Dental Materials Science

Principles, Properties and Clinical Applications

1

Course Objectives

By the end of this module, you will understand:

Classification of dental materials
Physical and mechanical properties
Restorative material systems
Impression materials
Cements and liners
Prosthetic materials
Biocompatibility considerations
Recent advancements

2

Material Classification

By Use

Restorative: Amalgam, composite, glass ionomer
Prosthetic: Alloys, ceramics, polymers
Auxiliary: Impression, casting, abrasive
Preventive: Sealants, fluoride varnishes

By Structure

Metals: Amalgam, gold, titanium
Ceramics: Porcelain, zirconia
Polymers: Acrylic, composite resin
Composites: Resin-modified glass ionomer

3

Key Material Properties

Physical Properties

Density: Mass per unit volume
Thermal expansion: Coefficient (ppm/°C)
Color stability: Resistance to staining
Solubility: In oral fluids

Chemical Properties

Corrosion resistance
Setting reaction
Biocompatibility

Mechanical Properties

Strength: Compressive, tensile, flexural
Hardness: Resistance to indentation
Elastic modulus: Stiffness
Fracture toughness: Crack resistance

Biological Properties

Cytotoxicity
Allergenicity
Cariostatic effects

4

Dental Amalgam

Composition

40-50% Mercury (Hg)
50-60% Alloy powder (Ag, Sn, Cu, Zn)
Types: Low-copper (γ2 phase), High-copper (no γ2)

Properties

Compressive strength: 380-550 MPa
Creep resistance: High-copper better
Marginal breakdown: Low-copper worse
Service life: 10-15 years

Clinical Considerations

Requires 1.5-2mm cavity depth
Needs mechanical retention
Delayed polishing (24h)
Controversy over mercury safety
Declining use worldwide

5

Composite Resins

Composition

Resin matrix: Bis-GMA or UDMA
Fillers: Silica, glass (40-80% by volume)
Coupling agent: Silane
Initiators: Camphorquinone (light-cure)

Classification by Filler

Microfilled (0.04μm)
Hybrid (0.4-1μm)
Nanofilled (20-75nm)
Bulk-fill (4-5mm depth cure)

Properties

Flexural strength: 90-180 MPa
Wear resistance: Improved in newer formulations
Polymerization shrinkage: 1.5-5% volume
Thermal expansion: 25-38 ppm/°C

Advantages

Esthetic
Bonding to tooth structure
Conservative preparation

6

Glass Ionomer Cements (GIC)

Composition

Powder: Calcium-alumino-fluorosilicate glass
Liquid: Polyacrylic acid + tartaric acid
Reaction: Acid-base setting

Types

Conventional (Type I, II, III)
Resin-modified (light-cure)
High-viscosity (atraumatic restorative)
Metal-reinforced (cermets)

Properties

Compressive strength: 90-200 MPa
Fluoride release: Sustained (anti-cariogenic)
Adhesion: Chemical to tooth
Biocompatibility: Excellent

Uses

Class V restorations
Luting cement
Liner/base
Pediatric dentistry

7

Restorative Materials Comparison

Property	Amalgam	Composite	GIC
Compressive Strength (MPa)	380-550	250-350	90-200
Tensile Strength (MPa)	48-69	45-75	10-20
Wear Resistance	Excellent	Good	Fair
Esthetics	Poor	Excellent	Fair
Bonding	Mechanical	Adhesive	Chemical
Fluoride Release	No	Some types	Yes
Clinical Longevity	10-15 years	5-10 years	5-8 years

8

Impression Materials

Elastic Materials

Polyvinyl siloxane (PVS):
- Most accurate
- Excellent dimensional stability
- Hydrophobic
Polyether:
- Rigid after setting
- Hydrophilic
- Shorter working time
Alginate:
- Inexpensive
- For study models
- Poor dimensional stability

Rigid Materials

Zinc oxide eugenol:
- For edentulous impressions
- Good tissue detail
Impression compound:
- Thermoplastic
- For border molding

Digital Impressions

Intraoral scanners
No material needed
Increasingly popular

9

Dental Cements

Types by Use

Luting: Zinc phosphate, glass ionomer, resin
Temporary: Zinc oxide eugenol (ZOE), noneugenol
Liners: Calcium hydroxide, glass ionomer
Bases: Zinc phosphate, polycarboxylate

Properties Comparison

Strength: Resin > GI > Zinc phosphate
Solubility: ZOE > GI > Resin
Adhesion: Resin > GI > Zinc phosphate

Clinical Selection Factors

Tooth preparation design
Retention needs
Pulpal health
Alloy type being cemented
Esthetic requirements
Fluoride release needs

New Developments

Self-adhesive resin cements
Bioactive cements

10

Dental Ceramics

Types

Feldspathic porcelain:
- For veneers, inlays
- Highly esthetic
- Low strength
Lithium disilicate:
- (e.g., IPS e.max)
- 350-400 MPa strength
- For crowns, veneers
Zirconia:
- 900-1200 MPa strength
- For crowns, bridges, implants
- Less translucent

Fabrication Methods

Sintering: Traditional powder buildup
CAD/CAM: Milling from blocks
Heat pressing: Lost-wax technique
3D printing: Emerging technology

Clinical Considerations

Tooth preparation design critical
Need for bonding vs. cementation
Wear of opposing dentition
Chipping risk with zirconia

11

Dental Alloys

Noble Metal Alloys

High noble (Au > 40%):
- Type I-IV gold alloys
- Excellent corrosion resistance
- High cost
Palladium-based:
- Less expensive than gold
- Good properties

Base Metal Alloys

Cobalt-chrome:
- For removable partial dentures
- High strength
- Difficult to adjust
Nickel-chrome:
- For crowns, bridges
- Nickel allergy concerns

Titanium

Excellent biocompatibility
Low density
Difficult to cast
Used for implants

Properties Comparison

Strength: Co-Cr > Ni-Cr > Gold
Corrosion resistance: Gold > Pd > Ti > Co-Cr
Castability: Gold > Pd > Ni-Cr > Co-Cr
Cost: Gold > Pd > Ni-Cr > Co-Cr

12

Polymers in Dentistry

Types

Acrylic resins:
- PMMA (polymethyl methacrylate)
- For dentures, temporary crowns
- Heat-cured or auto-polymerized
Elastomers:
- For impression materials
- Polyethers, polysulfides
Composite resins:
- Bis-GMA based
- For restorations

Properties

Advantages:
- Easy to fabricate
- Low cost
- Esthetic
Limitations:
- Polymerization shrinkage
- Water sorption
- Wear
- Thermal expansion

New Developments

High-impact resins
Injectable resins
3D printable resins

13

Biocompatibility of Dental Materials

Potential Issues

Cytotoxicity:
- From monomers, metals, byproducts
- May affect pulp, gingiva
Allergic reactions:
- Nickel (10% population sensitive)
- Latex, acrylates
Carcinogenicity:
- Formaldehyde release
- Beryllium (in some alloys)

Testing Methods

In vitro:
- Cell culture tests
- Agar diffusion
In vivo:
- Animal tests
- Usage tests
Clinical trials

Regulations

ISO 10993 standards
FDA classification (I, II, III)
EU Medical Device Regulation

14

Dental Adhesive Systems

Enamel Bonding

Etch-and-rinse:
- 37% phosphoric acid
- Creates microporosities
- Bond strength 20-30 MPa

Dentin Bonding

Total-etch (4th gen):
- Separate etch, prime, bond
- Gold standard
Self-etch (6th-8th gen):
- Acidic monomers
- Less technique sensitive
Universal adhesives:
- Can be used in any mode
- Simplified procedures

Hybrid Layer

Resin-infiltrated dentin
5-10μm thick
Critical for bond strength

Factors Affecting Bonding

Smear layer management
Dentin moisture
Matrix metalloproteinases (MMPs)
Bond degradation over time

New Developments

MMP inhibitors
Bioactive adhesives
Self-healing bonds

15

CAD/CAM Dental Materials

Milling Materials

Zirconia:
- Y-TZP (yttria-stabilized)
- High strength (900-1200 MPa)
- Multilayer options for esthetics
Lithium disilicate:
- IPS e.max CAD
- 350-400 MPa after crystallization
- Excellent esthetics
Hybrid ceramics:
- Resin-ceramic composites
- Easier milling
- Lower modulus

3D Printing Materials

Resins:
- For models, surgical guides
- Interim restorations
Metals:
- Co-Cr alloys
- Titanium
- For frameworks, implants

Advantages

Single-visit dentistry
Digital workflow
Improved fit
Material efficiency

Limitations

High equipment cost
Learning curve
Material limitations

16

Endodontic Materials

Root Canal Sealers

Zinc oxide eugenol:
- Classic material
- Antimicrobial
- May stain tooth
Calcium hydroxide:
- Biocompatible
- Promotes healing
- Weak antibacterial
Epoxy resin:
- (e.g., AH Plus)
- Excellent adhesion
- Dimensional stability
Bioceramic:
- MTA-based
- Excellent sealing
- Promotes regeneration

Obturation Materials

Gutta-percha:
- Standard material
- Thermoplastic
- Used with sealer
Resin:
- e.g., Resilon
- Bonds to sealers
- Similar handling to GP

Other Materials

Intracanal medicaments:
- Calcium hydroxide paste
- Chlorhexidine
- Corticosteroid-antibiotic
Perforation repair:
- MTA
- Bioceramics

17

Orthodontic Materials

Fixed Appliances

Brackets:
- Metal (stainless steel)
- Ceramic (polycrystalline, monocrystalline)
- Self-ligating
Archwires:
- Stainless steel
- Nickel-titanium (superelastic)
- Beta-titanium (TMA)
- Copper-nickel-titanium
Bands:
- Stainless steel
- With buccal tubes

Adhesives

Composite resin:
- Light-cured
- With primer
RMGI:
- For high caries risk
- Fluoride release

Clear Aligners

Polyurethane:
- Thermoformed
- Worn 20-22h/day
Attachment materials:
- Composite
- For better control

New Developments

Smart wires (temperature responsive)
3D printed aligners
Bioactive adhesives

18

Preventive Materials

Pit and Fissure Sealants

Resin-based:
- Bis-GMA or UDMA
- Require etching
- Light-cured
Glass ionomer:
- Fluoride release
- Less technique sensitive
- Lower retention

Fluoride Releasing Materials

Varnishes:
- 5% NaF (22,600 ppm F)
- Applied 2-4x/year
Gels/foams:
- APF (1.23% F)
- For office application
Restorative materials:
- GI, RMGI, some composites

Desensitizing Agents

Potassium nitrate:
- In toothpastes
- Blocks nerve transmission
Oxalates:
- Precipitates in tubules
Glutaraldehyde/HEMA:
- Seals tubules

Antimicrobials

Chlorhexidine:
- 0.12% rinse
- For gingivitis
Xylitol:
- In chewing gums
- Reduces S. mutans

19

Dental Implant Materials

Implant Body

Titanium (CP or alloy):
- Grade 4 (CP) or Grade 5 (Ti-6Al-4V)
- Osseointegration capability
- Surface treatments (SLA, anodized)
Zirconia:
- Metal-free alternative
- Less research than titanium
- Esthetic advantage

Abutment Materials

Titanium:
- Standard material
- Strong, biocompatible
Zirconia:
- For esthetic zone
- Less gray show-through
Gold:
- For screw-retained
- High precision

Prosthetic Components

Screw materials:
- Titanium alloy
- Gold alloy
Cement vs screw-retained:
- Material selection differs

Surface Modifications

Macro:
- Thread design
Micro:
- Acid-etching
- SLA (sandblasted, acid-etched)
Nano:
- Nanotubes
- Bioactive coatings

New Developments

Peek implants
Bioactive surfaces
3D printed custom implants

20

Temporary Materials

Direct Temporization

Acrylic resins:
- PMMA (powder/liquid)
- Bis-acryl (auto-mix)
- Light-cure
Composite resins:
- For longer-term temps

Indirect Temporization

Provisional crowns/bridges:
- Lab-fabricated
- Higher quality

Cements for Temps

ZOE:
- Eugenol-containing
- Non-eugenol
Resin temporary cements

Clinical Requirements

Easy to fabricate
Adequate strength
Good marginal fit
Easy to remove
Biocompatible
Esthetic

New Developments

3D printed provisionals
Prefabricated shells
CAD/CAM milled temps

Common Problems

Fracture
Debonding
Poor occlusion
Gingival irritation

21

Clinical Material Selection

Factors to Consider

Tooth location:
- Anterior vs posterior
- Load-bearing needs
Extent of destruction:
- Small vs large restorations
Patient factors:
- Age
- Caries risk
- Bruxism
- Esthetic demands
- Cost considerations
Operator factors:
- Skill level
- Equipment available

Common Clinical Scenarios

Class I/II caries:
- Composite
- Amalgam (declining)
- High-viscosity GIC (atraumatic)
Class III/IV:
- Composite
- Porcelain veneer/crown
Full coverage:
- Metal-ceramic
- All-ceramic
- Zirconia
Pediatric:
- Stainless steel crowns
- GIC

22

Material Failure Analysis

Common Failure Modes

Fracture:
- Bulk fracture
- Crack propagation
- Fatigue failure
Debonding:
- Adhesive failure
- Cohesive failure
- Mixed failure
Wear:
- Abrasive wear
- Attrition
- Erosion
Discoloration:
- Surface staining
- Intrinsic color change

Contributing Factors

Material factors:
- Inadequate properties
- Poor formulation
Technical factors:
- Improper manipulation
- Contamination
Design factors:
- Inadequate thickness
- Sharp angles
Patient factors:
- Bruxism
- Poor oral hygiene

Prevention Strategies

Proper material selection
Good technique
Patient education
Regular maintenance

23

Emerging Dental Materials

Bioactive Materials

Bioactive glasses:
- Stimulate remineralization
- Antibacterial
Calcium phosphate cements:
- For bone regeneration
MTA derivatives:
- Faster setting
- Improved handling

Smart Materials

Shape memory alloys:
- For orthodontics
pH-responsive materials:
- Release therapeutic agents
Self-healing materials:
- Microcapsule technology

Nanotechnology

Nanocomposites:
- Improved strength
- Better polishability
Nano-hydroxyapatite:
- For remineralization
Antimicrobial nanoparticles:
- Silver, zinc oxide

Digital Materials

3D printable resins:
- For models, surgical guides
- Interim restorations
CAD/CAM materials:
- Improved ceramics
- Hybrid materials

Tissue Engineering

Scaffold materials
Growth factor delivery
Stem cell applications

24

Key Takeaways

Dental materials must balance mechanical, biological, and aesthetic properties
Material selection depends on clinical situation and patient factors
Understanding properties helps predict clinical performance
New materials continuously emerging with improved characteristics
Proper manipulation is crucial for optimal performance
Biocompatibility is essential for all intraoral materials
Digital technologies are transforming material fabrication
Future materials will be more bioactive and intelligent

Questions and Discussion

25