Class II Caries Diagnosis, Preparation, and Amalgam Matrix Techniques

What is a Class II carious lesion?

Caries occurring on the smooth proximal surfaces (mesial or distal) of posterior teeth (premolars and molars).

What six categories of diagnostic data are needed before treatment planning a Class II lesion?

1. Chief complaint & symptoms
2. Medical & dental history (caries risk)
3. Extraoral & intraoral soft tissue exam
4. Clinical visual/tactile exam
5. Pulp vitality testing
6. Radiographs (bitewings)

How effective are visual/tactile inspection, transillumination, laser fluorescence, and caries dyes for proximal caries?

• Visual/tactile: Good for occlusal fissures; limited for proximal caries due to adjacent contact.

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• Transillumination: Best for cracks in posteriors and proximal caries in anteriors.

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• Laser fluorescence (DIAGNOdent): Not useful for proximal caries.

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• Caries-detecting dyes: Non-conclusive.

Which radiograph is the main diagnostic method for proximal caries, and which should be avoided?

• Use bitewing radiographs (early proximal lesions are hidden below the contact; occlusal lesions do not appear until advanced).

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• Do not use periapical radiographs for proximal caries diagnosis.

Why is pulp vitality testing performed on deep Class II lesions, and how are EPT and cold (Endo Ice) interpreted?

• Goal: Confirm pulp vitality and mimic patient symptoms.

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• EPT: Normal, abnormal, or no response.

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• Cold test: Normal = brief sharp sensation; lingering pain (\( > \) 3-5 sec) = damaged pulp.

What is an incipient lesion, what are the ADA radiographic scores, and what is the restorative threshold?

• Incipient lesion: Early caries limited to enamel.

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• Threshold: Remineralize in enamel (E1-E2); restore once in dentin (D1-D3).

What CAMBRA preventive measures and remineralization agents are used for incipient proximal lesions? (2)

• Prevention: Cleanings, OHI (flossing), diet counseling, medical review, CAMBRA balance, and sealants.

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• Remineralization: Fluoride rinses, trays, varnish, high-strength fluoride toothpaste, and CPP-ACP.

How does caries risk guide treatment for a lesion reaching the inner half of enamel ($E2$ / Stage C)?

• Low caries risk: Remineralize and observe every 6 months recall exams.

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• High caries risk: Perform resin infiltration or a slot preparation (if no occlusal involvement).

What are the three steps of Resin Infiltration (Icon) for non-cavitated proximal lesions?

1. Etch: 15% hydrochloric acid
2. Dry: Ethanol solution
3. Infiltrate: Apply unfilled resin and light-cure

When are Slot, Conventional, and Complex Class II preparations indicated?

• Slot: Caries in outer dentin (D1) on proximal surface only (no occlusal caries).

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• Conventional: Caries on both proximal surface and occlusal pits/grooves (MO, DO, MOD).

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• Complex: Extensive multi-surface caries involving cusps (e.g., MODBL).

How do existing restorations appear on radiographs, and where is recurrent caries most commonly found? (4)

• Metal (amalgam/gold): Very bright (highly radiopaque)
• Modern composite: Lighter/less radiopaque than metal
• Older composite: Often radiolucent
• Recurrent caries: Most commonly seen at the gingival margin.

What are the restorative material options (4) and clinical factors for Class II lesions?

• Materials: Composite (direct/indirect), Amalgam, Gold (foil/inlay/onlay), Ceramic (inlay/onlay).

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• Factors: Caries location/size, caries risk (CRA), isolation ability, occlusion/bruxism, medical/perio status, esthetics, cost, and time.

Why are Class II slot preparations NOT recommended for amalgam, and how are they charted when used (e.g., for composite)?

• Why not amalgam: Slot preps are not retentive enough for amalgam.

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• Charting: Still charted with the occlusal surface (e.g., MO or DO) because the marginal ridge is cut; specify ""slot preparation"" in the notes."

What are the advantages of a Class II slot preparation? (2)

• Minimally invasive (preserves sound occlusal pits, fissures, and ridges)

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• Better resistance form (smaller isthmus lowers the risk of cusp fracture)

What are G.V. Black's seven sequential principles of cavity preparation?

1. Outline form
2. Retention form
3. Resistance form
4. Convenience form
5. Removal of remaining carious dentin
6. Finish enamel walls
7. Cleanse the cavity preparation

Define Resistance Form and list its four key features in a Class II amalgam preparation.

• Definition: Prevents fracture or dislodgment of the restoration or tooth under occlusal forces.

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• Features: Flat pulpal and gingival floors, rounded internal line angles, rounded/beveled axiopulpal line angle, and1.5 mm amalgam depth.

Define Retention Form and list its three key features in a Class II amalgam preparation.

• Definition: Prevents dislodgment of the restoration along the path of insertion or proximally.

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• Features: Occlusally convergent buccal/lingual walls, occlusal dovetail, and proximal retention grooves.

Name the preparation walls/floors of a Conventional Class II MO versus a Proximal Slot preparation.

• Conventional Class II MO (6): Buccal, lingual, distal walls; pulpal, axial, and gingival floors/walls.

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• Proximal Slot (4): Buccal wall, lingual wall, axial wall, and gingival floor.

Name the six internal line angles of a conventional Class II preparation and state how they are finished.

• Line angles: Buccopulpal, linguopulpal, axiobuccal, axiolingual, axiogingival, and axiopulpal.

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• Finish: All should be well-defined yet rounded (and axiopulpal rounded/beveled) to avoid stress concentration.

What is the cavosurface margin, and what is the required angle of departure for amalgam?

• Cavosurface margin: Junction of a prepared cavity wall and the unprepared external tooth surface.

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• Angle of departure: 90 degree (amalgam is weak when thin;90 degree prevents marginal chipping/fracture).

What four steps must be completed before starting rotary instrumentation for a Class II amalgam prep?

1. Mark the proximal contact with a pencil.
2. Plan the outline form (0.5 mm separation, \( 90^\circ \) departure, box width).
3. Place a pre-wedging wooden wedge.
4. Place a proximal guard (or piece of Tofflemire band).

What are the benefits of pre-wedging, which wedge types are used for amalgam vs. composite, and why is a proximal guard needed?

" • Pre-wedging: Protects gingiva/rubber dam/adjacent tooth, keeps outline conservative, separates teeth for a tight contact, and eases matrix placement.

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• Wedges: Wooden for amalgam; plastic for composite.

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• Proximal guard: Prevents nicking (""necking"") the adjacent tooth."

In the Class II occlusal outline, which grooves/defects are included vs. left, and what is the purpose of the occlusal dovetail?

• Include: All carious pits/grooves, central groove, and deep debris-filled defects.

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• Leave: Shallow defects or superficial stains in sound enamel.

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• Occlusal dovetail: Widens at the opposite fossa to prevent proximal displacement.

What is the ideal width of the occlusal isthmus in a Class II amalgam preparation, and why?

• Width: 1.25-1.5 mm ( 2.0 mm and \( < \frac{1}{4} \) intercuspal distance), centered faciolingually.

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• Rationale: Wide enough for the smallest amalgam condenser, yet narrow enough to preserve triangular ridges and prevent cusp fracture.

What are the proximal clearance requirements at the facial, lingual, and gingival walls, how are they checked, and why are they needed?

• Clearance: 0.5 mm facial, 0.5 mm lingual, and 0.5 mm gingival (verified with an explorer tip).

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• Purpose: Direct visibility, carving excess amalgam, easy matrix band placement, and avoiding adjacent tooth damage.

Why is the facial proximal clearance kept smaller than the lingual clearance ?

1. Esthetics: Minimizes visible dark metal on the facial aspect.

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2. Anatomy: The natural lingual embrasure is larger than the facial embrasure.

"What is the Reverse ""S-Curve"", what three goals does it achieve, and why is it more pronounced facially? "

• 3 Goals: Preserves the facial triangular ridge, establishes 0.5 mm facial clearance, and establishes a \( 90^\circ \) angle of departure.

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• Why more pronounced facially: The contact area and proximal box sit more facially, while the lingual embrasure is naturally larger.

What specific error occurs if you:
1. Widen the entire isthmus facially?
2. Extend straight out from the central groove?
3. Flare straight into the buccal embrasure?

1. Sacrifices the facial triangular ridge (weakens cusp).
2. Fails to establish facial clearance (does not break contact).
3. Fails to establish a \( 90^\circ \) angle of departure (leaves weak, thin amalgam margin).

What are the depth, orientation, and enamel rules for the pulpal floor in a Class II amalgam prep?

• Depth: 1.5 mm at central groove (#330 bur); closer to 2.0 mm at facial/lingual walls (#330D bur).

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• Orientation: Smooth, flat, and parallel to the occlusal plane.

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• Enamel rule: Sound enamel may remain on the pulpal floor if \( > \) 1.5 mm thick and caries-free."

What are the height, DEJ extension, and angulation requirements for the axial wall?

• Height: Minimum 1.25 mm (determined by contact and caries depth).
• DEJ extension: At least 0.5 mm past the DEJ into dentin (so retention grooves stay in dentin).
• Angulation: Perpendicular (\( 90^\circ \)) to the gingival floor.

What is the required gingival floor width (axial depth) in natural teeth vs. typodont teeth, and which instruments measure it?

" • Natural teeth: Minimum 1.0 mm.
• Typodont premolars: 1.0 mm (measured with a #10 enamel hatchet).
• Typodont molars: 1.5 mm (measured with a 1.5 mm binangle chisel)."

How should the axial wall be contoured horizontally, and why?

• Contour: Convex (curved parallel to the DEJ and external proximal surface).

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• Rationale: Ensures even amalgam thickness and protects the pulp (a straight wall risks pulp impingement).

How should the buccal and lingual walls be oriented, and how is this verified clinically?

• Orientation: Occlusally convergent (or parallel in the box, converging occlusally).

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• Verification: Place a finger over the prep to block glare and inspect visually, and place a periodontal probe/explorer flat against each wall.

Describe the placement, extent, and restrictions for proximal retention grooves and the axiopulpal line angle.

• Retention grooves: Cut in dentin at axio-facial & axio-lingual line angles with a #1/4 round bur (upstroke) from gingival floor to axial wall height (prevents proximal & occlusal displacement). Never cut in enamel, axial wall, or gingival floor.

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• Axiopulpal line angle: Rounded/beveled with a #10 hatchet or 132F diamond bur to prevent amalgam stress fracture."

Compare the Traditional Approach versus the Slot Approach for cutting a Class II preparation.

• Traditional (occlusal first): Better box visibility for beginners, but higher risk of removing sound occlusal tooth structure.

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• Slot (proximal box first): More conservative and easier to stop at a slot prep, but harder to see into the box.

List the rotary burs used in a Class II amalgam preparation and their specific roles. (4)

" • #330 / #330D: Primary prep burs (1.5 mm / 2.0 mm depth), convergent walls, rounded internal angles.

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• #245: Longer pear-shaped bur to smooth box walls and level the gingival floor.

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• #1/4 round / 132F diamond: Retention grooves (132F also rounds axiopulpal line angle).

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• Slow-speed round burs: Excavate deep caries.

Summarize Step 1 (Occlusal Portion) of the Traditional Class II amalgam preparation.

" Prepare a Class I outline with a #330/#330D bur to a flat 1.5 mm pulpal floor; include carious grooves/dovetail, keep isthmus 1.25-1.5 mm and centered, create occlusally convergent B/L walls, and keep the marginal ridge wall straight or slightly divergent."

Summarize Steps 2-5 (Ditching Box, Breaking Enamel Shell, & Checking Convergence) of the Traditional Class II prep.

" • Steps 2-3: Ditch inside the marginal ridge parallel to the DEJ until 0.5 mm gingival clearance is reached, leaving a thin proximal enamel shell intact.

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• Steps 4-5: Fracture away the enamel shell with a #10 hatchet or explorer, smooth axial/gingival walls, and verify occlusal wall convergence."

"Summarize Steps 6-7 (Angle of Departure & Smoothing Walls) and distinguish the #10 enamel hatchet from the #12 hoe. "

" • Steps 6-7: Cleave away remaining buccal/lingual enamel spurs at a \( 90^\circ \) angle of departure and smooth the gingival floor.

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• #10 hatchet: Planing tool used with light pressure on buccal/lingual walls.

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• #12 hoe: Hatchet with blade swiveled \( 90^\circ \), used to plane the horizontal gingival floor (or use a #245 bur)."

Summarize the final finishing steps (Steps 8-10) before cleansing and restoring a Class II amalgam prep.

" 1. Recheck separation: Confirm 0.5 mm gingival, buccal, and lingual clearance with an explorer tip.

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2. Round axiopulpal line angle: Use a #10 hatchet or 132F diamond bur.

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3. Cut retention grooves: Use a #1/4 round bur (upstroke) in axio-facial/axio-lingual dentin line angles."

How does caries risk guide treatment for a lesion reaching the inner half of enamel (E2 / Stage C)?

• Low caries risk: Remineralize and observe with 6-month recall exams.

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• High caries risk: Perform resin infiltration or a slot preparation (if no occlusal involvement).

Why is the facial proximal clearance (0.5 mm) kept smaller than the lingual clearance (\( \ge \) 0.5 mm)?

1. Esthetics: Minimizes visible dark metal on the facial aspect.

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2. Anatomy: The natural lingual embrasure is larger than the facial embrasure.

What must be verified during the pre-restoration check, and how does management differ between the clinic and sim clinic?

Verify that the adjacent tooth is NOT damaged and is smooth.

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• Clinic: Smooth rough or damaged adjacent teeth using an orange plastic Sof-Lex disc.

• Sim clinic: Do NOT disc the adjacent tooth.

What are the four main anatomical parts of a Tofflemire matrix holder (retainer)?

1. Head (with guide slots)
2. Slide
3. Rotating spindle (large screw)
4. Set-screw (small screw)

What are the three types of Tofflemire matrix bands, which is used in the sim clinic, and what is its thickness?

"• Types: #1 Universal, #2 MOD wide, and #2 MOD narrow.

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• Sim clinic band: Universal Bands for Amalgam

0.0015 inch thick.

How should the Tofflemire matrix band and retainer be oriented when seated on a tooth?

• Band: Larger flared edge faces occlusally; smaller edge faces gingivally (round out the inside first).

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• Retainer: Open slots face gingivally (smooth side faces occlusally); slot sits in the middle of the tooth.

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• Arch alignment: Retainer lies parallel to the facial/buccal surface toward the vestibule (not sticking straight out).

What are the ideal occlusogingival heights for a Tofflemire matrix band, and why do you loosen the spindle by a half-turn?

• Occlusally: ~\(1\{ mm}\) above the preparation (allows overfilling amalgam).
• Gingivally: At least \(1\{ mm}\) below the gingival margin (avoids overhanging restorations).
• Half-turn adjustment: Loosens the band slightly so amalgam can expand slightly to create a good contact.

How is an interproximal wedge inserted, and what are its main functions?

• Insertion: Enter from the lingual (or largest) embrasure at an angle; push in fully with a condenser or the back end of tweezers using the largest wedge possible (use 2 wedges for MOD).

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• Functions: Seals the gingival embrasure/margin, creates separation, and compensates for the thickness of the matrix band.

What problems occur when a selected interproximal wedge is too tall and narrow, too big, or too small?

• Too tall and narrow: Pushes the matrix band into the proximal box.
• Too big: Improperly positioned/adapted.
• Too small: Leaves the band unadapted at the gingival margin.

How do you prepare the proximal contact area on the matrix band, and what must be checked before mixing amalgam?

• Use a ball burnisher to impart a convex contour (burnish only where you want the contact) to form a broad, tight contact area rather than a pinpoint contact.

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• Check the stability of the matrix assembly before mixing the amalgam.

After triturating the amalgam capsule, how do you load the amalgam carrier and where is the first increment placed?

• Load both sides of the amalgam carrier and use the small end first.
• Place the first load into the smallest and hardest-to-reach area: the gingival area in the proximal box.

What is the proper sequence and technique for condensing amalgam in a Class II preparation?

• Start at the gingival part of the proximal box and retention points using a small condenser first.
• Condense gingivally and laterally toward the adjacent tooth, sliding alloy into the box corners with overlapping stepping movements to prevent voids.
• Once the box is filled, use a larger condenser to condense along the entire occlusal surface.

How and why is pre-carving burnishing performed on a Class II amalgam restoration?

• Overfill the amalgam, then burnish before carving using an egg or acorn burnisher.

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• Move from the center bulk toward the margins to develop the central groove and bring the mercury-rich surface layer to the top so it is removed as excess.

What are the key rules and steps for carving the occlusal surface while the matrix band is still in place?

• Always carve directionally from tooth to amalgam (resting on natural tooth as a guide) to avoid ditching margins.

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• Gently use an explorer (or Hollenback carver) to remove bulk and separate the occlusal embrasure between the band and amalgam (be careful not to overdo it).

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• Carve the central groove, add secondary grooves, and ensure the marginal ridge is level with the adjacent tooth.

How do you remove the Tofflemire retainer and carve the facial and lingual proximal margins?

• Stabilize the band and carving with your thumb, unscrew the outer assembly, and lift off the Tofflemire retainer while the amalgam is still soft.

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• Peel the band to expose and carve the facial margin, then remove the band from one contact to expose and carve the lingual margin.

In what order and manner are the matrix band and wedge removed, and what is carved immediately afterward?

• Always remove the band BEFORE the wedge.
• Gently lift the band out at a \(45^\circ\) angle toward the lingual embrasure (do NOT use a sawing motion).

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• Remove the wedge with tweezers, then carve the gingival margin and facial/lingual embrasures from tooth toward amalgam (avoiding an open contact, which is a critical error).

What final wiping and evaluation steps are performed after carving a Class II amalgam restoration? (4)

• Burnish/wipe the carving after just setting with a saturated wet cotton roll.

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• Clean the gingival area with an EverEdge and check margins with an explorer.

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• Check overhangs with floss and explorer (do NOT check with floss until amalgam is set).

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• Check occlusion with articulating paper and tactile sensation.

Which anatomical features must be evaluated when checking a completed Class II amalgam restoration?

Evaluate the proximal contours, contacts, occlusal anatomy, and embrasures (ensuring a proper occlusal embrasure).

What is amalgam flash, how do you check for it, and why is it clinically unacceptable?

• Flash is thin excess amalgam extending over the cavosurface margin (checked by memorizing the cavosurface outline of the prep).

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• It will eventually break off submarginally, trapping plaque and leading to recurrent caries.

What are the benefits of finishing and polishing amalgam, how long must you wait, and what tools are used?

• Benefits: Prolongs restoration life, decreases tarnish and corrosion, smoothes rough surfaces that accumulate plaque, and improves marginal integrity.

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• Timing: Wait \(24\text{ hours}\) for final set and crystallization, which increases compressive strength.

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• Tools: #7404 carbide bur, flour of pumice, greenie, etc.