxillary Second Premolar

Principal identifying features

1. The buccal and lingual cusps are equal in height.

2. The mesial slope of the buccal cusp is shorter than the distal slope.

3. The mesial surface has no developmental depression.

4. Has a single root.

5. The occlusal surface is more rounded or oval.

6. The central developmental groove is shorter and more irregular with more supplemental grooves on the occlusal surface.

7. There is no mesial groove crossing the mesial marginal ridge.

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Lec 9 Dental Anatomy

Mandibular Premolars Dr. Huda Msaed

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Mandibular first premolar

It is the smallest premolar in the human dentition. The mandibular 1st premolar shows resemblance to both of its neighboring teeth; the mandibular canine and 2nd premolar.

The features that resemble those of the mandibular canine are:

1. The buccal cusp is long and sharp. It is the only functional cusp.

2. The buccolingual measurement is similar to that of the canine 3. The occlusal surface slopes sharply lingually in a cervical direction 4. The mesiobuccal cusp ridge is shorter than the distobuccal cusp

ridge.

5. The outline form from the occlusal aspect resembles the incisal aspect of the mandibular canine.

The characteristics that resemble those of the second mandibular premolar are as follows:

1. The tooth has more than one cusp.

2. Viewed buccally, the crown and root form resemble that of the 2nd premolar

3. The contact areas, mesially and distally, are near the same level. This feature is common to all posteriors

4. The curvature of cervical line mesially and distally is similar.

Principal Identifying Features

1. Marked lingual inclination of the crown.

2. Two cusps: buccal and lingual; the buccal cusp is larger, and the lingual cusp is like a more developed cingulum.

3. Circular occlusal outline.

4. Single rounded root.

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Buccal Aspect:

1. The crown is roughly trapezoidal with a prominent middle buccal ridge, which continues from the cusp tip to the cervical line.

2. The mesial slope of the buccal cusp is shorter than the distal slop.

3. The contact areas mesially and distally are broad and at the same level.

4. The mesial and distal outlines from the cervical line to the crest of curvature are slightly concave.

5. The tip of the buccal cusp is sharp and located mesial to the long axis of the crown.

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The Lingual Aspect

1. The crown and the root taper lingually, and the occlusal surface inclines greatly cervically.

2. The lingual cusp is poorly developed but pointed.

3. There is a developmental groove named” mesiolingual developmental groove”, which divides the lingual cusp into the mesiobuccal and lingual lobes.

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The Mesial Aspect

1. The tip of the buccal cusp nearly reaches the center of the root.

2. The buccal outline is much curved, and the crest of curvature is near the middle third of the crown.

3. The lingual outline is less curved than the buccal outline, with the crest of curvature at the center of the middle third.

4. The height of the lingual cusp is two-thirds the height of the buccal cusp from the cervical line to the tip of the cusp.

5. The surface of the crown mesially is smooth except for the presence of the mesio-lingual developmental groove.

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The Distal Aspect

The distal aspect of the mandibular first premolar differs from the mesial aspect in the following points:

1. There is no developmental groove in the distal aspect.

2. The distal marginal ridge is higher than the mesial marginal ridge, with less inclination lingually.

3. The curvature of the cervical line distally is nil.

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The Occlusal Aspect:

1. Buccal cusp is larger making the major bulk of the crown and the lingual cusp is much smaller. The crown converges sharply towards lingual surface.

2. The mesio-buccal and disto-buccal line angles are rounded and prominent.

3. The crown converges sharply to the center of the lingual surface.

4. Mandibular 1st premolar has two fossae: The mesial and the distal

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Lec 10 Dental Anatomy Dr. Huda Msaed

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Permanent mandibular second premolar:

Principal identifying features:

1. It is larger than the mandibular first premolar.

2. The cusps are more equal in size with less pointed tips. Usually this tooth has three cusps, one buccal and two lingual; or may have only two cusps, one buccal and one lingual.

3. The occlusal outline is almost square in appearance with no mesio-lingual developmental groove.

There are two common forms of mandibular 2nd premolar:

1. three cusp form (‘Y’ groove pattern) Frequently seen 2. Two cusp form (‘U’ and ‘H’ groove pattern).

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Buccal Aspect: Geometric shape: Trapezoidal

1. The buccal cusp is shorter and less pointed than that of mandibular first premolar.

2. The contact areas are broad and high (appear to be higher because of the shorter buccal cusp).

3. The root is broader mesio-distally than that of mandibular first premolar ending with a blunter apex.

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Lingual Aspect

The lingual surface of the crown is smooth and spheroidal.

From this aspect, this tooth differs from the mandibular first premolar in:

1. The lingual cusps are more developed than mandibular first premolar.

2. Less occlusal surface may be seen. However, because the lingual cusps are slightly shorter than the buccal cusp, we can see part of the lingual incline of the buccal cusp from this aspect.

3. A. In the three cusps type: there are two lingual cusps, the mesio-lingual is larger than the disto-lingual cusp and divided by the lingual developmental groove.

B. In the two cusps type: there is a large cusp of the same height as in the three cusps type. There is a developmental depression disto- lingually where the lingual cusp ridge joins the distal marginal ridge.

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Mesial Aspect: Mesial contact area: It is at the middle third of the crown and centered buccolingually.

From this aspect, this tooth differs from the mandibular first premolar in:

1. The crown and the root are wider bucco-lingully.

2. The buccal cusp is not nearly centered over the root trunk, and it is shorter.

3. The marginal ridge is at a right angle to the long axis of the tooth with less occlusal surface may be seen.

4. There is no mesio-lingual developmental groove on the crown.

5. The root is longer with blunt apex.

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Distal aspect:

1. More of occlusal surface can be seen than from mesial aspect, as distal marginal ridge is at a lower level.

2. Distal contact area is at the same level as the mesial contact area.

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Occlusal Aspect

A. Three cusps type:

1. The occlusal aspect is square in shape.

2. Three cusps: the buccal is the largest, followed by the mesio- lingual cusp, and then the distolingual cusp.

3. Each cusp has a well-formed triangular ridge separated by deep developmental grooves which form a Y-shape on the occlusal surface.

4. There are three developmental grooves:

A. Mesial developmental groove ending in the mesial triangular fossa.

B. Distal developmental groove ending in the distal triangular fossa.

C. Lingual developmental groove separating the two lingual cusps.

5. These grooves converge in a central pit, which is placed slightly towards the distal side.

6. Supplemental grooves are often seen.