Physicochemical and functional properties of a novel clodronate-containing chelating gel: A comparative in vitro study

Aim: All commercial chelating gels contain EDTA which reacts chemically with sodium hypochlorite (NaOCl). This research aimed to develop a non-EDTA clodronate gel and to measure physicochemical and functional gel properties of the novel and commercial gels.

Methodology: A 1.37 M clodronate gel was made by combining polyethylene glycol (PEG) 400 and tetrasodium clodronate. File-Eze™, Glyde™, Odontoprep®, RC-Prep®, SlickGel™ ES and the clodronate gel were tested in pH, density and viscosity experiments. pH: A pH meter was used at 23°C. Viscosity: A rheometer recorded viscosity at a shear rate of 10/s at 35°C. Free available chlorine (FAC): NaOCl reactivity with the clodronate gel was compared to a 4% NaOCl control by measuring FAC with iodometric titration. Tissue Dissolution: File-Eze, Glyde, RC-Prep and clodronate gel mixtures with 4% NaOCl, PBS (phosphate buffered saline) (negative control) and 4% NaOCl (positive control) were tested. Percentage weight losses of porcine palatal mucosa were recorded over 5 min at 35°C. Smear Layer Removal (SLR): Scanning electron micrography and ImageJ software assessed the SLR ability of File-Eze, Glyde, RC-Prep, clodronate gel, PBS (negative control) and 15% EDTA (positive control) by calculating the area fraction percentage of the image occupied by open dentinal tubules (AF%).

Results: pH: Values ranged from 5.78 ± 0.09 (RC-Prep) to 11.34 ± 0.05 (clodronate gel). Viscosity: Ranges were 6390 ± 290 (File-Eze) to 714 ± 50 mPa.s (Odontoprep). FAC: The clodronate gel differed significantly from 4% NaOCl (p < 0.0001, two-way anova, Šídák's tests), albeit with small absolute differences. Tissue Dissolution: All gel-NaOCl mixtures, except for clodronate gel-NaOCl, differed significantly to 4% NaOCl (p < 0.0001, one-way AVOVA, Tukey's multiple comparisons test). Weight losses were: 4% NaOCl, 30.0 ± 3.7%; clodronate gel-4% NaOCl, 29.2 ± 3.5%; whilst other gel-4% NaOCl mixtures ranged from 2.8 ± 2.0% to -0.6 ± 4.5% and PBS was -0.13 ± 3.3%. SLR Ability: Median AF%s were: 15% EDTA-9.7%; File-Eze-8.7%; clodronate gel-5.8%; Glyde-2.5%; RC-Prep-2.2%; PBS-0.22%. All gels differed to 15% EDTA (p < 0.0001, Kruskal-Wallis, Dunn's tests) except File-Eze.

Conclusions: The gels varied in physical properties, but none of them both dissolved organic tissue in NaOCl mixtures and removed smear layer well. Thus, none of the gels tested possessed all functional properties required of a chelating gel for glide path creation.