The power of light – From dental materials processing to diagnostics and therapeutics

Harnessing the power of light and its photonic energy is a powerful tool in biomedical applications. Its use ranges from biomaterials processing and fabrication of polymers to diagnostics and therapeutics. Dental light curable materials have evolved over several decades and now offer very fast (≤ 10 s) and reliable polymerization through depth (4–6 mm thick). This has been achieved by developments on two fronts: (1) chemistries with more efficient light absorption characteristics (camphorquinone [CQ], ~30 L mol-1 cm1[ʎmax 470 nm]; monoacylphosphine oxides [MAPO], ~800 L mol-1 cm-1 [ʎmax 385 nm]; bisacylphosphine oxide [BAPO], ~1,000 L mol-1 cm-1 [ʎmax 385 nm]) as well mechanistically efficient and prolonged radical generation processes during and after light irradiation, and; (2) introducing light curing technologies (light emitting diodes [LEDs] and less common lasers) with higher powers (≤ 2 W), better spectral range using multiple diodes (short: 390–405 nm; intermediate: 410–450 nm; and long: 450–480 nm), and better spatial power distribution (i.e. homogenous irradiance). However, adequate cure of materials falls short for several reasons, including improper selection of materials and lights, limitations in the chemistry of the materials, and limitations in delivering light through depth. Photonic energy has further applications in dentistry which include transillumination for diagnostics, and therapeutic applications that include photodynamic therapy, photobiomodulation, and photodisinfection. Light interactions with materials and biological tis-sues are complex and it is important to understand the advantages and limitations of these interactions for successful treatment outcomes. This article highlights the advent of photonic technologies in dentistry, its applications, the advantages and limitations, and possible future developments

Photographic investigation of reflected shock phenomena from decigram explosive charges

An investigation of the primary shock front and Mach Y-stem systems was conducted utilizing decigram explosive charges. Distance and arrival time data of the primary shock front was correlated with that of high yield explosions. A good correlation would indicate the feasibility of conducting laboratory scale tests to obtain information on high yield explosions without the expenditure of time and money involved in large scale field tests. The shock front system was also investigated at the time of first formation of the Mach Y-stem. The critical angle of incidence of the primary shock front for the formation of the Y-stem was compared to the theoretical value. Theoretical calculations of the yield of the explosion was also compared to the actual yield. Basic data were obtained from the explosions by photographing the shadow of the shock front system utilizing a Polaroid camera, a microflash unit and a time delay generator. Correlation of the overpressure was excellent for small to moderate distances from the point of explosion, as was the yield comparison. The critical angle of incidence comparison indicated a marked difference between experimental end theoretical values.http://www.archive.org/details/photographicinve00luskLieutenant, United States NavyLieutenant, United States NavyApproved for public release; distribution is unlimited