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Establishing reproducible methodologies for assessment of early enamel lesions using optical coherence tomography (OCT) appears to be challenging. This in vitro study longitudinally evaluated the subsurface enamel lesion progression after 3, 9 and 15 days by cross-sectional scanning using 1310 nm centered swept-source OCT (SS-OCT) under hydrated and dry conditions. The positive difference between the depth-integrated OCT signals at dry and hydrated conditions were calculated and adopted as dehydration parameter (DH). A linear regression was found between DH and the square root of demineralization time (R(2) = 0.99). Significant differences were found in DH between sound and demineralized enamel, and between different periods of demineralization (p < 0.001). Hydration state affects the reflectivity of demineralized porous enamel, and the effect can be potentially used for assessment of early enamel lesion using OCT.

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Purpose Despite the good sealing ability and biocompatibility of mineral trioxide aggregate (MTA), its slow setting, high degradation, and weakness limit its use in surgical endodontics and high stress-bearing areas. This study aimed to develop two new liquids to control these drawbacks. They were prepared from calcium chloride, fumed silica, and hydroxyapatite or calcium phosphate and coded “H” and “P,” respectively. Methods Portland cement, Grey ProRoot® MTA, and white ProRoot MTA were mixed with distilled water (control) or liquid “H” or “P.” The pH, setting time, degradation rate, leachant/precipitate' composition, compressive strength, and morphology were assessed. Results Both liquids maintained MTA's high alkalinity and reduced the setting time by 1-2 orders of magnitude. Both liquids, H in particular, significantly reduced the degradation rate of Grey ProRoot and White ProRoot MTA®. Calcite has been identified as the main phase of the leachant or precipitate formed during the cement's degradation. Calcium hydroxide or hydroxyapatite was also identified with Grey ProRoot MTA mixed with H liquid. These liquids also significantly increased the compressive strength with no statistical differences between them; this was associated with the production of dense, consolidated structures. Conclusions The modified MTA could be used in surgical endodontics and high stress-bearing areas.