Pellicle, acquired

The bond strength to enamel (2-6 to 9-9 MPa) is greater than that to dentine (1-5 to 4-5 MPa) (Wilson McLean, 1988). Bond strength develops rapidly and is complete within 15 minutes according to van Zeghbroeck (1989). The cement must penetrate the acquired pellicle (a thin mucous deposit adherent to all surfaces of the tooth) and also bond to debris of calciferous tooth and the smear layer present after drilling. Whatever the exact mode of bonding to tooth stmcture, the adhesion is permanent. The principles and mechanism of adhesion have already been discussed in Section 5.2. 

T. Sonju and G. Rolla, Chemical analysis of the acquired pellicle... 

Besides taking part in acquired pellicle formation on tooth (denture, implant) surfaces, MUC5B type mucins cover all oral surfaces with a 10-20- im thick layer. In addition, MUC5B type mucins form a hydrophilic viscoelastic gel (already in low concentration) that causes a high viscosity matrix of saliva. 

That minocycline attaches to the acquired pellicle glycoproteins (the extrinsic theory ) (8). This in turn etches the enamel, and cycles of demineralization and remineralization occur. It oxidizes on exposure to air or as a result of bacterial activity, and the final product is insoluble black quinine. 

The calculus reviews cited earlier [1, 16, 30, 31] discuss the role of saliva and its constituents in the context of mineral formation and dissolution in plaque. Other authors have reviewed saliva with respect primarily to dental caries [e.g. 54, 55], caries models [56, 57] and the acquired pellicle [58]. 

The most important components are probably the proteins, and the possible roles of these molecules in caries, in particular, have been studied extensively. An obvious inhibitory function of the salivary proteins is the formation of an adsorbed layer on the teeth, the acquired pellicle. For more details on the composition and function of pellicle the reader is referred to chapter 2 and ref. 58. 

Formation of the acquired salivary pellicle is the result of biopolymer adsorption at the tooth-saliva interface. The term acquired pellicle was first suggested in a review of the nomenclature of the enamel surface integuments by Dawes et al. [1], to describe the cuticular material formed on the enamel surface after eruption. The pellicle consists of adsorbed proteins and other macromolecules from the oral environment (saliva, crevicular fluids) and is clearly distinguished from the microbial biofilm (plaque) (fig. 1). 

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 formation is determined by adsorption of components from saliva, crevicular fluid and bacteria onto the enamel surface [2-13], Formation of the acquired pellicle is a highly selective process, since only a fraction of the proteins available in saliva is found in the pellicle [14,15],... 

Fig. 7. Atomic force microscope image of the acquired pellicle layer formed on an enamel specimen mounted at the palatal site of the upper first molar and exposed to the oral environment for 10 min. The pellicle surface is characterised by a densely packed layer of globularly shaped particles of 15-30 nm diameter. 

Sonju T, Rolla G Chemical analysis of the acquired pellicle formed in two hours on cleaned human teeth in vivo. Rate of formation and amino acid analysis. Caries Res 1973 7 30-38. 

Kraus FW, Orstavik D, Hurst DC, Cook CH The acquired pellicle variability and subject-dependence of specific proteins. J Oral Pathol 1973 2 165-173. 

Orstavik D, Kraus FW The acquired pellicle enzyme and antibody activities. Scand J Dent Res... 

Armstrong WG Origin and nature of the acquired pellicle. Proc Royal Soc Med 1968 61 923—930. 

Leach SA, Saxton CA An electron microscopic study of the acquired pellicle and plaque formed on the enamel of human incisors. Arch Oral Biol 1966 11 1081-1094. 

Finke M, Parker DM, Jandt KD Influence of soft drinks on the thickness and morphology of in situ acquired pellicle layer on enamel. J Colloid Interface Sci 2002 251 263-270. 

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. 

Rykke M, Ellingsen JE, Sonju T Chemical analysis and scanning electron microscopy of acquired pellicle formed in vivo on stannous fluoride treated enamel. Scand J Dent Res 1991 99 205-211. 

The surfaces of the mouth are coated with a layer of salivary proteins known as the acquired pellicle, which provides a protective effect from both chemical and mechanical attacks to the tooth surface. The pellicle layer both moderates diffusion of ions away from the tooth surface, thus inhibiting the dissolution of enamel by erosion, and provides a lubricating layer to protect from mechanical attacks [10, 11], It is known that dental prophylaxis and the use of regular oral hygiene procedures are able to reduce or remove the pellicle layer. However, recent evidence has shown that the pellicle is able to re-form very rapidly and thus, maintain a protective layer over the tooth surface [10]. For this reason, tooth wear studies performed in vivo or in situ, where the mediating effects of pellicle are present, will give a much more realistic assessment of tooth wear than in vitro studies. For a more detailed discussion on the effects of pellicle, see chapter 2. 

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