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Composite Resin - Cons & Endo

Composition

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Classification by Filler Particle Size

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Uses in Conservative Dentistry (Cons)

Indications

• Class I cavities - pit and fissure restorations in premolars/molars (aesthetic demand)
• Class II cavities - proximal restorations (packable/hybrid composites preferred)
• Class III - proximal restorations of anterior teeth (no incisal involvement)
• Class IV - proximal + incisal angle restorations
• Class V - cervical abrasion/erosion/caries lesions (flowable preferred)
• Class VI - cusp tip restorations
• Diastema closure - direct composite build-up
• Veneers (direct) - masking discolouration, shape correction
• Enamel/dentine fractures - bonded reattachment or composite build-up
• Composite inlays/onlays (indirect)
• Pit and fissure sealants (unfilled/lightly filled resin)

Advantages in Cons

• Tooth-coloured, excellent aesthetics
• Bonded restoration - requires minimal tooth preparation (conservative cavity design)
• Strengthens remaining tooth structure via bonding
• Easily repairable
• No mercury (unlike amalgam)
• Can be polished to high gloss (nanofill, microfill)

Disadvantages in Cons

• Polymerisation shrinkage (1.7-5%) - causes microleakage, marginal gap, post-operative sensitivity
• Technique sensitive - moisture control, bonding steps critical
• Longer placement time vs amalgam
• Wear - less wear-resistant than amalgam in high-stress areas
• Recurrent caries risk if microleakage occurs
• Discolouration over time (staining from food, beverages)
• Higher cost than amalgam

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Uses in Endodontics (Endo)

1. Coronal Seal / Access Cavity Restoration

• Most critical use in endo: composite is used to seal the access cavity after obturation
• A good coronal seal prevents reinfection of the root canal system
• Composite (with bonding agent) provides a superior coronal seal compared to IRM or ZOE-based materials
• Build-up after RCT: when sufficient tooth structure remains, composite is used as a definitive coronal restoration

2. Reattachment of Fractured Teeth

• After luxation injuries requiring endo treatment, composite bonds fractured fragments

3. Internal Bleaching Follow-up

• After walking bleach technique, access cavity sealed with composite

4. Perforation Repair (Rarely)

• Composite has been used (though MTA/Biodentine are now preferred) for small coronal perforations

5. Post-Space Seal

• Light-cured composite used to seal the orifice around a post before crown placement

6. Barrier Placement (Indirect Pulp Capping Adjunct)

• In near-exposure situations, composite placed over a calcium hydroxide/MTA liner

7. Apical Barrier (indirect via surgical endo)

• Composite used as retrograde filling material in apicoectomy (though MTA/Super-EBA are now preferred)

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Key Pros and Cons Summary (Exam-Oriented)

Advantages

• Excellent aesthetics (shade matching)
• Conservative cavity preparation
• Bonds to tooth (enamel > dentine)
• Strengthens tooth structure
• No galvanic corrosion
• Easy repair
• Radiopaque formulations available

Disadvantages

• Polymerisation shrinkage - most important drawback
• Technique sensitive (critical step: acid etch, primer, bond)
• Moisture sensitivity
• Post-operative sensitivity
• Wear in high-stress areas
• Marginal discolouration with time
• More expensive and time-consuming than amalgam
• Shorter longevity than cast gold/amalgam in large stress-bearing restorations

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Polymerisation Shrinkage - Key Exam Concept

• Composite shrinks toward the light source during curing
• Cuspal deflection can occur in posterior teeth
• Minimised by:
  • Incremental layering technique (2 mm increments)
  • Oblique layering
  • Bulk-fill composites (designed for reduced shrinkage)
  • Using low-shrinkage monomers (ORMOCER, Silorane)

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Bonding to Tooth Structure

• Total-etch (3-step or 2-step) - gold standard for anterior composites
• Self-etch (2-step or 1-step) - less technique sensitive, less enamel bond strength
• Universal adhesives - can be used in both modes

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Flowable Composite (Special Note for Endo & Cons)

• Liner under packable composite (stress-absorbing layer)
• Class V restorations (cervical area - high flexion stress)
• Pit and fissure sealants
• Repair of small defects
• Endo: sealing fine accessory canals or isthmi when used in warm vertical compaction

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Exam tip: The most frequently tested disadvantage is polymerisation shrinkage. The most important use in endodontics is coronal seal of the access cavity. The most conservative cavity design enabled by composite is the box-only preparation or tunnel preparation for Class II lesions.

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Composite Resin Restoration - Full Procedure

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Armamentarium (Instruments & Materials)

Basic Setup

Isolation Instruments

Cavity Preparation Instruments

Etching & Bonding

Composite Placement

Finishing & Polishing

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Step-by-Step Procedure

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STEP 1 - Clinical Examination & Diagnosis

• Thorough history, chief complaint
• Periapical + bitewing radiographs
• Shade selection before rubber dam placement (tooth is hydrated)
  • Use VITA shade guide in natural daylight
  • Note body shade, cervical shade, incisal translucency

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STEP 2 - Local Anesthesia

• Infiltration or block anesthesia as required
• Wait for full effect before proceeding

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STEP 3 - Isolation

• Rubber dam - method of choice
  • Prevents moisture contamination (critical for bonding)
  • Protects patient from chemicals (acid, resin)
  • Improves visibility
• Alternative: cotton rolls + retraction cord + saliva ejector
• For Class II: place wooden wedge interproximally before matrix to pre-wedge and displace papilla

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STEP 4 - Cavity Preparation

• No need for resistance/retention form via undercuts
• Conservative outline - remove only carious tooth structure
• No extension for prevention (unlike amalgam)
• Cavosurface margin: butt joint / beveled (bevel increases enamel surface area for etching, improves aesthetics in anterior teeth)
• Bevel: used on anterior teeth (Class III, IV) - NOT on posterior occlusal margins

1. Outline form with high-speed diamond bur
2. Convenience form
3. Caries removal with round carbide bur (low speed) + spoon excavator
4. Refinement of cavity walls
5. Toilet of cavity (rinse, dry gently - do not desiccate dentine)

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STEP 5 - Liner/Base Placement (if needed)

• Deep cavities (within 0.5-1 mm of pulp): calcium hydroxide (Dycal) or MTA as sub-liner
• Moderate depth: glass ionomer (GIC) as dentine replacement base
• Thin liner: not needed for shallow cavities
• Flowable composite can also serve as a stress-absorbing liner over GIC

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STEP 6 - Matrix Band Placement (for Class II)

• Sectional matrix system (Palodent/Garrison) - preferred for composites
  • Allows better proximal contour and contact point
• Tofflemire matrix - alternative for large restorations
• Mylar/celluloid strip - for Class III, IV (anterior)
• Wooden wedge tightened to:
  • Seal gingival margin
  • Separate teeth slightly
  • Prevent gingival flash of composite

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STEP 7 - Acid Etching

1. Apply 37% phosphoric acid gel
   • Enamel first - 15-30 seconds
   • Dentine - 15 seconds only (over-etching collapses collagen network)
2. Rinse thoroughly with water for 10-15 seconds
3. Dry gently - do not desiccate dentine (keep slightly moist - "moist bonding")
4. Enamel appears frosty/chalky white when properly etched

• Combined etch + prime step
• Less technique sensitive
• Weaker enamel bond unless selective enamel etch used first

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STEP 8 - Primer Application

• Apply primer with microbrush in scrubbing motion
• Allow 20-30 seconds for solvent evaporation
• Gently air thin with chip blower
• Primer makes dentine hydrophilic and penetrates dentinal tubules
• Forms resin tags in enamel and hybrid layer in dentine

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STEP 9 - Bonding Agent Application

• Apply bonding resin in thin layer with microbrush
• Gently air thin (uniform, shiny appearance indicates correct thickness)
• Light cure for 10-20 seconds (some systems are self-cure or dual-cure)
• The bonding agent + primer together form the hybrid layer (Nakabayashi layer)

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STEP 10 - Composite Placement (Incremental Technique)

1. Each increment: maximum 2 mm thick
2. Place first increment at base of cavity
3. Light cure each increment for 20-40 seconds (depends on shade and unit output)
4. Adapt with composite instrument - press firmly against walls
5. Contour with ball burnisher for cuspal anatomy

• Reduces polymerisation shrinkage stress (C-factor management)
• First increment against proximal box wall
• Subsequent increments obliquely placed

• Dentine shade (opaque): body of tooth
• Enamel shade (translucent): outer surface layer
• Incisal shade: incisal edge for translucency
• Mimics natural tooth optical properties

• LED curing unit: 1200-1500 mW/cm², 450-470 nm blue light
• Tip held as close as possible without touching composite
• Dark shades and opaque composites need longer cure times
• Cure from multiple angles for deep/large cavities

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STEP 11 - Removal of Matrix and Wedge

• Remove matrix carefully to avoid fracturing restoration
• Remove rubber dam or cotton rolls

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STEP 12 - Initial Occlusal Check

• Articulating paper - check for premature contacts
• Mark high spots
• Adjust with finishing burs

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STEP 13 - Finishing

1. Carbide 12-fluted finishing bur (low speed) - gross contouring, removing excess, refining margins
2. Fine diamond bur - smoothing
3. Soflex discs (posterior: rubber points; anterior + proximal: discs in sequence)
   • Coarse → Medium → Fine → Superfine
4. Interproximal areas: finishing strips
5. Occlusal surface: rubber abrasive points

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STEP 14 - Polishing

1. Polishing rubber cups/points with polishing paste (aluminum oxide)
2. Diamond polishing paste for final gloss
3. Result: smooth, glossy surface that:
   • Resists staining
   • Reduces plaque adhesion
   • Improves aesthetics

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STEP 15 - Final Occlusal Check

• Re-check with articulating paper in centric occlusion AND lateral/protrusive excursions
• Adjust any interferences
• Smooth adjusted areas again

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STEP 16 - Final Inspection

• Check margins with sharp explorer (should be flush, not catch)
• Check proximal contact with dental floss (should be firm but not too tight)
• Check gingival health
• Take post-operative radiograph if needed (Class II)

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Composite Placement in Endodontics (Access Cavity Seal)

After RCT Obturation:

1. Remove temporary filling (Cavit/IRM) from access cavity
2. Clean access cavity walls
3. Check obturation radiograph
4. Etch + bond access cavity walls
5. Place flowable composite first layer (adapts to canal orifices)
6. Light cure
7. Build up with packable composite in increments
8. Finish and check occlusion
9. Definitive restoration (crown if indicated)

The coronal seal is as important as the apical seal - microleakage through a poor coronal seal leads to reinfection and endodontic failure.

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Common Errors to Avoid

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Exam summary: The most critical step is isolation (rubber dam). The most critical bonding principle is moist bonding of dentine. The most important rule of placement is 2 mm increments. The most common reason for failure is polymerisation shrinkage + microleakage.