Bacterial entombment by intratubular mineralization following orthograde mineral trioxide aggregate obturation: a scanning electron microscopy study

Abstract

The time domain entombment of bacteria by intratubular mineralization following orthograde canal obturation with mineral trioxide aggregate (MTA) was studied by scanning electron microscopy (SEM). Single-rooted human premolars (n=60) were instrumented to an apical size #50/0.06 using ProFile and treated as follows: Group 1 (n=10) was filled with phosphate buffered saline (PBS); Group 2 (n=10) was incubated with Enterococcus faecalis for 3 weeks, and then filled with PBS; Group 3 (n=20) was obturated orthograde with a paste of OrthoMTA (BioMTA, Seoul, Korea) and PBS; and Group 4 (n=20) was incubated with E. faecalis for 3 weeks and then obturated with OrthoMTA–PBS paste. Following their treatments, the coronal openings were sealed with PBS-soaked cotton and intermediate restorative material (IRM), and the roots were then stored in PBS for 1, 2, 4, 8 or 16 weeks. After each incubation period, the roots were split and their dentin/MTA interfaces examined in both longitudinal and horizontal directions by SEM. There appeared to be an increase in intratubular mineralization over time in the OrthoMTA-filled roots (Groups 3 and 4). Furthermore, there was a gradual entombment of bacteria within the dentinal tubules in the E. faecalis inoculated MTA-filled roots (Group 4). Therefore, the orthograde obturation of root canals with OrthoMTA mixed with PBS may create a favorable environment for bacterial entombment by intratubular mineralization.

Evaluation of the Ca ion release, pH and surface apatite formation of a prototype tricalcium silicate cement

“…The precipitates form via the dissolution of the calcium hydroxide that forms during the initial hydration reaction, which causes increases in pH and the Ca 2+ concentration and enhances the supersaturation of the phosphate-containing fluid with respect to calcium phosphates, and hence, promotes precipitation (Kokubo & Takadama 2006). Calcium phosphate precipitate formation is also known to contribute to the sealing of the material-dentine interface (Sarkar et al 2005, Reyes-Carmona et al 2009) and the occlusion of dentinal tubules (Han & Okiji 2013, Yoo et al 2014. MTA has several drawbacks; for example, it has a long setting time (Torabinejad et al 1995, Dammaschke et al 2005, is difficult to handle and causes discoloration (Camilleri 2014a), and several new calcium silicate-based materials have recently been developed to address these limitations.…”

Evidence of Intratubular Biomineralization in a Root Canal Filled with Calcium Enriched Material over 8 Years

“…Previous in vitro studies reported its use as root canal filling material, showing evidences of intracanal mineralization of root canal dentin at the interface of dentin and obturation material [7,9,10]. However little was known on in vivo data on this issue.…”

“…We speculate that these precipitates, most probably amorphous calcium phosphate, was gradually formed from calcium ions leached from MTA and phosphorous ions in dentinal fluids [12,13]. Such intratubular mineralization could physically entomb microorganism [9,14], and also the depletion of intratubular phosphorus might result in the inhibition of E. faecalis since phosphorus ion is essential to the survival of E. faecalis [15]. Noteworthy the Ca/P ratio at the orifice level was relatively higher than deeper tubules, and decreased along the tubular pathway.…”

“…MTA's sealing effects appear to be due to the formation of hydroxyapatite crystals and the biomineralization of dentinal tubules [1], as reported by in vitro studies [2][3][4][5][6]. However, the long term clinical evidence for the biomineralization in dentin are missing, and its relevance unclear.…”

“…After 2 weeks, the root canal was copiously irrigated with 5.25% NaOCl, then immersed in 17% ethylenediaminetetraacetic acid (EDTA) solution (pH 7.2) for 1min, and finally flushed with 5.25% NaOCl, with all irrigants activated ultrasonically (P5 Newtron1 XS; Satelec, Acteon group, Mėrignac, France). Then, the canal was copiously rinsed with sterile distilled water, dried with sterile paper points and obturated with OrthoMTA (BioMTA, Seoul, Korea) as previously reported [1,7]. The OrthoMTA had been mixed with distilled water by using the OrthoMTA automixer (BioMTA), as recommended by the manufacturer.…”