Erosion bacteria

Tay et al. (1974, 1979) have studied the mechanism of erosion of the dental silicate cement in service, finding that grooving occurs at the margin between the restoration and the tooth. Erosion exposes the cavity and provides sites for the accumulation of food debris and bacteria which can cause inflammation of the gingiva (Larato, 1971). It also leads to staining of the restoration (Bock, 1971 Kent, Lewis Wilson, 1973). 

Bacterial attack is an early stage in the degradation of wood exposed in wet or moist conditions. Bacteria can be the dominant form of attack when fungal decay is suppressed by a wood-preserving treatment. Bacteria can attack the cell wall of wood by tunnelling, cavitation or erosion mechanisms (Eaton and Hale, 1993). 

The organic matter in topsoil is a mixture of fallen plant material, the remains of dead animals, and such decomposers as bacteria and fungi, as Figure 15-9 illustrates. This organic matter is called humus, and it is rich in a variety of plant nutrients. Humus tends to be porous, giving roots access to subterranean water and oxygen. It also binds the soil, helping to prevent erosion. 

The seaweeds known as kelps and giant kelps (Laminariales) are built in such a way that they produce detritus more or less continuously. All are divisible into holdfast, stipe and blade (Fig. 7) and the blades normally have a growth zone at the base and a zone of erosion near the tip. They have been likened (Mann, 1972b) to "moving belts of tissue". Growth at the base compensates for erosion at the tip, and in the process large amounts of detritus, both particulate and dissolved, are released into the water. This detritus is readily colonized by bacteria (Laycock, 1974) and appears to be less resistant to digestion by animals than the detritus derived from vascular plants. 

Recently there has been much concern over arsenic in aquatic and soil environments from sources such as arsenical pesticides, smelters, coal-fired plants, and erosion caused by intensive land use (Huang and Liaw, 1979). Arsenic can exist in several oxidation states. It has been shown that in marine environments, As(V) can be reduced to As(III) by bacteria... 

Fig-1- SEM micrographs of biotically aged polylactide films a) surface erosion, b) bacteria, and c) fungi on the surface of the PLLA films... 

Rainwater is responsible for the washing and cleaning processes of the atmosphere by means of dissolution of gases and salts, and the transport of substances and particles onto the surface of the Earth. The particles of minerals and salts washed out by rain usually have diameters below 1 p.m. Other particles included in the washout are microorganisms, such as bacteria, that are suspended in air through wind erosion and carryover. 

In the two billion years of the Proterozoic eon (2,500-570 million years ago). North America s geologic setting became more like the world as we know it. The cores of the modern continents were assembled, and the first collections of continents, or supercontinents, appeared. Life, however, was limited to bacteria and algae, and unbreatheable gases filled the atmosphere. Rampant erosion filled the rivers with mud and sand, because no land plants protected Earth s barren surface from the action of rain, wind, heat, and cold. 

Erosion is defined as the loss of hard tissue by chemical means not derived from bacteria, i.e. the dissolution of hard tissue by acid where the acid source is not the oral bacteria [5], Erosion may be caused by either intrinsic (e.g. stomach acid) or extrinsic (e.g. dietary) sources. Erosion is often associated with the consumption of acid products, such as fruits or acid beverages, or with medical conditions where reflux of acidic into the oral cavity is present. Interestingly, the term erosion is widely used in other fields where the definition is rather different. For example, in the field of tribology, erosion refers to the loss of material from a surface by solid or liquid impacts [6], In the classical tribological definitions, the mechanism dentists refer to as erosion would be described as corrosion, or tribo-chemical wear. 

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