A Comparative Study of the Biocompatibility of Three Root-end Filling Materials in Rat Connective Tissue Shahriar Shahi, DDS, MSc, Saeed Rahimi, DDS, MSc, Mehrdad Lotfi, DDS, MSc, Hamid Reza Yavari, DDS, MSc and Ali Reza Gaderian, DDS, MSc Abstract The purpose of this study was to compare the biocom- patibility of amalgam, gray MTA and white MTA in the connective tissue of rats. We used 45 Sprague-Dawley rats in this study. The rats were divided into three groups. Root end filling materials were placed in poly- ethylene tubes and inserted into the rats’ connective tissue through incisions. The rats were sacrificed after 3 days, 1 wk, and 3 wk, respectively. Histologic samples were sectioned in 5-m thicknesses and stained with hematoxylin and eosin. Kruskal-Wallis test was used for statistical analysis. The results showed that after 3 days, white MTA was more biocompatible than gray MTA and amalgam. After 1 week, gray MTA was more biocompatible than white MTA and Amalgam. After 3 wk, there were no significant differences between ex- perimental groups and the control group. (J Endod 2006;32:776 –780) Key Words Biocompatibility, endodontic surgery, MTA, root-end filling material S everal retrospective studies have addressed the outcome of conventional, nonsur- gical root canal therapy, and the success rates reported have ranged between 53 % (1) and 95 % (2). However, even if 90% of all endodontic treatment is successful over time, the reciprocal failure rate is still 10% (3). Therefore, a certain number of failures can be expected, probably because of the persistence of bacteria and their byproducts in the root canal system. Although many endodontic failures can be successfully re- treated by an orthograde approach (4), root-end surgery may be the only alternative to extraction in cases where the orthograde approach is not feasible because of the pres- ence of posts and other permanent restorative materials in the coronal aspect of the root canals (5). The ultimate success of the surgery depends on the regeneration of a functional periodontal attachment apparatus, including cementum overlying the resected root-end surface, periodontal ligament, and alveolar bone (6). This would occur more predict- ably when the root canal that is exposed after root end resection is filled with a material that not only seals the canal to prevent egress of any remaining bacteria or their by-products, but also allows for the formation of a normal periodontium across its exterior surface (5). Amalgam had been the most popular and widely used retrograde filling material since the last century (7). It is easy to manipulate, readily available, well tolerated by soft tissues, radiopaque, and initially provides a tight apical seal (7). However, its disad- vantages are significant, including potential for mercury and other ions release, slow setting, dimensional unstability, eventual leak from corrosion, and staining the overly- ing soft tissues causing a tattoo (8, 9). A gray mineral trioxide aggregate (MTA) was developed at Loma Linda University in 1993 as a root-end filling material and for repair of lateral and furcal perforations (9, 10). Gray MTA powder consists of fine hydrophilic particles. The principle compounds present in this material are tricalcium silicate, tricalcium aluminate, tricalcium oxide, and silicate oxide (7). In addition, small amounts of other mineral oxides exist that are responsible for the chemical and physical properties of this aggregate (7).The biocom- patibility of gray MTA has been reported using cell culture techniques and connective tissue reactions (11–13). Sarkar et al. reported the propensity of MTA to release Ca and its ability to form hydroxyapatite and concluded that the sealing ability, biocompatibility and dentinogenic activity of MTA is attributed to these physicochemical reactions (14). White MTA, a new type of MTA has recently been introduced to the profession and, as a consequence, only limited research has been carried out on the properties of this new material (15–17). It was reported that the behavior of osteoblasts is very different in contact with the surface of white MTA compared with gray MTA (16). The aim of this study was to histopathologically examine the biocompatibility of gray MTA, white MTA and high-copper amalgam by implanting them into the subcutaneous connective tissue of rats. Materials and Methods We used 45 male, 2 to 3 month old Sprague-Dawley rats weighing 250  20 g. All ethical and humane criteria contained in Helsinky declaration, and all recommended points by Institutional Animal Care and Use Committee (IACUC), in care and use of laboratory animals were observed in all the different stages of the project. The following materials were investigated: Group A, tooth colored mineral trioxide aggregate (white From the Department of Endodontics, Tabriz Faculty of Dentistry, Azarbaidjan Shargi, Iran. Address requests for reprints to Dr. Shahriar Shahi, DDS, MSC, Department of Endodontics, Tabriz Faculty of Dentistry, Golgasht Street, Tabriz, Azarbaidjan Shargi 5166614713, Iran. E-mail address: shahriar_shahi@yahoo.com. 0099-2399/$0 - see front matter Copyright © 2006 by the American Association of Endodontists. doi:10.1016/j.joen.2006.01.014 Basic Research—Technology 776 Shahi et al. JOE — Volume 32, Number 8, August 2006