## 1 Introduction  
During endodontic treatment, as a result of the complex anatomy of the root canal system [1], procedural mistakes, such as perforation of the pulp chamber walls in coronal and intraradicular areas, can often occur [2, 3]. With the interruption of the continuity of the dentine walls and the damage to cement tissue, contact is made with the periodontium. Frequently, the therapeutic outcome of these complications is unsuccessful and leads to the extraction of the tooth [4, 5]. Therapeutic success depends on multiple factors: the localization of the damage, the size of the damage, the time elapsed since the occurrence of the perforation and the properties of the repairing material [6, 7]. The recommendation is to close the defect as soon as possible to prevent bacterial contamination and the extrusion of infected dentin during treatment or filling material during retreatment [8, 9]. Materials that are used for this purpose should provide firm sealing, lowering the probability of local inflammation, and also should promote perriadicular tissue regeneration. Thanks to its positive properties such as its biocompatibility, bioactivity and the ability to achieve a good marginal seal in a moist environment, mineral trioxide aggregate (MTA) is one of the most frequently used materials for perforation repairment [10]. By mixing components of MTA, the result is a material of sandy consistency, difficult to manipulate, which has a long setting time and the potential for tooth discoloration [11]. The advancement in material properties in order to achieve higher clinical success has brought new formulations to the market. One of them, a material from a group of calcium silicate-based cements, is Biodentine (Septodont, Saint-Maur-des-Fosses, France). The main elements of this powder are tricalcium silicate, zirconium oxide and calcium carbonate. The liquid portion is a mixture of water, calcium chloride (setting accelerator) and a hydrosoluble polymer. The advancement in the basic components has brought a faster setting time with a low water to powder ratio [12], higher compression and flexural strength of the material [13] and extraordinary bioactivity [14]. Materials based on calcium silicate, which are a combination of powder and a liquid, such as MTA and Biodentine, belong to the hydraulic type of cement; materials that set by a hydration reaction [15]. Premixed calcium silicate-based cements supplied in a syringe in the form of a paste are also available. These cements need water from their surroundings for the process of hydration, because they are not mixed with water [16]. These premixed cements have a simplified application. One such cement is the radiopaque material based on calcium aluminosilicate, Well-Root PT (Vericom, Chuncheon-si, Korea). Studies have shown that this material possesses high antibacterial activity, forms phosphate crystals in phosphate-buffered saline (PBS) and has a solubility comparable to MTA and Biodentine [17]. There are no available studies in the literature on other physical or chemical properties of this cement, which would contribute to better application of this material in dentistry. Materials placed in the defect zone are exposed to environmental influences (tissue fluid, blood and products of bacterial metabolism) and the effect of canal irrigants during endodontic treatment. The unfavorable effects of these factors cause the inability of the material to adequately set, the change in material properties (microhardness and bond strength) [18; 19; 20] and changes in the surface chemical structure [21]. Good marginal adaptation [22] and the ability to withstand the dislodging forces, which lead to marginal gap formation [23] and bacterial leakage [24], are necessary properties of materials for perforation repair. Different degrees of dimensional changes lead to formation of gaps and voids of different volume [25]. Changes in material dimensions have been measured in previous studies using a linear variable transducer [26] and scanning electron microscopy (SEM) [27].