Science of Dental Materials
The science of dental materials involves a study of the composition and properties of materials and the way in which they interact with the environment in which they are placed. The selection of materials for any given application can thus be undertaken with confidence and sound judgement.
The dentist spends much of his professional career handling materials and the success or failure of many forms of treatment depends upon the correct selection of materials possessing adequate properties, combined with careful manipulation.
It is no exaggeration to state that the dentist and dental technician have a wider variety of materials at their disposal than any other profession. Rigid polymers, elastomers, metals, alloys, ceramics, inorganic salts and composite materials are all commonly encountered. Some examples are given in Fig. 1.1 along with some of their uses in dentistry.
This classification of materials embodies an enormous variation in material properties from hard, rigid materials at one extreme to soft, flexible products at the other.
Many dental materials are fixed permanently into the patient’s mouth or are removed only intermittently for cleaning. Such materials have to withstand the effects of a most hazardous environment. Temperature variations, wide variations in acidity or alkalinity and high stresses all have an effect on the durability of materials.
Normal temperature variations in the oral cavity lie between 32°C and 37°C depending on whether the mouth is open or closed. The ingestion of hot or cold food or drink however, extends this temperature range from 0°C up to 70°C. The acidity or alkalinity of fluids in the oral cavity as measured by pH varies from around pH 4 to pH 8.5, whilst the intake of acid fruit juices or alkaline medicaments can extend this range from pH 2 to pH 11.
The load on 1 mm2 of tooth or restorative material can reach levels as high as many kilograms indicating the demanding mechanical property requirements of some materials.
Many products, for example direct filling materials, are handled entirely by the dentist and their chairside assistant and are rarely encountered by the dental technician. Other materials are generally associated with the work of the dental laboratory and in this case both technician and dentist require a thorough knowledge of the materials in order that they may communicate about selection, manipulation and any problems which arise. A third group of materials link the dental surgery and the laboratory. The most obvious example of such products is the impression materials. Whilst the latter are under the direct control of the dentist it is essential that the dental technician also has a sound knowledge of such materials.
1.2 Selection of dental materials
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