¶ Chapter 4 — DENTAL (TOOTH) ANATOMY
Reference Edition
This chapter is part of the Air Force Dental Laboratory Manual (2005) – Digitally Restored Edition.
This edition preserves the original publication while correcting OCR errors, restoring formatting, reconstructing damaged tables where necessary, and improving digital readability.
The technical content has not been rewritten, modernized, expanded, or altered.
It is provided as a professional reference. Modern instructional material is published separately throughout DentalTechnology.org.
¶ Section 4A — How Teeth are Identified
¶ 4.1. Groups of Teeth
Teeth, as they exist in the mouth, can be placed into one of three broad groupings; maxillary or mandibular, right or left, or anteriors or posteriors. These groupings, detailed below, apply to both the natural dentition and artificial teeth.
4.1.1. Maxillary or Mandibular. Each person has two jaws, a maxillary (upper) and a mandibular (lower). The teeth in these jaws are called either maxillary or mandibular teeth. The combination of natural teeth and supporting alveolar bone found in an upper or a lower jaw is called a dental arch. When natural teeth are extracted, the healed alveolar process is called the alveolar ridge. Artificial teeth are set over alveolar ridges so they coincide with the original arch form.
4.1.2. Right or Left. If the two dental arches are split down the midline from front to back, the arches can be divided into upper and lower right sections and upper and lower left sections. Because one of these sections represents one-fourth of the upper and lower arches taken together, each section is called a quadrant (Figure 4.1). If a tooth is located to the left of the midline in the upper arch, the tooth is part of the maxillary left quadrant (and so forth).
Figure 4.1. Mandibular Right Quadrant.
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Right
Quadrant
4.1.3. Anteriors or Posteriors.
4.1.3.1. Teeth can also be classified as anteriors (incisors and canines) or posteriors (premolars and molars) (Figure 4.2)
A complete adult natural dentition has 32 teeth, and each arch contains 16.
4.1.3.2. The teeth in an arch are composed of six anteriors (canine to canine) and ten posteriors (all teeth distal to the canines)
There are three anteriors and five posteriors in a quadrant. NOTE: Complete dentures for the upper and lower arches usually consist of 28 teeth. The third molars (4) are not used.
Figure 4.2. Anterior and Posterior Teeth.
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ANTERIOR TEETH
POSTERIOR TEETH
¶ 4.2. Names of Teeth
See Figure 4.3 and the subparagraphs herein for the names of groups of teeth.
Figure 4.3. Names of Teeth (Groups).
4.2.1. Anteriors.
4.2.1.1. Central and Lateral Incisors. The word “incisor” describes the function of incising or cutting food. In each quadrant, the two teeth nearest the midline of the dental arches are called incisors. The first incisor on either side of the midline is called a central incisor. The second incisor from the midline of either arch is called a lateral incisor.
4.2.1.2. Canines. In each quadrant, the third tooth nearest the midline of the dental arches is called a canine. These teeth are used to tear food, and each dental arch has two canines. A canine is sometimes called a cuspid because its cutting edge is a single, pointed elevation or cusp.
4.2.2. Posteriors.
4.2.2.1. Premolars. Premolars are so named because they occupy an anatomical position mesial to the molars. (They are sometimes called bicuspids because most have two cusps on their chewing surfaces.) There are eight premolars, two in each quadrant, which function as seizing and grinding teeth. The two premolars in any given quadrant are further called first and second premolars, the first located immediately behind the canine.
4.2.2.2. Molars. Molars, the largest teeth in the dental arches, lie directly behind the premolars and function as grinders during mastication (chewing). Under normal conditions, there are six molars in each arch (three in each quadrant). They are called first, second, and third molars. The first molar is the first tooth distal to the second premolar.
¶ 4.3. Number Substitutes for Teeth Names
Formal descriptions like “maxillary right molar” and “mandibular left lateral incisor” can be time-consuming when many people must be examined in a short time. They can also be too lengthy when space on forms is limited. Therefore, numerical shorthand is often used as a substitute for complete, formal tooth names. See Figure 4.4 (and paragraphs 4.3.1 and 4.3.2) for number substitutes 1 through 32 for the full complement of natural teeth.
4.3.1. Numbers 1 through 16 are in the maxillary arch. The upper right third molar is number 1, the upper right second molar is number 2, and as you proceed in consecutive order around the maxillary arch to the upper left third molar, the last number is 16.
4.3.2. Numbers 17 through 32 are in the mandibular arch. The lower left third molar is number 17; the lower left second molar is number 18; and, as you proceed around the mandibular arch to the lower right third molar, the last number is 32.
¶ 4.4. Structures of the Teeth
4.4.1. A tooth is divided into two parts, the crown and the root (Figure 4.5)
The anatomical crown is the part of the tooth covered with enamel. The root of a tooth is embedded in alveolar bone and covered with cementum. NOTE: In young people, areas of the anatomical crown are frequently buried in gingival tissue. As a person gets older it becomes common for a tooth’s enamel to be completely exposed above the gingiva and to have root surface showing.
4.4.2. The term clinical crown is applied to the part of the tooth that is visible above the gingiva to include root surface. The bulk of a tooth is composed of a bone-like substance called dentin that is covered by enamel to form the crown and cementum to form the root. The line of division between the crown and root is called the cervical line or cementoenamel junction. The dividing line is found in a somewhat constricted region on the tooth’s surface called the cervix or neck.
4.4.3. The tip of the root is known as the apex. The tooth contains an aggregate of blood vessels, nerves, and cellular connective tissue called the dental pulp, which is housed within a pulp chamber and root canal of a tooth.
Figure 4.4. Number Substitutes for Teeth Names.
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RIGHT MAXILLARY THIRD MOLAR.
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RIGHT MAXILLARY SECOND MOLAR.
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RIGHT MAXILLARY FIRST MOLAR.
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RIGHT MAXILLARY SECOND PREMOLAR.
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RIGHT MAXILLARY FIRST PREMOLAR.
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RIGHT MAXILLARY CANINE.
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RIGHT MAXILLARY LATERAL INCISOR.
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RIGHT MAXILLARY CENTRAL INCISOR.
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LEFT MAXILLARY CENTRAL INCISOR.
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LEFT MAXILLARY LATERAL INCISOR.
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LEFT MAXILLARY CANINE.
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LEFT MAXILLARY FIRST PREMOLAR
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LEFT MAXILLARY SECOND PREMOLAR
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LEFT MAXILLARY FIRST MOLAR.
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LEFT MAXILLARY SECOND MOLAR.
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LEFT MAXILLARY THIRD MOLAR.
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LEFT MANDIBULAR THIRD MOLAR.
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LEFT MANDIBULAR SECOND MOLAR.
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LEFT MANDIBULAR FIRST MOLAR.
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LEFT MANDIBULAR SECOND PREMOLAR.
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LEFT MANDIBULAR FIRST PREMOLAR.
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LEFT MANDIBULAR CANINE.
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LEFT MANDIBULAR LATERAL INCISOR.
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LEFT MANDIBULAR CENTRAL INCISOR.
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RIGHT MANDIBULAR CENTRAL INCISOR.
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RIGHT MANDIBULAR LATERAL INCISOR.
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RIGHT MANDIBULAR CANINE.
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RIGHT MANDIBULAR FIRST PREMOLAR.
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RIGHT MANDIBULAR SECOND PREMOLAR.
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RIGHT MANDIBULAR FIRST MOLAR.
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RIGHT MANDIBULAR SECOND MOLAR.
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RIGHT MANDIBULAR THIRD MOLAR.
4.4.4. Anterior teeth ordinarily have one root canal; multiple canals occur in posterior teeth. The nerves and blood vessels enter and leave the tooth through an opening called the apical foramen at or near the apex of the root.
Figure 4.5. Structures of Teeth and Supporting Tissues.
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ANATOMICAL CROWN
CLINICAL CROWN
GINGIVAL
CREST
GINGIVA
CERVICAL LINE
SUBMUCOSA
ROOT
APICAL FORAMEN
ENAMEL
DENTIN
PULPAL HORNS
PULP CHAMBER
ROOT CANALS
PERIODONTAL LIGAMENT
ALVEOLAR BONE
CEMENTUM
¶ 4.5. Supporting Structures of the Teeth
The supporting tissues of the teeth are collectively called the periodontium. The periodontium consists of the alveolar process of the maxillae and mandible, periodontal ligament, cementum of the tooth, and gingiva, as follows:
4.5.1. Alveolar Process.
4.5.1.1. The alveolar process is the portion of the maxillae or mandible in which the roots of the teeth are embedded and by which tooth roots are supported. An alveolar process consists of three kinds of bone; the outer cortical plate, lamina dura, and spongy bone.
4.5.1.2. The outer cortical plate is a compact layer of bone on the bone’s surface. The lamina dura is a thin, dense layer of bone that lines tooth sockets and is a specialized continuation of the cortical plate. The spongy bone is the less dense, cancellous bone representing central mass of the alveolar process.
4.5.2. Periodontal Ligament. The periodontal ligament is a thin, fibrous ligament connecting a tooth to the lamina dura of the bony socket. Normally, teeth do not contact the bone directly; a tooth is suspended in its socket by the fibers of the ligament. This arrangement allows each tooth limited individual movement. The fibers act as shock absorbers to cushion the force of chewing impacts.
4.5.3. Cementum. The cementum is the only tissue considered as both a basic part of the tooth and a component of the periodontium. Formed during the development of the tooth’s root, cementum is a thin, calcified layer of tissue that completely covers the root’s dentin. It functions as an area of attachment for periodontal ligament fibers.
4.5.4. Gingiva. The gingiva is the specialized mucous membrane covering the alveolar processes and encircling the necks of the teeth (Figure 4.6). It aids in the support of the teeth and protects the alveolar process and periodontal ligament from bacterial invasion. Healthy gingiva is pale pink, firm, and resilient. It is divided into two types, free and attached gingiva.
Figure 4.6. Free and Attached Gingiva.
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GINGIVAL SULCUS
GINGIVAL LINE
FREE MARGINAL GINGIVA
ATTACHED GINGIVA
MUCOGINGIVAL JUNCTION
ALVEOLAR MUCOSA
EPITHELIAL ATTACHMENT
GINGIVAL SULCUS
LAMINA DURA
SPONGY BONE
LINGUAL CORTICAL PLATE
4.5.4.1. Free gingiva is “free” to the extent that it can be displaced. That is, it is not tightly bound to anything underneath it. Free gingiva extends from the gingival crest to the bottom of the gingival sulcus. At the bottom of the sulcus, an epithelial attachment joins the free gingiva to the tooth surface. The interdental papilla is the portion of the free gingiva that fills the proximal space below the contact areas of adjacent teeth. It helps prevent food from packing between the teeth.
4.5.4.2. Attached gingiva covers the labial cortical plate of the alveolar process. It is firmly fixed to underlying bone.
¶ 4.6. Crown Morphology (Contours)
There are almost no perfectly flat or perfectly straight surfaces; most surfaces are curved. The contour of a crown is a combination of convex and concave curves. A convex surface is one that is curved outward; a concave surface is curved inward.
¶ 4.7. Tooth Surfaces
4.7.1. Proximal. A tooth has two proximal surfaces, one oriented toward the midline of the dental arch and another oriented away from the midline of the arch (Figure 4.7). The mesial is the proximal surface closest to the midline of the arch. The distal is the proximal surface oriented away from the midline of the arch.
Figure 4.7. Tooth Surfaces.
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FACIAL SURFACES
LINGUAL SURFACES
INCISAL EDGE
OCCLUSAL SURFACE
MESIAL SURFACE
DISTAL SURFACE
MEDIAN LINE
4.7.2. Facial. The facial is the surface of a tooth that “faces” toward the lips or cheeks (Figure 4.7). When there is a requirement to be more specific, terms like labial and buccal are used. The labial is the surface of an anterior tooth that faces toward the lips. The buccal is the surface of a posterior tooth that faces toward the cheek.
4.7.3. Lingual. The lingual is the surface of a tooth facing toward the tongue.
4.7.4. Incisal. The incisal is the cutting edge of an anterior tooth.
4.7.5. Occlusal. The occlusal is the chewing surface of a posterior tooth.
4.7.6. Long Axis and Axial Surface. The long axis of a tooth is an imaginary line that goes through the crown and root around which the substance of a tooth is most symmetrically distributed (Figure 4.8). Any surface of a tooth that is parallel to the long axis is called an axial surface (for example, mesial, distal, facial, or lingual surfaces).
Figure 4.8. Long Axis.
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LONG AXIS
4.7.7. Dividing a Crown Into Thirds. The facial, lingual, mesial, and distal surfaces of a crown can be divided into thirds, both horizontally and longitudinally, as follows:
4.7.7.1. Horizontal Division. Each axial surface of a crown is divided horizontally into a cervical, a middle, and an occlusal (or incisal) third (Figure 4.9).
Figure 4.9. Anterior and Posterior Crown Divisions.
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MIDDLE
DISTAL MESIAL
CERVICAL
THIRD
MIDDLE THIRD
OCCLUSAL THIRD
MIDDLE
DISTAL MESIAL
CERVICAL
THIRD
MIDDLE THIRD
INCISAL THIRD
4.7.7.2. Longitudinal Division. Each mesial or distal axial surface may be divided into a facial, a middle, and a lingual third. Each facial or lingual surface may be divided into a mesial, a middle, and a distal third.
4.7.8. Line Angle. A line angle is an angle formed by the junction of two crown surfaces. It derives its name from those two surfaces. There are eight line angles per tooth.
4.7.8.1. The eight anterior tooth line angles are the mesiolabial, mesiolingual, distolabial, distolingual, labioincisal, linguoincisal, mesioincisal, and distoincisal.
4.7.8.2. The eight posterior tooth line angles are the mesiobuccal, mesiolingual, distobuccal, distolingual, bucco-occlusal, linguo-occlusal, disto-occlusal, and mesio-occlusal.
4.7.9. Point Angle. The junction of three crown surfaces forms a point angle. Combining the names of the three surfaces derives the name of the point angle.
4.7.9.1. The four anterior tooth point angles are the mesiolabioincisal, mesiolinguoincisal, distolabioincisal, and distolinguoincisal.
4.7.9.2. The four posterior tooth point angles are the mesiobucco-occlusal, mesiolinguoocclusal, distobucco-occlusal, and distolinguo-occlusal.
¶ 4.8. Distinctive Crown Convexities
4.8.1. Lobes. Lobes are one of the primary anatomical divisions of a crown; all teeth develop from either four or five lobes (Figure 4.10). (For example, a central incisor develops from four lobes while first molars develop from five lobes.) Lobes are usually separated by readily identifiable developmental grooves.
4.8.2. Mamelons. Mamelons are small, rounded projections of enamel from the incisal edges of newly erupted anterior teeth (Figure 4.11). The projections wear away soon after eruption.
4.8.3. Cingulum. A cingulum is found on the lingual aspect of an anterior tooth (Figure 4.12). It is a convex mount of enamel localized to the cervical one-third of the crown.
4.8.4. Cusps. Cusps are cone-shaped elevations on the occlusal surface of a premolar or molar and on the incisal edge of the canine (Figure 4.13).
Figure 4.10. Lobes.
Figure 4.11. Mamelons.
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MAMELON
Figure 4.12. Cingulum.
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CINGULUM
4.8.4.1. Canines have one cusp that represents the tooth ’s cutting edge. Maxillary premolars and the mandibular first premolars have two cusps, one buccal and one lingual. The mandibular second premolar normally has three cusps, one buccal and two lingual. The lingual cusps are subdivided into a mesiolingual and a distolingual.
4.8.4.2. Maxillary molars have four cusps, two buccal and two lingual. The two buccal cusps are subdivided into a mesiobuccal and a distobuccal. The two lingual cusps are subdivided into
a mesiolingual and a distolingual. (Once in a while, the mesiolingual cusp of a maxillary first molar carries an underdeveloped, rudimentary cusp called the cusp of Carabelli.)
Figure 4.13. Cusps.
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CUSPS
4.8.4.3. The mandibular first molar has five cusps, three buccal and two lingual. From anterior to posterior, the three buccal cusps are subdivided into a mesiobuccal, a distobuccal, and a distal. The two lingual cusps are divided into a mesiolingual and a distolingual. The mandibular second molar has four cusps called the mesiobuccal, distobuccal, mesiolingual, and distolingual.
4.8.5. Ridge. A ridge is a linear elevation found on the surface of a tooth as follows:
4.8.5.1. Marginal Ridge. A marginal ridge is a linear, rounded border of enamel that forms the mesial and distal margins of anterior teeth (as viewed from the lingual) and the mesial and distal borders of occlusal surfaces on posterior teeth (Figure 4.14). NOTE: When wax patterns are developed according to the additive wax technique, the definition of a marginal ridge is extended to include mesial and distal cusp ridges of buccal and lingual cusps on posterior teeth (paragraph 4.8.5.3).
Figure 4.14. Marginal Ridges.
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MARGINAL RIDGES
4.8.5.2. Lingual Ridge. The ridge of enamel that extends from the cingulum to the cusp tip on the lingual surface of most canines is called the lingual ridge (Figure 4.15).
4.8.5.3. Cusp Ridges. Each cusp has four cusp ridges radiating from its tip (Figure 4.16). They are named according to the direction they take away from the cusp tip (mesial, distal, facial, or lingual).
4.8.5.4. Triangular Ridge.
4.8.5.4.1. The occlusal surface of a cusp is composed of a mesial and a distal incline (Figure 4.17). These two inclines meet to form a triangular ridge of enamel that descends from the tip of the cusp to the central portion of the occlusal surface. A triangular ridge is either a facial or a lingual cusp ridge, depending on where the cusp is located.
Figure 4.15. Lingual Ridge.
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LINGUAL RIDGE
Figure 4.16. Cusp Ridges.
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BUCCAL CUSP RIDGE
MESIOBUCCAL INCLINE
DISTOBUCCAL INCLINE
MESIAL CUSP RIDGE
DISTAL CUSP RIDGE
DISTOLINGUAL INCLINE
MESIOLINGUAL INCLINE
LINGUAL CUSP RIDGE
Figure 4.17. Triangular Ridge.
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TRIANGULAR RIDGE
4.8.5.4.2. Cusps are described in some mouths as being “pointy” and in others as being “flat” or “blunt.” Most pointy posterior teeth have high cusp angle values (Figure 4.18). A cusp angle is the angle that a triangular ridge makes with a plane perpendicular to the long axis of the tooth.
Figure 4.18. Cusp Angle.
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PERPENDICULAR TO LONG AXIS
CUSP ANGLE
4.8.5.5. Transverse Ridge. A transverse ridge is the union of a buccal and lingual triangular ridge that crosses the surface of a posterior tooth transversely (roughly 90 degrees to both the buccal and lingual tooth surfaces) (Figure 4.19).
Figure 4.19. Transverse Ridge.
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TRANSVERSE RIDGE
4.8.5.6. Oblique Ridge. The only tooth on which an oblique ridge is found is the maxillary molar (Figure 4.20). An oblique ridge consists of a union between the triangular ridge of the distobuccal cusp and the distal cusp ridge of the mesiolingual cusp.
4.8.6. Cusp Inclines. A cusp incline or inclined plane is the sloping area found between two cusp ridges. To name an incline, you must combine the names of the cusp ridges that define a large part of its borders, for example, the distolingual incline of the buccal cusp of a maxillary first premolar (Figure 4.16).
¶ 4.9. Distinctive Crown Concavities
4.9.1. Fossae.
Figure 4.20. Oblique Ridge.
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OBLIQUE RIDGE
4.9.1.1. Lingual Fossa. The lingual fossa is an irregular, rounded concavity bound by the mesial marginal ridge, distal marginal ridge, cingulum, and incisal edge of the lingual surface of an incisor tooth (Figure 4.21). Lingual fossae are also found on both sides of the lingual ridge of a canine tooth.
Figure 4.21. Lingual Fossa.
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LINGUAL FOSSA
4.9.1.2. Triangular Fossa. Triangular fossae are located adjacent to marginal ridges on the occlusal surfaces of posterior teeth (Figure 4.22). There are two kinds of triangular fossae, a mesial and a distal.
Figure 4.22. Triangular Fossa.
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TRIANGULAR FOSSA
4.9.1.3. Central Fossa. A central fossa is a centrally located depression or concavity found on the occlusal surface of molars and mandibular second premolars (Figure 4.23). The other premolars have mesial and distal triangular fossae, but do not have a central fossa.
Figure 4.23. Central Fossa.
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MAXILLARY MOLARS
MANDIBULAR MOLARS
4.9.2. Developmental Groove. A developmental groove is the junction line between the inclined walls of adjacent cusp or ridges (Figure 4.24). Developmental grooves represent lines of union between lobes of the crown during its formation. These grooves appear on labial, occlusal, buccal, and lingual surfaces, and they are least apparent on the labial aspect of anteriors.
Figure 4.24. Developmental Grooves.
flowchart
4.9.3. Supplemental Groove. A supplemental groove is a minor, auxiliary groove that branches off from a much more prominent developmental groove (Figure 4.25). Supplemental grooves do not represent the junction of primary tooth parts.
4.9.4. Fissure. A fissure is a linear fault that sometimes occurs in a developmental groove (Figure 4.26). A fissure represents a lack of union between the inclined walls of a sulcus.
4.9.5. Pit. A pit is a small, pinpoint fault on the surface of a tooth usually found at the end of a developmental groove or where two fissures intersect.
Figure 4.25. Supplemental Grooves.
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SUPPLEMENTAL
GROOVES
Figure 4.26. Fissure.
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FISSURE
¶ 4.10. Description of Anterior and Posterior Tooth Surfaces
Figures 4.27 through 4.32 show specific convexities and depressions on anterior and posterior teeth. You should be able to name the coronal features of teeth after you study these figures closely.
Figure 4.27. Maxillary Central Incisor (Facial View).
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MAXILLARY CENTRAL INCISOR (FACIAL VIEW)
DEVELOPMENTAL GROOVE
2
3 CEMENTO-ENAMEL JUNCTION
1 LOBE
4
INCISAL EDGE
Figure 4.28. Maxillary Central Incisor (Lingual View).
¶ 4.11. Proximal Surface Contact Characteristics
4.11.1. Contact Points or Areas. Teeth make contact with one another at points or areas on the greatest contour of their proximal surfaces (Figure 4.33). The places where adjacent teeth make point contact are called contact points. Contact points become wider and flatter in time from wear that occurs during functional movements (chewing) or parafunctional movements (grinding). A flattened contact point is called a contact area.
4.11.2. Embrasure.
4.11.2.1. An embrasure is a space diverging from the contacting proximal surfaces of two adjacent teeth (Figure 4.34)
There are four of these spaces or embrasures recognized. They are the facial, lingual, gingival, and occlusal or incisal (depending on whether they are posterior or anterior teeth).
4.11.2.2. The gingival embrasure is located cervical to the contacting areas of adjacent teeth. A gingival embrasure has other names like cervical embrasure, apical embrasure, interproximal space, and septal space.
4.11.2.3. Interdental papillae (gingival tissue) fill interproximal spaces to a greater or lesser extent.
¶ 4.12. Occlusal Surface Outlines of Posterior Teeth
Figure 4.35 and the subparagraphs herein show the types of occlusal surface outlines:
Figure 4.29. Mandibular Canine (Lingual View).
4.12.1. Circular (Round)
The occlusal surfaces of the lower premolars are circular in outline.
4.12.2. Rectangular. The occlusal surfaces of the lower second molar and the upper premolars are often described as being rectangular or oblong in outline.
4.12.3. Trapezoid. A trapezoid is a plain four-sided figure with two parallel sides. The occlusal surface of the lower first molar is said to be trapezoidal in outline.
4.12.4. Rhomboid. A rhomboid is shaped as an equilateral parallelogram with two opposing oblique angles. The occlusal surfaces of the upper molars are rhomboidal in outline.
¶ Section 4B — Descriptions of Individual Teeth
¶ 4.13. Introduction
4.13.1. Paragraphs 4.14 through 4.27 describe each tooth of the permanent dentition (except the third molars, which are not reproduced in artificial teeth). In each instance, the tooth from the right side of the mouth is illustrated. NOTE: The drawings in this section were adapted from those appearing in the Ney Crown and Bridge Manual, J. M. Ney Co., Hartford CN.
4.13.2. The teeth are described as they usually look; however, teeth vary considerably from one person to another and certain teeth in the dentition tend to vary more than others.
4.13.3. Included in the illustrations of the premolars and the molars are drawings showing angles that can be carved in reproducing the occlusal surfaces of these teeth. The broken lines shown in the illustrations of the facial and lingual surfaces of the teeth indicate proper food deflection contours.
Figure 4.30. Maxillary Second Premolar (Occlusal View).
¶ 4.14. Maxillary Central Incisor
The maxillary central incisor (Figure 4.36) is the tooth nearest the median line in the maxillary arch.
4.14.1. Facial Surface. The facial surface is broad and resembles a thumbnail in outline. The right maxillary central incisor can be distinguished from the left maxillary central incisor because the distoincisal angle is more rounded than the mesioincisal angle and the incisal edge slopes slightly gingivally in a mesiodistal direction. The facial surface is convex, both mesiodistally and incisocervically. Three distinct lobes may be seen in the incisal portion, and they are separated by two developmental grooves.
4.14.2. Lingual Surface. The lingual surface appears slightly smaller than the facial surface, and the cervical portion is narrower. The large lingual fossa is bounded by prominent mesial and distal marginal ridges. There is a cingulum in the cervical portion, and there may be a pit in conjunction with the cingulum.
4.14.3. Incisal Edge. Viewed on end, the incisal edge appears nearly straight. Most of the wear is on the lingual portion of the edge, so the edge becomes beveled lingually. The cingulum lies more to the distal side of the tooth than to the mesial side.
4.14.4. Mesial Surface. The mesial surface loo ks like a wedge. The apex of the w edge is at the incisal edge of the tooth. The facial outline is slightly convex. The lingual outline is slightly concave from the incisal edge to the cingulum and convex from the cingulum to the cervical margin.
4.14.5. Distal Surface. The distal surface closely resembles the mesial surface. The lingual outline is more concave in the incisal portion than it is on the mesial surface.
Figure 4.31. Maxillary First Molar (Occlusal View).
Figure 4.32. Mandibular First Molar (Occlusal View).
Figure 4.33. Contact Areas.
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PROXIMAL SURFACE
CONTACT AREA
Figure 4.34. Embrasures.
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OCCLUSAL EMBRASURE
APICAL EMBRASURE
FACIAL EMBRASURE
LINGUAL EMBRASURE
Figure 4.35. Occlusal Surface Outlines of Posterior Teeth.
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ROUND
RECTANGULAR
TRAPEZOID
RHOMBOID
Figure 4.36. Maxillary Central Incisor.
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D M
FACIAL
M LINGUAL
D F
D M
L INCISAL
F MESIAL L
L F
DISTAL
¶ 4.15. Maxillary Lateral Incisor
The maxillary lateral incisor (Figure 4.37) is the second tooth from the median line in the maxillary arch. It resembles the central incisor, but is smaller in all dimensions.
4.15.1. Facial Surface. The facial surface is narrower and shorte r than the central inciso r. The distoincisal angle is more rounded than the mesioincisal angle. The distal portion of the incisal ridge slopes upward toward the distoincisal angle. The facial surface is convex.
Figure 4.37. Maxillary Lateral Incisor.
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D
M
D
F
L
INCISAL
M
F
MESIAL
L
DISTAL
4.15.2. Lingual Surface. The lingual surface resembles the facial surface in perip heral outline except that the cervical portion is n arrower. The features of this surface vary considerably from one individual to another. Proportionally, the lingual surface characte ristics of a lateral incisor are more marked than similar features on a central incisor.
4.15.3. Incisal Edge. Viewed on end, the incisal edge appe ars nearly straight. The cingulum lies slightly to the distal side of the tooth.
4.15.4. Mesial Surface. The mesial surface, like the central incisor’s, is wedge shaped. The ap ex of the wedge is at the incisal edge. The incisal edge lies somewhat further lingually than it does in the central incisor.
4.15.5. Distal Surface. The distal surface resembles the mesial surface, but the facial outline is more convex and the incisal portion of the lingual outline is more concave.
¶ 4.16. Maxillary Canine
The maxillary canine (Figure 4.38) is the third tooth from the median line in the maxillary arch. It is located at the corner of the arch, and its long root is embedded in the canine (cuspid) eminence. The maxillary c anine is usu ally the longest tooth in either jaw. It is called canine because it resembles a dog’s tooth. (It is sometimes referred to as a cuspid because it has one cusp on its incisal edge.)
Figure 4.38. Maxillary Canine.
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4.16.1. Facial Surface. The incisal portion of the facial surface is much broader than the cervical portion. The mesial and distal cusp ridges of the incisal edge slope downward toward the center to meet at the tip of the cusp. The distal slope is longer than the mesial slope. The facial surface is convex. It is divided into mesial and distal surfaces by the facial ridge. The ridge extends from the tip of the cusp to the point of greatest convexity. The mesiofacial surface of the canine falls on the curve of the arch formed by the anterior teeth. The distofacial surface conforms to the buccal alignment of posterior teeth.
4.16.2. Lingual Surface. The lingual surface resembles the facial surface in outline, but the cervical portion is narrower. The mesial and distal marginal ridges are prominent, and a strong lingual ridge runs from the tip of the cusp to the cingulum. The maxillary canine has the largest cingulum of all the anterior teeth.
4.16.3. Incisal Edge. Viewed on end, the incisal edge is slightly curved. The lingual portion of the tooth appears rugged; the ridges and grooves are very well defined.
4.16.4. Mesial Surface. The mesial surface is roughly triangular. From this aspect, the canine appears much thicker than the incisors.
4.16.5. Distal Surface. The distal surface is shaped very much like the mesial surface, but is shorter because the distal portion of the incisal edge slopes further cervically than the mesial portion.
¶ 4.17. Maxillary First Premolar
The maxillary first premolar (Figure 4.39) is the fourth tooth from the median line in the maxillary arch. It is the first posterior tooth. The premolars are sometimes called bicuspids because most of them have two cusps.
Figure 4.39. Maxillary First Premolar.
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4.17.1. Facial Surface. The facial surface resembles the canine in outline, but it is shorter occlusocervically and not quite as convex. The slopes of the mesial and distal cusp ridges are about equal in length. The facial ridge is prominent.
4.17.2. Lingual Surface. The lingual surface is much smaller than the facial surface in all dimensions, but is generally similar in outline. The lingual cusp is shorter than the facial cusp and is located mesial to the midline of the tooth.
4.17.3. Occlusal Surface.
4.17.3.1. The occlusal surface is broader facially than lingually. There are two cusps, the facial cusp and the lingual cusp.
4.17.3.2. The mesial and distal marginal ridges correspond to the marginal ridges of the anterior teeth. The mesial and distal proximal surfaces converge toward the lingual. Of the two, the distal surface has the greatest convergence.
4.17.3.3. The mesial fossa is distal to the mesial marginal ridge and the distal fossa is mesial to the distal marginal ridge. The facial and lingual triangular ridges extend from the tips of the cusps to the central groove. This groove ends at the mesial and distal pits. The mesial and distal marginal grooves arise from the mesial and distal pits and end on the mesial and distal surfaces, respectively.
4.17.4. Mesial Surface. The mesial surface is roughly rectangular in outline. The facial and lingual outlines are convex. The mesial surface is generally convex except for a concave area on the facial portion of the surface above the cervical margin. The mesial marginal groove extends onto the mesial surface.
4.17.5. Distal Surface. The distal surface resembles the mesial surface, but does not have the concave area above the cervical margin.
¶ 4.18. Maxillary Second Premolar
The maxillary second premolar is the fifth tooth from the median line in the maxillary arch. It closely resembles the first premolar, but it is more rounded in outline (Figure 4.40).
Figure 4.40. Maxillary Second Premolar.
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4.18.1. Facial Surface. The facial surface is slightly smaller than the facial surface of the first premolar. The slopes of the mesial and distal cusp ridges are about equal in length. The facial surface is convex, and the facial ridge is prominent.
4.18.2. Lingual Surface. The lingual surface is only slightly shorter than the facial surface because the facial and lingual cusps are nearly equal in length. This surface is also slightly narrower than the facial surface. The lingual surface is smoothly convex in all directions, and its greatest convexity is in the cervical third.
4.18.3. Occlusal Surface. In general, the occlusal surface has the same form and features as the occlusal surface of the first premolar. However, the facial and lingual portions are more nearly equal in size and the mesial and distal pits are closer together.
4.18.4. Mesial Surface. The mesial surface is wider in the cervical portion than in the occlusal portion. The facial outline is slightly convex except in the central portion. The lingual outline is convex. Both cusps appear more rounded that the cusps of the first premolar.
4.18.5. Distal Surface. The distal surface is slightly shorter than the mesial surface, but it is about the same width. The facial and lingual outlines are convex. The surface is smoothly convex except at the distal marginal groove.
¶ 4.19. Maxillary First Molar
The maxillary first molar (Figure 4.41) is the sixth tooth from the median line in the maxillary arch. It is the largest tooth in either arch. The maxillary and mandibular first molars are often called 6-year molars.
Figure 4.41. Maxillary First Molar.
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4.19.1. Facial Surface. The facial surface is roughly heart-shaped in outline. The mesiofacial and distofacial cusps form the occlusal border, and the facial groove divides the cusps. The surface is generally convex except at this groove. The surface has three ridges. A ridge extends perpendicularly from the tip of each cusp and a third ridge extends horizontally in the cervical portion.
4.19.2. Lingual Surface. The mesiolingual and distolingual cusps outline the occlusal border of the lingual surface. The mesiolingual cusp is the largest of the posterior teeth. Quite often this tooth has a residual fifth cusp, the cusp of Carabelli, which is on the lingual surface of the mesiolingual cusp. When present, this cusp is shorter than the other cusps and does not form part of the occlusal surface. The lingual surface is generally convex except at the distolingual groove.
4.19.3. Occlusal Surface. The occlusal surface is roughly rhomboidal. The cusps are large and prominent, with broad surfaces broken up into rugged ridges and well-defined grooves. The mesiolingual cusp is the largest of the cusps. The distolingual groove separates it from the distolingual cusp. An oblique ridge connects the mesiolingual and distofacial cusps. It runs parallel to the distolingual groove. The facial groove runs from the central pit onto the facial surface. The mesial and distal pits lie near the mesial and distal marginal ridges, respectively.
4.19.4. Mesial Surface. The mesial marginal groove, which starts at the mesial pit, notches the occlusal border of the mesial surface. A double convexity marks the lingual margin if the cusp of Carabelli is present.
4.19.5. Distal Surface. The distal marginal groove, which starts at the distal pit, notches the occlusal border of the distal surface.
¶ 4.20. Maxillary Second Molar
The maxillary second molar (Figure 4.42) is the seventh tooth from the median line in the maxillary arch. It is quite similar to the first molar, but it is smaller. This tooth is often called the 12-year molar.
Figure 4.42. Maxillary Second Molar.
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4.20.1. Facial Surface. The facial surface of the maxillary second molar is less symmetrical than the first molar. The mesiofacial cusp is larger than the distofacial cusp. The facial groove lies nearer to the distal surface than it does to the mesial surface. The same three ridges appear on the facial surface as appear on the facial surface of the first molar (paragraph 4.19.1).
4.20.2. Lingual Surface. The occlusal border of the lingual surface is marked by two cusps, the mesiolingual and the distolingual. The mesiolingual cusp is the largest. (NOTE: The distolingual cusp is not fully reproduced in artificial teeth. For this reason, many of these artificial teeth appear triangular when viewed occlusally.) The second molar has no cusp of Carabelli. The cervical border is nearly straight, and the lingual surface is generally convex.
4.20.3. Occlusal Surface. The occlusal surface is very similar to the occlusal surface of the first molar (paragraph 4.19.3).
4.20.4. Mesial Surface. The mesial surface is fairly symmetrical in outline. The mesiofacial cusp is slightly longer than the mesiolingual cusp. The facial outline is nearly straight, but the lingual outline is distinctly convex.
4.20.5. Distal Surface. The distal surface is somewhat smaller than the mesial surface. The distofacial cusp is longer than the distolingual cusp. The facial outline appears less convex than it does from the mesial aspect.
¶ 4.21. Mandibular Central Incisor
The mandibular central incisor (Figure 4.43) is the first tooth from the median line in the mandibular arch. As described in the paragraphs below, it is the smallest tooth in either arch and the simplest in form:
Figure 4.43. Mandibular Central Incisor.
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4.21.1. Facial Surface. The facial surface is widest at the incisal edge. The mesioincisal and distoincisal angles are almost 90-degree angles. The mesial and distal borders are almost parallel in the incisal portion. In their middle and cervical portions, the outlines converge but do not meet. The facial surface is convex. There are three lobes separated by two developmental grooves. The grooves are more faint than they are in the maxillary central incisor, often disappearing entirely.
4.21.2. Lingual Surface. The lingual surface is quite similar in outline to the facial surface, but the cervical portion is more narrow. The incisal portion of the lingual surface is concave. The cingulum, which begins fairly close to the cervical margin, blends more smoothly with the rest of the lingual surface than it does on the maxillary incisors.
4.21.3. Incisal Edge. Viewed on end, the incisal edge appears nearly straight; and, in adults, the edge is worn smooth and sharp.
4.21.4. Mesial Surface. The mesial surface is wedge shaped. The facial outline is convex. The lingual outline is concave in the incisal and middle portions and convex in the cervical portion. The mesial surface is almost flat incisogingivally.
4.21.5. Distal Surface. The distal surface closely resembles the mesial surface.
¶ 4.22. Mandibular Lateral Incisor
The mandibular lateral incisor (Figure 4.44) is the second tooth from the median line in the mandibular arch. Although it resembles the mandibular central incisor, it is wider and longer:
Figure 4.44. Mandibular Lateral Incisor.
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4.22.1. Facial Surface. The facial surface is less symmetrical than the facial surface of the mandibular central incisor. The incisal edge slopes upward toward the mesioincisal angle, which is slightly less than 90 degrees. The distoincisal angle is rounded. The mesial border is more nearly straight than the distal border. (The distal border is slightly convex in the incisal portion and slightly concave in the middle and cervical portions.) The facial surface is convex.
4.22.2. Lingual Surface. The lingual surface is similar in outline to the facial surface. The mesial and distal borders converge more sharply than they do on the facial surface. The incisal portion of the lingual surface is concave. The cingulum is quite large, but blends smoothly with the rest of the surface.
4.22.3. Incisal Edge. Viewed on end, the incisal edge forms a nearly straight line that slants lingually toward its distal end. This is because the distal portion of the facial surface is more convex than the mesial portion.
4.22.4. Mesial Edge. The mesial surface is wedge shaped. The facial outline is convex. The lingual outline is concave in the incisal portion and convex in the middle and cervical portions.
4.22.5. Distal Edge. The distal surface is slightly shorter than the mesial surface because the incisal edge slants downward toward the distoincisal angle. The incisal portion of the distal surface is thicker than the incisal portion of the mesial surface.
¶ 4.23. Mandibular Canine
The mandibular canine (Figure 4.45) is the third tooth from the median line in the mandibular arch. It is similar to the maxillary canine, but more narrow.
Figure 4.45. Mandibular Canine.
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4.23.1. Facial Surface. The facial surface is asymmetrical in outline. The distal portion of the surface is shorter and broader than the mesial portion. Consequently, the distal cusp ridge of the incisal edge is much longer than the mesial edge. The mesial border is slightly convex. The upper portion of the distal border is very convex, and the lower portion is slightly concave. The three lobes are quite distinct. The central lobe forms the strong facial ridge.
4.23.2. Lingual Surface. The lingual surface is similar in outline to the facial surface except the cervical portion is more narrow. Most of the surface is concave incisocervically. The lingual ridge divides the surface into two planes. The ridge blends smoothly with the cingulum, which is small and confined to the cervical portion of the tooth.
4.23.3. Incisal Edge. Viewed on end, the incisal edge forms two curves that meet at the tip of the cusp. The mesial portion of the facial outline is convex, but the distal portion is slightly flattened. The mesial curve follows the alignment of the facial surfaces of the anterior teeth. The distal part of the facial outline conforms to the buccal surface alignment of posterior teeth. The cingulum appears uniformly curved on both sides.
4.23.4. Mesial Surface. The mesial surface more nearly resembles the incisors than the mesial surface of the maxillary canine in outline. The facial outline is convex. The lingual outline is chiefly concave except near the cervical margin. The mesial surface is generally convex.
4.23.5. Distal Surface. The distal surface is shorter than the mesial surface, but about the same width. The incisal portion is very convex both faciolingually and incisogingivally. The cervical portion is concave incisogingivally.
¶ 4.24. Mandibular First Premolar
The mandibular first premolar (Figure 4.46) is the fourth tooth from the median line in the mandibular arch. It is the smallest and least typical of the premolars.
Figure 4.46. Mandibular First Premolar.
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4.24.1. Facial Surface. The facial surface is shaped somewhat like a bell because the cervical portion is markedly constricted in comparison with the occlusal portion. The distal cusp ridge of the occlusal border is slightly longer than the mesial cusp ridge, and the distoincisal angle is more rounded than the mesioincisal angle. The distal portion of the surface is slightly shorter and broader than the mesial surface. The surface is convex.
4.24.2. Lingual Surface. The lingual surface is much smaller than the facial surface because the lingual cusp is smaller than the facial cusp. The tip of the lingual cusp is closer to the mesial margin than to the distal margin. The surface is convex.
4.24.3. Occlusal Surface. The occlusal surface is marked by a strong facial cusp and a lingual cusp that may appear almost rudimentary. The marginal ridges are well defined. The strong lingual ridge of the facial cusp and the facial ridge of the lingual cusp may join, forming a transverse ridge. In this instance, the central groove would be very faint.
4.24.4. Mesial Surface. The mesial surface is irregular in outline. From this aspect, the tooth appears to be tipped lingually. The facial cusp forms most of the occlusal outline. The facial outline is very convex, and the greatest convexity is in the cervical third. The lingual outline is fairly straight. Occlusocervically, the mesial surface is very convex in the occlusal portion and concave in the cervical portion.
4.24.5. Distal Surface. The distal surface is similar to the mesial surface.
¶ 4.25. Mandibular Second Premolar
The mandibular second premolar (Figure 4.47) is the fifth tooth from the median line in the mandibular arch.
Figure 4.47. Mandibular Second Premolar.
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4.25.1. Facial Surface. The facial surface is very similar to the surface of the mandibular first premolar. The facial ridge is prominent, and the surface is convex.
4.25.2. Lingual Surface. The lingual surface is similar to the surface of the mandibular first premolar except there may be two cusps--the mesiolingual and the distolingual.
4.25.3. Occlusal Surface. The occlusal surface may appear in a number of forms. In the form pictured, the mesial and distal triangular fossae are quite distinct as they join the short central groove. There are three pits; central, mesial, and distal.
4.25.4. Mesial Surface. The mesial surface is similar to the surface of the mandibular first premolar, but it is more regular in outline. The surface is convex faciolingually. Occlusocervically, the occlusal portion is convex, and the cervical portion is concave.
4.25.5. Distal Surface. The distal surface is very similar to the mesial surface.
¶ 4.26. Mandibular First Molar
The mandibular first molar (Figure 4.48) is the sixth tooth from the median line in the mandibular arch. It is also the largest tooth in the mandibular arch. The maxillary and mandibular first molars are often called 6-year molars.
Figure 4.48. Mandibular First Molar.
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4.26.1. Facial Surface. The facial surface presents three cusps; mesiofacial, distofacial, and distal. The mesiofacial cusp is the largest; the distal is the smallest. The distofacial cusp, though smaller than the mesiofacial cusp, may be slightly higher. The mesiofacial (facial) groove, which may end in a pit, separates the mesiofacial and distofacial cusps. The distofacial groove separates the distofacial and distal cusps. The facial surface is convex except at the grooves.
4.26.2. Lingual Surface. The lingual surface has a mesiolingual cusp and a distolingual cusp, which are similar in outline. They are separated by the sharply defined lingual groove. The surface is slightly convex.
4.26.3. Occlusal Surface. The occlusal surface of this tooth, unlike the surface of the maxillary first molar, is formed by all five cusps and is trapezoidal in shape. There are three pits; mesial, central, and distal. A central groove, which connects these pits, divides the occlusal surface into the lingual and facial halves. From the occlusal aspect, the mesiofacial cusp appears the largest and the distal cusp appears the smallest.
4.26.4. Mesial Surface. The mesial surface is wider in the cervical portion than it is in the occlusal portion because the occlusal and middle thirds of the facial outline slope outward occlusocervically. The lingual outline is quite straight and nearly perpendicular.
4.26.5. Distal Surface. The distal surface is more symmetrical than the mesial surface because the facial outline is more nearly perpendicular than it is on the mesial surface.
¶ 4.27. Mandibular Second Molar
The mandibular second molar (Figure 4.49) is the seventh tooth from the median line in the mandibular arch. It is one of the 12-year molars.
4.27.1. Facial Surface. The facial surface is almost symmetrical in outline, and the mesiofacial and distofacial cusps appear nearly equal in size. The two cusps are separated by the deep facial groove. There is no third cusp.
4.27.2. Lingual Surface. The lingual surface is symmetrical, but the mesiolingual cusp is slightly longer and bulkier than the distolingual cusp. The lingual groove is shorter and less distinct than the groove on the facial surface.
4.27.3. Occlusal Surface. The occlusal surface is rectangular in shape. From this view, the mesiofacial cusp appears slightly larger than the other three cusps. The occlusal surface has three pits; mesial, central, and distal.
Figure 4.49. Mandibular Second Molar.
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4.27.4. Mesial Surface. The mesial surface resembles the mesial surface of the mandibular first molar, but it is shorter. The facial outline is convex occlusocervically. The occlusal portion of the lingual outline is convex, and the cervical portion is more nearly straight.
4.27.5. Distal Surface. The distal surface resembles the mesial surface.
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