The concept of the aesthetic dentistry and tooth coloured restorations are not new. Though the aesthetic restorations are in vogue, today and their demand is increasing day by day, the translucent silicates, were even available in late 19th century and early 20th century.
The components of composite resin are,
- Resin matrix
- Coupling agents
- Coloring agents
ADVANCES IN COMPOSITES
1. Flowable Composites
Introduced in 1996, the flowable composites are characterized by the presence of filler particles that have a particle size similar to that of the traditional hybrid composites, but the filler content is reduced which results in a decrease in viscosity.
Flowable composites were launched to improve upon the handling characteristics of existing composites.
- Because of the lesser amount of filler loading, the flow is increased and the material flows immediately on dispensing from the syringe/compule.
- The depth of cure is approximately 6mm.
- Mechanical properties of the material, like compressive strength, diametrical tensile strength, biaxial flexure strength, are generally about 60-90% of those of the conventional composites. Hence the use of these materials should be avoided in high stress areas.
- The low contact angle associated with the flowable composite resins is an indication of how well it will wet and relate to all of the irregularities in the cavity preparation.
- When using the flowable composite resin, it is important to cover all the dentin.
- If any space exists between the matrix band and the gingival margin, there is the potential for allowing the flowable to seep beyond the gingival margin, thereby creating an overhang, which is difficult to remove.
- The thickness should range between 0.5-1micron. Thickness greater than 1mm, is acceptable. However, it is important not to cover the occlusal margins or establish the proximal surface with the flowable agent.
Application areas for Flowable Composites –
- Filling materials in low stress areas.
- Useful in areas of difficult access, like in repairing amalgam, composite or crown margins, pit and fissure sealing, as liners in proximal boxes of class II,CLASS III, and class V cavities.
- Repairing porcelain
- Tunnel restorations
- Core build up
- Veneer material
- Cementing agents for porcelain restorations.
Inferior characteristics include,
- Curing shrinkage
- Water sorption
- Reduced compressive strength
- Low elastic modulus
- Increased wear resistance
Development of an intimate relationship between the walls of the cavity preparation and the surface of the flowable resin.
It serves as a stretchable liner to absorb the shrinkage or contraction of the overlying composite resin restoration.
Before purchase, points to consider,
- Its handling characteristics
A major change in the resin viscosity came about in 1998, with the first introduction of the so called packable composite resin. it is based on the newly introduced concept PRIMM. (Polymer rigid inorganic matrix material). This concept was introduced to help the clinician switch over from amalgam to composite resins. It was believed that if, the composite resin exhibited the handling characteristics of amalgam, the clinician would more readily accept the new material. this system consists of a resin and a ceramic component.
It should be pointed out, that some practitioners refer to the new composite resins as condensable. This is different from packable.
Improved properties over conventional composites,
- Increased flexure modulus
- Increased resistance to wear
- Higher depth of cure.
- Reduced polymerization shrinkage.
- Non stickiness to the instrument.
- Antibacterial composites
Composites that offer Antibacterial properties
Are promising since, several studies have shown that a greater amount of bacteria and plaque accumulate on the surface of the resin composites than on the surface of other restorative materials/enamel surface. Therefore, attempts to incorporate antibacterial properties into resin composites are a welcome step.
Expanding Matrix resin for composites
Composite resins that expand slightly during polymerization are highly desirable as these would facilitate bulk placement of the material and reduce post operative sensitivity.
Laser curing of composite resins
Recently composite resins are bieng cured with lasers. argon laser is the most suited. the intensity of laser required is 250mW, and the time required is 10 seconds per increment.
Today, the combination of highly wear resistant composite resins and the ability to bond to dentin has lead to the potential for total replacement of amalgam with a more esthetic material.
The composite resin used by the finishing today represents the accumulation of years of research, and clinical testing. the products of tomorrow, promise to be even more exciting.
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