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The purpose of this study was to evaluate the effect of calcium hydroxide [Ca(OH)2] on dentine composition and root fracture resistance. Root canals of fifty extracted mandibular premolars were prepared and divided into five groups (N = 10). Canals were filled with non‐setting Ca(OH)2 or left empty and were subsequently stored in phosphate buffered saline for 7, 14, 30, or 90 days, respectively. Ca(OH)2 was then washed out, and roots were separated from the crowns and subjected to fracture strength test. Fractured fragments were examined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X‐ray diffraction (XRD). The results showed a significant and progressive reduction in fracture resistance the longer the duration of exposure to Ca(OH)2, and the fracture resistance in teeth exposed for 90 days was significantly lower than in any other group. SEM revealed cracks in the dentine surfaces that had been exposed to Ca(OH)2. FTIR showed a significantly lower mineral to matrix ratio in roots exposed to Ca(OH)2 for 30 and 90 days than seen in roots exposed for a shorter duration. XRD analysis revealed a reduction in dentine crystallinity. It was concluded that Ca(OH)2 significantly reduced the fracture resistance of the roots overtime. Exposure to Ca(OH)2 reduced the mineral to matrix ratio and crystallinity of the dentine.

Background: Overexposure to ultraviolet (UV) radiation is linked to serious adverse health effects that are cumulative in nature and affect children more than adults. UV radiation has also been reported to have serious complications for the eye, particularly in areas with a high UV radiation index. Increasing public awareness about the harmful effects of UV radiation on the eye and promoting awareness about protection against UV radiation may prevent eye disease related to UV radiation damage and help in the improvement of public health in general. This study aims to assess public awareness and knowledge of UV radiation and practices toward UV protection in Jordan, which is a country recognized as having a relatively high UV index throughout the year. Methods: A cross-sectional study was performed using an online questionnaire using Google Forms® to assess people's awareness, knowledge, practices toward eye protection from UV radiation, and the reasons for not wearing UV-protective eyeglasses in Jordan. Sociodemographic information of participants including age, gender, education level, and employment status was also acquired. People’s knowledge on UV protection and harmfulness was measured via rewarding their correctly answered knowledge questions with one mark and zero for incorrectly answered questions based on key answers defined from the literature. Results: A total of 1331 participants (77% females and 23% males) with an average age of 26(±10) years completed the online questionnaire. Participants showed generally high levels of knowledge and awareness about UV radiation and its harmful effects. Nevertheless, participants showed a low level of knowledge about the link between UV radiation and some of the ocular diseases in the questionnaire. Practices toward UV radiation protection where inadequate, with 59% of the respondents reporting that they do not use any protective eyewear from natural UV radiation. The main reported reason for not wearing UV-protective sunglasses was uncertainty in the efficiency of UV protection in sunglasses, as reported by 47% of the participants who do not wear UV-protective sunglasses. Conclusions: The awareness of UV radiation and its harmful effects is high in the studied population. Participant knowledge is also relatively high in relation to nature of solar UV radiation, other synthetic sources of UV radiation, and the most dangerous UV exposure time. However, low participant knowledge was measured on the association between UV radiation with ocular disease and the role of UV-protective eyeglasses. Participant practice toward UV radiation protection was found to be insufficient. Thus, it is important to further increase the knowledge of damaging effects of solar and synthetic UV radiation and emphasize the benefits of eye protection from UV radiation. Eye care practitioners should target youth by different strategies including health campaigns, media, and clinics.