CL II,III Amalgam Restoration _5,6

CL II Amalgam Restoration

Dr. Samira J. Juhi Tarfa

RESTORATIVE AND COSMETIC DENTISTRY

CL II Amalgam Restoration
Dr. Samira J. Juhi Tarfa

Two surfaces cavity for posterior teeth.

Three surfaces cavity for posterior teeth.
Four surfaces( or more) cavity for posterior teeth.

CL II Amalgam Restoration

Width of facio-lingual walls of the cavity should be ¼ I.C.D.

Preserving the marginal ridge strength (2mm thickness marginal ridge)
The depth of the preparation into dentin should be 1.5-2mm.
The extent of the caries lesion affects the outline form of the proposed tooth preparation( extent to sound tooth structure).
Ideal outline includes all pits and fissures even if its sound to prevent them from caries in the future ( extension for prevention).
Step 1 :Outline Form and Initial Depth:





The shape of the cavity that prevent fracture of the remaining tooth structure this includes:
Factors prevent fracture of tooth
The facio-lingual width of preparation not exceed ¼ I.C.D.
Removal of unsupported E. by making margin (90°-110°).
Smooth pulpal floor and gingival seat to prevent stress concentration area.
Mesial and distal walls of the cavity should be parallel and slightly diverge occlusally.


Step 2: Resistance Form

• .All the internal line angle should be rounded to prevent stress concentration area.

Preventing fracture of restoration

• The margins or cavosurface line angle should be 90°-110° if more than this lead to fracture of restoration.
• Facio-lingual width should be ¼ ICD .
• Occlusal amalgam should have thickness of 1.5-2 mm to resist fracture during function.





The shape of the cavity that permits the restoration to resist displacement through the tipping or lifting force.
To provide this:
1-Facial and lingual walls should be parallel or converge occlusally 5°.
2. Pulpal floor and gingival seat of the cavity should be flat.
3. The ooclusal convergence of the box.
4.Retentive grooves or locks in the axiofacial and axiolingual line angle.


Step 3: Retention form

5.Dove-tail preparation to increase retention.

The shape or form of the preparation that provides for adequate:

Observation,
Accessibility,
Ease of operation in preparing and restoring the tooth.
Step 4: Convenience Form


Deep dentinal caries can be removed by using spoon excavator or large round bur with slow speed hand piece.
Step 5: Removal of Remaining caries

Involve making the wall smooth and removing of unsupported enamel.

Step 6: Finishing Enamel Walls

Removal of all debris by washing the cavity and drying it.

Step 7: Clean the preparation

The occlusal outline form of CL II tooth preparation is similar to that for CL I

Enter the pit nearest the involved proximal surface using 245 no. bur.
The long axis of the bur and the long axis of tooth crown should remain parallel during cutting .
The bur should be rotating when applied to the tooth and should not stop rotating until removed.
Proper depth of the initial entry cut is 1.5-2mm.


CLINICALLYOcclusal outline form (occlusal step)

Move the bur to extend the out line to include the central groove and the opposite pit which provided by dovetail retention form the isthmus width should be as narrow as possible and not wider than 1/4ICD.

The Objectives for extension of proximal margins are to:

1. Include all caries, faults or existing restorative material.
1.Remove unsupported enamel.
3.Establish not more than 0.5 mm clearance with the adjacent proximal surface facially, lingually, and gingivally.
Proximal out line form preparation

The initial procedure in preparing the outline form of the proximal box is the isolation of the proximal enamel by the proximal ditch cut.
1.Place the bur over the DEJ in the pulpal floor near the remaining marginal ridge, allow the end of the bur to cut the ditch gingivally then move the bur facially and lingually along the DEJ this lead to create axial wall.
2. The ditch should extended gingivally beyond the caries or the proximal contact area.
3. The location of final proximal margin should be established with hand instruments (chisel, hatchets, gingival margin trimmers).

CL III Amalgam RestorationDr. Samira J. Juhi Tarfa

Indications
It is generally reserved for the distal surface of maxillary and mandibular canines if :
• The preparation is extensive with minimal facial involvement.
• The gingival margin primarily involves cementum.
• Moisture control is difficult.

Contraindications

In esthetically important areas proximal surfaces of incisors and mesial surface of canines.

Advantages

• Amalgam restorations are stronger than other Cl III direct restorations.
• Easier to place.
• Less expensive to the patient.
• Easier to finish and polish with out damage to adjacent surfaces.

Disadvantage

1.Metallic color.
2.Less conservative cavity preparation.

OUT LINE FORM

1.The outline form of Class III amalgam preparation may include only the proximal surface.
2.A lingual dovetail may be indicated if one existed or if additional retention is needed for a larger restoration.

Resistance form

It is provided by
• 1.Cavosurface and amalgam margins of 90 °.
• 2. Removal of unsupported enamel.
• 3. Sufficient bulk of amalgam ( minimal 1 mm thickness).
• 4.Round internal angles.
• 5. Conserve the disto-incisal tooth structures as possible .

Retention Form

• 1.The box like preparation form.
• 2. Gingival groove, incisal cove, and sometimes a lingual dovetail.

Tooth Preparation

• A lingual access preparation on the distal surface of the maxillary canine may be indicated if the lesion is more facial than lingual.
• 2.Bur size selection depends on the size of the lesion, bur options may include a no. 2 or smaller round bur.
• 3. The bur is positioned so that its long axis is perpendicular to the lingual surface of the tooth.
• 4.Initial axial depth 0.5 mm inside the DEJ or 0.75 mm axial depth when the gingival margin is on the root surface.

Infected dentin that is deeper than this limited initial axial depth is removed later during final tooth preparation.
5. The gingival retention groove is prepared by placing a no. 14 round bur rotating at low speed in the axio-facio-gingival point angle, it is positioned in the dentin to maintain 0.2 mm of dentin along the axio-gingival line angle.

If a lingual dovetail is needed

• -It is prepared only after initial preparation of the proximal portion has been completed. Otherwise, the tooth structure needed for the isthmus between the proximal portion and dovetail may be removed when the proximal outline form is prepared.
• -The lingual dovetail should be conservative, generally not extending beyond the mesio-distal midpoint of the lingual surface.
• -The axial depth of the dovetail should approximate 1 mm.