deptt. of prosthodontics & crown &bridge

CONCEPTS OF OCCLUSION IN COMPLETE DENTURE

SEMINAR

VIKAS AGGARWAL

INDEX

1. INTRODUCTION

2. DIFFERENCE BETWEEN NATURAL AND ARTIFICIAL

DENTITION

3. REQUIREMENTS OF COMPLETE DENTURE OCCLUSION

4. CONCEPTS OF OCCLUSION

5. VARIOUS THEORIES OF OCCLUSION

6. BALANCED OCCLUSION

7. NON BALANCED OCCLUSION/MONOPLANE OCCLUSION

8. LINGUALIZED OCCLUSION

9. ORGANIC CONCEPT OF OCCLUSION

10.TYPES OF OCCLUSAL SCHEMES

11.CONCLUSION

CONCEPTS OF OCCLUSION

INTRODUCTION

Occlusion is a factor that is common to all branches of dentistry. The study of

occlusion and its relationship to function of the masticatory system has been a

topic of interest in dentistry since many years. One of the chief aims of

preventive and restorative dentistry has been to maintain an occlusion that will

function in harmony with the other components of the masticatory mechanism,

thereby preserving their health and at the same time providing the optimum, if

not maximum masticatory function.

OCCLUSION: according. to GPT 8th ed

a) Act or process of closure or of being closed or shut off

b) The static relationship between the incising or masticating surfaces of the

maxillary or mandibular teeth or tooth analogues

ARTICULATION: It is defined as the dynamic contact relationship between

the occlusal surfaces of the teeth during function. ( GPT 8th)

Sliding occlusion is the contacting of teeth in motion. Sliding occlusion occurs

when the occlusal surface of the teeth make contact when the mandible is

moving.

Centric occlusion is the position of mandible when the relationship of the

opposing occlusal surface that provides the maximum planned contact and / or

intercuspation. Centric occlusion with teeth present is the tooth-to-tooth relation

whereas centric relation is a static position, is a bone-to-bone relation.

Eccentric occlusion is a contacting of teeth or occluding surface when the jaws

are in any other relation other than centric occlusion

Differences between natural and artificial occlusion:

1. The teeth in natural dentitions are retained by periodontal tissues that are

innervated by proprioceptive fibres. In edentulous mouths, both occlusion and

proprioceptive feedback mechanism are lost. In complete denture occlusion all

the teeth are on bases seated on movable tissues.

2. In natural dentitions the teeth receive individual pressures of occlusion and

can move independently to adjust to occlusal pressures. The artificial teeth

move as a unit on a base.

3. Malocclusion of natural teeth may be uneventful for years. Malocclusion of

artificial teeth evokes an immediate response and involves all of the teeth and

the base.

4. Non vertical forces on natural teeth during function affect only the teeth

involved, are usually well tolerated, whereas in artificial teeth, the effect

involves all of the teeth on the bases and is traumatic.

5. Incising with the natural teeth does not affect the posterior teeth whereas

incising with artificial teeth affects all of the teeth on the base.

6. In natural teeth, the second molar is the favoured area for masticating hard

foods, owing to more favourable leverage and power. Heavy pressures of

mastication in the second molar region with artificial dentition will tilt the base.

7. In natural teeth, bilateral balance is rarely found, and if present it is

considered balancing side interference. In artificial teeth bilateral balance is

generally considered necessary for base stability.

8. In natural teeth, prematurities are avoided due to neuromuscular system

control and establish stable habitual occlusion away from centric relation. In

artificial occlusion any prematurity causes instability due to lack of feedback.

Requirements of Complete Denture Occlusion

According to Ortmann (1971) the requirements of complete denture

occlusion which are:

1. Stability of occlusion at centric relation position and in area forward and

lateral to it.

2. Balanced occlusal contacts bilaterally for eccentric contacts.

3. Unlocking the cusps mesiodistally to allow for gradual but inevitable settling

of the bases due to tissue deformation and bone resorption.

4. Control of horizontal force by buccolingual cusp height reduction according

to residual ridge resistance form and inter arch distance.

5. Functional lever balance by favourable tooth to ridge crest position.

6. Cutting, penetrating and shearing efficiency of occlusal surfaces.

7. Anterior incisal clearance during posterior masticatory function.

8. Minimum occlusal contact areas for reduced pressure in communiting food.

9. Sharp ridges or cusps and generous sluice ways to shear and shred food with

the minimum of force necessary.

These requirements can be applied if the occlusion is divided into 3 distinct

units incising, working, and balancing.

Requirements for incising units:

1. These units should be sharp in order to cut efficiently.

2. They should not contact during mastication.

3. They should have as flat incisal guidance as possible considering esthetics

and phonetics.

4. They should have horizontal overlap to allow for base settling without

interference.

5. They should contact only during protrusive incising function.

Requirements for working occlusal units:

1. They should be efficient in cutting and grinding.

2. They should have decreased bucco-lingual width to minimize the work force

directed to the denture foundation.

3. They should function as a group with simultaneous harmonious contacts at

the end of the chewing cycle and during eccentric excursions.

4. They should be over the ridge crest in the masticating area for lever balance.

5. They should have a surface to receive and transmit the force of occlusion

essentially vertically.

6. They should centre the work load near the anteroposterior centre of the

denture.

7. They should present a plane of occlusion as parallel as possible to the mean

foundation plane.

Requirements for balancing units:

1. They should contact on the second molars when the incising units contact in

function.

2. They should contact at the end of the chewing cycle when the working units

contact.

3. They should have smooth gliding contacts for lateral and protrusive

excursions.

Axioms for artificial occlusion were published by Sears in 1952 which have

guided the planning of complete denture occlusion for many years:

1. The smaller the area of occlusal surface acting on food the smaller will be the

crushing force on food transmitted to the supporting structures.

2. Vertical force applied to an inclined occlusal surface causes non vertical

force on the denture base.

3. Vertical force applied to an inclined supporting tissue causes non vertical

force on the denture base.

4. Vertical forced applied to a denture bases supported by yielding tissue causes

the base to teeter when the force is not centred on the base.

5. Vertical force applied outside (lateral) to the ridge crest creates tipping force

on the base.

CONCEPT’S OF OCCLUSION

Occlusion must satisfy physiologic requirement and be acceptable to

the patient. When considering the concepts of occlusion, one must review

certain factors which will govern a satisfactory arrangement of teeth for

complete denture.

There is no scientific proof that any one concept of occlusion will

satisfy the entire requirement of a complete denture in a patient. There is

likewise no scientific proof that one tooth form is more efficient than other

tooth form. It is almost impossible to conduct a scientific investigation that will

give definite predictable results of the reactions of the basal seat to denture.

Clinical observation and evaluation are not always reliable. Competent

prosthodontics differs in their evaluations.

Theory means observation based on principles and concept is application of

theory. In pertinence to occlusion the concept of occlusion for complete denture

falls in to two broad disciplines (Heartwell 5th ed)

1) Balanced occlusion.

2) Non-balanced occlusion.

Any occlusion other than balanced occlusion is referred to as non-balanced

occlusion. This includes arrangement according to, Spherical theory, Organic

occlusion, Neutrocentric concept

Concepts of occlusion according to Boucher (11th ed)

1. Balanced

2. Monoplane

3. Lingualized

Various Theories of occlusion

1. Bonwill theory of occlusion

2. Conical theory of occlusion

3. Spherical theory of occlusion

1) BONWILL THEORY OF OCCLUSION 1858

He developed the theory of equilateral triangle, in which there was a 4-inch

distance between the condyles and between each condyle and incisor point. This

theory proposed that teeth move in relation to each other as guided by the

condylar controls and the incisal point

2) CONICAL THEORY OF OCCLUSION R.E. Hall (1915)

Theory proposed that the lower teeth move over the surfaces of the upper teeth

as over the surfaces of a cone with a generating angle of 45 degree and with a

central axis of the cone tipped at a 45 degree angle to the occlusal plane.

The Hall automatic articulator designed by R.E. Hall is an example of such a

theory.

3) SPHERICAL THEORY

This theory was proposed by G.S. Monson in 1918 and was based on the

observations of natural teeth and skulls made by Von Spee.

This form of occlusion is sometimes referred to as having Monson's Curve.

The spherical theory shows the lower teeth moving over the surface of the upper

teeth as over the surface of a sphere of a diameter 8 inches (20 cms.).

The center of the sphere is located in the region of the glabella and surface of

the sphere passes through the glenoid fossa along the articulating eminences or

concentric with them.

VARIOUS CONCEPTS OF OCCLUSION

A) BALANCED OCCLUSION

Definition: “The simultaneous contacting of maxillary and mandibular teeth on

right and left and in the posterior and anterior occlusal areas in centric and

eccentric positions.”-Heartwell

It is defined as “stable simultaneous contact of the opposing upper and lower

teeth in centric relation position and a continuous smooth bilateral gliding from

this position to any eccentric position within normal range of mandibular

function.”-Winkler

Balanced occlusion involves the arrangement of the teeth to provide even tooth

contact between posterior and anterior teeth as the mandible moves to and from

centric and eccentric positions. The purpose of this arrangement of the teeth is

to provide stabilizing forces to the denture bases on their basal seat when the

teeth make contact and the jaws are in centric and eccentric relation. This type

of articulation helps to maintain the stabilizing forces as mandible moves the

teeth to and from centric occlusion and eccentric occlusion.

When artificial cusp form teeth are arranged for complete denture it is possible

that the occlusal surface of the teeth should be altered to allow freedom of tooth

movement in harmony with the rotation when it occurs in fossae. The freedom

of tooth contact is accomplished by altering the fossae of the tooth both

anteroposteriorly and mesiodistally. When a non-cusp form posterior tooth is

used this freedom exists. In both situations the anterior teeth are arranged or

altered to allow this freedom of movement. The anterior teeth are not arranged

in contact when the jaws are in centric relation.

This concept of occlusion is similar to alteration of natural teeth to develop

freedom in centric or long centric relation and includes concept of balanced

occlusion. This concept does not imply that centric relation is an area; it means

that centric occlusion for some individuals may be an area.

a) the most retruded position of mandible with posterior teeth in maximum

intercuspation at given vertical dimension.

b) Centric occlusion anterior to centric relation: first position of tooth contact

(1): maximum intercuspation of posterior teeth

(2) This is often referred to as acquired centric occlusion with natural teeth but

the use of centric is confusing

C) Long centric occlusion: position of first tooth contact (1) The freedom of

tooth contact between points 1 and 2 is accomplished by altering the fossae of

the tooth both anteroposteriorly and mesiodistally

Concepts Proposed To Attain Balanced Occlusion

1) Gysi’s concept (1914) - for the use of 33 degree anatomic teeth under

various movements of articulator to enhance stability of denture.

2) Sear’s concept (1920) - Balanced occlusion for non-anatomical teeth with

anteroposterior & lateral curvature or use of second molar ramp.

3) Pleasure’s concept- Also called posterior reverse lateral curve. In 1937,

Dr. Max Pleasure described a reverse occlusal scheme in which the posterior

teeth are set with buccal tilt providing total lever balance during function.

Buccal tilt is given at the premolars , no tilt or flat occlusal surface at first

molars and a lingual tilt (Monson curve) to second molars.

The reverse curve is created to direct forces of occlusion lingually to favor

stability of lower denture. Lingual tilt of the second molar provides a buccal rise

to provide for a lateral balancing contact.A compensating curve is developed in

the first and second molar area to provide for protrusive balance.

This scheme is especially beneficial for patients with class II jaw relation.The

lever balance obtained in the premolar area is nearly at the anterio-posterior

center of the denture foundation coinciding with the zone where class II patient

functions during light to heavy intermediate chewing..

4) French concept (1954)- Increasing the stability of denture by reducing the

occlusal table of lower posterior teeth while maintaining the balanced concept.

He arranged upper first premolar with 5 degree of inclination, upper second

premolar with 10 degree of inclination, upper molars with 15 degree of

inclination.

5)Frush’s concept-1966 – (linear occlusion) One dimensional contact between

opposing posterior teeth that initially could be arranged to balanced articulation

on dental instruments followed by interocclusal shaping to obtain balanced

articulation.

Linear occlusion is a one dimensional contact between two opposing posterior

teeth. The contact occurs only in one dimension which is the length of the

contacting blade (not surface). This blade, being always in the form of a straight

line, geometrically constitutes “length” in occlusal contact without either

“width” or “depth” of occlusal contacts.

Intent of this occlusion was to remove occlusal deflective contacts and provide

greater stabilization of dentures.

REQUIREMENTS OF BALANCED OCCLUSION

1. All the teeth of working side should glide evenly against the opposing

teeth.

2. No single tooth should produce any interference or disocclusion of other

teeth.

3. There should be contacts in balancing side, but they should not interfere

with the smooth gliding movement of the working side.

4. There should be simultaneous contact during protrusion

SIGNIFICANCE:

Brewer (1963) found in a 24 hour test that:

”Normal individual makes masticatory tooth contact only for 10 mins in one

day compared to 24hrs of total tooth contact during other functions. So, for

these 24hrs of tooth contact, balanced occlusion is important to maintain

denture stability

It improves the stability of denture, reduce resorption of the residual ridge and

soreness and improve oral comfort & well-being of the patient.

BALANCE AS RELATED TO COMPLETE DENTURE

When forces act on a body in such a way that no motion results, then

there is balance or equilibrium. This should be the primary aim of the dentist i.e.

to achieve a stable base. In order to do so the following axioms have to be

followed: by Sears

1. The wider and larger the ridge and closer the teeth are to the ridge, the

greater the balance.

2. Conversely, the smaller and narrower the ridge and farther the teeth from

the ridge, the poorer the balance

3. The wider the ridge and narrower the teeth buccolingually, the greater the

balance.

4. Conversely, the narrower the ridge and wider the teeth, the poorer the

balance.

5. The more lingual (with-in limits provided by the tongue) the teeth are

placed in relation to alveolar ridge crest, the greater the balance.

6. The more buccal the teeth are positioned, the poorer the balance.

TYPES OF BALANCE

Balance may be unilateral, bilateral, or protrusive.

1) UNILATERAL LEVER BALANCE

This is present when there is balance of the base on its supporting

structures when food bolus is interposed between the teeth on one side and a

space exits between the teeth on the opposite side. Following points encourages

the lever balance-

a) Teeth placement should be such that to direct the resultant force on the

functioning side over the ridge or slightly lingual to it.

b) Having the denture base cover as wide an area on the ridge as possible.

c) Placing the teeth as close to the ridge as other factors will permit.

d) Using as narrow a buccolingual width occlusal food table as practical.

2) UNILATERAL OCCLUSAL BALANCE

This is present when the occlusal surfaces of teeth on one side articulate

simultaneously, as a group, with a smooth uninterrupted glide.

3) BILATERAL OCCLUSAL BALANCE

This is present when there is equilibrium on both sides of the denture

due to simultaneous contact of the teeth in centric and eccentric occlusion. It

requires a minimum of three contacts to establish a plane of equilibrium. This

balance is dependent on the interaction of the incisal guidance, plane of

occlusion, angulations of teeth, compensating curve, and condylar guidance

4) PROTRUSIVE OCCLUSAL BALANCE

This is present when the mandible moves essentially forward and the

occlusal contacts are smooth and simultaneous in the posterior both on right and

left sides and on the anterior teeth.

It is slightly different from bilateral balance in that it requires a minimum

of three contacts, one on each side posteriorly and one anteriorly, and is

dependent on interaction of the same factors as bilateral occlusal balance.

ADVANTAGES OF BILATERALLY BALANCED OCCLUSION

Prime gave the concept of “ENTER BOLUS EXIT BALANCE” which

implies that introduction of food on one side will prevent the teeth of opposite

side from contacting and hence occlusal balance is impossible during

mastication.

However Sheppard (1964) later gave the concept of ENTER BOLUS

ENTER BALANCE according to which even while chewing, the teeth cut

through the bolus and come in contact with each other, for few fractions of a

second. Hence the stability of the denture is maintained during various

movements of mandible during chewing.

Moreover, the bilateral balanced occlusion is even more important during

functional and the parafunctional activities like swallowing of the saliva,

closing to seat the denture and bruxing of the teeth.

Balanced occlusion thus will make such episode less damaging to the

supporting structures during the times of stress

As Winkler stated balancing occlusion in complete dentures is like

changing stumbling prose to poetry.

1. Bilateral simultaneous contact help to seat the dentures in a stable position

during mastication, swallowing and maintain retention and stability of the

denture and the health of the oral tissues.

2. Due to cross-arch balance, as the bolus is chewed on one side, the balancing

cusps will come close or will contact on the other. The dictum “Enter bolus,

exit balance” is therefore refuted.

3. Denture bases are stable even during bruxing activity.

Disadvantages of Balanced Occlusion:

1. It is difficult to achieve in mouths where an increased vertical incisor overlap

is present – Class II cases.

2. It may tend to encourage lateral and protrusive grinding habits.

3. A semi adjustable or fully adjustable articulator is required.

FACTORS AFFECTING BALANCED OCCLUSION

Rudolph.L.Hanau 1930 described nine factors that govern the articulation

of artificial teeth .These nine factors are called the laws of balanced

articulation. Hanau later condensed these factors to 5 articulation factors and

named it the articulation Quint.

LAWS OF BALANCED ARTICULATION

1. Horizontal condylar guidance

2. Compensating curve

3. Protrusive incisal guidance

4. Plane of orientation

5. Buccolingual inclination of the tooth axis

6. Sagittal condylar pathway

7. Sagittal incisal guidance

8. Tooth alignment

9. Relative cusp height

HANAU’S QUINT

1. Condylar guidance

2. Incisal guidance

3. Orientation of occlusal plane

4. Inclination of the cusps

5. Prominence of the compensating curve

Thielmann subsequently simplified Hanau’s factors in a formula for Balanced

Articulation.

[K x I] / [OP x C x OK]

Where, K = Condyle guidance.

I = Incisal guidance.

C = Cusp height inclinations.

OP = Inclination of the occlusal plane.

OK = Curvature of the occlusal surfaces.

TRAPAZZANO CONCEPT

Trapazzano (1963) reviewed Hanau’s five factors and decided only 3

factors were actually concerned in obtaining balanced occlusion. He eliminated

need for compensating curve and plane of occlusion and called it Traid of

Occlusion. He said that plane of occlusion could be shifted to weaker ridges

hence its location is not constant and is variable with in interarch distance. He

also dismissed the need of compensating curves, according to him when we

arrange cusped teeth in principle these curves are produced automatically.

BOUCHER’S CONCEPT

Boucher in (1963) disagreed with Trapazzano and felt that the occlusal

plane could be located at various heights to favour a weaker ridge, and he

recommended that the occlusal plane "be oriented exactly as it was when the

natural teeth are present. He believed that this must be done to confirm to

anatomic and functional needs.

Boucher, unlike Trapozzano, felt there was a need for a compensating curve and

stated, "The value of the compensating curve is that it permits an alteration of

cusp height without changing the form of the manufactured teeth. If the teeth

themselves do not have cusps, the equivalence of cusps can be produced by

using a compensating curve. Boucher's concept is that

a) There are three fixed factors: The orientation of the occlusal plane, the incisal

guidance, and the condylar guidance;

b) The angulation of the cusp is more important than the height of the cusp

c) The compensating curve enables one to increase the effective height of the

cusps without changing the form of the teeth.

LOTT’S CONCEPT

Lott (1963) studied Hanau's work and clarified the laws of occlusion by relating

them to the posterior separation that is the resultant of the guiding factors. He

stated the laws as follows:

1. The greater the angle of the condyle path, the greater is the posterior

separation.

2. The greater the angle of the overbite (vertical overlap), the greater is the

separation in the anterior region and the posterior region regardless of the angle

of the condyle path.

3. The greater the separation of the posterior teeth, the greater, or higher, must

be the compensation curve.

4. Posterior separation beyond the ability of a compensation curve to balance

the occlusion requires the introduction of the plane of orientation.

5. The greater the separation of the teeth, the greater must be the height of the

cusps of the posterior teeth.

LEVIN’S CONCEPT

Bernard Levin (1978) described the laws of articulation in a Quad.

Levin’s concepts are similar to that of Lott’s, but he eliminates the plane of

occlusion. However Hanau’s five laws are found most acceptable.

As described by the Rudolph L.Hanau there are five factors involved

in balanced occlusion of CD. These factors are:

1. Inclination of the Condylar guidance

2. Inclination of the Incisal guidance

2. Inclination of the Plane of orientation

3. Prominence of Compensating curve

4. Height of cusps.

1. Condylar Guidance: Is the mandibular guidance generated by the condyles

traversing the contours of the glenoid fossa. It is one of the end controlling

factors. It is independent of tooth contact. The condylar path is determined

on the patient by a protrusive record and set on the instrument. It acts as a

posterior control factor.

As defined by G.P.T-8, it is mandibular guidance generated by the condyle

and articular disc traversing the contour of glenoid fossae.

Of the five factors governing the laws of articulation as given to us by

Hanau, the condylar inclination is one of the three most important and

necessary factors utilized in securing balanced articulation and forms one of

the end-controlling factors

There is controversy that whether condylar path is precise or not.

Kurth (1954) claims that condylar path is not same for varying incisal

guidance.

Payne (1951) has shown that mandible can move to follow steep cusps,

modified cusps and zero degree teeth when there is posterior harmony and

no anterior interference is present.

Weinberg (1976) has demonstrated that the condylar path may vary with the

variable pressure of function.

As stated by Hanau (and agreed by Trapozzanno) that the condylar

guidance is the factor edentulous patient presents and can no way be

modified by the operator.

Factors which determine the registration of condylar guidance are –

a) Shape of the bony contour of glenoid fossae;

b) Muscles attaching to the mandible ;

c) Limitation of the movement by attached ligaments.

d) The registration method used. i.e. If registration method require bases to

rest on tissue of mandible and maxilla, the REALEFF can modify the

recordings.(Hanau)

2. Incisal Guidance :

As defined by G.P.T- 8 It is the influence of the contacting surfaces of the

mandibular and maxillary anterior teeth on mandibular movements. And

incisal guide angle is defined as the angle formed by the intersection of the

plane of occlusion and a line within the sagittal plane determined by the

incisal edges of the maxillary and mandibular central incisors when the teeth

are in maximum intercuspation.

Trapozanno( 1963) defined it as the steepest angle formed with the

horizontal plane by drawing a line between the incisal edges of the maxillary

and mandibular incisors and cuspids of both right and left segments when the

teeth are in centric occlusion

It can be set by dentist in accordance with esthetics and phonetics. If the

incisal guidance is steep it calls for steep cusps, steep occlusal plane or a

steep compensating curve to affect an occlusal balance. This type of

occlusion is detrimental to the stability and equilibrium of the denture base.

For complete dentures the incisal guidance should be as flat as esthetics and

phonetics will permit. When the arrangement of the anterior teeth

necessitates vertical overlap, a compensating horizontal overlap should be

set to prevent dominant incisal guidance, from upsetting the occlusal balance

on the posterior teeth. Incisal guidance should never exceed the condylar

guidance. It is the anterior controlling factor.

The above 2 factors determine the movements of the articulator. In order

to achieve balance, the other 3 balancing factors are arranged to correspond to

these articulator movements.

In C.D construction it is largely under the control of the dentist, the

limitations governing it are-

a) Ridge relation,

b) Arch shape,

c) Ridge fullness

d) Inter ridge space

e) Phonetics and esthetic requirements of the patients.

3) PLANE OF OCCLUSION

According To G.P.T -8 it is defined as the average plane established by the

incisal and occluding surfaces of the teeth. Generally, it is not a plane but

represents planer mean of the curvature of these surfaces.

This plane is established in anterior region by the height of lower cuspid which

coincides with the commissure of the mouth and in the posterior region by the

center (Winkler) or junction of posterior and middle third of the retromolar pad

(Boucher).

These landmarks also provide a physiologically and functionally acceptable

anteroposterior inclination of the occlusal plane that is nearly parallel to the

lower mean foundation plane.

These landmarks also creates an occlusal plane essentially parallel to the ala-

tragus line (Camper`s plane)

Okane (1979) showed that when occlusal plane is parallel is to the ala – tragus

line, the closing force during maximum clenching was greater than when it was

altered by +/- 5 degree.

Tilting of plane of occlusion beyond 10 degree is not advisable.Its position can

be altered only slightly without creating serious functional problem. Its role is

not as important as are the other determinants

4) COMPENSATING CURVE

According To G.P.T -8 , it is defined as (1) the anterio-posterior curving (in

median plane) and the medio-lateral curving ( in frontal plane) within the

alignment of occluding surfaces and incisal surfaces of artificial teeth used to

develop balanced occlusion.

(2) The arc introduced in the construction of complete denture to compensate

for the opening influence produced by the condylar and insical guidance's

during lateral and protrusive mandibular excursive movements

It is determined by the inclination of the posterior teeth and their vertical

relationship to the occlusal plane so that the occlusal surface results in a curve

that is in harmony with the movement of the mandible as guided by the

condylar path posteriorly and incisal guidance anteriorly

A steeper condylar path requires a steeper compensating curve. A lesser

compensating curve for steeper condylar guidance would result in steeper

incisal guidance acting as anterior interference, causing loss of molar balancing

contacts.

The primary function thus of compensating curve is to provide balancing

contacts for protrusive mandibular movements. Without this curve it would be

necessary to incline the entire occlusal plane at an angle

5) INCLINATION OF THE CUSPS/ CUSPAL ANGULATION

It is also a determinant, as it modifies the effect of the plane of occlusion and

the compensating curve.

The angulation of the cusp is more important than the height of the cusps.

The mesiodistal cusp heights that interdigitate lock the occlusion so that

reposition of the teeth due to setting of the base cannot take place. To prevent

this problem, it is advocated that all mesiodistal cusp heights be eliminated in

anatomic type teeth. With the teeth so modified, only the buccolingual inclines

need be considered as determinants of balanced occlusion.

Out of the five factors, only four can be controlled by the dentist.

1) The incisal guidance and plane of occlusion can be altered but only slightly

because of esthetic and phonetic limitations.

2) The main factors which can be used and changed effectively are

compensating curve and inclinations of the cusps of the teeth

3) The inclination of the occlusal plane: Plane of orientation is established in the

anterior by height of the lower cuspid and in the posterior by the height of the

retromolar pad. Its position can be altered only slightly.

4) The compensating curve is one of the most important factors in establishing a

balanced occlusion. The compensating curves eliminate Christensen’s

phenomenon to achieve balance. It is determined by the inclination of the

posterior teeth and their vertical relationship to the occlusal plane so that the

occlusal results in a curve that is in harmony with the movement of the

mandible.

The anteroposterior curvature of the occlusal plane is desired to permit

protrusive disocclusion of the posterior teeth by the combination of anterior

guidance and condylar guidance.

Mediolateral curve: It results from the inward inclination of the lower posterior

teeth, making the lingual cusps lower than buccal cusps on the mandibular arch

and buccal cusps higher than the lingual cusps on the maxillary arch. Aligning

the teeth according to the above produces the greatest resistance to masticatory

forces.

5) Cusp height and inclination: These are important determinants, as they

modify the effect of the plane of occlusion and the compensating curve.

All the five factors of balance interact with each other. The dentist can

control only four of the 5 factors, since the condylar path is fixed by the patient.

Incisal guidance and plane of occlusion can be altered only slightly. The

important working factors for the dentist to manipulate are the compensating

curve and the inclinations of cusps on the occlusal surfaces of the teeth.

Balance in non anatomic teeth:

It can be accomplished in two ways. One can either set the teeth in a

compensating curve as is done in anatomic forms, or one can set the teeth in a

flat plane, and utilize a balancing ramp just distal to the 2nd molar. This ramp

adjusted so that the upper 2nd molar will contact it eccentric movements and thus

provide three point contacts.

Pleasure (1937) set premolars and 1st molars in an anti-Monson curve;

this avoids a tipping force and seats the denture. In order to provide eccentric

balance during tooth contacts the 2nd molars are set in the conventional Monson

curve. This combination of Monson and anti-Monson curve in posterior

occlusion is often referred to as the pleasure curve.

Trapozzano (1960) studied the masticatory performance of balanced and

non-balanced occlusion in complete denture patients and concluded that

masticatory efficiency with balanced occlusion was only slightly greater but the

stability was definitely enhanced.

B) Non-balanced occlusion

When the requirement for balanced centric and eccentric occlusion and

balanced sliding occlusion are accepted as requisites for balanced occlusion, it

follows that all other occlusal arrangement are non-balanced occlusion. The

arrangement of teeth according to the spherical theory, organic occlusion, and

occlusal balancing ramps for protrusive balance and transographic and on a

plane may be classified as non-balance occlusion.

Non-balanced occlusion is an arrangement of teeth with form or purpose.

Acceptance of the concept of non-balanced occlusion includes acceptance of the

following

1. The character of the supporting foundation makes it almost impossible to

harmonize tooth arrangement with mandibular movement in the eccentric

relation to the maxillae and to maintain this harmony.

2. The contacting of the teeth during masticatory and non-masticatory

mandibular movement occurs when the mandible is in centric relation to

the maxillae.

3. The artificial teeth should not contact when the mandible is in eccentric

relation to the maxillae because when jaws are eccentrically related and

the teeth contact, horizontal and torqueing forces are directed to support.

These forces are un stabilizing and potentially destructive to supporting

tissue.

4. When the jaws are in centric relation and the contact of the teeth produces

no discomfort to the supporting tissue or the joints, the patient is

encouraged to make similar maxillo mandibular relation repeatedly.

CONCEPTS OF NON BALANCED OCCLUSION

Pound's concept -He proposed a monoplane occlusion which stresses the

importance of phonetic and aesthetics for anterior teeth. The posterior teeth on

the other hand have a sharp upper cusp and a wide lower central fossa. The

buccal cusps of the lower posterior teeth were reduced to avoid deflective

contacts.

In effect it was lingualized occlusion where in there is no buccal contact of

upper and lower teeth and the occlusal surfaces are reduced such that they lie in

a triangle formed between the mesial end of the canine and the two sides of the

retromolar pad.

Gold surface occlusal concept-33 degree teeth with full occlusal gold surface

are used to attain non balanced concept. Extreme vertical overlaps producing

cuspid guidance are frequently used resulting in disocclusion of posterior teeth

away from maximum intercuspation position.

Hardys concept- A straight horizontal occlusal plane using non anatomical

teeth is used to establish non balanced occlusion.

Occlusal pivots by Sears- The pivots were used to place the mandible in

equilibrium by concentrating the load in the molar regions. This scheme

reduced the injury to the temporomandibular joint and also reduced the stress in

the anterior region.

Kurth's concept- He proposed a non-balanced occlusion set with flat posterior

teeth in a horizontal plane without any balancing ramps. The teeth were set in a

flat plane anteroposteriorly with a reverse lateral curve

Philip M. Jones scheme of non-balanced occlusion 1972 -In this scheme,

non-anatomical teeth were arranged with the following modifications:

1. Different articulator that could fit large casts was used. He advocated

barn hinge door articulator.

2. The maxillary and mandibular teeth were arranged without any vertical

overlap.

3. The jaw relation determined the amount of horizontal overlap.

4. The maxillary posteriors were set first and the occlusal plane must fill

certain requirements

a) Occlusal plane should divide interarch space equally.

b) Occlusal plane should be parallel to mean denture base foundation

c) Occlusal plane should lie at middle and upper third of retromolar pad.

5. During final arrangement, there should be complete intercuspation

between the upper and lower posterior teeth except the second molar.

6. The occlusal surface of the upper second molar should be 2 mm above

the plane of occlusion (hence it is out of occlusion) and parallel to the

occlusal surface of the lower second molar.

7. These modifications are done so that the premolars and the first molars

are the primary masticators and the second molars are just non-functional

space fillers.

NEUTROCENTRIC CONCEPT OF OCCLUSION (MONOPLANE

OCCLUSION)

Devan in 1954 suggested the concept of neutrocentric occlusion

This concept of occlusion assumes that the anterior-posterior plane of occlusion

should be parallel to the denture foundation area and not dictated by condylar

inclination.

The plane of occlusion is completely flat and level. There is no curve of Wilson

or Curve of Spee (compensating curve) incorporated into the set up. In

mediolateral direction teeth are set flat with no medial or lateral inclination. The

patient is instructed to avoid incising with the anterior teeth; therefore there is

no need to concern for sagittal condylar inclination. Because there are no cusp

on teeth, when incising is avoided and no cusp project above or below the

occlusal plane then horizontal condylar guidance may be set to zero.

Since teeth are not arranged for balanced contact when jaws are eccentrically

located lateral condylar guidance may be set zero.

There is no vertical overlap of the anterior teeth.

When using this concept of occlusion the patient is instructed not to incise the

bolus. With this tooth arrangement DeVan noted that “the patient will become a

chopper, not a chewer or a grinder.”

Acc. to DeVan the main objectives of neutrocentric concept are-

I – Neutralization of the inclines and,

II – Centralization of the occlusal forces acting on the denture foundations.

In order to attain these objectives, it is necessary to reduce the size and number

of teeth and to abandon attempts to secure balancing contacts in eccentric

positions beyond the range of masticatory stroke

According to DeVan, the five factors involved in the relation of the teeth to

dental foundation are:

(a) POSITION

There is probably no single factor as important as position.

Acc. to DeVan posteriors should be positioned in as central position on the

foundation as allowed by the tongue, this way denture will be more stable due

to enhanced lever balance, and more of the osseous foundation will be saved by

the harmful tensile and shearing forces acting on bone and the overlying mucosa

Acc. to DeVan the employment of lateral balance intensifies rather than

alleviates the problem of stabilizing the denture.

Eccentric balance does help to maintain retention; but if the use of

inclines is essential for its establishment, then bilateral balance causes a

decrease in stability.

Balancing inclines shift the denture farther toward the side of the

mastication, preventing its dislodgement while increasing its side

displacement.

B) PROPORTION

DeVan recommends reduction in the proportion of the artificial teeth as

compared to size of natural teeth.

Reduction in proportion is necessary to develop centralization of forces,

Reduction of frictional forces developing on occlusal surfaces which will

transfer to the underlying mucosa and bone.

Reduction by 40% in width is possible without serious diminution of the

food table

C) PITCH

Pitch is synonymous with inclinations or tilt.

In neutrocentric concept the plane of occlusion should be oriented so that

it is midway and parallel to mean foundation planes of the maxilla and

the mandible.

The compensating curve should be neutralized so that posteriors are

placed on a plane rather than on spherical surface.

D) FORM

Artificial posterior teeth should be devoid of projecting cusps.

Contacting occlusal lines should be on a single plane.

This arrangement will avoid interference from TMJ and their inclines.

E) NUMBER OF TEETH

DeVan recommends reduction in no. of teeth from 8 per denture to 6 per

denture.

This will aid in stability by freeing the lower ridge molar incline of

occlusion.

Elimination of 2nd molar will result in establishment of centralization and

reduction in occlusal area

C) LINGUALIZED OCCLUSION

Acc. to GPT-8, lingualized occlusion is defined as the form of denture occlusion

in which the maxillary lingual cusps articulate with the mandibular occlusal

surfaces in centric, working and balancing mandibular positions.

Although S. H. Payne(1941) has being credited for being the first one to

describe, it was Gysi (1927) who used this scheme approximately 20 years

earlier(1927).

Payne 1941 credited Farmer with development of this technique, and provided a

brief description of the required laboratory procedures. According to Payne’s

article, a mortar-and-pestle arrangement was created via judicious recontouring

of 30-degree teeth.

Pound (1970) used maxillary teeth having cusp angles greater than 30 degrees

in conjunction with mandibular teeth having cusp angles of 20 degrees or less.

He carefully reshaped mandibular fossae to produce cross-arch balance. Like

his predecessors, Pound ensured that maxillary buccal cusps did not contact

mandibular teeth during eccentric mandibular movements. He accomplished

this by reducing the facial surfaces of the mandibular posterior teeth rather than

elevating the buccal cusps of the maxillary teeth.

Generally, maxillary teeth with cusp angles of ≥30 degrees are opposed by

mandibular teeth displaying cusp angles of ≤20 degrees are used.

The posterior teeth selected for lingualized occlusion differ depending upon

whether balanced or non balanced occlusion is used.

A balanced scheme usually involves maxillary tooth with sharply pointed

lingual cusp to oppose mandibular tooth with an uncomplicated occlusal table

including only shallow inclines.

For a non balanced lingualized occlusion monoplane mandibular denture tooth

is selected.

Clough et al 1983 examined chewing efficiency of monoplane versus

lingualized occlusion and reported that 67% of the patients in their study

preferred lingualized occlusion.

PRINCIPLES OF LINGUALIZED OCCLUSION

1. Anatomic posterior teeth are used for maxillary denture.

2. Non anatomic or semi anatomic teeth are used for mandibular denture.

3. Modification of mandibular posterior teeth is accomplished by selective

grinding.

4. Balancing and working contacts should occur only on the maxillary

lingual cusps.

5. Protrusive balancing contacts should occur only between maxillary

lingual cusps and lower teeth.

The advantages of lingualized occlusion are:

Lingualized occlusion yielded cross-arch balance. This resulted in

improved denture stability and enhanced patient comfort

Occlusal forces can be directed lingually without placing the teeth

lingually

It is especially useful where esthetic demands of the patient is high but

presenting oral conditions indicate non-anatomic teeth, e.g., severe ridge

resorption, class II & III jaw relationships and highly displaceable

supporting tissues.

The chewing efficiency is comparable to anatomic (semi) and definitely

superior to zero degree teeth

As mesiodistal locking is eliminated by grinding the transverse ridges of

the cusp teeth, freedom is provided in the occlusion to accommodate for

the settling of denture base.

The lateral thrust control (during functional and para-functional

movements) is provided by grinding the buccolingual inclines, which is

based on the shape and prominence of the ridge and its ability to

withstand lateral forces

The para-functional habits are usually confined to a zone of activity

around centric relation. The lingualized occlusion provides for smooth

balancing contacts with excursive movements of 2-3mm around centric

relation, owing to creation of common central fossa in mandibular

posteriors by selective grinding of transverse ridges in the process of

mesiodistal unlocking

Lingualized occlusion creates a more favorable lever by moving the

centric contacts from half tooth to lingual. This allows occlusal forces to

move more centrally there by contributing to more stable denture.

It minimizes the frictional contact between upper and lower occlusal

surfaces as there are only one area of contact.

There is only one contact point. This creates Mortar pestle type of

occlusion that provides a small area of contact for more efficiency and

control of lateral forces.

By allowing the maxillary cusp to function against a variety of opposing

occlusal surface, the advantage of many other occlusal schemes can be

accommodated while their disadvantages can be ignored.

Greatest advantage of balanced lingualized occlusion is esthetics. First the

presence of cusped tooth in maxillary premolar and first molar region looks

more natural when compared to zero degree teeth. Second the use of occlusal

curves for the purpose of balance allows for incisal overlap of anterior teeth.

The popularity of lingualized occlusion stems from simplicity and flexibility of

the concepts and from its wide application to clinical practice. Indeed this type

of occlusion may be used in any type of removable prosthodontic appliance and

in most cases, incorporates most of the advantages while eliminating or

neutralizing the disadvantages of many occlusal schemes. Lingualized is a truly

“OCCLUSION FOR ALL REASONS”

MYERSON’S LINGUALIZED INTEGRATION

Myerson proposed specialized tooth Molds for arranging teeth in lingualized

occlusion. He proposed two different molds for the maxillary posterior

namely control contact (cc) mold and Maximum contact (Mc) mold. The

remaining teeth are common for both these molds.

He advocates the use of ‘Mc’ Mold for patients who can reproduce accurate

centric position and ‘cc’ mold for patients with variation in centric position.

These teeth provide Maximal intercuspation, good cuspal height to perform

occlusal reshaping and a natural and pleasing appearance.

The ‘Mc’ Mold Maxillary posterior have taller cusps with a more anatomical

appearance compared to the ‘cc’ mold. The ‘Mc’ mold also offers a more

exacting occlusion.

ORGANIC CONCEPT OF OCCLUSION

Mutually protected occlusion is also known as canine protected occlusion or

''organic" occlusion. It had its origin in the work of D'Amico, Stallard and

Stuard. (1963)

According to this concept of occlusion, the anterior teeth bear the entire load

and the posterior teeth are disoccluded in any excursive position of the

mandible.

In organic or organized occlusion the arrangement of teeth should relate the

occlusal element of teeth so that the teeth will be in harmony with the muscles&

joints in function. The muscles & joints should determine the mandibular

position of occlusion without tooth guidance.

Organic occlusion has three phases of mutually interdependent protection

1. The posterior teeth should protect the anterior teeth in centric occlusal

position

2. The maxillary incisor should have vertical overlap sufficient to provide

separation of the posterior teeth when the incisors are in end-to-end

contact.

3. In lateral mandibular position outside the masticatory cyclic movement

the cuspid should prevent contact of all other teeth.

An articulator capable of receiving and reproducing pantograms in 3 planes is

recommended to develop the organic concept of occlusion.

This type of occlusion is more applicable in natural dentition and fixed partial

denture, than in complete dentures

TYPES OF OCCLUSION SCHEMES

Now let us discuss the three main occlusal schemes i.e.

Monoplane occlusion

Classical bilaterally balanced occlusion

Lingualized occlusion

It is of interest to note that none of the occlusal scheme has been proved

to be superior to other (for all presenting conditions of edentulous

mouths), although one type of scheme may offer some advantages over

other.

MONOPLANE OCCLUSION

Acc. To G.P.T -8 ,it is defined as an occlusal arrangement wherein the posterior

teeth have masticatory surfaces that lack cuspal height .

Hall (1929) is credited for the introduction of Zero degree teeth calling them

inverted cusp tooth, but these teeth have the problem of clogging of food in the

depressions onto the occlusal surfaces

Myerson later designed a cusp less teeth with series of transverse buccolingual

ridges and sluiceways between them.

ADVANTAGES OF MONOPLANE OCCLUSION / ZERO DEGREE

TEETH

1. They are more adaptable to unusual jaw relations such as Class II and

Class III malocclusions.

2. Zero degree teeth impart to the patient a sense of freedom because they

do not lock the mandible in one position only.

3. This is used more easily when variation in the width of upper and lower

jaws indicate a cross bite setup.

4. Centric occlusion is more of an area and less of a precise point in these

teeth hence they allow closure of jaws over a broad contact area.

5. Minimal horizontal pressures are created because of elimination of

incline plane.

6. Zero degree teeth permit the use of a simplified and less time consuming

technique and offer greater comfort and efficiency for longer duration.

7. They accommodate better to the inevitable negative changes in the ridge

that occur with aging.

As far as balanced occlusion is concerned in monoplane occlusion two

important concepts prevail-

A) Non Balanced occlusion (in centric relation only) E.g

Neutrocentric concept.

B) Balanced occlusion in centric relation and lateral excursions

This can be achieved with the use of compensating curve, balancing

ramps, Tripodization by tilting the 2nd maxillary and mandibular molars,

and using monoplane with zero overbite (but this will compromise

phonetics and esthetics.)

The 2nd category in monoplane occlusion involves bilateral balance in centric

and eccentric relations.

A) WITH COMPENSATING CURVE

Acc. to this concept –

A) No. of posterior teeth should be 3, i.e. mandibular 1st premolar should

be omitted.

B) Antero-posterior comp. curve begins at the DMR of the 2nd premolar

and continues till 2nd molar.

The amount of this curve is dependent on steepness of the condylar

guidance, but is rarely more than more than 20 degree from horizontal.

This curve is used to provide the needed tooth structure for protrusive

balancing contacts

Mediolateral compensating curve is also needed to achieve lateral

balanced contacts. This curve is initiated from first replacement tooth and

continued till the second molar. The degree to which the facial cusps are

elevated to establish this curve will vary with the condylar and incisal

guidances. The curve usually does not exceed 5-10 degree

B) WITH BALANCING RAMPS (NEPOLA 1958)

Balancing ramps provide a tripodization of the denture base.

As the patient moves the mandible from centric relation to

protrusive or lateral positions, there is smooth contact anteriorly on

the teeth and posteriorly on the ramps.

The balancing contacts give improved horizontal stability to the

dentures. Esthetics and phonetics are greatly enhanced because

there is more freedom in placing anterior teeth.

The ramps can be developed after the final try-in of the waxed

dentures or at the time of clinically remounting the dentures at the

insertion appointment

The procedure is performed on a properly adjusted articulator.

This technique can be applied to existing dentures by clinical

remount.

C) WITH TILTING THE SECOND MOLARS

Acc to C G Porter, mandibular second molar is inclined to provide

contact with maxillary dentures in all excursions.

The maxillary molars are also inclined but left out of centric contact.

He recommended the use of French modified posterior teeth which have

sub-occlusal surfaces of mandibular buccal cusps directing the occlusal

force downward and lingually.

CHARACTERISTICS ANATOMIC LINGUALIZED NEUTROCENT

RIC

ESTHETICS + + -

EASE ACCORDINGOF

PENETRATION OF FOOD

BOLUS

+ + -

DENTURE STABILITY (in

parafunct movt )

+ + -

SIMPLER TECHNIQUE - + +

DECREASED LATERAL

FORCES

- + +

EASE OF ADJUSTMENT - + +

CLASS II & III CASES - + +

STABILITY WITH

CENTRALIZED &

NEUTRALIZED FORCE

- + +

CONCLUSION

Many occlusal schemes have been proposed over the years. Most schemes when

correctly used gives satisfactory results. The result is satisfactory, if the patient

gets better function, esthetics & comfort without any adverse changes in denture

foundation.

REFERENCES:

1. Boucher's Prosthodontic Treatment for Edentulous Patients (12th Edition)

2. Boucher's Prosthodontic Treatment for Edentulous Patients (11th Edition)

3. Essentials of complete denture prosthodontics Sheldon Winkler 2nd ed

4. Textbook of complete denture Arthur O. Rahn, Charles M. Heartwell 5 th

ed

5. A Text book of occlusion Norman .D.Mohl 1988 1st edn

6. Trapazzano.R.V (1963), Laws of articulation. J Prosthet Dent, 13(1),34-

44

7. Boucher.O.C (1963), Discussion of Laws of articulation. J Prosthet Dent,

13(1),45-48

8. Ortman.R.H (1971), Role of occlusion in preservation and prevention in

complete denture prosthodontics. J Prosthet Dent, 25(2),121-138

9. Becker.M.C, Swoope.C.C, Guckes.A.D (1977), Lingualized occlusion for

removable prosthodontics. J Prosthet Dent, 38(6),601-608

10.Levin.B (1978), Reevaluation of Hanau’s law of articulation and Hanau’s

Quint. J Prosthet Dent, 39(3),254-258

11.Nimmo. A & Kratochvill. J. F (1985), Balancing ramp in non-anatomic

complete denture occlusion, J Prosthet Dent, 53(3), 431-433

12.Phoneix.D.R & Engelmeire.R.L (2010), Lingualized occlusion revisited,

J Prosthet Dent, 104(5), 342-346