Delivery of Antimicrobials in Root-canal Treatment

Addition of antibiotics to dental cements:

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The Mineral Trioxide Aggregate (MTA) is a dental cement used in root-canal obturations. It is of great interest to add antibiotics to MTA in order to prevent recurring infections after obturation. However, many antibiotics have been shown to degrade the mechanical properties of the cement. By using a special salt form of the antibiotic, we were able to retain both antimicrobial effectiveness (Figure 1) and mechanical stability. In this study, White Portland Cement (WPC), a representative material, was used in place of MTA. Future studies will involve validating the results using the MTA material.

Figure 1. 0.12% Antibiotic in Portland Cement sample. This figure demonstrates the ability of the modified cement to prevent the growth of E. Faecalis.

Design of Nanoparticles for Endodontic and Periodontal Treatments:

Part of a root canal therapy involves treatment that affects the metabolism of bacteria or eliminates it. Chlorhexidine (CHX) loaded nanoparticles (NP) can be used to treat and prevent infections after a root canal treatment. This is accomplished through local drug delivery systems based on biocompatible polymers to design the NP and a carrier solution that will disperse them. Fabrication of nanoparticle delivery systems is a critical step toward realization of nano-bio material engineering.

PEG–b–PLA bilayer nanoparticles (BNP) and trilayered nanoparticles (TNP) for CHX delivery have been successfully assembled (Figure 1) to improve drug bioavailability and target drug delivery to dentin tubules.

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Figure 2. Morphological analysis of CHX-encapsulated bilayer and trilayer nanoparticles using atomic force microscopy (AFM). (a) 2D, (b) 3D surface topography of BNP. (c) 2D, (d) 3D surface topography of TNP.

This synthesis of BNP allowed for the sustained inhibition of bacteria that could potentially be used in root canal systems. The BNP employed featured a hydrophobic interior space that easily encapsulated CHX, a hydrophobic drug; while the TNP incorporates the hydrophilic version of CHX, chlorhexidine – digluconate.

Our current work is focused on developing NPs that have highly packed coronas to reduce the diffusion rate of the water-miscible CHX-digluconate. This is being achieved by strengthening the entanglement of PLA on TNPs.

Another important aspect of this work is the development of a continuous phase gel matrix that can entrap and delivery the NP to the deepest part of dentin that would facilitate bio-adhesion of the NP at different sites. Once this NP reach all the areas that need to be covered within the dentinal matrix they will release their entrapped CHX. SEM studies on dentine (figure 2) are necessary to understand its morphology and determine the diameters and depths of dentinal tubules to establish the optimal properties of the NP gel matrix.

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Figure 3. SEM images of tubules found in dentine using VP (variable pressure aperture). (a) Dentinal tubules found on coronal surface of a tooth at a magnification of 4.49 kX (b) Dentinal tubules found on a sagittal sectioned teeth at a magnification of 5.65 kX.