Microbial attack of orthodontic adhesives.

Composites used as orthodontic direct bonding adhesives have a polymeric matrix that can host and nurture a variety of aerobic and anaerobic microorganisms acting alone or in combination (consortia). Their accumulation can lead to the weakening of the bond and possibly the attacking of the tooth. A number of microorganisms have been identified as present on the removed direct bonding brackets. Their action has been duplicated in vitro. Although some are specific to the oral environment, others are "opportunistic," i.e., have external sources. The results of attempts to detect the origin of the latter suggests a contamination of iatrogenic origin. Thus a high percentage of attacked adhesive can be traced to specific orthodontic offices, a fact that could be indicative of a breach in the sterilization procedures. While the attack of microorganisms on orthodontic adhesives is spectacular, less obtrusive inroads are likely to occur whenever similar acrylic composites are used in general dentistry, i.e., in restorations, veneers, and crowns. Indeed, it has been found that neither these polymeric products, nor some of the ingredients used to make them, exhibit a bacteriostatic activity, being metabolized instead. Results of rendering the adhesive microbe-resistant by adding a bactericide have shown to be encouraging.