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material types for direct restoration are: § Dental amalgam (silver-tin-copper alloy and approximately 50% mercury) § Resin-based composite materials (RBC). 9 Future Use of Materials for Dental Restoration § Modifications of RBCs (poly-acid modified composites); compomers and giomers (glass filler modified composites). § Glass-ionomer cements/water-based cements: Self-setting (“pure” glass ionomers) or, more usually, light cured (resin modified glass-ionomers). § Long-term temporary materials e.g. reinforced zinc oxide-eugenol cements. The indications for use of restorative materials span from small cavities to extensive loss of tooth substance. Materials are employed for cavities in primary teeth; for cavities in permanent teeth, ranging from “minimal interventions” to the need for extensive replacements and/or build-procedures; replacement or repair of failed or less satisfactory restorations, or materials are used in people with compromised health and having dental caries on certain locations, e.g. root caries. The development of ‘smart composites’, Amorphous Calcium Phosphate Composites that respond to oral microflora by releasing chemotherapeutics or antimicrobials such as calcium and fluoride, may circumvent some of the shortcomings of composite restorations. Research into a material that is based on the technology of glass ionomers, low shrinking resins and high strength filters with simple handling and acceptable longevity is in progress. 4.1 Strengths and weaknesses of different materials While tooth-coloured restorative materials are generally more expensive than amalgam, they offer an aesthetic alternative to traditional amalgam fillings. However there are concerns about their longevity and wear particularly in areas subjected to masticatory forces. In a study conducted on the longevity of amalgam versus compomer/composite restorations in posterior primary and permanent teeth, the repair rate was seven times greater for composites than for amalgams (2.8 percent of composites versus 0.4 percent of amalgams) (26) Micro leakage is also a disadvantage but it can be reduced with proper manipulation and strict clinical procedures. Important advantages and disadvantages of amalgam, composites, glass ionomers and resin ionomers are presented in Table 1. 10 Oral Health Programme Table 1. Advantages and disadvantages of different types of restorative materials. Amalgam Composites Glass ionomers Resin ionomers Principal uses Dental fillings Aesthetic dental fillings Small non-load fillings Small non-load fillings Heavily loaded posterior restorations Veneers Cavity liners Cavity liners Cements for crowns and bridges Cements for crowns and bridges Leakage and recurrent decay Moderate leakage Low leakage if properly bonded Low leakage generally Low leakage if properly bonded Recurrent decay same as other materials Recurrent decay depends on maintenance of tooth-material bond Recurrent decay comparable to other materials Recurrent decay comparable to other materials Fluoride release may be beneficial Fluoride release may be beneficial Overall durability, fracture resistance & wear resistance Good to excellent durability in large load bearing restorations Good durability in small to moderate restorations Moderate to good durability in non loadbearing restorations; poor in load-bearing Moderate to good durability in non loadbearing restorations; poor in load-bearing Brittle, subject to chipping on filling edges; good bulk strength in large highload restorations Moderate resistance to fracture in high load restorations Low resistance to fracture Low to moderate resistance to fracture High resistance to wear Moderate resistance to wear High wear on chewing surfaces High wear on chewing surfaces Cavity preparation and clinical consideration Require removal of tooth structure Adhesive bonding permits removal of less tooth structure Adhesive bonding permits removal of less tooth structure Adhesive bonding permits removal of less tooth structure Tolerant to wide range of clinical conditions Requires well-controlled