Evaluation of sealing ability of mineral trioxide aggregate (MTA) as a canal filling material using micro-computed tomography

Abstract

1. ObjectivesMineral trioxide aggregate (MTA) has been widely used in perforation repair, retrofilling, pulp capping and apexification. Recently, MTA has also been used as an orthograde canal filling material. However, only small number of studies have investigated the sealing ability of MTA as an orthograde canal-filling material. Therefore, the aims of this study were as follows: (1) evaluate the sealing ability of MTA and gutta-percha (GP) in 5mm apical canals, (2) separately compare the sealing abilities of these materials in mesial and distal canals and (3) investigate the differences in the sealing ability between mesial canal and distal canals.2. Materials and MethodsTwenty-two extracted sound human mandibular molars were collected. The root lengths were adjusted to 12 mm after cutting the crowns of the teeth. The canals were instrumented with the ProFile® system (Dentsply Maillefer, Ballaigues, Switzerland) to a master apical size of #35/06 in a crown down manner. Next, the teeth without a canal filling (n = 2) were used as negative controls to determine the range of density for micro-computed tomography (micro-CT) analysis, and the other teeth were randomly assigned to two groups (n = 10) according to the obturation material. In the MTA group, the prepared canals were obturated with ProRoot® MTA (Dentsply Maillefer, Ballaigues, Switzerland) using a specialized MTA delivery gun, the Micro-Apical Placement (MAP) System (Dentsply, Tulsa Dental Specialties, Tulsa, OK), Obtura S-Kondensers (Obtura Spartan, Earth City, MO, USA), and absorbent paper points (Meta Dental Co., Cheongju, Korea). In the gutta-percha (GP) group, the prepared canals were obturated with gutta percha (Diadent, Seoul, Korea) and AH Plus® sealer (Dentsply DeTrey, Konstanz, Germany) using a continuous wave vertical compaction technique. All canal filling procedures were performed under a dental microscope (OPMI PICO; Carl Zeiss, Gottingen, Germany) at 10× magnification. Micro-computed tomography (Skyscan 1076, SkyScan, Kontich, Belgium) was used to scan the teeth. Then, NRecon (NRecon v1.6.3.2; Skyscan) and CT-An (SkyScan) were used for the reconstruction and measurement of the volume of the filling materials (VM) and the gap between the filling material and the tooth structure (VG). The percentage volume of the gap (VG%) was calculated as VG / (VM+VG) * 100. Finally, CT-Vol (Skyscan) was used for the three-dimensional (3D) volumetric visualization.The Mann–Whitney test was used to determine the statistical significance of the following differences: 1) the percentage volume of the gap (VG%) of the MTA and GP groups, 2) the VG% of the MTA and GP groups within the mesial canal groups, and 3) the VG% of the MTA and GP groups within the distal canal groups. Additionally, a Wilcoxon signed rank tests were performed to analyze the differences between the following: 1) the VG% of the mesial and distal canal groups, 2) the VG% of the mesial and distal groups within the MTA groups, and 3) the VG% of the mesial and distal canal groups within the GP groups.