Permanent maxillary canine l tooth crown & root morphology revision for dental students

 

Morphology of Maxillary Canine

Labial Aspect

1. Canines possess four developmental lobes when viewed from the labial aspect - three labial lobes of which middle lobe develops into prominent labial ridge and one palatal lobe develops into a prominent cingulum. Vertical developmental depression are seen mesial and distal to the labial ridge of the crown.
2. Crest of the labial ridge will curve slightly toward the mesial side of the crown. Cuspal tip is located mesial to the mesiodistal long axis giving an impression of short mesial slope and longer distal slope.
3. Mesial aspect of the crown appears convex in the middle third and becomes flatter in the cervical third of the crown. Distal aspect of the crown appears convex in the middle third and slightly concave in the cervical third of the crown (“S” shaped).
4. Mesial contact area appears at the level of the junction of the incisal and middle third of the crown. Distal contact area is usually near the middle of the middle third or junction of incisal and middle third of the crown (mesial cuspal ridge appears shorter than distal cuspal ridge due to above difference in the positioning of the contact areas).
5. Crown converges evenly (at the same rate, mesially and distally) from the contact areas to the cervical line. This gives an illusion that the crown is “balanced” under its root.
6. Crest of the cervical line apically will be slightly distal to the mesiodistal long axis bisector of the crown.
7. Exhibits longest roots among all human teeth. Conical and slender root may remain straight or may curve in usually toward the distal aspect (distal tilt) with a sharp apex.
8. Overall, the crown and root of maxillary canine appears narrower mesiodistally as compared to the incisors.

Palatal Aspect

1. Palatal outline is inverse of the labial outline of the crown.
2. Crest of this palatal ridge appears similar to the labial aspect of the crown. Distal marginal ridge appears smaller than mesial marginal ridge.
3. Two palatal fossae “mesiopalatal fossa” and the “distopalatal fossa” are separated by the palatal ridge which connects the cusp tip and the cingulum.
4. Smooth well developed cingulum appears like another cusp on the palatal aspect of the crown. Cingulum is presented centred or slightly distal to the mesiodistal long axis bisector of the crown.
5. Crown and root taper lingually than labially. Cingulum, marginal ridges and cingulum remain prominent on this aspect of the crown. Less evidence of any supplemental groves.
6. Long and narrow palatal root with the presence of developmental depression on the mesial and distal aspect of the root is seen. As the root is very narrow lingually, portion of mesial and distal aspect of the tooth can also be seen.

Mesial Aspect

1. Wedge shaped outline of the crown with its cusp tip centred labial to the labiopalatal long axis of the tooth.
2. Crown when viewed from the mesial aspect looks wider with greater bulk present labiopalatally.
3. Labial outline between the cervical ridge and cusp tip is smoothly convex. Palatal outline will exhibit a convex cingulum and the crest of the palatal ridge with intermittent concave palatal fossa.
4. Labial and palatal cervical ridges are well developed and their crests oppose one another at the cervical third of the crown.
5. Cervical line on the mesial aspect of the tooth appears to extend incisally more on the mesial surface than on the distal surface.
6. Root and cusp tip are in line with each other located labial to labiopalatal bisector of the tooth. Broad root (labiopalatally) with blunt apex and palatal convergence is prominent. Shallow developmental depression is present on the mesial aspect of the root.

Distal Aspect

1. Features on the distal aspect remains similar to the mesial aspect of the tooth.
2. Distal marginal ridge appears irregular and prominent. Prominent concavity is seen usually above the distal contact area.
3. Cervical line curves less incisally on the distal surface than it does on the mesial surface of the crown.
4. Root morphology appears almost similar to the mesial aspect. Deeper developmental depression is seen on the distal surface of the root.

Incisal Aspect

1. Diamond shaped incisal outline with wider labiopalatal dimensions of the crown.
2. Cusp tip is positioned slightly labial to the labiopalatal bisector & slightly mesial to the mesiodistal bisector of the crown. Sometimes, it may be centred within the crown outline. Mesial portion of the tooth appears narrow while the distal portion appears to be stretched.
3. Cingulum appears to be located at the centre mesiodistally.
4. Cuspal ridges are generally in line with one another across the tooth mesiodistally.
5. Distal end of the distal cuspal ridge is likely to be a little palatal to the mesial end of the mesial cuspal ridge (Both cuspal ridges comprise the incisal ridge)
6. Labial outline is convex and rounded. Mesial half of the labial outline appears convex while distal half of the labial outline of the crown appears concave.
7. Palatal outline is convex from the mesial contact area to the crest of the cingulum than it is between the cingulum and the distal contact area. Thin distal lobe causes a concavity in the palatal outline of the crown. The crest of the palatal outline will be slightly distal to the mesiodistal bisector giving a wider mesial half appearance.

Steps in Carving of Maxillary 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 Palatal – P

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 palatal 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-palatal 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 palatal aspects of the crown (remove more wax on the middle and incisal third of the tooth to maintain the convexity on the cervical third and create palatal fossa on the palatal side)

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 palatal aspect in 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. More labio-palatal dimension  , Note: Two areas concavities need to be given – Incisal aspect

1. Distal slope at the Incisal edge
2. Distal region of the labial aspect of the tooth – This gives the tooth a prominent labial ridge and a stretched distal area.

• 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. Distal contact area is placed slightly higher than mesial contact area.

• 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 palatal aspect as shown in the picture.

• Step 12: Remove the wax on the labial aspect of the crown – As shown in the picture. Also, remove more wax on the sides of the labial aspect than the central portion of the crown.

• Step 13: Draw a midline on the palatal aspect of the crown. Mark a u shaped fossa on either side of the midline as shown in the picture. (Leave about 1 mm from the marginal ridge)

• Step 14: Remove the wax from the shaded portion of the crown on the palatal 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 palatal aspect of the crown appears like this

• Step 16: Mark the outline of the root portion of the tooth on the labial and palatal portion of the tooth. Reduce from the mesial and distal aspects of the block. Reduction is made more on the palatal side of the tooth. Finally, make a distal 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.

1. Reduce from the labial and palatal aspects of the block
2. Make developmental depressions on the mesial and distal aspects of the tooth. (Distal aspect depression appears more deeper than mesial aspect)

• Step 18: Mark the cervical line on the labial, palatal, 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 except keeping the mesio-incisal angle alone sharp.
• Polish each side of the tooth with a soft cloth and soap water.