A Mini-Guide to Dental Composites
Have you ever wondered about the white filling material your dentist uses to fill the teeth?
This mending material is known as dental composite. Composites are a group of tooth colored, synthetic polymeric resins used as dental restoratives and adhesives. The word “composite” refers to a combination of two or more things. Dental composites are composed of a resin matrix reinforced with a suitable filler, in addition to minute quantities of other components.
Dental composites are currently the most widely used filling materials, especially in developing countries, owing to their ability to match natural tooth color and their ease of manipulation and adequate strength. This group of restorative materials has replaced the previously used silver amalgams, which are gradually declining to be used as restorative materials, due to concerns raised by researchers and scientists regarding their safety.
Composition of Dental Composites
The major components of composites are a combination of synthetic polymers (BisGMA and UDMA) and co-polymers (TEGDMA), and a suitable filler material such as quartz or finely ground glass particles.
The function of fillers in composites is to enhance the fracture resistance, and to decrease the polymerization shrinkage of the resin. Furthermore, to enhance the adhesion between the filler and resin, a silane “coupling” agent is also added, which functions by creating an adhesive interface between the filler and the polymer.
Other ingredients include initiators, activators that help in the polymerization process. An inhibitor is added to prevent “auto-polymerization”, and to control the speed of the polymerization reaction.
Clinical Handling of Composites
Manufacturers usually supply composites in the form of pastes, each paste having a distinct shade, to help in matching with a wide range of tooth shades in patients. Hence, composites can be regarded as the most aesthetic materials, when compared with other direct restorative materials, such as amalgams and glass ionomers.
The process of placing a composite filling is initiated by removing the carious tooth structure. The next step is to apply an acidic etch-ant, such as phosphoric acid, onto the tooth. The etch-ant demineralizes a part of dental enamel, which creates space for the resin to penetrate and create a “micro-mechanical” attachment with the tooth structure. The tooth must be sufficiently dried before the placement of the composite, since moisture adversely effects the bond strength and integrity of the filling material.
Polymerization, or “light curing” is initiated by exposing the resin to a light source, such as the LED light curing unit or a halogen lamp. Care must be taken to incrementally cure the composite in thin layers, as the light curing apparatus is unable to properly cure composites having a thickness greater than 2-3 mm. Another advantage of incremental curing of composites is the reduced polymerization shrinkage which occurs after each curing cycle.
Advantages of Dental Composites
• Aesthetics – composites are tooth colored restorative materials, and their shade can be easily matched with the natural tooth color. Hence, these filling materials are very popular among people who are conscious of their appearance.
• Strength – with continued research in the dental materials science, the contemporary composites are able to achieve very high bond strengths with the tooth structure, which results in minimization of tooth fracture and de-bonding of the restorations.
• Conservation of Natural Tooth Structure – the placement of amalgam restorations requires extensive tooth preparation which results in the sacrifice of sound tooth structure. An advantage of composites is that they do not require a definite tooth preparation design, and only require the removal of soft and carious dentin. Hence, these materials can be regarded as more tooth conservative, since they do not require an extensive removal of healthy tooth structure.
• Repair-ability – in contrast to the dental amalgam, the composites can be easily repaired by the addition of another increment of filling material.
• Safety – composites have been shown to exhibit lesser local and systemic toxicity, when compared with the dental amalgams.
• Polymerization Shrinkage – an inherent drawback of the composites is the shrinkage they undergo after polymerization, which not only undermines the strength and integrity of the filling, but can also generate excessive stresses onto the adjacent natural tooth structure, which result in fracture of the tooth.
• Technique Sensitivity – the placement of composites requires skill and experience, and any deviation from the recommended method of use results in premature failure of the restoration.
• Less Durable – the composites restorative materials are not as durable as the amalgams, especially if the patients have a habit of excessive tooth grinding.
• Costly – composite fillings are more expensive than dental amalgams, hence they’re not affordable to every patient.
• Limited Insurance Coverage – most insurance plans cover dental treatment with composites only on the front teeth where amalgam restorations cannot be placed due to aesthetic concerns. Hence, patients have to pay from their own pocket when they require a posterior filling with composites.