Tooth morphology Flashcards
What teeth are present in deciduous teeth?
8 incisors, 4 canines, 8 molars
no premolars
What surface is labial
face towards lips
from canine to canine
What surface is lingual/ palatal
face towards tongue (mandibular)
face towards palate (maxillary)
What surface is buccal
face towards cheek
from premolar to last molar
Vestibular surfaces
buccal/ labial
american eng terms
Mesial
surface closest to midline
Distal
surface farthest from midline
Cervix/ cervical line
amelo-cemental junction
Cingulum
incisors/ canine
bulge of enamel found on cervical third of the lingual surface of all anterior teeth
Marginal ridges
elevation of enamel
forms mesial/ distal margin of lingual surface of an anterial tooth
form occlusal surface of posterior tooth
Purpose of dental notation
allow communication between specialists/ when on referral
Long hand dental notation
upper/lower + left/ right + tooth number + tooth type
e.g. upper left first molar
Zsigmondy-Palmer dental notation
quadrant + tooth
e.g. upper left quadrant symbol with 6 inside
used in notes/ hard copies
difficult to input on computer (electronic format unfriendly)
Federation Dentaise International (FDI)
number of quadrant + number of the tooth
e.g. 26
quick
electronic format friendly
used in UK
Universal system
upper right to upper left: 1-16
lower left to lower right: 17-32
e.g. 14
unique to North America
Alphanumeric dental notation
quadrant + number of tooth
e.g. UL6
Reason for studying tooth morphology
- for tooth restoration (occlusion must be correct for teeth to function)
- knowledge on tooth morphology is needed for root canal treatments
- help to know the shape of the tooth -> help to know th correct movement/ rotation for tooth extraction
Upper central incisors
-* largest crown out of the 4 incisors
-* crown as wide as long (root:crown roughly 1:1)
- crown has smooth surface + usually slightly convex
- sharp mesio-incisal angle
- more rounded disto-incisal angle
- concave lingual surface
- wedge-shaped crown (when view mesially/ distally) + cone-shaped root
- mesial + distal marginal ridges meet at neck to form convex cingulum (scooplike)
- have cuplets/ mammelons (wear off later on in mouth)
-* greater mesial undulation than distal (cervical line greater curvature on mesial side)
Upper lateral incisors
-* narrower
-* less bulky and more slender (relatively smaller)
- not as retangular
-* slightly rounded mesio-incisal edge
- more rounded disto-incisal edge
- long mesial surface (cervical region narrowed mesio-distally)
- 2 pronounced marginal ridges meet -> *enclose a fossa/ depression (deposit can accumulate -> more susceptible to caries)
- wedge-shaped crown when view mesially/distally
- greater mesial undulation
Lower central incisors
-* flat + almost symmetrical crown
- view from above: line of incisal edge perpendicular to line bisecting tooth
- wedge-shaped crown (mesially/distally) leans more lingually (compare to upper due to occlusion)
- sharp angles
- greater mesial undulation
-* faint marginal ridges + small cingulum
-* roots appear to be flat (laterally)
Lower lateral incisors
-* more fan-shaped crown
-* sharp mesio-incisal edge
- rounded disto-incisal edge
-* relatively larger (compare to lower central)
- wedge-shaped crown (mesially/ distally)
- greater mesial undulation
- mesial side longer than distal side
-* (view from above) incisal edge of crown slightly twisted on root -> follow the dental arch
Upper canine
-* a pointed cusp (instead of incisal edge)
- assymmetrical
- concave (palatal side) -> often 2 fossae
- greater cervical margin curvature on mesial surface
-* mesial contact point located more incisally
-* distal contact point locate at centre of the middle third of the crown
- shorter + less steeply inclined mesial border (from tip of cusp to mesial contact point)
-* longest + strongest human dentition -> long root)
-* (view from side) irregularly oval
- root usually slightly grooved both mesially + distally (have a line runing down the root)
-* diamond shape crown set in straight line with root
-* AMJ at same level on labial + lingual side of crown
Lower Canine
-* more slender (narrower)
- less pointed cusp
- more symmetrical
-* less pronounced cingulum/ marginal ridge (compare to upper canine)
-* flatter lingual surface
- shorter + less steeply inclined mesial border
- ridges less prominent
- labial surface lingually inclined -> bring cusp to lingual position
- crown set at an angle to the root -> more convex labial probile from cusp to apex -> tilt towards distal
- enamel extend further apically on labial side than lingual
Upper first premolar
-* roughly oval
- 2 cusps
- palatal surface slightly lower + much narrower than buccal
- very convex distal surface
- convex occlusal half of mesial surface + concave cervical half
-* mesial surface of root deeply grooved -> canine fossa
-* well-defined developmental groove in enamel of mesial marginal ridge
-* align with developmental depression on mesial surface (not usualy connected)
-* groove continuous with central groove of occlusal surface
-* wider + higher buccal cusp (than lingual)
- higher mesial marginal ridge
-* sharp fissure running mesio-distally (don’t reach distal marginal ridge but often extends to mesial) separates the 2 cusps
-* mesial displacement of lingual cusp (lingual cusp not centred - closer to mesial side)
-* more than 50% - 2 roots (one buccal + one lingual)
- bifurcation variable distance from cervical margin
-* apical part of root usually has marked distal curvature
Upper second premolar
-* smaller than upper first
-* occlusal surface more symmetrical
- 2 cusps with similar width + height
-* smaller buccal cusp compare to upper first
- convex mesial surface crown
-* no developmental depression on mesial surface of the crown
- deeper distal root depression (opposite of upper first)
-* (only very slight) medial displacement of the lingual cusp
-* 2 cusps separated by fissure running meio-distally but don’t reach marginal ridges
- only 15% have 2 roots, usually deeply grooved single root
- distal marginal ridge more cervical (curve closer to cervical line) than mesial
Lower first premolar
- buccal surface inclined strongly lingually -> tip almost above centre of the tooth
- slight narrower + much lower lingual surface
-* almost round occlusal surface
-* greater difference in buccal + lingual cusp height - small groove run from mesial pit to mesial lingual surface
- mesial marginal ridge more cervical than distal
- small semi-circular arc mesial contact point
- more broad distal contact point
Lower second premolar
- much larger crown than first
- lingual cusp much larger than first + displace mesially
-* might be 2 lingual cusp (mesial lingual cusp larger) - generally larger distal fossa than mesial
distal marginal ridge more cervical than mesial
-* (compare to lower first) smaller difference between the height of lingual and buccal cusps
Clinical relevance of upper 1st premolar
- ignoring mesial canine fossa during restoration -> (might) improper contact relationship with distal proximal surface of canine -> overhang
Define:
- unilateral
- bilateral
- ipsilateral
- contralateral
- unilateral: affecting only one side
- bilateral: affecting both side
- ipsilateral: belonging to / occuring on the same side of the body
- contralateral: occurs on the opposite side of the body
Upper first molar
- diamond-shaped (longer diagonal extending from mesio-buccal to disto-palatal cusp - emphasised by opaque ridge)
- 3 roots (2 buccal + 1 palatal)
- 4 cusps (2 buccal + 2 palatal)
- 2 fissure (one distal + one mesial) connected by a shallow fissure -> H-shape
- distal fissure run parallel to oblique ridge＋continues on palatal side
- largest cusp: mesio-palatal cusp
- smallest cusp: disto-lingual cusp
- two buccal cusps similar circumference + height
-* tubercle of carabelli on palatal surface of mesio-palatal cusp - found on 60% of upper first
- to hold it: thumb on palatal + index on buccal
Upper second molar
- similar features as upper first but
-* more triangular shaped
-* disto-palatal cusp greatly reduced or even missing
-* roots much less divergent - palatal root often partially fused with either of the buccal root
Upper third molar
-* smallest out of the three
- often only 3 cusp (no disto-lingual)
- roots usually fused into one bulky root with deep grooves where root would be divided
- may show a completely irregular form
Lower first molar
-* 5 cusps (3 buccal + 2 lingual)
-* smallest cusp: distal cusp
- groove starts on buccal surface -> deepen into transverse fissure across occlusal surface -> end as groove on lingual surface
- another fissure runs mesio-distally: starts near mesial marginal ridge -> cross the central fossa/ pit -> divide into 2 branches passing each side of the distal cusp
- larger buccal surface (compared to lingual) + lingually inclined
- buccal surface usually have a pit -> increased risk of caries
-* 2 roots (1 mesial + 1 distal)
- both strongly compressde mesio-distally - show distal curvature (more pronounced on mesial root)
- mesial root usually curved + grooved + broader than distal root -> *distal root not visible from mesial aspect
Lower second molar
- more symmetrical
- smaller
- usually only 4 cusps of similar size
-occlusal surface almost square
-* + shaped fissure pattern - largest cusp: mesio-buccal cusp
- highest cusps: lingual cusps
- tootes less divergent (might be fused)
- lingual - shorter crown
Lower third molar
- variable shape + size crown
- 50% 5 cusps, 40% 4 cusps, 10% 3 or >5 cusps
- roots often fused
Clinical relevance of upper 1st molar
- shape + inclination of palatal cusp need to be carefully considered in order to achieve optimal occlusion of complete denture
- mesio-palatal cusp should be on occlusal plane
- buccal cusps should be raised from plane
- if tooth morphology not considered while designing restoration -> excessive adjustment of restoration
endodontics
- access cavity should be placed mesially to transverse oplique ridge (TOR)
- inappropriate access cavity -> failure to locate second mesio-buccal canal
- palatal canal often curve towards buccal but appear straight on radiographs (need to consider)
Clinical relevance of lower 2nd molar
endodontics
- The mesiobuccal canal orifice on the chamber floor is located slightly mesial but close to the mesiobuccal cusp tip.
* The mesiolingual canal orifice is just lingual to the mesial developmental groove of the mesial marginal ridge, it is not under the
mesiolingual cusp tip but is in a more central location.
* If the distal root has one canal, the distal canal orifice is large and located just distal to the centre of the crown. When two canals are
present, the distolingual orifice is small and is located centrally just lingual to the central fossa.
* Careful inspection of the chamber floor toward the buccal will successfully locate the distobuccal orifice.
* Almost 40% of lower 2nd molars will have canals with greater curvature in the unseen bucco-lingual plane than the mesiodistal plane
