Tooth morphology Flashcards
Primary vs Permanent
a) size
b) shape
c) colour
d) hardness
e) roots
f) pulp cavities
g) dentine thickness
a) smaller
b) more bulbous
c) whiter = more proteins, less minerals
d) enamel is thinner so softer
e) thinner, shorter and more diverged
f) larger
g) thinner
Why are primary teeth less susceptible to inter proximal caries?
Less crowded
Difference in pulp horn position between primary and permanent teeth?
Primary = closer to EDJ
What do all primary teeth possess on labial/palatal surface?
Low rounded labial cingulum
Crown shape of upper primary 1?
Transverses equal to vertical height
Mesial angle RA, distal angle rounded
Root of upper primary 1?
Conical root compressed in labio-palatal direction
Primary vs permanent upper lateral
Primary = more acute medial angle and more rounded distal angle
Root is compressed in labio-palatal direction
Primary vs permanent upper canine
Primary = symmetrical, if it isn’t the cusp is displaced distally unlike permanent
Much fatter
Primary molars
Crowns of first primary molar intermediate in shape between permanent premolars and molars
Primary 2nd molars resemble permanent 1st molars
Upper primary first molar
a) crown shape
b) buccal and palatal cusps
c) roots
a) irregular quadrilateral (4 cusps)
Buccal side wider and palatal side shorter
b) convergence of buccal and palatal cusps towards midline
c) 3 roots (2 buccal, 1 palatal)
Which incisors have mesiodistally compressed roots?
All lower incisors
What is the angle of the mesio-incisal edge of upper central incisors?
90
How can you distinguish between lower central and lower lateral incsiors?
Lateral = asymmetric fan shaped crown with distal angle more acute than medial
Incisal edge distally is curved lingually
Central = symmetrical rectangular crown = both angles 90
Which ridge is shorter on all canines?
Mesial
State 2 differences between upper and lower canines
Upper canine - larger and longer root
Lower = difference in length of ridges is less pronounced.
Has a labial cingulum and is inclined labially
Which ridge is steeper on all canines?
Distal
Which pre-molars have disto-lingual accessory cusps?
Lower 5 almost always and lower 4 often
Roots of upper 4?
One buccal one palatal root, sported by the canine fossa
Are upper or lower pre-molar crowns more circular?
Lower
Which tooth has canine groove and fossa?
Upper 4
Which tooth has canine groove?
Upper 4 and Lower 4
Difference in buccal cusps of lower 4 and 5
Lower 4 = very prominent buccal cusp and small lingual cusp
Lower 5 = better developed lingual cusp and smaller buccal cusp
On which tooth is the medial ridge straighter and longer than the distal?
Upper 4
Upper 4 vs Upper 5
Upper 4 usually has 2 roots (buccal and palatal) where as upper 5 has only one although it is deeply grooved
Buccal cusp of upper 5 is smaller than upper 4
Upper 4 has canine fossa and groove
Describe the position of the palatal cusp compared to buccal cusp on all upper pre-molars?
More mesially
Which molars have 3 roots?
Upper 6 and 7 = 2 buccal 1 palatal
7 may be partly fused
Crown shape of upper 1st molar?
Rhomboid, with 4 cusps separated by H shaped fissure
Largest cusp of upper 6
Mesio-palatal
Accessory cusp of upper 6 and where it is found?
Tubercle of carabelli, on the mesio-palatal cusp
3 types of upper 7
- similar to upper 6 but smaller and the disco-palatal cusp is reduced in size
- heart shaped = no disto-palatal cusp = 3 cusps only
- fusion of mesio-palatal and ditto-buccal cusps causes oval shaped crown
Most common type of upper 8?
Resembles type 2 of upper 7 = heart shaped but may be reduced to rounded triangular shape
How does reduction of upper and lower 8s differ?
Upper retains triangular shape and becomes rounded triangular
Lower retains rectangular shape or becomes circular
Crown of lower 6
5 cusps = 2 lingual, 3 buccal
Roots of lower 6
2 roots, 1 medial, 1 distal, deeply grooved
Mandibular characteristic
Buccal cusp tilted lingually
Difference in crown shape upper vs lower pre-molars?
Uppers are wider bunco-palatally whilst lowers are wider mesio-distally
Crown of lower 7
square with 4 cusps separated by cross fissure
Roots of lower 7
2 roots, may be fused 1 medial, 1 distal
Crown of lower 8
Regular shape, normally 4 cusps, the fissure is often heavily branched so can have more
Roots of lower 8
2 roots (medial and distal) one rot frequently sub-divided
Which molars have 5 cusps?
Lower 6
Upper 6 with tubercle of carabelli
Which molars have cusp of carabelli?
Upper 6
In which direction are root apices pointed?
Distally
Describe the number of cusps and crown shape of lower 7?
Regular square/rectangle = 4 cusps
Which side, buccal or palatal, of upper molars has 2 roots?
Buccal
2 main differences between crowns of permanent and primary teeth?
Permanent are larger and less bulbous
Which primary molar is larger, D or E?
E
Describe the medial ridge of lower C compared to distal ridge?
Shorter and steeper
Difference between mesial and distal marginal ridge of all Ds?
Distal is flat against E, medial is sloped distally
Why are primary roots diverged?
To allow room for the developing tooth germ beneath
