Dr Chris Hope BSc (Hons), PhD, FHEA

Dental plaque is a complex microbial habitat containing many hundreds of different species of bacteria within the biofilm. Modelling dental plaque requires specialist knowledge and equipment. It is possible to modify the model in order to mimic the oral environment in conditions of health, caries (tooth decay) and periodontitis (gum disease). The constant-depth film fermenter is used in our group to model dental plaques which can then be subjected to various external influences to model the effects of antimicrobials, diet, inflammation etc.

Conventional models of tooth decay involve the immersion of tooth enamel into various acidic solutions. Although reproducible, this technique does not correctly mimic the production of a gamut of organic acids which are produced by a microbial biofilm growing on the tooth surface being subjected to periodic cycles of feast (i.e. supplied with dietary carbohydrates) and famine (i.e. between meals) with the continual flow of saliva acting as a buffer. A novel application of the CDFF has been to model this complex situation by pumping sugars into the system as a series of pulses. This model is able to produce caries-like lesions within 10 days. This model can be used for studying the effects of dietary supplements and anti-caries agents, such as fluoride.

We have also worked with validate models of endodonitic irrigation using extracted human teeth.

https://www.ncbi.nlm.nih.gov/pubmed/28245470
https://www.ncbi.nlm.nih.gov/pubmed/22716966
https://www.ncbi.nlm.nih.gov/pubmed/20971137
https://www.ncbi.nlm.nih.gov/pubmed/20652229
https://www.ncbi.nlm.nih.gov/pubmed/17908949
https://www.ncbi.nlm.nih.gov/pubmed/16487610
https://www.ncbi.nlm.nih.gov/pubmed/15691977
https://www.ncbi.nlm.nih.gov/pubmed/15105093
https://www.ncbi.nlm.nih.gov/pubmed/12931764
https://www.ncbi.nlm.nih.gov/pubmed/12842487
https://www.ncbi.nlm.nih.gov/pubmed/12834500
https://www.ncbi.nlm.nih.gov/pubmed/12516675
https://www.ncbi.nlm.nih.gov/pubmed/12174043

Many of the most powerful antibiotics have been rendered impotent due to the emergence of resistant organisms and we are in danger of entering the “post-antibiotic era”. Lethal photosensitisation has been proposed as a possible alternative to antibiotics. LP involves the production of free-radicals and reactive oxygen species when excited by light photons. These free-radicals can then react with nearby cellular targets and result in cell death. There are two approaches to this treatment modality. Firstly, photosensitiser molecules can be added to the target organism. The second approach is to seek to kill bacteria using any photosensitive molecules which they might already be producing. An example of this second approach is to utilise protoporphyrin IX which is produced by a number of periodontal pathogens, such as Porphyromonas gingivalis and Prevotella intermedia. These organisms have been shown to be photosensitive to 405 nm light and we are looking to optimise this process.

https://www.ncbi.nlm.nih.gov/pubmed/26216344
https://www.ncbi.nlm.nih.gov/pubmed/24284127
https://www.ncbi.nlm.nih.gov/pubmed/19411679
https://www.ncbi.nlm.nih.gov/pubmed/16549510
https://www.ncbi.nlm.nih.gov/pubmed/15983029
https://www.ncbi.nlm.nih.gov/pubmed/12210591

A number of biological molecules fluoresce under appropriate lighting / viewing conditions. This phenomenon can be utilised to visualise bacteria. Spectral analysis provides supplementary information which allows the presumptive identification of particular fluorophores and may be able to reveal details of the local environment, particularly pH - which is a very important consideration for dental plaque and infected wounds.

Quantitative Light-Induced Fluorescence (QLF) has been used by our research group for almost 20 years to image dental plaque. We have developed and refined this technique in collaboration with the manufacturer. We have also sought other (non-dental) applications for this technology. This methodology has been taken to the next level using fluorescence hyperspectral imaging which reveals spectral information at the pixel level.

https://www.ncbi.nlm.nih.gov/pubmed/27552307
https://www.ncbi.nlm.nih.gov/pubmed/27441707
https://www.ncbi.nlm.nih.gov/pubmed/24511282
https://www.ncbi.nlm.nih.gov/pubmed/21198645