TRIPASS XR تري باس

 • When teeth are arranged on the plane, these are not inclined to form

compensatory curves.

• In the mediolateral direction, the tooth is set flat with no medial or

lateral inclination.

• Thus, this concept of occlusion eliminates any anteroposterior or

mediolateral inclines of the teeth and directs the forces of occlusion

to the posterior teeth.

• The patient is instructed not to bite with the anterior teeth.

• Monoplane or cuspless posterior teeth are used in this type of

occlusion.

• Because of this, there is no projection above or below the occlusal

plane.

• The horizontal and lateral condylar guidances of the articulator are

programmed to ‘zero’.

• To direct force towards the centre of the support and to reduce the

functional forces, the buccolingual width of the teeth and the

number of teeth are also reduced.

FIGURE 8-8 Teeth arranged in neutrocentric occlusion.

Factors influencing neutrocentric occlusion are:

• Skeletal relationship of the jaws.

• Influence of somatic nervous system to control muscle movement

and proprioception.

• Accuracy of the denture bases.

• Stable position of the condyles in the glenoid fossa.

Advantages

• It is more adaptable to unusual jaw relation such as class II and class

III jaw relationships.

• It can be used with crossbite relations.

• It provides freedom in occlusion.

• It is useful in cases of poor ridges.

• It is a simplified and less time-taking technique.

Disadvantages

• It results in poor aesthetics.

• It results in decreased masticatory efficiency.

• It results in decreased denture stability during eccentric movements.

• It is difficult to obtain balanced occlusion.

Spherical occlusion

Definition

Spherical occlusion is defined as ‘an arrangement of teeth that places their

occlusal surfaces on the surface of an imaginary sphere (usually 8 inches in

diameter) with its centre above the level of the teeth’. (GPT 4th Ed)

• Spherical theory of occlusion was introduced by G.S. Monson (1918).

• This concept of occlusion was based on observations of the natural

teeth by German anatomist von Spee.

• Hagman balancer and one phase of the Pankey–Mann occlusal

reconstruction technique were based on the spherical theory of

occlusion.

• According to this concept, the anteroposterior and mesiodistal

inclines of the artificial teeth should be arranged in harmony with a

spherical surface.

• The spherical theory of occlusion proposed that lower teeth move

over the surface of upper teeth as over a surface of sphere with a

diameter of 8 inches.

• The centre of sphere was located in the region of glabella.

• The surface of the sphere passed through the glenoid fossa and

along with the articulating eminences.

Limitations

• Articulators based on this theory do not have provisions for

variations in inclinations for condylar paths.

• It cannot be used in all patients due to variation in the paths of jaw

movements.

Balanced occlusion

Definition

Balanced occlusion is defined as ‘the bilateral, simultaneous, anterior, and

posterior occlusal contact of teeth in centric and eccentric positions’. (GPT

8th Ed)

Or

‘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 the normal range of mandibular

function’. (Winkler)

Goals of balanced occlusion

• Maximal bilateral, simultaneous contact in centric positions.

• Working contacts are present all along the working side from the

canine posteriorly.

• Balancing contact in protrusive position in the molar region. Slight

variation in angulation can result in this contact.

• Balancing in the molar region in lateral position.

• Occlusal plane of the completed set up parallel to the maxillary and

mandibular residual ridges.

Factors which aid in achieving balanced occlusion are described as

follows:

Factors of protrusive balance

• The inclination of the condylar path.

• Angle of the incisal guidance chosen for the patient.

• Inclination of the plane of occlusion.

• The compensating curves chosen for orientation with the condylar

path and incisal guidance.

• Cuspal height and inclination of the posterior teeth.

Factors of lateral balance

• Inclination of the condylar path on the nonworking side.

• Inclination of the incisal guidance and cuspid lift.

• Inclination of the plane of occlusion on the balancing or nonworking

and the working side.

• Compensating curve on the balancing and the working side.

• The buccal cusp heights or inclination of teeth on the balancing side.

• The lingual cusp heights or inclination of teeth on the working side.

• The Bennett side shift on the working side.

Requirements for balanced occlusion

• All the teeth of the working side (canine to second molar) should

glide evenly against the opposing teeth.

• No single tooth should produce any interference or dislocation of

other teeth.

• There should be contact in the balancing side, but they should not

interfere with the smooth gliding movements of the working side.

• There should be simultaneous contact during protrusion.

Advantages

• Balanced occlusion is one of the most important factors that affect

the denture stability. Absence of occlusal balance will result in

leverage forces which destabilize the denture during mandibular

movement.

• Bilateral balanced occlusion provides contact during the terminal

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

chewing.

• Balanced occlusion aids during swallowing as it allows even

bilateral contact.

• It helps in preventing the destructive lateral forces generated during

parafunctional habits such as bruxism to be transmitted to the

supporting tissues.

• It provides stability, retention and comfort.

• Dentures which are not balanced tend to move during function, this

movement or shifting of the denture base tends to abuse the

supporting tissues.

Types of Balanced Occlusion

(i) Unilateral occlusal balance

(ii) Bilateral occlusal balance

(iii) Protrusive occlusal balance

(iv) Lateral occlusal balance

Unilateral occlusal balance

• This type of occlusion has all the teeth contacting on the working

side and with no contact on the balancing side.

• This type of occlusion is not advised in complete denture fabrication

but can be used in fixed partial dentures.

Bilateral occlusal balance

• This occurs when there is bilateral simultaneous contact of the teeth in

centric and eccentric movements.

• In this, minimum of three contacts are needed to establish a plane of

equilibrium.

• This type of balance is dependent on the interaction of condylar

inclination, incisal guidance, plane of occlusion, height of the cusp

and teeth angulation.

• This type of occlusion is the most desired one in complete denture

fabrication.

• It enhances the denture stability in centric and eccentric movements.

Protrusive occlusal balance

• During protrusion of the mandible, there is simultaneous and

bilateral contact in the posterior and anterior teeth.

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

posterior teeth and one on the anterior teeth.

• This type of balance also depends on the interaction of factors

similar to the bilateral balance (Fig. 8-9).

FIGURE 8-9 Teeth contact during protrusive balance.

Lateral occlusal balance

• There is a simultaneous contact on the working and balancing side

on lateral movements.

• Minimum three-point contact is needed.

• Greater the number of teeth contacting, greater will be the balance.

• It is desirable in complete dentures to enhance stability.

Concepts of balanced occlusion

Gysi’s concept (1914)

• A. Gysi first proposed the concept of balanced occlusion in 1914.

• He suggested that 33° anatomic teeth can be arranged under various

movements of the articulator to enhance the stability of the denture.

French’s concept (1954)

• F.H. French (1954) used modified French teeth to obtain balanced

occlusion.

• He suggested lowering of the lower occlusal plane to enhance

stability of the dentures along with balanced occlusion.

• He arranged the upper first premolars with 5° angulation, upper

second premolars with 10° angulation and upper molars with 15°

angulation.

Sear’s concept (1949)

• He introduced the balanced occlusion for nonanatomic teeth using

posterior balancing ramps or an occlusal plane which curves

anteroposteriorly and laterally.

Pleasure concept (1937)

• M.A. Pleasure introduced a Pleasure curve or the posterior reverse

lateral curve to align and arrange the posterior teeth in order to

increase the stability of the denture.

• He used reverse curve in the first premolar, flat occlusal surface on

the first molar and Monson curve at the second molar to achieve

balance.

• The reverse curve helped in directing the forces of occlusion

lingually to enhance the stability of the lower denture.

Frush’s concept

• He advocated arranging teeth in a one-dimensional contact

relationship, which could be reshaped during the wax try-in to

obtain balanced occlusion.

Hanau’s quint (1929)

• Rudolph L. Hanau proposed that five factors were important in

achieving balanced occlusion, which are as follows:

(i) Condylar guidance

(ii) Incisal guidance

(iii) Compensating curves

(iv) Relative cusp height

(v) Plane of orientation of the occlusal plane

Trapozzano’s concept

• It is also called ‘triad of occlusion’.

• Reviewed factors of Hanau’s Quint and came to the conclusion that

only three factors were important to achieve balanced occlusion.

• He eliminated the plane of occlusion as he believed that its location

is highly variable and depends on the available interarch space.

• He suggested that occlusal plane should be located at various

heights to favour a weaker ridge.

• The other factor which he considered unimportant was the

compensating curve.

• When the cuspal angulation that will produce balanced occlusion is

determined, the concavity or convexity of the curve can easily be

evaluated.

Lott’s concept (fig. 8-10)

• F. Lott 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.

FIGURE 8-10 Lott’s chart.

Lott’s Laws of Occlusion are:

• Greater the angle of the condylar path, greater will be the posterior

separation during protrusive movement.

• Greater the vertical overlap, greater is the separation in the anterior

region and the posterior region regardless of the angle of the

condylar path.

• Greater the separation of the posterior teeth, greater or higher will

be the compensating curve.

• Posterior separation beyond the balancing ability of the

compensating curve requires the introduction of the plane of

orientation.

• Greater the separation of the teeth, greater must be the height of the

cusps in the posterior teeth.

Boucher’s concept

• C.O. Boucher confronted V.R. Trapozzano’s concept and proposed

the following three factors for balanced occlusion.

(i) According to him, there are three fixed factors,

namely, orientation of the occlusal plane, incisal

guidance and the condylar guidance.

(ii) Angulation of the cusp is more important than

the height of the cusp.

(iii) The compensating curve enables one to

increase the effective height of the cusps without

changing the form of the teeth.

Levin’s concept

• This concept was similar to the Lott’s concept except here the plane

of orientation factor is eliminated.

• According to him, the plane of occlusion can be slightly altered by

1–2 mm in order to improve stability of the denture.

• He named other four factors as QUAD.

• The condylar guidance is fixed and given by the patient. The

balancing condylar guidance includes the Bennett shift of the

working condyle. This may or may not affect the lateral balance.

• Incisal guidance is obtained from the patient’s aesthetic and

phonetic requirements. However, it can be modified (e.g. in cases of

resorbed residual ridges, the incisal guidance can be reduced).

• Compensating curve is the most important factor for obtaining

balance. Monoplane or low cusp teeth should employ the use of

compensating curve.

• Cusp teeth or anatomic teeth have the inclines necessary for

obtaining the balanced occlusion but are used mostly with the

compensating curve.

Factors influencing balanced occlusion

Rudolph L. Hanau proposed nine factors that govern the articulation

of the artificial teeth, which are:

(i) Horizontal condylar guidance

(ii) Compensating curves

(iii) Protrusive incisal guidance

(iv) Plane of orientation

(v) Buccolingual inclination of tooth axis

(vi) Sagittal condylar pathway

(vii) Sagittal incisal guidance

(viii) Tooth alignment

(ix) Relative cusp height

These nine factors were called the laws of balanced articulation.

Hanau later condensed these nine factors and formulated five factors,

which are commonly known as Hanau’s Quint.

(i) Condylar guidance

(ii) Incisal guidance

(iii) Compensating curves

(iv) Relative cusp height

(v) Plane of orientation of the occlusal plane

Condylar inclination (fig. 8-11)

FIGURE 8-11 Diagram showing condylar inclination which is

the only factor given by the patient.

Definition

Condylar inclination is defined as ‘the direction of the lateral condylar

path’. (GPT 4th Ed)

• It is the only factor which is given by the patient.

• The inclination of the condylar path is determined by the protrusive

record.

• This factor is fixed by the patient and cannot be altered by the dentist.

• The articulator is programmed using the protrusive record of the

patient.

• The occlusion set on the articulator should be in harmony with the

patient’s temporomandibular joint.

Incisal guidance (fig. 8-12)

Definition

Incisal guidance is defined as ‘the influence of the contacting surface of the

mandibular and maxillary anterior teeth on mandibular movements’. (GPT

8th Ed)

• It is called the second factor of occlusion.

• It is determined by the dentist and altered depending on the individual

case.

• It can be set depending upon the desired overjet and overbite planned

for the patient.

• It is the anterior controlling factor.

• If the overjet is increased, the inclination of the incisal guidance is

decreased.

• If the overbite is increased, the inclination of the incisal guidance

increases.

• The incisal guidance has greater influence on the posterior teeth

than the condylar guidance.

• This is because the posterior teeth are closer to the action of incisal

inclination than the action of the condylar guidance.

• During protrusive movements, the incisal edge of the mandibular

anterior teeth move in a downward and forward path

corresponding to palatal surface of the upper incisors.

• This is known as the protrusive incisal path or incisal guidance.

• The angle formed by this protrusive path to the horizontal plane is

called protrusive incisal path inclination or the incisal guide angle.

• This influences the shape of the posterior teeth.

• If the incisal guidance is steep, the compensating curve is needed to

produce balanced occlusion.

• In a complete denture, the incisal guide angle should be as flat

(more acute) as the aesthetics and phonetics permit.

• Therefore, while arranging the anterior teeth, for aesthetics, a

suitable vertical overlap and a horizontal overlap should be chosen

to achieve balanced occlusion.

• Also, once the aesthetics is established, this factor becomes fixed.

• If the incisal guidance is steep, then to achieve balanced occlusion

steep cusps, steep occlusal plane or compensating curve is used.

• The location of the incisors is governed by various factors such as

aesthetics, function and phonetics.

FIGURE 8-12 Schematic diagram showing incisal guidance:

(A) anterior teeth; (B) incisal guide table.

Determinants of the incisal guidance are:

• Phonetics

• Aesthetics

• Ridge relationship

• Arch shape

• Ridge fullness

• Inter-ridge space

Plane of orientation (fig. 8-13)

Definition

Plane of orientation is defined as ‘the average plane established by the

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

represents the planar mean of the curvature of these surfaces’. (GPT 8th Ed)

• The plane of orientation should be established exactly as it was

when the natural teeth were present.

• It is established anteriorly by the height of the lower canine, which

nearly coincides with the commissures of the mouth and posteriorly

ends at the anterior two-thirds of the retromolar pad.

• It is essentially parallel to the ala–tragus line or the Camper’s line.

• It can be slightly altered and its role is not as important as other

factors.

• Tilting the plane of occlusion beyond 10° is not advisable.

• Research shows that when the occlusal plane is parallel to the ala–

tragus line, the closing force during maximum clenching is greater

than when it is altered ±5°.

FIGURE 8-13 Diagram showing height of occlusal plane.

Cuspal inclination

Definition

Cusp angle is defined as ‘the angle made by the average slope of the cusp

with the cusp plane measured mesiodistally or buccolingually’. (GPT 8th Ed)

• The cusps on the teeth or the inclination of cuspless teeth are

important factors that modify the effect of plane of occlusion and

the compensating curves.

• The mesiodistal cusps lock the occlusion, such that repositioning of

teeth does not occur due to settling of base.

• In order to prevent the locking of occlusion, all the mesiodistal

cusps are eliminated during occlusal reshaping.