Saliva-enamel interactions

Saliva - Enamel Interactions. Enamel becomes adsorbed with a bacteria-free film almost instantaneously after contacting saliva. ) and is constantly renewable if... 

Food is taken into the buccal cavity, where it is masticated by the teeth and mixed with saliva from three pairs of salivary glands. It moistens the food and dissolves some molecules enabling them to interact with the taste receptors on the tongue. Saliva contains Na% Cl and HCOs ions and a protein, mucin, which is a component of mucus that lubricates the chewed food on its way down the oesophagus. The pH of saliva is about 7.8, which neutralises acid formed by bacteria in the mouth this protects tooth enamel... 

Ruan et al. [97] were unable to detect IgA amongst substances adsorbed onto enamel and cementum from saliva in vivo. This is perhaps not surprising since the mode of action of the antibodies is more likely to involve specific interaction with bacteria. 

The rapid initial phase of salivary protein adsorption is followed by a second, comparatively slower phase of protein adsorption onto the protein-coated enamel surface. The second stage of pellicle formation is characterised by a continuous adsorption of biopolymers from saliva. This process involves protein-protein interactions between already adsorbed proteins, immobilised in the pellicle layer, and proteins as well as protein aggregates from saliva. Amino acid and Auger analyses of the pellicle layer formed on buccally carried enamel slabs [18] indicate that the adsorbed proteins reach an initial thickness in about 2-3 min, and stay at that level for about 30 min. The thickness of the pellicle then increases to about three times its initial thickness and reaches a plateau after 30-90min [5, 18, 27], Within 60min, the thickness of the in situ-formed pellicle will further increase to between 100 and lOOOnm [17, 28], dependent on the supply of locally available salivary biopolymers and the prevailing intraoral conditions [17,28,29] (fig. 2). 

A simplified description of the etiology of dental caries involves metabolism of sugars by oral microorganisms to acids which gradually dissolve tooth enamel. However, it is now recognized that a number of dietary factors and nutrient interactions can modify the expression of dental caries (Herod, 1991). The cariogenic potential of food is infiuenced by its composition, texture, solubility, retentiveness, and ability to stimulate saliva flow (Morrissey et al, 1984). 

Saliva - Dental Materials Interactions. Besides enamel and other tissues, surfaces from metallic, polymeric, and ceramic dental materials are capable of becomimg adsorbed with organic films. Germanium and silica infrared spectrometer prisms formed oral films at high speeds and were... 

Glass-ionomers not only release ions, but are capable of taking them up. Studies have shown that cements exposed to natural saliva take up calcium and phosphate ions, and develop a surface of significantly increased hardness [121]. Also, when used as pit and fissure sealants, they interact with saliva to form a substance with increased content of calcium and phosphate that is considerably more resistant to cutting with a dental drill than the original material. Under these circumstances, the cement had become transformed into a material with enamel-like optical and mechanical properties [122]. This observation is the basis of the development of glass-ionomer type materials with even further enhanced bioactivity, the so-called glass carbomers, which are discussed in Chapter 8. 

Dental calculi, i.e. calcifications of the dental plaque biofilm, contain various calcium phosphates, since these inorganic ions are provided by saliva or crevicular fluids. Although the pattern of calcification of oral microorganisms, either intra- or extracellularly, is mainly a characteristic of each bacterial species or strain [75], it may be influenced by nutritional factors, such as saliva proteins, as well [76]. The interactions of saliva with dental calculi and its role in preventing dental caries by controlling the enamel de- and remineralisation processes have been reviewed [19]. 

The increasing trend in the consirmption of acidic soft drinks has led to the dissolution and softening of dental enamel, which is a phenomenon known as erosion. Recently a study has revealed that by the addition of food-approved pol5miers such as highly esterified pectin (1% w/w) to the citric acid solutions with a pH of typical soft drinks, the effect of citric acid on human dental enamel can be reduced [9], Similarly, interaction between the pectin coated liposome and dental enamel were also studied to find out the ability of the pectin-coated liposome to mimic the natural protective biofilm on the tooth surfaces. There were no aggregation tendencies for the pectin coated liposome and parotid saliva, which made them a promising device for the dental drug delivery. This ability of pectin-coated liposome to retain on the enamel surfaces also enhances their function as protective stmctures of the teeth [58]. 

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