Continuous Chelation in Endodontics with a Focus on the Novel Chelator Clodronate

Abstract

BackgroundSodium hypochlorite (NaOCl) is essential to endodontic irrigation because it uniquely dissolves organic matter and disinfects. Chelators remove the smear layer. Sequences of NaOCl and the chelator ethylenediaminetetraacetic acid (EDTA) are in common use because alone neither fulfils all the core functions required of an irrigant. In 2005, the concept of continuous chelation was introduced, whereby a chelator is combined with NaOCl for simultaneous antimicrobial and proteolytic actions and with the capacity to remove smear layer. Not only is this simpler compared to standard irrigation, but some authors report improved antimicrobial effectiveness, enhanced dentinal debris removal, and improved bonding of endodontic materials to dentine. Combinations of alkaline EDTA with NaOCl have been investigated, although the only commercial application of this technique employs the chelator etidronate. The major shortcoming of etidronate-NaOCl mixtures is that a chemical reaction occurs between etidronate and NaOCl, causing reduced NaOCl concentrations over time. Given that continuous chelation may hold advantages, finding a chelator more compatible with NaOCl than etidronate would improve the lifespan of continuous chelation mixtures. ObjectivesThe initial objective was to examine the effect of heating to intracanal temperature on known continuous chelation mixtures. A number of chelators were then screened, aiming to identify one, which when combined with NaOCl had better stability with NaOCl than etidronate and was capable of removing smear layer. Once identified, the NaOCl stability of such a mixture was examined at root canal temperature and in refrigerated storage. Subsequent objectives focused on comparing the identified mixture to etidronate-hypochlorite mixtures, standard sequences and NaOCl with respect to organic tissue dissolution, antimicrobial activity and tooth fracture resistance. MethodsFree available chlorine (FAC), pH and temperature were used to assess NaOCl stability in known continuous chelation mixtures at root canal temperature versus room temperature.Iodometric titration was used to determine the FAC. This methodology was then employed to identify a stable chelator-NaOCl solution from several novel chelator mixtures at room Foremost, I would like to thank my supervisors, Professor Laurie Walsh and Honorary Associate Professor Bill Kahler. Without them this PhD thesis would not have been possible.Early on in my PhD, Laurie spent considerable time with me ploughing through the endodontic literature. It was this early foundation which engendered in me the importance of reading the literature. Laurie's door was always open and despite being an incredibly busy and productive person, Laurie addressed concerns as they arose and put ideas on the table.He was also the generous funder of my research. This was a godsend as it ensured that products could be purchased when required. Bill was my moral support when times were tough. He always had time to listen and understand. His knowledge on publication ...