Light transmittance characteristics and refractive indices of light-activated pit and fissure sealants

Assessment of tissue pathology using optical polarimetry

Optical polarimetry have been extensively used for the non-invasive assessment of biological tissues. However, the knowledge regarding differences in polarimetric signatures of different tissue pathologies is very scattered, confounding the deduction of a global trend of the polarimetric variables for healthy and pathological tissues. The purpose of this study was to bridge this gap. We conducted a rigorous online survey to collect all published studies that report the two most common polarimetric variables (i.e., depolarization and retardance) for any type of tissue pathology. A total of 101 studies describing the polarimetric assessment of tissues were collected, wherein 253 (i.e., n_human = 149, n_animal = 104) different type of tissues were optically characterized. Most tissue samples (172/253) were investigated in ex vivo settings. The data showed 32 different types of tissues pathologies, where the most common pathology was cancer and its subtypes. The skin tissues were the most frequently explored tissues, followed by tissue samples from breast, colon, liver, and cervix. Although differences in polarimetric signatures of different tissue pathologies were summarized from the included studies, generalization of the results was hindered by the presentation of polarimetric data in a non-uniform format. The analyses presented in this study may provide an important reference for future polarimetric studies that conduct optical assessment of tissues at greater depth, particularly in the context of optical biopsy/digital staining.

Isolating individual polarization effects from the Mueller matrix: comparison of two non-decomposition techniques

The prevailing formalisms for isolating individual polarization effects from the experimental Mueller matrix M can be broadly divided into two categories; decomposition of M to derive the individual optical effects and directly associating the individual optical effects to specific elements of M (i.e., non-decomposition techniques). Mueller matrix transformation (MMT) and direct interpretation of Mueller matrix (DIMM) are two popular techniques of the latter category. In this study, these two non-decomposition techniques (i.e., MMT and DIMM) are compared in a detailed quantitative analysis comprising of tissues (n = 53) and phantom (n = 45) samples. In particular, two commonly investigated polarimetric variables (i.e., depolarization and retardance) were calculated from the experimentally measured M using both the non-decomposition (i.e., MMT and DIMM) techniques. The comparison carried out with scatter plots (integrated with the correlation coefficients), violin plots and Bland and Altman plots revealed better agreement of depolarization-related variables (as compared to the retardance) between the two non-decomposition techniques. The comparative analyses presented here would be beneficial for the interpretation of polarimetric variables and optical characterization of turbid media.

Refractive index of biological tissues: Review, measurement techniques, and applications

Refractive index (RI) is a characteristic optical variable that controls the propagation of light in the medium (e.g., biological tissues). Basic research with the aim to investigate the RI of biological tissues is of paramount importance for biomedical optics and associated applications. Herein, we reviewed and summarized the RI data of biological tissues and the associated insights. Different techniques for the measurement of RI of biological tissues are also discussed. Moreover, several examples of the RI applications from basic research, clinics and optics industry are outlined. This study may provide a comprehensive reference for RI data of biological tissues for the biomedical research and beyond.

Irradiance of Different Curing Modes of Common Light Cure Devices: An In Vitro Study

Aim:

The aim of this study was to test the irradiance values of different curing modes of commonly available light cure devices (LCDs).

Materials and Methods:

An in vitro investigation was carried out to compare the irradiance output of 10 brands of LCDs available in Saudi Arabia measured using a digital radiometer. Values were recorded for three time points when applicable (0, 10, and 20s). This technique was repeated five times for each LCD. Normal, high-intensity, and soft-start modes were evaluated for all brands with the features available. Irradiance values between brands were analyzed using one-way analysis of variance followed by Bonferroni method. Changes in irradiance between different time points were analyzed using one sample t test for normal and high-intensity modes and using paired t test for soft-start mode. All comparisons were carried out at 0.05 significance level.

Results:

The highest values were reported for Ortholux Luminous, Elipar DeepCure-S, Elipar DeepCure, and KaVo mini-LED with values above 1000 mW/cm². All LCDs showed values above 600 mW/cm². Three LCDs had high-intensity mode and only one device had soft-start mode. Changes over the different time points were not statistically significant exept for soft-start mode.

Conclusion:

All tested LCDs had irradiance values sufficient for adequate polymerization of resin composite. Only four of these are capable of curing bulk-fill composites.

Efficiency of light curing units in a government dental school

The light intensity of a light-curing unit is a crucial factor that affects the clinical longevity of resin composites. This study aimed to investigate the efficiency of light-curing units in use at a local governmental dental school for curing conventional and bulk-fill resin materials. A total of 166 light-curing units at three locations were examined, and the brand, type, clinic location, diameter of curing tip, tip cleanliness (using a visual score), and the output (in mW/cm² using a digital radiometer) were recorded. Only 23.5% of the units examined had clean tips, with the graduate student clinical area containing the highest percentage of clean tips. Further, tips with poor cleanliness score values were associated with significantly lower output intensities. A small percentage (9.4%) of units was capable of producing intensities higher than 1,200 mW/cm² and lower than 600 mW/cm² (7.6%). The majority of the low intensity units were located in the undergraduate student area, which also contained the highest number of units with intensities between 900 and 1,200 mW/cm². The output of all the units in service was satisfactory for curing conventional resin composites, and most units were capable of curing bulk-fill resin materials.