BALANCED OCCLUSION

ByReema Talat AyeshaFinal yearR.R.D.C

DEPARTMENT OF PROSTHODONTICS

• Definition• Types of Balanced Occlusion -Unilateral -Bilateral -Protrusive -Lateral • Concepts of Balanced Occlusion -Gysi’s concept -French’s concept -Sears concept -Pleasure’s concept -Hanau’s Quint -Trapozzano’s concept of occlusion -Boucher’s concept -Lotts concept • Factors influencing Balanced Occlusion

DEFINITION‘The simultaneous contacting of the

maxillary and 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 tipping or rotating of the denture bases in relation to the supporting structures”-GPT

Types of Balanced OcclusionUnilateral Balanced OcclusionThis is a type of occlusion seen on occlusal

surfaces of teeth on one side when they occlude simulatenously with a smooth , uninterrupted glide. This is not followed during complete denture preparation. It is more pertained to fixed partial dentures.

Bilateral Balanced OcclusionThis is a type of occlusion that is seen when a

simultaneous contact occurs on both sides in centric and eccentric positions. Bilateral balanced occlusion helps to distribute the occlusal load evenly across the arch and therefore helps to improve stability of the denture during centric, eccentric or parafunctional movements.

Protrusive balanced OcclusionThis type of balanced occlusion is

present when mandible moves in a forward direction and the occlusal contacts are smooth and simultaneous anteriorly and posteriorly.There should be atleast three points of contact in the occlusal plane.Two located posteriorly and one anteriorly.Absent in natural dentition.Posterior contact during protrusion to

maintain balance

Lateral Balanced OcclusionIn lateral balance there will be a minimal simultaneous three point contact present during lateral movement of mandible.This is absent in natural dentition.Teeth should be arranged such that there is simultaneous tooth contact in balancing side and working side.Canine guided disocclusion.This relationship is seen in natural dentition

Anterio and posterior tooth contact during laterotrusion seen on working side.

Mechanics of balanced occlusion

In natural teeth when the mandible is protuded so that the incisal edges of the upper & the lower teeth contact, there is a gap between the upper & lower posterior teeth, this is termed as “Christensen’s phenomenon”.

But this occlusion could cause tipping of the denture in the posterior region. Thus simultaneous anterior & posterior contacts are required when mandible is protruded.

Concepts proposed-

• Gysi’s conceptHe proposed the first

concept towards balanced occlusion in 1914.He suggested arranging 33 degree anatomic teeth could be used under various movements of the articulator to enhance the stability of the denture.

• French’s conceptHe proposed lowering the lower occlusal

plane to increase the stability of the dentures along with balanced occlusion.he arranged upper first premolars with 5º inclination,upper second premolars with 10º inclination and uppe r molars with 15º inclination.He used modified French teeth to obtain balanced occlusion.

• Sears’s ConceptHe proposed balanced occlusion for non

anatomical teeth using posterior balancing ramps or an occlusal plane which curves anteroposteriorly and laterally.

• Pleasure’s conceptPleasure introduced a pleasure

curve or the posterior lateral curve to align and arrange posterior teeth in order to increase the stability of the denture.

• Frush’s conceptHe advised arranging teeth in a

one dimensional contact relationship,which should be reshaped during try in to obtain balanced occlusion.

• Hanau’s QuintRudolph L.Hanau proposed nine factors

that govern the articulation of artificial teeth.They are

-Horizontal condylar guidance -Compensating Curve -Protrusive Incisal Guidance -Plane of orientation -Buccolingual inclination of tooth axis -Saggital condylar pathway -Saggital Incisal Guidance -Tooth Alignment -Relative Cusp Height “LAWS OF BALANCED

ARTICULATION”

Hanau later condensed these nine factors and formulated five factors which are commonly known as Hanau’s Quint:

-Condylar Guidance -Incisal Guidance -Compensating

curves -Relative Cusp Height -Plane of Orientation of

occlusal plane

A). Incisal guidance B). Condylar guidanceC). Cuspal angulation D).plane of occlusionE). Compensating curve.

• Trapozzano’s Concept of Occlusion

HE reviewed and simplified Hanau’s Quint and proposed his Triad Of Occlusion.He said that plane of occlusion could be shifted to favour weak ridges,hence its location is not constant and is variable within the inter arch distance.

-Condylar Guidance -Incisal Guidance -Relative Cusp Height

• Boucher’s Concept

Boucher proposed the following three factors for balanced occlusion.

-Orientation of the occlusal plane,the incisal guidance

and the condylar guidance. -The angulation of the cusp is

more important than the height of the cusp.

-The compensating curve enables one to increase the height of the cusp without changing the form of teeth

• Lott’s Concept -The greater the angle of the condylar

path,the greater is the posterior separation during protrusion.

-The greater the angle of the overbite,the greater is the separation in the anterior and posterior regions irrespective of the angle of the condylar path.

-The greater the separation of the posterior teeth the greater or higher must be the compensating curve.

-Posterior separation beyond the balancing abiltiy of the compensating curve can be balanced by the introduction of the plane of orientation.

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

• Levin’s Concept

He named the four factors of occlusion as the QUAD

-The condylar guidance is fixed and is recorded from the patient.

-The incisal guidance is usually obtained from patients esthetic and phonetic requirements

-The compensating curve is the most important factor in obtaining occlusal balance.

- Cusp teeth have the inclines necessary for balanced occlusion but nearly always used with a compensating curve.

Factors influencing balanced occlusion

Thielemann’s formula

• Balanced Occlusion= K . I• OP .C .

OK • Where,• K CONDYLAR INCLINATION,• I INCISAL INCLINATION,• C CUSPAL HEIGHT,• OP INCLINATION OF PLANE OF

ORIENTATION,• OK PROMINANCE OF

COMPENSATING CURVE.

1. CONDYLAR GUIDANCE

This is the only factor which can be recorded from patient.It is registered using prostrusive registration and transferred to the articulator as the condylar guidance.This factor of Balanced occlusion cannot be modified.

“Mandibular guidance generated by the condyle and articular disc traversing the contour of the glenoid fossae”

a).Horizontal condylar guidance-guides the forward movement for protrusive balance.

b).Lateral condylar guidance-guides the sideward or lateral movement of the mandible.

Posterior slope of the articular eminence represented by the condylar tract of articulator

2. INCISAL GUIDANCE

“The influence of the contacting surfaces of the mandibular and maxillary anterior teeth on mandibular movements’

It is determined by the dentist and customised for the patient during anterior try in. It acts as a controlling path for the movements of the casts in an articulator.Its should be set according to the desired overjet and overbite planned for the patient.If overjet is increased,the inclination of the incisal guidance is decreased.The incisal guidance has more influence on posterior teeth than condylar guidance.

3. PLANE OF OCCLUSION OR OCCLUSAL PLANE

“An imaginary surface which is related

anatomically to the cranium and which theorotically touches the incisal edges of the incisors and tips of occluding surfaces of the posterior teeth.It is not a plane in the true sense of word but represents the mean curvature of the surface “

It is established anteriorly by the height of the lower canine,which nearly coincides with the commisure of the mouth and posteriorly by the height of the retro molar pad.It is usually parallel to Camper’s line.

The plane of occlusion can be altered to a maximum of 10o

4. COMPENSATING CURVES

“The anteroposterior and lateral curvatures in the allignment of the occluding surfaces and incisal edges of artificial teeth which are used to develop balanced occlusion.”

2 types of curves: -Anteroposterior curves -Lateral curves

Posterior teeth separation when the curve of spee not incorporated

Incorporating the curve spee will provide posterior tooth contact during protrusion

It is seen in the natural dentition and should be reproduced in a CD. The significance of the curve is that, when the patient moves his mandible forward, the posterior teeth set on this curve will continue to remain in contact.

Curve of Spee“Anatomic curvature of the occlusal alignment of teeth beginning at the tip of lower canine and following buccal cusps of natural premolars and molars,continuing to the anterior border of ramus”

Monson’s Curve

“The curve of occlusion in which each cusp and incisal edges touches or conforms to a segment of a sphere of 8 inches in diameter with its center in the region of Glabella.”

Only if teeth are set following Monsons curve will there be lateral balance of occlusion.runs across the palatal & buccal cusps of maxillary molars.

• Wilson’s Curve

“A curve of occlusion which is convex upwards”

This curve is followed when first premolars are arranged. The premolars are arranged according to this curve so that they do not produce any interference to lateral movements.

Lateral view with 2nd PM & 1st molar follow the reverse curve

Reverse curve is used in the bicuspid area for lever balance

Pleasure Curve/Reverse Curve

“A curve of occlusion which in transverse cross section conforms to a line which is convex upward except for last molars”This curve runs from palatal cusp of the first premolar to the distobucaal cusp of second molar,The second molar gives occlusal balance and the second premolar gives lever balance.

5. Cuspal Angulation

“The angle made by the average slope of a cusp with the cusp plane measured mesiodistally and buccolingually”

The cusps on the teeth or the inclination of the 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 the repositioning of teeth does not occur due to settling of the base. To prevent the locking of occlusion the mesiodistal cusps are reduced during occlusal reshaping.