MORPH: Exam 2

19 and #30

What are the Universal tooth numbers for the mandibular 1st molars?

First calcification: at birth → enamel complete: 2½–3 years → eruption: 6–7 years → root complete: 9–10 years

What is the developmental sequence and approximate timing of the mandibular 1st molar?

“6-year molar”; its eruption marks the beginning of the mixed dentition period

What nickname/eruption significance is associated with the mandibular 1st molar?

Largest and strongest tooth in the mandibular arch

How does the mandibular 1st molar compare with other mandibular teeth in size/strength?

Crown: 7.5 mm occlusocervically, 11 mm mesiodistally, 10.5 mm buccolingually; root: 14 mm

What are the average dimensions of the mandibular 1st molar?

Mesiodistal width is greater than buccolingual width

What important crown dimensional relationship should you know for the mandibular 1st molar?

5 lobes: 3 buccal and 2 lingual

How many developmental lobes form the mandibular 1st molar, and how are they distributed?

Mesiobuccal, distobuccal, distal, mesiolingual, distolingual

What are the five lobes/cusps of the mandibular 1st molar?

2 roots: mesial and distal

What is the usual root pattern of the mandibular 1st molar?

Mesial outline is slightly concave in the cervical third to the contact, then convex toward the occlusal

Describe the mesial crown outline of the mandibular 1st molar from the buccal view.

Distal outline is relatively straight from the cervical line to the convex contact area

Describe the distal crown outline of the mandibular 1st molar from the buccal view.

The occlusal portion is divided into three portions by two buccal grooves; cusp tips are relatively blunt and the distal cusp is lower and sharper

Describe the occlusal portion of the mandibular 1st molar from the buccal view.

Mesiobuccal and distobuccal developmental grooves

What two developmental grooves are visible on the buccal surface of the mandibular 1st molar?

The crown converges/tapers lingually

What important crown relationship is evident from the lingual aspect of the mandibular 1st molar?

Lingual cusps are more pointed than the facial cusps

How do the lingual cusps compare with the facial cusps on the mandibular 1st molar?

It separates the lingual cusps and terminates in the occlusal third

Describe the lingual developmental groove of the mandibular 1st molar.

The lingual cervical line is positioned more occlusally than the facial cervical line

How does the cervical line compare on the lingual vs facial surfaces of the mandibular 1st molar?

Only the mesiobuccal and mesiolingual cusps

Which cusps are normally visible from the mesial aspect of the mandibular 1st molar?

The root depression often extends onto the cervical third of the crown; the distal surface of the mesial root is also fluted

What root depression/fluting features are seen from the mesial aspect of the mandibular 1st molar?

Irregular with an occlusal deviation beneath the contact area

Describe the CEJ from the mesial aspect of the mandibular 1st molar.

Buccal HOC: cervical third

Lingual HOC: middle third

Where are the buccal and lingual heights of contour on the mandibular 1st molar?

The buccal outline is very convex in the cervical third; above the cervical ridge it may be slightly concave, flat, or slightly convex toward the MB cusp tip

Describe the buccal outline from the mesial aspect of the mandibular 1st molar.

MB cusp tip lies over the buccal third of the mesial root

Where is the mesiobuccal cusp tip positioned relative to the mesial root of the mandibular 1st molar?

All five cusps, the distal root, and part of the mesial root

What structures are visible from the distal aspect of the mandibular 1st molar?

The distal marginal ridge is lower/more cervical than the mesial marginal ridge

How does the distal marginal ridge compare with the mesial marginal ridge on the mandibular 1st molar?

The tooth tapers distally

How does the mandibular 1st molar crown change from mesial to distal?

The distal cusp is positioned more lingually than the distobuccal cusp

How is the distal cusp positioned relative to the distobuccal cusp on the mandibular 1st molar?

Distal root depressions are less pronounced than those on the mesial root

How do the distal root depressions compare with those on the mesial root of the mandibular 1st molar?

Relatively straight

Describe the cervical line from the distal aspect of the mandibular 1st molar.

Mesiobuccal > mesiolingual > distolingual > distobuccal > distal

What is the cusp-size order of the mandibular 1st molar from largest to smallest?

The crown is wider mesiodistally than buccolingually and tapers lingually

What are the major dimensional relationships of the mandibular 1st molar from the occlusal view?

The mesial half is broader buccolingually than the distal half

How does buccolingual width compare mesially vs distally on the mandibular 1st molar?

The central developmental groove lies lingual to the center of the crown

Where is the central developmental groove positioned faciolingually on the mandibular 1st molar?

Central, mesiobuccal, distobuccal, and lingual developmental grooves

What major developmental grooves should you recognize on the mandibular 1st molar?

Central fossa plus mesial and distal triangular fossae

What major fossae are present on the mandibular 1st molar?

Central, mesial, distal, buccal, and distobuccal pits

What pit locations should you recognize on the mandibular 1st molar?

2 roots with 3 or 4 canals; mesial root usually has 2 canals and distal root has 1 or 2

Describe the cervical cross-sectional root/canal anatomy of the mandibular 1st molar.

Five cusps; largest/strongest mandibular tooth; two widely separated roots; lingual taper; distal cusp smallest; MD > BL

What are the major identifying traits of the mandibular 1st molar?

18 and #31

What are the Universal tooth numbers for the mandibular 2nd molars?

First calcification: 2½–3 years → enamel complete: 7–8 years → eruption: 11–13 years → root complete: 14–15 years

What is the developmental sequence and approximate timing of the mandibular 2nd molar?

“12-year molar”

What nickname is commonly used for the mandibular 2nd molar?

Crown: 7 mm occlusocervically, 10.5 mm mesiodistally, 10 mm buccolingually; root: 13 mm

What are the average dimensions of the mandibular 2nd molar?

4 lobes: 2 facial and 2 lingual

How many developmental lobes form the usual mandibular 2nd molar, and how are they distributed?

Mesiobuccal, distobuccal, mesiolingual, distolingual

What are the four usual cusps of the mandibular 2nd molar?

2 well-developed roots: mesial and distal

What is the usual root pattern of the mandibular 2nd molar?

General outline is similar to the mandibular 1st molar, but the tooth is generally smaller

How does the mandibular 2nd molar compare overall with the mandibular 1st molar?

Lingual cusps are slightly longer and more pointed than the facial cusps

How do the lingual and facial cusps of the mandibular 2nd molar compare?

A facial developmental groove may contain a faulty pit and ends in the middle third

Describe the facial developmental groove of the mandibular 2nd molar.

The cervical ridge is more pronounced in the mesiofacial area and may extend onto the root

Where is the cervical ridge most pronounced on the mandibular 2nd molar?

Roots are shorter, closer together, and more distally inclined than those of the mandibular 1st molar

How do the roots of the mandibular 2nd molar compare with the mandibular 1st molar?

The mesial root is slightly twisted due to taper, but less than on the mandibular 1st molar

Describe the mesial-root twist of the mandibular 2nd molar compared with the 1st molar.

The crown has less of a bell shape than the mandibular 1st molar

How does the facial crown form of the mandibular 2nd molar compare with the mandibular 1st molar?

Crown and roots converge lingually, but less than on the mandibular 1st molar

How does lingual convergence of the mandibular 2nd molar compare with the mandibular 1st molar?

Very little of the mesial and distal surfaces is visible from the lingual view

How much of the proximal surfaces is normally visible from the lingual aspect of the mandibular 2nd molar?

The tooth does not taper lingually as much as the mandibular 1st molar

How does lingual taper of the mandibular 2nd molar compare with the 1st molar?

The cervical line is higher on the lingual than on the facial, but the crown is about the same length

How does the lingual cervical line relate to the facial cervical line on the mandibular 2nd molar?

Lingual developmental groove

What groove separates the two lingual cusps of the mandibular 2nd molar?

Very little occlusal surface is visible because of the height of the mesial marginal ridge

Why is very little occlusal surface visible from the mesial aspect of the mandibular 2nd molar?

The mesial root is broad, has a deep flute on its mesial surface, and is blunter than that of the mandibular 1st molar

Describe the mesial root of the mandibular 2nd molar from the mesial view.

Straight

Describe the cervical line of the mandibular 2nd molar from the mesial view.

The distofacial cusp may be visible because of its prominence

Which additional cusp may be visible from the mesial aspect of the mandibular 2nd molar?

Mesial HOC/contact: middle third; distal HOC/contact: middle third

Where are the mesial and distal proximal heights of contour/contact areas of the mandibular 2nd molar?

All four cusps

How many cusps are visible from the distal aspect of the mandibular 2nd molar?

Distal cusps and distal marginal ridge are lower/more cervical than the mesial

How do the distal cusps and marginal ridge compare with the mesial on the mandibular 2nd molar?

The distal contact is broader

How does the distal contact compare with the mesial contact on the mandibular 2nd molar?

The distal root is narrower buccolingually than the mesial root

How does the distal-root buccolingual width compare with the mesial root on the mandibular 2nd molar?

Root flutes occur on all root surfaces but are not as broad distally

Describe the root fluting of the mandibular 2nd molar.

Four cusps—MB, DB, ML, DL—are approximately equal in size

How do the four usual cusps of the mandibular 2nd molar compare in size?

The distal half of the crown is narrower than the mesial half

How does the distal half compare with the mesial half on the mandibular 2nd molar from the occlusal view?

Y pattern: the ML and DB cusp regions connect/touch and share a common fissure

What defines the Y fissure pattern shown for the mandibular 2nd molar?

the ML and DB cusp regions do not touch/share a common fissure

What defines the + fissure pattern shown for the mandibular 2nd molar?

Four approximately equal cusps; smaller than the 1st molar; less lingual taper; roots shorter/closer/more distally inclined; distal half narrower than mesial

What are the major identifying traits of the mandibular 2nd molar?

17 and #32

What are the Universal tooth numbers for the mandibular 3rd molars?

17–21 years

What is the eruption range for the mandibular 3rd molar?

40% have 4 lobes; 50% have 5 lobes; 10% have 6 or more lobes

What lobe-number variability is described for the mandibular 3rd molar?

Five-lobed form

What is the most common lobe-number form of the mandibular 3rd molar according to the lecture?

More likely to be impacted than the maxillary 3rd molar

How does impaction likelihood of the mandibular 3rd molar compare with the maxillary 3rd molar?

More bulbous and convex

How is the general crown form of the mandibular 3rd molar described?

Many supplemental grooves

What is characteristic of the occlusal surface anatomy of the mandibular 3rd molar?

Roots are shorter, more distally inclined, and likely to be fused

Describe the usual root characteristics of the mandibular 3rd molar.

Mesial HOC/contact: middle third; distal HOC/contact: middle third

Where are the mesial and distal proximal heights of contour/contact areas of the mandibular 3rd molar?

Statements 1, 2, and 4 are true. The 1st molar is larger, usually has 5 cusps, and has more widely separated roots; the 2nd molar roots are shorter, closer, and more distally inclined.

Which of the following statement(s) are TRUE regarding mandibular 1st and 2nd molars?

1. The mandibular 1st molar is generally larger than the mandibular 2nd molar.

2. The mandibular 1st molar usually has 5 cusps.

3. The mandibular 2nd molar has roots that are more widely separated than those of the 1st molar.

4. The mandibular 2nd molar roots are generally more distally inclined than those of the 1st molar.

Statement A is true and Statement B is false. The 1st molar tapers lingually; the 2nd molar also tapers lingually, but less—not more.

Determine whether the following statements are true or false.

Statement A — The mandibular 1st molar crown tapers lingually.

Statement B — The mandibular 2nd molar shows greater lingual taper than the mandibular 1st molar.

Statements 1, 3, and 4 are true. The usual mandibular 2nd molar has 4 cusps, not a distinct fifth distal cusp.

Which of the following statement(s) are TRUE regarding the mandibular 2nd molar?

1. Its four usual cusps are approximately equal in size.

2. A distinct fifth distal cusp is normally present.

3. The distal half of the crown is narrower than the mesial half.

4. Its roots are shorter and closer together than those of the mandibular 1st molar.

Statement A is true and Statement B is false. The central groove is lingual to center, but the crown is broader buccolingually mesially—not distally.

Determine whether the following statements are true or false.

Statement A — The central developmental groove of the mandibular 1st molar is positioned lingual to the center of the crown.

Statement B — The mandibular 1st molar is broader buccolingually than mesiodistally.

The mandibular 3rd molar. Its combination of bulbous crown, many supplemental grooves, marked variability, and likely fused roots is the key.

A mandibular molar is bulbous and convex, shows many supplemental grooves, and has short roots that are likely fused. Which tooth is most consistent with this description?

Statements 1, 2, and 3 are true; statement 4 is false. The distal half is not broader than the mesial half.

Which of the following statement(s) are TRUE regarding the mandibular 1st molar?

1. The lingual cusps are more pointed than the facial cusps.

2. The distal cusp is the smallest cusp.

3. The crown tapers lingually.

4. The distal half is broader buccolingually than the mesial half.

Both statements are true.

Determine whether the following statements are true or false.

Statement A — From the distal aspect of the mandibular 1st molar, all five cusps may be visible.

Statement B — From the distal aspect of the mandibular 2nd molar, all four cusps may be visible.

The mandibular 2nd molar. Four approximately equal cusps + less lingual convergence + a narrower distal half + closer roots favors the 2nd molar.

A mandibular molar has four approximately equal cusps, distal half narrower than its mesial half, and 2 roots (1 mesial, 1 distal). Which tooth is described?

Statements 1, 2, and 4 are true. The distal cusps are lower—not higher—than the mesial cusps.

Which of the following statement(s) are TRUE regarding the mandibular 2nd molar?

1. The distal root is narrower buccolingually than the mesial root.

2. The distal marginal ridge is lower than the mesial marginal ridge.

3. The distal cusps are positioned higher than the mesial cusps.

4. The distal contact is broader than the mesial contact.

Both statements are true.

Determine whether the following statements are true or false.

Statement A — The distal marginal ridge of the mandibular 1st molar is lower than the mesial marginal ridge.

Statement B — The distal cusps and marginal ridge of the mandibular 2nd molar are lower than the mesial.

Statements 1, 3, and 4 are true; statement 2 is false. Five lobes are more common than four lobes in the mandibular 3rd molar lecture data.

Which of the following statement(s) are TRUE regarding the mandibular 3rd molar?

1. Its anatomy is highly variable.

2. Four lobes are more common than five lobes.

3. Its crown is generally more bulbous and convex.

4. Its roots are often fused.

Statement A is false and Statement B is true. The 2nd molar shows less lingual convergence than the 1st.

Determine whether the following statements are true or false.

Statement A — The mandibular 2nd molar shows greater lingual convergence than the mandibular 1st molar.

Statement B — The mandibular 2nd molar crown and roots converge lingually less than those of the mandibular 1st molar.

A distinct fifth distal cusp (that feature favors the mandibular 1st molar, not the usual mandibular 2nd molar)

All of the following favor identification of a mandibular 2nd molar rather than a mandibular 1st molar EXCEPT one. Which is the EXCEPTION?

• Four approximately equal cusps

• Roots that are closer together

• Less lingual taper

• A distinct fifth distal cusp

Statements 1 and 4 are true; statements 2 and 3 are false. The mesial root is broader/deeper fluted, while the distal root is narrower buccolingually with less-broad fluting.

Which of the following statement(s) are TRUE regarding the roots of the mandibular 2nd molar?

1. The mesial root is broad and may show a deep mesial flute.

2. The distal root is broader buccolingually than the mesial root.

3. Root flutes are broader on the distal root than on the mesial root.

4. The roots are more distally inclined than those of the mandibular 1st molar.

Both statements are true.

Determine whether the following statements are true or false.

Statement A — The lingual developmental groove of the mandibular 2nd molar separates the two lingual cusps.

Statement B — Its facial developmental groove may terminate in the middle third and occasionally contain a faulty pit.

The mandibular 3rd molar.

A molar erupts around 17–21 years, is more likely to be impacted than its maxillary or mandibular counterpart, and commonly has short, distally inclined, possibly fused roots. Which tooth is described?

Statements 1, 2, and 3 are true; statement 4 is false. Root separation decreases rather than increases as you move posteriorly.

Which of the following statement(s) are TRUE when comparing mandibular molars?

1. The mandibular 1st molar is generally the largest.

2. The mandibular 2nd molar usually has 4 cusps.

3. The mandibular 3rd molar is the most variable.

4. Root separation generally increases from the 1st molar to the 3rd molar.

Statement A is true and Statement B is false. The 1st molar has more widely separated roots; the 3rd is more likely to have fused roots.

Determine whether the following statements are true or false.

Statement A — The mandibular 1st molar generally has more widely separated roots than the mandibular 2nd molar.

Statement B — The mandibular 3rd molar generally has the most widely separated roots of the three.

A Y pattern. The lecture defines Y when the ML and DB cusp regions connect/touch and share a common fissure; a + pattern is when they do not.

A mandibular 2nd molar occlusal diagram shows the ML and DB cusp regions contacting and sharing a common fissure. Which fissure pattern is represented?