• Condyle process at the level of the upper border of mandible.
• Coronoid process at higher level than condyloid.
• Mental foramen near the lower border under the crypt of D
• Mandibular canal near lower border
• Sigmoid notch is shallow
• Mandible two half till the end of the first year.
• Angle of the mandible 170 degree.
cartilage(Symphysis of mandibule
2parts fuse at 1 year
of the ramus
process + anterior
part of the ramus
• Coronoid process higher than condyloid process.
• Mental foramen midway between upper& lower border.
• Mandibular canal slightly above mylohyoid line.
• Sigmoid notch more deeper.
• Angle of the mandible 140 degree.
• Chin is poorly developed.
Increase in length by bone
remodeling make room for
Increase in height by
eruption of teeth +alveolar bone
formation+ bone deposition at lower
border of the mandible
• Condyle process at a higher level than coronoid process.
• Sigmoid notch deepest.
• Mental foramen mid way between upper & lower border
under the socket of lower 5.
• Angle of the mandible 110-120 degree.
• Chin is significantly prominent ----- mental protuberance.
• Condyloid process at a lower level than coronoid process
• Sigmoid notch is shallower.
• Mental foramen near the upper border of the mandibule.
• Mandibular canal near the upper border.
• Angle of the mandible 140 and the ramus inclined posterior.
• Body of the mandible has reduction in height due to loss of teeth and
At adult period
At old age
• Bonwill described the
mandible and the
mandibular dental arch
form occlusal view as
an equilateral triangle
of 4 inches length.
• The apex of the
triangle is at the mesial
contact area of lower
central incisors and the
angles of the base at
the centers of the
1- These are the curved plane to which the teeth are
arranged in the dental arch.
2- They provide balance in all mandibular movement.
The curve of Spee in sagittal
plane (Lateral view).
Spee stated that when the
upper and lower jaws are
examined from a point
opposite the first molar
buccally the incisal ridges
of anterior teeth and the
buccal cusps of posterior
teeth follow a curve that
end at the anterior surface
of the condyle.
Curve of Spee allows for the
normal functional protrusive
movement of the mandible.
Curve of Spee:
*Curve of the mandibular arch is concave from
the level of occlusion.
*Curve of the maxillary arch is convex.
• Crowns of the upper posterior
teeth are inclined buccally so
lingual cusps appear longer than
• Crowns of the lower posterior
teeth are inclined lingually so
buccal cusps appear longer than
• If a line is drawn from the buccal
cusps of a posterior tooth on one
side to a buccal cusp of the same
tooth on the other side of the
same arch, it will follow a curve
parallel to the coronal plane. This
is the curve of Wilson.
Curve of Wilson
• The curve formed by an
imaginary line touching the
buccal and lingual cusp tips of
similar teeth on each side of the
• The inclination of the posterior
teeth increase in backward
direction so the curve of wilson
is more curved in backward
• Typically, viewed in the frontal
plane (However, to improve
visibility, this image is viewed
from the posterior)
Curve of Wilson:
* Allows for those exquisite
movements which are used in
* The elevated buccal cusps prevent
food from going past the occlusion
Curve of Wilson :
convex in maxillary arch & concave
in mandibular arch
change from first molar to third
molar and with wear of the
What is the difference between the curve of Spee and the curve of Wilson?
The buccal cusp tips of posterior
teeth , seen in alignment from a
lateral view , conform to the curve
of Spee in an anterior to posterior
The curve of Wilson is a
transverse occlusal curve which
exists for posterior teeth in a
direction from right to left as
seen from a posterior view.
Curve of Spee:
of the incisal &occlusal
Buccal - Lingual Curvature.
For mastication. the Curve of Wilson.
Clinically, it relates to the anterior overbite:
the deeper the curve, the deeper the overbite.
Curve of Monson: Curve of Monson is the curve of occlusion
in which each tooth cusp and incisal edge touches or conform
to a segment of a surface of a sphere 8 inches (20 cm) in
diameter, with its center in the region of the glabella.
• When teeth are properly aligned in the
dental arches, their incisal and occlusal
surfaces adapt themselves to curved
• The occlusal surfaces of the mandibular
teeth form a concave plane .Those of
maxillary teeth form a convex plane .In
centric occlusion these planes become
Monson stated that the curved occlusal surfaces of the
dental arches conform to a segment of a sphere of 4 inches
radius. The center of this sphere is in the glabella.
Curve of Monson is a combination of curve of Spee and
curve of Wilson.
The importance of these curved planes is to assist the path
of condyles of the mandible in its movement.
Sphere of Monson
It is a combination of Spee and Wilson curves , these curves are
studies in a three dimension occlusal model the cusps tips of posterior
teeth resting on a sphere. Sphere of Monson :sphere existed with a
radius of 4 inches
Center of Monson’s Sphere
( located in the gabella
above the condyles)
• The functional form of the crown at incisal and occlusal third, is
manifested by elevations and depressions. Elevations of the crown
in one dental arch occlude with depressions on the opposing teeth
during centric occlusion (self occluding design).
• Ridge to fossa : Incisal ridge of lower 1& 2 rest in the lingual fosse
• of upper 1& 2.
• Cusp to fossa: MLC of upper molars rest in central fossae of lower
• molars & DBC of lower molars rest in central fossae of
• upper molars.
• Cusp to ridge: BC of lower 4& 5 hits MMR of upper 4&5 in
• Cusp to sulcus: the triangular ridge of the MBC of upper molar are
• accommodated to the BG of the lower molars.
• Cusp to embrasure: the DBC of the maxillary molars lie in
the B. embrasure between lower molars.
• Escapement spaces : the rounded surfaces of teeth make
escapement of food during mastication.
Ridge to fossa
• It is the contact relation of upper and lower
teeth when they are in the maximum inter
cuspation and the condyles are in the most
retruded unstrained position in glenoid
• The first permanent tooth to develop &
• The largest of the permanent teeth.
• Their eruption is guided distal to the
• Their eruption is not disturbed as they
have no deciduous predecessors.
• The upper 6 is more important as a key
of occlusion as it is attached to a fixed
bone (the maxilla).
1- each tooth contacts 2 teeth from the other arch except lower
1and upper 8.
2- All upper teeth overlap the lower teeth vertically and it called
3- All upper teeth have a labial relation to the lower teeth in
centric occlusion and it called overjet.
• Guiding cusps:
cusps free of contact during centric occlusion (buccal
cusps of upper teeth & lingual cusps of lower).
• Supporting cusps:
cusps that occlude with fossae or marginal ridges of
opposing teeth in centric occlusion (palatal cusps of upper
teeth & buccal cusps of lower teeth).
• Centric stops:
points of occlusal contact made by supporting cusps
with opposing teeth in centric occlusion.
1-Buccal of upper (guiding cusps)
- incisal edge of upper anterior & buccal cusps of upper
premolars & molars are all free of contact.
- Cusp of upper canine, Buccal cusps of upper premolars & disto-
buccal cusp of 7 lie in the buccal embrasure.
- Buccal cusps of 6 & mesio-buccal cusp of 7 & 8 lie in the
2- Buccal of lower: (supporting cusps)
-Buccal cusps of lower 4 & 5 hit the MMR of opposing teeth having
the same number.
- Mesio-buccal cusps of lower 6 & 7 hit the MMR of
upper teeth having the same number + the DMR of
the tooth before.
-Mesio-buccal cusp of lower 8 hits the mesial triangular fossa of the 8 .
- Disto- buccal cusps of lower molars hit the central fossae of upper
- distal cusp of lower 6 rest in the distal triangular fossa of 6.
- Cingulum of lower 2, 3 & lingual cusps of posterior teeth are free of
- Lingual cusps of lower premolars & mesio- lingual cusps of lower
molars lie lingual to the lingual embrasure.
- Disto-lingual cusps of lower molars lie lingual to the lingual
grooves of upper molars.
lingual surface (Supporting cusps):
- Lingual cusps of upper 4 & 5 hit the DMR of lower 4 & 5.
- In case of 3 cusp type lower 5 the lingual cusp of upper 5
contact the disto-occlusal cusp slope of the disto lingual
- MLC of upper molars contact the central fossae of the lower
- DLC of upper 6 hits the MMR of lower 7.
- DLC of upper 7 & 8 hit the distal cusp ridge of lower 7 & DMR
of lower 8 respectively.
• Movements of the mandible:
*Bilaterally symmetrical *Bilaterally
*Depression &Elevation. *Right lateral.
*Protrusion & Retrusion. *Left lateral.
• All mandibular movements start from and
terminate to centric occlusion.
1-The mandible is depressed.
2-Moves forward (Protrusive movement)
bring teeth together in the best position for incision
(the lower teeth are in anterior relation to centric
1- The mandible is depressed.
2- Retrusion of the mandible :
placement of the teeth posterior to centric
occlusion (non functioning occlusion).
3- Retrusive is limited by the compressibility of the
tissues posterior to the condyles.
*The mandible moves in downward and forward direction to
make lower anterior teeth in anterior relation to the upper
* The functioning side is located at anterior teeth & balancing
side at posterior teeth.
* The incisal edge of lower teeth are in contact with lingual
third of upper teeth (working side)
*Posterior teeth in anterior relation of the lower teeth to
the upper teeth (balancing side)
Then the mandibule glides upward and backward
1-Tthe mandible is depressed (the dental arches
2-Moves to a right position to centric occlusion.
3-The right side is termed the working side
* The buccal cusp of maxillary & mandibular teeth
are in contact
*The lingual cusps of lower posterior teeth
contact the lingual cusps of upper posterior
4-The left side is termed the balancing side:
* The lingual cusps of maxillary teeth contact the
buccal cusps of mandibular teeth.
• The left lateral movement is similar to the right one in
opposite direction the left side is the (working side & the
right side is the balancing side)
5-Return to centric occlusion by sliding of teeth against each
other in a direction nearly parallel to the oblique ridge of upper
6-The lateral movement is repeated again till grinding of the
The cycle of occlusal movement
contact in right
Final contact after leaving
centric relation before the
mandible drops away to
begin another cycle
• The lower anterior teeth strike the
upper anterior teeth lingually above
their incisal ridges.
• Upper A: lower A&m1/3 of lower B.
• Upper B: d 2/3 of lower B and
mesial part of lower C
(mesial to its cusp tip).
• Upper C: d part of lower C (distal
to cusp tip) and m part of
• Upper D: d 2/3 of lower D and m
part of lower E.
• At the age of 4&5 years diastema due to
jaw growth and increase with further
• Occlusion is supported by eruption of
permanent first molar at 6 years.