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Implant with slow-release drug reservoir reduces infection

22 February 2017

Implant with slow-release drug reservoir reduces infection

SScientists have developed a dental implant containing a reservoir for the slow release of drugs. Laboratory tests in which the reservoir slowly released a strong antimicrobial agent showed that the new implant can prevent and eliminate bacterial biofilms - a major cause of infection associated with dental implants.

The researchers, from various departments at KU Leuven in Belgium, describe how they designed and tested the implant in a paper published in the journal European Cells & Materials.

Lead author Dr. Kaat De Cremer, from the Centre of Microbial and Plant Genetics at KU Leuven, explains that the reservoir in the implant can be filled by removing the cover screw. She adds that:

"The implant is made of a porous composite material, so that the drugs gradually diffuse from the reservoir to the outside of the implant, which is in direct contact with the bone cells. As a result, the bacteria can no longer form a biofilm."

In general, bacteria have two life-forms. In one, the planktonic state, they exist as single, independent cells, and in the other, they aggregate in a slime-enclosed mass called a biofilm.

Biofilms are notoriously stubborn and hard to treat, and when they become chronic, they are extremely resistant to antibiotics.

Mouth infections are often cited as the main reason why dental implants fail. This has led to research looking for ways to protect against infection - by developing an antimicrobial coating for the implant, for example.

Implant prevents and eliminates biofilms

In their study paper, the researchers note that implant developers are increasingly using materials with rough surfaces because they enlarge the contact area - thus improving anchorage with bone cells and integration into the bone. However, greater surface area also raises the risk of biofilm development.

The new implant is a composite of a silicon-based "diffusion barrier" integrated into a porous, load-bearing titanium structure.

The researchers subjected the implant to various laboratory tests, during which they filled the reservoir with chlorhexidine, a powerful antimicrobial commonly used as an oral rinse or mouthwash.

Tests showed that the chlorhexidine-filled implant stopped Streptococcus mutans - a common mouth bacterium that attacks teeth - from forming biofilms. It also eliminated biofilms that were grown on the implant before loading the reservoir.

Researchers say that the results prove that the implant is effective at both preventing and eliminating biofilms, and it may potentially be able to prevent and cure infections in patients.

Implant design suits personalized treatment

In a discussion with reviewers that accompanies the study paper, the authors point out that their work is a "proof of principle" based on tests done in the laboratory. Further research should now be done to show that the implants are effective in patients.

This needs to address several issues, including whether the new material fulfils the mechanical requirements of dental implants, and whether there is a risk of protein and calcification clogging up the pores.

The team also notes that the design of the titanium silicon composite implant suits personalized treatment; different drugs can be loaded into the internal reservoir, depending on the patient's individual need.

The authors conclude that:

"This study focuses on dental implant applications, but the concept could, in principle, be translated to any percutaneous implant that can incorporate an internal reservoir, such as percutaneous fixation devices, as long as this does not compromise the mechanical strength of such load-bearing devices."

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