Morphology Flashcards
Maxillary 1st( central) Permanent Incisor
Initial calcification: 3-4 months
Crown completion: 4-5 years
Root completion: 10 years
Eruption: 7-8 years
Principal identifying features: - largest crown of all incisors, almost as wide as long. Labially has a smooth surface , slightly convex.
- Mesio- incisal angle is sharp, disto-incisal angle is rounded.
- Palatal surface concave with mesial/distal marginal ridges forming a cingulum.
- Viewed mesially/distally crown is wedge shaped and leans palatally.
- One triangular tapering root, one root canal with 2 pulp horns mesial and distal( cornua).
- Externally , if a groove is present it will be more prominent on the distal surface.
VARIATIONS
- malformed macrodent
- exaggerated marginal ridges with an elongated cingulum
- mineralisation defects near incisal edge
- ethnic variations
Mandibular 1st ( central) Permanent Incisor
Initial calcification: 3-4 months
Crown completion: 4-5 years
Eruption: 6-7 years
Root completion: 9 years
PRINCIPAL IDENTIFYING FEATURES
- labially crown appears flat, almost symmetrical
- Disto-incisal angle is marginally rounder than Mesio-incisal angle.
- From the mesial/distal aspect crown appears wedge shaped and leans lingually.
- Faint marginal ridges and small cingulum
- One root flattened mesio-distally
- Mesial and distal surfaces grooved , distal more pronounced
- One root canal , mesial and distal pulp horns.
VARIATIONS
- may get two root canals
- root may be bifurcated at the apex
Maxillary 2nd ( lateral) Permanent Incisor
Initial calcification: 10-12 months
Crown completion: 4-5 years
Eruption: 8-9 years
Root completion: 11 years
PRINCIPAL IDENTIFYING FEATURES
- Labial outline not as rectangular as central, less bulky and more slender.
- cervical region narrowed mesio-distally, long mesial edge with sharp mesio-incisal angle and pronounced rounding of disto-incisal angle.
- Crown wedge shaped when viewed mesially/ distally
- Palatal surface has 2 ridges enclosing a depression or fossa.
- one tapering root, slightly flattened , one root canal, 2 pulp horns
- distal groove more pronounced than mesial
VARIATIONS
- peg shaped lateral, tooth often absent
- dens invaginatus( Palatal pit deep)
- enamel/dentine folds within pulp chamber causes pulpal necrosis in 5%.
- Dens in dentate
Mandibular 2nd( lateral) Permanent incisor
Initial calcification: 3-4 months
Crown completion: 4-5 years
Eruption: 7-8 years
Root completion: 10 years
PRINCIPAL IDENTIFYING FEATURES
- labially crown appears more fan shaped
- mesio incisal angle sharp and disto incisal more rounded.
- mesial side slightly longer than distal
- wedge shaped and leans lingually
- lingual surface similar to central
- viewed from incisal edge crown slightly twisted on root to follow arch
- one root flattened mesio distally , sometimes distally inclined
- distal groove more pronounced
- one root canal, two pulp horns, mesial and distal.
Maxillary Permanent Canine
Initial calcification: 4-5 months
Crown completion: 5.5-6.5 years
Eruption: 11-12 years
Root completion: 13-15 years
PRINCIPAL IDENTIFYING FEATURES
- crown comes a point or cusp at the incisal edge
- labial surface convex and has mesial slope and distal slope but distal is longer.
- distal surface more bulbous than mesial
- Palatal surface has marginal ridges , large cingulum and mesial and distal fossa.
- one long tapering root, one root canal , no pulp horn.
- longest
- greater density of dentine so more yellow.
VARIATIONS
- labiopalatal measurement may be exaggerated
- cingulum may be pointed
- tip of root bent sharply distally
Mandibular permanent canine
Initial calcification: 4-5 months
Crown completion: 6-7 years
Eruption: 9-10 years
Root completion: 12-14 years
PRINCIPAL IDENTIFYING FEATURES
- less bulky than upper canines
- viewed labially , crown tall compared to width , smooth, convex, cusp inclines distally.
- whole tooth tends to have a distal sweep.
- distal surface more bulbous than mesial
- lingually less pronounced cingulum, two lingual fossae, distal larger .
- one root flattened mesio distally with mesial and distal groove , distal more prominent.
- one root canal , no pulp horns.
VARIATIONS
- partial bifurcation of root to a labial and lingual root.
- single longitudinal root with two root canals.
Maxillary First premolar
Initial calcification: 18-21 months
Crown completion: 5-6 years
Eruption: 10-11 years
Root completion: 12-13 years
PRINCIPAL IDENTIFYING FEATURES
- crown has 2 cusps , one buccal and one Palatal
- buccal cusp larger and similar to canine.
- viewed palatally , tip of Palatal cusp tilts mesially.
- occlusal outline appears angular, wider on buccal side.
-2 cusps seperated by deep mesio distal fissure which crosses over mesial marginal ridge to merge into concave mesial surface. Viewed mesially developmental groove can be seen between roots known as canine fossa.
- crown flattened mesio distally , cusps directly above roots .
- two roots one buccal and one Palatal which may be fused. Two root canals , two pulp horns.
VARIATIONS
- buccal root may be divided into mesio and disto buccal , may be a single root. Roots may be short and blunt or long and slender.
Mandibular first premolar
Initial calcification: 1.5-2 years
Crown completion: 5-6 years
Eruption: 10-12 years
Root completion: 12-13 years
PRINCIPAL IDENTIFYING FEATURES
- crown has 2 cusps, large buccal cusp and smaller lingual cusp.
- viewed mesially/ distally buccal cusp leans lingually.
- lingual cusp tends to overhang root.
- occlusal surface rounded outline distally , slightly angled mesially with developmental groove interrupting mesio lingual marginal ridge. Overall more rounded.
- two fossae, mesial and distal ( larger)
- one root( triangular) mesial / distal grooves, root curves distally, one root canal and buccal pulp horn.
VARIATIONS
- lingual cusp may be larger than normal/missing , accessory cusps may be present on slopes of buccal/lingual cusps , rarely root may be bifurcated , crown may have 2 lingual cusps.
Maxillary second pre molar
Initial calcification: 2-2.5 years
Crown completion: 6-7 years
Eruption: 10-12 years
Root completion: 12-14 years
PRINCIPAL IDENTIFYING FEATURES
- 2 cusps, one buccal and one palatal, buccal slightly larger.
- cusps not as high as first pre molar , making crown appear shorter.
- Palatal cusp tilted mesially , cusp sit directly above root.
- crown flattened mesio distally
- oval occlusal outline , fairly symmetrical
- mesio distal fissure does not interrupt mesial marginal ridge.
- root flattened mesio distally , longer root, curve distally, more prominent groove on distal side. May be one or two root canals and two pulp horns.
VARIATIONS
- crown may flare / taper in at cervix , may be an accessory cusp on distal slope of buccal cusp , additional shallow grooves radiating from central fissure , very rarely root may bifurcate ( no more than 10%).
Mandibular second pre molar
Initial calcification: 2.25-2.5 years
Crown completion: 6-7 years
Eruption: 11-12 years
Root completion: 12-13 years
PRINCIPAL IDENTIFYING FEATURES
- crown may have 2/3 cusps , 1 buccal , 1/2 lingual
- if single lingual cusp , displaced mesially. If 2 then the mesio lingual cusp will be larger.
- bucally , crown has 1 cusp , mesial slope shorter than distal.
- mesial marginal ridge higher than distal , buccal cusp leans lingually , lingual overhangs root.
- occlusal outline rounded ( 1 lingual cusp) , slightly angled ( 2 lingual cusps ).
- in 2 cusps central fissure curves around buccal cusp joining mesial and distal fossae , with 3 cusps central pit with 3 grooves. Mesial and distal developmental grooves running to mesial and distal fossae , lingual groove between lingual cusps to lingual surface.
- single root, curves distally , one root canal, and one pulp horn to each cusp.
VARIATIONS
- crown may flare out to wide occlusal surface from a narrow cervix , very rarely bifurcated.
Mandibular first permanent molar
Principal identifying features
- largest Mandibular tooth
- crown has 5 cusps ; 3 on buccal and 2 lingual
- occlusally a Y shaped fissure pattern : formed by lingual and 2 buccal fissures.
- occlusal aspect roughly oblong
- buccal surface convex and divided into lobes topped by cusps. Between the lobes runs a shallow groove extending from the occlusal fissure between mesio buccal and disto buccal cusps , ending in a buccal pit in 60% of cases. This is prone to caries.
- viewed mesially the buccal cusps lean limgually and the lingual cusps tend to overhang the root.
- 2 roots, one mesial and one distal
- mesial root flattened mesio distally and curves distally. Longitudinal groove present. Distal root slightly shorter, more rounded and less distally curved. Two or sometimes 3 root canals and a pulp horn to each cusp.
Variations :
- 4 cusps instead of 5 , giving more circular outline like to 2nd molar
- mesial root may occasionally be bifurcated giving 3 root apices
- rarely an accessory root grows out of base of distal root on lingual side.
Mandibular second permanent molar
Principal identifying features
- 4 cusps: 2 buccal and 2 lingual , lingual cusps higher than buccal .
- from the mesial or distal aspect the buccal cusps lean lingually
- rectangular occlusal outline with cusp at each corner.
- central cruciform fissure pattern seperates cusps
- lingual cusps seperated by lingual groove - extends from occlusal half of the lingual surface to the centre of occlusal surface where joins the buccal groove.
- buccal groove seperates buccal cusps terminating in buccal pit
- not as wide mesio distally as first molar
- bulbous buccal surface
- 2 roots mesial and distal but less wide and closer together than first molar.
- 2/3 root canals with one pulp horn per cusp.
Variations
- crown form may be similar to Mandibular first molar - 3 buccal cusps and 2 lingual.
- roots may be partially fused
- distal curvature of roots
- very rarely there’s a partial divison of the mesial root.
Maxillary first permanent molar
Features:
- largest maxillary tooth
- crown has 4 cusps: mesio palatal, mesio buccal, disto palatal and disto buccal. Mesio palatal is the largest, mesio buccal is the highest.
- occlusally crown is equilateral rhomboid in shape.
- in approx 50-70% people a 5th cusp of carabelli is present on the mesio palatal cusp.
- oblique ridge ( triangular ridge of disto buccal cusp and distal ridge of mesio palatal cusp) joins mesio palatal and disto buccal cusps.
- 4 cusps seperated by a fissure pattern roughly in shape of a H. The horizontal bar of the H formed by a fissure which crosses oblique ridge.
- 3 occlusal fossae. Mesial, central, distal.
- 3 roots: 2 buccal, one palatal. Palatal is longest.
- 3 root canals and 4 pulp horns.
Variations:
- partial roots of buccal roots
- enamel pearls present cervically on mesial or distal surfaces .
- underdeveloped disto palatal cusp.
- shallow concavity sometimes present on palatal surface of palatal root next to CEJ which might be prone to caries.
Maxillary permanent second molar
Features
- crown has 4 cusps , 2 buccal and 2 palatal.
- disto palatal cusp much smaller than first molar .
- bucco palatal diameter of crown similar to maxillary first molar , mesio distal diameter is much less in proportion.
- no cusp of carabelli
- 3 roots, two buccal and one palatal , slope together and slope distally.
- fusion of roots common
- oblique ridge joins mesio palatal and disto buccal cusp
- 3 root canals and three/ four pulp horns depending on no.of cusps.
Variations:
- crown may have 3 cusps, disto palatal missing
- root fusion
- enamel pearls may be present on mesial and distal surfaces of root. Enamel pearls are enamel found where enamel shouldn’t be.
