Human root dentin microhardness and degradation by triple antibiotic paste and calcium hydroxide.

Purpose: To investigate and compare the effects of the two widely used regenerative endodontics medicaments: Triple antibiotic paste (ciprofloxacine-metronidazole-clindamycin) and calcium hydroxide on the microhardness and degradation of human root dentin.

Methods: Following ethical approval and subject consent to use teeth in this research study, 60 singled-rooted permanent human teeth were randomly divided into six groups:(1) Tri-antibiotic paste with distilled water, or with (2) propylene glycol, (3) calcium hydroxide with distilled water, (4) calcium hydroxide propylene glycol, (5) untreated extracted teeth as negative controls, or (6) teeth instrumented and filled with calcium hydroxide or tri-antibiotic paste as positive controls. The microhardness tests were conducted after 1 and 2 months of exposure to the medicaments using a Vickers microhardness tester. Raman spectroscopy and energy dispersive x-ray spectroscopy were used to evaluate the chemistry and structure of the root dentin.

Results: There were differences in the dentin microhardness following treatment with the medicaments or controls (P< 0.05). The time of root dentin exposure to the medicaments was similar (P> 0.05). The root dentin microhardness was lower in the teeth treated with the triple antibiotic paste or calcium hydroxide when combined with propylene glycol. The root dentin collagen in these treated teeth were also significantly degraded when viewed with Raman spectroscopy and energy dispersive x-ray spectroscopy, whereas the inorganic phase (dentin) remained unaltered. Samples exposed to the antimicrobial agents with water as a vehicle exhibited stronger microhardness and less degradation.

Clinical Significance: These ex vivo results suggest that the triple antibiotic paste and calcium hydroxide should be used with propylene glycol if a fast diffusion is desired or with water to avoid degrading the collagen and weakening the microhardness of the teeth. Clinical trials are needed of new formulations of medicaments with propylene glycol to disinfect teeth for regenerative endodontic procedures, to help strengthen the teeth to prevent the loss of children's permanent immature teeth by fracture following caries or trauma.