Research
Development of dental plaque microcosm biofilms for drug delivery and therapeutic testing |
|
 |
We develop microbial biofilms evolved in vitro from saliva and subgingival plaque inocula. These biofilms are reproducible, analogous to that of natural dental plaque and provide a means for testing drug delivery and therapeutic procedures. |
Structure of the biofilm on day 5 of its development as it was observed by scanning electron microscopy |
|
Study of biofilm anatomy by Confocal Reflectance Microscopy |
|
 |
In confocal reflectance microscopy biofilms are illuminated by a laser source and backscattered (or reflected) light is collected by a detector. Image contrast is determined by natural differences in refractive indices of various structures within biofilms. Gray-scale images are displayed in real-time on a video monitor and represented horizontal (en face) optical sections through the biofilm. |
Bacterial aggregates (B), fluid channels (C) and extracellular matrix (M) are clearly observed by confocal reflectance microscopy . |
|
Selective phototargeting of microorganisms in dental plaque |
|
 |
We have proposed the use of visible (blue) light as a bactericidal agent in vivo to eliminate dental plaque pathogens by activating their endogenous porphyrins. The selective inhibition of the growth and metabolism of these species may lead to biofilm disruption and eventually to decreasing the pathogenic bacterial load. The result will be the prophylactic stabilization of the normal microbial composition of the plaque, even under conditions that may otherwise predispose a site to periodontitis. |
For our preliminary clinical studies, an intraoral light source was designed and constructed to irradiate dental plaque on bicuspid and molar teeth by directing light from the buccal side |
|
Photodynamic therapy of chronic periodontitis |
|
 |
Periodontitis is a destructive chronic inflammatory condition of the supporting structures of the teeth that arises as the result of the interaction of microorganisms and their products in dental plaque (periodontal biofilm) with host defense mechanisms. Our goal is to develop a photochemotherapeutic system for the treatment of periodontitis. A photoactive compound or “photosensitizer” could be introduced into the dental pocket followed by red light illumination via an optical fiber (photodynamic therapy or “PDT”). This technique would offer the following advantages in the hypothetical case of its in vivo application: (a) rapid application of the drug in the dental pocket and rapid bacterial killing after a short time of exposure of the dental pockets to light; (b) killing could easily be confined to the lesion by restricting irradiation to this region, so that microflora at other sites would remain intact; and (c) light would be delivered topically, rapidly and non-invasively. Our current work is focused on the photosensitization of periodontal biofilms in vitro using a series of different photosensitizers. |
Photodynamic therapy for endodontic disinfection |
|
 |
Endodontic failures are caused by the proliferation of residual bacteria that are left behind within the root canal due to the complexity of the root canal system that makes complete debridement with instrumentation and irrigation alone almost impossible. More than 2 million root canal retreatments due to residual microorganisms are performed yearly in the US. PDT may be an adjunctive procedure to kill residual root canal bacteria after their sensitization with a photoactive drug and their subsequent exposure to light. We envision the application of PDT in clinical practice as follows. The photoactive drug will be applied in the root canal system after instrumentation is complete for a short time (up to 5 minutes) and will strongly bind to the negatively charged matrix and to bacteria. Then a fiber optic will be used to deliver red light from a diode laser to irradiate microbial biofilms on the root canal surface as well as in the dentinal tubules. The entire root canal system will be exposed to light simultaneously for 5 minutes. |
Practical demonstration of light delivery in the root canal of an extracted tooth using a fiber optic |
|
Photomechanical drug delivery into oral microbial biofilms |
|
 |
Photomechanical waves (PW) generated by ablation with high power lasers are fast rise time compressional waves whose effects are caused by mechanical forces. Recently, we have shown that PW enhance the permeability of microbial biofilms. The combination of PW delivery and PDT has been shown to disrupt resistant biofilms. We have proposed that the synergistic action of PW and PDT can be used as a powerful treatment tool for control of infections. Some of the potential applications to infectious diseases are: dental caries, periodontitis, cystic fibrosis pneumonia, native valve endocarditis, as well as infections of contacts lenses, urinary catheters, endotracheal tubes, vascular grafts, mechanical heart valves, and orthopedic devices. |