Natural tooth enamel dentine can be classified as particulate composites in materials science terminology. Enamel is a highly filled composite consisting of greater than 80 volume percent mineral in the form of hydroxyapatite and a finely organized microstructure. These unique characteristics contribute significantly to the enamels ability to withstand the relatively harsh conditions of the oral environment. In recent years, clinical studies have suggested that the current improvements seen in performance properties of dental composites have come about to a great extent by decreasing the size of the filler particles and increasing the percent filler in the resin matrix. It would seem reasonable to think that further improvements may be experienced if this microstructural trend continues. The sol-gel technology offers some unique theoretical potential in this regard and should be examined. The research and development efforts being made in the area of computer aided design and manufacturing (CAD/CAM) and adhesion technology presents some a very real possibility for revolutionary new restorative dental delivery. From a materials perspective, this technology allows researchers to pursue new avenues of materials processing. The maximum utilization of this technology clinically can only come about when combined with materials ideally suited to the task. Materials whose microstructures are minimally adversely affected by the milling process will be most ideal. As clinicians we have employed a high speed milling processes to natural teeth for well over 50 years in the form of restorative tooth preparation. The application of the milling process to natural teeth has enjoyed good clinical success and is not perceived to be a major contributor to restorative failures. Natural teeth themselves would appear to be constructed of materials or tissues which are millable or machinable by nature an may provide one of the better models to materials designers and researchers. Materials which more closely simulate the ultra-fine microstructural features of natural tooth enamel and dentin should be evaluated. The microstructural characteristics of sol-gel derived composite materials are of interest in this regard. The demand for esthetic restorations has had a major impact on the practice of restorative dentistry. As a result, the success of future materials will no doubt be influence by their optical characteristics. Developing materials which have the potential to more closely simulate the optical characteristics of natural teeth must be given strong consideration. The ultra-fine microstructural and compositional flexibility of the sol-gel process allows great potential for the design of new materials with precise control of optical properties. In summary, it appears that there is substantial evidence to suggest that the sol-gel derived method of processing continuous dual matrix composite materials may have some potential as a route to develop new dental materials and should be carefully pursued.
