Ch 9 Permanent Max PreMolars Flashcards
1
Q
Why are cusps and grooves arranged they way they are?
A
-to contact the occlusal surfaces of the mandibular cusps and grooves so that they fit together to interdigitate. Allowing chewing, called comminution.
2
Q
General Info of Max Pre-Molars
A
- Total 4 teeth
- succeed deciduous molars
- 4 lobes: well-formed ling cusp, middle buccal is long and sharp
- there is less space toward the post region of mouth hence D surfaces of teeth are gen. smaller than M
- crown tips distally, so more of occlusal aspect can be seen distally
3
Q
General Info of Max 1st Pre-Molar
A
- 2 cusps: buccal and lingual
- buccal 1mm > lingual
- roots 3mm or 4mm < canine
- mesial slope of cusp (longer) > distal slope of cusp
- 2 roots, 2 pulp canals. Buccal root resembles canine.
- # canals: 1-19.5%
- 2-79.5%
- 3-1%
4
Q
Buccal aspect 1st PM
A
- trapezoidal crown
- cervical line-little curvature, crest is near center of root buccally
- mesial: slightly concave
- distal: straighter
- buccal cusp is long and pointed
5
Q
Lingual aspect 1st PM
A
- crown: narrower mesiodistally, tapers toward lingual aspect
- cusp: smooth & spheroidal, pointed tip. Shorter than Bu cusp
- cusp tip: is pointed w/ the M & D slopes meeting at 90deg
- small portion of Bu cusp visible
6
Q
Mesial aspect 1st PM
A
- Bu and Li cusps visible
- MMR and Mesial Marginal Dev’tal groove present
- Marked Mesial Dev’tal Depression seen at middle of mesial surface extending beyond cervical line
- cusp tips: w/in confines of root trunk
- crest at center of middle 1/3 or some abrupt curve at cervical 1/3
- ling cusp 1mm < buccal cusp
- mesial dev’tal depression: cervical to mesial CA, continues apically beyond cervical line, joining a deep dev’tal depression bet. roots, ends at bifurcation.
- well-defined dev’tal groove in enamel of MMR
- buccal root, may take buccal or ling inclination, apical to middle 1/3.
7
Q
Distal aspect of 1st PM
A
- cervical: curvature less than mesial (less of the cervical line)
- deep dev’tal groove not evident (convex at all points)
- root trunk: flattened (above cervical line)
- root bifurcation is abrupt near apical third
8
Q
Occlusal aspect of 1st PM
A
- 6-sided hexagonal:
1. mesiobuccal
2. mesial
3. mesioling
4. distoling
5. distal
6. distobuccal - mesial side < distal side, mesioling < distoling
- buccal sides nearly equal
- occlusal surface is circumscribed by the cusp ridges and marginal ridges
- following are present w/in the cusp ridges and marginal ridges:
1. central dev’tal groove
2. MB &DB DG
3. MMRDG
4. M&D triangular fossa
5. Bu&Li triangular ridge
*MBCR & MMR = right angle
DBCR & DMR = acute
*DBCR is buccal to MBCR
9
Q
Chronology of 1st PM:
- crown
- root
- calc
- erupt
A
- 5-6 yrs
- 12-13 yrs
- 1.5-1.75 yrs
- 10-11 yrs
10
Q
Chronology of 2nd PM:
- crown
- root
- calc
- erupt
A
- 6-7 yrs
- 12-14 yrs
- 2-2.25 yr
- 10-12 yrs
11
Q
Gen Info for 2nd Pm
A
- supplements max 1st PM in function
- less angular
- has 1 root
- crown is smaller cervico-occlusally and mesiodistally
12
Q
Buccal aspect of 2nd PM
A
- cusp is shorter than 1st PM and it appears less pointed, more rounded
- mesial slope < distal slope
- crown: trapezoidal
- middle facial lobe most developed
- dev’tal depression less evident
13
Q
Lingual aspect of 2nd PM
A
- lingual cusp nearly as large as the buccal cusp
- rounded on all aspect
- tip of ling cusp leans towards M of tooth
- lling cusp in line w/ bucc cusp, nearly same height
14
Q
Mesial 2nd PM
A
- cusps are shorter, rounded
- buccal/ling cusps are more nearly the same length
- greater dist bet cusp tips widens occlusal surface bucc lingually
- MMR is in a horizontal position and is slightly concave, slightly occlusal than DMR
- MCA is at the junction of Bu and Midd 3rd
- CL line curvature shallow, about 1mm greater than D
- No dev’tal depression, except shallow dev’tal groove on single tapered root
- crown convex
- no deep dev’tal groove crossing MMR
15
Q
Distal 2nd PM
A
- rounded
- DMR more cervical than MMR
- DCA is ling to MCA
- Dev’tal dep evident and deeper than mesial dep
