BEGINNING WITH THE END IN MIND

ANTERIOR GUIDANCE:

Restoring upper & lower ant teeth

CONTENTSAnterior guidance:

Steps in harmonizing the anterior guidance

Restoring of lower anterior teeth:

Restoring the upper anterior teeth

Duplicating the incisal edge outline

conclusion

Anterior Guidance

1. The influence of the contacting surfaces of the mandibular and maxillary teeth on mandibular movements.

.

Natural dentition

Articulator

Two posterior controls or the

temporomandibular joints

The anterior control or the

incisal guidance

Two condylar guidances of the

articulator

Incisal guide pin of the

articulator

• Controlling factors of occlusal rehabilitation So it is imagined as stable inverted tripod at centric relation of mandible

Classification of maxillofacial prosthesis

To incise food

To aid in speech

To aid in esthetics

To protect the posterior teeth, by directing the teeth together in centric occlusion so that the closing forces will be vertically directed onto the posterior teeth

Functions

anterior guidance is considered to be not a fixed but a variable factor. It can be altered by dental procedures such as restorations, orthodontia, and extractions. It can also be

altered by pathologic conditions such as caries, habits, and tooth wear

Why is incisal guidance important?

If the closing motion of mandible is stopped by the incisal edges of all six lower ant teeth

we have not only taken advantage of the position of the front teeth but also

strehgthened this position by distributing stress.

key factor in protecting the posterior teeth.

key factor in protecting the posterior teeth.

Williamson demonstrated that disculsion of all posterior teeth in eccentric jaw position reduces muscle contraction in elevator muscles. This enables us to reduce the load on both the TMJs and the posterior teeth in all excursions

Which teeth can best accept horizontal forces?

• Damaging horizontal forces of eccentric movement must be directed to the anterior teeth

You crack the nuts closer to the fulcrum, where you’re maximum mechanical advantage resides. Well the same

principles of physics apply to teeth,

Anterior teeth receive less stress because they are the furthest from the TMJ, which is the fulcrum n muscle force.

The relationship between the incisal guidance and cuspal inclination.

B. The upper and lower posterior teeth have steep lateral occlusal contours which are in harmony with the steep incisal guidance

D, The upper and lower posterior

teeth have reduced steepness of the lateral inclines which are in harmony with incisal guidance

RELATION BETWEEN ANTERIOR AND CONDYLAR GUIDANCE

Kohno and Nakano The inclination of the incisal

path should be equal to the inclination of the condylar path. The incisal path should not be flatter than the condylar path in the sagittal plane. A jerky condylar

movement will result from an incisal path that is flatter than the condylar path.

What happens when condyles slide curved pathways of ementiae

•If the condyles slide forward the lower ant teeth have to move forward too.

•It is a popular fallacy that whatever the condyles follow must be duplicated in the lingual surface of the upper ant. teeth so the lower ant teeth can follow the same path.

Condylar paths do not dictate the ant guidance and there is no need to even try to make the ant guidance duplicate

condylar guidance.

This allows the front end of the mandible to follow a completely

different path without interfering with the condylar

path.

advocates of such concept they have failed to recognize that the condlyes rotate as

they move along their protusive pathways.

The path that the condyles travel dictates the outer limits to which the mandible can move. Path that front end of the mand follows is dictated by functional movements of muscle as it relates the lower ant teeth to upper ant teeth in the chewing cycle.

Each of these patients has same outer limits of motion but each has different envelope of function. Even though condylar guidance is same the ant teeth would be contoured differently.

Ant guidance is a separate entity and must be determined in the mouth where the

determinants of ant tooth position can be observed in function.

• The arrangement of entire occlusal scheme starts with the lower ant teeth

Analysis of lower anterior teeth• Analyze lower anterior segment from several different

perspectives.

• If the teeth are stable , function comfortably and are esthetically acceptable to the patient there would be rarely any need to change them

• There shud be no signs of instability. Like wear, hypermobility, tooth migration etc.

• Every contour has a purpose that is related to function.

• Both visual and digital examination should be used to determine whether any teeth are being moved during lateral excursions

• Correction usually consists of reshaping the upper lingual contours. Correction of upper lingual contours is patterned to accomplish two effects : redirection of force vector and improved distribution of forces.

Modification of Incisal Guidance

Steep incisor guidance

• Increase VDO when indicated• Reduce incisal edges of lower ant.• Place pin ledge inlays on lingual surface of upper

anteriors– Restore tooth contact in centric position– Formation of fav. Ecc. Incisor guide contours

Harmonizing the Anterior guidance

Lower anterior teeth reshaped and restored

Establish coordinated centric relation stops on all anterior teeth

• There should be no deviation from centric contact . Incase present should be removed by removing interferences

• If no contact on some teeth are present after deviation is eleminated we hv three choices

CLOSE VERTICAL BY GRINDING

BUILD UP TEETH TO CONTACT

ESTABLISHING LONG CENTRIC

Extend centric stops forward at the same vertical to include light closure from the postural rest position.

• Establish group function (of the anterior teeth) in straight protrusion.

• Establish ideal anterior stress distribution in lateral excursions.

Analyzing incisal edge outline.

In most of patients the incisal edges have lost

Definite line angles

a common mistake is to round the edges, instead of preserving

the definite line angles

Labio incisal line angle is too low

and angle of incisal edge is too

high for stability and as a holding

stop and is also unesthetic

Lingual line angle is too low

result is poor esthetics n

problem with excursive

movements

Rounded edge are the first

Worst

esthetic contour

Not acceptable holding

contact

Proper incisal edge contour is necessary for optimum occlusal stability. It can be! analyzed from two perspectives:

a lateral view and an incisal view.

A correct lingual line angle

is higher than the labio

incisal angle

RELATING THE INCISAL PLANE

The lower incisal edges viewed together form the

incisal plane. It is as important to phonetics as

it is to esthetics.

RELATING LOWER INCISAL EDGES TO THE LIPS

LIPS SEALED:

• THE LOWER INCISAL EDGE IS AT THE HEIGHT OF THE JUNCTURE OF THE UPPER AND LOWER LIPS

lips slightly pated and jaws at rest : • at this position the upper lip completely

covers the maxillary teeth while the lower lip droops down to expose approximately one half of the labial surface of the mand incisors..

Relation during speech:

During speech the lower ant teeth are in view and the upper teeth are generally covered.

During smiling, the lower teeth are completely covered and the upper ant teeth are exposed.

Detection of neutral zone problems for anterior teeth

• Observing the condition of the alveolar process on the labial surface and noting its contour.

• Observing the angulation of the anterior teeth.• • outward pressure of the tongue and the inward

pressure of the perioral musculature set the limits within which the teeth can he stable.

INCLINATION OF LOWER INCISORS IS DIRECTLY RELATED TO NEUTRAL ZONE PRESSURES THAT RESULT

FROM PERIORAL MUSCULATURE AND TONGUE.

SURGICAL PROCEDURES

• The procedure advocated by Frederick involves a surgical cut vertically-through the buccinator muscle just anterior to mental foramen.

• This is foIlowed at the same appointment by vestibuloplasty from mesial of the second bicuspid around to the opposite side at the same position.

RELATING LOWER INCISOR POSITION WITH CEPHALOMETRICS

• Lower incisors seem to remain stable if they are positioned at a 90-degree angulation to a line drawn from the hinge axis point to the incisal edge.

• This is referred to as the hinge axis angle.

• Ricketts has advocated relating the lower incisors to the A-Po plane.

• Labial surface of the lower incisor is approximately 1 mm forward of the A-Po plane, its position is in harmony with the basal jaw

CENTRIC RELATION STOPS

The position of lower incisor in centric relation determine the start of contour of the upper ant teeth.

Lower incisal outline determines the reciprocal contour for each holding

contact on upper teeth

LIP SUPPORT

The labial contours of upper ant teeth should support the upper lip at rest. It should neither sink nor bulge

Natural drape should be der.

the upper half of the labial contour relates directly to the labial contour of the alveolus. It should be nearly parallel and continuous with tissue over root.

LIP CLOSURE PATH

Lower lip should go smoothly past the labio incisal line angle of upper incisors.There should be no feeling of strain

TOOTH TO LIP RELATION DURING F AND V SOUNDS

When f and v sound are made upper incisal edges should contact the

vermilion border of lip.

The smile line: the incisal edges should contact the smiling lip line contour without

strain

In making S sound the flow of air must be constricted into a flat wide band between the hard surfaces of the lower and upper teeth. The position may vary from near contact in some patients to edge to edge contact in others.

If the s sound is made at an overlap position the lower incisal plane is more likely to have a convex

bow to its contour so that it can fit the concavity of the upper lingual surfaces.

• It the s sound is made at an edge to edge position the lower incisal plane is likely to be flatter.

• As a general rule more convex the incisal plane on the upper teeth more convex it will be on lower teeth. A convex upper incisal plane caannot make a clear s sound at end to end position because air leaks out at sides.

If the lower incisal plane does not closely approximate the contour of the upper arch during the s sound lisping results because of using the tongue to fill in the void so that the air can be squeezed into the flattened band to produce a crisp s sound.

DETERMINING LINGUAL CONTOURS FOR UPPER ANTERIOR TEETH

THE ENVELOPE OF FUNCTION IS INCORPORATED INTO THE

LINGUAL CONTOURS AFTER THE INCISAL EDGES ARE DETERMINED.

Analyzing cingulum contourCingulum contour should conform with the natural position of the tongue during t and d sounds.

If the lingual surface must be extended to provide a holding contact for lower incisors n this may interfere with t-d togue position. Problem must be explained to patient.

Patients adapt with time

3.5mm of protusion forward of the A-Po plane

How to fabricate incisal guidance

CONCLUSION

• Complete oral rehabilitation is one of the most complex services the dentist is called upon to render.

• Its successful completion requires unusual knowledge, judgment, and dexterity acquired only by diligent study and application.

•

THANK YOU

REFERENCES• • Dawson P. Functional Occlusion: From TMJ to Smile Design. St.

Louis, MO: Mosby; 2006:347.• Lawrence A. WEINBERG. Incisal and condylar guidance in relation to

cuspal inclination in lateral excursions. 1959;9:5.• Schuyler The function and importance of incisal guidance in oral

rehabilitation. 2001:86;3.• Schuyler, C. H.: Correction of Occlusal Disharmony of the Natural

Dentition, New York J. Den. 13:445-462, 1947.• Schuyler, C. H.: Factors Contributing to Traumatic Occlusion, J. Pros.

Den. 11:708-717, 1961.• Stallard, H., and Stuart, C. E.: Eliminating Tooth Guidance in Natural

Dentitions, J. Pros. Den. 11:474-479, 1961.

Anatomically

, 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 maxill

ary and

mandibular

central incisor

s when

the teeth are in maxim

um intercuspati

on.

On an

articulator, that

angle formed in the

sagittal

plane,

between the

plane of

reference and the

slope of

the anteri

or guide table,

as viewed in the

sagittal

plane

Incisal guide angle: