(48) It is speculated that chitosan can build up a protective organic layer through interaction with enamel and proteins from the acquired pellicle. (49,50) Moreover, due to its lubricating effects, it may reduce the abrasivity of dentifrices by binding to the silica particles or the tooth surface.
The effective blocking of acidic groups of salivary glycoproteins will reduce their adsorption to hydroxyapatite and the formation of acquired pellicle.
This coating is called as acquired pellicle. Then the primary colonizers, first streptococci and later actinomycetes, colonize the surface of the teeth by adhesion molecules and pilli.
Minocycline may etch the tooth surface through long-term contact by attaching to glycoproteins in the acquired pellicle. It then may become oxidized on exposure to oxygen or bacterial activity.(26) Minocycline is also found in gingival fluid at a concentration five times that of serum and may intrinsically stain the enamel by diffusing through the pulp.(24) Minocycline's strong affinity for iron and its ability to form insoluble salts also may play a role.(23)(25)