Bioactivity of Retrograde Dental Root Filling Materials
Authors: Borș Andreea , Székely Melinda , Molnar-Varlam Cristina , Antoniac Iulian Vasile 
Published: May 2016

The placement of appropriate root-end filling materials in contact with periradicular tissues, with improved adaptation and biological properties is critical for the long-term success of the periapical surgery. The purpose of the present study was to evaluate and compare the bio-properties of four different root canal filling materials with respect to storage media. Two mineral trioxide aggregates: MTA-Angelus (Angelus, Londrina, PR, Brazil) and ProRoot MTA (Dentsply Maillefer, Ballaigues, Switzerland) and two glass ionomer cements: one conventional Ketac Molar (3M ESPE AG, Seefeld, Germany) and a resin reinforced core build-up glass ionomer Vitremer (3M ESPE AG, Seefeld, Germany) were evaluated. Eighty healthy single-rooted human extracted teeth without curvature and with closed apices were included in this experiment. The canals were instrumented with K-files up to size #35. Adequate irrigation was performed during preparation and instrumentation using 2.6% NaOCl. Root canals were obturated with vertically condensed gutta-percha and roots end were apically resected 3mm. The samples were randomly divided in four groups (n=20) and each group was assigned to one of the four tested materials. Three-mm depth preparations were made at root ends using cylindrical diamond burs and constant water spray, and were filled with the tested materials. The roots were then wrapped in wet gauze and placed in an incubator at 37°C for 48 hours to allow complete set of the root-end filling materials. Each group was divided in two subgroups (n=10) and stored in polypropylene sealed containers for 60 days at 37°C. Specimens of the first subgroup were immersed in 5ml of a physiological-like buffered Ca- and Mg-free solution (PBS, pH=7.4) and those of the second subgroup were in 5ml of deionized water (DW, pH 6.8) After 10 minutes of immersion and at the established endpoint times, the specimens were analyzed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Statistical analysis was performed by t-test and one-way ANOVA (p<0.05). The morphology of cement–dentin interface in fresh restorations soaked 10 min in PBS showed the margins of all cements free from porosities or gaps. EDX elemental analyzes on MTA and ProRoot MTA revealed calcium, silica and phosphorous peaks, while on Ketac Molar and Vitremer, aluminum, silica, zinc and fluoride peaks were detected. After 60 days of immersion in PBS calcium-phosphate deposits completely covered the surface, the margin and partially also the peripheral dentin surface of MTA and Pro Root MTA. Glass ionomer cements showed the presence of thick irregular deposits (p<0.05). In deionized water, EDX analyses revealed no deposits forming after 60 days. SEM analysis showed the margins of MTA and ProRoot MTA with significant discontinuities compared with glass ionomer cements (p<0.05). Mineral trioxide aggregate cements are significantly more bioactive compared to conventional or reinforced glass ionomers upon aging in PBS. Glass ionomer cements provide more optimal adaptation to dentinal cavity walls of all cements than MTA cements when used as retrograde fillings.