Special issue on lasers in dentistry

A quiet revolution is taking place in dentistry through the progression and integration of wide-ranging biophotonics technologies into clinical practice and research. These advances can be broadly divided into three major areas: Diagnostics, Therapy and Device Design/Manufacturing. Given our current emphasis on precision dentistry, biophotonics-based approaches are very attractive, enabling tissue interrogation at levels ranging from structural to molecular, and therapies providing selective and individualized treatment options. One of the major advantages of light-based diagnosis is its capability for non-invasive and real-time in vivo assessment that is quick and has no harmful side-effects. This translates into a capability for improved and easier diagnosis and monitoring as defined by clinical need. Combinatorial approaches that include both therapy and diagnostics, termed Theranostics, can provide many benefits to patient and clinician alike. Therapeutic uses of various biophotonics sources, especially LED arrays and lasers, span surgical and non-surgical realms in medicine and dentistry. Moreover, the often quoted 10 year lag between ground-breaking laboratory research and clinical practice is mitigated in this particular field by the power of social media, accessible scientific meetings and fora, as well as online learning and training avenues. This special issue is dedicated to highlighting a few of the key advances in biophotonics that hold considerable promise for improving patient care in dentistry. One of the early domains of laser use in dentistry was caries detection and ablation. Current caries assessment techniques include Quantitative fluorescence, Laser-induced fluorescence (LF), transillumination and optical coherence tomography (OCT). In a paper by Wilder-Smith et al. that is included this issue, the clinical efficacy of LF and OCT was compared with current standards of care—visual examination and radiographs—for caries detection. The authors note that, although LF was most effective at detecting surface caries on smooth tooth areas, OCT provided a viable alternative to radiographs at multiple sites, including smooth surfaces, the margins of existing restorations and beneath sealants and restorations. However, the authors note that current swept-source OCT techniques are limited to detecting caries less than 2mm below the tooth surface. Addressing this specifically in another paper included in this issue, Fried et al. utilized polarization-sensitive illumination and cross-correlation analyses which they term cross-polarization optical coherence tomography (CP-OCT). The authors demonstrated in a clinical study that CP-OCT can be used to monitor changes in the internal structure of early active carious lesions on smooth enamel surfaces. They also reported that this technique can be used to assess topical interventions with fluorides to reverse early carious lesions. These innovations clearly hold much promise to current restorative and pediatric dental practice. The very first dental hard tissue laser showed considerable—if somewhat slow—ablation effectiveness in vitro[1]. However, these early devices frequently caused considerable increases in intra-pulpal temperatures, often leading to irreversible pulpal damage. This effect considerably impeded the adoption of lasers to clinical dentistry [2]. Since those early days, the development of a better understanding of laser-tissues interactions and improved optics and photonics technologies have provided avenues to overcoming this challenge. Innovations in precision machining at the nanoscale level, facilitated by extreme peak powers with pulsed beams that minimize collateral thermal damage have provided the basis for the development of safer and more efficient dental hard tissue lasers. Ongoing areas of innovation to improve clinical performance include new wavelengths and shorter pulse durations—potentially extending beyond the existing femtosecond ranges. The search for additional wavelengths has the goal of better achieving targeted clinical effects while avoiding adverse biological responses. This issue includes a paper by Yuichi Izumi et al. that describes one such innovation. It showcases the development of a new dental hard tissue laser operating at 2.76–3.00mmwavelengthfromasolidstate, chromium-doped