OCCLUSION (Seminar).doc

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INTRODUCTION
According to angle, occlusion can be defined as the normal relation of the occlusal
inclined planes of the teeth when the jaws are closed.
Gregory puts it as the changing interrelationship of the opposing surfaces of the
maxillary and mandibular teeth, which occurs during the movement of the mandible and the
terminal full contact of the maxillary and mandibular dental arches.
Occlusion of teeth is not a static condition as the mandible can assume various
positions. Occlusion may be centric, habitual, mesial, distal, eccentric, labial, supra, infra etc.
Ideal occlusion is a hypothetical formula, which does not and cannot exist in man. It
necessitates an unblemished heredity, an optimum favourable environment and a
developmental history devoid of any accident or disease.
Maxwell concept of ideal occlusion requires
a) Normally developed coronal contour of properly coordinated mesiodistal and
buccolingual dimensions.
b) Normally developed tooth and osseous muscular and other anatomic structures.
c) A definite geometric and anatomic, individual and collective relationship of
cranium and mandible.

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OTHER DEFINITIONS
STATIC OCCLUSION :- Is the form, alignment and articulation of teeth within and
between the arches, and the relationship of teeth to their supporting structure.
DYNAMIC OCCLUSION : It refers to the function of the stomatognathic system as a
whole comprising of teeth, supporting structure, TMJ, neuromuscular and nutritive systems.
PHYSIOLOGIC OCCLUSION : Occlusion that deviates in one or more ways from the
ideal yet it is well adapted to that particular environment, is esthetic and shows no pathologic
manifestations or dysfunction.
ORGANIC OCCLUSION : Is the one in which all the parts are mutually dependent or
intrinsically related having systematic co-ordination. The parts are organized i.e. an overall
perceivable pattern into which the parts can be filled to make a whole.
THERAPEUTIC OCCLUSION :- An occlusion that has been modified by appropriate
therapeutic modalities in order to change a non physiological occlusion to are that is least
physiologic if not ideal.

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FACTORS FOR ACHIEVING NORMAL OCCLUSION
Normal occlusion is dependent on several factors :-
- The position, size and relationship of the bone in which tooth develops.
- The position & relationship of the tooth within the bone.
- The path, which the tooth follows to reach the mucous membrane before eruption.
- The forces, which guide its course after eruption.
- Force which start to operate when the tooth contacts its opponent.
BONE RELATION :
The relationship of the maxilla or mandible to other bones and to each other is
probably determined by a number of factors like hereditary, congenital, hormonal imbalance,
traumatic and pathological condition which interfere with growth.
HORAWITZ in 1958, said that heredity is significant in influencing the development
of normal occlusion by controlling:-
- The width and length of the palate
- Height of the palate.
- Crowding and spacing of the teeth
- Position and conformation of perioral musculature and shape and size of the
tongue.
- Soft tissue peculiarities - character and texture of the mucosa, frenum size, shape
and position.
The development and growth of the craniofacial skeleton with associated soft tissues
and the primary teeth, and a few permanent teeth being prenatally and an interference with
this development, either due to nutritional, metabolic or other systemic influences drugs or
trauma may all result in malocclusion.
Eg: In congenital syphilis, screw driver shaped teeth and mulberry molars are seen.
Birth injury to TMJ causes ankylosis and affects mandibular growth.
Cerebral palsy i.e. paralysis or lack of muscular coordination effects mastication,
deglutition, respiration and speech and upsets muscle balance which is necessary for the
establishment and maintenance of normal occlusions.
According to Nanda, there is some evidence that the developmental position of a tooth
is also under strong hereditary control, similar atypical malposition of individual teeth are
seen in twins and siblings.
During intraalbeolar eruption, the tooth is affected by the presence or absence of
adjacent teeth, resorption of primary teeth, early loss of primary teeth, localized pathologic
conditions and any factors that alter the growth or conformation of the alveolar process.
FACTORS AFFECTING ERUPTION
Mechanical disturbance can alter the plan of eruption causing localized pathosis,
perapical lesions, pulpitis and pulpotomy of a primary molar will hasten the eruption of the
successor premolar. If the primary tooth is extracted prior to the onset of permanent tooth,
root formation there will be delayed eruption of the permanent tooth since the alveolar
process may reform atop the successor tooth making eruption more difficult and slower.
Intrusion or extrusion of the primary incisors may occur accidentally during early childhood,

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resulting in disturbance in mineralisation of the permanent successors and in some instances
intrusion of the successors.
It is also seen that unfavourable eruption sequence also results in malocclusion.
Therefore we need to know the favourable sequence.
Its 6 1 2 4 5 3 7 in maxilla
6 1 2 3 4 5 7, in mandible
FACTORS DETERMINING TOOTH POSITION DURING ERUPTION :-
When the teeth occlude with those of the opposite dental arch (occlusal stage of
eruption) a most complicated system of force determines the position of the tooth.
The muscles of mastication exert an influence through the interdigitation of the cusps.
The upward forces of eruption and alveolar growth are countered by apposition of the
apically directed forces of occlusion. The periodontal ligament disseminates these strong
forces of chewing into alveolar bone. The axial inclination of the permanent teeth is such that
some of the force of chewing produce a mesial resultant force, through the contact point of
the teeth. THE ANTERIOR COMPONENT OF FORCE, which is the result of muscle forces
acting through the intercuspation of the occlusal surfaces. The mesial drifting tendency is an
internal disposition of most teeth, even before they are in eruption.
INTRA ORAL FORCES :-
The forces encountered by the tooth may be divided into buccolingual and mesiodistal
forces (exerted by adjacent teeth). Forces generated by the muscles may be either passive or
active.
Passive :- Certain muscles exert a constant tension (muscle tonus) upon the jaws. In this
state, a small proportion of fibers contract, the proportion of fibers is constant, but they are
not always the same fibers.
The muscles, which have a direct effect on the jaws are those of deglutition,
expression and mastication. The tongue acts within the lingual vestibule exerting buccally
directed forces.
The lips and cheek apply forces to the labial and buccal surfaces. At the same time,
there is a tension from orbicular oris muscle on the upper incisors.
Active muscle force exert pressure only intermittently, but to a greater degree eg.
deglutition.
To summarise, the stability of dental relationship is determined by buccinator
mechanism and tongue.
Winders (1956) measured the force of perioral and lingual musculature on the
dentition and found that the tongue was capable of exerting more lingual pressure (2-3 times
more force) than the labial/buccal musculature. These findings suggested an inbalance in
muscle force in the normal condition (confirmed by Kydd in 1957).
Briggs in 1965 and Lear et al (1965) found that a normal adult in an average,
swallows 585 times a day with a range of 233-1008 times.
According to Profitt, a typical individual swallows about 800 times per day, while
awake but has only a few swallows per day while asleep. The total swallows per day
therefore is usually less than 1000 times, 1000 seconds of pressure which accounts for a total
of only a few minutes, not nearly enough to effect the equilibrium.
Tongue pressure in the maxillary incisor region has been determined to be 75  25 g
per swallow.

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On palate & molar teeth it is about 100  30g/cm, on mandibular incisors and molars
it is about 90g/cm.
The restrictive influence and the force exerted by perioral musculature can be
explained by a study of buccinator mechanism. It is actually an intermingling of fibers of all
perioral muscles to constitute a functioning unit. Anteriorly, the superior & inferior fibers of
orbiculars oris decussate with Zygomaticus, Levator anguli oris, Platysma and laterally with
the buccinators. The buccinator posteriorly inserts into the pharyngomandibular raphae just
behind the dental arches. The fibers of superior constrictor muscle decussate at this point and
continue prosteriorly and medially to attach into the pharyngeal tubercal of occipital bone.
The buccinator complex of muscles acts like a rubber bondage around the dentoalveolar
region and is important in the maintenance of equilibrium and stability of dentition.
POSTURE OF LIPS :- In cases with small interlabial gap, the lip contraction required for
lip seal is minimal, whereas in case of a large interlabial gap with small lip length, there may
be significant muscular activity and a contraction of mentalis muscle. Due to the contraction
of mentalis muscle the chin will be flattened and moves the inferior facial sulcus upward and
forward in an attempt to close the lips increase the posterior component of forces on the
incisor.
TONGUE POSITION :-
Tongue size, position and function may be a direct cause of or an important
contributory factor in the development of malocclusion.
A large tongue is responsible for wide well developed dental arches, buccal and labial
inclination of teeth with spacing and occasionally leads to anterior and posterior openbite. If
the tongue is too small the dental arches are narrow and the teeth in the buccal segments are
lingually inclined.
The position of the tongue will also be affected by craniofacial morphology. A small
gonian angle and a flat mandibular plane will provide more space for the tongue. In other
cases, when high mandibular plane and large gonial angle provides less space for the tongue.

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DEVELOPMENT OF OCCLUSION
The periods of occlusal development :-
- Pre dental period
- The deciduous dentition period
- Mixed dentition period
- Permanent dentition
MOUTH OF A NEONATE :-
The alveolar arches at the time of birth are termed gumpads, which are firm and pink
in color. They develop in 2 distinck parts - labio buccal and a lingual portion.
The labiobuccal part is differentiated first and grow more rapidly. It is divided by
transverse grooves into 10 segments each corresponding to a deciduous tooth sac and is
papillomatous at first. The groove between the canine & 1st deciduous molar is called lateral
sulcus. It is useful in judging the interarch relationship at an early stage. The lingual portion
is separated from the labial buccal by a dental groove.
The gingival groove separates the gumpad from the palate and floor of mouth. The
transverse groove divides the gumpads into 10 segments.
The lower gumpad is V shaped & the alveolar pad is limited on the lingual aspect by a
continuous groove. Anteriorly the gumpad is slightly everted labially. The transverse groove
is not a clear as upper. The upper gumpad is wider than the lower and when the two are
approximated, there is a complete overjet all round. In the anterior region, there is nearly no
contact between the gum pads when approximated (helpers in suckling) and the contact is
seen only in 1st molar region.
At rest, the gum pad are separated by the tongue, which protrude over the lower gum
pad to lie immediately behind the lower lip or may even protrude a little between the lips.
The antero-posterior movement of the gum pad are usually small and there is no
lateral movement.
At birth, the gum pad are not sufficiently wide to accommodate the developing
incisors which are crowded & rotated in their crypts. But during the 1st year of life, the pads
grow rapidly and the growth is marked in the lateral direction. This increase permits good
alignment.
According to Leigton, the size of gum pad at birth is determined by
- State of maturity of infant at birth
- Size at birth as expressed by birth weight.
- Size of developing primary teeth
- Purely genetic factors.
DECIDUOUS DENTITION PERIOD :-
Initiation of deciduous dentition starts within the first 6 weeks of intra uterine life.
Eruption begins by 6 months after birth and is completed at about 2½ - 3½ years when the 2nd
molars come into occlusion.
The emption sequence is ABDCE. Between 3-6 years, the dental arch is relatively
stable and very few changes occur.
Teething : 60% of infants exhibit disturbances such as rhinorrhea, irritability diaorrhea,
which occur for a short time before tooth eruption and resolve after emergence of tooth.

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Characteristics of primary dentition :
- spaced anteriors
- primate space
- deepbite
- straight terminal plane
- almost vertical inclination of anterior teeth.
- Ovoid arch form.
SPACING IN PRIMARY TEETH :
Was 1st described by Dellabarre in 1819. It was called physiological spaces by
Korkhous & Newmann and developmental spacing by Fraber in 1962.
Spacing around canines [mesial to upper canine and lateral to lower canine] are
named as simian gap by BAUME in 1940.
It was renamed as ANTHROPOID SPACES by FOSTER & HAMILLON in 1969.
Any spaces which exist between the deciduous molars usually close by the time of
eruption of 1st permanent molars. But the spaces between deciduous incisors persist until
teeth are replaced.
Where the deciduous incisors erupts ,the overbite of the upper incisors are equivalent
to the height of the crown of lower incisors, that is the lower incisor are covered by the upper
when the teeth are in occlusion. The overbite is reduced progressively by the eruption of
deciduous molars and by more rapid attrition of incisors.
Spaced primary arches produce favourable alignment of permanent incisors. The
presence of mandibular primate space is conducive of proper molar occlusion by means of an
carly shift of mandibular primary molars into this primate space on eruption.
The age at which deciduous dentition teeth erupt are
Teeth maxillaky mandibular
Central 7½ months 6½ month
Lateral 8 7
Canine 16-20 (182) 16-20 (16)
1st molar 12-16 (142) 12-16 (12)
2nd molar 20-30 (24) 20-30 (20)
In most of the deciduous dentition, the distal surface of the maxillary and mandibular
2nd primary molars are in the same vertical plane called the flush terminal plane. Later on
when the maxillary and mandibular 1st permanent molars erupts, they are guided into the
dental arch by distal surfaces of 2nd primary molars.
The permanent lower molar have to move 3-5 mm to get into a normal occlusion. It is
achieved by early mesial shift in spaced dentition by utilizing the primate space.
- Late mesial shift after the loss of 2nd primary molar
- Greater forward growth of mandible than maxilla
- Or a combination
- Utilizations of leeway space of nance i.e. the combined mesiodistal width of the
primary cuspid & molars is greater than the permanent canines & premolars.
In the maxilla it is about 0.9mm per quadrant & 1.7mm in the mandible.

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DISTAL STEP : Here the distal surface of lower 2nd DM is more distal to that of upper. The
1st molar also erupt in the same relationship and may land up in class II.
MESIAL STEP : When the mesiobuccal cusp of maxilliary primary molar occludes with the
buccal groove of the mandibular 2nd primary molar, mesial step is produced.
Under there conditions, the 1st permanent molar upon eruption will approximate the
class I adult molar relationship. It may also develop into class III depending on the magnitude
of mesial step, leeway space & differential growth of maxilla and mandible.
THE PERMANENT DENTITION :
The cusps of the 1st permanent molars is formed at birth. Eruption is the
developmental from that move a tooth from its crypt position through the alveolar process
into the oral cavity and to occlusion with its antagonist. During eruption of succedaneous
teeth, following events occur simultaneously.
- Primary teeth resorbs
- Root of permanent tooth lengthens
- Alvcolar process increase in height
- Permanent tooth move through the bone.
STAGES OF TOOTH DEVELOPMENT BASED ON THE WORK OF NOLLA.
0 - Absence of crypt
1 - Present Of Crypt
2 - Initial Calcification
3 - 1/3 Of Crown Completed
4 - 2/3 Of Almost Completed
5 - Crown Almost Completed
6 - Crown Completed
7 - 1/3 Of Root Completed
8 - 2/3 Of Root Completed
9 - Root Almost Complete, Open apex
10 - Apical End Of Root Completed.
The teeth generally erupt when 2/3 of its root is completed, showing that periodontal
ligament is essential for eruption.
It takes 2-5 years for posterior teeth to reach alveolar crest following completions of
their crown and 12-20 months to reach occlusion after reaching alveolar margin.
PREEMERGENT ERUPTION : During the period when the crown of a tooth is being
formed, there is a very slow labial or buccal drift of the tooth follicle within the bone.
POST EMERGENT ERUPTION : The stage of relatively rapid eruption from the time a
tooth 1st penetrates the gingiva until it reaches the occlusal level.
This is followed by a period of very slow eruption called JUVENILE OCCLUSAL
EQUILIBRIUM.

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It has also been shown that the eruption occurs only during 8PM to 1AM at other
times, tooth stops erupting or may be intruded to some extent.
During the juvenile equilibrium, teeth that are in function erupt at a rate that paralles
the rate of vertical growth of mandibular ramus.
Since the rate of eruption parallel the rate of jaw growth, pubertal spurt in eruption of
teeth accompanies the pubertal spurt in jaw growth. When the pubertal growth spurt ends, a
final phase in tooth eruption called the adult occlusal equilibrium is achieved.
ERUPTION SEQUENCE OF PERMANENT TEETH :
MAXILLARY MANDIBULAR
Central 7-8 years 6-7 years
Lateral 8-9 years 7-8 years
Canine 11-12 years 9-10 years
1st premolar 10-11 years 10-12 years
2nd premolar 10-12 years 11-12 years
1st molar 6-7 years 6-7 years
2nd molar 12-13 years 11-13 years
3rd molar 17-21 years 17-21 years
In the mandible, the most favourable
Eruption sequence - 3 4 5 7
In the maxilla - 4 5 3 7
THE CHANGES FROM DECIDUOUS DENTITION TO PERMANENT DENTITION:
1) Replacement of primary incisors (1st transition period)
The permanent incisor teeth are considerably larger than the primary teeth. The
maxillary arch has initially enough space for the accommodation of permanent lateral
incisors when they erupt.
In the mandibular arch however, when the lateral erupt, there is an average 1.6mm
space available for the four mandibular incisors that required. This difference between the
amount of space needed & that required is called INCISOR LIABILITY which is 7mm in
the maxilla and 5mm in the mandible.
The incisor liability can be compensated by
1) Interdental spacing in the primary dentition. The space are about 4mm is maxilla and
3mm n the mandible.
2) Increase in intercanine width. The intercanine width increase markedly at the time of
eruption of mandibular & maxillary lateral incisors.
According to Moorees and Chanda (1959) by the time the central incisor have
completed their eruption, the intercanine width increase by about 3mm in each arch.
Furthermore in the maxilla, the intercanine width increase by another 1.5mm when the
canines erupt. More width is gained in the boys than the girls. Therefore the girls have
greater liability to have incisor crowding especially mandibular incisor crowding. Clasps
on the cuspid attached to the space maintenance must be out off at this time or should be
designed so as to allow natural increase of intercanine width.
3) Change of tooth axis of incisors :

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Primary teeth are generally very upright but permanent teeth tend to incline more
laterally or buccally.
This contributes to 1-2 mm of additional space.
UGLY DUCKLING STAGE :-
The term was 1st introduced by Broadbent to describe the midline diastemas in the
maxillary arch along with overlapping of the permanent lateral incisor about the age of 8-
9 yrs.
The mandibular permanent central incisor are almost in proximal contact from the
time they erupt. In the maxillary arch, when the canines erupt, a midline diastema is
present which shows the beginning of ugly duckling stage.
By the 7th year, the crown of permanent cuspid have been completed, but they have
not yet moved from their sight of origin. The crown of the cuspid in the young jaw
impinge on the developing roots of laterals driving the roots medially and causing the
crown to flare laterally. The roots of central are also forced towards each other.
Changes during 6-8 years :-
As the upper laterals develop in a more palatal position than the central incisor, they
are overlapped by the latter. When central incisor erupt, the lateral incisor becomes free to
move labially but their apices always remain slightly more palatal to those of central
incisors.
The crown of the lateral incisor have a slight distal initiative and there is a partial
closure of midline spaces as they erupt. The distal inclination of the lateral incisor is due
to the developing canine which are high and closely associated with the root of erupting
lateral incisors and exert pressure on the apices resulting in distal tilt of the crown of the
lateral.
About 11 years the root of lateral incisors are complete and maxillary canine erupt at
about 11½ years. As they erupt the canines move labially exerting a mesial pressure
resulting in closure of central diastema.
If the diastema is less than 2 mm spontaneous closure occurs and therefore treatment
is not indicated. If the diastema is greater than 2mm, spontaneous closure is unlikely
therefore treatment is indicated.
2nd MOLAR ERUPTION : In most case, just prior to eruption of 2nd m, the dental arch
length with be reduced by eruption forces immediately mesial and with 2nd molar. With
the eruption of 2nd molar in the permanent dentition, the arch circumference may become
shorter than that of the primary dental arch by the utilization of the leeway space.

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DETERMINANTS OF OCCLUSION
The determinates can be grouped into two – fixed & variable
Fixed - Angulations & curvature of condylar guidance
- Intercondylar distance
- Hinge axis & centric relation
- Mandibular lateral movement
- Bennett shift
- Centric occlusion & rest position
Variable - Anterior guidance
- Occlusal plane
- Curve of spee
- Curve of Wilson
- Cusp heights
- Vertical overlapping
- Overjet & overbite
CONDYLAR GUIDANCE : Refers to the path that the Transcranial rotation axes of the
condyle travel during mandibular opening. This path may be measured in degree from the FH
plane.
During functional movements, its curvature has a great influence in occlusal contact
from centric relation to centric occlusion even in eccentric movements.
If the gleniod fossa is very deep, the condylar path will be very steep. Then during
protrusive movements, there will be no contact of posterior teeth (Christensen’s
phenomenon) and vice versa.
INTERCONDYLAR DISTANCE :-
It influences the carving of occlusal surfaces in regard to the direction and position of
grooves and cusp inclines. The greater the distance, the greater the tendency for grooves and
cusp inclines to be located distally on mandibular teeth and mesially on maxillary teeth. On
the balancing side of the arch this tendency will be inverted.
HINGE AXIS & CENTRIC RELATION :-
The horizontal rotation axis of the mandible, which passes through both the condyles
permits a limited hinge like movement and no translation.
In centric relation the mandibular condyles are simultaneously seated more superiorly
on the posterior slope of the articular disc properly interposed between them.
It is placed by the patients own healthy closing musculature which contracts evenly
on both side. It is the position prior to 1st tooth contact. Theoretically, the mandible in this
position with passively swing up & down in a hinge movement around an axis passing
through both condyles.
With the condyles being irregular in shape and their respective articular surface also
not being uniformly rounded the rotatary movement of the mandible in centric venation may
generate instantaneous axes of rotation, which may not be located inside the condyles.
Due to this fact, according to individual variation, the condyle may assume an
uppermost & rearmost, uppermost & midmost or uppermost and anterior position in the joint,

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when positioned in centric relation when the mandible is brought to the level of maximum
intercuspation, the bracing action of the muscles activates the contraction of the intermediate
median & posterior fibers of the temporal muscles to position the condyles in the uppermost
and rearmost, uppermost & midmost & uppermost and anterior position of the surface. In
addition, the subject contracts the digastric muscle to his/her mandible.
BENNETT MOVT & BENNETT ANGLE :-
The lateral shift of the mandible called Bennett movement is measured by the distance
that the condyle on the working side moves from W1 to W2. The opposing or balancing
condyle moves down, forward and inward and makes an angle with the median plane when
projected perpendicularly on the horizontal plane. This angle is called Bennett Angle. This
lateral movement may have immediate as well as progressive components.
On the working side, the rotating condyle may move laterally from W1 to W2 up to
approximately 3mm.
MAXIMUM INTERCUSPATION : Also called centric occlusion, habitual centric,
intercuspal position, acquired centric, tooth to tooth position convenience occlusion, power
centric.
It is the position in which opposing teeth are firmly contacting each other, it is directly
related to vertical dimension of occlusion. Maximum masticatory efficiency is observed when
the muscles are in an optimum length of contraction. It is about 1.5mm ahead of centric
relation.
The contacts occur on the cuspal inclines, depth of the fossa, marginal ridges. The
lingual cusps of the upper posterior and buccal cusps of the lower teeth are generally
considered supporting cusps since on their interface there is a great incidence of centric stops.
Generally, one should have only 3 simultaneous contact on the occlusal surface of a given
tooth.
2 on cusp tips and one on the depth of fossa. It is best to avoid centric stops on the
occlusal inclines, since they are capable of providing good stability.
REST POSITION/POSTURAL POSITION :-
This posture of the mandible maybe defined as a balance of a lower level of activity
between the elevator & depressor muscles of the mandible as well as viscoelastic properties
of the muscle, capable of maintaining the mandibular bone suspended at a curtains
interocclusal distance (1-3mm).
During this position, the fibers are at their optimal length and minimal firing level
from where they will able to start the elevation or depression of the lower jaw.
ANTERIOR GUIDANCE :-
Is determined by the relation of the upper and lower anterior teeth at a given vertical
dimension. It is actually the angle formed by incisal edge of lower anterior teeth and lingual
anatomy of upper anterior teeth.
PLANE OF OCCLUSION :-
Is an imaginary plane containing the incisal edges of the mandibular central incisor
and the tips of distobuccal cusps of 2nd mandibular molars.

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It determines the special orientation of the occlusal surface of the teeth in relation to
the base of the skull and maxillary bone.
CURVE OF SPEE :-
Introduced by Graf Von Spee, and is determined by the occlusal surfaces of the teeth
following the cusp tips of anterior mandibular teeth to the buccal cusp tips of posterior
mandibular teeth.
Greater the curvature, the higher the cusp will have to be inorder to produce efficient
mastication. Lesser the curvature, lower the height of cusps so that the interfering contacts
may be avoided
CURVE OF WILSON :-
Curve that contacts the buccal and lingual cusp tips of mandibular buccal teeth.
It results from an inward inclination of lower posterior teeth.
It help in 2 ways
- Teeth are aligned parallel to the direction of medial pterygoid for optimum
resistance to masticatory force.
- The elevated buccal cusps prevent food from going past the occlusal table.
- The curve change from 1st to 3rd molar and with the wear of the dentition. The
curve of Wilson in the mandibular 1st molar is concave in an unworn dentition but
becomes convex in a worn dentition.
Monson connected the curve of spee, or curvatures in the sagital plane with related
compensating curvatures in vertical planes and suggested that the mandibular arch adopted
itself to the curved segment of a sphere of 4 inch radius.
CUSP DIMENSIONS :-
In the occulsal scheme – 2 types of cusp are visualized –
Supporting (stamp, centric holding)
Guiding (trespassing, non supporting, shearing)
Centric holding cusps are facial cusps of mandible and palatal cusps of maxillary
posterior teeth. They occlude into central fossa and marginal ridge.
Guiding cusps are maxillary buccal and mandibular lingual. They contact and guide
the mandible during lateral excursion and shear food during mastication.
OVERJET AND OVERBITE :-
Greater the overjet, the shorter the cusp heights in order to avoid eccentric functional
movement interferences. In cases of long overjet, some pateints due to their deficient anterior
guidance have to use posterior teeth for eccentric guidance called MEDIAL GUIDANCE.
The lesserthe overbite, the shorter the posterior teeth cusp height should be to avoid
protrusive interferences.

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OCCLUSAL CONTACTS
Centric stops : Are the areas of contact that the supporting cusp makes with an opposing
teeth.
CUSP TO FOSSA OCCLUSION : (TOOTH TO TOOTH ARRANGEMENT)
The pointed mesiolingual cusp portion of the upper molar fit into the major fosse of
lower molar in centric occlusion. This is useful in chewing and stabilization.
The distolingual cusp of upper molar fit into the distal triangular fossa or marginal
ridge of the lower molar or into the mesial marginal ridge of the molar distal to their
namesake. The lingual cusps of the upper premolar fit into the triangular fossa of lower
premolar. Mesiobuccal cusps of lower molars into the distal fossa or marginal ridge bordering
it of the tooth above, mesial to its namesake. The distobuccal cusps of lower molars
approximate into the central fossa of their namesakes in the upper arch. The buccal cusp tips
of 2nd lower premolar into mesial fossa of upper 2nd premolar.
CUSP TO EMBRASURE (TOOTH TO 2 TEETH OCCLUSION) :-
It is found when a tooth has two opponents some cusp tips are actually apposed to
embrasures spaces, while their cusps are in partial contact with marginal and cusp ridge in
addition to straddling the embrasure space created by the ridge.
RIDGE & SULCUS APPOSITION :-
The triangular ridge of the buccal cusps of upper molar occlude with the buccal grove
with their sulcus in lower molars.
The triangular ridges of the distolugualcusps of lower 1st molar with the lingual grove
sulcus of maxillary 1st molar.
Oblique or transverse ridge of upper 1st molar with the sulcus on lower 1st molar
marked by distobccal, central and lingual developmental groove.
Hellman listed 138 points of occlusal contacts, which included 32 teeth.
There are 2 main groups of interocclusal contact :
Closure stoppers : Are found on the distal incline of upper posterior teeth and mesial
inclusive of lower posterior teeth.
Functions to
- Stop hinge closure of the mandible
- Offset forces exerted by equalizers.
- Contribute to anterior component of force on upper teeth.
- Oppose anterior component of force on lower teeth.
- Prevent hard contact on anterior teeth.
Equalizers :-
Are located on the mesial inclines of the upper posterior and distal inclines of lower
posterior.
Functions to –

15
- Offset the force exerted by closure stoppers
- Oppose anterior component of force on upper posteriors
- Contribute to anterior component of force in lower posterior
Interocclusal contact are classified into three :-
A CONTACTS : Shearing cusps of upper teeth occlude with stamp
cusp of lower
C CONTACTS : Stamp cusps of upper occludes with shearing cusps of
lower.
B CONTACTS : Stamp cusps of upper and stamp cusps of lower.
A + B - Produces stability
C + B - also stability
A + B + C - also stability
A + C - tooth movement or mandibular movement.
B - Tooth movement or mandibular movement
Centric Contacts : Are classified into posterior centric contacts and anterior centric contacts
posterior contacts. Consist of facial range and lingual range of contact.
Facial involves the mandibular facial cusp tips contacting the central fossa and mesial
marginal ridges of the opposing maxillary teeth. Lingual ones involve the maxillary lingual
cusp tips contacting the central fossa and distalmarginal ridge of opposing mandibular teeth.
Anterior have only 1 range of centric contacts
PODED CENTRIC CONTACTS:-
The contact occurring on inclines should be balanced by on equal contact on an
opposing incline to resolved the forces in an axial direction. It the contact occur on 2 inclines,
it is termed BIPODED CONTACTS, contact on 3 incline is termed TRIPODED
CONTACTS and those on 4 inclines QUADRAPODED CONTACTS.
OCCUSAL CONTACTS DURING VARIOUS MANDIBULAR POSITIONS AND
MOVEMENTS:-
BALANCED OCCLUSION (FULLY BALANCED, BILATERALLY BALANCED)
Has all teeth in contact in maximum intercuspation also and during eccentric
mandibular movements. Is ideal for restoration with complete dentures.
The forces generated are shared by all teeth and TMJ. It is seen in natural dentition
when there is advanced attrition.
MUTUALLY PROTECTED OCCLUSION :-
Here the posterior teeth protect the anterior teeth and vice versa. Posterior teeth
protect the anterior teeth in centric position. The centric stops on the posterior teeth also help
prevent excess loading transferred to the TMJ. The incisor protect the canine and posterior
teeth during protrusive movement and canine protect the incisors and posterior during lateral
movements.

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It is felt that the ideal occlusion for natural dentition and vertical dimension is
maintained by the posterior teeth.
D Amico found that canine guidance positioned the mandible into maximum
intercuspation and no teeth contacted till the final position. Mandibular eccentric movements
were guided by the canines except in protrusion, so the canine is a key element in occlusion.
Anatomical evidence to support the canine as a key element includes :-
- Good crown – root ratio
- Amount of hard, compact bone surrounding the tooth.
- Location far from TMJ.
- Canines has many receptors in PDL and it has been said that the canine controls
lateral pressure by directing vertical masticatory movements
MPO is contraindicated when masticatory cycles is horizontal and when PDL is
compromised. Lucia advocated that when anterior teeth are strong, MPO is used but when
anterior are missing balanced occlusion is to be used.
Dawson staled that when canines cannot be used, lateral movements have posterior
disclusion guided by anterior teeth on the working side instead of the canines alone, he called
this ANTERIOR GROUP FUNCTION.
SCHUYLER stated that when mandibular movement cannot be guided by anterior
teeth, all working side teeth should be used for guidance during lateral movements.
The term MPO was changed to organic occlusion by STALLARD & STUART.
In organic occlusion, centric relation and centric occlusion coincide. The posterior
teeth are in cusp to fossa relation. Each functional cusp contacts the occlusal fosse at 3 points
while anterior teeth disclude by 25. In protrusive movement, the maxillary incisors guide
the mandible and disocclude the posterior teeth. In lateral movements, the lingual surface of
the maxillary canine guides along the distal incline of mandibular canine and mesial ridge of
1st premolar facial cusp.
GROUP FUNCTION :-
Schuyler introduced the fundamental of this occlusion. It occurs when all facial ridges
of working side teeth contact the opposing dentition while the non working side do not
contact. Has a broad support and has been frequently observed in natural dentition.
CHARACTERISTICS :-
- Teeth should receive stress along the tooth long axis.
- Total stress should be distributed among the tooth segment in lateral movement.
- No interferences occur from closure into inter cuspal position.
- Keep proper interrocclusal clearance.
- Teeth contact in lateral movement without interferences.
Dawson described 5 concepts important for an ideal occlusion :-
1) Stable stops on all teeth when the condyls are in their superior posterior position
(CR)
2) An anterior guidance that is in harmony with the border movements of the
envelope of function.
3) Disclusion of all posterior teeth in protrusive movements.
4) Disclusion of all posterior teeth on the balancing side.
5) Non interference of all posterior teeth on the non working side with either the
lateral anterior guidance or border movements of the condyles.

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ANDREWS 6 KEYS OF OCCLUSION
Andrews in 1970’s put forward the 6 keys to normal occlusion after studying 120
models of patients with ideal occlusion. They have a special value to the orthodontist because
- They have a complete set of indicators of optimal occlusions.
- They can be judged from tangible land marks.
- They can be judged from the facial and occlusal surfaces of the crown, reducing
the need for a lingual view or for articulating paper to confirm occlusal
interfacing.
ANDREWS PLANE :- The surface or plane on which the mid transverse plane of every
crown in an arch will fall when the teeth are optimally positioned. If the plane is concave or
convex, technically it is a surface, but in all instance it will referred as ANDREW’S PLANE.
CLINICAL CROWN : Amount of crown that can be seen intraorally or with a study cast.
Orbans definition – clinical crown as Anatomical crown height minus 1.8mm. In young
patients, or those with hypertrophied or receding gingiva the clinical crown height can be
found by measuring the distance from the incisal edge or cusp tip of the crown to CEJ and
then subtracting 1.8 mm.
CROWN ANGULATION :- The angle formed by the facial axis of the clinical crown
(FACC) and a line perpendicular to the occlusal plane.
Considered position, when the occlusal portion of the FACC in measured mesial to
the gingival portion, negative when distal.
CROWN INCLINATION : The angle between a line perpendicular to the occlusal plane
and a line that is parallel and tangent to the FACC at its midpoint.
Considered positive if the occulsal portion of the crown, tangent line or FACC is
facial to its gingival portion, negative if lingual.
FACIAL AXIS POINT (FA point) :-
The point on the facial axis that separates the gingival half of the clinical crown from
the occlusal half, was earlier called long axis point.
Key I : INTERARCH RELATIONSHIPS :-
The mesiobuccal cusp of the permanent maxillary 1st molar occludes in the groove
between the mesial and middle buccal cusps of the permanent mandibular 1st molar.
The distal marginal ridge of the maxillary 1st molar occludes with the mesial marginal
ridge of the mandibular 2nd molar.
The mesiobuccal cusp of the maxillary 1st molar occludes in the central fossa of the
mandibular 1st molar.
- The buccal cusps of the maxillary premolars have a cusp embrasure relationship
with the mandibular premolar.
- The lingual cusps of maxillary premolar have a cusp-fossa relationship with the
mandibular premolar.
- The maxillary canine has a cusp embrasure relationship with the mandibular
canine and 1st premolar.
- The tip of its cusp is slightly mesial to the embrasure.

18
- The maxillary incisors overlap the mandibular incisors and the midlines of the
arches match.
II CROWN ANGULATION :
The line that passes along the long axis of the crown through the most prominent part
in the center of the labial or buccal surface. This is called long axis of the clinical crown.
For the occlusion to be considered normal, the gingival part of the long axis of the
crown must be distal to the occlusal part of the line.
III CROWN INCLINATION :-
Most maxillary incisors have a positive inclination, mandibular incisors have a
slightly negative inclination.
The max centrals have more positive inclination than the lateral.
The canine and premolar are negative and quite similar. The inclination of the
maxillary 1st and 2nd molars are also similar and negative, but slightly more negative, than
those of canines and premolars. The molars are more negative because they are measured
from the groove instead of from the prominent facial ridge from which the canines and
premolars are measured.
The inclinations of the mandibular crowns are progressively more negative from the
incisors through the 2nd molars.
IV ABSENCE OF ROTATION :
Rotated posteriors teeth occupy more space in the dental arch while rotated incisor
occupy less space in the arch.
V TIGHT CONTACTS :-
Contact points should abut unless a discrepancy exists in the mesio distal crown
diameter.
VI CURVE OF SPEE :-
The depth of the curve of spee ranges from a flat plane to a rightly concave surface.
An excursive curve of spee restricts the amount of space available for the upper teeth,
which must then move toward the mesial and distal thus preventing correct intercuspation.
A normal occlusion has a flat occlusal plane. According to Andrews the mandibular
curve of spee should not be deeper than 1.5 mm.
A reverse curve of spee create excessive space in the upper jaw, which prevents
development of a normal occlusion.
VII BOLTON’S RATIO :-

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FUNCTIONAL OCCLUSION
It is defined as the arrangement of teeth, which will provide the highest efficiency
during all excursive movements of the mandible which are necessary during function.
In recent years, orthodontists have voiced more and more interest in occlusion and
functional occlusion.
The stability of a treated orthodontic case would atleast partially rest in functional
dynamics of occlusion. The treatment must definitely help him and not harm him. Roth had
assumed that he could equilibrate every ortho case after tooth positions had settled. But the
case had to be atleast close to centric relation before equilibrations was done. Correct
occlusal equilibration is very time consuming. And also equilibration had to be done only
when growth had been completed.
TREATMENT OBJECTIVES :
- Pleasing facial esthetics evaluated by soft tissue and skeletal measurements
cephalometrically.
- Molar relation and tooth alignment evaluated by Angles description of anatomical
occlusion.
- Functional occlusion, evaluated gnathlogically on an articulator.
- Stability of post treatment tooth positions and alignment.
- Comfort, efficiency and longevity of the dentition, supporting structues and TMJ.
Ideally, when the jaw is closed from centric relation position to maximum closure the
teeth should mesh and should not cause the jaw to be pulled forward down or lateral side. Nor
should the teeth interfere with the full extent of movement.
Four areas of concern are.
- Defining the ideal relationship of the condyles in fossa.
- Degree of accuracy necessary to record the full extent of jaw movement.
- The type of centric contact and type of excursive occlusal scheme.
- Type and accuracy of the instrumentation to be used.
First of all, you must know your treatment objective:-
Is it supposed to be centric relation coinciding with centric occlusion or is it just alleviate
pain by alteration of occlusion?
CENTRIC RELATION has represent an idealized treatment goal. Condyles cannot be
retruded from this position without moving inferiorly in most instances. Centric relation is
not found with condyle appearing back against the tympanic plates. It is not a strained
position. Electromyography studies indicate that at centric relation, the condyles are seated in
the fossa against the superior – posterior slope of the eminence. Tooth interferences prevent
the muscles from sealing the condyles property.
REARMOST POSITION is often been debated because cases with damaged TMJ ligaments
where excess mobility of condyles is seen it is virtually impossible to push the mandible
distally without causing further inferior positioning or subluxation of the condyles.
RECOGNIGING OCCLUSAL DISHARMONY :-
It becomes important to know the signs and symptoms of occlusal interference.

20
- Occlusal wear
- Excessive tooth mobility
- TMJ sounds
- Limitations of opening movement
- Myofascial pain
- Contracture of mandibular musculature, making manipulation difficult or
impossible.
- Some types of tongue thrust swallow.
If signs and symptoms are present, put him on a splint and see if symptoms can be
eliminated or alleviated and what changes occur in mandibular position before placing
orthodontic appliances. Even a little bit of clicking or wear is considered abnormal.
We are treating kids with exceptionally high tolerance level and adaptive capacities.
As he grows older, the tolerance decrease.
The patients do not adapt to occlusal interferences, they tolerate them. If the adaptive
capacity have been exceeded, the patient become symptomatic.
There are three sets of patients :-
- Those with symptomatology
- Those with either psychologically or physically predisposed to developing a
problem.
- Those that are neither symptomatic nor predisposed to develop symptoms.
People with psychological stresses either vent it outwardly or inwardly. Those who
vent it inwardly, the target places are gut, teeth and jaws.
Occlusal interferences tend to make teeth and jaws a focus for venting psychological
stresses. When the teeth are stressed, the weakest link in the chain breaks down.
If the patient is prone to periodontal diseases, in the presence of plaque, PDL breaks
down. If PDL is healthy and hygiene is good, occlusal wear maytake place. If the TMJ is
weak, there may be TMJ dysfunction or diseases.
In some instances, when the clinical symptomatology is of a minor nature and the
patient is in a delicate balance accommodating to his existing occlusion, barely through. He is
actually in a precipice, any traumatic injury, sudden stretch of tense mandibular musculature
or increase psychological stress or any minor change in occlusion will make him
symptomatic and the degradation begins.
EXAMINATION :-
On initial examination, the orthodontist should manipulate the mandible into clinical
centric relation.
Place the left thumb and forefinger over the patients upper teeth. The right thumb
should be placed on the superior aspect of pogonion applying downward pressure and the
right fore finger and 2nd finger placed under the gonial angles applying upward pressure.
The pressure is being applied downward on the chin, keeps the patient from closing
and his attempt to close will cause his own musculature to seat the condyles superiorly, which
is what is desired.
The patient is instructed to allow the jaw to move in the direction the pressure in
being applied. He is allowed to close until his lower teeth barely touch your fingers. Once the
condyles are seated superiorly, the patient is instructed, as the dentists fingers are removed,
keep the jaw where it is and slowly hinge it closed on this arc until you just begin to feel
something touch and then stop and not let the jaw go where the teeth fit. Check for

21
discrepancies. If you find that the discrepancy is very large then mount on a simple
articulator.
TMJ is palpated for popping/grating sound or tenderness.
Wear facts on the teeth are looked for, check the patients ability to execute left and
right lateral excursion and protrusive movements.
If the patient cannot execute gliding movements on anterior teeth in all excursions
there are post interferences or incorrect anterior coupling.
Also check for maximum opening – 45-50 mm indicates a state of contracture of
mandibular musculature.
The neuromuscular positoning of the mandible to accommodate occlusal
discrepancies will hide the true discrepancies from us.
A true/stable centric relation can almost be never captured on the 1st clinical attempt.
RE POSITIONING SPLINT :-
The two great causes of failure of occlusal treatment are
- Failure to stabiles and then capture true centric relation
- Failure to alter occlusion to hold centric and still clear on movement.
PURPOSE OF A SPLINT :-
- To find true centric
- To test the patient’s response to changes in occlusion
- To see if mandibular centric position is stabilized.
EUGENE DYER popularized the craniomandibular orthopedic appliance or the splint.
Is used when the patient is symptomatic or mandible is difficult to manipulate. It serves
the following function :
- Alleviation of pain dysfunction symptoms
- Diagnosis of true maxillo mandibular relationship.
- Means of relaxing the mandibular musculature
- Resolving inflammatory change within the joint capsule.
- Allows remodeling of the joint to occur.
Most of the patients will reposition from 1st captured centric. Greater the pain or
discomfort, the greater the amount of repositioning. Those that cannot be stabilized are those
with radiographic signs of degenerative or bony recontouring processes going on.
CAPTURING AND STABILIZING TRUE CENTRIC :-
Centric is a stable superior clinical limit position of the condyles against the articular
disc that can be captured clinically and reproduced time and again.
Once muscles are stabilized or relaxed, any good centric registration technique will
yield identical and verifiable centric positions of the mandible.
The objective of making repositioning splint is to seat the condyles in the most
superior position possible on every visit and to adjust the occlusal surface to achieve
maximum intercuspation at this position of the mandible.
Also an anterior guide ramp is created to act as anterior guidance to disocclude the
posterior teeth during movement out of centric. The splint is constructed is such way that at
becomes a removable appliance with a mutually protected occlusal scheme.

22
The repositioner should be adjusted as soon as a change in mandibular position
becomes evident. It is done by relining the occlusal surface of the splint with a self curing
acrylic resin.
The mandibular positional changes during splint therapy is due to
- Changes due to relaxation of the musculature.
- Changes due to the elimination of intra capsular inflammatory fluid.
- Change due to remodeling or recontouring of the bony parts of the joints.
The splint therapy must be continued until there has been no change is mandibular
positioning in CR for atleast 3 months. In more difficult cases, when there is some
radiological evidence of recontouring of bony parts, 6 months stabilization is required. It is
usually better to splint for 3 months before starting a symptomatic case.
CONSTRUCTION :
- Impression of the maxillary arch should be accurate. It must be poured
immediately if alginate is used. It is made of accurate stone – MOUNTING
STONE made by whip mix corporation with a setting expansion of 0.08%.
- The base is constructed from 0.080 omnivac or BIOCRYL II material on a
BIOSTAR at atm pressure.
- The base material should snap tightly with a minimum of material over the labial
and buccal surface of the teeth.
- Excess material is cut off from the soft palate.
- The base is placed in the month and the mandible is manipulated into centric. The
thickness of the base should be very less posteriorly where 1st centric contacts
occur.
- Trimming as done with a buffallow carbide acrylic bur in a slow-speed handpiece
- After this, the splint is ready for occlusal lining.
- A fairly thin mix of acrylic should be prepared, and is placed on the occlusal
surfaces. You also build an anterior guide ramp from cuspid to cuspid
- Dry the acrylic a little with air syringe and place it carefully in the month, lean the
chair and manipulate the patients mandible to centric such that you get light prints
of the cusps. Allow it to set.
- After the malerial has set, a sharp pencil is used to outline the entire buccal and
labial impressions of the lower cusps in the acrylic.
- Gross trimming of the occlusal lining and anterior ramp is done.
- Excess is cut away leaving the pencil mark at the very tips of the cusps.
- Anterior ramp is cut approximately 450 from canine to canine.
- The splint is polished with pumice.
- Splint is now put into the month and equilibrated in centric using ACUFILM.
- A mutually protected occlusal scheme is got.
- The patient is told that be might have some discomfort or even a headache on the
1st day. But at the middle of 2nd morning, things should be alright.
- By 2nd day the bite may leek different and so called back to clinic for adjustment
before pain sets in.
If there is extreme pain initially, and is not feasible to manipulate the mandible, a flat
plane splint is constructed, but instead of building a guide ramp, get equal contact of all teeth
against the acrylic. The patient wears it full time for several days and then occlusal reline is
done.

23
If the patient is in severe pain or spasm, valium with hot packs are given. Splint is to be
worn will the time except for cleaning.
- If there is posterior capsulitis or large closing click, leaving the patients only on
anterior support may damage the posterior area of the capsule and may result in
both pain and more damage
- Drugs not be given.
FINISHING TO GNATHOLOGICAL PRINCIPLES
Gnathological Objectives :-
1) To obtain a stable centic relation of the mandible and have the teeth intercusp
maximally at this mandibular position. There should be no contact of anterior
teeth in centric closure (0.0005” clearance).
2) Harmonious glide path of anterior teeth, to separate the posterior teeth
immediately.
3) Mutually protected occlusal scheme is established.
Ideally centric relations coincide with centric occlusion. But it occurs in less than 1%
of cases so, possibly, we can treat the case close enough to centric that there is no discernible
discrepaney between centric relation and habitual centric clinically. Also treat it close to
centric such that if equilibrations is required it can be done.
IDEAL TOOTH POSITIONING :-
Prior to all treatment, the patient must be monitored in centric relation. If symptoms
of TMJ problems are evident or difficult to manipulate, put him on repositioning splint for 3
months. At every appointment, the patient should be checked in centric, so that the patient
learns where his centric, so that the patient learns where his mandible should be when his
teeth fit together.
Centrically related occlusion and mutually protected occlusion are dependent on
- Proper individual tooth positioning
- Knowing when the mandible is in centric and when it is not.
- Coordination of arch form and width.
- Control of vertical dimension
- Anterior – posterior correction between maxilla and mandible.
- Clinical awareness of excursive interferences.
ARCH FORM :- Is a modified centenary curve consisting of 5 separate radii. The widest
part of the lower arch is at the mesiobuccal cusps of lower 1st molar and 1st premolar. In the
maxillary arch, it is the mesiobuccal cusp of upper 1st molar.
- No more than 1mm of attached gingival is shown on full smile.
- Tips of upper incisor should be 2-2.5mm below the lip embrasure of the upper and
lower lips when lips are closed with no lip strain.
- Approximately 2.5mm overjet, overbite with 0.0005” clearance of incisors when
in centric.
- A level or nearly level occlusal plane at the end of appliance therapy that would
return to 1-1.5mm curve of spee at its deepest point after appliance removal and
settling of occlusion.

24
- Lower incisor aligned contact point to contact point with roots in the same plane
when observed from occlusal, the mesioaxial inclination should be 20.
- Lower cuspid crown angulated mesially 50, incisal tip 1mm higher than central
incisor. Lower cuspid should have a slightly exaggerated mesial rotation in
extraction case.
- Lower bicuspids should be upright 10 from their normal mesial inclination and
should have a slight distal rotation (more in extraction)
- Lower molar should be uprighted 10 from their normal 20 mesial inclination and
slight distal rotation.
- Lower buccal segment should have progressive torque close to Andrew’s
measurements for establishment of curve of Wilson, no rotation or spaces.
- Upper 1st and 2nd molar should have sufficient distal rotation, mesioaxial
inclination and buccal root torque described by Andrews – 140 torque and 00
mesial inclination.
- Upper premolars uprighted to 00 from their normal 20 mesial inclination with no
rotation, except for some distal rotation in an extraction case.
- Upper cuspid should have proper contact points, 11-130 mesial crown tip, mesial
rotation of 40 on an extraction case.
- Upper lateral and central should have no more than 0.5mm height difference, with
90 and 50 mesioaxial inclination
- No rotations or spaces in upper arch and buccal segments from the cuspids distally
should have 140 non progressive buccal root torque.
- It is better if the desired treatment is built into the appliance.
OVER CORRECTION :-
Over correction required because
- Tooth will move after appliance removal
- Curve of spee will flatten
- Teeth that are slightly tipped distally in the buccal segment will tend to settle
better than those already mesially inclined.
- Teeth in the buccal segments settle, they will tip mesially and rotate mesially.
- As band space close, there is corresponding loss of torque in the anterior teeth.
- Teeth adjacent to extraction site will rotate and tip towards extraction space
- Maxillary lingual cusp will migrate downward till it finds on occlusal stop against
opposing teeth.
OVER CORRECTION is build for all areas except for buccolingual torque of lower buccal
segments as it acts as a template for the maxillary teeth to occlude.
TREATMENT PRIORITIES :-
- Correction of cross bites
- Correction of jaw relationship (orthopedic appliances)
- Elimination of crowding
- Establishment of space for severely malposed teeth.
- Space consolidation of the lower arch
- Leveling of curve of spee
- Finishing lower arch
- Establishment of desired molar and buccal segment relationship

25
- Consolidation of maxillary space; retraction and intrusion of maxillary anteriors
- Artistic positioning and torque of maxillary anteriors
- Overcorrection
- Final detailing
It is always better to stabilize the lower arch within a year.
DETAILING OF TOOTH POSITIONS IN TREATMENTS :-
- Each tooth must be considered individually
- Bracket placement is utmost important to achieve good occlusal intercuspation
- The 12 year molar are most commonly involved in occlusal interference it is
generally better to band them
- Artistically tipped incisors occupy more space.
CONTROL OF VERTICAL DIMENSION AND MOLAR FULCRUM :-
- Avoid extrusion of posteriors toe avoid molar fulcrum
- The molar fulcrum causes anterior open bite through premolar and develop tongue
thrust swallow.
- Sometimes there may not be open bite but clicking of TMJ and stiffening of
muscles
- Use of repositioning splint is advocated
AFTER CENTRIC IS OBTAINED :-
Look for - Torque of upper incisors
- Artistic tip of upper incisors and cuspid
- Overjet and overbite
- Flatness of curve of spee
- 2nd molar position
- Anterior group function posterior clearance, cuspid guidance
and balancing interferences.
At the end of appliance therapy, occlusion should almost resemble bilaterally
balanced occlusion because of leveled curve of spee, overcorrection of overbite. Anterior
guidance is not to be kept adequate.
GNATHOLOGICAL TOOTH POSITIONER :-
Purpose : Move the occlusion closer to centric relation than it was at the time of debanding
- Also aid in better anterior guidance and posterior disclusion upon mandibular
movement
- Positioner is later used to maintain centric during most of retention period
- Used to correct minor rotation, buccolingual or labiolingual adjustments and
control of vertical settling.

26
REQUIREMENTS :-
The case should have been treated close enough to centric and mutually protected
occlusal scheme should have been got.
Is made on anatomical articulator, Denar mark II articulator using the material
OROLASTIC II
The positioner is to be worn full time for 2-3d days. After 5-7 days, night wear and 2
hours in the day.
When the positioner is placed in the patient month, the patient can place the positioner
on the upper arch and the mandible can be placed clinically into centric relation and hinged
into the positioner. One can literally see the soft tissues blanch around the teeth that are the
centric deflectors indicating that these teeth are going to be moved by the appliance.

27
OCCLUSAL EQUILIBRATION
The term occlusal equilibration refers to the correction of stressful occlusal contacts
through selective grinding. It involves selective reshaping of the tooth surface that interfere
with normal jaw function.
ADVANTAGES :-
It never harms the patient, allows about for free movement of the mandible to move
wherever, consciously or unconsciously, proper equilibration is stable.
PROCEDURES :-
Can be divided into four
- Reduction of all contacting tooth surface that interface with the terminal hinge
axis closure.
- Selective reduction in lateral excursion
- Elimination of all posterior tooth structure that interferes with protrusive
excursions
- Harmonization of anterior guidance
COUNSELING BEFORE EQUILIBRATION :-
The patient be to told the need for the procedure. Never should the equilibration be
started unless both the clinician and the patient are committed to complete.
LOCATING THE INTERFERENCES :-
Improper manipulation of the mandible is responsible for most failures in
equilibrations. For equilibrations to be successful, the condyle disc assemblies must be free to
seat in their most superior position without any forced displacement when teeth intercuspate.
As the jaw closes and tooth contacts get closer, some resistance may be felt. Just
delay for a moment and then start to close again, continue a slow opening closing movement
until the 1st tooth contact occurs, which is the 1st interference.
ELIMINATING INTERFERENCES IN CENTRIC RELATION
2 Types :
Interferences in the arc of closure :-
As the condyles rotate on their terminal hinge axis each lower tooth follow an arc of
closure. They should intercuspate without any deviation. Most deviations from the arc of
closure require the condyle to move forward. Primary interferences that deviate the condyle
forward produces an anterior slide.
Basic rule to correct anterior slide is MUDL- Mesial incline of the upper and distal
incline of the lower.
Interference in the line of closure :

28
Refer to the primary interferences that causes the mandible to deviate left or right
from 1st part of contact to the most closed position.
If interfering incline causes the mandible to deviate off the line of closure toward the
cheek, grind the buccal incline of upper and lingual incline of the lower or both inclines
(BULL).
If interfering incline causes the mandible to deviate off the line of closure toward the
tongue, grind the lingual incline of the upper or buccal incline of lower (LUBL). This can be
applied to any cusp and they are valid if the teeth are in crossbite relationship.
Many interference produce deviation of both the arc of closure and line of closure at
the same time. In such a case, upper incline are always adjusted on the inclines that face the
same direction as the slide. Lower teeth are adjusted by grinding of inclines that face the
opposite direction from the path of slide.
The vertical dimensions of occlusion after equilibration at centric relations should
remain the same as it is in acquired centric occlusion before adjustment.
Tilted teeth or wide cusp tips can be adjusted to improve stability as well as eliminate
interferences. If the mark on upper tooth is buccal to central fossa, the lower tooth is ground
to move the cusp lingually if the shaping can be accomplished without shortening of cusp tip
out of centric contact. Grinding of upper teeth only may mutiliate upper cusps unnecessarily.
If the mark on the upper tooth is lingual to its contact fossa and stability could be
improved, if the lower cusp tips is moved toward the buccal, the lower cusp tip is reshaped by
grinding its lingual inclines to move the contact buccally. This should not be done if it would
require shortening of the cusp out of centric contact. To grind the upper tooth only may
mutiliate the lingual cusp unnecessarily.
It is wise to give first priority to the elimination of all interference to centric relation
closure.
Reasons :-
- By adjusting cusp interference first you have the option of improving cusp tip
position. Most cusp tips are wide enough to permit narrowing toward a more
favourable central groove relationship.
- When cusp tip position is given the first priority, occlusal grinding is more evenly
distributed to both arches. Cusp tip position is usually improved by narrowing the
cusp on 1 arch.
Excessive interferences are then corrected by grinding of the fossae walls of opposing
arch. After gross adjustments are made in this sequence, fine contouring can be selectively
achieved on either arch.
If cusp tip contours and position are improved first in centric relation, centric
interference can be eliminated with speed and simplicity.
Though lateral excessive interference removal is an effective way to eliminate
interference it does not always produce optimum stability.
LATERAL EXCURSION INTERFERENCES :-
When lateral excursions are being equilibrated the mandible must be guided with firm
upward pressure to ensure that all interferences are recorded and eliminated through the
uppermost range of motion. If the patient is allowed to mark lateral interferences by unguided
excursions, there will be a tendency to slide anterolaterally to lateral border path. Guiding the
mandible with firm pressure during excursion will routinely pick up most interferences that
are missed with unguided movement.

29
ELIMINATING LATERAL INTERFERENCES :-
Are grouped into two :
- Working side interferences
- Balancing side
Balancing side interference can be adjusted quickly because the goal here is to
eliminate all contact on inclines as soon as the lower teeth move out of centric relation and
start toward the tongue. It is done first. The upper inclines of the upper and lingual inclines of
the lower are ground off. This is applicable to all situation including crossbites.
As the working inclines are corrected, previously reduced balancing inclines may
come back into interference and require further reduction. You will need to work with both
balancing and working inclines together.
WORKING SIDE INTERFERENCE :- It is necessary to determine the type of occlusion
that will best suit the particular patient.
GROUP FUNCTION :- Working side inclines are adjusted to precisely harmonize with both
condylar movements and anterior guidance. In group function the lower posterior cusp tips
and lower working side incisal edges maintain continuous contact from centric relation out
toward cheek. As the mandible swings laterally the length of the stroke contract is
progressive from molar forward. This means the 2nd molar disengages first, the cuspid last.
Posterior disclusion or mutually protected occlusal scheme is the best because of it effect on
the elevator muscles. At the moment of posterior disclusion most of the elevator muscle
contraction is shut off, reducing the load on both anterior teeth and the joints.
The rule of equilibrating working side contacts LUBL – lingual of upper, buccal of
lower cusps
PROTRUSIVE INTERFERENCES :-
All posterior contacts should be eliminated in protrusion. Here, the distal inclines of
the upper and mesial inclines of lower are ground away. In grinding away protrusion
interference centric stop should be marked with a different colored ribbon so that they will
not be inadvertently ground. The jaw should be positioned in centric relation and the patient
is asked to slide forward & back repeatedly.
Posterior disclusion in protrusion is accomplished by both the anterior guidance and
downward movement of the protruding condyles. With steep anterior guidance the correction
for protrusion interference is usually minimal. Flat anterior guidance rely more on condyles
for disclusion. When the arch relationship does not permit the anterior teeth to disclude the
posterior teeth, the farthest forward tooth on each side should serve to disocclude the rest of
posterior teeth in protrusion.
EQUILIBRATING HYPERMOBILE TEETH :-
Loose teeth that interfere can easily move to permit even marking with stable teeth.
Marks on then may be less noticeable than stable teeth. Tooth should be held in place with
the finger when marked.

30
Candidate with emotional problem may or may not be indicated for equilibration.
Only if all symptoms are resolved by the occlusal splints and the patient has a full
understanding of the need for occlusal correction, should direct equilibration be attempted.
IN ORTHODONTIC PATIENTS :-
Equilibration should not be used to take the place of correct tooth positioning.
During Treatment :-
It is permissible to change the shape of cusp, fossae or inclines during treatment, if
such changes will benefit stability after the tooth is moved. Non functioning inclines
particularly can be reshaped at any time during treatment. Visualizing the final position of
any tooth in question can help to determine what changes in shape would be beneficial.
During Retention :-
When bands are removed and a removable retainer is inserted, gross occlusal
correction should be initiated. If the occlusion can be corrected in position of retention,
stabilization of the teeth in that position will be enhanced.
When the tooth to tooth relationships is correct as the orthodontist believes it can be,
the occlusion should be refined.
EFFICIENCY IN EQUILIBRATION :-
It would be rare to finalize an occlusion to stability in appointment because stressed
teeth have a tendency to move as excessive occlusal forces are reduced.
- Equilibration is done in a dry mouth. Wet teeth prevent the ribbon from marking
adequately.
- It is better to use vacuum evacuation and stream of air.
- Drying with cotton roll leaves a thin film that reduces the effectiveness of marking
ribbon.
- Use a 12 sided football shaped silver carbide bur with a moderate speed
handpieces.
- RIBBONS : Very this films impregnated with different colors of ink are used.
- ACUFILM : The thinness of this film prevents it from smudging around the side
of cusp and permits to mark only surfaces that contact.
- Use a miller ribbon holder.
- Marking paper is usually not the best as the ink rubs off.
- Thin sheet of dark colored wax are placed on the occlusal surfaces of teeth in 1
arch. The opposite teeth are then tapped gently into the wax until it perforates.
This perforation is marked with pencil and reduced as usual. This method is
excellent for finding interferences on sharp line angle that are often difficult to
pick up by other methods.
- Other methods use of paints, sprays

31
OCCLUSAL DISORDERS
Parafunctional movements of the mandible may be described as sustained activities
that occur beyond the normal functions of mastication, swallowing and speech.
FORMS OF PARAFUNCTIONAL ACTIVITIES :-
Bruxism, clenching, Nail biting, pencil chewing. Typically, parafunction is
manifested by long periods of increased muscle contraction and hyper activity. Over a
protracted period, this phenomenon may result in excessive or retrograde wear, widening of
the periodontal ligament, mobility, migration or fracture of teeth.
Muscle dysfunctions such as myospasms, myositis, myalgia and referred pain may
also be seen.
2 most common forms of these activities are BRUXISM and CLENCHING.
BRUXISM : Is the sustained grinding, rubbing together, or gnashing of teeth with greater
than normal chewing force. This may be diurnal, nocturnal or both. Although bruxists is
initiated on a subconsious level, nocturnal bruxism is prudentially more harmful because the
patient is not aware of it while sleeping. Because of this it is difficult to detect and should be
expected in any patient who exhibits abnormal tooth wear or pain.
The etiology of bruxism is also often unclear and may be related to malocclusion,
neuromuscular disturbances, response to emotional stress or a combination.
Altered mastication has been observed in such patient and may be due to the fact that
the chewing pattern avoid interfering occlsual contacts. There may also be a neuromuscular
attempt to rub out the interfering cusp. The fulcrum effect of rubbing on posterior
interferences will create a protrusive or laterotrusive movement that cause overloading of the
anterior teeth, with resultant excessive anterior wear. In certain malocclusion the
neuromuscular system exerts fine control during chewing to avoid particular occlusal
interferences. As the degree of muscle activity necessary to avoid the interferences become
greater, an increase in muscle tone may result with subsequent pain in the hyperactive
musculature, which in turn can lead to restricted movement.
If uncontrolled, it may result in occlusal wear, hypermobility of teeth, adaptive
changes in TMJ, flattening of condyles and gradual loss of convexity of eminence,
enlargement of musculature.
Split teeth or fractured filling, screeching or grating sound
Treatment :- the behavioral modality is initiated by the dentist through explanation and
awarness of patients of the habit. Behavioral therapies such as EMG biofeedback may be
prescribed.
If musculoskeletal pain and stiffness are associated with bruxism, a brief course of
physical therapy is appropriate. Medications for few days aimed at altering sleep or reducing
anxiety such as diazepam. Low doses of trycyclic antidepressant are given to inhibit the
amount of REM sleep.
Maxillary stabilization appliance is most effective.
The patient is asked to wear it at night. The appliance is readjusted in 2-4 week and
thereafter over longer intervals. In follow up visits, the occlusal surface of the appliance
should be observed for bruxofacets in the hard acrylic resin. Bruxofacets in the appliance
should be burnished away with a smooth pumice impregnated rubber wheel. Careful
balancing of occlusion on the nightguard should be completed before dismissal of the patient.

32
Clenching : clenching is defined as forceful clamping together of jaws in static relationship.
The pressure thus created can be maintained over a considerable time with short periods of
relaxation is between. The etiology is generally associated with stress, anger, physical
exertion or intense concentrations on a given task rather than on occlusal disorder.
As opposed to bruxism clenching does not readily result in damage to the teeth
because the concentration of pressure is directed more or less through the long axis of the
posterior teeth without the involvement of detrimental lateral forces. However, the increased
load may result in damages to the periodontium, TMJ, and muscles of mastication. Typically
the elevators will become overdeveloped.

33
BEGG ATTRITIONAL OCCLUSION CONCEPT
There is nothing more important for a dental or orthodontic student to learn than the
normal attritional development of man’s dentition. Only then, can he or she understand the
true causes of most dental and orthodontic problems, and take appropriate remedial action.
Dr. P.R. Begg after studying the skull of primitive man and Australian aboriginals
rejected the concept of the textbook normal occlusion (Fig 3) as a fallacy. He refused the
precept of normal textbook occlusion, which consists of a static non-changing condition,
which was thought to be normal physiologically, functionally and anatomically in man.
Begg advocated the Stone Age mans attritional occlusion represented the true
occlusion for man-not a pathological condition was basis of orthodontics, because it is
anatomical and functionally correct occlusion. Civilized man’s unworn dentition with all its
related problems is abnormal.
CORRECT OCCLUSION
Correct occlusion according to Dr. Begg and his co-workers was not a static condition
as is considered in textbook normal occlusion where there is correct interdigitation of the
cusp to fossa interlocking, no attrition and tight proximal contacts.
According to their concept in correct occlusion the position relationships of the
individual teeth to each other in the same dental arch, the occlusal, relationships of the teeth
of one dental arch to those of the opposite arch and the relationships of the teeth to the jaws
change continually throughout life. Therefore the only constant incorrect occlusion is
continually changing occlusion!!!
FACTORS IN CORRECT OCCLUSION :
1. Tooth migration :
Tooth migration is considered to be a factor that is indispensable for bringing about
the continually changing position of the teeth in the jawbones. It is accepted that teeth
continually move throughout life in two directions simultaneously horizontal (mesial
migration) and vertical (continual eruption occlusally) (Fig – 9).
According to Dr. Beggs, mesial and occlusal migration is a normal and vitally
necessary physiologic process, which is related to and is part of the process of continual tooth
migration.
2. Changing anatomy of teeth :
In very few animals does the anatomy of the teeth remain completely unchanged
throughout life. Among mammals with perhaps the exception of some of the carniovores and
insectivores the anatomic forms of the teeth begin to change soon after eruption because of
wear, or attrition. This attrition chiefly takes place occlusally, incisally and proximally.
Attrition is considered to play an important role in the evolution of the anatomy of the
teeth, there growth processes, function and characteristics, which confer freedom from
disease of the teeth and their supporting tissues.
In fact absence of attritional occlusion is thought to cause malocclusion. Absence of
attrition also cause periodontal disease and dental caries and thus reduces the functional
efficiency of mans dentition, but since modern mans food are soft and papery, he does not

34
suffer through the masticatory shortcomings of his dentition. Attrition in the Stone Age man
is attributed to the hard and coarse diet that he had.
Thus anatomically correct occlusion is developed and maintained by these factors.
1. Tooth Movement - Continual mesial and continual vertical
eruption
2. Anatomy of the teeth - The changing anatomy, dependent on
tooth attrition.
ANATOMICALLY CORRECT ATTRITIONAL OCCLUSION
Anatomically correct occlusion is thought to be practically non-existent in civilized
man because, the basic factor’s that make this occlusion possible are absent. The Australian
aboriginals teeth were considerably larger than those of other living races. Anatomically
correct occlusion is thought to develop only when there is sufficient attrition of the teeth for
them to assume correct occlusal relationships. Stone Age man’s teeth have occlusal and
proximal attrition and this may be so marked as to even expose the dentin. However, caries
was virtually non-existent in Stone Age man’s dentition. In contrast civilized mans due to the
soft and refined diet do not have so much of tooth attrition. This result in the incisal, proximal
and axial relations of his teeth remain almost static throughout life because the unworn cusps
are locked in an anatomically incorrect occlusion. More over, this lack of attrition is believed
to prevent the jaws from assuming normal relations to each other, especially in the vertical.
Civilized mans upper and lower jaws are forced further apart as his teeth continually erupt
without being continually reduced in vertical length by occlusal and incisal attrition.
Process of attritional occlusion in Stone Age man :
The reason for the attrition of Stone Age mans teeth was the hard, coarse fibrous and
gritty food that he ate.
Attritional occlusion in the deciduous dentition :
Stone Age man deciduous incisors erupt into a normal incisors overbite, however
attritional occlusion will immediately commence reducing the size of each tooth occlusally,
incisally and proximally. The end result will be the elimination of the overbite into an edge-
to-edge relation of the anteriors and flattering of the occlusal surface of the posterior due to
attrition even to the extent of exposing the dentin and person feels pulpal pan. Due to this any
cuspal locking of the occlusion is removed and the deciduous dental arches are unrestricted in
their masticatory movements.
The lower deciduous teeth then move forward enmass in their occlusal relations with
the upper deciduous teeth.
This causes the distal surfaces of the lower second deciduous molars to assume a
position farther mesially than the dental surfaces of the upper second deciduous molars. The
permanent first molars now can erupt into a normal class I occlusion (Fig 6)
In contrast in the civilized man’s deciduous dentition, the absence of attrition prevents
the forward movement of the lower deciduous teeth and hence the forward movement of the
whole of the lower deciduous dental arch relative to the upper. This in many instance prevent
the lower first permanent molar to erupt for enough mesially in proper occlusal relation with
the upper first permanent molar.

35
Attritional occlusion in permanent teeth :
When Stone Age man’s permanent incisors first erupt there is an overbite, however
due to his rough diet; there is attrition and ultimately the incisors are worn … to an edge-to-
edge bite. Thus a flat plane of attrition of the incisors in the same straight line is formed and
hence the curve of spee also gets flattened out. The elimination of the incisal overbite allows
the Stone Age man’s lower permanent incisors to tip labially to their correct prcumbency. On
the other hand, the persistence of the incisors overbite in civilized man causes the cover
permanent incisors to be held in anatomically and functionally incorrect upright positions.
Eruption of third permanent molars in stone age man and civilized man :
Begg further substantiates that attritional occlusion is normal by stating that the
eruption and coming into occlusion of civilized mans third permanent molars are often
prevented or retarded due to the absence of tooth attrition and by the subsequent inability of
all the teeth mesial to the third permanent molars to migrate mesially. Moreover, the third
molars are the only teeth that have their root formation completed before eruption leads to the
complete impaction. Whereas the third molars confirm to the behaviors of all other human
teeth by erupting before complete root formation in the attrition dentition of stone age man.
Anterior tooth relationships and lip balance attritional occlusion :
The end on relationship of the anterior teeth in the Stone Age man permitted the lower
lips to press directly against the upper and lower teeth. Therefore upper anterior teeth retained
their correct axial relations and the lower anterior teeth experienced far as crowding than
civilized mans.
In civilized mans, lower lip pressed against upper teeth, which in turn press the lower
teeth. Therefore lower teeth is pressed in a single direction and therefore held upright. This is
conducive to crowding of lower anterior teeth, especially in absence of attritional occlusion
the force that contributes to lower anterior tooth crowding.
The attritional loss in both deciduous and permanent dentitions of stone age man’s
anterior overbite together with the wearing away of the cusps of all of his teeth, frees the
lower dental arch from the upper and permitting it to move anteriorly. The mandible was also
free to move in relation to the maxilla. This often eventually resulted in an Angle class III
occlusion of teeth. This in civilized can is regarded as malocclusion but which is considered
proper evolutionary occlusion for man.
Proximal wear provides space for eruption of canine:
In attritional occlusion deciduous teeth are worn away quickly, both proximally and
occlusally. The proximal wear can result in increased space for later erupting permanent
teeth, such as canine. In civilized man, where virtually no proximal attrition occurs on the
neighbors of their predecessors, the permanent canine frequently lacks adequate space for
eruption.
A change in the curve of Wilson and a reason for cusps of carabelli :
When the teeth first erupt into occlusion, the curve of Wilson, as we know it, exists-
lingual cusps of upper molars are higher than the buccal cusp and vice on the lower. As wear
progresses, the plane become horizontal, then begins to slant downward on the buccal, and up
on the lingual –the opposite of “text book” occlusion. This angle of wear helps explain the
evolutionary value of cusps of carabelli. In this situation, they quickly come into occlusal

36
contact to provide greatly increase occlusal surface area as attrition proceeds. Extra cusps
have also been seen on the buccal surfaces of mandibular molars in some pacific Island races.
This cusp would serve the same purpose as the cusp of carabelli-survival through a more
efficient and long lasting dentition.
SIMULATION OF STONE AGE MAN’S DENTITION IN THE DIFFERENTIAL
FORCE METHOD OF ORTHODONTIC TREATMENT
Dr. Begg summarized his finding of Stone Age man’s dentition and justified
reduction of tooth material (extraction or proximal stripping) of civilized mans dentition for
the correction of malocclusion.

37
CONCLUSION
Dentistry has made numerous exhaustive attempts to understand occlusion. It has
proposed various arrangements and contours of chewing surfaces most of which were taken
from observing severe by worn dentition. Knowledge of functional occlusion is very
inevitable these days.
There is a long way to go until we actually understand all aspects of occlusion.

38
BIBLIOGRAPHY
1. Graber T.M.- Orthodontic Principles and Practice-3rd
edition.
2. Guyton –Textbook of Medical Physiology_8th
edition.
3. Moyers- Handbook of Orthodontics – 4th
edition.
4. Profitt- Contemporary Orthodontics- 3rd
edition.
5. Chaudhuri-Consise Medical Physiology-2nd
edition.
6. Chaurasia-Human Anatomy(Head and neck)-3rd
edition.
7. Jeffrey P.Okeson-Management of temporomandibular disorders and
occlusion-4th
edition.
8. Shafers- Textbook of Oral Pathology-4th
edition.

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