Force directed should be along the long axis of the tooth.

• Most normal chewing stays within the red area, but the lower teeth have the range of the black line.

• Lower teeth are guided by a gentle slanted slope of the upper lingual surfaces.

5. In an upright posture, posterior tooth contact more heavily than do anterior teeth.

Concepts of occlusion in natural dentition The collective arrangement of the teeth in function is quite important. There are three recognized concepts that describe the manner in which

teeth should and should not contact in the various functional and excursive position of the mandible they are bilateral balanced occlusion, unilateral balanced occlusion and mutually protected occlusion.

• These three concepts based on some early concepts (bonwill, spee, monsoon,hall), gnathology (mccollum, page, lauritzen, beyron, stuart & stallard, guichet, dawson, schuyler, gerber, pms concept)

• 1) Bilateral balanced occlusion :- Based on work of von spee and monson Prosthodontic concept which dictates that a maximum number of teeth should

contact in all excursive positions of the mandible. When concept was applied to natural teeth in complete occlusal rehabilitation, multiple tooth contacts that occurred as the mandible moved through its various excursions, there was excessive frictional wear on the teeth.

Not used now a days for natural teeth. Useful in complete denture construction.

2) Unilateral balanced occlusion Commonly known as Group function occlusion Widely accepted and useful method of tooth arrangement in restorative dental

procedures today Concept had origin in the work of Schuyler, who began to observe the destructive

nature of tooth contact on non working side and concluded it would best to eliminate all tooth contact on the non working side.

Group function occlusion calls for all teeth on working side to be in contact during a lateral excursion.

The absence of contact on non working side prevent those teeth from being subjected to the destructive, obliquely directed forces found in nonworking interferences.

It also saves the centric holding cusps from excessive wear. The obvious advantage is the maintenance of the occlusion.

The functionally generated path technique, originally described by mayer is used for producing restoration in unilateral balanced occlusion.

It has been adapted by Mann and Pankey for use in comlete-mouth occlusal reconstruction.

3)Mutually protected occlusion

• It had its origin in the work of D’Amico, Stuart , Lucia and the members of the gnathological Society they observed that in many mouths with a healthy periodontium and minimum wear, the teeth were arranged so that the overlap of the anterior teeth prevented the posterior teeth from making any contact on either the working or the non working sides during mandibular excursions.

• This separation from occlusion was termed disocclusion. According to this concept of occlusion, the anterior teeth bear all the load and the posterior teeth are disoccluded in any excursive position of the mandible.

• The desired result is an absence of frictional wear and anterior teeth protecting the posterior teeth

in all mandibular excursion and posterior teeth protecting the anterior teeth at the intercuspal position.

• If same disocclusion occur in all excursive movement and contact occur only on canine then mutually protected occlusion known as canine protected/guided occlusion.

• This arrangement of the occlusion is probably the most widely accepted because of its ease of fabrication and greater tolerance by patients.

• Conditions of using mutually/canine protected occlusion:-

All anterior teeth/canine should be healthy with normal class-1 relationship.

In presence of ant. Bone loss or missing canines the mouth should be restored to group function.

In either angle class-2 or class-3 occlusion mandible can-not be guided by the anterior teeth.

A mutually protected occlusion also can-not be used in a situation of reverse occlusion, or cross bite in which maxillary and mandibular buccal cusps interfere with each other in a working side excursion.

RAMFJORD AND ASH CONCEPTS OF OCCLUSION

Equilibrium between the different components of masticatory system.

According to RAMFJORD & ASH an occlusion should be evaluated more by the way it influenced the function of the stomatognathic system than by the way the teeth intercuspid

The occlusal concept applied should promote occlusal stability, does not exceed the needs and finances of most persons, is controlled by general clinician and does not need a specialized laboratory technician.

FREEDOM IN CENTRICPosselt was firstCriteria are to attempt to eliminate the need for neuromuscular adaptation.According to this concept, Maximum intercuspation and centric relation are coincident but flat areas on the depth of the fossae, on which opposing cusps occlude, will allow for a certain degree of freedom in both centric and eccentric movements without the guiding influences of occlusal inclines.Vertical dimension of occlusion in maximum intercuspation and centric relation might be the same when all the interferences for closing in centric relation are eliminated.

controlling factors/Anatomic determinants of occlusion

• The occlusal anatomy of the teeth must function in harmony with the structures controlling the movement patterns of the mandible.

• To maintain harmony of the occlusal condition, the posterior teeth must pass close to but must not contact their opposing teeth during mandibular movement

Posterior controlling factorsTwo TMJ’s –posterior controlling factors

Fixed factorsThe angle at which the condyle moves away from horizontal reference plane is referred to as the condylar guidance angle.

Anterior controlling factorsVertical overlap and horizontal overlapVariable factor (altered by dental procedures)

Understanding the controlling factorsIf the criteria for optimum functional occlusion has to be fulfilled, the morphologic characteristics of each posterior tooth must be in harmony with those of its opposing tooth or teeth during all eccentric mandibular movements.The relationship of a posterior tooth to the controlling factors influences the precise movement of that tooth.

•The dentist has no control over posterior determinants while dentist have direct control over the tooth determinant by orthodontic movement of teeth; restoration of the anterior lingual or posterior occlusal surfaces; and equilibration, or selective grinding, of any teeth that are not in a harmonious relationship.

•Intercuspal position and anterior guidance can be altered, for better or for worse, by any of these means.

•Therefore, the significance of the anterior and condylar guidances lies in how they influence posterior tooth shape.

The closer a tooth is located to a determinant, the more that it will be influenced by that determinant . A tooth placed near the anterior region will be influenced greatly by anterior guidance and less by the TM joint. A tooth in the posterior region will be influenced partially by the joints and partially by the anterior guidance.

Occlusal surface of the posterior teeth can be affected in 2 manners

1. Height

2. Width Factors that influence the heights of cusps and depths of fossae are

the vertical determinants of the occlusal morphology Factors that influence the direction of ridges and grooves on the

occlusal surfaces are considered the horizontal determinants of the occlusal morphology.

Vertical determinants of occlusal morphology (on cusp height)

a) Effect of condylar guidance b) Effect of anterior guidance

c) Effect of plane of occlusion

d) Effect of curve of Spee

e) Effect of mandibular lateral translation movement

a) Effect of condylar guidanceThe inclination of the condylar path during protrusive movement can vary from steep to shallow in different Patients. If the protrusive inclination is steep, the cusp height maybe longer.

b) Effect of anterior guidanceIt is a function of the relationship between the maxillary & mandibular anterior teeth.•The track of the incisal edges from maximum intercuspation to edge-to-edge occlusion is termed the protrusive incisal path. The angle formed by the protrusive incisal path and the horizontal reference plane is the protrusive incisal path inclination.In a healthy occlusion, the anterior guidance is approximately 5 to 10 degrees steeper than the condylar path in the sagittal plane. Therefore, when the mandible moves protrusively, the anterior teeth guide the mandible downward to create disocclusion, or separation, between the maxillary and mandibular posterior teeth. The same phenomenon should occur during lateral mandibular excursions.The lingual surface of a maxillary anterior tooth has both a concave aspect and a convexity, or cingulum. The mandibular incisal edges should contact the maxillary lingual surfaces at the transition from the concavity to the convexity in the centric relation position.

Anterior guidance, which is linked to the combination of vertical and horizontal overlap of the anterior teeth, can affect occlusal surface morphology of the posterior teeth.The greater the vertical overlap of the anterior teeth, the longer the posterior cusp height may be. The greater the horizontal overlap of the anterior teeth, the shorter the cusp heightmust be.

c) Effect of plane of occlusionIt is an imaginary line extending from cusp tip of mandibular canine to distobuccal cusp of lower second molarRelationship of this plane to the angle of articular eminence influences the steepness of the cusps.

As the plane of occlusion becomes more nearly parallel to the angle of the articular eminence, the posterior cusps must be made shorter..

d) Effect of curve of Spee3 components affecting the cusp height are:

a) Length of the radius of the curve

b) Degree of curvature of the curve of Spee

c) Orientation of curve of Spee

Length of the radius of the curve

Degree of curvature of the curve of Spee

Orientation of curve of Spee

e) Effect of mandibular lateral translation movement

Bennett movement- A bodily side shift of the mandible that occurs during lateral movements.

The degree of medial movement of orbiting condyle depends on two factors :

a. Morphology of medial wall of the fossa.b. Inner horizontal portion of the Temporomandibular ligament (which attaches to

the lateral pole of the rotating condyle)

Lateral translation movement has 3 attributes

1. Amount

2. Direction

3. Timing Amount and Timing are dependent on medial wall of fossa and TM

ligament. Direction depends on the direction taken by the rotating condyle.

Effect of amount of lateral translation movement on cusp height

Greater the amount of lateral translation movement, shorter is the posterior cusp

Effect of the direction of lateral translation movement on cusp heightThe movement occurs within a 60 degree cone whose apex is located at the axis of rotation.

More superior the direction of movement shorter should be the cusp height.

Effect of timing of lateral translation movement on cusp heightDependent on the medial wall of fossa and TM ligament.Immediate side shift – when the lateral translation movement occurs earlyProgressive side shift – if movement occurs in conjunction with an eccentric movement

More is the Immediate side shift shorter should be the cusp height.

Horizontal determinants of occlusal morphology

Influences the direction of ridges and grooves on the occlusal surfaces.Each centric cusp tip generates both laterotrusive and mediotrusive pathways across its opposing tooth. (working and balancing grooves)Each pathway represents a portion of the arc formed by the cusp rotating around the rotating condyle.

Horizontal determinants of occlusal morphology (on ridge and groove direction)

a) Effect of distance from rotating condyle

b) Effect of distance from mid-Sagittal plane

c) Effect of distance from rotating condyle and from mid-Sagittal plane

d) Effect of mandibular lateral translation movement

e) Effect of inter-condylar distance

a) Effect of distance from rotating condyle

Greater the distance – wider the angle b/w working and balancing grooves

b) Effect of distance from mid-Sagittal plane

More the distance – wider the angle b/w working and balancing grooves

c) Effect of distance from rotating condyle and from mid-Sagittal plane

The combination of the two positional relationships is what determines the exact pathways of the centric cusp tips

Because of the curvature of the dental arch; as the distance of tooth from rotating condyle increases – distance from midsagittal plane decreases, but distance from rotating condyles increases FASTER than decrease in distance from midsagittal plane.

Therefore, the teeth toward the anterior region (e.g. premolars) have larger angles than posterior teeth (e.g. molars).

d) Effect of mandibular lateral translation movement

influences the directions of ridges and grooves

Movement depends on 2 factors:

1. Amount

2. Direction

Effect of amount of lateral translation movement on ridge and groove direction

Effect of direction of lateral translation movement on ridge and

groove direction

e) Effect of inter-condylar distance As inter condylar distance increases – distance between the condyle and

the tooth increases – wider angles

Factor Condition Effect Condylar guidance Steeper Taller

Anterior guidance More overbiteMore Overjet

Taller Shorter

Plane of occlusion More parallel Shorter

Curve of Spee More acute Shorter

Lateral translation Greater movementMore superior Greater immediate shift

Shorter ShorterShorter

Distance from rotating condyle

Greater Wider the angle

Distance from midsagittal plane

Greater Wider the angle

Lateral translation Greater Wider the angle

Intercondylar distance Greater Smaller the angle

NEUTROCENTRIC OCCLUSION• It was developed by DeVan and he stated that the teeth must be placed where they grew as long as the

mechanical laws are not violated.

• DeVan has suggested to two key objectives of his occlusal scheme-

neutralization of inclines

centralization of forces.

• The five elements of this scheme were :-

DIFFERENT SCHEMES OF OCCLUSION

1) Position

DeVan positioned the posterior teeth over the posterior residual

ridge as far as lingually as the tongue would allow, so that the forces

would be perpendicular to the support areas. He felt this was the

most important factor and that “Off ridge” contact for the purpose of

balance created more problems that they sloved.

2)Proportion

• DeVan reduced tooth width 40% to correct tooth proportion such a narrowing

supposedly reduced vertical stress on the ridge by narrowing the occlusal table.

• In addition, horizontal stress was reduced because friction between opposing surfaces

was decreased.

• Forces were centralized without encroachment on the tongue space.

3)Pitch

•This is the inclination or tilt of the occlusal plane. • It is oriented parallel to the underlying ridge and midway between them. •This directed the forces perpendicular to the mean osseous foundation plane. •Patients are trained not to protrude and incise.

4)Form• Tooth form was corrected by using flat teeth with no deflecting inclines.• This arrangement reduced destructive lateral forces and helped to keep masticatory

forces perpendicular to the support.• All contacts were in a single plane with no projections above or below the plane to

interfere with the mandibular movements.

5)Number • The posterior tooth were reduced in number form eight to six. •This decreased the magnitude of the occlusal force and centralized it to the second premolar and first molar area.

Attributes of Neutrocentric concept- a). Non-anatomic teeth b). Plane of occlusion parallel to the residual ridge. c).No compensating curves, teeth are set flat d). Maxillary & mandibular teeth arranged without any vertical overlap. e).Narrow teeth selected to decrease occlusal forces.

Advantages of Neutrocentric occlusion

1.This technique is simple and requires less precise records.

2.Suitable for a patient who have resorbed friable ridges with mobile tissue in whom it may be

difficult or impossible to make precise records which could be duplicated.

3. By removing inclines the lateral forces which are destructive to the residual ridges are reduced

4. Teeth set with a neutrocentric occlusal scheme are easier to adjust.

5. Because the neutrocentric technique provides an area of closure and does not lock the

mandible into a single position the geriatric patient with limited oral dexterity is an ideal

candidate. Also the centric occlusion – centric relation discrepancy introduced by the denture

settling would tend to be less destructive because of the unlocked nature of the occlusion.

6. Neutrocentric occlusion is especially good in class II (retrognathic) class III (prognathic) and cross bite

cases. In geriatric patient with resorbed ridges the chances for arch relationship discrepancies are

increased, therefore greater horizontal overlap and lack of specific interdigitation make

neutrocentric occlusion ideal.

Disadvantages of neutrocentric occlusion1. The greatest criticism of this occlusal scheme is that it is the least esthetic of the five basic occlusal schemes. In that

there is no incisal overlap and no posterior cusps certainly make the statement true.

2. A strong criticism of the neutrocentric occlusion is that moving the teeth lingually and altering their vertical position

may not be compatible with the tongue, lip and cheek function.

3. The flat nature of teeth used in neutrocentric occlusion impair mastication because of poor

bolus penetration. As a result vertical forces on the ridge are increased, patients comment that the

teeth “feel dull”.

4. While vertical forces are more acceptable to the residual ridges that horizontal forces, there is

a limit beyond which base movement and discomfort occurs.

5. Patients with class III tend to hold there jaws forward and to function forward of the centric relation.

They continue to do so regardless of the dentist efforts at patient education. The result is disclusion of the

posterior teeth due to Christensen’s phenomenon and continued soreness in the anterior area of the mouth

because forces are not being placed perpendicular to their support area, these patients then require some

form of anterior-posterior compensating curve to increase their comfort.

6. This flat type of occlusion cannot be balanced and the lack of cusp height encourages a lateral

component to the chewing cycle which can lead to bruxism, ridge soreness and possible TMJ problems.

• Semi anatomic occlusion (teeth with a cuspal inclination of less than 300 in full balance)

represents an effort by the anatomic school to overcome some of the problems and

criticisms of anatomic occlusion.

• Its is a compromise by those who desire cusps for esthetics chewing efficiency and balance

and yet still desire to decrease the lateral force component introduced by the cusp inclines.

SEMI ANATOMIC OCCLUSION

In 1952, Schuyler pointed out that functional harmony can be achieved with shallow cusp teeth by reducing the incisal guidance. The advantage and disadvantage of semianatomic occlusion are basically the same as for anatomic occlusion.

Esthetics is not compromised , to a degree by decreasing the incisal guidance, but the advantage of reduced lateral forces seems to make this a worthwhile compromise.

• Non anatomic( zero degree. Non cusp) teeth with a compensating curve to provide some degree of protrusive and lateral balance is widely accepted occlusal scheme.

• In this scheme tooth inclines are eliminated and balance is produced by combination of anterior-posterior and lateral curves or by the use of a balancing ramp leading to three point balance.

NON ANATOMIC / MONOPLANE OCCLUSION

• The maxillary and mandibular teeth are arranged without any vertical overlap. The amount of horizontal overlap is determined by the jaw relationships.

• Jones advocated monoplane articulation in 1972. In this concept, a non-anatomic occlusal scheme is used with a few specific modifications.

•The posterior teeth are positioned on a flat plane. The anterior teeth are positioned with a horizontal and vertical overlap, and the emphasis in tooth arrangement is to establish maximal tooth contact in the centric jaw relation position.

Advantages of Non Anatomic Occlusion Its is more esthetic than neutrocentric occlusion because some

degree of vertical overlap is allowed by the presence of posterior compensating curves.

This occlusal scheme is simple and less time consuming then others.

This occlusal scheme good for patients with cross bite or class III relationship and especially for patients with sever class II relationship who have an extremely long functional path and who tend to hold their jaws forward and to function in that position.

The presence of the compensating curve allows these patients to hold their jaws anywhere and still maintain posterior contacts over the areas where occlusal forces can be resisted.

LINGUALISED OCCLUSION• First proposed by Alfred Gysi in 1927.• 1941 Payne desired a modification of anatomic teeth.• Involves the use of a large upper palatal cusp against a wide lower central

fossa.• Buccal cusps of upper & lower teeth do not contact each other.

• It is an attempt to maintain the esthetic and food penetration advantages of the anatomic form while maintaining the mechanical freedom of the non-anatomic form.

• PRINCIPLES:• Anatomic posterior teeth are used for maxillary denture.• Non-anatomic or semi anatomic teeth are used for mandibular

denture.• Modification of mandibular posterior teeth is accomplished by

selective grinding and creating a slight concavity in the occlusal surface.

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

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

• Protrusive balancing contacts should occur only between maxillary lingual cusps and lower teeth.

ADVANTAGES• 1. The lingual cusp of the maxillary tooth in a lingulaised

occlusion penetrates the bolus of food like a cleaver on a butcher’s block and then operates on the bolus in a holding and grinding fashion similar to the mortar and pestle mechanism.

• 2. There is a reduction of damaging lateral forces.• 3. It allows easier accommodation to unpredictable basal seat

changes since it provides for an area of closure.• 4. Vertical forces are centralized on the mandibular teeth.• 5. The maxillary buccal cusps play no functional role in occlusion

and only improve the esthetic appearance and prevent cheek biting.

• 6. It is a simple and flexible concept and can be applied in virtually any type of removable prosthodontics as it incorporates most of the advantages while eliminating or neutralizing many of the disadvantages of other occlusal schemes.

LINEAR OCCLUSION• It is defined as “The occlusal arrangement of artificial

teeth, as viewed in the horizontal plane, where in the masticatory surfaces of the mandibular posterior artificial teeth have a straight, long, narrow occlusal form resembling that of a line, usually articulating with the opposing monoplane teeth.”

• Literature has supported the use of linear (also known as lineal) occlusion to enhance the stability of the complete denture prosthesis. Noninterceptive occlusion (linear occlusion) requires that there should be no interference or interception with the mandibular movement in protrusive or lateral excursions.

FUNCTIONALLY GENERATED OCCLUSION

In this occlusion scheme, the maxillary teeth carve out a path in the wax placed on the lower occlusal table. This is known as ‘functionally generated path’. Later the wax containing this path is replaced with cast gold or Cobalt alloy.

Used in amalgam inserts, cast gold occlusal.

• The essential starting point for understanding of occlusion is a through knowledge of the anatomy, physiology & biomechanics of the TMJ, TEETH & their relationship to the stomatognathic system.

• “The controversy about occlusion cannot be resolved for three reasons: (1) much knowledge is based upon empirical rather than scientific information. (2) the tolerance of the oral organ or the upper and lower physiologic limits are so

broad that because a certain concept failed in one specific mouth, it does not mean that it would fail in all mouths.

(3) the tremendous variable factor of the individual dentist and the standards by which he evaluates his completed restorations.”

The knowledge, judgment, understanding, and skill of each dentist is more important in treating patients than the technique or concept of occlusion to which he subscribes.

since there is no one answer to occlusal problems, the dentist should use the philosophy that works best in his own hands and at the same time does the most good, or better yet, the least harm to the patient.”

CONCLUSION

REFERENCES

1.Dental Anatomy Physiology & Occlusion - (7th Edition) WHEELERS 2.Evalution,Diagnosis & Treatment of Occlusal Problems (2nd

Edition )PETER E. DAWSON3. Occlusion (3rd Edition) RAMFJORD.S & ASH 4. Bhalaji (3rd Edition)5. Okeson JP. (4th Edition) Management of

Temporomandibular Disorders and Occlusion, 6. Shillingburg HT. (3rd Edition)Fundamentals of Fixed

Prosthodontics 7. Syllabus of complete dentures Heartwell 4th Edition8. Essentials of complete denture prosthodontics Winkler 2nd Edition

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RAVI GOYAL