Staining, pellicle

The addition of therapeutic or cosmetic agents to dentifrices has paralleled advances in knowledge about factors affecting the human dentition. Agents added to dentifrices can act directly on the host tooth stmcture or on specific oral accumulations, for example, the principal action of fluoride is on the tooth enamel. The primary action of an abrasive, however, is on an accumulated stained pellicle. Oral accumulations of interest to preventive dentistry are dental pellicles, dental plaque, dental calculus (tartar), microbial populations responsible for oral malodor, and oral debris (food residues, leukocytes, etc). Plaque is most important because of its potential to do harm. 

Only limited information is available from the literature concerning the behaviour of the pellicle during daily brushing of the teeth with a dentifrice. It has been reported from in vitro and in vivo studies that brushing with commercially available dentifrices significantly reduces the pellicle film quantity and its thickness [170-174], Conversely, brushing with a nonabrasive dentifrice leads to a thick and often-stained pellicle [139, 175],... 

Abrasive. Dentifrices have the unique ability to remove extrinsic tooth stains, which are caused by agents such as berries, tea, smoking, antibiotics, and certain bacteria as they attach to the dental pellicle. These stains can be removed only by abrasive cleaning a toothbmsh alone is not adequately effective. It has been shown that only 4% of a test population were able to maintain thein teeth in an acceptably stain-free state without an abrasive and that 18% of the population were "heavy" stainers (2). However, colored materials found in dental plaque are removable without abrasives. 

This review covers the formation, composition, structure, function and properties of the acquired pellicle. Specifically, the formation of pellicle is considered in terms of thermodynamic and kinetic aspects. The composition of the pellicle is reviewed in terms of the proteins, carbohydrates and lipids that have been identified using a range of analytical techniques. The ultrastructure of the pellicle is described in some detail from studies involving enamel slabs carried in the mouth, in which the subsequent pellicle was analysed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and confocal laser scanning microscopy (CLSM). The function of the pellicle is outlined in terms of its lubrication properties, its ability to act as a semi-permeable membrane and its overall protection of the underlying enamel surfaces. Since pellicle is formed at the interface between the enamel surface and the oral environment, the important process of bacterial attachment to the pellicle surface is described and the specific bacterial binding sites found in the pellicle are summarised. The influence of diet and nutrition on the pellicle layer is considered. The formation of extrinsic stain is discussed in particular, the role that chlorhexidine... 

Pellicle has a tendency to develop stain, termed extrinsic stain, particularly in those areas of the dentition which are inaccessible to toothbrushing and the abrasive action of a dentifrice [137-139], Extrinsic staining has been reported to be promoted by smoking, dietary intake of tannin-rich foods (e.g. tea, red wine) and the use of certain cationic agents such as chlorhexidine, tin and iron [140-144], Proposed mechanisms of extrinsic stain formation have been reviewed over the years by a number of authors [140,145-148] and the focus of recent attention has been the staining associated with chlorhexidine. 

Nordbo H, Eriksen HM, Rolla G, Attramadal A, Solheim H Iron staining of the acquired pellicle after exposure to tannic acid or chlorhexidine preliminary report. Scand J Dent Res 1982 90 117-123. 

In Chapter 2 the structure and function of the acquired enamel pellicle are discussed. Recent work, aided by advances in analytical methodologies, has increased our understanding of pellicle formation and maturation, and how pellicle composition relates to saliva. The authors emphasize the important role played by pellicle in plaque attachment, tooth protection and stain formation. The authors also describe research on the potential effects that dentifrices can have on pellicle. 

Pellicle stains positively for carbohydrate and protein and appears to be derived from the salivary proteins. Its amino acid composition is similar to that of a typical glycoprotein and it contains hexoses, hexosamines and fiicose. However, the glucose/galactose ratio differs from that in saliva and it has been suggested that the pellicle consists of a specific salivary glycoprotein fraction whose oligosaccharide side chains are resistant to enzymic degradation. 

At present chlorhexidine is the agent of choice in the short-term control of supragingival plaque although it is not without its disadvantages. It adsorbs to a pellicle-covered enamel and to the surface of calculus and subsequently reacts with dietary components to produce a persistent brown stain. In addition, some patients report a burning sensation and loss of taste after prolonged use. 

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