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TOOTH COLOURED RESTORATIONS: DIRECT AND INDIRECT

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CONTENTS

1. Introduction
2. Classification of Tooth Coloured Restorations
3. DIRECT TOOTH COLOURED RESTORATIONS
   • A. Composite Resins
   • B. Glass Ionomer Cements (GIC)
   • C. Resin-Modified GIC (RMGIC)
   • D. Compomers
   • E. Giomers
4. INDIRECT TOOTH COLOURED RESTORATIONS
   • A. Ceramic Restorations (Porcelain)
   • B. Indirect Composites
   • C. CAD/CAM Restorations
5. Comparison: Direct vs Indirect
6. Clinical Selection Criteria
7. Recent Advances
8. References

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1. INTRODUCTION

• Direct restorations: Placed directly into the prepared cavity chairside in a single visit.
• Indirect restorations: Fabricated outside the mouth (in a dental laboratory or via CAD/CAM milling) and subsequently cemented into the prepared tooth.

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2. CLASSIFICATION OF TOOTH COLOURED RESTORATIVE MATERIALS

Based on Placement

Based on Composition (Craig's Classification of Composites)

• Macrofilled (conventional): Filler particle size 8-12 µm
• Microfilled: Filler particle size 0.04-0.4 µm
• Hybrid: Combination of macro + micro fillers
• Nanofilled: Filler size 5-75 nm
• Nanohybrid: Most widely used today; combines nanoparticles with microhybrid filler

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3. DIRECT TOOTH COLOURED RESTORATIONS

A. COMPOSITE RESINS

Definition

Composition

Setting Reaction

• Light-cured (most common): Camphorquinone absorbs blue light (468 nm) → free radical generation → chain polymerisation of methacrylate groups. Depth of cure: ~2 mm per increment.
• Self-cured (autopolymerised): Benzoyl peroxide + tertiary amine (two-paste system)
• Dual-cured: Both mechanisms; used for indirect cementation

Classification by Filler Size

1. Macrofilled (Conventional) - 8-12 µm; high strength but poor polishability; e.g. Adaptic, Concise
2. Microfilled - 0.04-0.4 µm; excellent polishability but low strength and high polymerisation shrinkage; e.g. Heliomolar, Silux
3. Hybrid - 0.6-1 µm + fine particles; good balance of strength and aesthetics; e.g. Herculite, Z100
4. Packable (condensable) - High filler content; used for posterior teeth; e.g. SureFil, Solitaire
5. Flowable - Low filler (42-53%); low viscosity; used as liner, cavity bases, class V; e.g. Tetric Flow
6. Nanofilled - 5-75 nm; superior polish, low shrinkage; e.g. Filtek Supreme Ultra
7. Nanohybrid - Most popular currently; combines aesthetics with strength; e.g. Tetric EvoCeram, Venusdiamond

Properties

Cavity Preparation Principles (Black's vs Modern)

• Minimal intervention principles apply - no prophylactic extension
• Beveling of enamel margins (45°) for anterior composites increases bond strength
• Rounded internal line angles
• Depth of preparation: 1.5-2 mm for occlusal surfaces

Bonding System

1. Etch-and-Rinse (Total Etch): 30-40% phosphoric acid etching (enamel 30s, dentine 15s) → primer → adhesive bond
2. Self-Etch: Acidic primer + adhesive; less technique-sensitive
3. Universal (Multi-mode): Can be used in all modes; most versatile currently

Placement Technique (Incremental Layering)

• Maximum 2 mm increments to ensure adequate polymerisation
• Oblique incremental technique for Class II (reduces polymerisation stress)
• Centripetal build-up for Class II
• C-factor (Configuration factor) must be minimised - high C-factor = more polymerisation stress

Finishing and Polishing

• Gross reduction: coarse diamond/carbide burs
• Contouring: medium grit
• Polishing: Sof-Lex discs, rubber points, polishing pastes
• Final gloss: polishing paste + felt wheel

Indications

• Class I, II, III, IV, V cavities
• Diastema closure
• Composite veneers
• Tooth fractures
• Core build-ups

Contraindications

• Patients with composite allergy
• Heavily stressed posterior areas (limited masticatory load tolerance)
• Poor moisture control (relative)
• Areas inaccessible for light curing

Advantages

• Excellent aesthetics
• Bonds to tooth - conservative preparation
• Insulating properties
• Immediate restoration
• Repairable

Disadvantages

• Polymerisation shrinkage causing microleakage, postoperative sensitivity
• Technique-sensitive
• Wear in high-stress areas
• Colour change over time
• Shorter clinical longevity than amalgam (average 5-7 years vs 8-12 years for amalgam)

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B. GLASS IONOMER CEMENTS (GIC)

Definition

Composition

• Powder: Calcium fluoroaluminosilicate glass (Ca, Al, Si, F)
• Liquid: Aqueous solution of polyacrylic acid (40-50%), itaconic acid, tartaric acid

Setting Reaction (Acid-Base Reaction)

1. Dissolution phase: H⁺ ions from acid attack the glass surface, releasing Ca²⁺, Al³⁺, F⁻ ions
2. Gelation phase: Ca²⁺ forms calcium polyacrylate (rapid initial set)
3. Hardening phase: Al³⁺ cross-links polyacrylate chains (slow, final hardening; continues for 24 h)

Classification (Mount's Classification)

• Type I: Luting (cementation) - e.g. Fuji I, Ketac Cem
• Type II: Restorative - e.g. Fuji II, Ketac Fil
  • IIa: Aesthetic restorative
  • IIb: Reinforced (cermet - ceramic + metal)
• Type III: Liner/base - e.g. Fuji Lining, Vitrebond

Properties

Indications

• Class III and V cavities (especially in elderly patients)
• ART (Atraumatic Restorative Treatment) in primary teeth
• Tunnel and box preparations
• Core build-up
• Luting cement
• Liner under composite (Sandwich technique)
• Cervical erosion/abrasion lesions

Sandwich Technique

• Open sandwich: GIC margin at cervical, composite above gingival margin
• Closed sandwich: GIC completely covered by composite
• Achieves fluoride release of GIC + aesthetics of composite

Advantages

• Chemical adhesion - no bonding agent needed
• Fluoride release - caries preventive
• Thermal compatibility with tooth
• Biocompatible
• Moisture tolerant (more than composite)

Disadvantages

• Poor aesthetics (opacity, colour)
• Low fracture toughness
• Moisture sensitive during initial set
• Prone to erosion

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C. RESIN-MODIFIED GLASS IONOMER CEMENT (RMGIC)

Composition

• GIC components + addition of HEMA (hydroxyethyl methacrylate) and photoinitiator

Setting

• Dual set: acid-base (GIC) + light-cure polymerisation (resin component)

Examples

• Vitremer (3M ESPE)
• Fuji II LC
• Vitrebond (liner)

Properties

• Better aesthetics than GIC
• Higher early strength
• Better moisture resistance
• Retains fluoride release
• Expansion on water uptake (hygroscopic expansion)

Indications

• Class III, V restorations
• Pediatric restorations
• Liner/base
• Core build-up in deciduous teeth

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D. COMPOMERS (POLYACID-MODIFIED COMPOSITE RESINS)

Composition

• Resin matrix with acid-modified monomers + fluoride-containing glass particles
• No water in material; acid-base reaction occurs only after water uptake in mouth

Properties

• Better aesthetics than GIC
• Minimal fluoride release (less than GIC)
• No bonding to tooth - requires primer/adhesive
• Moderate strength

Examples

• Dyract (Dentsply)
• Compoglass (Ivoclar)
• F2000 (3M ESPE)

Indications

• Class III, V in adults
• Primary tooth restorations (class I, II in deciduous teeth)
• Not recommended for high-stress posterior areas

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E. GIOMERS

Composition

• S-PRG (surface pre-reacted glass ionomer) fillers in composite matrix
• Pre-reacted glass releases fluoride and other ions

Properties

• Aesthetics similar to composite
• Fluoride release and recharge
• Good polishability
• Better biocompatibility

Examples

• Beautifil II (Shofu)
• BeautifilFlow Plus

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4. INDIRECT TOOTH COLOURED RESTORATIONS

GENERAL WORKFLOW FOR INDIRECT RESTORATIONS

1. Tooth preparation
2. Impression (conventional or digital)
3. Temporary restoration
4. Laboratory fabrication (or CAD/CAM milling)
5. Try-in and adjustments
6. Final cementation/bonding

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A. CERAMIC (PORCELAIN) RESTORATIONS

Classification of Dental Ceramics

1. Glass-based ceramics (feldspathic, leucite-reinforced, lithium disilicate)
2. Polycrystalline ceramics (zirconia, alumina)
3. Resin-matrix ceramics (e.g. VITA Enamic, Lava Ultimate)

• High fusing: >1300°C
• Medium fusing: 1101-1300°C
• Low fusing: 850-1100°C
• Ultra-low fusing: <850°C

1. Feldspathic Porcelain

• Composition: Feldspar (KAlSi₃O₈ - matrix), quartz (filler), kaolin (binder), metal oxides (colour)
• Excellent translucency and aesthetics
• Low strength (60-70 MPa)
• Used for veneers and layering on frameworks
• Technique: Powder slurry built up on refractory die and fired

2. Leucite-Reinforced Ceramics

• Examples: IPS Empress, Empress Esthetic
• Leucite crystals (KAlSi₂O₆) dispersed in glass matrix
• Pressed ceramic technique (heat-pressed at ~1180°C)
• Flexural strength: 120-180 MPa
• Excellent aesthetics; suitable for inlays, onlays, anterior crowns, veneers

3. Lithium Disilicate (IPS e.max)

• Most popular high-strength aesthetic ceramic today
• Lithium disilicate crystals (Li₂Si₂O₅) in glassy matrix (70% crystal volume)
• Two forms: CAD blocks (IPS e.max CAD - blue/milled) and Pressable ingots (IPS e.max Press)
• Flexural strength: 400-500 MPa (e.max Press), 360 MPa (e.max CAD)
• Can be used monolithically or layered with veneering porcelain
• Excellent aesthetics + strength combination
• Indications: Inlays, onlays, anterior/posterior crowns, veneers, 3-unit bridges (anterior only)

4. Zirconia (Yttria-stabilised tetragonal zirconia polycrystal - Y-TZP)

• Strongest dental ceramic: Flexural strength 900-1200 MPa (conventional); up to 1400 MPa (high-strength)
• Transformation toughening: tetragonal → monoclinic phase transformation under stress absorbs crack energy
• Opaque - traditionally used as framework (Zirconia-supported PFZ)
• New generation zirconia (3Y-TZP, 4Y-TZP, 5Y-TZP): increased translucency with some reduction in strength
• High-translucency zirconia (e.g. Katana UTML, VITA YZ HT): can be used monolithically
• Cannot be etched with HF (hydrofluoric acid); bonded with Zirconia primers (MDP-containing)
• Indications: Posterior crowns, bridges (multi-unit), implant abutments

Porcelain Inlays/Onlays

• Moderate to large posterior cavities
• Replacement of large failing restorations
• High aesthetic demand patients
• Parafunctional occlusion (with appropriate material selection)
• Teeth with cuspal fracture risk

• Isthmus width: ≥ 1.5 mm
• Depth: 1.5-2 mm
• All walls diverging occlusally (6-10° taper)
• No undercuts
• Rounded internal line angles
• Butt-joint margins (90°) - no bevels (ceramic fractures at thin edges)
• Smooth, flowing preparation

• Surface treatment: Ceramic etched with 5-9% HF acid (60 sec for feldspathic, 20 sec for e.max) → silanisation → adhesive
• Tooth preparation: Etch (phosphoric acid) → primer → adhesive
• Resin cement: Dual-cure adhesive resin cement (e.g. Variolink II, RelyX Ultimate)

• Stained/discoloured teeth (tetracycline, fluorosis)
• Enamel hypoplasia
• Diastema closure
• Minor misalignment
• Shape corrections (peg laterals)

• Window preparation: Incisal edge preserved; 0.3 mm reduction
• Feather preparation: Minimal; no incisal involvement
• Bevel preparation: Incisal bevel; some incisal reduction

• Excellent aesthetics and colour stability
• Minimal tooth reduction
• Gingival compatibility
• Long clinical longevity (10-15 years)

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B. INDIRECT COMPOSITE RESTORATIONS

Rationale

• Laboratory polymerisation at high temperature/pressure results in higher degree of conversion (> 99%) vs chairside (55-65%)
• Reduced residual monomer
• Lower polymerisation shrinkage at insertion (only luting cement shrinks)
• Better surface finishing and contour possible in lab
• Better contact point and contour than direct

Materials

• Particulate filler composites: Artglass (Heraeus-Kulzer), Signum (Heraeus-Kulzer)
• Fibre-reinforced composites: Targis (Ivoclar), BelleGlass HP (Kerr)

Cementation

• Sandblasting of fitting surface (air abrasion with Al₂O₃)
• Silanisation of fitting surface
• Resin cement (dual-cure) application
• Bond to tooth using standard bonding protocol

Advantages over Direct Composite

• Better degree of conversion
• Better wear resistance
• Better contour and contact points
• Improved colour stability

Disadvantages

• Two-visit procedure
• Higher cost
• Less reparable than direct composite
• Cannot match long-term longevity of ceramics

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C. CAD/CAM RESTORATIONS

Workflow

1. Digital impression: Intraoral scanner (e.g. CEREC Omnicam, iTero, 3Shape TRIOS)
2. Design: CAD software (e.g. CEREC SW, exocad, 3Shape Dental Designer)
3. Milling: 4-axis or 5-axis milling unit from pre-fabricated blocks
4. Post-processing: Glazing, staining, crystallisation (for e.max CAD)
5. Cementation: Same as conventional indirect restorations

Materials Available in CAD/CAM Blocks

VITA Enamic (Hybrid Ceramic)

• Interpenetrating network: 86% ceramic + 14% polymer
• Elastic modulus: 30 GPa (close to dentine at 18 GPa)
• Better fracture resistance than feldspathic
• "Tooth-like" elasticity - less stress on opposing teeth
• Bonded with conventional composite bonding

CEREC Same-Day Dentistry

• Chair-side CAD/CAM: entire workflow in single visit
• Scanning → designing → milling → crystallisation (30 min) → cementation
• Patient advantage: single appointment, no temporaries

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5. COMPARISON: DIRECT vs INDIRECT TOOTH COLOURED RESTORATIONS

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6. CLINICAL SELECTION CRITERIA

Factors Governing Choice:

• Aesthetic demand
• Parafunctional habits (bruxism - prefer zirconia or indirect composite)
• Financial considerations
• Number of appointments tolerable
• Allergy history

• Amount of remaining tooth structure
• Pulp status
• Position in arch (anterior vs posterior)
• Occlusal loading

• Anterior teeth, aesthetic demand: Composite veneer (direct) or porcelain veneer (indirect)
• Posterior, high stress, large cavity: Ceramic inlay/onlay (lithium disilicate or zirconia)
• Primary teeth: RMGIC or compomer
• Cervical erosion/NCCL: GIC or RMGIC
• Deep carious cavity, pulp proximity: GIC liner + composite (sandwich)
• Single appointment, moderate cavity: CEREC CAD/CAM ceramic

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7. RECENT ADVANCES

1. Bulk Fill Composites: Can be placed in 4-5 mm increments. Reduced time, comparable performance. Examples: Tetric PowerFill, SonicFill, SDR (Smart Dentin Replacement - Dentsply). Uses sonic activation or modified photoinitiator systems to reduce polymerisation stress.
2. Self-Adhesive Flowable Composites: Combine bonding and filling in one material; e.g. Fusio (Pentron), Vertise Flow (Kerr). Reduce technique sensitivity.
3. Universal Adhesives: Simplify bonding protocol; compatible with total-etch, self-etch, selective etch; contain MDP monomer for bonding to zirconia; e.g. Scotchbond Universal, Adhese Universal.
4. High-Translucency Monolithic Zirconia: Overcomes opacity limitation while maintaining high strength; enables full-contour monolithic restorations.
5. Digital Workflow: Intraoral scanners + CAD/CAM have eliminated conventional impressions; virtual articulators enable digital occlusal analysis; digital shade matching systems.
6. Resin Matrix Ceramics (RMC): Hybrid materials (VITA Enamic, Lava Ultimate) offer biomimetic elasticity, reducing stress concentration on restored tooth.
7. 3D Printing for Temporaries: PMMA-based dental 3D-printed temporaries using SLA/DLP printers.
8. Adhesive Cementation Advances: Universal resin cements (e.g. Panavia V5, RelyX Universal) effective for all ceramic types with single bonding protocol.
9. Biomimetic Dentistry: Concept of restoring teeth to mimic natural biomechanics using layered composites or ceramics with graduated elastic modulus.
10. Smart Dental Materials: GICs with enhanced ion release, antibacterial monomers in composites (e.g. MDPB), bioactive calcium silicate-containing materials.

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8. REFERENCES

1. Sturdevant's Art and Science of Operative Dentistry - Roberson TM, Heymann HO, Swift EJ Jr. (6th ed.). Elsevier/Mosby.
2. Phillips' Science of Dental Materials - Anusavice KJ, Shen C, Rawls HR. (12th ed.). Elsevier.
3. Restorative Dentistry - Pickard's Manual of Operative Dentistry - Kidd EAM, Beckett H, Smith BGN. (9th ed.). Oxford University Press.
4. Craig's Restorative Dental Materials - Sakaguchi RL, Powers JM. (13th ed.). Elsevier/Mosby.
5. Contemporary Fixed Prosthodontics - Rosenstiel SF, Land MF, Fujimoto J. (5th ed.). Elsevier.
6. Clinical Aspects of Dental Materials - Gladwin M, Bagby M. (5th ed.). Lippincott Williams & Wilkins.
7. Operative Dentistry - Modern Theory and Practice - Summitt JB, Robbins JW, Schwartz RS. (3rd ed.). Quintessence Publishing.
8. IPS e.max Scientific Documentation - Ivoclar Vivadent AG. Technical Documentation.
9. van Noort R. Introduction to Dental Materials (4th ed.). Elsevier Mosby.
10. Guess PC, et al. Monolithic CAD/CAM lithium disilicate versus veneered Y-TZP crowns: comparison of failure modes and reliability after fatigue. Int J Prosthodont. 2013;26(4):359-368.
11. Ferracane JL. Resin composite - State of the art. Dent Mater. 2011;27(1):29-38.
12. Mount GJ, Hume WR. Preservation and Restoration of Tooth Structure. (2nd ed.). Knowledge Books & Software.

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SUMMARY TABLE

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• Comprehensive classification with full detail on each material
• Composition, setting reactions, properties for each
• Cavity preparation principles and clinical technique
• Comparison tables
• Recent advances
• Standard academic references from core dental textbooks