CHAPTER 15: CLASS III & V AMALGAM RESTORAT

Class III amalgam restorations.

are indicated to restore defects located on the proximal surface of anterior teeth that do not affect the incisal edge.

Class III amalgam use is rare, often replaced by composites.

INDICATION of Class III amalgam restorations.

Can be used in Distal surface of canines. Extensive preparation with minimal facial involvement
Gingival margin primarily involves cementum

Used when moisture control is difficult.

Class V amalgam restorations.

Class V restorations are indicated to restore defects on the facial or lingual cervical one third of any tooth
Class V restorations are technique-sensitive due to location and access.

Used for cervical and root caries.
Common in patients with gingival recession or reduced salivary flow.
May require surgical flap for deep gingival lesions.

INDICATION of Class V amalgam restorations.

Non-esthetic areas
Deep gingival caries with limited access.
Used when moisture control is difficult

Pre-wedging in gingival embrasure

better protection of soft tissue and the rubber dam,

2.better access because of the slight separation of teeth

3.better re-establishment of the proximal contact.

Tooth Preparation for Class III Amalgam Restorations

Distal surface of maxillary canine via lingual access
For esthetic reason, Amalgam best when lesion can be approached from lingual
A facial approach for a mandibular canine may be indicated, if lesion is facial & less visible
The outline form of the Class III amalgam preparation may include only the proximal surface.
Lingual dovetail may be added if:

Previously existed, or
Extra retention needed for large restoration

INITIAL TOOTH PREPARATION

Bur selection: No. 2 round bur or No. 330 bur
The bur is positioned perpendicular to the lingual surface of the tooth, but angled mesially toward adjacent tooth Penetration through enamel positions the bur so that additional cutting isolates the proximal enamel affected by caries

Initial axial depth:
0.5–0.6 mm inside DEJ (enamel margin)
0.75–0.8 mm axial depth if gingival margin on cementum

0.5–0.6 mm inside DEJ (enamel margin)

0.75–0.8 mm axial depth if gingival margin on cementum

Finalizing Initial Preparation: No. 1⁄2 round bur used

toTo accentuate the axial line angles, particularly the axiogingival angle.
Facilitates the placement of retention grooves and leaves the internal line angles slightly rounded. Rounded internal preparation angles

To smooth any roughened, undermined enamel produced at the gingival and facial cavosurface margins

Incisal margin often inaccessible to bur without marring the adjacent tooth
Further finishing of the incisal margin is presented later. At this point, the initial tooth preparation is completed.

Small Lesions (Outline Features)

Facial margin: extend 0.2–0.3 mm into facial embrasure (if needed) with a curved outline from the incisal to the gingival margin (resulting in a less visible margin). Lingual outline: smooth curve, minimal lingual wall Cavosurface margin: 90°

Facial, incisal, gingival walls meet axial wall at ~90°
Axial wall: uniform depth, follows external tooth contour

Incisal & Gingival Extensions

Incisal extension to remove carious tooth structure may eliminate the proximal contact
Preserve distoincisal enamel to reduce fracture risk When possible, it is best to leave the incisal margin in contact with the adjacent tooth.

When preparing a gingival wall that is near the level of the rubber dam or apical it is best to use wedge

Final Tooth Preparation

Remove remaining infected dentin

Protect the pulp
Develop secondary resistance & retention forms Finish external walls for strong margins
Clean, inspect, and desensitize/bond cavity

Any infected dentin left on the axial wall should be

Slow-speed round bur (No. 2 or No. 4)
Spoon excavator (as needed)
Careful, controlled removal helps avoid pulpal exposure

Resistance Form for Class III Amalgam Restorations.

90° cavosurface and amalgam margins
2. Enamel walls supported by sound dentin

3. Sufficient amalgam bulk (minimum 1 mm thickness)

4. Rounded internal line angles (no sharp corners)

Primary Retention

box-like cavity preparation

Secondary Retention:

Gingival groove
Incisal cove
Lingual dovetail (if needed for additiona retention)

Gingival Retention Groove

Instrument:
No. 1/4 round bur, low speed

Placement:

Bur positioned at the axio-facio-gingival point angle

Groove prepared in dentin, leaving 0.2 mm of dentin between

groove and DEJ Technique:

Bur rotated and moved lingually along axiogingival line angle

Cutting angle should bisect gingival & axial walls Direction:

Gingival grooves is slightly more gingival than axial
Incisal (occlusal) groove would be slightly more incisal than axial

Gingival Coves

Used when less retention form is needed Two small coves instead of a continuous groove

One at axio-gingivo-facial point angle

One at axio-gingivo-lingual point angle Instrument: No. 1/4 round bur (0.5 mm diameter)

Depth: 0.25 mm (half bur diameter)

Must avoid:

Removing dentin that supports gingival enamel prevents enamel fracture

Placing groove only in axial wall
ineffective retention & possible pulpal risk

Incisal Retention Cove

Location: Axio-facio-incisal point angle Instrument: No. 1/4 round bur in dentin Depth: ~0.25 mm (half bur diameter) Direction: Into incisal point angle Precautions:

Avoid undermining enamel Maxillary canine palm-and- thumb grasp to direct bur incisally

Lingual Dovetail

Not required for small/moderate restorations
Used in large Class III with excessive incisal extension
May be unnecessary if incisal retention is adequate

Preparation Steps:
Prepared after proximal portion is complete
Conservative: generally not beyond mesiodistal midpoint of lingual surface
Axial depth ≈ 1 mm, axial wall parallel to lingual surface (in enamel or dentin)
Instrument: No. 245 bur

Positioned in proximal portion, angled perpendicular to lingual surface
Moved mesially to most mesial extent of dovetail
Then moved incisally & gingivally create incisogingival dimension (~2.5 mm)

Incisal & gingival walls of isthmus: smooth curves connecting dovetail to proximal outline

A. Bur position at correct depth and angulation to begin cutting.
B, Initial cut in beginning dovetail.
C, Bur moved to most mesial extent of dovetail.

D, If possible, cutting should not extend beyond the midlingual position.
E, Bur cutting gingival extension of the dovetail.
F, Incisal and gingival extensions of the dovetail.

G, Completing the isthmus. The proximal and lingual portions are connected by the incisal and gingival walls in smooth curves.
H, Completed lingual dovetail.

Beveling & Line Angle Rounding

Instrument: Gingival Margin Trimmer
Used to bevel (round) the axiopulpal line angle (junction of proximal & dovetail)

• Increases strength of restoration at junction • Provides bulk of amalgam
• Reduces stress concentration

Dovetail Retention Cove

Lingual convergence of dovetail walls (No. 245

bur)
• If dovetail axial wall is in dentin:

- Add retention coves (one incisal, one gingival)

- Prepared with No. 1/4 round bur
- In dentin that does not support lingual

enamel
• May require deepening axial wall

dentin desensitizer

over the prepared tooth structure before placing amalgam is generally recommended. The dentin desensitizer is rubbed onto the prepared tooth surface for 30 seconds and excess moisture is removed without desicating the dentin.

MATRIX PLACEMENT

Wedged, rigid material–supported sectional matrix is suitable for Class III amalgam restorations.

Typically inserted from the lingual aspect.

Matrix Dimensions:

Length: 5/16 inch (8 mm) wide
Thickness: 0.002 inch (0.05 mm) stainless steel
Should cover one-third of the facial surface and extend through the proximal to the lingual surface.

Lingual Trimming:

Trim lingual portion at an angle matching the lingual surface slope to avoid blocking access during amalgam insertion.

Matrix Contouring:

Burnish on a resilient paper pad to create desired contact and contour.

Matrix Placement:

Place in position and wedge from the larger embrasure (facial or lingual).

Stabilize facial and lingual portions with a rigid material.

Precontoured Matrices:

May be used if their contour matches the proximal surface.

Support Material:

If preparation is small and matrix is rigid enough, additional support may not be needed.

Proper Isolation of class V resto is Critical during

Caries removal
Liner application
Amalgam insertion and carving
Moisture negatively impacts visual assessment, pulp protection, and material properties.

Class V Challenges

Gingival margin often lies apical to gingival crest. Requires gingival retraction to:

Provide access
Prevent sulcular fluid seepage Protect free gingiva

Methods of Isolation for class V

Cotton Roll + Retraction Cord

Rubber Dam + Cervical Retainer

Cotton roll + cord is more commonly used and practical

Cord Types:

Braided (preferred), twisted, or woven Should fit sulcus comfortably

Retraction Cord

Place before tooth preparation to avoid gingival injury.

Temporary apical and lateral retraction Hemostasis (if treated with hemostatic agents)

Treatment Options of hemostasis

Aluminum chloride or ferrous sulfate (preferred) Epinephrine (use caution; can cause systemic effects like BP,

HR, dysrhythmia)

Placement Tips:

Cord length: 1⁄4 inch (6 mm) longer than gingival margin Wet with hemostatic agent, blot before use
Use blunt instrument (e.g., explorer tine) to insert gently Use second instrument to prevent dislodgment

Use air syringe or cotton to control sulcular fluid

Avoid Over-Retraction:

Watch for blanching use smaller cord if needed

During Amalgam Procedure

Cord remains in place during preparation and initial carving.
May hinder tactile feel during carving near gingival margin risk of over-contouring.

Solution: Tease cord out after removing gross excess, then complete carving.

Enamel Decalcification Considerations

If no cavitation and minimal decalcification: Do not extend outline form unnecessarily.

If outline must include all decalcified areas:
May lead to excessive extension into proximal cervical

areas or circumferential involvement.
Restoration may become difficult or nonviable.

INITIAL TOOTH PREPARATION for class v resto

Initial Entry and Depth

Bur used: Tapered fissure bur (e.g., No. 271)

Initial axial depth:

0.5 mm inside DEJ (on crown)
0.75 mm (on root surface)
Total depth typically: 1–1.25 mm, depending on occlusogingival location

Bur technique:

Use edge of bur’s end for penetration (prevents “crawling”)

Adjust bur orientation to:

Keep walls perpendicular to external tooth surface Align with enamel rod direction

Preparation Extension

Extend in all directions (incisally, gingivally, mesially, distally) until margins are in sound tooth structure

Mesiodistal and occlusogingival contours require:

Adjusting handpiece angle
Protecting rubber dam with a flat-bladed instrument if needed

Axial Wall Characteristics

Follows facial contour convex in both mesiodistal and occlusogingival directions

Variable depth:

Incisal wall deeper (~1–1.25 mm): more enamel Gingival wall shallower (~0.75–1 mm): less enamel or on cementum

Purpose of 0.5 mm inside DEJ:

Allows retention grooves without undermining enamel Ensures dentin thickness at gingival aspect to protect pulp

Round carbide burs (No. 2 or No. 4)

For initial entry in inaccessible areas

Helpful in defining internal line angles

Smaller round burs aid in precise retention groove placement

Alternative Burs for class V 

angle-former chisel or No. 33 1/2 bur

Final tooth preparation involves removing any remaining:

infected dentin
pulp protection
retention form
finishing external walls
cleaning, inspecting, and desensitizing

burs used to remove remaining infected axial wall dentin

No. 2 round bur — smaller, about 1.0 mm in diameter

No. 4 round bur — larger, about 1.4 mm in diameter

Any old restorative material remaining may be left if:

(1) no clinical or radiographic evidence of recurrent caries exists

(2) the periphery of the base and liner is intact

(3) the tooth is asymptomatic

MACROMECHANICAL RETENTION

he mechanical interlocking of a restorative

material with tooth structure by cavity design and

undercuts, not by bonding.

BUR USED:

No. 1⁄4 round bur

retention grooves for class V

0.25 mm deep

Large Preparations That Include Line Angles

Facial or Lingual caries may extend

beyond the line angles of the tooth.

Round bur:

Used to start the distal portion

Small round bur:

Used to accentuate the internal line angles of the distal portion.

Hand instruments can be used

to complete the distal half.

Grooves = entire length of the occlusoaxial and gingivoaxial line angles using No. 1⁄4 round bur

For distal portion:

Gingival margin trimmer or 7-85-2 1⁄2 -6 angle-former chisel is used

When a Class V outline form closely approaches an existing restoration, the preparation should be extended to remove the remaining thin enamel wall to achieve

adjoining restorations

Matrix Placement for class V

No matrix needed unless axial wall is convex mesiodistally

Tofflemire band with window cut

instrument used in Insertion and Carving of the Amalgam

Large condenser

flat bladed instrument

Side of the explorer tine / Hollenback No. 3 carver

Isolation for class V

Rubber Dam with No. 212 Cervical Retainer:

The retainer is removed using care to open the jaws of the retainer wide enough to prevent marring the surface of the restoration. 

The rubber dam is removed, and the area is examined carefully to ensure that no amalgam particles remain in the sulcus.

Retraction Cord:

It may interfere with carving any excess amalgam at the gingival margin. 

Removal of the gross excess of amalgam is followed by careful removal of the cord, followed by completion of the carving along the margin.

Finishing and Polishing of the Amalgam for class V

Incorrect use of a pointed stone at the gingival margin results in the removal of cementum, notching of the tooth structure gingival to the margin, or both.

Reshaping a rubber abrasive point against a mounted carborundum disk.