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. J.D." J.D."

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.

The resistance form here consists The resistance form here consists chiefly of a pulpal wall parallel to chiefly of a pulpal wall parallel to the occlusal plane with dentin the occlusal plane with dentin walls at right angles to it., i.e. walls at right angles to it., i.e. Boxing the preparation. Boxing the preparation.

The form of this cavity provides The form of this cavity provides automatically for effective automatically for effective retention and, therefore, no special retention and, therefore, no special retentive features are required.retentive features are required.

Obtaining the Resistance and Retention Forms

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

Performing of the toilet of the cavity

Armamentarium

High speed handpiece Burs #330, 56 HoeHatchet R&L Wedel staedt chisel

Operative Procedures

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 pear but #330.small pear but #330.

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 the most defective area of enamel, i.e., a carious pit or enamel, i.e., a carious pit or fissure.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 a #330 pear 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 1/z-1 mm. gentle pressure junction 1/z-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 #56 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 The gingival wall is placed at or slightly occlusal to the height or slightly occlusal to the height of contour of the tooth.of 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 The enamel walls are planed in the direction of planed in the direction of enamel rods and enamel rods and perpendicular to the axial perpendicular to the axial wall.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.

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 the amelo-dntinal junction using a #56 bur until the ocdusal ridge a #56 bur until the ocdusal ridge is undermined and removed.is 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.

b)A ledge is cut on the expense of the buccal and lingual side walls of the cavity for obtaining the required resistance in sound dentin.

I. OUTLINE FORM – Smooth flowing, regular curves.

Angular irregularities in the outline are susceptible to fracture during condensation – a smooth flowing outline is easier to visualize and carve following condensation.

PrinciplesRationale

II. EXTENSIONS – Conservation of tooth structure is the basis for all cavity preparations in order to preserve the strength of the tooth.

However, sufficient extension of cavity preparations is necessary to ensure access (convenience form) for instrumentation, removal of defective tooth structure, insertion and finish of the restorative material, and maintenance of the restoration (prevention).

A. Extensions circumscribe:

1. Caries and decalcifications

2. Enamel unsupported by sound dentin

3. Pits and fossae

4. Major fissures and grooves

5. Existing restorations

eliminates defective tooth structure and eliminates areas (pits, fissures, etc.) which are susceptible to recurrent caries and facilities oral hygiene procedures (extension for prevention).

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B. Bucco – lingual extension

1. Extend fully in areas of buccal and lingual grooves to terminate on smooth surfaces.

to allow a smooth tooth-restoration margin to be created (easier to finish and keep clean).

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2. Extend minimally in areas of triangular ridges (optimal isthmus width is ¼ intercuspal distance or less) terminating on smooth surfaces.

to preserve the strength and function of the cups while eliminating susceptible grooves or defective tooth structure (must be wide enough to allow condensation).

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C. Mesio-distal extension

1. Stop short of the marginal ridge crest.

2. Parallel the contour of the marginal ridge.

to preserve strength of marginal ridges.

to preserve a uniform bulk (strength) to the mariginal ridges.

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3. Groove extensions are kept narrow (mesio-distally) where possible (consistent with access for condensation and outline form), terminating on smooth tooth structure.

to preserve strength of cusps while eliminating susceptible grooves and/or defective tooth structure (must be at least as wide as the narrowest condenser).

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4. If marginal ridge is unsupported or very thin it should be included, resulting in a Class II preparation.

If not included the marginal ridge may fail (amalgam will be stronger than the unsupported enamel)

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A. Depth = ½ mm into dentin (approx. 2 mm measured at triangular ridges).

Minimum depth is required to provide sufficient bulk to prevent fracture and retain the amalgam.

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III. RESISTANCE/ RETENTION FORM

B. Pulpal floor

1. Smooth and flat

2. Parallel to the occlusal plane

Uniform thickness of restorative material.

resists occlusal stress (resistance form) and forces of condensation.

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C. Buccal and lingual walls

1. Smooth and curved mesio-distally.

2. Smooth and straight pulpo-occlusally.

Facilitates adaptation of amalgam and elimination of weak tooth structure.

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3. Converge slightly pulpo-occlusally in areas of triangular ridges (60).

To provide mechanical lock or retention to the occlusal portion and crate bulk at the margins.

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4.Diverge slightly pulpo-occlusally in buccal and lingual groove extensions (60).

protects buccal and lingual surfaces from being undermined (RESISTANCE FORM).

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D. Mesial and distal wall

1. Smooth and straight

facilitates adaptation of amalgam and elimination of weal tooth structure.

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2. Diverges slightly pulpo-occlusally (forms an obtuse angle with pulpal floor).

protects marginal ridge form being undermined or weakened (enamel must be supported be dentin)

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IV. CAVITY FINISH

A. Pulpo-occlusal line angle is well defined (no point angles are present) and follows general configuration of cavosurface outline.

increases retention of the amalgam restoration and preparation is more easily visualized.

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B. Cavosurface margins

1. Sharp (well defined)

2. Sound (well supported)

easier to visualize and carve.

provides marginal integrity.

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C. Cleanliness – cavity is free of debris and moisture.

facilitates adaptation of amalgam to the cavity and improves the physical properties of the restoration by elimination of void or foreign material.

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V. TISSUE RESERVATION

A. Rubber dam is intact

B. Adjacent tooth structure and restorations are intact

C. Adjacent soft tissue (perio-dontium) is intact

preserves isolation, eliminates moisture.

conservation of tooth structure.

prevention of post-operative pain and inflammation.

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