Demineralization of resected root-ends with methylene blue dye

Objectives. This study evaluated the ability of methylene blue solutions of different concentration, pH, and time exposure to remove the smear layer from resected root-ends. Study design. Resected root-ends were treated with either 2% methylene blue dye for intervals of 5 to 11 minutes or 1% methylene blue for 7 to 9 minutes and examined with a scanning electron microscope for smear layer removal. Two minute applications of saline solution and 50% citric acid served as controls. Results. All methylene blue solutions were found to be ineffective in removing the smear layer at all time intervals tested. An experimental solution of 1% methylene blue in 50% citric acid was found to predictably remove the smear layer during a 2 minute application and retained all the favorable staining characteristics of the dye. Fifty percent citric acid solutions applied for 3 minutes appeared to overdemineralize the root-end and gave poorer results than 2 minute applications. Conclusions. Smear layer removal was pH dependent. Methylene blue solutions are clinically unsuitable for smear layer removal.