1. Dental Anatomy and Chronology Dr. Razan Ahmad Al Majali
2. Tooth Morphology
3. General informations Humans have two generations of teeth :
deciduous and permanent By the age of 3 years all deciduous teeth
have erupted . By 6 years, the first permanent teeth appear and
hence the deciduous teeth are exfoliated one by one replaced by
their permanent successors. A complete permanent dentition is
present at around 18 years . 20 teeth 10 in each jaw. (primary
dentition ) 32 teeth 16 in each jaw.
4. Three basic tooth form : incsiform , caniniform , molariform
. Incisors : cutting teeth , thin , blade- like crowns. Canines :
piercing or tearing teeth , single pointed cone-shaped crown .
Molars : grinding teeth possessing a number of cusps on an
otherwise flattened biting surface . Premolars: bicuspid teeth
,replace the deciduous molars.
5. Some terms for the description of tooth form : Crown :
clinical crown : that portion of a tooth visible in the oral cavity
Anatomical crown :that portion of a tooth covered with enamel .
Root : clinical root : portion of tooth which lies within the
alveolus . Anatomical root : that portion covered by cementum .
Cervical margin : the junction of the anatomical crown and
anatomical root . Occlusal surface : biting surface . Cusps :
pronounced elevation of occlusal surface . Incisal margin :cutting
edge Tubercle : small elevation on the crown . Cingulum : bulbous
convexity near cervical region of the tooth .
6. Ridge : linear elevation on the surface of a tooth. Marginal
ridge : ridge at the mesial or distal edge . Fissure : long cleft
between cusps or ridges . Fossa : rounded depression in a surface
of a tooth . Buccal : toward cheeks. Labial : toward lips . Palatal
: toward palate . Lingual : toward the tongue . Mesial : toward the
median . Distal : away from the median .
7. Dental notation: For deciduous teeth DI 2/2 DC 1/1 DM 2/2 =
10 For permanent teeth I 2/2 C 1/1 PM 2/2 M 3/3 =16 Zsigmondy
system : 8 7 6 5 4 3 2 1 1 2 3 4 5 6 7 8 8 7 6 5 4 3 2 1 1 2 3 4 5
6 7 8 E D C B A A B C D E E D C B A A B C D E
8. Federation Dentaire Internationale (FDI) : 1= max. rt.
Quadrant 2= max. left quadrant for PERMANENT 3 = mand. Lft quadrant
4 = mand . rt quadrant 5= max. rt. Quadrant 6= max. left quadrant 7
= mand. Lft quadrant for DECIDUOUS 8 = mand . rt quadrant
9. Differences between deciduous teeth and permanent : 1 . The
deciduous teeth are smaller, although the mesiodistal dimension of
the permanent premolars are generally less than those for deciduous
molar . 2. Deciduous teeth have a greater constancy of shape . 3.
The crown of deciduous teeth appear bulbous , often having
pronounced labial or buccal cingula . 4. the cervical margins of
deciduous teeth are more sharply demarcated and pronounced , enamel
bulging rather than gently tapering . 5. the cusps of newly erupted
deciduous teeth are more pointed .
10. 6. the crowns of deciduous teeth have thinner enamel (
0.5-1.0 mm ) than the crowns of permanent teeth (2.5 mm ) 7. the
enamel of deciduous teeth are more opaque , gives the crown a
whiter appearance 8. the enamel is softer and more easily worn in
deciduous teeth . 9. enamel is more permeable in dec. teeth . 10.
the aprismatic layer of surface enamel is wider in dec. teeth
.
11. 11. the enamel and dentine of ALL dec . teeth exhibit
neonatal lines . 12. the roots of dec. teeth are shorter and less
robust than those of permanent teeth . 13. the roots of dec.
incisors and canines are longer in proportion to the crown than
those of permanent ones. 14. the roots of the dec. molars are
widely divergent extending beyond the dimensions of the crown. 15.
the pulp chambers of dec. are proportionally larger in relation to
the crown than those of permanent teeth. the pulp horns in dec. are
more prominent. 16. the root canals of dec. are extremely fine . 17
. the dental arch for dec. dentition are smaller .
12. A, The enamel cap of primary molars is thinner and has a
more consistent depth. B, A comparatively greater thickness of
dentin is over the pulpal wall at the occlusal fossa of primary
molars. C, The pulpal horns are higher in primary molars,
especially the mesial horns, and pulp chambers are proportionately
larger. D, The cervical ridges are more pronounced, especially on
the buccal aspect of the first primary molars. E, The enamel rods
at the cervix slope occlusally instead of gingivally as in the
permanent teeth. F, The primary molars have a markedly constricted
neck compared with the permanent molars. G, The roots of the
primary teeth are longer and more slender in comparison with crown
size than those of the permanent teeth. H, The roots of the primary
molars flare out nearer the cervix than do those of the permanent
teeth.
13. THE INCISORS : THE MAXILLARY FIRST CENTRAL PERMANENT
INCISOR : Incisal view : - The crown and incisal margin are
centrally positioned over the root of the tooth. - The incisal
margin presents as narrow flattened ridge rather than as a fine
sharp edge. - The crown outline is bilaterally symmetrical, being
triangular. Mesial appears slightly larger. - may have two grooves,
the labial lobe grooves; correspond to three developmental lobes
(mammelones) which are lost by attrition.
14. Labial view : Smooth , convex . Convexity marked cervically
. flat at the middle and incisal regions. Crown length almost as
great a root length . Two faint grooves which are extensions of the
labial lobe grooves. Mesial surface is straight and at right angle
to incisal margin . Distal outline is convex and the distoincisal
angle is more rounded.
15. Palatal view : More irregular ,shovel shaped Bordered by
mesial and distal marginal ridges . Middle and incisal third being
concave. Prominent cingulum lies near the cervical margin maybe
single ,divided
16. Mesial and distal : Wedge shaped or triangular . The root :
Single root tapers toward the apex . The root is conical in cross
section , narrower palataly .
17. THE MAXILLARY PERMANENT LATERAL INCISOR : The smallest
mesiodistal dimensions of any teeth in permanent dentition. One of
the most variable teeth in dentition . It is morphologically a
diminutive form of maxillary incisor with slight modifications .
The crown is much narrower and shorter , the crown:root ratio is
decreased .
18. Incisal aspect : More rounded than central. Labial view :
The mesioincisal and distoincisal angles and mesial and distal
crown margins are more rounded .
19. Palatal view : Similar to central . marginal ridges and
cingulum are more pronounced , and palatal concavity appears
deeper. In front of the cingulum is a pit ( foramen caecum)that may
extend into the root. The root : Slightly compressed and grooved on
the mesial and distal surfaces . CAN BE DISTINGUISHED : by their
size , the marked lingual inclination of the crowns over the roots
, mesiodistal compression of their roots , poor development of the
marginal ridges and cingula .
20. THE MANDIBULAR PERMANENT CENTRAL INCISOR : Incisal view :
Bilaterally symmetrical triangular shape . Labial view : The crown
is almost twice as long as it is wide . Straight incisal angle .
Mesio and distoincisal angles are sharp and approximately at right
angle . Mesial and distal surfaces are similar , being flattened in
the middle and cervical thirds and convex in the incisal third
.
21. Lingual view : Smooth and slightly concave Lingual cingulum
and mesial and distal marginal ridges are less distinct . Mesial
and distal view : Wedge shape . The cervical margin on the distal
side is less curved than that of the mesial . The root : Narrow ,
conical . Frequently grooved on the mesial and distal surfaces ,
distal groove more marked and deeper .
22. THE MANDIBULAR LATERAL PERMANENT INCISOR : Closely
resembles the mand. Central incisor . Slightly wider mesiodistally
and asymmetric in shape. Distal surface diverges , giving it a fan-
shaped apperance . Distoincisal angle more acute and rounded .
DISTINGUISHING characteristic : the angulation of the incisal
margin relative to the labiolingual axis of the root is twisted
distally in a lingual direction , where as in the central it forms
a right angle .
23. THE CANINES: The only teeth in the dentition with a single
cusp . Triangle.. mesially and distally Trapezoidal .. buccally and
palataly ..
24. THE MAXILLARY PERMANENT CANINE : Well developed cingulum
and the longest root of any tooth. Incisal view : The distal
portion is much wider than the mesial portion. The pointed shape of
the canine is thought to be related to an increase in the size of a
central mammelon Prominent longitudinal ridges pass from the cusp
tip down both the labial and palatal surfaces. Variations : like an
accessory
25. Labial view : Marked by longitudinal ridge extends from the
cusp to the cervical margin . The incisal part occupies at least
1/3 of the crown height . The mesial arm is shorter than the distal
arm. The distoincisal angle is more rounded. The mesial profile is
slightly convex with a straight line with the root . the distal is
markdly convex an obtuse angle with the root .
26. Palatal view : Well defined cingulum and distinct marginal
ridges . Longitudinal ridge meets the cingulum and is separated
from the marginal ridges by a distinct groove or fossa Mesially and
distally : Great width of the cervical third of both the crown and
the root . The curvature of cervical margin distally is less marked
than mesially.
27. The root : The largest and stoutest in the dentition.
Triangular in cross section . Mesial and distal surfaces of the
root are often grooved longitudinally.
28. THE MANDIBULAR CANINE : Similar to the maxillary , but
smaller , more slender , more symmetrical . The cusp is less
developed . with attrition it may resemble max. lateral incisor.
Incisal view : No distinct longitudinal ridges from the tip of the
cusp onto the labial and lingual surfaces .
29. Labial view : The cusp is less pointed , the incisal margin
occupies only 1/5 of the crown height . Crown is narrower
mesiodistally , it appears longer , narrower and more slender .
Mesial and distal profiles are parallel. Lingual view : Surface of
cingulum ,marginal ridges and fossa are indistinct . Lingual
surface is flatter than
30. Mesially and distally : Wedge-shaped appearance . Cervical
margin follows a course similar to the incisors , more marked
distally . The root : Normally single .occasionally it may
bifurcate . Oval cross section . The root is grooved
31. THE PREMOLARS : Bicuspids ( two cusps buccal and lingual
separated by mesiodistal occlusal fissure). To distinguish upper
and lower premolar when viewed mesially or distally upper premolars
are trapezoidal in shape while the lowers are rhomboidal in shape
and inclined lingually .
32. THE MAXILLARY FIRST PREMOLAR : Occlusal view : Ovoid .
border buccaly than palatally Mesio and distobuccal corners are
less rounded than mesio and distopalatal . Distinct mesial and
distal marginal ridges. Central occlusal fissure that crosses
mesial marginal ridge onto mesial
34. Buccal view : Resemble the canine . Longitudinal ridge .
Prominent mesio and disto- occlusal angles . Mesial slope is longer
than distal slope . Palatal view : Palatal cusp is smaller and
lower than buccal . The tip lies more mesially .
35. Mesial view : Canine groove across the mesial marginal
ridge . Cervical third marked by a distinct concavity the canine
fossa Distal veiw : Lacks the canine groove and fossa . The roots :
Usually two roots , sometimes single root which is deeply grooved
.
36. THE MAXILLARY SECOND PREMOLAR : Similar to first premolar
except : Occlusally : More rounded mesio distobuccal corners.
Mesial and distal profiles parallel to each other . Smaller
mesiodistally. Central fissure doesnt cross the marginal
ridge.
37. Buccally : Less prominent disto and mesio-occlusal angles.
narrow shouldered appearance Smaller cusps , equal in size cusps.
Mesially : No canine fossa and groove . The root : Single root
.
38. THE MANDIBULAR FIRST PREMOLAR : Smallest premolar .
Dominant buccal cusp and very small lingual cusp. Occlusal view :
More than 2/3 of buccal aspect is visible. Diamond shaped. Broad
buccal cusp , its apex at midpoint of the crown. Buccal and lingual
cusps are connected by a transverse ridge that divides the occlusal
fissure to mesial and distal fossa ( mesial fossa is smaller).
Canine groove crosses the mesial marginal ridge .
39. Buccally : nearly Symmetrical . lingual view : the entire
buccal profile and occlusal surface are visible . 2nd premolar
differs from other premolars that the occlusal plane doesnt lie
perpendicular to the long axis of the tooth . The root : Single ,
conical ,and oval cross section . Root is grooved longitudinally
mesial and distal .
40. THE MANDIBULAR 2nd PREMOLAR : The crown is generally
larger. Lingual cusp is better developed. Occlusal aspect : Round
or square . Well defined mesiodistal occlusal fissure . Distal
fossa is larger then mesial fossa. Accessory cusplets are common on
both buccal and lingual . Lingual cusp is usually subdivided to
mesio and distolingual cusps. Mesiolingual is wider and higher
.
41. Buccal aspect : Symmetrical . Appears shorter and more
rounded than 1st mand premolar . Lingually : Little if any of the
occlusal surface and buccal profile is visible . Mesial and distal
: Mesial marginal ridge is higher than the distal . Occlusal
surface appears horizantal to the long axis . The root : Single ,
conical , nearly round in cross section.
42. THE MOLARS : largest occlusal surfaces of all teeth . have
3-5 MAJOR cusps. Have more than one buccal cusp . In general .. 3
roots upper , 2 roots lower . Buccally and lingually are
trapezoidal. Mesially and distally .. upper trapezoidal , lower
rhomboidal.
43. MAXILLARY 1st PERMANENT MOLAR : Occlusally : Rhombic in
outline. Four major cusps separated by an irregular H- shaped
occlusal fissure. Occlusal table is divided to two components
(trigon and talon )by the oblique ridge. Oblique ridge passes from
the mesiopalatal cusp to the distobuccal cusp. Mesiopalatal .. the
largest cusp Trigon ; triangular in shape ,apex directed palataly .
bears the mesiobuccal ,mesiopalatal, and distobuccal cusps . Apex:
mesiopalatal base : buccal cusps Mesial marginal ridge and the
oblique ridge form its sides. Central fossa , central fissure
terminate in mesial pit , buccal fissure,
44. Talon : bears distopalatal cusp .the smallest cusp
Distopalatal fissure separates the palatal cusps ,ends in a distal
pit. Accessory cusplet the tubercle of Carabelli : seen on
mesiopalatal cusp ,variable sizes,found on 60% of max 1st molars.
CHARACTERISTIC of max. molar : the tips of palatal cusps are nearer
the mid- mesiodistal diameter of the crown than buccal cusps.
46. Buccal view : Mesiobuccal cusp is wider than distobuccal .
but equal in heights . Buccal groove extends to end about half way
. Distal profile.. convex all regions . mesial profile concave in
cervical 1/3 and convex n the middle and occlusal thirds . Palatal
view : Mesiopalatal is larger , blunt . Palatal groove extends
approximately halfway up the palatel surface.
47. Mesial and distal : Maximum bucco-palatal dimension is at
the cervical margin. Mesial marginal ridge is more prominent and
have a no. of destinct tubercles which are rare distally. The
roots: 3 roots : 2 buccaly , 1 palataly .from a common root stalk .
At the root stalk palatal root is more related to distobuccal root
. Palatal is the longest and strongest. Buccal roots are more
slender and mesiodistally flattened .
48. THE 2nd MAXLLARY MOLAR : Resembles 1st molar but shows some
reduction in size and cusps relationship. Common variations in
morphology . Occlusal view : More pronounced rhomboid form. Smaller
oblique ridge , the talon is reduced. More variable occlusal
fissure pattern.
49. Buccal view : Two features that differentiate the 2nd molar
: smaller size and distobuccal cusp . Palatal view : Reduction in
size of the distopalatal cusp is more visible. Tubercle of
Caraballi is not always found.
50. Mesial and distal : The tubercles on marginal ridges are
less pronounced. The roots : 3 roots , shorter and less divergent,
maybe partly fused. Apex of mesiobuccal root is in line with the
center of the crown . while in 1st molar is in line with the tip of
mesiobuccal cusp.
51. THE MAXILLARY 3rd MOLAR : Most variable in dentition . Most
often absent congenitally. Most commonly , the crown is triangular
in shape having cusps of trigon but no talon. Roots are often fused
and irregular in form .
52. MANDIBULAR MOLARS : Differences with the upper : 1. Mand.
Molar have two roots ,mesial and distal . 2. Derived from a five
cusped form. 3. Are oblong , broader mesiodistally than
buccolingually . 4. The fissure pattern is cross-shaped. 5. Lingual
cusps are more equal size. 6. The tips of buccal cusps are shifted
lingually ,the whole buccal surface is visible occlusally.
53. THE MANDIBULAR 1st MOLAR : Pentagonal in outline. Occlusal
view : Occlusal surface is divided into buccal and lingual by a
mesiodistal occlusal fissure. Buccal side three distinct cusps :
mesiobuccal ,distobuccal , and distal . rounded cusp tips displaced
lingually rounded and lower than lingual cusps . Lingual side two
cusps :mesiolingual , distolingual . large and pointed . Smallest
cusp is the distal
54. 90% of cases mesiolingual and distobuccal are joined across
the floor of the central fossa . this feature and the five cusped
pattern is termd dryopithecus pattern. dryopithecus pattern
sometimes referred to Y5 due to Y-shaped tissue pattern with 5
cusps.
56. Buccal view : Three cusps , distal cusp is the smallest .
buccal surface is markedly convex especially at cervical third.
Lingual view : Mesiolingual cusp appears slightly larger. Fissure
separating the two cusps doesnt extend significantly to lingual
surface. Surface convex then flat or concave cervically.
57. Mesially and distally : Mesial and distal marginal ridges
appear V-shaped . Distal surface is more convex . The roots : Two
roots ,mesial and distal . arise from common root stalk. Mesial
root is usually deeply grooved. Both roots curve distally.
58. THE MANDIBULAR 2nd MOLAR : Occlusal view : Rectangular .
buccal equal to lingual . Four cusps , mesial cusps are slightly
larger than distal cusps . Cusps separated by a cross shaped groove
, complicated by supplementary grooves . Buccal ; Smaller than 1st
molar. Buccal surface is highly convex .
59. Mesial and distal : The proximal surfaces have more equal
convexity. The roots : Smaller , less divergent , partly fused .
Distal inclination is more marked.
60. THE MANDIBULAR 3rd MOLAR : Variable morphology . not as
variable as the max. 3rd molar . Usually 4-5 cusps . rounded
rectangle . Very irregular occlusal pattern. Roots greatly reduced
in size , more fused , marked distal inclination .
61. PULP MORPHOLOGY
62. MAX. PERM. CENTRAL INCISOR : Labial aspect : Pulp chamber
follows the outline of the crown . In young tooth , pulp chamber
has three pulp horns correspond to the mammelones. Distally : Pulp
tapers towards the incisal edge and widen cervically. Cross section
: Ovoid ,becomes round as it nears the apex. With age : Reduced
dimensions of the pulp chamber and root canal . Pulp chamber
recedes and may disappear completely .
63. MAX. LATERAL PERM. INCISOR : Similar to central but
smaller. Root canal is single , slightly ovoid , commonly curves
both distally and palataly.
64. MAND. PERM. CENTRAL INCISOR : Pulp chamber is similar to
max. central , but much smaller . Pulp chamber is oval in cross
section. Root canal is ovoid in cross section. 30% have two canals
, most of them fuse near the apex and exit by single foramen.
65. MAND. LATERAL INCISOR : Tooth and root canal are larger
than central. 43% two root canals more common than cental . Exit by
separate foramina.
66. CANINES : MAX. CANINE : Narrow pulp chamber with a single
pulp horn points cuspally . Pulp chamber and single canal are wider
labiopalataly than mesiopalatly. Root canal doesnt constrict
markedly until apical third . Root canal are ALWAYS single .
67. MAND. CANINE : Pulp cavity resembles max. canine but
smaller in all dimensions . 6% have two root canals usually with
separate foramina.
68. PREMOLARS : MAX 1ST PREMOLAR : 85% has two roots ,
sometimes fused. The two canals exit by separate foramina . Less
than 10% ,single root with single root canal . 5% have three canals
(sometimes in three roots ). Two distinct pulp horns pointing
towards the cusps. Pulp chamber is closest to the surface mesially
. In cross section root canals are generally round.
69. MAX. 2ND PREMOLAR : 75% single root with single root canal
. If two canals are present , mostly they have separate apical
foramina. In cross section the root canal is oval .
70. MAND. 1ST PREMOLAR : Pulp chamber is wider buccolingually .
like max. premolar Usually only one pulp horn extends into buccal
cusp. unlike max. premolar . 75% single root canal . Most teeth
that have two canals have two apical foramina .
71. MAND. 2ND PREMOLAR : 85% have single canals . and usually
two well developed pulp horns pointing towards the cusps.
72. MOLARS: MAX. 1ST PERM. MOLAR : pulp chamber is rhomboidal
in shape , wider buccopalatally. Four pulp horns , one to each
major cusp. The pulp horn to mesiobuccal cusp is the longest . The
floor lies below cervical margin . Three root canals . or four
canals on 60% ( 4th canal in the mesiobuccal root ). 2/3 of the 4th
canals rejoin the main canal of the mesiobuccal root near apex.
Palatal root canal is the widest and longest . Floor of the chamber
is marked by series of developmental grooves that join the orifice
of the root canals.
73. MAX. 2ND MOLAR : Similar to 1st molar pulp cavity but
smaller with the rhomboidal shape more compressed. Roots are more
convergent. Orifices are closer together. Roots are commonly fused.
2nd mesiobuccal canal is less common ( 40% of cases ).
74. MAND. 1ST MOLAR : Pulp chamber is wider mesiodistally than
buccolingually . wider mesially than distally. Five pulp horns
pointing to the cusps. Lingual pulp horns are longer and more
pointed. Floor of chamber lies at or below the level of cervical
margin . The mesial root has two root canals (mesiobuccal and
mesiolingual). Both are circular in cross section. 30% of teeth the
distal root has two canals
75. MAND. 2ND MOLAR : Pulp chamber closely resembles 1st molar.
But it has only four pulp horns. Only rarely (8% of cases)two
canals in distal root.
76. PULP CHAMBERS IN DECIDUOUS TEETH :
77. The chamber is relatively larger and the pulp horns longer
and closer to the surface of the tooth. All incisors and canines
have single canals . 10% on mand. Incisor there are two canals .
Pulp chamber of deciduous mand molar are proportionally larger than
those of max. molars. The mesiobuccal pulp horn is near the
occlusal surface and highly vulnerable to exposure . Small canals
from the floor to the furcation region are common. Severe curvature
of deciduous teeth.
78. Features to bear in mind : - Maxillary D has 2-4 roots
canals (75% 2 canals in the mesiobuccal root and palatal and
distobuccal roots . - Maxillary E has 2-5 root canals (90% of cases
mesiobuccal root contains two canals) , (palatal and distobuccal
roots sometimes fuse and contain a single common canal . -
Mandibular D may have 2-4 canals ( 75% of mesial roots have two
canals , and 25% of distal). - Mandibular E usually has 3 canals
(but vary 2-5) (85% of mesial roots , 25% of distal roots have two
canals ).
79. DECIDUOUS TEETH :
80. Upper A : No mammelons are seen on the incisal margin .
Cingulum is very prominent . Marginal ridges are poorly defined .
Cervical margins are pronounced but less sinuous than permanent
teeth. Compared with permanent incisor , the root is longer in
proportion to the crown.
81. Upper B : Similar to A , one obvious difference is the more
acute mesioincisal angle and more rounded distoincisal angle.
Palatal surface is more concave , marginal ridge more pronounced
.
82. Lower A : Similar to permanent . however ,its much shorter
. No mammelon grooves . Lingual cingulum and marginal ridges are
poorly defined. More rounded root , tends to incline distally
.
83. Lower B : The mesioinciasal angle is more obtuse and
rounded than lower A Distoincisal angle is markedly rounded , it
distinguishes it from upper B . Unlike the permanent , the root is
rounded .and its longer than lower A .
84. Upper C : Similar to permanent ,but more bulbous .
Generally symmetrical , but if there is asymmetry the mesial slope
tends to be longer than distal slope. The width of the crown is
greater than the length. Longitudinal ridges on the labial and
palatal surfaces .it divides the palatal surface into two shallow
pits. Marginal ridges are indistinct . The root is long compared
with the crown height. triangular in cross section .
85. Lower C : More slender than upper C . The crown is
asymmetrical , the cusp tip displaced mesially. Poorly developed
longitudinal ridges on labial and lingual surfaces . The width of
the crown is less than the length . Root is triangular in cross
section .
86. Upper D : Most atypical of all molars , primary and
permanent . Its the smallest molar . Occlusally : - Irregular
quadrilateral .buccal and palatal parallel. - Mesiobuccal angle is
extended to produce a prominent bulge , the molar tubercle. -
Mesiopalatal angle is obtuse. - Generally its a bicuspid tooth .
buccal and palatal . - Buccal cusp is divided by shallow buccal
fissure into two , mesial part is larger. - Palatal cusp may also
be subdivided into two . - Tips of the cusps converge towards the
midline .
87. Buccal aspect : - Height less than width . - On mesial side
lies the buccal cingulum. Mesial and distal : - Cervical bulbosity
of the buccal and palatal surfaces . - Prominent molar tubercle
mesially . - No fissure crosses the marginal ridges . The roots : -
Three roots ( two buccal and one palatal ) arise from a common root
stalk . - The palatal root is the largest. - The distobuccal and
palatal roots maybe partly fused .
88. Upper E : Resembles the max. permanent first molar . Size ,
whiteness , widely diverging roots and low buccal cingulum
distinguish it . A tubercle of Carabelli is often well
developed.
89. Lower D : Occlusally : - Irregular quadrilateral with
parallel buccal and lingual surfaces . Elongated mesiodistally. -
Mesiobuccal corner is extended forming a molar tubercle .
mesiolingual is obtuse . - Buccal and lingual part . mesiodistal
fissure . - Buccal part has two cusps , mesiobuccal is larger . -
Lingual part narrower , two cusps separated by lingual fissure .
mesiolingual is larger. - Transverse ridge connect the mesial cusps
, form a distal fissure and a mesial pit. - Supplemental groove
extends over mesial marginal ridge .
90. Buccal aspect : - The mesiobuccal cusp occupies 2/3 of the
crown. - The profile of mesial is flat and distal is convex .
Mesially and distally : - Buccal and lingual aspects converge
toward the midline . The roots : - Two divergent roots . mesial and
distal . - Mesial root is often grooved .
91. Lower E : A small version of lower first permanent molar .
Narrower , whiter , widely diverging roots. The mesiobuccal corner
of the crown ,the greater convexity of the mesial and distal
surfaces . The mesiolingual and distobuccal cusps are not usually
joined to give the Dryopithecus pattern .
92. ETHIC AND RACIAL DIFFERENCES IN TOOTH MORPHOLOGY