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. Root canal surgeries performed with a new kind of material could successfully entrap problematic bacteria and prevent tooth abscesses. A team led by Kee-Yeon Kum from the Seoul National University School of Dentistry, South Korea, prepared roots from 60 extracted human premolar teeth. They exposed half of the teeth to Enterococcus faecalis, a bacterium commonly found in infections in root-canal treated teeth, the remaining teeth acting as controls. The roots were then filled with either a phosphate-buffered saline (PBS) solution or OrthoMTA, a newly developed type of mineral trioxide aggregate (MTA) cement composed mainly of tricalcium silicate. After incubation periods ranging from one to 16 weeks, the researchers examined the teeth using scanning electron microscopy. They found that OrthoMTA-filled roots had higher rates of mineralization and could seal or ‘entomb’ the bacteria dentinal tubules.