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OBJECTIVE: The objective of this study was to compare staining effect of various beverages on and surface nano-hardness of a resin coated and a non-coated fluoride releasing tooth-coloured restorative material. MATERIALS AND METHODS: Two restorative materials, Equia Forte Fil (coated with Equia Forte Coat) and Cention N (non-coated), were evaluated in this study. Fifty samples (n = 50) were prepared from each restorative material. Ten samples of each material were randomly placed in Phosphate Buffer Saline (PBS) solution, Tea, Coffee and Coke solutions. Spectrophotometer readings were recorded after 24 hours of sample preparation followed by 7th, 14th, 21st and 28th day. Colour difference (ΔE) for each sample was calculated at the specified time intervals. The remaining ten samples of each restorative material were subjected to nano-hardness testing. Nano-hardness values at 1st day and 28th day were noted. Colour difference and nano-hardness values were statistically analysed. RESULTS: By the 28th day, all samples from the solutions were stained. Equia Forte Fil coated with Equia Forte Coat samples showed better resistant to staining solutions than Cention N samples. Surface nano-hardness of both the materials increased from the 1st day to 28th day and were comparable. CONCLUSION: Over a period of time, changes in colour stability and nano-hardness, are inevitable. Cention N showed more potential to undergo surface discolouration than Equia Forte Fil. Both materials exhibited increased nano-hardness over a period of time. Cention N exhibited higher surface nano-hardness when compared to Equia Forte, by the 28th day. CLINICAL SIGNIFICANCE: Resin coated, high viscous and fluoride releasing glass ionomers can delay the staining effect by various beverages and exhibit better initial surface nano-hardness when compared to a non-coated alkasite based, fluoride releasing restoration.

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AIM: The aim of the study is to compare the maximum stress distribution on the rotary retreatment instruments within the root canal at cervical, middle, and the apical one-third during retreatment of gutta-percha. MATERIALS AND METHODS: A human mandibular premolar was scanned, and three-dimensional geometry of the root was reconstructed using finite element analysis (FEA) software package (ANSYS). The basic model was kept unchanged; tooth models were created using the same dimensions and divided into two groups as follows: Group I: ProTaper Universal retreatment system and group II: Mtwo rotary retreatment system. The stress distribution on the surface and within the retreatment files was analyzed numerically in the FEA package (ANSYS). RESULTS: The FEA analysis revealed that the retreatment instruments received the greatest stress in the cervical third, followed by the apical third and the middle third. The stress generated on the ProTaper Universal retreatment system was less when compared with the Mtwo retreatment files. CONCLUSION: The study concludes that the retreatment instruments undergo higher stress in the cervical third region, and further in vivo and in vitro studies are necessary to evaluate the relationship between instrument designs, stress distribution, residual stresses after use, and the torsional fracture of the retreatment instrument. CLINICAL SIGNIFICANCE: The stress developed on the rotary retreatment instruments during retrieval of gutta-percha makes the instrument to get separated. There is no instrument system, i.e., suitable for all clinical situations and it is important to understand how the structural characteristics could influence the magnitude of stresses on the instrument to prevent its fracture in use.

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INTRODUCTION: The main disadvantages of mineral trioxide aggregate (MTA) are its prolonged setting time and the difficulty in retrieving it from the root canal. Because MTA is alkaline in nature, it might interact with acids or chemicals and could disintegrate. The aim of this study was to assess the effect of various chemicals on dissolution of white MTA (WMTA). METHODS: Stainless steel molds were prepared and filled with WMTA that was exposed to carbonic acid, 2% chlorhexidine gluconate solution, 17% ethylenediaminetetraacetic acid (EDTA) solution, and saline on days 1 and 21. The surface hardness was measured before and after 5-, 10-, 15-, and 20-minute intervals after exposure to chemicals. The samples were probed with a #16 endodontic explorer after 20 minutes of chemical exposure and hardness testing. RESULTS: Both qualitative and quantitative analysis showed that carbonic acid was effective in significantly reducing the surface hardness of set WMTA on both days 1 and 21; 2% chlorhexidine gluconate reduced the surface hardness of set WMTA significantly on day 1 only. CONCLUSIONS: Carbonic acid can be effectively used as an adjunct to dissolve set WMTA even after 21 days, whereas 2% chlorhexidine gluconate showed significant surface dissolution only within 24 hours of WMTA placement. Thus, usage of chlorhexidine gluconate as a root canal irrigant in which WMTA is used during endodontic procedure should be avoided for 24 hours. Solutions with EDTA have no effect on surface hardness of WMTA.

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