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Secondary caries is the primary reason for replacement of composite fillings, and clinical studies report more secondary caries when composites are used compared to amalgam in high-risk caries groups. This highlights the need for development of materials that will reduce or inhibit biofilm formation on dental materials.

The challenges of antibacterial agents in dental materials can be many:
• The agent must be present in a concentration that inhibits or reduces biofilm formation.
• The concentration must not exceed cytotoxic level.
• The aesthetic, mechanical and chemical qualities of the material must not deteriorate.
• The effect should not be limited in time.

We are currently investigating the inhibitory effect of chitosan on biofilm formation; an interesting antimicrobial agent which may fulfil the criteria described above (Figure 1). Chitosan is a natural carbohydrate polymer derived from the deacetylation of chitin. Chitosan have different degrees of deacetylation and molecular mass, and is produced commercially from crab and shrimp shell wastes. Because of chitosan’s promising biological activities, including non-toxicity and antimicrobial activity, it is used for a variety of purposes in food production, medicine, agriculture, cosmetics and biotechnology. The antimicrobial properties are thought to be due to positively charged amino groups, NH3+, participating in an electrostatic interaction with negatively charged groups on the cell surface of the bacteria. This may damage the cell wall and change its permeability and barrier properties allowing the cell contents to leak out. Chitosan has shown antimicrobial effect against oral bacteria and is tested for use as an antimicrobial agent in composites and other dental materials and oral hygiene products.

Experiments with low viscosity chitosan have shown an antibacterial dose-response effect after being dissolved in culture media at various concentrations (Figure 2) and reduced biofilm when coated on polystyrene discs. We are currently investigating the use of chitosan in dental composites.


Reference
Dragland IS, Kopperud HM. Chitosan – antibakteriell bruk i dentale materialer. In: Holmstrup P (ed.),
Odontologi 2015 – Aktuel Nordisk Odontologi, København, Munksgaard, 2015; pp. 97–109.
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