The Permanent Canines

A. Introduction:

1. The canines are the most important teeth in the mouth of carnivores, and are the "fangs" of many animals. In fact, the name, canine, is derived from the Latin term for dog.

2. The human permanent canines (or cuspids) in each arch have a similar appearance and function. They are often called the "cornerstones of the mouth", since they are intermediary between the incisors and posterior teeth in function, form, and arch position.

a. In function, the canine's role in mastication is mainly tearing, which is intermediate between the incising of the other anterior teeth, and the grinding of the posterior teeth. They also contribute greatly to the cosmetic and facial support function, and play a part in phonetics as well.

b. In form, they have the same general wedge shape as the incisors, when viewed from a proximal aspect. However, when viewed from the facial, they look like premolars. They exhibit biting edges, cingula, and marginal ridges which are similar to those of incisors, while the facial ridge and cusp are features common to posterior teeth.

c. In arch position, they are the third tooth from the midline in each quadrant, and are positioned as a cornerstone between the more or less laterally positioned incisors and the anteroposteriorly positioned premolars and molars. This location is important to an individual's appearance, since the canines play a major role in the support of the facial muscles.

3. The canines exhibit the greatest combined crown plus root length in each arch, and their root is very firmly anchored in alveolar bone. The thick facial plate of bone overlying the canine root is termed the canine eminence. Because of this bony support, and the length of the root, the canines are usually the most steadfast teeth in the mouth.

B. Permanent Maxillary Canine: 1. General characteristics:

a. Arch position - The permanent maxillary canine replaces the deciduous maxillary canine, and is located third from the midline in each maxillary quadrant. The canine shares a mesial contact with the maxillary lateral incisor, and contacts the maxillary first premolar on the distal.

b. Universal number: Maxillary right canine - #6 Maxillary left canine - #11

c. General form and function - As already pointed out, the canine's function in mastication is mainly tearing and piercing and they also function in esthetics and speech. The general crown form is pentagonal when viewed from the labial or lingual aspect, and triangular when viewed from the proximals. The crown exhibits one rather sharp cusp incisally which has two biting edges, in comparison to the single and relatively straight incisal edge of the incisors. The crown is bulky in comparison to the incisors, especially labiolingually, which gives it the appearance of strength.

Comparisons to the maxillary central incisor:

a. Incisogingivally, the crown length is about the same, or even slightly shorter, than that of the central incisor.

b. Mesiodistally, the canine crown is noticeably narrower.

c. Labiolingually, the crown is considerably wider than that of the central incisor.

d. The root is longer, and the combined crown plus root length is greater in the canine.

e. The cingulum shows greater development, and it is a much stronger tooth than the central incisor.

f. The middle labial lobe of the canine is much better developed, which is partially responsible for the greater convexity of the canine's facial surface.

Development Table (Maxillary canine)*

Initiation of calcification 4 to 5 months

Completion of enamel 6 to 7 years

Eruption 11 to 12 years

Completion of root 13 to 15 years

Labial aspect: i a. General considerations - The labial surface is convex in all directions, but the curvature is more pronounced mesiodistally. The general outline of the surface is pentagonal.

b. Mesial outline - The mesial margin is usually convex from the mesial contact area to the cervical line, with a rounded mesioincisal angle. The height of contour of this margin is at the contact area, which is located at the junction of the incisal and middle thirds.

c. Distal margin - The distal margin is shorter than the mesial margin, and is usually concave between the distal contact area and the cervical line. It also has a more rounded incisal angle. The height of contour, at the contact area, is in the middle third.

d. Incisal margin - The incisal margin is divided into two components by the tip of the cusp, and they are termed the mesioincisal and distoincisal slopes (or mesial and distal cusp ridges). Prior to attrition, the mesioincisal slope is normally the shorter of the two, and also slopes to a lesser degree. Nevertheless, the tip of the cusp is located in line with the center of the root.

With normal attritional wear, the cusp tip moves to the distal, thus lengthening the mesioincisal slope and shortening the distoincisal slope. Usually the cusp tip also extends past the plane of occlusion of the other teeth in the arch. This extension may be as much as a millimeter or two, and reflects the evolution of the human canine from the carnivorous animal fang.

e. Cervical outline - The CEJ is quite evenly curved toward the root.

f. Other considerations - A labial ridge transcends the middle of the surface in an incisocervical direction, and is most prominent in the incisal portion. This ridge represents a greater development of the middle labial lobe, as compared to the mesial and distal labial lobes. It is responsible for the greater mesiodistal convexity of the incisal two-thirds of the labial surface, when compared to the incisors.

Separating the three lobes and lying on either side of the labial ridge in the incisal portion of the labial surface are two faint concavities, termed mesiolabial and distolabial developmental depressions. In newly erupted canines, these depressions may extend onto the two incisal slopes, thus creating a slightly concave, or notched area, when viewed from the facial.

Imbrication lines can often be found in the cervical third of the surface, especially in newly erupted teeth, but mamelons are ordinarily not present on the incisal outline

The height of contour is located in the cervical third of the surface. Lingual aspect:

a. Mesial, distal, and incisal outlines - These margins are similar to those of the labial aspect.

b. Cervical outline - The cervical line curves asymmetrically toward the apex with a slight offset to the distal.

c. Other considerations - The mesiodistal dimension of the lingual surface is less than that of the labial surface, since the mesial and distal surfaces converge slightly toward the lingual.

The cingulum is bulky, and normally smooth. It shows greater development than the cingulum of the maxillary central incisor. The marginal ridges are also prominent.

The incisal half of the surface is relatively smooth, but does exhibit faint landmarks. There is normally a lingual ridge extending incisogingivally in the center of this area, with shallow mesiolingual and distolingual fossae between it and the prominent marginal ridges.

The cingulum and incisal half of the lingual surface are on rare occasions separated by a linguogingival groove, which in some cases may contain a lingual pit near its center. When present, the groove is normally quite shallow. The lingual pit may be present, even when the groove is absent. Nevertheless, the presence of a groove or pit is not very common. The lingual height of contour is associated with the greatest convexity of the cingulum in the cervical third. Mesial aspect:

a. General considerations - The mesial surface is convex in all dimensions, and is wider labiolingually than the mesial surface of any of the incisors. Like other anterior teeth, it is triangular in shape.

b. Labial outline - The labial margin is convex incisocervically, with the crest of curvature in the cervical third. This convexity is slightly greater than for the same outline of the maxillary incisors.

c. Lingual outline - The lingual outline is concave in the incisal half, and convex in the cingulum area, or gingival half, but less so than on incisor crowns because of the lingual ridge. The height of contour is in the cervical third.

d. Cervical outline - The cervical line is curved evenly toward the incisal, with the greatest extent of curvature directly beneath the incisal edge.

e. Incisal outline - The incisal edge is thick, and from this aspect, has an outline which slopes from labial to lingual, like the maxillary incisors.

f. Other considerations - The contact area is located at the junction of the middle and incisal thirds, about midway between the labial and lingual surfaces. It has an ovoid shape, which is longer incisogingivally than labiolingually.

The height of contour of the mesial surface is located at the contact area, at the junction of the incisal and middle thirds.

7. Distal aspect: The distal surface is similar to the mesial surface, with the following exceptions:

a. The distal surface is generally smaller, with resultant shorter labial and lingual margins.

b. The cervical margin exhibits less curvature incisally than it does on the mesial surface.

c. The lingual outline of the distal marginal ridge is likely to be more irregular than the outline of the mesial marginal ridge.

d. The contact area is more circular than on the mesial, and is located at a more cervical level which is in the middle third. Although a different shape, it occupies about the same sized area as does the mesial contact.

e. A concavity is usually present in the cervical half of the distal surface.

f. The height of contour is located at a more cervical level, and is associated with the contact area in the middle third.

8. Incisal aspect:

a. From the incisal, the maxillary canine is generally convex in both its labial and lingual outlines. The tooth's strength is exhibited by the thicker labiolingual dimension, when compared to the maxillary incisors.

b. From this aspect, the canine crown has an asymmetrical diamond shaped ^ outline. The mesial half is thicker labiolingually and more convex, while the distal portion is thinner and exhibits a slight concavity in its labial and/ or lingual outline. The cingulum is offset to the distal from this view.

c. The greater development of the middle labial lobe is also evident from the incisal aspect, and contributes to the increased convexity of the labial outline, when compared to the maxillary incisors.

a. The root is single, and normally the longest root of any tooth in the mouth.

b. From all aspects, the root tapers gradually to a sharp, or slightly blunted apex.

c. The root is generally wider labiolingually than mesiodistally. Both lingual and labial surfaces are convex, while the mesial and distal surfaces are convex or slightly flattened. The root, like the crown, exhibits mesial and distal surfaces which converge toward the lingual. Thus, the labial root surface is w ider mesiodistally than the lingual root surface.

d. In cross section at the neck, the root is roughly ovoid, with convex labial and lingual outlines, but with mesial and distal outlines which are flattened or only slightly convex. Furthermore, the outline is wider mesiodistally at the labial than at the lingual. The mid root section is similar, except that the mesial and distal outlines are most likely to be convex.

10. Variations and Anomalies:

a. Crown form does not vary widely, although the sharpness of the cusp tip has considerable range.

b. On rare occasions, the lingual surface may exhibit a tubercle which is located near the most incisal level of the cingulum. When a tubercle is present, a lingual pit is often associated with it.

c. Root form is subject to variations. There may be several curvatures along its length. If curved in the apical third, the deflection is most commonly to the distal.

d. Since the maxillary canine normally erupts after the maxillary premolars, its space is sometimes partially closed. It may then erupt well to the labial or lingual of the other teeth, or not erupt at all, in which case it is considered to be impacted.

C. Permanent Mandibular Canine:

1. General characteristics:

a. Arch position - The mandibular canine is the third tooth from the midline in each lower quadrant, and is the replacement for the deciduous mandibular canine. The mesial contact is shared with the mandibular lateral incisor, while distally it contacts the mandibular first premolar.

b. Universal Number: Mandibular right canine - #27 Mandibular left canine - #22

c. General form and function - Form and function are similar to those of the maxillary canine.

2. Comparisons with the maxillary canine:

a. The crown is as long, or longer incisocervically, when compared to the maxillary canine.

b. The mesiodistal and labiolingual dimensions of both crown and root are normally less in the mandibular canine.

c. The root is usually shorter than the maxillary canine's, but in some cases, may be as long. The total crown plus root length is approximately the same for the two canines.

d. The lingual surface and its structures are less well developed than in the maxillary canine. In fact, the form of the lingual surface is more closely allied to that of the mandibular incisors, even with the presence of a lingual ridge.

e. The cusp of the mandibular canine is not so well developed, nor is its tip normally as sharp mesiodistally as in the maxillary canine.

f. The labial surface is generally not so convex as in the maxillary canine. This is especially true in the incisal two-thirds of the surface. However, it may be more convex mesiodistally in the cervical third.

3. Development Table: (Mandibular canine)*

Initiation of calcification 4 to 5 months

Completion of enamel 6 to 7 years

Eruption 9 to 10 years

Completion of root 12 to 14 years

Labial aspect:

a. General considerations - Even though the dimensions differ, the general outline of the tooth from the labial aspect is pentagonal, like the maxillary canine. As pointed out, the labial surface is generally not so convex (except mesiodistally in the cervical third) as the maxillary canine, but is generally more convex than in the mandibular incisors.

b. Mesial outline - The mesial outline is pretty much a straight line from the mesial contact to the cervical line, with an obtuse mesioincisal angle. The crest of curvature of this margin is near the mesioincisal angle, and is associated with the contact area in the incisal third.

c. Distal outline - Distally, the outline is convex incisocervically, with a more rounded distoincisal angle. The distal margin is shorter than the mesial margin. The height of contour, which is associated with the contact area at the junction of the incisal and middle thirds, is more cervically located than on the mesial outline.

d. Incisal outline - The cusp is not as long or the tip as sharp as the maxillary canine cusp. The distoincisal slope is normallyJonger, and its angulation cervically is much steeper than the mesioincisal slope exhibits.

Since the distoincisal slope of the mandibular canine normally occludes with the mesioincisal slope of the maxillary canine, the wear pattern is reflected in a mesial displacement of the cusp tip of the mandibular canine, and a lengthening of its distoincisal slope. However, prior to attrition, the cusp tip is located directly over the root center, as in the maxillary canine.

e. Cervical outline - The cervical line is evenly curved toward the root.

f. Other considerations - The labial surface appears to be much longer incisocervically than the maxillary canine, and in fact, it is as long, or slightly longer. However, the main reasons for this appearance are its narrower mesiodistal dimension, and the more incisal location of the contact areas.

The labial ridge is not as prominent as in the maxillary canine. Developmental depressions are positioned and named like those of the incisors and maxillary canine, but imbrication lines are normally absent.

The labial height of contour is located in the cervical third.

Lingual aspect:

a. Mesial, distal, and incisal outlines - These margins mimic those of the labial aspect.

b. Cervical margin - The cervical line exhibits a greater depth of curvature than on the labial, and it is uneven, with the greatest curvature offset to the distal.

c. Other considerations - The lingual surface is generally smoother and lacking in anatomic detail, when compared to the maxillary canine. The cingulum does not extend so far incisally, and it and the marginal ridges are not so prominent. There is normally a less pronounced lingual ridge, and shallow distolingual and mesiolingual fossae usually occur in the incisal portion of the surface. There are rarely any grooves, pits, or tubercles on the lingual surface.

As is the case with other anterior teeth, the lingual surface is slightly narrower mesiodistally than the labial surface.

The lingual height of contour is associated with the greatest prominence of the cingulum in the cervical third.

6. Mesial aspect:

a. Labial margin - The entire labial outline is convex, with the greatest rounding at the height of contour in the cervical third.

b. Lingual margin - The lingual outline is similar to that of the maxillaiy canine, except the cingulum convexity is less prominent and located farther cervically.

c. Incisal margin - The outline of the incisal ridge is thinner labiolingually.

d. Cervical margin - The CEJ is quite evenly curved incisally.

e. Other considerations - The mesial surface is roughly triangular in shape like the maxillary canine, but noticeably narrower labiolingually. The surface contour is basically convex labiolingually, but incisocervically there is usually a flattening between the cervical line and the contact area.

The contact area is located in the incisal third, about midway between the labial and lingual surfaces. It is ovoid, and wider incisogingivally than labiolingually.

7. Distal aspect:

a. The distal is similar to the mesial surface in all respects, except that it is slightly smaller in all dimensions.

b. The contact area, and thus the height of contour, are found at a more cervical level at the junction of the incisal and middle thirds. It also has a different outline which approaches a circular shape.

c. There is no incisocervical flattening on the distal surface, as there is on the mesial surface.

8. Incisal aspect:

a. Although the relative dimensions differ, this tooth is similar to the max-D illary canine, when viewed from the incisal. The crown is thicker labiolingually toward the mesial, and the cingulum is offset to the distal. The labial outline is more convex mesiodistally than in the mandibular incisors.

a. The root is normally single, fairly straight, and the longest root in the" mandibular arch.

b. Like most other anterior teeth, it is narrower mesiodistally than labiolingually. The lingual portion is narrower mesiodistally than is the labial. Both labial and lingual surfaces are convex, while the mesial and distal surfaces are flattened or concave. When concavities are present, they extend cervicoapically along the root, and in some cases run the entire root length. As in the mandibular incisors, they are named root concavities, or longitudinal grooves.

c. In cross section at the neck, the outline is roughly a flattened ovoid, wider labiolingually, and wider mesiodistally at the labial than the lingual. If root concavities are present, the proximal outline will be concave. The mid root section is similar, but the mesial and distal surfaces are more likely to be flattened rather than concave.

10. Variations and Anomalies:

a. Crown form is not greatly variable.

b. Irregularly curved roots axe occasionally seen, and bifurcated roots, with labial and lingual branches, are also possible.

Comparison of Incisal Slopes In Newly Erupted and Worn Canines

Maxillary Right Canine Newly Erupted

Distoincisal Slopes

Distoincisal Slopes

Mesioincisal Slopes

Mandibular Right Canine Newly Erupted

Incisal Relation During Occlusion

UNIT #5

Reading Assignment:

Unit # 5 (The Permanent Maxillary Premolars) Specific Objectives:

At the completion of this unit, the student will be able to:

A. List the appropriate age(s) concerning the developmental chronology of the maxillary premolars found in the development tables, or select the appropriate age(s) from a list, when given a certain developmental feature. The student should also be able to compare these facts between the maxillary premolars.

B. Demonstrate a knowledge of the morphology of each surface of the crown, as well as the root, of each permanent maxillary premolar by:

1. describing,

2. selecting the correct information from a list,

3. or interpreting a diagram to identify or name any of the following features:

a. Contours of any surface, or margin of any surface.

b. Structural entities such as grooves, pits, ridges, inclined planes, cusps, fossae, lobes, etc.

c. Height of contour and contact areas.

d. Relative dimensions and shape.

e. Any other surface feature.

Furthermore, the student will be able to make comparisons of any of these features between the maxillary premolars.

C. Make comparisons between maxillary premolars and other permanent teeth, where appropriate, by selecting the correct response from a list.

D. Make comparisons between the general characteristics of the maxillary premolars, including function, arch position, distinguishing features, etc., by describing them, or selecting the correct response from a list, when given the tooth (teeth), or a description of the general characteristic(s).

E. Determine from a diagram or description whether a given maxillary premolar is first or second, or right or left.

F. Determine the correct universal number or Palmer notation for a given diagram or description of any maxillary premolar.

G. Demonstrate a knowledge of any of the new terms in this unit by defining them, or selecting the correct definition, or application thereof, from a list, when given the term, or any of its applications.

H. Demonstrate a knowledge of any of the variations or anomalies in this unit by describing them, or selecting the correct response from a list, when given the particular tooth (teeth), the anomaly, or any of its features or applications.

The student is also responsible for any material which was to have been mastered in previous units.

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