class v amalgam cavity

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

DEFINITION

Always s imple le s ions a s i t involve s one sur face of a tooth.

Limitations:

11 .. Carie s i s not only the rea son of cavi tat ion, Carie s i s not only the rea son of cavi tat ion, abra s ion and eros ion may al so re spons ib le for abra s ion and eros ion may al so re spons ib le for the ir causa t ion.the ir causa t ion.

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 sens i t iv i ty. Marked sens i t iv i ty.

4.4. Tendency to spread mes ia l ly and di s ta l ly Tendency to spread mes ia l ly and di s ta l ly near the axia l angle s of tee th , i t may near the axia l angle s of tee th , i t may pas s the axia l angle of the tooth and pas s the axia l angle of the tooth and uni te wi th a Cla s s II, III or IV uni te with a Cla s s II, III or IV cavi ty.cavi ty.

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

66 .. It occur s le s s fr equent ly than the other It occur s le s s fr equent ly than the other type s of car i e s .type s of car i e s .

7 . It i s usual ly af f ec t s mult ip le tee th . Thi s indicate s that the pat ient has a high car ie s su scept ib i l i ty and require s care fu l extens ions of cavi ty out l ine .

8-It i s more f requent among old-aged pat ient s and i s ca l led s eni le car ie s , yet i t i s not uncommon in chi ldhood and adole s cence and i s of ten as soc ia ted with improper ora l hygiene and pre s ence of bacter ia l plaque. In ca se of old aged individual s , car ie s may be found to extend gingival ly and af f ec t the cementum of the root . Sens i t iv i ty wil l increas e and the car ie s may tend to recur around the margins in cementum.

Application of Principles:

The Outline Form:

A. General shape:

“Ferr ier de s ign, convent ional or typica l “

This i s the most recent and accepted now. General ly the c la s s i ca l Clas s V cavi ty usual ly de s cr ibe a trapezoidal out l ine with s t ra ight margins and round corner s , with the short arm be ing the gingival .

I. OUTLINE FORM - rounded trapezoid in gingival 1/3.

Principles Rationale

Conforms to the tooth shape, typical car ie s locat ion, and s i te of plaque accumulat ion.

B. B. Location of Location of marginsmargins

Occlusa l ly:Occlusa l ly: It has to be at , but not It has to be at , but not inc luding the he ight or jus t pas t the inc luding the he ight or jus t pas t the he ight of contour of the tooth or jus t he ight of contour of the tooth or jus t inc lude the de fec t ive area of the tooth.inc lude the de fec t ive area of the tooth.

A. Occlusal / inci sal out l ine i s s t ra ight and paral l e l to the occ lusal p lane .

Principles Rationale

More e s the t ic and harmonious .

Proximally: Far enough mesial ly and distal ly to include only the defective and/or the decalcified tooth t issues, yet not encroaching on the axial angles of the tooth, and placed just opposite the axial angles of the tooth.

Gingival ly : At or ideal ly in the occlusal portion of the gingival sulcus space. In cases of gingival recession, the gingival margin should be located supragingival ly.

Resistance and Retention Resistance and Retention Forms:Forms:

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

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

a . Resistance Form:

b. Retention Form

For retention, however, as the mandible moves in lateral excursion, the l ingual s lopes of the buccal and l ingual cusps of maxi l lary teeth load the buccal slopes of the buccal and l ingual cusps of mandibular teeth.

Assume that we have a facial Class V restoration in the lower molar tooth, as i l lustrated in the diagram, and so the tooth is f irmly 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 (usual ly the occlusal one), together with a facial component of force driving the restoration facial ly. So, retention wil l be placed in the occlusal (or incisal) and gingival wal ls in the form of grooves or retentive holes.

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

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

Although the s e locat ions are not mandatory in premolar s and in prominent , ea s i ly c leansable molar tooth sur face s , locat ing the margins apica l to the he ight of contour should be dec ided upon only af t er care fu l ly cons ider ing the c leans ing abi l i ty and plaque control technique of the pat ient a s wel l a s the natural pat tern of c leans ing the s e tee th .

Internal anatomy:

1. In a mesio - distal cross section:

i. The axial wal l wi l l be smooth and sl ightly curved mesiodistal ly, fol lowing the curvature of the facial or l ingual surface. This is to provide resistance to the forces of condensation and to provide a maximal pulp protection.

i i .i i . Mesial and distal wal ls, wi l l Mesial and distal wal ls, wi l l appear divergent or f lare mesial ly appear divergent or f lare mesial ly and distal ly respectively, going and distal ly respectively, going with the direction of enamel rods with the direction of enamel rods to form to 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 wal ls.undermined the enamel wal ls.

2. In an occluso - gingival longitudinal

section: i. The axial wall:

Will be seen as f lat to sl ightly convex occluso-gingival ly depending on the extent of the preparation occluso-gingival ly. This wil l 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 fol lowing the direction of enamel rods. This is to facil itates 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 l ingual surfaces, it wil l 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 wi l l provide a mechanical retention lock in occlusal wal l 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 wil l protect the very short gingival enamel rods from fracture during condensation and, at the same time, it terminates the gingival wal l with its enamel wal l going with the direction of the enamel rods, thus, el iminates the unsupported rods.

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

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

All internal l ine angles in dentine All internal l ine angles in dentine must be squared up except those on must be squared up except those on the corners, they must be rounded. the corners, they must be rounded. Also, al l point angles must be Also, al l point angles must be rounded. This is to facil itate rounded. This is to facil itate condensation of amalgam.condensation of amalgam.

Convenience form:

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

Removal of carious dentine:

As described before.

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

Enamel margins should be Enamel margins should be smoothened and should be provided smoothened and should be provided with with 90°90° cavo-surface angle . The cavo-surface angle . The gingival bevel is to be placed on the gingival bevel is to be placed on the gingival wal ls that are terminated by gingival wal ls that are terminated by enamel and not where the preparation enamel 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 of Meets the general principles of cavity cavity preparation.preparation.

2.2. Exhibits a pleasant appearance, Exhibits a pleasant appearance, andand

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

Preparation1. No. 256 or 335 bur for penetration and

extension of the outl ine .2. Axial wal l 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 f inished and beveled with a

no. 15 Wedelstaedt chisel and 7901 or 242 bur.

B. Gingival outl ine is straight and paral lel to the occlusal outl ine.

Principles Rationale

Will al low maximum retention to be placed in cavity walls if occlusal and gingival outl ines are paral lel .

C. Mesial and distal outl ine is straight and paral lel to the mesial and distal tooth outl ine in the gingival 1/3.

Principles Rationale

Conforms to the shape of the tooth.

II. Extensions

Conservation of tooth structure is the basis for al l 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 f inishing and maintenance of the restoration must be provided.

A. Circumscribe 1. Decay, decalcif ication,

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 wil l terminate on sound tooth structure (extension for prevention).

B. Occluso-gingival B. Occluso-gingival extensionsextensions

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

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

Principles Rationale

Provides sufficient access for instrumentation and condensation and for prevention.

C. Mesio-distal extention is to the l ine angles of the tooth (or to the extent of the lesion mesial ly and distal ly).

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

sl ightly depending on size of tooth, thickness of enamel and extensions); occlusal ly 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 sensit ivity.

Principles Rationale

B. Axial Wall 1. Smooth 2. Slightly curved

mesiodistal ly. 3. Straight or sl ightly curved

occlusogingival ly depending on the extent of the preparation occlusogingival ly.

Principles Rationale

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

C. Mesial and distal C. Mesial and distal wal lswal ls

1.1. Smooth and straight Smooth and straight occlusogingival ly.occlusogingival ly.

Principles Rationale

Facilitates condensation, adaption.

2 . Flare mesial ly and distal ly respectively to form 90 0 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 wal l

1. Smoothly and straight mesiodistal ly.

Principles Rationale

Facil itates condensation, adaption.

2. Forms a 90 0 cavosurface angle (occlusal wal l is paral lel to the enamel rods – 90 0 to a tangent to the external surface).

Principles Rationale

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

3. Occlusal retention – two undercuts .5 mm deep in the dentin of the occlusal wal l at the occluso-axial l ine angle (one mesial ly and one distal ly)

Principles Rationale

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

E. Gingival wal l 1. Smooth and

straight mesiodistal ly.

Principles Rationale

Facil itates condensation, adaption.

2. Gingival retention – an acute axio-gingival angle (70 0).

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 el iminates unsupported rods.

A. Line AnglesA. Line Angles 1.1. Axial l ine angles Axial l ine angles

are well defined are well defined and conform to the and conform to the configuration of configuration of the cavosurface the cavosurface outl ine form outl ine form (internal outl ine).( internal outl ine).

Principles RationaleIV. CAVITY FINISH

Increase retention

2. Mesio – occlusal, mesio-gingival, disto-occlusal, and disto-gingival wal ls form rounded l ine angles.

Principles Rationale

Facil itates condensation.

B. Point angles are rounded

Principles Rationale

Facilitates condensation

C. C. Cavosurface Cavosurface marginsmargins

1.1. Well defined Well defined

2.2. Strong (sound) Strong (sound)

Principles Rationale

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

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

Principles Rationale

a clean, dry cavity preparation wi l l al low more intimate adaptation of amalgam to the cavity walls. An amalgam which is placed in a dry environment wi l l 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 wil l cause leakage and loss of isolation (moisture contamination).

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

Principles Rationale

conserves natural tooth structure el iminates post-operative pain inflammation.

C. Soft t issue undamaged.

Principles Rationale