Photobiomodulation (PBM) with near-infrared lasers or light-emitting diodes (LEDs) has been proposed to support local analgesia and anaesthesia by modulating cellular activity, enhancing tissue repair, and reducing inflammation and pain perception. This non-invasive technique holds promise for improving patient comfort during dental procedures and enhancing outcomes in regenerative treatments. Chapter 1 provides a comprehensive literature review on photobiomodulation (PBM), focusing on its principles, light sources, and laser classifications, as well as the interaction of light with dental tissues such as enamel, dentine, and oral mucosa. It explores the mechanisms behind PBM-induced analgesia and its potential role in regenerative endodontic therapy. The chapter also identifies gaps in current knowledge, particularly in PBM's application for dental pain relief and tissue regeneration, and outlines the study’s hypotheses and objectives. Chapter 2 systematically assessed current evidence for PBM-induced dental analgesia. Three key gaps were found: heterogenous or partially reported light parameters that have not been validated in vitro previously, heterogenous samples for both patient and tooth related factors, and subjective measures of analgesia. Additionally, several clinical variables have been overlooked in previous studies, including tooth shade, the location of the light delivery probe, tooth type, and patient-specific factors such as pre-existing chronic pain or neuropsychiatric conditions, all of which may significantly influence PBM efficacy. Chapter 3 was designed to explore the influence of tooth shade on near infrared light transmission through human dentine and enamel. The study used visible red and near infrared light, using single wavelength diode lasers (660, 808 and 904 nm) and a novel multiwavelength LED device designed for PBM (700 - 1100 nm). This study showed that within the range from 660 – 1100 nm, the longer wavelengths are transmitted better by both enamel and dentine. The transmission of visible red light (660 nm) was affected by tooth shade, while the transmission of near infrared light (700 – 1100 nm) was not affected by shade. Chapter 4 aimed to assess the effect of intra-canal medicaments on infrared light energy transmission through enamel and dentine during photobiomodulation. The study found transmission was compromised, through teeth treated with intra-canal medicaments, with significant reduction in enamel-dentine samples. The absorption of all single and multiwavelength PBM through intra-canal medicaments were greatest with calcium hydroxide. Chapter 5 assessed effectiveness of PBM-induced analgesia of teeth in a clinical trial. The study, following a robust repeated-measures design, with single wavelength diode lasers (660, 808 and 904 nm) and the multiwavelength LED device used to treat healthy unrestored premolar teeth in adults. The strongest analgesic effects occurred with the LED, both in terms of the size of the response, and the proportion of subjects showing elevated electric pulp test thresholds at various levels. At the same time, PBM with the LED did not cause any discomfort, unlike the 808 and 904 nm lasers, despite the same light exposure parameters being used. Chapter 6 explored PBM for prevention of pain from injection into the buccal attached gingival. A similar repeated measures design was used, but this time comparing in the clinical trial the LED PBM device to the current “gold standard” of 5% lidocaine topical gel. The PBM approach was more effective, with lower pain scores and more subjects reporting zero discomfort. It was also more predictable than topical gel. Chapter 7 looks at the limitations and future directions of the current work. Further in vitro cellular and molecular exploration of mechanism of action would help support clinical translation. Exploration of factors that can influence clinical application of PBM such as tooth size, type, and microstructural changes such as secondary dentine or sclerosis should be considered in future studies. Pain and dental anxiety experience is a complex subjective phenomenon in a dental setting, and as such further testing of PBM induced dental analgesia should be explored with various clinical applications for both oral mucosal and dental analgesia. This study provides evidence supporting the concept of PBM-induced dental analgesia, laying the groundwork for further research into clinical applications of multiwavelength LED devices and diode lasers. These devices have the potential to augment or even replace traditional topical or injected dental anesthetics, offering a means to reduce patient discomfort during treatments. Additionally, the findings suggest that PBM could be an effective tool in managing painful oral mucosal conditions, such as traumatic or aphthous ulcerations.