Smooth surface lesions located on the gingival third of labial, buccal and more rarely the lingual surfaces of all teeth.

DEFINITION

Always simple lesions as it involves one surface of a tooth.

Limitations:

11.. Caries is not only the reason of Caries is not only the reason of cavitation, abrasion and erosion cavitation, abrasion and erosion may also responsible for their may also responsible for their causation.causation.

These lesions have the following clinical characteristics:

2. The carious lesion usually starts as a white or chalky line or area near the center of the gingival 1/3 of the labial or buccal surfaces of teeth. If it occurs on the lingual surface, it is usually associated with denture clasps.

33.. Marked sensitivity. Marked sensitivity.

4.4. Tendency to spread mesially Tendency to spread mesially and distally near the axial and distally near the axial angles of teeth, it may pass angles of teeth, it may pass the axial angle of the tooth the axial angle of the tooth and unite with a Class II, III and unite with a Class II, III or IV cavity.or IV cavity.

5. Bell-crowned teeth, and teeth with markedly convex surfaces, are more susceptible to this type of caries.

66.. It occurs less frequently It occurs less frequently than the other types of than the other types of caries.caries.

7. It is usually affects multiple teeth. This indicates that the patient has a high caries susceptibility and requires careful extensions of cavity outline.

8-It is more frequent among old-aged patients and is called senile caries, yet it is not uncommon in childhood and adolescence and is often associated with improper oral hygiene and presence of bacterial plaque. In case of old aged individuals, caries may be found to extend gingivally and affect the cementum of the root. Sensitivity will increase and the caries may tend to recur around the margins in cementum.

Application of Principles:

The Outline Form:

A. General shape:

“Ferrier design, conventional or typical“

This is the most recent and accepted now. Generally the classical Class V cavity usually describe a trapezoidal outline with straight margins and round corners, with the short arm being the gingival.

I. OUTLINE FORM - rounded

trapezoid in gingival 1/3.

Principles Rationale

Conforms to the tooth shape, typical caries location, and site of plaque accumulation.

B. B. Location of marginsLocation of margins

Occlusally:Occlusally: It has to be at, It has to be at, but not including the height but not including the height or just past the height of or just past the height of contour of the tooth or just contour of the tooth or just include the defective area of include the defective area of the tooth.the tooth.

A. Occlusal /incisal outline is straight and parallel to the occlusal plane.

Principles Rationale

More esthetic and harmonious.

Proximally: Far enough mesially and distally to include only the defective and/or the decalcified tooth tissues, yet not encroaching on the axial angles of the tooth, and placed just opposite the axial angles of the tooth.

Gingivally: At or ideally in the occlusal portion of the gingival sulcus space. In cases of gingival recession, the gingival margin should be located supragingivally.

Resistance and Retention Resistance and Retention Forms:Forms:

No resistance form necessary for No resistance form necessary for these preparation because they are these preparation because they are not subjected to a direct functional not subjected to a direct functional loading.loading.

A minimum dept of A minimum dept of 0.5 mm0.5 mm in dentin in dentin is required for a uniform bulk of is required for a uniform bulk of amalgam for strength of the amalgam for strength of the material.material.

a. Resistance Form:

b. Retention Form

For retention, however, as the mandible moves in lateral excursion, the lingual slopes of the buccal and lingual cusps of maxillary teeth load the buccal slopes of the buccal and lingual cusps of mandibular teeth.

Assume that we have a facial Class V restoration in the lower molar tooth, as illustrated in the diagram, and so the tooth is firmly seated in bone, the tooth structure of the crown can move from position (1) to position (2), making a v-shape opening at the margin (usually the occlusal one), together with a facial component of force driving the restoration facially. So, retention will be placed in the occlusal (or incisal) and gingival walls in the form of grooves or retentive holes.

If the occlusal margins approximate the facial or lingual cusps or marginal ridges, it is advisable to make the occlusal walls devoid of any occlusal grooves as this may:

i. undermine the structure of these cusps or marginal ridges.ii. display the restorative through the enamel and, therefore, causes objectionable esthetics.

Although these locations are not mandatory in premolars and in prominent, easily cleansable molar tooth surfaces, locating the margins apical to the height of contour should be decided upon only after carefully considering the cleansing ability and plaque control technique of the patient as well as the natural pattern of cleansing these teeth.

Internal anatomy:

1. In a mesio - distal cross section:

i. The axial wall will be smooth and slightly curved mesiodistally, following the curvature of the facial or lingual surface. This is to provide resistance to the forces of condensation and to provide a maximal pulp protection.

ii.ii. Mesial and distal walls, will Mesial and distal walls, will appear divergent or flare appear divergent or flare mesially and distally mesially and distally respectively, going with the respectively, going with the direction of enamel rods to direction of enamel rods to form form 90°90° cavo-surface angle. cavo-surface angle. This is to provide strength for This is to provide strength for the tooth and the amalgam the tooth and the amalgam margins and to prevent margins and to prevent undermined the enamel walls.undermined the enamel walls.

2. In an occluso - gingival longitudinal section:

i. The axial wall:

Will be seen as flat to slightly convex occluso-gingivally depending on the extent of the preparation occluso-gingivally. This will provide maximal pulp protection, while maintaining a uniform minimum dept of 0.5m in dentine.

ii. Occlusal or incisal wall:

It can appear in one of two ways:

a. Smooth and straight forming a 90° cavo-surface angle following the direction of enamel rods. This is to facilitates condensation and the adaptation of the amalgam restoration and at the same time it prevents undermining of enamel rods.

b. If the occlusal margins is located at,the middle third of the facial or lingual surfaces, it will be formed of two planes; a grooved internal plane, and is made of dentin, and an outer amelo-dentinal plane going with the direction of enamel rods. This will provide a mechanical retention lock in occlusal wall without undermining the enamel rods.

iii. Gingival wall:Also it can vary in appearance, depending on its location, if it is located on enamel, it requires a small cavo-surface bevel. This will protect the very short gingival enamel rods from fracture during condensation and, at the same time, it terminates the gingival wall with its enamel wall going with the direction of the enamel rods, thus, eliminates the unsupported rods.

In such a manner it appears with two planes; an internal grooved plane made of dentinand an outer flat plane made of enamel.

If the gingival wall is located on cementum of the root, it also appears with two planes, an internal grooved plane made of dentin and an outer flat plane made of dentin and cementum.

All internal line angles in dentine All internal line angles in dentine must be squared up except those must be squared up except those on the corners, they must be on the corners, they must be rounded. Also, all point angles rounded. Also, all point angles must be rounded. This is to must be rounded. This is to facilitate condensation of facilitate condensation of amalgam.amalgam.

Convenience form:

The trapesiodal shape with rounded corners and the isolation of the field of operation using the rubber dam will provide a better conveniency for cavity preparation and restoration.

Removal of carious dentine:

As described before.

Finishing of enamel walls Finishing of enamel walls and margins:and margins:

Enamel margins should be Enamel margins should be smoothened and should be smoothened and should be provided with provided with 90°90° cavo-surface cavo-surface angle . The gingival bevel is to angle . The gingival bevel is to be placed on the gingival walls be placed on the gingival walls that are terminated by enamel that are terminated by enamel and not where the preparation and not where the preparation terminates in cementum.terminates in cementum.

Cavity Debridement

As described before.

This Form of the Cavity :This Form of the Cavity :

1.1. Meets the general principles Meets the general principles of cavity of cavity preparation.preparation.

2.2. Exhibits a pleasant Exhibits a pleasant appearance, andappearance, and

3.3. Is easier to restore. Is easier to restore.

Armamentarium

1. Rubber dam , punch , clamp forceps and clamp no. 212.

2. Burs nos. 330 , 256 , 1/2, 1 , 35 .

3. Hand instruments : curved chisel, mon - angle hoe , hand excavator.

Instrumentation Resume for the Class V Preparation

1. No. 256 or 335 bur for penetration and extension of the outline .

2. Axial wall located with the same burs.3. If required , caries is removed with a

slow - speed round bur , as dictated by convenience .

4. Hand excavator may be advised.5. Gingival and incisal retention placed

with no. ¼ or ½ bur.6. Enamel is finished and beveled with a

no. 15 Wedelstaedt chisel and 7901 or 242 bur.

B. Gingival outline is straight and parallel to the occlusal outline.

Principles Rationale

Will allow maximum retention to be placed in cavity walls if occlusal and gingival outlines are parallel.

C. Mesial and distal outline is straight and parallel to the mesial and distal tooth outline in the gingival 1/3.

Principles Rationale

Conforms to the shape of the tooth.

II. Extensions

Conservation of tooth structure is the basis for all cavity preparation; therefore, extend only far enough to remove defective tooth structure and create sufficient access (convenience form) for instrumentation and insertion of restorative material. In addition, access for finishing and maintenance of the restoration must be provided.

A. Circumscribe 1. Decay,

decalcification, and defects.

2. Enamel unsupported by dentin.

3. Eroded, abraded areas.

4. Existing restorations

Principles Rationale

Eliminates weak or defective tooth structure so that margins of the restoration will terminate on sound tooth structure (extension for prevention).

B. Occluso-gingival B. Occluso-gingival extensionsextensions

1.1. Occlusally to the Occlusally to the height of contour (or height of contour (or to the occlusal to the occlusal extent of the lesion)extent of the lesion)

2.2. Gingivally to the Gingivally to the gingival extent of gingival extent of the lesion the lesion (frequently (frequently subgingivally near subgingivally near the C.E.J.)the C.E.J.)

Principles Rationale

Provides sufficient access for instrumentation and condensation and for prevention.

C. Mesio-distal extention is to the line angles of the tooth (or to the extent of the lesion mesially and distally).

Principles Rationale

Extention for prevention, more esthetic and harmonious.

III. RESISTANCE/RETENTION FORM

A. Depth 1. 0.5 mm in dentin 2. 1-1.25 mm (may

vary slightly depending on size of tooth, thickness of enamel and extensions); occlusally 1.5 – 1.75 mm depth may be required to achieve 0.5 mm in dentin.

A minimum depth is required to provide retention and uniform bulk of amalgam for strength of material – further tooth reduction is unnecessary and may result in pulpal encroachment or sensitivity.

Principles Rationale

B. Axial Wall 1. Smooth 2. Slightly curved

mesiodistally. 3. Straight or slightly

curved occlusogingivally depending on the extent of the preparation occlusogingivally.

Principles Rationale

Easier to adapt amalgam to smooth walls provides resistance to forces of condensation and provides maximumal pulpal protection while maintaining uniform minimum depth (0.5 mm in dentin).

C. Mesial and distal C. Mesial and distal wallswalls

1.1. Smooth and Smooth and straight straight occlusogingivally.occlusogingivally.

Principles Rationale

Facilitates condensation, adaption.

2. Flare mesially and distally respectively to form 900 metal margins).

Principles Rationale

provides strength for the tooth and amalgam margins (prevents undermined enamel and provides a 700 - 900 amalgam margin) – Resistance form.

D. Occlusal or incisal wall

1. Smoothly and straight mesiodistally.

Principles Rationale

Facilitates condensation, adaption.

2. Forms a 900 cavosurface angle (occlusal wall is parallel to the enamel rods – 900 to a tangent to the external surface).

Principles Rationale

Prevents undermining of enamel rods, assists in providing retention by opposing the gingival wall which forms an acute gingivocavosurface angle.

3. Occlusal retention – two undercuts .5 mm deep in the dentin of the occlusal wall at the occluso-axial line angle (one mesially and one distally)

Principles Rationale

Provides retention – a mechanical lock in occlusal wall without undermining enamel rods.

E. Gingival wall

1. Smooth and straight mesiodistally.

Principles Rationale

Facilitates condensation, adaption.

2. Gingival retention – an acute axio-gingival angle (700).

Principles Rationale

Provides mechanical lock to retain the amalgam (primary retention).

3. If terminated on enamel requires a small cavosurface bevel.

Principles Rationale

A small enamel bevel protects the very short gingival enamel rods from fracture during condensation, and eliminates unsupported rods.

A. Line AnglesA. Line Angles 1.1. Axial line Axial line

angles are well angles are well defined and defined and conform to the conform to the configuration of configuration of the cavosurface the cavosurface outline form outline form (internal (internal outline).outline).

Principles Rationale

IV. CAVITY FINISH

Increase retention

2. Mesio – occlusal, mesio-gingival, disto-occlusal, and disto-gingival walls form rounded line angles.

Principles Rationale

Facilitates condensation.

B. Point angles are rounded

Principles Rationale

Facilitates condensation

C. C. Cavosurface Cavosurface marginsmargins

1.1. Well defined Well defined

2.2. Strong Strong (sound)(sound)

Principles Rationale

Well defined, sound cavosurfaces are required to resist condensation forces and produce a well adapted, durable tooth restoration margin which will resist plaqueaccumulation and prevent recurrent caries.

D. Cleanliness - the cavity must be free of moisture and debris.

Principles Rationale

a clean, dry cavity preparation will allow more intimate adaptation of amalgam to the cavity walls. An amalgam which is placed in a dry environment will have superior physical properties to one placed in a moist environment.

Principles Rationale

V. TISSUE/DAM PRESERVATION

A. The rubber dam is intact.

damage of the dam will cause leakage and loss of isolation (moisture contamination).

B. Surrounding enamel, dentin, and cementum are preserved undamaged.

Principles Rationale

conserves natural tooth structure eliminates post-operative pain inflammation.

C. Soft tissue undamaged.

Principles Rationale