Outcomes of Periodontal Treatment in Patients with Rheumatoid Arthritis (OPERA) was a pilot randomized controlled trial (RCT) that aimed to assess the feasibility for a larger, multi-center RCT which would investigate the efficiency of non-surgical periodontal treatment in reducing disease activity levels in patients with rheumatoid arthritis (RA). The OPERA trial used a mixed methods approach. The quantitative approach delivered pilot data regarding the clinical outcomes of the intervention, whilst the role of qualitative data was to provide a better insight into the experiences and values of the patients that would encourage their participation in the larger, definitive study. The findings of this trial highlighted the specific issues of the patient population, the logistic challenges and provided some possible solutions to facilitate patient participation.

Biological effects are known to occur with ultrasound energy at kilohertz frequencies. This has led to research into its use as a non-invasive tool for tissue healing and repair. The aim of this research is to investigate the in vitro application of kilohertz ultrasound and to measure the biological responses using models of dental pulp cells which play an important role in dental repair. Ultrasound emitted from a longwave therapy instrument (DuoSon, SRA Developments Ltd) was characterised and measured identifying the range and intensity of the field. These measurements, coupled with biological data, identified the difficulties when conducting research with kilohertz ultrasound in vitro and indicated that the use of multi-well culture plates is not appropriate when investigating the effects of kilohertz ultrasound in cell culture. An improved method for in vitro kilohertz ultrasound application was devised enabling the investigation of non-thermal ultrasound effects on primary human dental cells. Cell proliferation, viability and gene expression, including the dental-related and biomechanically-responsive gene, dentine matrix protein-1, responded in a dose-dependent manner with respect to the duration of ultrasound application. These findings highlight the complexity of the biophysical interaction of kilohertz ultrasound with cells and demonstrate the need for further clarification of specific ultrasound settings for optimal therapeutic application. This study has demonstrated a positive effect of kilohertz ultrasound on human dental pulp cells and has identified methods to improve in vitro cell culture models to capture robust data to develop a novel therapy for dental repair.

Current treatment of epithelial wounds utilise biomimetic materials, cells or a combination of both. This project aimed to examine the feasibility of incorporating mesenchymal stem cells (MSCs), isolated from adipose tissue and dental pulp, and induced pluripotent stem cells (iPSC)-derived cells into 3D organotypic cultures, as reports suggest MSCs facilitate wound healing and can generate constituent cells. The effect collagen hydrogels containing MSCs on H400 epithelial cells seeded on its surface was assessed. Fixed H&E-stained sections of organotypic cultures were used to determine epithelial maturation and thickness using image analysis. iPSCs generated using the STEMCCA lentivirus were assessed by gene expression analysis and immunofluorescent staining for pluripotent capabilities and keratinocyte differentiation. MSCs incorporated into collagen hydrogels exerted no effect on epithelial thickness. iPSCs generated from mouse adipose-derived stem cells (mADSC- iPSCs) expressed pluripotency markers and were capable of differentiating down embryonic lineages. Keratinocytes generated from mADSC-iPSCs expressed cytokeratins, but were unable to be cultured in 3D organotypic cultures. This thesis highlighted the importance of characterising stem cells when investigating their therapeutic potential. Future work will involve characterising MSCs and evaluating their effects on epithelial cell growth. Furthermore, the effects of iPSC-derived keratinocytes must be determined to exploit them for regenerative therapies.

Portland cement (PC) is generally known for its various applications in the construction industry. However, since mineral trioxide aggregate (MTA), a PC based root filling material, obtained food and drug administration (FDA) approval in the late 1990’s there has been an increased interest in the use of the cement for other in vivo applications. PCs are durable, possess high compressive strengths, set in aqueous environments such as those found in vivo and have demonstrated desirable tissue responses as an endodontic sealant. The injectability of PC with various additives was investigated for use in clinical applications such as vertebroplasty (the stabilisation of a fractured vertebra with bone cement) using a syringe with a 2 mm aperture. Additives significantly improved cement injectability, decreased setting times from over 2 h to below 20 minutes while maintaining the compressive strength of the material. Cement characterisation methods including X-ray diffraction (XRD), helium pycnometry and zeta potential measurements were employed to elucidate the effect of the additives on the cement setting reaction. The biocompatibility of PC was investigated with fibroblast and bone marrow cells. The freshly mixed cement appeared cytotoxic while set cement upregulated genes associated with the osteogenic phenotype.

Current methods of dental biofilm removal are predominantly mechanical and are not effective in removing it from irregular surfaces in the mouth. Cavitation occurs around dental ultrasonic scalers and may be a more efficient and less damaging technique. Previous work has failed to quantify the cavitation bubble dynamics around ultrasonic scalers and its effects. The aim was to develop imaging and analysis protocols to analyse the cavitation and to investigate its ability to disrupt biofilms and deliver sub-micron particles into dentine. High speed imaging was used to characterise cavitation. Its effect on biofilm removal and dentinal tubule occlusion was studied using electron microscopy and x-ray micro computed tomography. We are able to demonstrate that cavitation occurs at the free end of scaler tips and increases with power and vibration amplitude. Biofilm can effectively be removed from dental implant surfaces using this cavitation. It can also be used to transport sub-micron particles further into dentinal tubules. The results show that ultrasonic scalers could be optimised for non-contact use and improved removal of plaque from the teeth. The protocols established in this study can be applied to future studies for quantitative investigation of biofilm growth and removal and analysis of cavitation dynamics.