Permanent canines l tooth crown & root morphology MCQs for dental students

Permanent canines l tooth crown & root morphology MCQs (multiple choice question) for dental students

PERMANENT CANINE ( tooth crown & root )

Maxillary Canine

Chronology

• Eruption >> 11-12 years.
• Root completed >> 13-15 years.

 

Labial aspect

• The geometric outline of the crownis trapezoidal in shape with short uneven side toward the cervical line and long uneven side toward the contact area.
• Mesial Outline: The mesial outline of the crown convex from the cervix to the center of mesial contact area. The mesial contact area is at the junction of middle and incisal third of the crown.
• Distal Outline: The distal outline of the crown is concave from cervical line to the distal contact area. The distal contact area is usually at the center of the middle thirds of the crown.
• Labial surface: It is smooth and ithas shallow depressions mesially and distally, dividing the labial surface into three labial lobes.                          
• The middle labial lobe shows much greater development than the other lobes.This produce a ridge on the labial surface of the crown [ labial ridge].                                  
• The cusp is on the line of the root. The cusphas a mesial slope and distal slope.                                                           
• The mesial slope is shorter than the distal slope. The mesial slopeis concave in its outline while the distal slope is convex.
• All areas mesial to the labial ridge exhibit convexity except for insignificant developmental lines in the enamel.              
• Distal to the labial ridge exhibit concavity at cervical third.         
• The cervical line labiallyis convex toward the root.
• The Root:It appear slender when compared with the bulk of the crown.                                                                                             
• It is conical in form with a quite pointed 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 is more convex than labially.
• The mesial and distal outlines are similar to the labial aspect.
• The cingulum is large and pointed like small cusp.
• There are well developed lingual ridge extend from the cusp tip to a point near the cingulum that divides the lingual fossa into two shallow concavities (lingual fossae).
• The lingual fossae present between the lingual ridge and the well developed marginal ridges.
• The Root: The lingual portion of the root is narrower than the labial portion. So, much of the mesial and distal aspects of the root are visible from the lingual aspect.
• Also, the mesial and the distal developmental depressions may be seen on most of these roots, extending most of the root length.

Mesial aspect

• The geometric outline of the proximal aspects is triangle in shape . The apex of the triangle is lying at the tip of the cusp.
• The Labial Outline: It is convex from the cervical line to the cusp tip with the crest of curvature at the cervical third [cervical ridge].
• The lingual outline: The lingual outline is convex in the cervical third (at the cingulum). Slightly concave at the middle third, then become convex again at the incisal third.
• The cusp tip is on the midline of the tooth or slightly labial.
• The mesial contact area is oval in shape, centered labiolingually and located at the junction of incisal and middle thirds.
• The mesial surface is convex except a small concave area between the cervical line and the contact area.
• Cervical line is curved toward the cusp.
• The Root: It is conical in shape with tapered apex. The root surface from the mesial aspect appears broad with shallow depression for a part of its length.
• This developmental depression on the heavy root help in anchoring the tooth to the alveoli and help in preventing rotation and displacement.

 

Distal aspect

• The distal aspect shows the same form as the mesial aspect, with the following variations:
• The cervical line exhibits less curvature toward the cusp tip.
• The distal marginal ridge is heavier and more irregular in outline.
• The distal contact area is more cervical in its level than the mesial contact area (distal contact area is lying in the center of the middle third).
• The surface displays more concavity above the contact area.
• The developmental depression on the distal side of the root is more pronounced.

 

Incisal aspect

• The labiolingual dimension is greater than the mesiodistal.
• The ridge of the middle labial lobe is very noticeable from incisal aspect.
• Lingually , a shorter arc than that described labially describes the outline of the cingulum.
• The two shallow lingual fossae are located lateral to the lingual ridge.

 

The pulp cavity of the maxillary canine

• Labiolingul section: The pulp cavity corresponds to the outline of the tooth . The size of the pulp chamber of this tooth is large. In the pulp chamber a long narrow projection (the pulp horn) presents . Then the root canal gently tapers from the pulp chamber toward the apex of the root.
• Mesiodistally section:The pulp cavity is much narrower in the mesiodistal section. The pulp cavity gently tapers from the incisal aspect to the apical foramen. The apical foramen is larger than incisors and presents at the tip of the root.
• Cervical cross section : The shape of the root and pulp cavity is oval or triangular.

 

Mandibular Canine

 Chronology

• Eruption >> 9-10 years.
• Root completed >> 12-14 years.

 

Labial aspect

• The essential differences between mandibular and maxillary canines viewed from the labial aspect may be described as follows:

1. The crown is longer and narrower mesiodistally than the maxillary canine.
2. The mesial outline of the crown is straight with the outline of the root.
3. The mesial contact area located at the incisal third near the mesioincisal angle.
4. The distal outline is convex with a more rounded disto incisal angle.
5. The distal contact area is slightly cervically (at the Junction of the incisal and middle thirds).
6. The cups tip is on a line with the center of the root. The mesial cusp slope is shorter than the distal cusp slope.
7. The cervical line labially curved root wise.
8. The root of mandibular canine is shorter and its apical end is more sharply pointed.

 

Lingual aspect

• It is flatter simulating the lingual surfaces of the mandibular incisors.
• The cingulum is smooth and poorly developed.
• The marginal ridges are less distinct.
• The lingual surface of the crown is smooth and regular. 

Mesial aspect

• The mandibular canine has less curvature labially and lingually than that of the maxillary canine.
• The cingulum is not as pronounced.
• The cusp appears more pointed and the tip of the cusp is slightly lingual to the center of the tooth.
• The contact area is located at the incisal third.
• The root from mesial aspect similar to the maxillary canine with the exception of a more pointed root tip.
• The mesial developmental depression on the root is more pronounced and quite deep.

 

Distal aspect

• The distal surface is similar to the mesial surface but it is slight smaller in all dimensions.
• The contact area is more cervically located.
• The cervical line is less curved than mesially.

 

Incisal aspect

• The mesiodistal dimension of the mandibular canine is less than the labiolingual dimension.
• The cusp tip is more likely to be inclined lingually.

 

The pulp cavity of the mandibular canine

• The pulp cavity of the mandibular canine is similar in its size and shape to the maxillary canine. 

Maxillary canines:

1. Also known as cuspids or CORNER TEETH OR EYE TEETH (as t hey develop near orbital floor).
2. Most commonly impacted teeth next to third molars.
3. The root is longest and strongest of all teeth.
4. Maxillary and mandibular canines are the longest teeth in oral activity
5. (Maxillary canine - Crown 10mm, root 17mm , Mandibular canine - Crown 11, root 16 mm)
6. These teeth exhibit longest path of eruption.
7. These teeth have maximum mesiodistal angulation (17°). Mesial half resembles incisors and distal half resembles premolars.
8. In canines and premolars (except maxillary first premolar) mesial slope is shorter than distal slope.
9. Least common tooth to slow bifurcated roots.
10.  It is the tooth, which is blocked out commonly due to lack of space.

 Mandibular canine:

•  Longest crown.
•  Among anterior teeth bifurcated roots and root canals are most common in mandibular canine.

 

Important points in canines

 

•  PRIMARY maxillary canine differ from PERMANENT maxillary canine in that -

1.    It has sharp pointed cusp tip.
2.     The mesial cusp ridge is longer than distal cusp ridge. 

•  Permanent MAXILLARY canine differs from permanent MANDIBULAR canine in that -

1.     Maxillary canine has more mesiodistal diameter.
2.    Contains well-developed cingulum as well as lingual fossa.
3.    The crown appears to be short with a long root.
4.    The cusp tip is labial to bisecting line.

 

•  RIGHT and LEFT MAXILLARY CANINES are distinguished by -

1.    Presence of more convexity on distal half than on mesial half.
2.    The distal cusp ridge is longer than mesial cusp ridge.

• MANDIBULAR RIGHT anot LEFT CANINES are distinguished by Shorter mesial cusp ridge, The mesial surface of mandibular canine is straight and is parallel to the long axis of crown.

• Teeth, in which the MESIAL CUSP RIDGE IS LONGER than distal cusp ridge are

1.     Primary maxillary canine.
2.    Permanent maxillary first premolar - facial cusp.

• Teeth in which the DISTAL CUSP RIDGE IS LONGER than mesial cusp ridge are

1.  Primary and permanent mandibular canine.
2.  Permanent maxillary canine.
3.  Permanent maxillary 2nd premolar.

•  Primary cusps of TRIGONE PATTERN are mesiobuccal, distobuccal and mesiolingual. Supplementary cusp or secondary cusp in trigone pattern is distolingual.

•  Mandibular incisor is bilaterally symmetrical when viewed both labially and incisally. The cuspal ridge is perpendicular to a line bisecting tooth. Because of these reasons, it is difficult to distinguish between the mesial and distal sides, and so the tooth cannot be differentiated into right or left.

•  Maxillary lateral incisor can be identified from mandibular lateral incisor by presence of deep lingual fossa.

•  Mandibular lateral incisor can be identified from mandibular central incisor in that The crown is bilaterally asymmetrical as the distal half of the crown appears to be stretched to make contact with mandibular canine.
• When viewed incisally, the distal portion of crown appears to be twisted lingually.
• The cervical line is more apically placed on the lingual side than on labial side.

•  The crown of mandibular canine appears to bend distally on its root base. This is an important feature to differentiate maxillary and mandibular canine.

•  The cusp tip of maxillary canine is labial to the center of crown labia lingually (cusp tip is present labial to the bisecting line) and mesial to the center mesiodistally. The cusp tip of mandibular canine is present lingual to the bisecting line.