Locally-Delivered Sustained-Release Antimicrobials

Controlled clinical trials have consistently shown that locally-delivered sustained-release antimicrobials, along with scaling and root planing, have been shown to provide a clinically and statistically significant increase in the percentage of patients achieving predetermined periodontal benefits, than does scaling and root planing alone.¹⁵ Some trials have also shown that an agent alone can reduce probing depths as much as SRP alone.¹⁶ Generally, it is agreed that these agents provide better outcomes than SRP alone in sites where patient access for plaque control might otherwise be limited; i.e. wherever pocket depths are 2 mm or greater. Improved outcomes can be obtained with these products during both active and maintenance therapy. Bacterial resistance to antibiotic therapies have not been reported, but resistance concerns can be avoided by the use the locally-delivered sustained-release antimicrobial containing chlorhexidine, an antiseptic rather than an antibiotic which is not known to induce the emergence of resistant strains.

There remains a question as to whether these agents are appropriate for routine use or for only those instances where previously available therapies may fail. Generally, surgical needs are assessed after the patient receives optimal non-surgical therapies. All appropriate strategies should be considered in the effort to control a chronic disease like chronic periodontitis.

Examples of these products which have been available in the U.S. include tetracycline fibers, chlorhexidine chip, doxycycline polymer, and minocycline microspheres.

A 3 month phase II clinical trial found that 0.4% moxifloxacin gel, a fourth-generation fluoroquinolone, administered in a single subgingival administration adjunctive to scaling and root planning, resulted in additional pocket depth reduction compared with scaling and root planing plus a placebo gel.²⁰ Moxifloxacin is a broad spectrum antimicrobial active against aerobic and anaerobic bacteria. These results would need to be confirmed in a phase III clinical trial. Phase II trials generally assess efficacy and dose response prior to designing a larger phase III trial. Phase III studies are generally randomized controlled multicenter trials on larger groups of patients. The goals of a phase III trial usually compares efficacy as compared to the current gold standard treatment.

Another 9 month clinical trial indicated that microsphere formulation of doxycycline provided both a more sustained release and a high initial drug concentration as compared with doxycycline gel. All three groups (scaling and root planing alone, doxycycline microspheres and doxycycline gel) showed improvements in relative attachment levels at 9 months. The group receiving scaling and root planing plus doxycycline microspheres showed significantly greater gain in relative attachment levels than the other groups.²¹ Again further research is needed comparing other agents and delivery systems.