9 Tooth Morphology

Dental Arches Dentition: arranged in two arches Maxillary arch-upper Mandibular arch-lower Each arch has identical number of teeth Maxillary teeth slightly overlap mandibular Dentition refers to natural teeth in position. The maxillary arch is the upper arch of teeth set in the maxilla bone and the mandibular arch is the lower arch located in the mandible bone. Although each arch has the same number of teeth, the mandibular arch is movable while the maxillary arch remains fixed to the skull. The teeth of the mandibular joint are slightly overlapped by the teeth of the maxillary arch.

Dental Quadrants Maxillary right quadrant Maxillary left quadrant Mandibular right quadrant Mandibular left quadrant (A) Primary dentition The midline is an imaginary line that divides each of the dental arches into two sections, called quadrants.

Dental Quadrants Maxillary right quadrant Maxillary left quadrant Mandibular right quadrant Mandibular left quadrant (B) Permanent dentition The midline is an imaginary line which divides each of the dental arches into two sections, called quadrants. Each of the four quadrants contain eight permanent teeth and are labeled right or left.

Types of Teeth and Their Functions Primary teeth (deciduous) Total of 20 Permanent teeth Total of 32 Known as deciduous, the primary teeth total 20; 10 in each arch, 5 in each quadrant. Adults have 32 permanent teeth: 16 in each arch and 8 in each quadrant.

Primary Teeth Central incisor Lateral incisor Canine Molars Cuspid First and second The central incisor is the first tooth starting from the midline in each quadrant. The purpose of the incisor is to cut or bite food. The second tooth from the midline is called the lateral incisor and is used for cutting. The canine is the third tooth from the midline and its bulkiness aids in tearing food. There are two molars in each quadrant named the first and second molars. Molars are used to chew food.

Primary Teeth Central incisor Lateral incisor Canine First molar Second molar Second molar First molar Canine Lateral incisor Central incisor

Permanent Teeth Central incisor Lateral incisor Canine Premolars or bicuspids First and second Molars First, second, and third In our lifetime we will receive two sets of teeth: the primary teeth and permanent teeth. Primary teeth are replaced by permanent teeth usually between the ages of six and seventeen. The arrangement is similar; however, there is an addition of first and second premolars in the permanent set, often called bicuspids because they have two pointed or rounded mounds on the crowns to pulverize food. Also, each quadrant contains an additional molar, the third molar, commonly referred to as “wisdom teeth.”

Eruption Schedule Primary dentition (6 months to 3 years) All twenty teeth should have erupted Mixed dentition (6 to 12 years) Period when both primary and permanent teeth are present Permanent dentition (by age 17) All adult teeth should have erupted At approximately six months, the first of the primary teeth erupt and continue until about 3 years of age. Mixed dentition refers to the period in which both primary and permanent teeth are in position, usually from six to twelve years old. The permanent dentition should be in place by age 17.

Divisions of the Tooth Crown Anatomical Clinical Clinical crown The two basic parts of the tooth are the crown and root. The crown may either be described as the anatomical crown (the portion of the crown covered by enamel) and the clinical crown (the portion of the crown visible in the mouth).

Divisions of the Tooth Root Anatomical Clinical The root is also identified into anatomical and clinical terms. The anatomical root is that which is covered by enamel. The clinical root is that which can be seen in the oral cavity. The cervical line divides the crown and the root where the anatomical crown and root join together.

Surfaces of the Teeth Anterior teeth Mesial Distal Labial Lingual Incisal edge The crowns of all teeth have five surfaces. The mesial is the surface toward the midline. The distal is the surface away from the midline. The labial is the outside surface toward the lips. The lingual is the inside surface toward the tongue that is also referred to as the palatal surface in the maxillary arch. The incisal edge is the biting or cutting edge. Facial describes either the labial surface of the anterior teeth or the buccal surface of the posterior teeth.

Surfaces of the Teeth Posterior teeth Mesial Distal Lingual Buccal Occlusal The surfaces of the posterior teeth are the mesial, distal, lingual, buccal, and occlusal. Mesial surface is toward the midline. Distal surface is away from the midline. Lingual is the inside surface, toward the tongue. Buccal is the outside surface toward the cheek and is also referred to as the facial surface. Occlusal surface is used for pulverizing and chewing.

Teeth Surface Flat Convex: bulging or curved outward Concave: recessed or indented HINT: “cave” is hollow and not bulging outward Tooth surfaces are all flat, convex, or concave. The surfaces of the posterior teeth are either flat, convex (bulging or curved), or concave (recessed or indented).

Teeth Surface Section of the tooth crown Incisal-third Occlusal-third Middle-third The crown of the tooth is divided into three sections. The incisal-third is the area nearest the incisal edge of the anterior. The occlusal-third is the occlusal surface of the posterior tooth. The area between the incisal-third and cervical-third is the middle-third.

Teeth Surface Contact area Area where proximal sides of two teeth come together and touch Usually mesial of one tooth and distal of another Where the proximal sides of two teeth come together and touch is called the contact area. Normally the mesial of one tooth and the distal of another, called the contact area, is between two incisors.

Teeth Surface Embrasure Triangular space in gingival direction Occurs when two adjoining teeth are contacting The triangular space in the gingival direction is called the embrasure.

Anatomical Structures Apex Apical foramen Apex Apical foramen Located in the root, the apex is at or near the end. The apical foramen is the opening in the end of the tooth where nerve and blood vessels enter. There may be more than one apical foramen in a tooth.

Anatomical Structures Bifurcated Buccal groove Mesial Distal Mandibular first molar Buccal groove A tooth with two roots is termed as bifurcated, or branched in two. The buccal groove is the depression that forms a groove which extends from the middle of the buccal surface to the occlusal surface.

Anatomical Structures Cingulum Lingual surface of maxillary central incisor Cingulum The cingulum is the convex area on the lingual surface of anterior teeth. It is located near the gingiva. Distal Mesial

Anatomical Structures Cusp Cusp of Carabelli Distal Mesial Maxillary first molar Lingual Cusp of Carabelli The cusp is the pointed or rounded mound on the tooth’s crown. The fifth cusp located on the mesial lingual surface of most maxillary first molars is called the Cusp of Carabelli.

Anatomical Structures Developmental groove A groove formed by uniting lobes during development of the crown of the tooth is the developmental groove.

Anatomical Structures Fissure Mandibular second premolar Fissure A fissure is the developmental groove that has an imperfect union where the lobes come together. Decay often initiates in the fissure.

Anatomical Structures Fossa Maxillary canine Lingual Distal Mesial The fossa is the shallow, rounded, and angular depression of the tooth. Distolingual fossa Mesiolingual fossa

Anatomical Structures Furcation Mandibular first molar Buccal view Furcation x The dividing point of a multirooted tooth is the furcation.

Anatomical Structures Lobes Mamelons Lobes are separate divisions that come together to form a tooth and often become cusps in molars. The three bulges on the incisal edge of newly erupted central incisor are called mamelons and normally disappear with normal wear and tear.

Anatomical Structures Marginal ridges Distal Mesial Distal marginal ridges The marginal ridges are elevated areas of enamel that forms the mesial and distal borders. In the anterior teeth they are on the lingual surface and on posterior teeth they are located on the occlusal surface.

Anatomical Structures Oblique ridge Oblique ridge Oblique ridges extend obliquely across the occlusal. They are elevated areas of enamel.

Anatomical Structures Pit Pits Grooves come together or the fissures cross at the pit. Decay often begins here.

Anatomical Structures Ridge Supplemental groove The ridge is the linear elevation of enamel and the supplemental groove is the shallow, linear groove that radiates from the developmental groove.

Anatomical Structures Transverse ridge A single ridge of elevation across the occlusal surface is create at the union of two triangular ridges called the transverse ridge. Transverse ridge

Anatomical Structures Triangular ridge Lingual triangular ridge Lingual Buccal The ridge of elevation that descends from cusp and widens as it runs down is called the triangular ridge.

Anatomical Structures Trifurcated Where three roots come from the main trunk of the tooth is called trifurcated.

Permanent Teeth Descriptions Maxillary central incisor First tooth closest to the midline Important for appearance Speech Mamelons Imbrication lines The first tooth closest to the midline is called the maxillary central incisor. It is very important to the physical appearance of an individual as well as the person’s speech.

Permanent Teeth Descriptions Maxillary centrals Labial Mesial Lingual Distal Incisal L F D M The first tooth closest to the midline is called the maxillary central incisor. It is very important to the physical appearance of an individual as well as the person’s speech.

Permanent Teeth Descriptions Maxillary lateral incisor Second tooth from the midline Smallest in maxillary arch Anomalies Peg lateral Agenesis The second tooth from the midline and the smallest in the maxillary arch is called the maxillary lateral incisor. It’s crown and root are smaller than the maxillary central incisor. The maxillary lateral incisors has anomalies such as the peg lateral, a diminutive peg-shaped crown with a smooth surface, and the agenesis, which occurs when tooth buds do not form leaving the roots curve in unusual ways and creating distorted crowns.

Permanent Teeth Descriptions Maxillary lateral incisors Labial Mesial Lingual Distal Incisal L F D M The second tooth from the midline and the smallest in the maxillary arch is called the maxillary lateral incisor. It’s crown and root are smaller than the maxillary central incisor. The maxillary lateral incisors has anomalies such as the peg lateral, a diminutive peg-shaped crown with a smooth surface, and the agenesis, which occurs when tooth buds do not form leaving the roots curve in unusual ways and creating distorted crowns.

Permanent Teeth Descriptions Maxillary canine (cuspid) Third tooth from the midline Cornerstone of the mouth Most stable tooth as the root is the longest in maxillary arch The root of the maxillary canine is the longest in the maxillary arch, making it the most stable. It is the third tooth from the midline and is termed as the “cornerstone of the mouth” as it is located between the incisors and bicuspids. Its crown is convex on the facial surface.

Permanent Teeth Descriptions Maxillary canines (cuspids) Labial Mesial Lingual Distal Incisal L F D M

Permanent Teeth Descriptions Maxillary first premolar (bicuspid) Much longer and wider Prominent There are two premolars in each quadrant. The maxillary first premolar is longer and wider.

Permanent Teeth Descriptions Maxillary first premolars (bicuspids) Buccal Mesial Lingual Distal Occlusal L B D M

Permanent Teeth Descriptions Maxillary second premolar (bicuspid) Maxillary second premolars (bicuspids) Buccal Mesial Lingual Distal Occlusal L B D M There are several differences between the maxillary second premolar and the first. In the maxillary second premolar the cusps of the maxillary are more equal in length, the lingual cusp is slightly shorter, the mesial cusp slope is shorter, there is only one root and one root canal, there is a slight depression on the mesial root, and the crowns of the first and second bicuspids are wider.

Permanent Teeth Descriptions Maxillary first molar “six-year molar” Buccal groove Divide mesiobuccal and the disto-buccal cusps Buccal pit Depression where crown ends Lingual pit Shallow depression halfway down The first permanent tooth to erupt is the maxillary first molar and referred to as the “six-year molar.” The fifth cusp, called the cusp of Carabelli, is located on the meso-lingual.

Permanent Teeth Descriptions Maxillary first molars Buccal Mesial Lingual Distal Occlusal L B D M

Permanent Teeth Descriptions Maxillary second molar “Twelve-year molar” Four cusps Referred to as the “twelve-year molars,” the maxillary second molars are similar to the maxillary first molars, but the crown and root are smaller.

Permanent Teeth Descriptions Maxillary third molar “Wisdom tooth” Many do not develop The maxillary third molars are called wisdom teeth because it is believed that a person has become mature by the time they erupt. Many individuals do not develop third molars and those who do often require surgery to remove them due to insufficient space in the oral cavity.

Permanent Teeth Descriptions Maxillary third molars Buccal Mesial Lingual Distal Occlusal L B D M The maxillary third molars are called wisdom teeth because it is believed that a person has become mature by the time they erupt. Many individuals do not develop third molars and those who do often require surgery to remove them due to insufficient space in the oral cavity.

Permanent Teeth Descriptions Mandibular central incisor Least variable tooth Smallest tooth in dentition Mandibular central incisors Labial Mesial Lingual Distal Incisal L F D M The mandibular central incisor is the least variable tooth in the mouth, as well as the smallest in its dentition.

Permanent Teeth Descriptions Mandibular lateral incisor Mandibular lateral incisors Labial Mesial Lingual Distal Incisal L F D M The mandibular lateral incisor resembles the central incisor, yet slightly larger. Its root is also slightly longer.

Permanent Teeth Descriptions Mandibular canine (cuspid) Mandibular canines (cuspids) Labial Mesial Lingual Distal Incisal L F D M The mandibular canine is also called the cuspid. It is the third tooth from the midline and resembles the maxillary canine but less developed. Its root is generally shorter and cusp is not as sharp.

Permanent Teeth Descriptions Mandibular first premolar (bicuspid) Mandibular first premolars (bicuspids) Buccal Mesial Lingual Distal Occlusal L B D M The mandibular first premolar looks more like a mandibular canine.

Permanent Teeth Descriptions Mandibular second premolar (bicuspid) Mandibular second premolars (bicuspids) Buccal Mesial Lingual Distal Occlusal L B D M The mandibular second premolar is longer and wider than the mandibular first premolar. Its lingual cusps are more developed with two or three functioning cusps.

Permanent Teeth Descriptions Mandibular first molar Mandibular first molars Buccal Mesial Lingual Distal Occlusal L B D M Referred to as the “six-year molar” the mandibular first molar normally erupts before the maxillary first molar and believed to be the keystone of the dental arch. It has the widest crown of any tooth and is the largest mandibular tooth. The six-year molar has five functioning cusps normally and two roots.

Permanent Teeth Descriptions Mandibular second molar Maxillary second molars Buccal Mesial Lingual Distal Occlusal L B D M The mandibular second molar is smaller in size than the mandibular first molar. It has four cusps and its two roots are normally shorter than the first molar’s, however they are closer together and sometimes fused.

Permanent Teeth Descriptions Mandibular third molar Maxillary first premolars (bicuspids) Buccal Mesial Lingual Distal Occlusal L B D M The mandibular third molars (also referred to as wisdom teeth) often develop improperly. It has a wrinkled surface and its roots (often four or more) are often fused and tend to angle almost horizontally toward the distal.

Deciduous Teeth Descriptions (Primary or Baby Teeth) Central incisor Lateral incisor Canine First molar Second molar There are twenty deciduous teeth in the primary dentition. Each quadrant contains a central incisor, a lateral incisor, a canine, first and second molar. There are no bicuspids. Second molar First molar Canine Lateral incisor Central incisor

Deciduous Teeth Descriptions (Primary or Baby Teeth) Maxillary deciduous central incisor Resembles the permanent maxillary central in shape Much smaller Erupts with no mamelons Surface is convex and smooth The maxillary deciduous central incisor resembles the permanent maxillary central in shape but is much smaller. It erupts with no mamelons and its surface is convex and smooth.

Deciduous Teeth Descriptions (Primary or Baby Teeth)

Deciduous Teeth Descriptions (Primary or Baby Teeth) Maxillary deciduous lateral incisor Similar to the central incisor except smaller More rounded on the mesial and distal sides The maxillary deciduous lateral incisor is similar to the central incisor but even smaller. It is more rounded on the mesial and distal sides.

Deciduous Teeth Descriptions (Primary or Baby Teeth)

Deciduous Teeth Descriptions (Primary or Baby Teeth) Maxillary deciduous canine (cuspid) More convex than permanent tooth The maxillary deciduous canine is more convex than the permanent version. The maxillary deciduous first molar is very similar to the permanent bicuspid, and the maxillary deciduous second molar has four primary cusps like the permanent tooth.

Deciduous Teeth Descriptions (Primary or Baby Teeth)

Deciduous Teeth Descriptions (Primary or Baby Teeth) Maxillary deciduous canine (cuspid) More convex than permanent tooth The maxillary deciduous canine is more convex than the permanent version. The maxillary deciduous first molar is very similar to the permanent bicuspid and the maxillary deciduous second molar has four primary cusps like the permanent tooth.

Deciduous Teeth Descriptions (Primary or Baby Teeth) The maxillary deciduous first molar is very similar to the permanent bicuspid.

Deciduous Teeth Descriptions (Primary or Baby Teeth) Maxillary deciduous second molar Four primary cusps like permanent tooth The maxillary deciduous second molar has four primary cusps like the permanent tooth.

Deciduous Teeth Descriptions (Primary or Baby Teeth)

Deciduous Teeth Descriptions (Primary or Baby Teeth) Mandibular deciduous central incisor More closely resembles mandibular lateral incisor Shape is almost identical to permanent lateral Root is slender rather than long Mesial and distal surfaces of root are flat Lingual and labial surfaces are convex The mandibular deciduous central incisor more closely resembles the mandibular lateral incisor than the central incisor counterpart. Its shape is almost identical to permanent lateral and the root is slender rather than long. The mesial and distal surfaces of root are flat, whereas lingual and labial surfaces are convex.

Deciduous Teeth Descriptions (Primary or Baby Teeth)

Deciduous Teeth Descriptions (Primary or Baby Teeth) Mandibular deciduous lateral incisor Same as mandibular deciduous central incisor except that it is slightly longer and wider The mandibular deciduous lateral incisor is smaller than the mandibular deciduous central incisor and is longer and wider. The pointed incisal edge of the mandibular deciduous canine distinguishes it from the other teeth.

Deciduous Teeth Descriptions (Primary or Baby Teeth)

Deciduous Teeth Descriptions (Primary or Baby Teeth) Mandibular deciduous canine (cuspid) Delicate in form Mesial and distal marginal ridges are less pronounced than those of the maxillary The maxillary deciduous canine is more delicate than the maxillary deciduous cuspid. The root is not large or long, the cingulum and distal and mesial margins are less pronounced, the mesial-incisal slope is not as long as the distoincisal slope, and the maxillary incisal slope are nearly equal in length.

Deciduous Teeth Descriptions (Primary or Baby Teeth)

Deciduous Teeth Descriptions (Primary or Baby Teeth) Mandibular deciduous first molar Does not resemble any other permanent or deciduous tooth Four cusps Two roots The mandibular first molar has four cusps and two roots. It is like no other tooth.

Deciduous Teeth Descriptions (Primary or Baby Teeth)

Deciduous Teeth Descriptions (Primary or Baby Teeth) Mandibular deciduous second molar Resembles the permanent mandibular first molar but smaller in all dimensions The mandibular deciduous second molar is similar in appearance to the mandibular first molar but smaller.

Deciduous Teeth Descriptions (Primary or Baby Teeth)