Permanent Mandibular Molars Question And Answers

The Permanent Mandibular Molars

Question 1. Describe in detail the morphology of the mandibular first molar.
Answer:

The mandibular first molar is the largest tooth in the mandibular arch.

• It has five well-developed cusps: two buccal, two lingual, and one distal.
• It has two well-developed roots, one mesial and one distal.

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Buccal aspects:

• The crown is roughly trapezoidal.
• The convex buccal surface presents 3 cusps mesiobuccal, distobuccal, and distal cusp with the tips of the lingual cusp.
• The mesiobuccal and distobuccal developmental grooves are seen.
• The buccal pit is present at the end of the mesiobuccal groove.
• The cervical line is almost straight.
• The cusps are relatively flat with less curvature of their ridges.
• The roots are well formed.
• The mesial root is curved mesially while the distal root is less curved.
• A deep developmental depression is present at the bifurcation.

Lingual aspect:

• Two lingual cusps and the lingual portion of the distal cusp are seen.
• A faint lingual developmental groove separates the mesiolingual and distolingual cusps.
• The cervical line is almost straight
• The mesial outline is convex while the distal outline is straight.
• The surface is smooth and spheroidal
• The bifurcation groove of the root trunk is located almost in line with the lingual developmental groove.

Mesial aspect:

• The mesiobuccal and mesiolingual cusps and the mesial root is seen.
• The crown is roughly rhomboidal and has a lingual tilt.
• The buccal cervical ridge is more prominent.
• The buccal outline is convex while the lingual outline is straight.
• The cervical line is irregular.
• The surface is convex and smooth.
• The mesial surface of the mesial root is convex.
• The mesial surface of the distal root is smooth, with no deep developmental depression.

Distal aspect:

• All five cusps are seen.
• The buccal and lingual surfaces of the crown converge distally.
• The distal marginal ridge is short and made up of the distal cusp ridge of the distal cusp and the distolingual cusp ridge of the distolingual cusp.
• The surface is convex.
• The cervical line may be irregular.
• A developmental depression is seen.
• The apical third of the root is more rounded.

Occlusal aspect:

• It is hexagonal
• It has five cusps: mesiobuccal, mesiolingual largest cusp, distobuccal, distolingual and distal cusps, the smallest cusp.
• The crown converges lingually

Fossae:

1. Major fossa:

• Central fossa- roughly circular.
  • Placed between buccal and lingual cusps ridges.
  • Bounded by the distal slope of the mesiobuccal cusp, both mesial and distal slopes of the distobuccal cusps, the mesial slope of the distal cusp, the distal slope of the mesiolingual cusp and the mesial slope of the distolingual cusp.

2. Minor fossa:

• Mesial triangular fossa.
  • Present distal to the mesial marginal ridge.
  • Bounded by the mesial slope of the mesiobuccal cusp, the mesial marginal ridge, and the mesial slope of the mesiolingual cusp.

Distal triangular fossa.

• Present mesial to the distal marginal ridge.
• Bounded by the distal slope of the distal cusp, the distal marginal ridge, and the distal slope of the distolingual cusp.

Groove:

• The central development groove, the mesiobuccal developmental groove, the distobuccal developmental groove, the lingual developmental groove, and supplemental grooves are seen on the occlusal surface.

Measurements:

• Cervico-occlusal crown length -7.5 mm
• Root length-14 mm
• Mesiodistal crown diameter-11 mm
• Mesiodistal crown diameter at cervix -9 mm
• Bucco-lingual crown diameter- 10.5 mm
• Bucco-lingual crown diameter at cervix -9 mm
• Curvature of cervical line – mesial -1 mm
• The curvature of the cervical line – distal – 0 mm

Question 2. Describe the morphology of the permanent mandibular second molar.
Answer:

• The mandibular second molar supplements the first molar in function.
• The crown has four well-developed cusps, two buccal, and two lingual.

Buccal aspect:

• It presents a buccal developmental groove separating mesiobuccal and distobuccal cusps.
• The roots incline distally.

Lingual aspect:

• Little of the mesial and distal surfaces are seen.
• The mesial and distal curvatures are seen.

Mesial aspect:

• The cervical ridge is less pronounced.
• The cervical line is straight
• The mesial root is pointed apically.

Distal aspect:

• The contact area is centered buccolingually.

 

Occlusal aspect:

• The buccal and lingual developmental grooves meet the central development groove.
• It is rectangular in shape.
• The distobuccal cusp ridge is present buccally to the mesiobuccal cusp ridge.
• It gives a 4-Y designation.

Measurements:

• Cervico-occlusal crown length – 7 mm
• Root length – 13 mm
• Mesiodistal crown diameter – 10.5 mm
• Mesiodistal crown diameter at cervix – 8 mm
• Bucco-lingual crown diameter – 10 mm
• Bucco-lingual crown diameter at cervix -9 mm
• Curvature of cervical line-mesial – 1 mm
• The curvature of cervical line-distal – 0 mm

Question 3. Write the differences between the permanent mandibular first molar and the mandibular second molar.
Answer:

 

Question 4. Write the differences between permanent maxillary 1st molar and mandibular first molar.
Answer: