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2-6 PERMANENT DENTITION The permanent dentition consists of 32 teeth. Each tooth in the permanent dentition is described in this section. It should be remembered that teeth show considerable variation in size, shape, and other characteristics from one person to another. Certain teeth show a greater tendency than others to deviate from the normal. The descriptions that follow are of normal teeth. MAXILLARY CENTRAL INCISORS The maxillary central incisor (tooth #8 or #9) is illustrated in figures 2-27 and 2-28. Viewed mesially or distally, a maxillary central incisor looks like a wedge, with the point of the wedge at the incisal (cutting) edge of the tooth. 
Figure 2-27.—Surfaces of a maxillary central incisor. | 
Figure 2-28.—Features of a lingual surface of maxillary central incisor. | - Facial Surface-The facial surface resembles a thumbnail in outline. The mesial margin is nearly straight and meets the incisal edge at almost a 90° angle, but the distal margin meets the incisal edge in a curve. The incisal edge is straight, but the cervical margin is curved like a half moon. Two developmental grooves are on the facial surface.
- Lingual Surface—The lingual surface (fig. 2-28) is quite similar to the facial surface in outline except that it is slightly smaller in all dimensions. At the mesial and distal margins there are marginal ridges. Occasionally there is a cingulum at the junction of the lingual surface with the cervical line. Sometimes a deep pit, the lingual pit, is found in conjunction with a cingulum.
- Root Surface—As with all anterior teeth, the root of the maxillary central incisor is single. This root is from one and one-fourth to one and one-half times the length of the crown. Usually, the apex of the root is inclined slightly distally.
MAXILLARY LATERAL INCISORS The maxillary lateral incisor (tooth #7 or #10), illustrated in figure 2-29, is much like the maxillary central incisor, except in size: it is shorter, narrower, and thinner. 
Figure 2-29.—Surfaces of a maxillary lateral incisor. - Facial Surface—The developmental grooves on the facial surface are not so evident as those of the central incisor. Of more significance, however, is the distoincisal angle, which is well-rounded with this curvature continuing to the cervical line. The mesiofacial angle is nearly straight to the cervical line.
- Lingual Surface—The shape of the lingual surface varies with the individual. In some persons it is markedly concave, almost spoon-like in appearance, and in others, it is flat. The lingual surface is almost the same as the facial surface.
- Root Surface—The root is conical (cone-shaped) but somewhat flattened mesiodistally.
MANDIBULAR CENTRAL INCISORS The mandibular central incisor (tooth #24 or #25) is illustrated in figure 2-30. These are the first permanent teeth to erupt, replacing deciduous teeth, and are the smallest teeth in either arch. 
Figure 2-30.—Surfaces of a mandibular central incisor. - Facial Surfaces—The facial surface of the mandibular central incisor is widest at the incisal edge. Both the mesial and the distal surfaces join the incisal surface at almost a 90° angle. Although these two surfaces are nearly parallel at the incisal edge, they converge toward the cervical margin. The developmental grooves may or may not be present. When present, they appear as very faint furrows.
- Lingual Surface—The lingual surface is similar in outline to the facial surface. The incisal portion of the lingual surface is concave. The cingulum is quite large but blends in smoothly with the rest of the surface.
- Root Surface—The root is single and extremely flattened on its mesial and distal surfaces.
MAXILLARY CUSPIDS - 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°. The distoincisal angle is rounded. The mesial border is more nearly straight than the distal border.
- Lingual Surface—The lingual surface is concave from the incisal edge to the cervical margin.
- Root Surface—The root is slender and extremely flattened on its mesial and distal surfaces.
MANDIBULAR LATERAL INCISORS The mandibular incisor (tooth #23 or #26) illustrated in figure 2-31, is a little wider mesiodistal than the mandibular central incisor, and the crown is slightly longer from the incisal edge to the cervical line. 
Figure 2-31 .—Surfaces of a mandibular lateral incisor The maxillary cuspid (tooth #6 or #11) is illustrated in figures 2-32 and 2-33. The maxillary cuspid is usually the longest tooth in either jaw. Since it resembles a dog’s tooth, it is sometimes called the canine. 
Figure 2-32.—Surfaces of a maxillary cuspid. 
Figure 2-33.—Features of facial and lingual surfaces of a maxillary cuspid. - Facial Surface—The facial surface of the crown (fig. 2-33) differs considerably from that of the maxillary central or lateral incisors. In that the incisal edges of the central and lateral incisor are nearly straight, the cuspid has a definite point, or cusp. There are two cutting edges, the mesioincisal and the distoincisal. The distoincisal cutting edge is the longer of the two. The developmental grooves that are so prominent on the facial surface of the central incisor are present here, extending two-thirds of the distance from the tip of the cusp to the cervical line.
- Lingual Surface—The lingual surface has the same outline as the facial surface but is somewhat smaller because the mesial and distal surfaces of the crown converge toward the lingual surface. The lingual surface is concave, with very prominent mesial and distal marginal ridges, and a lingual ridge, which extends from the tip of the cusp toward the cervical line. There is often a cingulum in the cervical portion of the lingual surface of the crown.
- Root Surface—The root is single and is the longest root in the arch. It is usually twice the length of the crown. This is because the cuspid is designed for seizing and holding food.
MANDIBULAR CUSPIDS The mandibular cuspid (tooth #22 or #27) is illustrated in figure 2-34. These teeth, like the mandibular incisors, are smaller and more slender than the opposing teeth in the maxillary arch. 
Figure 2-34.—Surfaces of a mandibular cuspid. - Facial Surface—The facial surface of a mandibular cuspid is much the same as that of a maxillary cuspid, except that the distoincisal cutting edge is almost twice the length of the mesial edge.
- Lingual Surface—The lingual surface as a rule is very smooth, and a cingulum is rarely present.
- Root Surface—The single root is not so long as that of the maxillary cuspid and is much flatter mesiodistal.
MAXILLARY FIRST BICUSPID The maxillary first bicuspid (tooth #5 or #12), illustrated in figures 2-35 and 2-36, is the fourth tooth from the midline. It is considered to be the typical bicuspid. (The word "bicuspid" means "having two cusps.") Sometimes bicuspids are called premolars because they are just in front of the molar teeth. 
Figure 2-35.—Surfaces of maxillary first bicuspid. 
Figure 2-36.—Features of an occlusal surface of maxillary first bicuspid. - Facial Surface—The facial surface is somewhat similar to the facial surface of the cuspid. However, the tip of the facial cusp is located in the center of the "biting" edge, which is called the occlusal edge or occlusal margin. From the cusp tip to the cervical margin, there is a slight ridge, called the facial ridge, similar to the facial ridge found in cuspid teeth.
- Lingual Surface—The lingual surface is narrower and shorter than the facial surface, and is smoothly convex in all directions. The cusp tip is in the middle of the occlusal edge.
- Root Surface—The root is quite flat on the mesial and distal surfaces. In about 50 percent of maxillary first bicuspids, the root is divided in the apical third, and when it so divided, the tips of the facial and lingual roots are slender and finely tapered.
- Occlusal Surface—The occlusal surface (fig. 2-36) has a facial cusp and a lingual cusp. There are mesial and distal marginal ridges. Two fossae are on the occlusal surface-the mesial and distal fossae.
MAXILLARY SECOND BICUSPID The maxillary second bicuspid (tooth #4 or #13), illustrated in figure 2-37, resembles the first bicuspid very closely, but is smaller in dimensions. The cusps are not as sharp as the maxillary first bicuspid and have only one root. 
Figure 2-37.—Surfaces of maxillary second bicuspid. MANDIBULAR FIRST BICUSPID The mandibular first bicuspid (tooth #21 or #28), illustrated in figure 2-38, is the fourth tooth from the midline. It is the smallest of the four bicuspids. The term bell-crowned is used to describe its appearance. The mandibular first bicuspid has many characteristics of a cuspid. 
Figure 2-38.—Surfaces of mandibular first bicuspid. - Occlusal Surface—A large facial cusp, which is long and well defined, and a small nonfunctional lingual cusp are present on the mandibular first bicuspid.
- Root Surface—The root of the mandibular first bicuspid is usually single, but on occasion can be bifurcated (two roots).
MANDIBULAR SECOND BICUSPID The mandibular second bicuspid (tooth #20 or #29), illustrated in figure 2-39, is the fifth tooth from the midline. 
Figure 2-39.—Surfaces of mandibular second bicuspid. - Facial Surface—The facial surface has the same facial surface as the first bicuspid.
- Lingual Surface—The lingual surface is similar to that of the mandibular first bicuspid, with the exception that there may be two lingual cusps present.
- Occlusal Surface—The occlusal surface usually has a total of three well-defined cusps. Viewed from above, the three cusp present a Y-form pattern.
- Root Surface—The root of the tooth is single, and in a great many instances, the apical region is found to be quite curved.
MAXILLARY FIRST MOLAR The maxillary first molar (tooth #3 or #14), illustrated in figures 2-40 and 2-41, is the sixth tooth from the midline. The first molars are also known as 6-year molars, because they erupt when a child is about 6 years old. 
Figure 2-40.—Surfaces of maxillary first molar. - Facial Surface—The facial surface has a facial groove that continues over from the occlusal surface, and runs down to the middle third of the facial surface.
- Lingual Surface—In a great many instances, there is a cusp on the lingual surface of the mesiolingual cusp. This is a fifth cusp called the cusp of Carabelli, which is in addition to the four cusps on the occlusal surface.
- Occlusal Surface—In all molars the patterns of the occlusal surface (fig. 2-41) are quite different from those of the bicuspids. The cusps are large and prominent, and the broad grinding surfaces are broken up into rugged appearing ridges and well-defined grooves. An oblique ridge, which is not present on the bicuspids, appears here (it also appears on maxillary second and third molars).
- Roots—The maxillary first molar has three roots, which are named according to their locationsmesiofacial, distofacial, and lingual (or palatal root). The lingual root is the largest.
Figure 2-41.—Features of occlusal surfaces of maxillary first molar. MAXILLARY SECOND MOLAR The maxillary second molar (tooth #2 or #15), illustrated in figure 2-42, is the seventh tooth from the midline. The second molars are often called 12-year molars because they erupt when a child is about 12 years old. 
Figure 2-42.—Surfaces of maxillary second molar. Because it has the same function as the maxillary first molar, its physical characteristics are basically the same. The second molar is smaller, the occasional fifth cusp of Carabelli does not appear, and there is a marked reduction in the size of the distolingual cusp. MAXILLARY THIRD MOLAR The maxillary third molar (tooth #1 or #16), illustrated in figure 2-43, is the eighth tooth from the midline. Third molars are often called wisdom teeth because they erupt when the young adult is passing into manhood or womanhood. The tooth is much smaller than the maxillary first or second molars, with an occlusal outline that is nearly circular. 
Figure 2-43.—Surfaces of maxillary third molar. - Occlusal Surface—Numerous fissures and grooves cover the occlusal surface. There is no distinct oblique ridge.
- Root Surface—The root may have from one to as many as eight divisions. These divisions are usually fused and very often curved distally.
MANDIBULAR FIRST MOLAR The mandibular first molar (tooth #19 or #30), illustrated in figures 2-44 and 2-45, is the sixth tooth from the midline. It is the first permanent tooth to erupt. 
Figure 2-44.—Surfaces of mandibular first molar. - Facial Surface—The facial surface has two grooves: the facial groove, which is an extension of the facial groove from the occlusal surface and the distofacial groove, an extension of the distofacial groove from the occlusal surface.
- Occlusal Surfaces—The occlusal surface has five cusps (fig. 2-45). The fifth cusp is called the distal cusp.
- Roots—The tooth has two roots, a mesial and a distal.
Figure 2-45.—Features of an occlusal surface of mandibular first molar. MANDIBULAR SECOND MOLAR The mandibular second molar (tooth #18 or #31), illustrated in figure 2-46, is the seventh tooth from the midline. 
Figure 2-46.—Surfaces of mandibular second molar. - Facial Surface—The facial surface has only one groove, the facial groove, which arises on the occlusal surface, extends over the facial margin onto the facial surface.
- Occlusal Surfaces—The greatest difference between the occlusal surfaces of the mandibular first and second molars is that the occlusal surface of the second molar has no fifth cusp.
- Roots—The mandibular second molar has two roots that are smaller than those of the first molar.
MANDIBULAR THIRD MOLAR The mandibular third molar (tooth #17 or #32), illustrated in figure 2-47, is the eighth tooth from the midline. It appears in many forms, sizes, and shapes. Since its function is similar to that of the other two mandibular molars, its general appearance is the same. It has smaller surfaces, more supplemental grooves, and four or five cusps, which are not so sharply differentiated as those of the first two molars. 
Figure 2-47.—Surfaces of mandibular third molar. - Roots—The roots, generally two in number, are shorter in length and tend to be fused together. In many instances they show a distinct distal curve.
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