Dental amalgam has been used in operative Dental amalgam has been used in operative

dentistry for not less than 150dentistry for not less than 150

years. Almost 80% of single tooth years. Almost 80% of single tooth

restorations are fabricated from amalgam,restorations are fabricated from amalgam,

in view of its numerous in view of its numerous advantages, which advantages, which

include:include:

Advantages1- Good adaptability to cavity walls and margins

i.e. provides good seal that prevents: 1) Recurrence of caries. 2) Irritation to dentin and pulp.2- High compressive strength → minimum 80 MN /

m2.3- Low coefficient of thermal expansion when

compared to other restorative materials: → Amalgam → 25 x 10-6. Tooth → 11.5 x 10 -6.

Advantages4- Indestructible in oral fluids → i.e.

maintains marginal seal, proximal contact and contour.

5- Biologically compatible with oral tissues.6- Convenience of manipulation.7- Could take and maintain high surface

polish that increases the strength.8- Low coast.

Disadvantages

4- Thermal conductivity.5- Dimensional changes during setting →

20 / cm.6- Poor esthetic.

Fracture

INDICATIONSINDICATIONS

Amalgam should be considered together Amalgam should be considered together

with posterior composite and cast gold as a with posterior composite and cast gold as a

restorative for classes I, II, the distal surface restorative for classes I, II, the distal surface

of cuspids and class V in posterior teeth. of cuspids and class V in posterior teeth.

Material selection in such cases will depend Material selection in such cases will depend

on:on:

A) THE EXTENT OF THE LESION:A) THE EXTENT OF THE LESION:

The most suitable indication for amalgam The most suitable indication for amalgam

is the small and medium sized class I and is the small and medium sized class I and

II cavities especially those with four walls II cavities especially those with four walls

and a floor, where the amalgam will be and a floor, where the amalgam will be

confined and not subjected to tensile confined and not subjected to tensile

loads.loads.

Extensive lesions especially those Extensive lesions especially those

including undermined cusps will require including undermined cusps will require

cusp capping and tooth supported against cusp capping and tooth supported against

high loads including tensile, where cast high loads including tensile, where cast

gold will serve better.gold will serve better.

B) ESTHETICS:B) ESTHETICS:

For esthetic-conscious patients, amalgam For esthetic-conscious patients, amalgam

will be objectionable particularly in will be objectionable particularly in

conspicuous areas of teeth and posterior conspicuous areas of teeth and posterior

composites may be favored. composites may be favored.

C) CARIES INCIDENCE:C) CARIES INCIDENCE:

Amalgam may be favored if repair or Amalgam may be favored if repair or

remake is likely to include extensions for remake is likely to include extensions for

original cavities and for patients with original cavities and for patients with

moderately high caries incidence; being moderately high caries incidence; being

less costly and having good sealing ability.less costly and having good sealing ability.

D) ECONOMICS:D) ECONOMICS:

Although amalgam restorations cost far Although amalgam restorations cost far less than cast gold restorations yet costing less than cast gold restorations yet costing per se may not be in favor of amalgam in per se may not be in favor of amalgam in the long run if the restoration has to be the long run if the restoration has to be repeatedly be made. Amalgam can also be repeatedly be made. Amalgam can also be used for core build-up under full crowns.used for core build-up under full crowns.

Cavity preparation Cavity preparation

Cavity preparation for amalgam restoration is characterized by: →

CSA 90C. Cavity walls parallel or perpendicular to

the direction of occlusal force. Enough depth to provide bulk to the

material.

Cavity preparation Cavity preparation

If a cusp is undermined and is to be capped with amalgam, it must be reduced minimum of 2 mm, to provide enough bulk of the amalgam enables it to withstand the tensile stresses.

The isthmus area shows: → Minimal bucco-lingual width.

→ Axio-pulpal line angle beveled, rounded or saucerized to provide:

a) Elimination of stress concentration area.

b) Bulk of amalgam.

B) DESIGNS OF CLASS I CAVITY B) DESIGNS OF CLASS I CAVITY PREPARATIONPREPARATION

Cavity preparation for Class I lesions for Cavity preparation for Class I lesions for

amalgam restoration. It may be either:amalgam restoration. It may be either:

A- Class I simple cavity.A- Class I simple cavity.

B- Class I buccal pit cavity.B- Class I buccal pit cavity.

C- Class I extension cavity.C- Class I extension cavity.

These are pit and fissure type cavities that involve the occlusal surfaces of molars and premolars, the occlusal 2/3 of buccal and lingual surfaces of molars, and the palatal pits in maxillary anterior teeth.

Definition:

These are self-cleansable These are self-cleansable areas. However, they may get areas. However, they may get involved by caries due to their involved by caries due to their inherent defective structure inherent defective structure as areas of imperfect as areas of imperfect coalescence of lobes of coalescence of lobes of calcification of these teeth. calcification of these teeth. These areas are retentive for These areas are retentive for food and thus invite caries.food and thus invite caries.

1.1.A small surface opening which may A small surface opening which may remain unnoticed until the lesion remain unnoticed until the lesion becomes of a considerable size.becomes of a considerable size.

2.2.A conical spread in both enamel and A conical spread in both enamel and dentin, with the bases of cones at dentin, with the bases of cones at the Amelo-Dentinal Junction, "A. the Amelo-Dentinal Junction, "A. D."J. D."J.

3.3. Its rapid burrowing at the dento-Its rapid burrowing at the dento-enamel junction. These lesions may enamel junction. These lesions may involve one or more surfaces and involve one or more surfaces and hence a simple or compound cavity hence a simple or compound cavity should be prepared.should be prepared.

These lesions are clinically characterized by:

Designing the Outline Form.Designing the Outline Form.The outline form of a routine class The outline form of a routine class I cavity should describe a I cavity should describe a symmetrical design running in symmetrical design running in sweeping curves along all pits, sweeping curves along all pits, fissures, and angular grooves fissures, and angular grooves between the cusps and with a between the cusps and with a minimum width.minimum width.

Simple occlusal cavities

The mesial and distal The mesial and distal margins are placed margins are placed midway between the midway between the bottom of the proximal bottom of the proximal fossae and the crest of fossae and the crest of the proximal ridges and the proximal ridges and in a direction parallel to in a direction parallel to these ridges.these ridges.

The mesial and distal wall should have a slant or slight divergence from the pulpal floor outward to avoid undermining the marginal ridges.

In a bucco-Iingual direction, the cavity is extended just sufficient to eliminate the defective and susceptible tissues. The lingual and the buccal wail should be parallel to the respective tooth surface.

It must be reemphasized that the outline form for class 1 cavities should be very conservative since they involve cleansable areas.

It is governed only by the extent of caries in both enamel and dentin and the amount of extension or need to eliminate pits and fissures to secure smooth margins.

Again:Again:

The outline form for simple design of Class I cavity preparation should include all carious and undermined enamel, all pits and fissures and extended to area self-cleansable in the shape of multi curves without any

sharp line angles.

Bucco-lingually, it should not extend beyond the

intercuspal line except if there is caries with

minimal width of the cavity about 1/4 - 1/3 the

inter-cuspal distance. Mesio-distally, it should be

extended mid way between the triangular fossa

and the crest of the marginal ridge.

The resistance formThe resistance formAchieved by maximum conservation of sound tooth

structure. Also, considering the amalgam as a brittle

material, cavo-surface

margin configuration of 90oC provides both the

enamel margins and the amalgam restoration with

enough bulk at margins to resist the fracturing forces

Minimal cavity width and providing bulk of the

restoration through a cavity depth at level of 0.2-

0.5-mm beyond the DEJ will provide minimal

surface area of the restoration exposed to the

occlusal loading force with bulk strength

through the depth.

Flat and smooth pulpal floor parallel to the

occlusal plane will help in proper distribution of

occlusal forces and provides stability that deletes

the wedging action of the restoration upon the

tooth structure. Roundation of axial line angles

also eliminates stress concentration.

Retention form:Retention form:

Only retention against axial displacement is

needed in the form of mechanical undercuts

in dentin by converging the cavity walls

occlusally about 5 - 15° from the tooth long

axis.

Convenience formConvenience formIn simple Class I cavity design, no need for

convenience in as it is easily seen and instrumented.

Only, accentuation of cavity walls, line and

point angles and selection of suitable sized

instruments is considered as a satisfactory

convenience.

In small size cavities, the carious In small size cavities, the carious dentin should have been removed dentin should have been removed during making the cavity extensions.during making the cavity extensions.

In moderately deep and deep In moderately deep and deep cavities, the carious dentin is peeled cavities, the carious dentin is peeled off carefully at the sides using large off carefully at the sides using large spoon excavators, and then scooped spoon excavators, and then scooped out in few and large pieces. out in few and large pieces.

Only light pressure in a direction Only light pressure in a direction parallel to that of the pulp is parallel to that of the pulp is utilized. This is continued until a utilized. This is continued until a sound dentin floor is reached.sound dentin floor is reached.

Removal of Carious Dentin

The enamel walls of the cavity should be The enamel walls of the cavity should be finished free from any loose, short, or finished free from any loose, short, or undermined enamel, and trimmed to undermined enamel, and trimmed to meet the tooth surface at a right cavo-meet the tooth surface at a right cavo-surface angle. surface angle.

This may be done by sharp and regular-This may be done by sharp and regular-edged chisels and hatchets, plane fissure edged chisels and hatchets, plane fissure burs, stones, or sand-paper discs. burs, stones, or sand-paper discs.

All sharp corners in enamel must be All sharp corners in enamel must be rounded, as they may contain short rounded, as they may contain short enamel rods.enamel rods.

Planning of Enamel Walls

A sharp explorer is then used to check A sharp explorer is then used to check the details of the prepared cavity and the details of the prepared cavity and to loosen the tooth debris which are to loosen the tooth debris which are then blasted out with warm air.then blasted out with warm air.

Performing of the toilet of the cavity

The outline form is performed by first gaining access through the enamel to the carious dentin floor of the cavity followed by making the necessary cavity extensions.

Procedure

In case of initial carious lesions, In case of initial carious lesions, access is obtained by employing a access is obtained by employing a small small sized round bursized round bur..

In big carious lesions, access is In big carious lesions, access is obtained easily by breaking down obtained easily by breaking down the undermined enamel overlying the undermined enamel overlying the carious dentin, using a the carious dentin, using a suitable size chisel.suitable size chisel.

In either case, access is started at In either case, access is started at the most defective area of enamel, the most defective area of enamel, i.e., a carious pit or fissure.i.e., a carious pit or fissure.

The bur is held at a right The bur is held at a right

angle to the involved angle to the involved surface of, the tooth and surface of, the tooth and light pressure in an in-and-light pressure in an in-and-out direction is exerted. out direction is exerted. Cutting is continued until Cutting is continued until the amelo-dentinal junction the amelo-dentinal junction (A.D.J.) is reached.(A.D.J.) is reached.

The necessary cavity extensions through pits, fissures, and deep developmental grooves are made using an inverted cone bur held at right angle to the surface of the tooth.

The bur is rotated, and carefully introduced through the opening just obtained, so that its weak corners do not touch the enamel and get dulled.

With the bur seated in the cavity With the bur seated in the cavity just below the amelo-dential just below the amelo-dential junction ½ -1 mm. gentle pressure junction ½ -1 mm. gentle pressure is applied in the direction of is applied in the direction of required extension. required extension. During cutting, the bur should be During cutting, the bur should be kept moving in-and-out of the cavity kept moving in-and-out of the cavity and at right angle to the tooth and at right angle to the tooth surface. In this way, the bur will surface. In this way, the bur will undermine and lift the cut enamel, undermine and lift the cut enamel, and at the same time unclog itself.and at the same time unclog itself.

Provision of ample resistance and adequate retention through boxing of the preparation could be obtained.

This is obtained by using a fissure bur held perpendicular to the surface of the tooth. All the line angle in dentin must be squared up hoe excavators.

The outline of these cavities The outline of these cavities usually describes a triangle with usually describes a triangle with its base faming the gingival wall its base faming the gingival wall and its sides forming the mesial and its sides forming the mesial and distal walls. and distal walls.

The gingival wall is placed at or The gingival wall is placed at or slightly occlusal to the height of slightly occlusal to the height of contour of the tooth.contour of the tooth.

Buccal Pit Cavities

All walls are extended just All walls are extended just enough to eliminate enough to eliminate defective enamel and dentin. defective enamel and dentin.

The enamel walls are planed The enamel walls are planed in the direction of enamel in the direction of enamel rods and perpendicular to rods and perpendicular to the axial wall.the axial wall.

Hoe excavators are used to smooth the axial wall and make it parallel with the external surface of the tooth.

It should be re-emphasize that the shape of the cavity will be governed by the extension of caries, accordingly the outline of these cavities may be a rounded or oval in shape.

Class I extension cavity:Class I extension cavity:

• Compound or complex Class I cavity

design is an extension of the occlusal

cavity to buccal or/and lingual surfaces

It is indicated in:It is indicated in:

• 1. Deep caries in buccal or / and lingual pits.

• 2. Deep fissure or groove extended from the occlusal to the lingual or / and buccal surfaces.

• 3. Fissure crossing the oblique ridge in upper molars.

• 4. When the remaining oblique ridge in

upper molars or transverse ridge in lower

premolars is weak (Fig. 4-4, A and B), it is

a must to be included in the cavity outline

to avoid its fracture.

The outline form:The outline form:

• The outline form of compound or complex Class I design is the she same as simple Class I cavity preparation in addition to extension to include the carious or retentive area either buccal or/and lingually.

• It may be extended with step, forming axial wall and

gingival floor, or without step, in

• cases showing extended caries or fissure at the level

of the pulpal floor.

• The formed step will provide inclusion of the carious

or retentive area without

• endangering the pulp.

Resistance form:Resistance form:

• The same features of resistance form as

simple Class I is performed in addition to:

roundation of axio-pulpal line angle to

prevent stress concentration and to

provide bulk to the restoration at this

critical area.

• The axial wall direction should be parallel

to the corresponding external tooth

• surface,

i.e. convex, in order to prevent pulp exposure

and provide uniform thickness of the

restoration.

• Axial retention in the form of mechanical

undercuts in dentin, the same as simple

Class I, in addition to occlusal lock against

lateral displacement. Extension for retention

to the other opposing surface to

• provide lateral retention in extensive cavities.

Convenience form:Convenience form:

• When the cavity design becomes

compound or complex Class I preparation

no need for extra convenience than that of

simple Class I cavity as the extension

portion is also easily seen and reached.

Finishing of enamel wallsFinishing of enamel walls

• The enamel wall should take the same

direction of enamel rods without

undermining or weakening with cavo-

surface margin of 90°.

• The mesial and distal walls of the extension

will be completely parallel to each other and

to the long axis of the tooth,

• while the gingival floor of the extension

portion will be slightly slanting gingivally to

be in the same direction of enamel rods.

Designs of Class II cavityDesigns of Class II cavitypreparationpreparation

• Class II cavity preparation for amalgam restoration mat be:

• 1. Class II compound or complex cavity with proximal step.

• 2. Class II compound or complex cavity without proximal step.

• 3. Class II simple cavity.

1. Class II compound or complex cavity 1. Class II compound or complex cavity with proximal step:with proximal step:

• Compound or complex Class II cavity preparation with step consists of three portions, occlusal, isthmus and proximal portion.

• The isthmus portion is defined as the narrowest connection between the occlusal and proximal portions of class II compound or complex cavity.

• The outline of the isthmus portion should

be extended to involve all the carious

enamel and dentin and place the cavity

margins in area self-cleansable with

freeing of the proximal contact area.

• According to the occlusal anatomy of the

tooth, the position and size of the proximal

contact area and width of the embrasure,

the isthmus outline form may follow one of

the following Ingrham’s lines

• These lines may be straight; in case of small contact area,

• uniform; in case of normal sized contact area .

• or reverse curve; in case of broad or wide contact area.

• The reverse curve outline will be followed in the buccal wall more than the lingual as the contact area is much more shifted buccally.

• The width of the cavity at isthmus should be narrow bucco-lingually as much as possible, about 1/4 the inter-cuspal distance. The occlusal outline is similar to that of Class I cavity preparation

• The proximal outline should be extended

enough to ensure involvement of all carious

enamel and dentin, freeing the proximal

surface out of contact lingually, buccally and

gingivally and placing the cavity margins in

the embrasures to be in area selfcleansable.

• The axial wall is about 0.5 – 0.8-mm away from the DEJ to provide enough bulk of the restoration.

• The axial wall should be in a direction parallel to the external proximal tooth surface, – i.e. it will be either straight or convex to provide

enough uniform bulk of the restoration and protection of the pulp against traumatic exposure.

• It is preferable to complete the proximal outline before breaking the marginal ridge and proximal enamel plate (Proximal ditch cut) (Fig. 4-6,

• 7 and 11, A and B).

This will provide:This will provide:

• 1. A guide to proximal design.

• 2. Protection of the proximal surface of the

adjacent tooth from rotary instrument.

• 3. Save time and effort.

• 4. Reduce heat generation as cutting in

enamel produces much more heat generation.

• 5. Enamel wall in the direction of enamel

rods.

• 6. CSA 90°.

• 7. Freeing of the contact area with maximum

conservation of the tooth structure.

Resistance form:Resistance form:

• Resistance of isthmus portion is achieved by

minimal width of the cavity bucco-lingually about

¼ the inter-cuspal distance.

– This will provide decrease in the surface area of

restoration subjected to the occlusal stresses.

–

• Roundation, beveling or saucerization of

the axio-pulpal line angle, to provide

removal of sharp axio-pulpal line angle

that acts as stress concentration area and

increased bulk of restoration at isthmus

area

• Reverse curve in case of wide proximal

contact area will provide maximum

conservation of the sound tooth structure

during freeing of the contact, removal of all

undermined enamel and correct cavo-

surface configuration of 90°

• Resistance of proximal portion is achieved

by performing cavosurface configuration of

90°.

• The gingival floor should be smooth, flat

and parallel to the pulpal floor and the

occlusal plane.

• The axial wall should be parallel to the

external proximal tooth surface and be at

0.5-0.8-mm away from the DEJ, To

provide uniform bulk of the restoration.

• The buccal and lingual walls should be

parallel to the direction of the

corresponding surfaces to avoid weakening

of cusps.

• In general, the proximal portion should be a

box form.

Retention form:Retention form:

• Axial retention features includes, • 1) mechanical undercuts by preparing the

cavity walls slightly converging occlusally, 2) the inverted truncated cone shape of the proximal portion,

• 3) proximal axial grooves • 4) pin retention in extensive cavities

placed in the gingival floor.

Retention form:Retention form:

• lateral retention features includes • 1) dove tail, which is considered as

extension for retention in premolars, considered extension for prevention that provides retention also in molars

• 2) occlusal lock.• 3) proximal axial grooves.• 4) pin retention in extensive cavities.

• Proximal axial grooves are cut in the axio-

buccal and axio-lingual line angles, in the

expense of buccal and lingual walls rather than

the axial wall to avoid pulp exposure. They

should extend from the gingival floor in occlusal

direction up to the level of the pulpal floor.

• These grooves are wider internally than

externally and wider gingivally than

occlusally.

• They are prepared using small round bur

or small tapered fissure bur

Convenience form:Convenience form:

• Cutting an occlusal cavity is considered as a

convenience form as it provides accessibility to the

proximal portion.

• The axial wall should be parallel to the tooth long

axis in occluso-gingival direction to allow

instrumentation up to the depth of the proximal

portion..

• Also, accentuation of cavity walls and

margins, roundation of line angles and

selection of suitable sized instruments are

important convenience features

Buccal and Lingual Buccal and Lingual ExtensionsExtensions

In case of occluso-buccal and In case of occluso-buccal and occluso-lingual cavities occluso-lingual cavities extensions are made through the extensions are made through the fissures and towards the fissures and towards the respective surfaces. respective surfaces.

The cutting is done in dentin at The cutting is done in dentin at the amelo-dntinal junction using a the amelo-dntinal junction using a #56 bur until the ocdusal ridge is #56 bur until the ocdusal ridge is undermined and removed.undermined and removed.

If the caries is still gingival If the caries is still gingival to the level of the pulpal seat, to the level of the pulpal seat, a step is indicated: a #330 or a step is indicated: a #330 or 56 but is used to cut the 56 but is used to cut the dentin at the amelo-dentinal dentin at the amelo-dentinal junction, applying pressure in junction, applying pressure in a gingival direction and at the a gingival direction and at the same time moving the bur same time moving the bur mesio-distally.mesio-distally.

The enamel thus The enamel thus undermined, is broken down undermined, is broken down with chisels. with chisels.

Retention grooves are then Retention grooves are then cut in dentin along the axio-cut in dentin along the axio-mesial and axio-distal line mesial and axio-distal line angles. The cavity walls and angles. The cavity walls and margins are finished as margins are finished as previously described.previously described.

In case of deeply-seated caries, where removal of the carious dentin will leave a round cavity floor, flattening of which to obtain the required resistance form, will expose the pulp.

The following technique The following technique is used:is used:

a)The cavity floor is covered with a sub base of calcium hydroxide, followed by a base of glass ionomer cement which fills it to the routine cavity depth.