Permanent mandibular canines l tooth crown & root morphology revision for dental students

Permanent mandibular canines l tooth crown and root morphology revision for dental students

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comparison between maxillary and mandibular canine :

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Morphology of Mandibular Canine

Labial Aspect

1. Mandibular canine is long (cervico incisally) and narrow (mesiodistally) as compared to the maxillary canines. However, the crown and root appears narrow labiolingually.
2. Labial surface of the crown appears smooth with a less pronounced labial ridge and vertical depressions mesial and distal to it.
3. Overall, the mesial outline of the crown, from contact area to cervical region is straight while the distal outline of the crown , from the contact area to the cervical region, reflects a concavity in the cervical third and convexity in the incisal third of the tooth.
4. Cusp tip will appear less pointed and remain positioned mesial to the long axis of the tooth. This gives an illusion of shorter mesial cuspal ridge than distal cuspal ridge.
5. Mesial proximal contact is located at the incisal third of the crown below the mesioincisal angle while the distal proximal contact is located at the junction of middle and cervical third of the crown . (at different levels)
6. Cervical outline appears semi-circular with prominent distal curvature.
7. Overall, convex root tapers evenly from the cervical line for two thirds of the root length and curves mesially or distally in the apical third of the tooth.

Lingual Aspect

1. Lingual outline will be the inverse of the labial outline of the crown. Crown appears more narrower and placed lingually as compared to the maxillary canine.
2. Overall, the anatomic features, like cingulum, marginal ridges and lingual fossa appear more poorly developed when compared to those of the maxillary canine.
3. Crest of the cervical line will be distal placed in relation to the mesiodistal axis of the tooth.
4. Presence of developmental depressions on the mesial and distal aspects of the narrow tooth root.

Mesial Aspect

1. Wedge shaped outline of the crown with lesser labiolingual dimensions of the crown.
2. Incisal ridge and cusp tip of the mandibular canine appears slender and is present lingual to the labiolingual long axis. Distoincisal angle also appears to be lingual to the distolingual axis of the tooth.
3. Labial outline from the cervical ridge to the cusp tip is slightly convex while the lingual outline from the cingulum to the cusp tip region is concave (cingulum is less pronounced)
4. Crest of curvature on the buccal and lingual surfaces are located on the cervical region of the tooth (same level). Mesial contact area is centred labiolingually within the incisal third of the crown.
5. Cervical line curves incisally more towards the mesial surface of the crown.
6. Convex root with an even which tapers to a pointed apex that is centred labiolingually. Deep developmental depression is present on the mesial aspect of the tooth.

Distal Aspect

1. Distal outline will be the inverse of the mesial outline.
2. Distal contact area is presenting cervical to the junction of the incisal and middle thirds of the crown.
3. Cervical line curves less incisally on the distal surface of the tooth.
4. Anatomical features of the root appear similar to the mesial surface of the tooth.

Incisal Aspect

1. Crown appears larger labiolingually when viewed from the incisal aspect of the tooth. Labial outline with respect to the mesial portion appears convex while distal portion shows mild degree of concavity.
2. Overall, the tooth shows lingual convergence. Crest of the cingulum will be slightly distally placed in relation to the mesiodistal bisector.
3. Cusp tip will always be lingual to the labiolingual bisector of the tooth. More prominently, the distal end of the distal cuspal ridge appear lingually exhibiting a distolingual twist (mesial marginal Ridge  >  distal marginal ridge). Both cuspal ridges combine to form the incisal ridge.

Steps in Carving of Mandibular Canine

• Step 1: Draw a mid-line on all 4 sides of the wax block and divide the block as shown in the diagram (crown and root length)
• Step 2: Mark the five aspects of the tooth as Labial – L, Mesial – M, Distal – D, Incisal – I and Lingual – Li

Carving –Labial Aspect

• Step 3: Mark the mesio-distal dimensions of the crown and at cervix. Join the points as shown here on the labial and lingual aspects of the crown

• Step 4: Remove the shaded portion of the block from the mesial and distal aspects of the crown

Carving – Proximal Aspect

• Step 5: Divide the crown into three equal thirds (cervical, middle and incisal third) from above to below on all sides and mark the labio-lingual dimension of the crown on the mesial and distal aspects as shown

• Step 6: Remove the shaded portion of the tooth from the labial and lingual aspects of the crown (remove wax more on the middle and incisal third of the tooth to maintain the convexity on the cervical third and create lingual fossa on the lingual side. Lingual outline must be 1 mm away from the midline.

Carving – Incisal Aspect

• Step 7: View the incisal aspect of the tooth with the central incisal ridge

• Step 8: Mark lines as shown here up to 1 mm from the edge of the incisal ridge to the lingual aspect and the labial aspect of the crown

• Step 9: Remove wax from the shaded portion of the tooth in order to obtain the palatal convergence and smooth rounded labial surface.

• Note: Two areas concavities need to be given – Incisal aspect Distal slope at the Incisal edge Distal region of the labial aspect of the tooth This gives the tooth a less prominent labial ridge and a stretched distal area.

Shaping and Contouring of the Crown

• Step 10: Mark a central line on the labial aspect of the crown which later forms the labial ridge. (Note that the central line is slightly curved with the convexity towards the mesial side.) Mark the mesial and distal slopes on the incisal aspect of the crown as shown in the picture. Note that the mesial slope is shorter than the distal slope and these slopes extend to the junction between incisal and middle third.

• Step 11: Remove the wax from the cervical portion to the incisal aspect of the crown leaving the central portion of the crown till a prominent labial ridge is visible. Remove the shaded portion of the crown from the labial and lingual aspect as shown in the picture.

• Step 12: Remove the wax on the labial aspect of the crown as shown in the picture (remove more wax on the sides of the labial aspect than the central portion of the crown).

• Step 13: Draw a midline on the lingual aspect of the crown. Mark a u shaped fossa on either side of the midline as shown in the picture

• Step 14: Remove the wax from the shaded portion of the crown on the lingual aspect thus maintaining the cingulum and palatal ridge also. (Sharp end of the carver is used initially followed by the scooped end of the carver to obtain a smooth surface)

• Step 15: Finally, the lingual aspect of the crown appear like this . (Less well developed cingulum, fossa and marginal ridges)

• Step 16: Mark the outline of the root on the labial and palatal portion of the tooth.

1. Reduce the tooth from the mesial and distal aspects of the block
2. Reduction is made more on the lingual side of the tooth
3. Mesial outline appears straight from crown to root.
4. Finally, make a mesial tilt in the apex of the root portion of the tooth

• Step 17: Mark the outline of the root portion of the tooth on the mesial and distal portion of the tooth. Reduce from the labial and lingual aspects of the block. Mesial developmental depression is more prominent than distal developmental depression
• Step 18: Mark the cervical line on the labial, lingual, mesial and distal aspect of the tooth . Cervical constriction – Remove wax to a small extent above and below the cervical line

Final Step

• Draw the cervical line and cervical constriction with the adequate measurements on all sides of the crown
• Provide a smooth finish to remove sharp edges
• Polish each side of the tooth with a soft cloth and soap water.