Root canal system disinfection is limited due to anatomical complexities. Better delivery systems of antimicrobial agents are needed to ensure efficient bacteria eradication. The purpose of this study was to design chlorhexidine-containing nanoparticles that could steadily release the drug. The drug chlorhexidine was encapsulated in poly(ethylene glycol)–block–poly(l-lactide) (PEG–b–PLA) to synthesize bilayer nanoparticles. The encapsulation efficiency was determined through thermogravimetric analysis (TGA), and particle characterization was performed through microscopy studies of particle morphology and size. Their antimicrobial effect was assessed over the endodontic pathogen Enterococcus faecalis. The nanoparticles ranged in size from 300–500 nm, which is considered small enough for penetration inside small dentin tubules. The nanoparticles were dispersed in a hydrogel matrix carrier system composed of 1% hydroxyethyl cellulose, and this hydrogel system was observed to have enhanced bacterial inhibition over longer periods of time. Chlorhexidine-containing nanoparticles demonstrate potential as a drug carrier for root canal procedures. Their size and rate of release may allow for sustained inhibition of bacteria in the root canal system.

Aim: To encapsulate an antibiotic in oral applications with PEG/PLA‐block copolymer into microparticles for infected dentin tubules. To maintain drug release for extended periods to prevent bacterial regrowth after root canal treatment. Methodology: Drug encapsulation was carried out through an oil‐water emulsion‐solvent evaporation method. In summary, the PEG/PLA copolymer and the oral drug were dissolved in an oil phase (dichloromethane), which was combined with an aqueous (polyvinyl alcohol and de‐ionized water). The solution was stirred, centrifuged, washed, and lyophilized. Particle size was determined using digital microscopy. Antimicrobial effectiveness was assessed in vitro by placing small amounts of encapsulated particles on bacterial agar plate cultures and monitoring growth inhibition. Results: Encapsulated particles ranged in size from 300 nm to 1.0 m. A 2 week bacterial inhibition test showed that the particles exhibited zones of inhibition between 3 mm and 5 mm. Conclusion: The proposed method with the PEG/PLA copolymer encapsulates the oral antibiotic producing particles with size distribution that may penetrate the dentinal tubules (2.5 m in diameter). Bacterial inhibition tests showed that the particles inhibited bacterial growth after 2 weeks. Ongoing bacterial inhibition tests will determine the release profile of the microparticles.

Encapsulation of Biological Stains for Drug Delivery Imaging and Microscopy in Dentin Tubules Michael Lau1, Ridwan Haseeb1, Francisco Montagner2, Danieli Rodrigues1: 1Department of Bioengineering, University of Texas at Dallas, Richardson, TX; 2Department of Conservative Dentistry, Federal University of Rio Grande do Sul, Brazil; Introduction: Bacteria are able to remain into dentin after the root canal disinfection. Drug penetration into the tubules can be a key component for infection control. This study uses the synthesis of poly(ethylene glycol)‐block‐poly(L‐lactide) PEG/PLA encapsulated biological stain particles to characterize the penetration depth of drug delivery systems with Confocal Laser Scanning Microscopy (CLSM). Methodology: Encapsulation of the biological stain was done with an oil‐water emulsion‐evaporation technique. The PEG/PLA copolymer and the stain were dissolved in the oil phase while the surfactant was dissolved in water. The oil phase and water phase was combined and emulsified then stirred. The particles were centrifuged, washed, and lyophilized. Characterizing the particle size and fluorescence was done with CLSM (VK‐X200 Keyence Laser Scanning Microscope). Results: The microscopy has shown particle formation in the 0.3‐1.0 m range, which depended on the method of emulsification: homogenizing or sonication. CLSM revealed that the particles fluoresce under light with 525‐605 nm wavelengths. Conclusion: The encapsulation technique effectively encapsulated the biological stain to penetrate the dentin tubules. With particle size similar to dentin morphology, the encapsulated stain proliferation into the dentin tubules will model dentin penetration of drug delivery systems of similar size.