Dental Anatomy Lec 5 PDF

Dental Anatomy Lec.5 Permanent Canines (Maxillary and Mandibular) There are four permanent canines: two in each dental arch and only one in each quadrant. General Characteristic Features of the Canines: 1. They are placed at the...

Dental Anatomy Lec.5 Permanent Canines (Maxillary and Mandibular) There are four permanent canines: two in each dental arch and only one in each quadrant. General Characteristic Features of the Canines: 1. They are placed at the “corners” of the mouth, which help in keeping facial expressions at the cosmetic value. 2. They are the most stable teeth in the mouth because of the followings:  They have large labio-lingual dimension.  They have long and wide root, which is well anchored in the alveolar bone.  The crown shape of the canine allows for “self-cleansing”, so they stay for longer time. 3. They develop from four lobes: Three labial and one lingual, their middle labial lobe is highly developed into well-formed cusp. 4. They are wider buccolingually than mesiodistally. 5. Marked convex labial outline, the labial surfaces have a labial ridge extending from the cusp tip to the cervical line. 6. Lingual aspect shows well-formed bulky cingulum and a lingual fossa, which may be divided by a lingual ridge into two small fossae. 7. Distal cusp slope is longer than the mesial cusp slope. 8. Typically have their contact areas at different levels cervico-occlusally. This is because the adjacent teeth of canines, with which they make contact, are of different classes (lateral incisor mesially and the 1st premolar distally). 9. Alveolar bone over the roots of permanent canine, from labial view, is prominent and is called canine eminence. 10. They have Single pointed cusp and single root, longest and strongest of all teeth providing the best anchorage among anterior teeth. 1  Functions: 1. The canines assist and support the permanent incisors and premolars in mastication since they are located between these groups. 2. Mainly used for tearing food, help in seizing, slicing and chewing food. 3. Are very important in esthetic. Principle identifying features: 1. Single pointed cusp. 2. The distal slope of the cusp is longer than the mesial slope. 3. Marked convex labial outline. 4. Bulky palatal cingulam. 5. Very long single root. The Permanent Maxillary Canine Labial Aspect: 1. Geometric shape: General shape of the crown from labial aspect is trapezoidal or pentagonal form. 2. The mesial outline of the crown is convex from the cervical line to the crest of curvature, which is located at the junction of the incisal and middle thirds. 3. The distal outline of the crown is slightly concave from the cervical line to the crest of curvature, which is located at the center of the middle third. 4. The distal slope of the cusp is longer than the mesial slope. 5. The cervical line is convex toward the root. 6. The labial surface is smooth except for a shallow depression mesially and distally dividing the three lobes, with the middle one much more developed producing the labial ridge. 7. The root is long and conical, with the apex curved distally. 2  Lingual Aspect: 1. The tooth is narrower lingually than labially (tapered lingually). 2. The cingulum in the maxillary canine is larger than that in the maxillary central and lateral incisors. 3. There is a well-developed lingual ridge confluent with the cusp tip, which divides the lingual fossa into two fossae. 4. There is a developmental depression mesially and distally extending for most of the root length. Mesial Aspect: 1. The labial and lingual outlines of the crown are more convex than that in the maxillary central and lateral incisors, with the crest of curvature (labially and lingually) located at the cervical thirds. 2. The curvature of the cervical line is 2.5 mm towards the cusp. 3. A line bisecting the cusp is labial to a line bisecting the root. 4. There is a developmental depression extending on part of the root. Distal Aspect: 1. The curvature of the cervical line is less distally than mesially (as in the maxillary central and lateral incisors). 2. The developmental depression of the root is more pronounced distally than mesially. 3  Incisal Aspect: 1. The labio-lingual dimension is greater than the mesio- distal dimension. 2. The ridge of the labial lobe is very noticeable labially, with its greatest convexity at the cervical third. 3. The cingulum is well developed and makes a small arc when compared with the labial outline which makes a large arc. 4. The tip of the cusp is labial to the center labio- lingually, and at or slightly mesial to the center mesio-distally. The Permanent Mandibular Canine Principle Identifying Features: 1. The mandibular canine is narrower mesio-distally and labio- lingually than the maxillary canine. 2. The lingual surface of the crown of the mandibular canine is shorter than that of the maxillary canine, with less developed cingulum and less prominent marginal ridges. 3. The cusp of the mandibular canine is not as well-developed as that of the maxillary canine. 4. The tip of the cusp is not in a line with the center of the root. 5. The mesial slope of the cusp is shorter than the distal slope. 6. The distal outline of the crown is more rounded than the mesial outline. 4 7. The mesial surface of the crown is nearly straight with the mesial surface of the root, with the contact area being near the mesio-incisal angle. 8. The distal contact area is located more incisally than the maxillary canine. Labial Aspect: 1. Geometric shape: The labial aspect of mandibular canine is trapezoidal or pentagonal like that of the maxillary canine. 2. The labial aspect reveals the major differences between the maxillary and mandibular canines. 3. The mesial outline is almost straight, in line with the mesial outline of the root and it joins the mesial cusp. 4. The maximum convexity of the mesial outline (The mesial contact area) is near the mesioincisal angle. 5. Distal outline is less convex than that of maxillary canine. 6. The distal contact area is more incisally located than that of maxillary canine. 7. The cusp tip is on line with vertical root axis. Cusp ridges are straight and the distal cusp ridge is longer than the mesial as in case of maxillary canine. 8. The cervical line on the labial surface curves apically. 9. Crown of mandibular canine appears longer, not only because of its extra length of 1 mm, but also due to its narrow mesiodistal width and more incisally placed contact areas. 10. Mesioincisal and distoincisal angles are well-defined. 11. The labial ridge running from cervix to the cusp tip is less prominent than that of the maxillary canine. 12. The crown appears to be tilted distally on the root base because of its straight mesial outline and curved distal outline. 13. When cusp tip is worn off, the tooth appears like a lateral incisor from labial aspect. 5  Lingual Aspect: 1. Geometric shape: It is trapezoidal like that of the labial aspect. 2. Crown outlines of lingual surface are similar to that of the labial aspect. 3. The lingual surface is narrower than the labial surface as the crown tapers lingually. 4. The lingual surface is less concave and more flattened similar to that of mandibular lateral incisor. The lingual fossa is shallow. 5. When lingual ridge is present, there are two small fossae, mesial and distal lingual fossae. The lingual ridge is also less well- developed than that of the maxillary canine. 6. The cingulum is poorly developed. 7. The marginal ridges are less prominent. Mesial Aspect: Some major differences between maxillary and mandibular canines are noted from this aspect. 1. Geometric shape: The mesial aspect has a triangular form with its base at cervix and apex at cusp tip. 2. The labial outline is less convex especially near the cervical line. 6 3. Lingual outline follows a less convex cingulum and less concave lingual fossa. 4. The cervical line shows more curvature incisally than that of the maxillary canine. 5. The cusp tip is in the center or lingual to the vertical root axis. 6. It can be remembered that cusp tip of maxillary canine is labial to the vertical root axis. The lower teeth show a lingual inclination over the root base. This conforms to the general rule that the upper teeth overlap the lower teeth in occlusion. Distal Aspect: It is similar to mesial aspect of mandibular canine except that: Cervical line is less curved on distal surface. Incisal Aspect: 1. Geometric shape: Oval. 2. Incisal aspect is similar to that of maxillary canine except the following features: A. Cingulum is smaller. B. Cusp tip and cusp ridges are lingually inclined. Whereas cusp ridges of maxillary canine extend straight to bisect the mesial and distal contact areas. 7