Intro Operative [Resin-Based Composite]

Composite

A solid that contains two or more different component materials or phases when considered at greater than an atomic scale.

Strength and elasticity are significantly changed in comparison with a homogenous material consisting of one component alone

Terminology

Resin-based composite (RBC)

Dental comosite

Polymer matrix composite

Particulate-reinforced polymer matrix composite

What are resin-based composites used for

Direct restoration of anterior and posterior teeth

Dental sealants

Luting of indirect restorations

Cementation of orthodontic appliances

Resin blocks for indirect composite restorations using CAD-CAM technology

Original development of resin was

around the 60s

Before that used acrylic

Summary of the evolution of dental composite over more than 60 years IMAGE

Basic compositions of RBC

1. Resin matrix

2. Filler particles

3. Coupling agent

4. Initiator and inhibitors

5. Pigments

6. Others (antibacterial etc)

who created the first resin composite and Bis-GMA

R. L. Bowen

Resin matrix monomers

Bis GMA

UDMA

TEGDMA

Main component of the monomers

Methacrylate

React with each others

The molecular weight of the 3 monomers tells us what

larger MW mixed with smaller MW helps dilute the mixture

High MW are to big and stiff that you can't add much fillers

Add a lower MW with the higher MW makes it all more fluid and fillers will mix together better

Fillers are __ -__% by volume

30-70%

Filler particles types

- Finely ground quartz or glass sol-gel ceramic

- Microfine silica

- Silica nanoparticles

Functions of filler particles

Reinforcement of the resin matrix

Reduction of polymerization shrinkage

Reduction of the thermal expansion/contraction

Decrease water sorption

Impart radiopacity

Control workability/viscosity

What is Phoenix's body weight

188

The more fillers we have will proportionally reduce

the amount of organic matrix

More filler = better

Coupling agent- silane

Provides the bonding between the inorganic filler particles and the organic resin matrix

- forms an interfacial bridge that strongly binds the fillers to the resin matrix

- It enhances the mechanical properties of the resin composite and minimizes the loss of the filler from resin matrix during clinical wear

TA:

- bridging material

Initiators: Chemically activated resin composites

Polymerization begins when the two components are mixed

Initiators: Light cured resin composites

Photo-initiators

- absorb electromagnetic energy

Inhibitors

Prevent spontaneous polymerization

ex: Hydroquinone

Increases:

- shelf-life

- Workin time

Resin polymerization

Polymerization shrinkage: Clinical implications

Creation of internal stress

Cusp deformation

Marginal gaps

Enamel cracks

- marginal leakage

- postoperative sensitivity

- secondary caries

Optical characteristics

Multiple shades and transclucency of both enamel and dentin

Dentin like: opaque, dentin, body, etc

Enamel-like: Enamel, body etc

Translucent-like shades: incisal translucent

- Intermediate opacity usually used for posterior restorations (single shade)

- Multiple shades used for anterior restorations

Classification of Resin-based composites

1. Filler particle size and distribution

2. Clinical usage (flowable, universal, bulk fill)

3. Polymerization reaction (light-cured; self cured; dual cured)

Classification: Filler particle size

Microfil

40-50 nanometer sized fillers, pre-polymerizated filled resin particle mixed with the monmers

Polished to the highest luster and smoothest surface

Not as strong as other RB- low stress bearing and esthetic areas

Mini/midfill or microhybrid

Less than 1 micrometer sized fillers

Intermediate filler loading between microfills and hybrids (high strength and good resistance)

Used for anterior and posterior restorations

Nanofilled and nanohybrid

< 100 nanometer sized filled or conventional fillers with added nanometer particles

High strength esthetics and polishability

Classification- clinical application and viscosity: Packable

Packable (high viscosity)

- Posterior teeth

- difficult adaptation

- rarely used

- Idea that packing composites would be similar to dental amalgam (Not really)

Classification- clinical application and viscosity: Flowable

Flowable (low viscosity)

- Easily adapt to the preparation

- Inferior mechanical properties

- Not to be used in load bearing area

- Better results with newer formulation

Classification- clinical application and viscosity: Conventional

Conventional (regular viscosity)

- Universal composites

- nanofilled, nanohybrids and microhybrids

- higher resistance, low wear, can be used in load bearing areas

- Polymerization shrinkage (stress)

Classification- clinical application and viscosity: Bulk-fill

Bulk-fill (conventional or low-viscosity

- Posterior restorations

- Reduced stress from polymerization shrinkage

- Deeper curing depth

- Conventional: Higher resistance, low wear, can be used in load bearing areas

- Low viscosity: not recommended in areas of high wear or loading stresses

Classification- Polymerization reaction: Type 1

Polymer-based restorative materials claimed by the mainufacturer as suitable for restorations involving occlusal

Classification- Polymerization reaction: Type 2

All other polymer-based restorative material, and luting materials

Classification- Polymerization reaction: Class 1

Materials whose setting is initiated by mixing an initiator and activator (self-curing materials)

Classification- Polymerization reaction: Class 2

Materials whose setting is initiated by the application of energy from an external source, such as blue light or heat

Group 1: materials whose use requires the energy to be applied intra-orally;

Group 2: materials whose use requires the energy to be applied extra-orally; these materials will be luted into place.

Classification- Polymerization reaction: Class 3

cured by the application of external energy and also have a self-curing mechanism present ("dual cure" materials)

Desirable physical and mechanical properties

Linear coefficient of thermal expansion (better when similar to the tooth's)

Water sorption (organic phase: increase filler- decrease water sorption)

Wear (filler size, shape and content, position in the dental arch, occlusion)

Modulus of elasticity (stiffness): increase filler - increase stiffness

Color stability (hydrolysis- marginal discoloration)

Physical and mechanical properties: Linear coefficient of thermal expansion

Increase in volume due to atomic vibration promoted by increased temperature in a solid

Clinical relevance: In the mouth, a composite restoration will undergo temperature changes between 4°C and 60°C

Better when similar to the tooth's

Physical and mechanical properties: Water sorption/swelling

Differential volume/weight of the material after immersion in water or another fluid

Influenced by the type of monomers (more hydrophilic monomers will absorb more water) and the amount of fillers

Clinical significance:

- Color, stability, volume stability, weakening of the polymeric structure

Physical and mechanical properties: Water resistance

Surface or volumetric loss of material due to wear

Clinical significance: margin deficiencies, volumetric loss of material, loss of surface gloss

Physical and mechanical properties: Fracture resistance

Maximum force that a body can resist when tested under compressive or tensile loads

Physical and mechanical properties: Fracture toughness

Measure of materials resistance to the propagation of a crack from a preexisting flaw of known size and infinite sharpness

Physical and mechanical properties: Modulus of elasticity and stiffness

The elastic modulus will determine the stiffness of a material

Measured by slope of the elastic region of a stress strain graph

Resin composites are suitable for replacing dentin- similar modulus of elasticity

Higher filler concentration - higher elastic modulus

Resin monomer composition and properties

Road to improvement

Improved sealing and toughness

Bacterial colonization and biofilm formation- antibacterial surface (less secondary caries)

Material degradation resistance- current materials can be degraded by certain salivary and bacterial enzymes

Self repairing materials- crack repair

Multifunctional and stimuli-responsive materials- beneficial pulp response, self adaptation/ repair when unde stress