Presented by :Dr. Avinash KumarIInd year P.GK.V.G Dental College & hospital, sullia

BALANCED OCCLUSION

AND ITS IMPORTANCE IN

COMPLETE DENTURE FABRICATION

Contents

• Introduction• Definitions• Requirements of complete denture occlusion• Theories of occlusion • Balanced occlusion: Definition Pre-Requisites• Parameters to success of occlusal balance• Types • Pro and Cons• Concepts of Balanced occlusion

• Factors that affect the occlusal balance• Characteristics of balanced occlusion in complete dentures• Steps • Selective grinding(correcting occlusal errors in balanced

articulation)• The retrognathic mandible• Lingualised articulation• Summary & conclusion• References

Introduction

However, there are rational ways to study occlusion, and

studying occlusion in complete dentures is a good starting

point, because of the need to place an entire dentition within a

system so that the edentulous patient can once again function

with the minimum of discomfort and the maximum possible

efficiency.

Occlusion in complete denture must be developed to function

efficiently and with the least amount of trauma to the

supporting tissues.

Features of natural occlusion

Intercuspal position is used during chewing, swallowing & deliberate clenching.In function -

Presence of unworn cusps results in separation of teeth on one side(most obviously during lateral movements & also in protrusive movements)

Artificial occlusion

Complete dentures remain static only when jaws remains static. All dentures move in function.

Prime aim- to ensure minimum movement & can be controlled by the patient to allow for optimal function.

When the artificial teeth do contact, they do so in the same way as in the

unworn natural dentition and leads to tipping, denture base tip up until the

teeth on other side met.

It would be therefore be entirely logical to try to achieve that situation in the

first place, an occlusion that balances both sides with each other, & anterior

part with the posterior part.

Definitions

Occlusion

Is defined as the static relationship between the incising or

masticating surfaces of the maxillary and mandibular teeth or tooth

analogue. (GPT)

According to Heartwell this is a static position and the jaws can be

in either centric or eccentric relation. Every time the teeth contact

there is a resultant force which may vary in magnitude and direction.

ArticulationThe contact relationship between the occlusal surfaces of the teeth during

function.(GPT)

Excursive movementMovement occuring when mandible moves away from maximum

intercuspation.

Balancing side/non-working sideThe side of mandible which moves towards median line in lateral excursion.

Balanced occlusionThe bilateral, simultaneous, anterior, and posterior occlusal contact of teeth in

centric and eccentric positions.

Centric occlusionThe occlusion of opposing teeth when the mandible is in centric relation. This

may or may not coincide with the maximal intercuspal position.(GPT 8) .Centric

occlusion is the tooth-to-tooth relation whereas centric relation is a static

position and a bone-to-bone relation.

Centric relation

The maxillomandibular relationship in which the condyles articulate with the thinnest

avascular portion of their respective discs with the complex in the anterior- superior

position against the slopes of the articular eminences. This position is independent of

tooth contact. This position is clinically discernible when the mandible is directed

superior and anteriorly. It is restricted to purely rotary movement about the transverse

horizontal axis.(GPT)

Transverse horizontal axisAn imaginary line around which the mandible may rotate within the sagittal plane.

(GPT)

Maximum intercuspationThe complete intercuspation of the opposing teeth, independent of condylar

position.

Eccentric occlusionEccentric occlusion refers to contact of teeth that occurs during movement of

the mandible.

It is of two types:-

1.Functional occlusion

2.Non functional occlusion

1.Functional occlusion

Functional occlusion (also called working side occlusion) refers to tooth

contacts that occur in the segment of the arch towards which the mandible

moves.

Functional occlusion can be of two types :

a. Lateral functional occlusion

b. Protrusive functional occlusion

a) Lateral functional occlusion:

It includes tooth contacts that occur on canines and posterior teeth on the side

towards which the mandible moves.

o The lateral functional occlusion can be of two types :

1. Canine guided occlusion:

2. Grouped lateral occlusion

i) Canine guided occlusion:

During lateral mandibular movement, the opposing upper & lower canines of

the working side contact thereby causing disclusion of all posterior teeth on

the working &, balancing sides.

Canine guided occlusion is usually seen in young individuals with unworn

dentition.

ii) Grouped lateral occlusion :

In addition to canine guidance, certain other posterior teeth on the working

side also contact during lateral movement of the mandible.

Such a type of contact during lateral movement is called grouped lateral

occlusion.

B) Protrusive functional occlusion:

It includes eccentric contacts that occur when the mandible moves forward.

Ideally the six mandibular anterior teeth contact along the lingual inclines of

the maxillary anterior teeth while the posteriors disocclude.

Requirement of Complete Denture Occlusion

(Winkler)

1. Stability of occlusion in centric relation and in areas forward and lateral to it.

2. Balanced for all eccentric contacts bilaterally for all eccentric mandibular movements.

3. Unlocking the cusp mesiodistally to allow for gradual but inevitable settling of the bases due to tissue deformation and bone resorption.

4. Control of horizontal forces by buccoligual cusp height reduction according to the residual ridge resistance and interridge space.

5. Functional lever balance by favorable tooth-to-ridge crest position.

Theories of occlusion

• Spherical theory

• Equilateral triangle theory

• Conical theory

Spherical theory of occlusion

Edgar et al 2002 The history of articulators: A clinical history of

articulators based on geometric theories of mandibular movement

This was given by Monson and the concept was derived from an idea

by Von spee.

Lower teeth moves over the surface of upper teeth as over the surface

of sphere with a diameter of 8inches(20cm).

Centre of sphere is in gabella.

Positioning of teeth with antero-posterior and medio-lateral inclines in harmony

with a spherical surface. Some times referred to as having Monson curve.

Surfaces of the sphere passes through glenoid fossa along the articular

eminences.

Bonwill’s equilateral triangle theory• Finn Tenges Christensen (1959) The

Effect Of Bonvill’s Triangle On Complete Dentures

The construction of average articulators is generally in accordance with Bonwill’s theory, and Monson’s pyramid is based also on Bonwill’s triangle.

This theory proposed that teeth move in relation to each other as guided by the condylar controls and the incisal point.

Conical Theory(1915)

The lower teeth move over the surfaces of the upper teeth as over the surfaces

of a cone and with a central axis of the cone tipped at a 45 degree angle to the

occlusal plane.

Various concepts of occlusion

In pertinence to occlusion the concept of occlusion for complete denture

falls in to two broad disciplines

1) Balanced occlusion. (Heartwell 5th ed)

2) Non-balanced occlusion.

Concepts of occlusion acc. to Boucher (13th ed)

•Balanced

•Monoplane

•Lingualized

Balanced Occlusion:• Reported by Brewer.

• “ 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

• Balanced occlusion involves a definite arrangement of tooth contacts in harmony with mandibular movement.-

Stansbery (TRAPOZZA V R.LAWS OF ARTICULATION. J. Pros. Den.Jan.-Feb., 1963;VOL-13 NO. 1)

• “The simultaneous contacting of the maxillary and the mandibular

teeth on the right and left side and in the posterior and anterior

occlusal areas in centric and eccentric positions, developed to lessen

or limit the tipping or rotating of the denture base in relation to the

supporting structures.-GPT

• “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

Need for balanced occlusion

Improved stability of denture

No interference of cusp during mastication

Preservation of ridges by better distribution of forces

Goals of balanced occlusion

Simultaneous contact in centric relation

Working side contact

Balancing contact in protrusion

Balancing contact in lateral excursion

Following axioms should be considered:1. The wider and larger the ridge and closure the teeth are to the ridge, the

greater the lever balance.

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

are placed from the ridge the poorer the lever balance.

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

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

balance.

5. The more lingual the teeth are placed in relation to the ridge the better the

balance.

6. The more buccal the teeth are placed to the ridge crest, the poorer the

balance.

7. The more centered the force of occlusion anterior-posteriorly, the greater

the stability of the base.

Types of Balanced Occlusion:

Balance may be -

•Unilateral,

•Bilateral, or

•Protrusive.

Unilateral lever balance:

This is present when there is equilibrium of base on its supporting structures

when a bolus of food is interposed between teeth on one side and space exists

between teeth on the opposite side.

• This state of equilibrium is encouraged by :

a) Placing the teeth so that the resultant direction of force on the functioning side

is over the ridge or slighty lingual to it.

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

c) Placing the teeth as close to the ridge as possible.

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

Unilateral occlusal balance:

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

simultaneously with smooth uninterrupted glide.

oThis is present when there is equilibrium on both sides of denture due to simultaneous contact of teeth in centric and eccentric occlusion.

oIt requires a minimum of three contacts. The more the contacts the more assured the balance.

Bilateral occlusal balance

Advantages of Bilateral 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.

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

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

day compared to 4hrs of total tooth contact during other functions. So, for

these 4hrs 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.

Pros & cons (Winkler)

The contact varies in frequency with different foods and different

persons. If this contact is interruptive and deflective; and not bilateral,

the denture base will not be stable. Hence, bilateral balanced contacts

during the terminal arc of closure help to seat the denture in a stable

position.

Also bilateral balanced occlusion is important during activities such as

swallowing saliva, closing to reseat the dentures, and the bruxing of the

teeth during times of stress.

Pros:

Patient with a balanced design do not upset the normal static, stable and

retentive qualities of their dentures.

In bilateral balance the bases are stable during bruxing activity and they are

tight when the patient separate the teeth.

There are some possible disadvantages of bilateral balanced articulation:

It may tend to encourage lateral and protrusive grinding, although this

habit may be confined to those people who are subjected to irrelevant

muscle activity.

It is difficult to achieve in mouth where an increased vertical incisor

overlap is indicated, and is better to retain the vertical overlap, than to

sacrifice it in order to achieve articular balance.

A semi-adjustable or fully adjustable articulator is required.

Cons:

This is present when the mandible moves essentially forward and

occlusal contacts are smooth and simultaneously in posterior region

both on right and left sides as well as anterior teeth.

It requires a minimum of three contacts, one on each side posteriorly

and one anteriorly

Protrusive occlusal balance:

CONCEPTS OF BALANCED OCCLUSION

o Gysi’s concept

o Sears’s concept

o French’s concept

o Pleasure’s concept

o Frush’s concept

o Hanau’s quint

o Trapazzano’s concept

o Lott’s concept

o Boucher’s concept

o Levin’s concept

GYSI’S CONCEPT

• He proposed the 1st concept towards balanced occlusion in

1914.

• He suggested arranging 330 anatomic teeth could be used

under various movements of the articulator to enhance the

stability of the denture.

• Truebyte

• In 1927 designed a modified Cross-bite posteriors.

Sears’s concept

• In 1922 & 1927, “Channel” tooth. To permit unlimited

protrusive glide .

• He proposed the balanced occlusion for non-anatomic teeth

using posterior balancing ramps or an occlusal plane which

curves anteroposteriorly & laterally.

French’s concept

• In 1935, modified Sear’s channel tooth with very shallow bucco-lingual

inclines to reduce the lateral thrust.

• And mandibular teeth with narrow mesio-distal table moved lingual of

occlusal surface and a sloping buccal incline.

Pleasure’s concept

• 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 (reverse curve) is given at the premolars , no tilt or flat occlusal surface at first molars and a lingual tilt (Monson curve) to second molars.

• 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.

• 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 second molar

area to provide for protrusive balance.

Frush’s concept(1966)

• He advised arranging teeth in a one – dimensional contact relationship,

which should be reshaped during try – in to obtain balanced occlusion.

Intent of this occlusion was to remove occlusal deflective contacts and

provides greater stabilization of dentures.

• Buccal blades of the lower posterior teeth should form a perfect straight

blade. This blade should be perfectly straight to support one-dimensional

contact against the opposing occlusion.

“ Hanau’s laws of articulation ” RUDOLPH L. Hanau

Nine factors governing the articulation are-

• Horizontal condylar guidance • Compensating curve • Protrusive incisal guidance • Plane of orientation • Buccolingual inclination of the tooth axis • Sagittal condylar pathway • Sagittal incisal guidance • Tooth alignment • Relative cusp height

Hanau’s Quint

Trapozzano’s Concept:

According to him – only 3 factors necessary for determining plane of

occlusion

1.Condylar guidance

2.Incisal guidance

3.Cuspal angle

-He stated occlusal plane could be located at various heights to favour

weaker ridge.

-He also stated that by arranging cusped teeth-these curves are produced

automatically

Fig.. A perpendicular constructed from the incisal guide table; (B) a perpendicular constructed from the condylar inclination guide; (A) the point of intersection. Using A as a center,the final level of the occlusal plane may be determined at any level desired, within the inter-ridgespace: I and 2 indicate two such planes. The cuspal angulation of the teeth will, of course,be different at each level selected and still satisfy the requirements for balanced articulation.

Occlusal plane be located exactly as it was when the natural teeth were present.States that:There are 3 fixed factors :1)The orientation of the occlusal plane, the incisal guidance, and the condylar guidance.

2)The angulation of the cusp is more important than the height of the cusp.

3)The compensating curve enables one to increase the effective height of the cusps without changing the form of the teeth.

Bouchers concept

Boucher felt that the compensatory curve is important since it helps in

increasing the effective height of the cusps without changing the form.

Boucher’s disagreed with Trapazzano that the occlusal plane could be

located at various heights to favour a weaker ridge and recommended

that the plane be orientated exactly as when natural teeth were present.

The lott’s Concept He related the laws as follows

• The greater the angle of the condylar path, the greater is the separation

• The greater the angle of the of the overbite, the greater is the separation in the anterior region and the posterior region.

• The greater is separation of the posterior teeth, greater is the compensating curve.

• Posterior separartion beyond the ability of compensating curve to balance the occlusion requires the plane of orientation.

• The greater the separation of the posterior teeth, the greater must be the height of the cusps….

Bernard Levin Concept

• Eliminated plane of orientation.

• Levin has put forth the four factors in the form of a Quad.

The essentials of a Quad are:-

The condylar guidance is fixed & is recorded from the patient.

The incisal guidance is usually obtained from patient’s esthetic & phonetic

requirements. However it can be modified for special requirements.

E.g., the incisal guidance is decreased for flat ridges.

The compensating curve is the most important factor in obtaining

occlusal balance. Monoplane or low cusp teeth must employ the

use of compensating curve.

Cusp teeth have the inclines necessary for balanced occlusion but

nearly always are used with a compensating curve.

FACTORS THAT AFFECT THE

OCCLUSAL BALANCE

Condylar guidance

• Determined purely by the biomechanics of the joint itself, i.e. on bone

contour of T.M.J., muscle of mastication, ligament of T.M.J. and

neuromuscular control of the patient.

• This is the net result of the condyle-disc assembly passing forwards and

downwards, under the influence of the anterior slope of the glenoid fossa.

• Obtained by protrusive registration record.

• It should be recorded and transferred to articulator as closely as possible as

given by the patient.

• Average condylar guidance is about 25-30 degree.

HANAU states that inclination of condylar guidance is definite anatomical

conception.

This path is precise & constant and it guides mandible so precisely that it

is primary dictator of occlusion

KURTH claims that condylar path is not same for varying incisal

guidances.

WEINBERG showed that condylar path varies owing to variable pressures

of function.

Significance

Increase in condylar guidance will increase jaw separation during

protrusion.

In patients with steep condylar guidance, incisal guidance should be

decreased to reduce amount of jaw separation produced during

protrusion

As this factor cannot be modified, all other 4 factors should be modified

to compensate effects of this factor

Incisal guidance

• This is defined as “angle formed by intersection of plane of occlusion

and line with in sagittal plane determined by incisal edges of maxillary

& mandibular central incisors when teeth are in maximum

intercuspation” (GPT-8)

•Angle of incisal guidance is largely under influence of dentist

•This factor is influenced by amount of horizontal, vertical overlap

•Greater horizontal overlap = lesser angle of inclination

•Lesser the vertical overlap = lesser angle of inclination

In complete dentures the incisal guidance should be as flat as possible as

the esthetics and phonetics permits.

If the incisal guidance is steep, it requires steep cusps, a steep occlusal

plane, or a steep compensating curve to affect an occlusal plane

It depends upon following factors:

Phonetic

Esthetic

Shape of residual ridges

Ridge relation

Inter-alveolar distance

On average it is about 10-20 degree.

•Defined as “An imaginary surface which is related anatomically to the

cranium and which theoretically touches the incisal edges of the incisors &

the tips of the occluding surfaces of posterior teeth.

•This plane is assumed to pass through 3 dental landmark central incisal

point and summit of mesio-buccal cusp of last molar on either side.

•It is parallel to Ala- tragus line.

•It is transferred to articulator with help of FACE BOW..

Plane of occlusion or occlusal plane

• The plane of occlusion can be altered to a maximum of 10°.

• Steep increase in inclination of occlusal plane will result in movement of

upper denture backward and lower denture forward during function.

• It represents the mean curvature of the surface. Established anteriorly by

height of lower canine and posteriorly by height of retromolar pad.

(winkler)

Compensating curve

o“The anterioposterior and lateral curvatures in the alignment of the

occluding surfaces and incisal edges of artificial teeth which are used to

develop balanced occlusion”(GPT -8)

oDetermined by inclination of posterior teeth and their vertical relationship

to occlusal plane.

oThe 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.

oSteep condylar path requires steep compensating curve to produce

balanced occlusion.

Lesser compensating curve for the same condylar guidance

steeper incisal guidance (anterior interference) causing loss of

molar balancing contact.

• With compensating curve it is possible to produce eccentric balance in

monoplane occlusal scheme, which is otherwise said to be deficient in

this.

• The compensating curve incorporated in a properly oriented plane of

occlusion starts with the first replacement tooth by raising it at distal

and continuing this initiated curve with further rise in the 2nd molar

with distal surface located at or above the top of retromolar pad.

Anteroposteriorly it should not exceed 20 degree and mediolateraly it should

not exceed 10 degree.

Anteroposterior compensating curves Mediolateral compensating curve

Cuspal Inclination

oIt is an important factor that modify the effect of plane of occlusion & the

compensating curves.

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

oThe 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 to be considered as determinants of balanced occlusion.

Interaction of the five factor Of the four that we can control two of them- o The incisal guidance and the plane of occlusion can be altered only a slight

amount because of esthetic and physiologic factors.

o The important working factors for the dentist to manipulate are the compensating curve and the inclinations of cusp on the occlusal surfaces of the teeth.

Incisal guidance

Condylar guidance

Plane of occlusion

cusps

Compensating curve

Characteristics of balanced occlusion in complete dentures

In centric relation

Anterior teeth- no contact Posterior teeth - multiple, uniform occlusal contacts.

In Protrusive Anterior teeth:

Maxillary & mandibular teeth contact.

Posterior teeth Semi-anatomic/ anatomic-

Multiple posterior buccal cusp to buccal cusp & lingual cusp to lingual cusp contacts between maxillary & mandibular teeth.

Posterior teeth Flat plane, neutrocentric, monoplane

2nd molar contact if increased compensating curve Balancing ramp contacts if maintain true flat plane.

If no curve or ramp & have incisal vertical overlap, can’t balance in protrusive.

In lateral excursion Working side

Anterior teeth:

Maxillary & mandibular anterior teeth contact on the working side.

The buccal & lingual cusps of the maxillary & mandibular posterior teeth are in

contact.

If lingualized occlusion, the maxillary lingual cusp will be in contact with the

mandibular lingual cusp.

Posterior teeth

In lateral excursionBalancing side

Anterior teeth

o The maxillary & mandibular anterior teeth may contact on the

balancing side.

Posterior teeth

o The lingual cusps of the maxillary teeth will be in contact with the

buccal cusps of the mandibular teeth.

o Monoplane balanced occlusion, usually only the second molars are in

contact or the balancing ramp.

Contacts in balanced occlusion Working side

o The mandibular buccal cusp ridges makes articular contact with the maxillary

buccal cusp ridges as the mandibular lingual cusp ridges are making contacts

with the maxillary lingual cusp ridges.

Balancing side:

The mandibular buccal cusps & their occlusal facing ridge, contacts

maxillary lingual cusps & ridge.

LUB- Lingual incline of Upper Buccal cuspBLL- Buccal incline of Lower Lingual cusp

BULL- Buccal incline of Upper lingual cuspLLB- Lingual inclines of Lower Buccal cusp

RIGHT LEFT

Protrusion:

Incisal edges of the mandibular anterior teeth contact with the lingual

surface of the maxillary anterior teeth. The mesiobuccal & lingual

cusp ridges of the mandibular teeth contact the distobuccal & lingual

cusp ridges of the maxillary teeth.

Steps

Tracer attachment

Programming of articulator

Teeth arrangement

Try-In

Selective grinding

Selective grinding is defined as the, “intentional alteration of the occlusal surfaces of the teeth to change their form’’ – GPT 8

Rational :

oEliminate occlusal interferences oAchieve balanced occlusion oContacts in harmony with TMJ and neuromuscular system

Avoiding remounting the dentures on articulator and selective grinding leads to,1) A deformation of underlying soft tissues,2) Discomfort, and3) Destruction of the underlying supporting bone. Later occlusal errors may be concealed and impossible to locate and correct because of distorted and swollen tissues.

Eliminate interlocking transverse ridges Functional cusp not subjected to selective grindingLower buccal cusp inclines can be reduced but not the cuspMaxillary buccal cusp out of contact during centric occlusion and eccentric positions.

“BULL’s Principle”

If interferences exists in the working side reduce either the upper buccal cusps or the lower lingual cusps.

In anterior teeth, lingual of upper and labial surface of lower teeth is grinded to eliminate any interference.

Final result should be smooth gliding lateral excursion with working and balancing contacts.

The multiple contacts should be smooth, uniform and in harmony with the TMJ’s and the neuro-muscular activity.

Principles :

Steps at which grinding is performed:

1) At the time of teeth arrangement

2) Lab remount procedures

3) Clinical remount procedures

Methods of detecting errors Articulating paper

Carbon paper

Wax template

Selective grinding for centric contactsCorrecting for maximum intercuspation

Discrepancies in static relationship due to minor processing errors.Four types:

1) Mesio- distal discrepancy

2) Bucco- lingual discrepancy-

a) Cusps appear to be too longb) Insufficient overjetc) Overbite too long.

1. Mesio- distal discrepancy

o Due to interferences between – mesial slopes of upper cusps & the distal slopes of lower cusps.

2. Cusps appear to be long

o Cusps appear to be only ones contacting.o If it is supporting cusps ,the opposing fossae are

depened untill an appropriate cusp fossa relationship is obtained.

3. Insufficient overjet

In Posterior teeth- seeming to be contacting end-to-end.

The interfering slopes must be adjusted

- Buccal cusps- effectively moved inward.

- Palatal cusps- moved outwards.

The central fossae are widened & the cusps appear narrower.

4. Overjet too large

Uppers appearing to be too far buccal to the lowers.

Length of the cusps must not be reduced.

Move the upper cusps inwards & lower cusps outward.

Widening of the central fossae & narrowing of the offending cusps.

Correction for lateral excursive movements

When the mandible moves laterally, the aim is to have contact on all working side as well as nonworking side cusp slopes.

1.Working side interferences:•Due to either:

• Buccal cusp or• Lingual & palatal cusp contacting preventing any contact

on nonworking side.

The adjustment is made on the upper buccal cusp, from the central fossa to the cusp tip.The adjustment is made on the non- supporting cusp.

2. Nonworking side interferences

Between the upper palatal cusp inclines and the inclines of the lower buccal cusps.

Both these cusps are supporting cusps, so great care must be taken to preserve as much of the cusp as possible.

Therefore only the parts of inclines causing the interference are adjusted, & their relationship in maximum intercuspation constantly checked.

If it appears that cusp height must be changed, it is preferable to preserve the upper palatal cusp.

Corrections for protrusive movements

1. Anterior interference :

-too great overbite

-insufficient compensating curvature to the occlusal plane.

o Inciso- labial surfaces of the lowers are adjusted.

2. Posterior interference:

- No contact at the anteriors, or- Few contacts posteriorly.

The offeding inclines must be adjusted- the distal inclines of upper cusps.- the mesial inclines of the lower cusps.

The Retrognathic Mandible

Class II division 1 cases

1. If the overjet is not too great:

- there will be contact between the anteriors during protrusion.

2. If the overjet is too great

- there will be no contact.

Contact can be created on the palate of the denture.

Lingualised articulation

LINGUALISED ARTICULATION

• GYSI in 1927 introduced this type of concept.

• POUND used it for non balanced articulation.

• PAYNE in 1941 used it for balance articulation.

• Lingualised occlusion can be used in most denture combinations.

• It is particularly helpful when the patient places high priority on esthetics but non-anatomic occlusal scheme is indicated by oral conditions such as severe alveolar resorption, a Class II jaw relationship, or displaceable supporting tissue.

• If the non-anatomic occlusal scheme is used, esthetics in the premolar region are compromised.

• With Lingualised occlusion, the esthetic result is greatly improved while still maintaining the advantages of a non-anatomic system.

• Lingualised occlusion also can be used effectively when a complete denture opposes a removable partial denture.

Indications

• Anatomic posterior (30 or 33°) teeth are used for the maxillary denture. Tooth

forms with prominent lingual cusps are helpful.

• Non-anatomic or semi-anatomic (20 or 0 degree) teeth are used for the

mandibular denture. Either a shallow or flat cusp form is used. A narrow

occlusal table is preferred wherever resorption of the residual ridges has

occurred.

• Modification of the mandibular posterior teeth is accomplished by selective

grinding which is always necessary regardless of specific tooth or material.

Principles of Lingualised articulation

• Maxillary lingual cusps should contact mandibular teeth in centric occlusion.

• Balancing and working contacts should occur only on the maxillary lingual

cusps.

• Protrusive balancing contacts should occur only between the maxillary lingual

cusps and the lower teeth.

o Most of the advantages attributed to both

the anatomic and non-anatomic forms are

retained.

o Cusp form is more natural in appearance

compared to non-anatomic tooth form.

o Good penetration of the food bolus is

possible.

o Bilateral mechanical balanced occlusion is

readily obtained for a region around

centric relation.

o Vertical forces are centralized on the

mandibular teeth.

Advantages of Lingualised articulation

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Figure : Centric occlusion in a lingualised articulation. The upper palatal cusps contact the central fossae of their opposing mandibular teeth, and the buccal cusps have been adjusted to just raise them sufficiently so that they do not take part in the articulation.

Centric occlusion

Lateral excursion

Protrusive movement

Retrognathic jaw relationship

o Functionally, skeletal Class II individuals have an extensive range of

motion of the mandible.

o The problem is that the patient functions in a variety of positions

anterior to centric relation position,

o They function closest to centric relation position when chewing food

requiring more force, but function forwards of this position at rest (to help

lip closure and to improve appearance), and when speaking.

o Protrusive balance is very difficult with cusped teeth.With a lingualised concept, however, the occlusal tables of each tooth can

be successively recruited to maintain contact during protrusion, and a

long anteroposterior area of contact can be obtained.

Prognathic jaw relationships

o The main problem with posterior tooth placement in these cases, is that

of a medio-lateral arch discrepancy and the need for a cross-bite

arrangement.

o In this case, the lingualised concept becomes a “buccalised” one: the

upper buccal cusps are now adjusted to contact the lower occlusal

surfaces, and the upper palatal cusps are ground so as not to take part in

the articulation.

Practical considerations

A study comparing patient responses to a lingualised scheme

using 30 upper posteriors to a monoplane scheme.

A statistically significant no. of patients (67%) preferred the

lingualised scheme, because they “chewed better”.

It would seem that 30 or 33 cusp angle teeth enhanced the

effective “pestle” effect of the scheme.

Summary

The nature of the supporting structures for the complete dentures and the forces directed to them by the occlusion creates a special biomechanical problem.

Balanced occlusion is one of the most important factors which will favor the stability of the base; and help in preservation of the supporting structures by reducing the lateral forces.

“ Thereby signifying its importance in complete denture fabrication.”

References:ESSENTIALS OF COMPLETE DENTURE PROSTHODOTICS , SECOND EDITION, by Sheldon WinklerBOUCHER’S PROSTHODONTIC TREATMENT FOR EDENTULOUS PATIENTS, ELEVENTH EDITION, by hickey , zarb and bolenderTrappozano V.R.: An experimental study of the testing of occlusal patterns on the same denture bases. JPD.;1952; 440-457.

Arthur N.: Balancing ramps in non-anatomic complete denture occlusion. JPD,1985;53:431-433.

Beck H.O.: Occlusion as related to complete removable prosthodontics. JPD,1972;27:246-256.

Becker C.M., Swoop P.C.: Lingualised occlusion for removable prosthodontics.JPD,1977;38:601-608.

Bernard Levin: Reevaluation of Hanaus Laws of Articulation and the Hanaus Quint. JPD,1978;39:254-258.

Heartwell Charles M.: Sylabbus of complete dentures.

Kydd W.L.: Comlete denture base deformation with varied occlusal tooth form. JPD., 1959;6:714-718.

Kurth L.E.: Balanced Occlusion. JPD’1954’4:150-167.

Trappozano V.R.: An experimental study of the testing of occlusal patterns on the same denture bases. JPD.;1952; 440-457.

Owen C P. Occlusion in complete denture.

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