Amalgam and Composite Restorations

Amalgam

Amalgam is a dental restorative material
An alloy of mercury with other metals, primarily silver, tin, copper, and zinc
Used for fillings for over 150 years
Stronger and more durable than composite resins
Amalgam restorations are placed by first preparing the tooth
The tooth is then cleaned and dried before the amalgam is placed
The amalgam is then condensed into the prepared cavity using a plugger
Once the amalgam is condensed, it is carved and polished to the desired shape
The amalgam is then allowed to set
After polishing, it is given a final check with a mirror and explorer
The amalgam restorative material contains silver (Ag), tin (Sn), copper (Cu), and zinc (Zn)
The composition of amalgam determines its properties, such as strength and setting time
The mercury in amalgam reacts with the other metals to form an intermetallic compound
This process releases heat and causes the amalgam to harden
Setting of amalgam takes place at room temperature in the mouth

Composite

Composite is a tooth-coloured restorative material
Made of a mixture of resin, silica, and other filler particles
Composite resin is used for fillings, veneers, and other cosmetic procedures
Composite restorations are placed by first preparing the tooth
The cavity is then cleaned and dried before the composite is placed
The composite is then cured with a blue light source for about 20 seconds
The composite restorative material contains two main components: Resin and fillers
Resin is a polymer that gives the composite its strength and flexibility
Fillers are particles that make the composite stronger and more resistant to wear
The fillers make the composite more opaque and less likely to stain
Composite restorations are bonded to the tooth using a special adhesive
This adhesive helps to create a strong bond between the composite and the tooth
The polymerisation of the composite resin is initiated using a blue light source
Polymerisation is the process of hardening the composite resin
The composite shrinks slightly during polymerisation
This polymerisation shrinkage can cause stress on the tooth, leading to postoperative sensitivity

### Polymerisation Shrinkage

The shrinkage creates a tiny gap between the restoration and the tooth
This creates a gap for bacteria and food to get trapped in leading to decay or sensitivity.
The degree of shrinkage is influenced by the type of composite used, the size of the restoration, and the technique that is used to place the composite resin

Classifications

Composite resins are classified based on their filler size and particle structure
Macrofilled composite resins have large filler particles
Hybrid composite resins have a mix of large and small filler particles
Microfilled composite resins have very small filler particles
Nanofilled composite resins have nano-sized filler particles
The filler size influences the properties of the composite resin
Macrofilled composites are strong and durable, but they are less esthetic
Microfilled composites are very smooth and esthetic, but they are not as strong

Mechanical Properties

Compressive Strength: The ability of a material to withstand compressive forces
Tensile Strength: The ability of a material to withstand tensile forces
Shear Strength: The ability of the material to withstand shear forces
Elastic Modulus: The stiffness of the material
Different types of composite resins have different mechanical properties
The properties of a composite resin are affected by the type and size of fillers
Composite resins have a lower modulus than amalgam and are more prone to wear
Composite resins can be used in some cases in high stress areas, like molar fillings
They can be considered for use in high stress areas if the restoration is done properly
Thermal Conductivity: The ability of a material to conduct heat
Composites have a lower thermal conductivity which makes them more comfortable for the patient when drinking hot or cold beverages
Thermal Expansion: The tendency of material to expand with temperature
Composites have a lower thermal expansion coefficient than amalgam, making them more compatible with tooth structure
Wear Resistance: Refers to the ability of a material to withstand wear and tear
The wear resistance of composite restorations greatly depends on the composition of material, the size of the filler particles, and the polishing characteristics
Polymerisation Shrinkage: The shrinkage of the composite resin during polymerisation
The degree of shrinkage is influenced by the type of composite used, the size of the restoration, and the technique used to place the composite resin
Postoperative Sensitivity: More common with composite restorations due to bonding challenges and polymerisation shrinkage

Long Term Effects

Amalgam: Durable, long-lasting, and resistant to wear
Composite: Less durable than amalgam restorations, can be prone to wear and tear
Composite: More prone to staining than amalgam restorations
Composite: Can wear away with time and need replacing more often

Future Trends in Restoratives

Development of new composite resins with improved mechanical properties
Development of new bonding agents for better bonding and a tighter seal
Development of new restorative materials with better biocompatibility
Development of new restorative techniques for less shrinkage
Development of new restorative materials that are more wear-resistant
Ongoing exploration of new materials and technologies to develop more durable and esthetic restorative materials
Continued research into novel restorative materials like glass ionomers and compomer materials
Ongoing research into the use of lasers and plasma technology for curing and bonding of restorative materials
The use of digital technology such as CAD/CAM systems is becoming more commonplace for the fabrication of restorations

Conclusion

Amalgam and composite resins differ significantly in their composition, properties, and long-term effects
The choice between these two materials depends on the specific clinical situation, patient needs, and cost considerations.
Both materials play a central role in restorative dentistry.
With continuing advancements in technology, both amalgam and composite resins continue to evolve with improvements in longevity, esthetics, and biocompatibility.