CONTENTS

INTRODUCTION

DEFINITION

IDEAL CONTACTS AND CONTOURS

ROLE OF CONTACTS AND CONTOURS

CAUSES OF IMPROPER CONTACTS, CONTOURS,

EMBRASSURES, MARGINAL RIDGES

HAZARDS

HISTOPATHOLOGY OF THE EFFECTED TISSUES

PROCEDURES FOR FORMULATION OF PROPER CONTACTS

AND CONTOURS

CONCLUSION

REFERENCES

CONTACT AREAS AND CONTOURS

INTRODUCTION:

From the cariogenic aspect there may be only 20 occlusal surfaces but there

are 60 contacting proximal and 64 facial and lingual surfaces susceptible to caries

mainly due to faulty interrelationship between the contact areas, marginal ridges,

embrasures and the gingiva.

Decay on the facial and lingual surfaces is especially in the gingival 1/3 rd

primarily by faulty interrelation between the tooth contour and the periodontal

components.

From the periodontal aspect, periodontitis may also be caused both

interproximally and in the facial and lingual periodontium by these faulty

interrelationships.

The key to these proper relationships interproximally is the contact area and

faciolingually are the occlusogingival and mesiodistal configuration.

Contact Area:

The contact area is the site of actual contact between two teeth on the

mesial and distal surfaces and is erroneously called a contact point.

This is the area of height of contour of the mesial and distal surfaces of a

tooth. Some authors describe the contact as “marble type” of relationship. The

contact point becomes a contact area because of wear of one proximal surface

against another during physiologic tooth movement which results in a flattened

contact area of 2 or 3mm in posterior teeth and slightly smaller in anterior teeth.

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Height of Contour:

The height of contour is the area of greatest circumference on the facial and

lingual surfaces of the tooth.

Embrasures:

Proximal curvatures adjacent to the contact area from V-shaped spillway

spaces called Embrasures. The spaces that widen out from the area of contact are

labial or buccal and lingual embrasures. Above the contact areas occlusally are the

incisal or occlusal embrasures and below the contact areas are the gingival

embrasures which are filled with the interdental papilla.

Emergency Profile:

The part of the axial contour that extends from the base of the gingival

sulcus past the free margin of the gingiva has been described as the emergence

profile by stein and kuwata. The emergence profile extends to the height of

contour producing a straight profile in the gingival third of the axial surface.

Contact areas (Buccal and Occlusal Aspect):

According to their general shapes, teeth can be divided into 3 types with

each having its own physical characteristics in the contact areas.

1. Tapering teeth

2. Ovoid teeth

3. Square teeth

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Contact Tapering Ovoid Square

1. Incisors Incisal ridges Mesial – ¼ of crown inciso gingivally.

Incisal ridges

Labio-lingually it is labially.

Distal – 1/3rd to ½ of crown lingually.

Labio-lingually it is in the center.

2. Canine Mesial-Incisal ridge

Distal – Middle

Close to incisal ridges

Close to incisal ridges

Labio-lingually it is in the center

Centre Centre

3. Bicuspids Junction of the occlusal and middle 1/3rd.

Middle 1/3rd Occlusal 1/3rd

Labio-lingually it is at the buccal axial angle

Junction of buccal and middle 1/3rd

Towards buccal axial angle

4. Molars mesial contact

Junction of the occlusal and middle 1/3rd.

Middle 1/3rd Occlusal 1/3rd

Labio-lingually it is at the mesio-buccal axial angle of tooth.

Junction of buccal and middle 1/3rd

Towards buccal axial angle

5. Molars distal contact

Distal contact of mandibular first molar is variable due to the position of distal cusp.

Occluso-gingivally at the middle 1/3rd

Buccolinaully at the middle 1/3rd

Occluso gingivally at the middle 1/3rd

Buccolingually in line with the central groove of the occlusal surface.

If small contact occlusal 1/3rd lingually.

If large contact from lower border of the marginal ridge to the CEJ.

1/3rd to 2/3rd of the crown bucco-lingually.

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Proximal Contours:

1. Tapering teeth:- Proximal contour of the tapering type of teeth has one

common feature: Starting at the CEJ, the surface presents a concavity almost to

the contact areas and they are decidedly convex from there to the crest of the

marginal ridges. The concavities are more pronounced on the mesial than on

the distal surfaces. Concavities occur most frequently on the mesial surfaces of

teeth having buccal and lingual roots, most pronounced being the mesial of the

first maxillary premolar.

2. Square teeth: The proximal contours of square type teeth have a tendency to

become a plane instead of a curved surface. Buccol-lingual concavities are

found occasionally on the mesial surfaces of the maxillary first bicuspids, first

and second molars, and the mesial surface of mandibular first molar. The distal

surfaces are generally either flat or slightly convex. The convexity which

creates the marginal ridges disappear at the contact and the remainder of the

surface in the gingival direction is usually flat.

3. Ovoid teeth: Proximal contours of ovoid anterior teeth are convex from the

incisal angle to the CEJ. Bicuspids of the ovoid type are frequently bell shaped

with the convex surface running from the crest of the marginal rides almost to

the CEJ where they merge via a slightly concave surface to a union with the

root surfaces. The mesial surfaces of ovoid molars present convex areas which

are less extensive than those on distal surfaces.

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Facial and Lingual Contours:

In a vertical direction, all tooth crowns will exhibit some convex curvatures

occlusal to the cervical line. This curvature is sometimes called the cervical ridge.

The extent of curvatures varies in different individuals but does not extend more

than 1mm beyond the cervical line.

Although inciso-apical curvature of the facial and lingual surfaces of all

teeth is convex, the incisal ½ to 1/3 of the lingual surfaces of anterior teeth

displays some concavities, more pronounced with upper centrals and laterals. The

canines show more convexity on the facial surface than the centrals and laterals.

In posterior teeth there will be a mesio-distal convexity corresponding to each

cusp. In molars where there is more than one cusp buccally and lingually, these

convexities are interrupted by concavities at the occlusal ½ to 2/3rd of the crown.

The convexity decreases as we approach CEJ and will flatten or become concave,

especially if the crown surface joins a bifurcation.

The curvatures on the labial, buccal and lingual surfaces of all maxillary

and buccal surface of mandibular posterior teeth are almost uniform, about 0.5 mm

or less. Mandibular anterior teeth have less curvature than any other teeth and

sometimes it is hardly distinguishable. Mandibular posterior teeth will have a

lingual curvature of approximately 1mm, with the crest of the curvature at the

middle 1/3rd instead of cervical 1/3rd, this is due to the lingual inclination of the

teeth.

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Embrasures:

1. Tapering type:- They show great variation than other types. Incisal and labial

embrasures are almost negligible. The gingival and lingual embrasures

between anterior teeth are the widest and longest in the mouth. Buccal

embrasures are small. Lingual embrasures are long, with medium width.

Gingival embrasures between posterior teeth are broad and long.

2. Square type:- Incisal, lingual, occlusal and buccal embrasures are nil. Gingival

embrasures are almost not noticeable, if found, they are very narrow and flat.

Lingual embrasures are very narrow and long.

3. Ovoid type:- Incisal, buccal, labial and occlusal embrasures are wider and

deeper than others. Gingival and lingual embrasures are short and broad.

Role of Contact Areas:

A positive relationship should exist between the contacts to resist food

impaction and to protect the gingival tissue. This relationship can be tested by

passing dental floss between the teeth and observing the resistance when the floss

is moved from the gingiva between the two enamel surfaces.

Proximal contacts and interdigitation of the teeth through occlusal contacts

stabilizes and maintains the integrity of the dental arches. With the increasing age

the contact areas become wide and flat due to physiologic wear and it is difficult

to clean these areas which might lead to periodontal problems.

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Role of contours:

Especially the facial and lingual surfaces height of contour affords the

protection and stimulation of the supporting tissues during mastication. In case of

anterior teeth labial and the proximal contours play an important role in esthetics.

Role of embrasures:

The outline form of restoration will include the diseased tooth structure and

extend so that the margins are located in the embrasure for cleaning purposes.

The food particles that are not crushed between the teeth slide through the

embrasures to the tongue and are thrust back onto the occlusal surfaces for

mastication. In this way mastication is facilitated by the lingual embrasures and to

a lesser extent by the facial embrasures.

Role of Emergence Profile:

Production of a straight profile should be a treatment objective in restoring

a tooth because it facilitates access for oral hygiene measures. The straight profile

is easily evaluated with a periodontal probe.

Through the years, undue importance, probably has been attributed to a

‘protective’ role of the axial contour in the cervical region. As a result, both

dentists and dental techniques frequently create a bulge where there should be

none, as well as place it apically in the cervical region. Such restorations usually

promote the accumulation of food debris and plaque and gingival inflammation is

encouraged rather than prevented.

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Role of Marginal Ridges:

Marginal ridges play an important role in withstanding and dissipating the

occlusal stresses. The correct form of marginal ridge compatible with the adjacent

tooth and also with its own surroundings is important during carving of posterior

restoration. A marginal ridge should always be formed in two planes bucco-

lingually, meeting at a very obtuse angle. This feature is essential when an

opposing functional cusp occludes with the marginal ridge.

A marginal ridge with these specifications is essential for the balance of the

teeth in the arch, the prevention of food impaction proximally, the protection of

the periodontium, prevention of recurrent and contact decay and for helping in

efficient mastication.

This diagram illustrates the function of the marginal ridges. Forces 1 and 2,

acting on two adjacent marginal ridges will have their horizontal components 1H

and 2H drive the two teeth towards each other, thus preventing any impaction

proximally, maintaining the mesiodistal dimension of the dental arch and

anchoring the teeth against occlusal embrasures are reduced, due to vertical

occlusal attrition and flattening of proximal contact areas.

Causes of Disturbances in Contact:

1. Physiological – midline diastema, spacing, rotation.

2. Plunger cusp, food impaction.

3. Fracture of teeth.

4. Proximal caries.

5. Habits – Unnecessary tooth picking, placing a nail or a needle between

teeth.

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6. Improper orthodontic force.

7. Jaw fracture

8. Improper restoration – improper cavity preparation, improper matricing,

improper widging, overhanging restorations, improper contouring of the

wax pattern of an artificial crown.

9. Missing tooth – drifting of teeth, supraeruption of opposing teeth.

CAUSES OF DISTURBANCES IN CONTOUR:

1. Physiological wear

2. Abrasion, erosion

3. Fracture of teeth

4. Enamel hypoplasia

5. Smooth surface caries

6. Improper restoration – improper matricing, overcontouring of restoration,

overcontouring of the wax pattern of an artificial crown especially

cervically on the buccal aspect.

Causes of disturbances in embrasure:

1. Improper contacts

2. Improper contours

3. Periodontal disease

Causes of disturbances in marginal ridges:

1. Proximal caries, fracture of teeth

2. Placing the contacts too gingivally or occlusally

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3. Improper restoration – absence of marginal ridge, creating a marginal ridge

not compatible in height with the adjacent tooth, a marginal ridge with no

adjacent triangular fossa, one planed marginal ridges in bucco-lingual

direction.

HAZARDS OF IMPROPER CONTACT AREAS:

1. Contact area that is too broad, bucco-lingually or occluso-gingivally will

change the anatomy of the tooth and the interdental column. The normal saddle

shaped area will become broadened. This is the most vulnerable area to

periodontal disease. Furthermore these broadened contacts produces an

interdental area that is difficult to clean and is more susceptible to decay.

Broadening of contact reduces the embrasures which usually leads to improper

movement or flow of masticated material. This leads to adhesion of debris and

possible interproximal impaction of that debris, which causes Halitosis. Due to

the periodontal problem there can even be loss of tooth.

2. Contact area that is too narrow, bucco-lingually or occluso-gingivally will

allow the food to be impacted vertically or horizontally on the delicate

interdental column. This will lead to greater susceptibility for plaque

accumulation which in turn predisposes to the same periodontal and caries

problems.

3. Contact area placed too buccally or lingually will result in flattened restoration

at the expense of the buccal or lingual embrasures.

4. Contact area placed too occlusally will result in a flattened marginal ridge at

the expense of occlusal embrasure.

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5. Contact area placed too gingivally will increase the depth of the occlusal

embrasures at the expense of the contact areas own size or at the expense of

broadening or impinging upon the interdental column.

6. Loose or open contacts may be caused by the occlusal forces moving the teeth

mesially or distally. It creates continuity of the embrasures with each other and

with the interdental column. These defects will allow for the impaction of food

and the accumulation of bacterial plaque with the accompanying periodontal

and caries problems.

Hazards of Improper Contours:

1. Facial and lingual convexities: Convex contours on the facial and lingual

surfaces of the teeth afford protection and stimulation to the supporting

structures during mastication. They direct the food towards the buccal

vestibule, palate or tongue while stimulating the surrounding soft tissue by

gentle massage rather than irritating it. Overcontoured curvatures can create a

favorable environment for the accumulation and growth of cariogenic and

plaque bacteria at gingival margin; apical to the height of contour. This results

in chronic inflammation of the gingiva.

It has been revealed that there is always more inherent danger in overconvex

rather than underconvex facial and lingual surfaces.

Morris, reported the response of gingival tissue around teeth prepared for

artificial crowns which had lost their temporary crowns were found to be

surrounded by healthy gingiva without plaque in the cervical region compared

with approximating unprepared teeth.

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Commonly, porcelain fused to metal crowns are overcontoured because of

inadequate facial reduction. Such an overcontour interferes with the sealing

cuff effect of gingiva against the tooth and the self-cleansing mechanism of the

gingival sulcus.

2. Facial and lingual concavities:- Concavities occlusal to the height of contour

are involved in the occlusal static and dynamic relations, as they determine the

pathways for teeth in and out of centric occlusion. Mislocated concavities will

lead premature contacts during mandibular movements and excessive

concavities can invite extrusion, rotation or tilting of occluding cuspal

elements into non-physiologic relations with opposing teeth.

Concavities apical to the height of contour, therapeutically or pathologically

exposed are essential for the proper maintenance of the accompanying new

components of the adjacent periodontium and must be initiated in a restoration.

Deficient concavities at these locations can create restoration overhangs and

excessive concavities decrease the chance for successful plaque control in the

extremely plaque retaining areas.

3. Proximal contours: In addition to creating a proper contact area, it is also

essential to restore a proper contour adjacent to the contact area. The proximal

crown contours are generally flat or concave. This provides adequate

embrasure space for the interdental gingiva and allows room from plaque

removal. The transitional line angle is also generally flat or concave to form

the opening for the embrasure space and house the interdental tissue.

Fabricating a restoration that does not reproduce the concavities and

convexities which occur here naturally will lead to restoration overhangs and

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underhangs, vertical and horizontal impaction of debris and impingment upon

the adjacent periodontal structures. Too narrow embrasures predispose teeth

and supporting structures to heavier stresses. Too wide embrasures offer little

protection to the underlying soft tissue.

Hazards of Improper Marginal Ridges:

1. Absence of marginal ridges in the restoration: By the absence of a marginal

ridge, force 1 will be directed toward the proximal of the adjacent tooth. The

horizontal components of force 1H and 2H will tend to drive the two teeth

away from each other. Mean while the vertical component 1V and 2V can

impact the food interproximally. The vertical component V2 will be more than

required, there may occur slight tilting of the tooth B.

2. A marginal ridge with wide occlusal embrasures: Exaggerating the occlusal

embrasure will direct forces 1 and 2 on adjacent proximal surfaces with the

horizontal components 1H and 2H separating the teeth and the vertical

components 1V and 2V driving the debris interproximally.

3. Adjacent marginal ridges not compatible in height: If a restored marginal ridge

is higher than the adjacent one, it will allow force A to work on the proximal

surface of the restoration. The horizontal component AH, will drive the

restored tooth away from the contacting tooth and the vertical component will

drive the debris interproxially. There will be some separation of teeth as the

surface hold force B is too small to counteract force A.

4. A marginal ridge with no adjacent triangular fossa: In this situation there are

no occlusal planes in the marginal ridges for the occlusal forces to act upon, so

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there are no horizontal components to drive the teeth towards each other,

closing the contact. Furthermore, the vertical force will tend to impact food

interproximally.

5. A marginal ridge with no occlusal embrasure: The two adjacent marginal

ridges act like a pair of tweezers grasping the food substance passing over it.

Though there will not be any vertical impaction of food, the contours impact of

higher concentration of vertical component of forces may lead to changes in

alveolar bone after sometime.

6. A thin marginal ridge in its mesio-distal bulk will be susceptible to fracture or

deformation leading to the problems of the previously mentioned faulty

marginal ridge. Also, this thinness may leave either shallow or deep adjacent

fossa or bulky anatomy with the same problems.

7. A one planed marginal ridge in the buccolingual direction can create premature

contacts during both functional and static occlusion. This type of marginal ride

increase the depth of adjacent triangular fossa, magnifying the stresses in this

area. Moreover, the one planed marginal ridge could increase the height of the

marginal ridge in the centre, making it amenable to the adverse effects of

horizontal components of force. Likewise, one planed marginal ridge will

deflect the food stream away from normal, proximal embrasure movements.

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HISTOPATHOLOGY OF THE AFFECTED TISSUES:

Imperfect formation, destruction or improper restoration of the contact areas

Food Impaction

Inflammation of superficial Proximal Caries tissues

Acute or chronic

Vasomotor nerves of the deeper Periodontal structures are first stimulated, then overstimulated and finally depressed in activity

Infection of soft tissues and adjacent bone

Tooth loss

PROCEDURES FOR THE FORMULATION OF PROPER CONTACTS

AND CONTOURS:

I. Intra Oral Procedures:

For the proper reproduction of contact areas and contours of the previously

described physio-anatomical features of teeth, two operative acts must precede the

restorative procedure.

1. Tooth movement

2. Matricing

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1. Tooth Movement:

It is the act of either separating the involved teeth from each other, bringing

them closer to teach other or changing their spatial position in one or more

dimensions. This is done in order to facilitate the creation of a physiologically

functional contact, contour and occluding anatomy in the restored tooth.

Objectives of tooth movement:-

a. To bring drifted, tilted or rotated teeth to their indicated physiologic

positions.

b. To close space between teeth in case of open contacts.

c. Intrusion or extrusion.

d. To move teeth from non-functional location to physiologically functional.

e. To move teeth for esthetics.

f. To create a space sufficient for the thickness of matrix band.

There are two principal methods of tooth movement:-

1. Rapid 2. Slow

i. Wedge method a. Separating wires

a. Elliot separator b. Oversized temporaries

b. Wooden or plastic wedges c. Orthodontic appliances

ii. Traction method

a. Non-interfering true separator

b. Ferrier double bow separator

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2. Matricing:-

It is a procedure where by a temporary wall is created opposite to axial

walls, surrounding areas of the tooth structure that were lost during preparation.

Different types of matrices are used for different types of cavities and

different types of materials.

Evaluation of different matrix technique:

Although there have been a very few investigations conducted on this

subject, the following observations can be summarized from information that is

presently available. It is clear that no matrix technique is capable of the exact

replication of normal anatomic contours of restored teeth. However, deviations

from normal are slight in any matricing procedure if proper contouring and

wedging are utilized.

Wedging is universally imperative in order to eliminate cervical flash of

restorative material. This is true with all three types of tooth shapes. Although

matrix contouring, in the absence of wedging, produces a more rounded contour

(especially on square-type teeth), it does not reduce cervical overhangs. With

tapering type teeth, however an accurate reproduction of the proximal surface can

be achieved without contouring i.e., wedge alone can be used. Ovoid type teeth are

the most difficult to reproduce, so that like square teeth, contouring in addition t

wedging is required.

Overhanging restorations have long been viewed as a contributing factor to

gingivitis and possible periodontal attachment loss. They pose a significant

concern as their prevalence has been estimated at 25-76%. The severity of bone

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loss was directly proportional to the severity of overhangs. Overhangs were

designated as large if they occupy >51% of interproximal space. Small and

medium overhangs (20-50%) which were not associated with bone loss. The

overhangs not only increase the plaque mass but also increase the specific

periodontal pathogens in the plaque. Most overhanging restorations can be

recontoured. A study demonstrated that a micromotor driven diamond tip is faster

for removing overhangs and led to smoother restorations compared to sonic

scalers and curettes (Sprinks et al. 1986).

Too many variables were used to trim overhangs and to change proximal

contours after the removal of a matrix but is difficult to recontour at this stage. It

would be better to utilize a matrix technique which will minimize the cervical

overhangs and improper contours. Even with the properly chosen technique, using

floss after condensation of amalgam definitely improves proximal contour as well

as reduce overhangs.

It was noticed that the circumferential matrix bands retained by tightening

devices have been shown to elastically deform tooth structures. Immediately after

removal of the matrix bands, tooth structures then regain their original dimension,

resulting in gaps between the tooth and the hardened restorative material. These

gaps may range from 11.4 to 25 . The width of this gap is directly proportional to

the width of the preparation, the pressure applied with the matrix and the

postoperative contraction of the particular restorative material used. Passively

inserted matrix bands like anatomic matrix and T-shaped bands etc., have no

deformative effect on the remaining tooth structures.

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Some esthetic problems can be corrected conservatively without the need

for tooth preparation and restoration which includes attrition of incisal edges, class

I fracture of maxillary anteriors. Cosmetic contouring is done to achieve youthful,

feminine characteristics which include rounding of incisal angles, reducing facial

line angles and opening incisal embrasures.

II. Extra Oral Procedures:

Contacts and contours are better maintained by the extra oral procedures

because of better access and visibility.

1. Wax Patterns:

This is usually built in a slightly overcontoured condition, especially at the

contact area to allow for the finishing and polishing surface losses.

Yuodelis et al. (1973) demonstrated that the greater the amount of facal and

lingual bulge of an artificial crown the more the plaque retained at the cervical

margin. In a review of periodontal-prosthetic interactions, Becker and Kaldahl

(1981) gave an opinion that buccal and lingual crown contours should be flat and

not fat usually <0.5mm wider than the CEJ.

Undercontouring than overcontouring of interproximal restorations is

preferred and to place contact areas as far occlusally as possible and furthermore

to make pontics narrow in order to facilitate access for interproximal plaque

control as well as ample space for the interdental papilla.

In a patient whose gingival margins are apical to the cementoenamel

junction, the sulcular morphology differs from that of a healthy patient whose

gingival margins on enamel.

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Wagman has estimated the angle of enamel flare from the CEJ to the

vertical axis of the gingival housing to be approximately 22.5.

As the gingival margin progresses more apically, the sulcus narrows and

the intracrevicular contours of the tooth become the flat contours of the root rather

than the convex surface of the anatomic crown. In this situation the intracrevicular

contours of the artificial crown do not mimic the root but depend on the adjacent

gingival morphology.

Thin gingival responds to irritation by receeding and thick gingiva enlarges,

forms pockets or both.

When intracrevicular margins are adjacent to thin gingiva on the root, the

sulcular contours of the artificial crown should be flat, mimicking the shape of the

root to prevent overcontouring. In the anterior region, the normal facial contours

are reestablished for esthetics, but this flare of the crown is far away from the

gingival margin to avoid plaque accumulation.

Thin gingiva-root relationship with flat emergence of the root from the

gingiva. The same emergence angle reproduced in the artificial crown. Enamel

bulge is added supragingival.

The gingiva adjacent to the flat root surface develops thick free gingival

margin when the underlying bone is thick and often presents with a slight, chronic

marginal gingivitis despite of minimal plaque accumulation. In these situations it

may be advisable to create a thicker intracrevicular crown similar to that of a

natural crown.

Thick gigniva-root relationship with a natural crown and the artificial

crown incorporating the average enamel bulge angle to support the thick gingiva.

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In some cases even the dental floss is incapable of removing plaque from

the concave surfaces, so artificial crown contours and solder joints are created to

accommodate the passage of floss, otherwise gingivitis or periodontitis may result

because of the inability to clean.

2. Cast adjustments:

These are usually done with rubbergy stones incrementally removing cast

material surface wise to obtain the exact dimensions, configuration and

interrelationship of the contact and contour. It is partly done on the working

models and partly or finally intraorally.

CONCLUSION:

Proper reproduction of the size and location of the contact areas to imitate

the natural dentition is essential for the success of treatment and the restoration of

proximal surface. The health of the periodontal tissues is dependent on properly

designed restorations. Overhanging restorations and open interproximal contacts

should be addressed and remedied during the disease control phase of periodontal

therapy.

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REFERENCES:

Dental Anatomy, Physiology, Occlusion – Wheeler’s. 5th edition.

Art and Science of Operative Dentistry – Sturdevant. 4th edition.

Operative Dentistry – Modern Theory and Practice – M.A. Marzouk. 1st

edition.

A Text Book of Operative Dentistry – McGhree. 4th edition.

Advanced Operative Dentistry – Baratieri. 2nd edition.

Text Book of Operative Dentistry – Vimal K. Sikri. 1st edition.

Operative Dentistry – Gillmore. 4th edition.

Fundamentals of Fixed Prosthodontics – Shillngbur__. 3rd edition.

Theory and Practice of Fixed Prosthodontics – Tylman. 8th edition.

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