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It is the contact relation ship of upper & lower teeth
during various mandibular movements.
The study of occlusion includes the following items:
1- Dental arch formation.
2- Compensating curvatures of the dental arch( curved
3- Compensatory curvatures of individual teeth (curved
4-Angulation of teeth in relation to various planes.
5- functional form of the teeth at their incisal and
6-Facial and lingual relation of each tooth in one arch
to its antagonist in the opposing arch during centric
7- Occlusal contact and inter-cusp relation of all teeth
during various mandibular movement.
(Arrangement or Alignment of teeth)
From an occlusal view the facial and lingual outlines of the
dental arch conform to a Parabolic curve.
The maxillary arch is larger than the mandibular arch
giving a horizontal space between upper and lower teeth
during occlusion called overjet.
Phases of development of permanent dental arch.
equally bisected by the
Facial surfaces of
anterior teeth and the
first premolar of both
2- Middle segment:
Straight line and
continuous with the
anterior segment in
Included the first and
second premolars and
the mesial half of the
3- Posterior segment:
Straight line parallel
to the midline
slightly directed to
the midline in the
First phase: Second phase:
At 6 years eruption of
the first permanent
molars lead to
efficiency and jaw
Eruption of the
Third phase: Fourth phase:
Premolars replace the
and spacing of teeth
occur due to smaller
size of premolars
The canines and the
molar erupted nearly at
the same time. The
arch is considered to
Eruption of the
the mandible and the
arch form occlusal
view as an
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
The curve follows a sagittal
plane. 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
Crowns of the upper posterior
teeth are inclined buccally so
lingual cusps appear longer
than buccal cusps.
Crowns of the lower posterior
teeth are inclined lingually so
buccal cusps appear longer
than lingual cusps.
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.
When teeth are properly aligned in the
dental arches, their incisal and
occlusal surfaces adapt themselves to
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 identical.
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
-Occlusal balance and
stability of teeth during
drift of teeth.
Any line bisecting the tooth
from any aspect will form a
The curves made by teeth in
either dental arch, is parallel
to those in the opposing
The curves made by anterior
teeth, premolars and first
molar form equal circles.
The second and third molars
Each tooth is positioned in the dental arch at
an angle that best withstands the forces of
The axial angulation of the incisors is about
60 degrees to the horizontal plane.
The axis of the maxillary incisor forms acute
angle with the axis of the mandibular incisor.
The angle becomes less acute in the canines
and first premolars.
The maxillary and mandibular second
premolar and the first molar have their axes
parallel to each other.
The second and third molars have their axes
at an angle more acute to the horizontal plane
than the first molar.
Function: - Stabilize proximal contact.
Angulation of the teeth
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 crown depression
on the opposing dental arch during centric occlusion (self
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
6-Facial and lingual relations of each
tooth in one arch to its antagonist in the
opposing arch in centric occlusion
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 fossa.
The first permanent tooth to develop & erupt.
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
1- each tooth contacts 2
teeth from the other arch
except lower 1and upper
2- All upper teeth overlap
the lower teeth vertically
and it called overbite.
3- All upper teeth have a
labial relation to the
lower teeth in centric
occlusion and it called
4- All incisal ridges of
upper incisors, buccal
cusps of upper premolars
and molars are free of
* The cusp of the upper 3,buccal
cusps of upper 4&5 and the DBC of
the upper molars are labial to the
labial embrasure of the tooth
having the same no and the next
* The MBC of upper molars are
buccal to the BG of the tooth
having the same number.
5- All incisal ridges of lower teeth,
lingual cusps of lower premolars
and molars are free of contact.
* the cusp of the lower 3, the lingual
cusps of lower 4&5 and the MLC of
6&7&8 are lingual to the lingual
embrasure of the tooth having its
number and the tooth before
* The DLC of lower molars are
lingual to the tooth having the
6-The BC of lower 4&5 hits the
MMR of the upper tooth
having the same number.
7-The MBC of lower 6&7 hits MMR
of the upper tooth having the
same number and the DMR of
the tooth before.
8-MBC of lower 8 hits MMR or MTF
of the upper 8.
9-All DBC of lower molars hit CF of
the upper molar having the same
10-All upper and lower teeth end at
one line distal to the upper and
11-All the MLC of upper molars hit
the CF of the lower tooth having
the same number.
12-The DLC of upper molars hit the
DMR of the tooth having the
same number except that of the
upper 6 hit the MMR to the lower
13-The LC of the upper 4 hits the DC
slope of the lower 4.
14-The LC of the upper 5 have two cases:
* if the lower 5 is 2 cusps type it hits the DTF of the
* if the lower 5 is 3 cusps type it hits the DC slope of
the lingual cusp of lower 5.
cusps free of contact in centric occlusion (buccal
cusps of upper teeth & lingual cusps of lower).
cusps making contact in centric occlusion.
points of contact made by supporting cusps with
opposing tooth in centric occlusion.
Each tooth contact 2 teeth except lower1& upper 8.
1-Buccal of upper
-incisal edge of upper anterior & buccal cusps of upper premolars & molars are all
free of contact.
-Buccal cusps of upper premolars& molars lie in the buccal embrasure or buccal
groove. -1&2 , over lap lower1&2&3
-3&4&5 lie in buccal embrasure. Molars MBC lie in buccal grooves & DBC lie in
2- Buccal of lower:
Buccal cusps of lower 4 & 5 lie in MMR of opposing teeth having the same number.
Molars : DBC lie in central fossa of opposing teeth having the same number. MBC
lower 6&7 lie in MMR of opposing +DMR of the tooth before. Lower 8 with MMR of 8 .
N.B. distal cusp of lower 6 rest in the distal
All lingual surfaces and cusps of lower teeth are free of contact:
1-lingual surface of lower:
*lingual cusps of lower 4 & 5 are free and lie in lingual embrasure
*ML cusps of lower 6& 7& 8 lie in the lingual embrasure.
*DLC of 6&7&8 lie in the lingual grooves of upper 6 & 7& 8.
2-lingual surface of upper: lingual surface of upper1& 2& 3 are free of contact.
Lingual surface of upper4&5 ,the lingual cusps contact DMR of lower 4&5 N.B.
in case of 3 cusp type lower 5 the lingual cusp ofupper5 contact the disto occlusal
Lingual cusps of molars
MLC, contact central fossa of molars having
the same number.
DLC, contact DMR of molars having the same
number except upper 6 contact MMR of lower
*N.B. cingulum of upper anterior is in the
lingual embrasure of lower anterior.
*Cingulum of lower anterior is free from
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 lower D.
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 growth.
Occlusion is supported by eruption
of permanent first molar at 6 years.
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 occlusion).
teeth slide over each other backward and upward to centric
The incisal ridges of upper and lower incisors contact each
other. While sliding back upper and lower incisors still
contact each other until they rest in centric position.
4-The mesial cusp ridge of lower 4 contact the distal cusp
ridge of upper 3.
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.
1-Tthe mandible is depressed (the dental arches are
2-Moves to a right position to centric occlusion.
3-The right side is termed the working side
*The buccal cusps of lower posterior teeth contact
the upper posterior teeth buccal to the buccal
*The upper posterior teeth make their contact
lingual to their buccal cusp ridge.
*The lingual cusps of lower posterior teeth contact
the lingual cusps of upper posterior teeth
*The lingual cusps of upper posterior teeth contact
the lingual cusps of the lower posterior
4-The left side is termed the balancing side:
*the occlusal slopes of the buccal cusps of lower
molars contact the occlusal slopes of the lingual
cups of upper posterior teeth.
5-Return to centric occlusion by sliding of teeth
each other in a direction nearly parallel to the oblique
ridge of upper 6.
6-The lateral movement is repeated again till grinding
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)
The cycle of occlusal movement
contact in right
Final contact after
leaving centric relation
before the mandible
drops away to begin