GENERAL FEATURES OF CANINES

  • The canines – two maxillary and two mandibular – bear a close resemblance to each other. They are the longest teeth in the mouth and placed at the corners of the mouth and therefore referred to as the corners stones of the mouth.
  • The canines are well anchored in the bone by their extremely long roots. The crown is bulkier than that of the incisors, and the middle labial lobe is highly developed incisally forming a strong well formed cusp and labial ridge.
  • The crowns and roots of the canines are markedly convex on most surfaces. When viewed from the proximal aspects they show a triangular shape, however, from labial and lingual aspects they take pentagonal shape.
  • The position and form of these teeth and their anchorage in the bone, along with a bone ridge over the labial portion of the root, called “canine eminence”, have a osmotic value and ensure facial expression. In function the canines support the incisors and premolars in holding and tearing the food material.

 

MAXILLARY CANINE

The crown and root of the maxillary canine are narrow mesiodistally than the central incisor. The cervico-incisal length of the crown is much longer than any other anterior tooth, with the exception of the maxillary central incisor. Table V list the chronological data of maxillary canine.

The mesial half of the crown of the maxillary canine resemble a portion of an incisor and contact with lateral incisor. The distal half, on the other hand, resembles a portion of a premolar and contact the first premolar. The incisal portion of the crown is thicker labiolingually then that of the incisors, and the cingulum shows greater development.

Labial aspect

  • It is pentagonal in outline. The mesial outline is convex from the cervix to the center of the contact area at the junction between the middle and incisal thirds of the crown.
  • The distal outline between the cervical line and the distal contact area which is situated at the center of the middle third. The mesial contact area is at a lower level than the distal.
  • The cusp has a mesial and distal slopes. The mesial one is shorter and shows tendency toward concavity, while the distal slope shows tendency toward convexity. The cervical line is convex root wise. Faint mediolabial and distolabial developmental grooves can be seen.
  • The labial surface is smooth except for a shallow depression mesially and distally dividing the crown into its three labial lobes. The middle lobe is more developed than the other two which result in formation of a ridge on the labial surface , the labial ridge, which runs from the cervical line to the tip of the cusp in a curved manner inclined mesially at its center. The areas mesial to the crest of this ridge exhibits convexity while area distal to it tends toward concavity.
  • The root appears slender form the labial aspect and is conical with blunt apex. The root may show either mesial or distal curvature, mostly distal, near the apex. The labial surface of the root is smooth and convex.

Lingual aspect

  • The crown and root are narrower lingually than labially. The cervical line from is less convex than on the labial surface. Below the cervical line is a well developed cingulum. The mesial and distal marginal ridges are strongly developed.
  • The area incisal to the cingulum is concave forming the lingual fossa. Very often the  lingual fossa show a well developed lingual ridge extending from the cusp tip to a point near the cingulum dividing the lingual fossa into mesial and distal.
  • The root is narrow when viewed from the lingual aspect than the labial and is smooth and convex.

Mesial aspect

  • The outline of the crown is wedge shaped with the greatest measurement at the cervical third. The wedge point at the tip of the cusp. The labial outline is more convex from the cervical line to the cusp tip than any other maxillary anterior tooth. The lingual outline is convex below the cervical line, representing the cingulum then continue as a straight line curves toward the cusp.
  • The relation of the tip of the cusp to the long axis of the root is different from that of maxillary incisors. A line bisecting the cusp is on long axis of the tooth or labial to it.
  • The mesial surface of the crown is convex at all points except for small circumscribed area above the contact area where the surface is concave of flat to the cervical line.
  • The outline of the root is conical with tapered blunt or pointed apex. The root may curve labially at apical third. The mesial surface of the root appears broad with a shallow developmental depression for part of the root length which helps to anchor the tooth to the alveolus and prevent rotation.

Distal aspect

This aspect is similar to the mesial aspect except that the cervical line shows less curvature toward the cusp tip. The distal marginal ridge is heavier and more irregular than the mesial one and the contact area is more cervically located  in the middle third. In addition, the surface is more concave above the contact area and the developmental groove is more pronounced.

Incisal aspect

The labiolingual dimension is greater than the mesiodistal dimension. The cusp tip is labial and mesial to the center of the crown. The ridge of the meddle labial lobe is very noticeable from the incisal aspect. It attains its greatest convexity at the cervical third of the crown, becoming broader and flatter at the middle and incisal thirds.

Pulp cavity

  • It consists of the pulp chamber and a single root canal. Labiolingual section shows a narrow pulp chamber that points incisally. The root canal is wide in the cervical half of the root than any other tooth. The canal then narrows to average width on its way to the apical foramen.
  • On mesio-distal section the pulp cavity is much narrower and similar to those of the incisors. It has much longer and tapered root canal.
  • On cervical cross section the pulp cavity appears even narrower and the root canal is eleptical rather than round and centered over the root. The canal is wider labiolingually than mesiodistally.

 

MANDIBULAR CANINE

The mandibular canine resembles the maxillary one in that they have the same wedge shaped outline, long crown and a well developed cingulum. They differ fro the maxillary canine, however, in some aspects. Table VI lists the chronological data of mandibular canine.

Labial aspect

The difference between the mandibular and maxillary canines are:

  • The crown is narrower mesiodistally by about o.5 mm than the maxillary one. Labiolingually the crown and root is slightly less than those of the maxillary canine.
  • The length of the mandibular canine is similar to the maxillary canine, but the crown is longer by 1 mm and the root is shorter by 1 mm. the effect of greater crown length is emphasized by the narrowness of the crown mesiodistally and the height of the contact area above the cervix. 
  • The mesial outline of the crown is nearly straight with the mesial outline of the root. The mesial contact area is near the mesioincisal angle.
  • The distal outline is convex cerivcoincisaaly with more rounded and obtuse distoincisal angle. It is shorter than the mesial outline and the contact area is located more cervically than the distal one but still more incisalo than the maxillary canine.
  • The cusp tip and ridges of the mandibular canine are not as well developed as the maxillary canine. The cusp tip is on the center of the root and the distal cusp slope is longer than the mesial one and inclined more cervically.
  • The cervical line is more symmetrically contoured than the maxillary one .
  • The crown surface is flat mesial and distal to the labial ridge at the incisal third. Crown outline is concave distally and convex mesially
  • The root is shorter by 1-2 mm than the maxillary canine and has a more sharply pointed apex that may be directed mesially of distally.

Lingual aspect

  • The lingual surface of the crown is flatter, smoother and regular simulating mandibular incisors. The cingulum and the ridges as well as the lingual fossa are less pronounced than in maxillary canine.
  • The lingual portion of the root is narrower than that of the maxillary canine, it is about one half or a little more in width than the labial portion.

Mesial aspect

  • The labial outline of the crown is less curved with the crest of the curvature at the cervical third. The lingual outline is also less curved. The cusp tip is centered over the root or slightly lingually inclined (that of the maxillary canine is labilly inclined).
  • The mesial developmental depression on the root is more pronounced and sometimes the root is bifurcated at the apical third.

Distal aspect

There is little difference between distal and mesial aspect which are:

  • The distal marginal ridge is more pronounced than the mesial
  • The cervical line has less curvature.
  • The distal contact area is more cervical.
  • More pronounced developmental depression on the root.

Incisal aspect

The outline of the incisal surface is less curved than in the maxillary canine. The cusp tip, mesial cusp ridge and the contact area are inclined lingually, while those of the maxillary canine extends nearly a straight line mesiodistally. The cingulum is shifted distally.

Pulp cavity

Pulp cavityiy is similar to that of the upper canine but smaller. The root may show one or two root canals - labial and lingual canal - that join at the apex.or have separate foramina when the root is bifurcated. There are always two canals. ■