Ch 10 Permanent Mandibular Premolars

Question 1

General Info

Answer 1

• have 4; 2 on right, 2 on left
• 1st pm: 4 lobes-1 large buccal cusp, small nonfunctioning lingual cusp (like canine)
• 2nd pm: 5 lobes-1 large buccal cusp, 2 smaller lingual cusp

Question 2

1PM Buccal:

1. crown
2. CA
3. Mesial
4. distal
5. cervix
6. root
7. surface

Answer 2

1. symmetrical bilaterally, trapezoidal
   - middle buccal well-dev
   - mesial cusp ridge < distal cusp ridge
2. broad, same level M&D, more than 1/2 distance fr cervical to cusp
3. straight, slight concave. slope, some concavity
   - buccal cusp: pointed, little mesial to center
4. slight concavity. slope, some concavity
5. narrow MD
6. 3 or 4mm < mand C
7. more convex than max PM
   - dev’t of middle buccal lobe is outstanding, dev’tal depressions often seen bet. 3 lobes
   - buccal ridge: continuous ridge fr cervical to cusp tip
   - smooth enamel

Question 3

1PM Lingual

2. cusp
3. surface
4. cervical
5. lingual cusp
6. root

Answer 3

• MD < buccal
  2. small, major portion is made middle buccal lobe
  3. most of occlusal can be seen, slopes cervically
  4. narrow, convex
  5. short, less dev, in alignment w/ BTR on occlusal
  6. narrower, ridge, smooth&convex. tapers evenly fr cervix to pointed apex.

Question 4

1PM Mesial

1. crown
2. buccal cusp
3. buccal
4. lingual
5. mesiobuccal lobe
6. cervical
7. crown surface
8. root

Answer 4

1. rhomboidal, overhang above root trunk in lingual direction
2. centered over root
3. crest of curve near middle third of crown
4. curved less convexity than buccal. crest @ mid 3
5. dev’t is prominent. harbors MLDG
6. curve occlusally
7. smooth, except MLDG
   - convex at CA, beneath its sharply concave
8. tapers, in line w/ buccal cusp tip. ling straight, bucc more curved. surface smooth, flt, display deep dev’tal groove, occasionally end in bifurc.

Question 5

1PM Distal

1. DMR
2. cervical
3. root

Answer 5

1. higher above the cervix, no extreme ling slope of MMR
   - major portion is convex, below & just above cervical is concavity
2. less curvature
3. mor convex, shallow dev’tal depression centered on root

Question 6

1PM Occlusal

1. crown
2. depressions
3. distal

Answer 6

1. diamond-shaped or circular
2. 2; mesial and distal fossae
   - M: more linear, contains MDG
   - D: more circular, contain crescent-shaped groov
3. larger arc and broader contact area
   - most of buccal surface can be seen.

• Characteristics common to all mand 1PM
  1. middle buccal lobe makes up bulk of crown
  2. buccal ridge prominent
  3. mesiobucc & distobucc line angles prominent, rounded
  4. CA broad
  5. crown converges sharply to center on lingual
  6. marginal ridges well-dev
  7. ling cusp small
  8. heavy buccal triangular ridge and a small ling triangular ridge

Question 7

2 PM Buccal

1. buccal cusp
2. CA

Answer 7

1. shorter than 1 PM, showing angulation of less degree
2. broader and higher

*tooth is larger
-2 forms:
three-cusp type=angular
two-cusp type=rounded
-single root is larger and longer than 1st PM

Question 8

2 PM Lingual

-Variations

Answer 8

1. lingual lobes developed to greater deg so cusps are longer
2. part of buccal portion of occlusal surface may be seen
3. Mesioling and distoling cusps are present, former being larger. a groove is between them.

• surface is smooth and spheroidal
• root is wide lingually and smoothly convex

Question 9

2 PM Mesial

-Variations

Answer 9

1. crown/root wider BL
2. buccal cusp not nearly centered over root trunk. shorter.
3. ling lobe dev greater
4. MMR is at right angles to long axis
5. less of occlusal seen
6. no MLDG present
7. root is longer
8. apex of root more blunt

Question 10

2 PM Distal

Answer 10

1. more occlusal seen, DMR is at a lower level than MMR

2. crown tipped distally (all post teeth)

Question 11

2 PM Occlusal

1. 3 cusp type
2. 2 cusp type
3. Mesial dev’tal groove
4. Supplemental grooves

Answer 11

1. square. Buccal > mesioling > distoling
2. round
   * each cusp has well dev triangular ridges sep by deep dev’tal grooves, forming Y-shape
3. travels MB direction, ends in mesial triangular fossa, distal to MMR (same as distal dev’tal groove)
   * mesioling cusp wider MD than distoling cusp
4. often seen, from deep dev’tal grooves

Question 12

Mand 1PM Chronology

• crown
• root
• calc
• erup

Answer 12

-5-6 yrs
-12-13 yrs
-1 1/3-2 yrs
10-12yrs

Question 13

Mand 2PM Chronology

• crown
• root
• calc
• erupt

Answer 13

• 6-7 yr
• 13-14
• 2.25-2.5
• 11-12yr