# Hydration Characterization of Two Generations of MTA-Based Root Canal Sealers
## 1 Introduction  
Due to the lack of gutta-percha adhesiveness, root canal sealers are regularly used to achieve three dimensional obturation and fill minute spaces between the gutta-percha cones and canal walls, providing a fluid-tight seal [1]. Different types of sealers have been developed possessing different compositions to meet the criteria of [PERSON] described in 1988 [2]. Since the development of mineral trioxide aggregate (MTA), it has been considered a gold-standard biocompatible material with high numbers of interesting clinical applications in endodontic treatment [3]. Based on the cohesive strength, biological behavior and osteogenic potential of MTA [4, 5], MTA-based root canal sealers were introduced to offer all of these advantages. MTA is mainly composed of tri-calcium silicate (C\({}_{3}\)S), di-calcium silicate (C\({}_{2}\)S), and bismuth oxide [5, 6]. It is characterized by alkaline pH [5] that creates a suitable environment for periapical healing [7].  
The setting time and setting reaction have an impact on the performance of root canal sealers and, in turn, on the quality of root canal obturation. According to [PERSON], the sealers must have ample working time to allow sufficient time for condensation procedures. On the other hand, an extended setting time is an undesirable property when considering the inflammatory reaction and cytotoxic effect of the adjacent periapical tissues [8, 9].  
MTA-Fillapex was first developed by [PERSON](r) (Londrina/Parana/Brazil) in 2010 [10]. It is available in a syringe with an automixed tip. According to the manufacturer, it is composed of 40% MTA (C\({}_{3}\)S, C\({}_{2}\)S, tri-calcium oxide, and tri-calcium aluminate), fumesilica, titanium dioxide, natural resin, salicate resin, and bismuth trioxide. It is characterized by alkaline pH due to the formation of calcium hydroxide as a by-product of its hydration reaction [6]. It provides some biological properties such as antibacterial activity [4,11] and bioactivity [12]. However, the conventional MTA-cement had an extended setting time [5]. According to manufacturer's guidelines, MTA-Fillapex has a setting time of 130 \(\pm\) 10 min [10]. One study showed a prolonged working time, initial setting time \(\approx\) 2.27 \(\pm\) 0.06 h, and final setting time \(\approx\) 4.55 \(\pm\) 0.05 h. However, it remained partially set in a previous study even for one month [11,13]. In this context, manufacturers compete to produce modified generations to improve the physical and chemical properties of MTA-based sealers.  
Recently, a new generation of MTA-based sealer was launched by ITENA Clinical, (Paris, France). The manufacturer claims it has a suitable working time and short setting time \(\approx\) 2 h [14]. There is no further information about its setting characterization other than that given in the manufacturer's reports. The setting characterization of the sealer has an impact on its handling and quality as well as the biological behavior of the final obturation [15].  
The current study aimed to evaluate the setting characterization of the first (MTA-Fillapex) and the recent (MTA-Bioseal) generations compared with epoxy resin (Adseal) sealers. The null hypothesis was that there would be no significant difference between the three root canal sealers.