Evaluation of two formulations containing mineral trioxide aggregate on delayed tooth replantation: relevance of RANKL/RANK/OPG system

This study aimed to evaluate the effects of White MTA (WMTA) and MTA Fillapex(A (R)) on root resorption, when used for root canal filling, in a rat model of delayed tooth replantation, with special focus on the RANKL/RANK/OPG system. Maxillary right central incisors of male rats were extracted (total N = 48), and exposed to dry environment for 30 min. The animals were allocated into four groups: (1) WMTA; (2) MTA Fillapex; (3) Calcium hydroxide; (4) Negative control. After periodontal ligament removal, root canals were filled with the corresponding material and replanted. After 10 and 60 days, qualitative and semi-quantitative histological and immunohistochemical analyses were carried out. Analysis of variance (ANOVA) with Tukey's post hoc adjustment was used, at 10 and 60 days, to compare the experimental groups in terms of the inflammatory scores and in terms of the changes in OPG, RANK and RANKL. Both WMTA and MTA Fillapex groups displayed inflammatory and replacement resorption, with the presence of dento-alveolar ankylosis, similarly to that observed for calcium hydroxide, in either 10 or 60 days. Notably, a slight increase of the inflammatory process was observed in both MTA groups. Quantitatively, inflammation score analysis showed a significant difference between the calcium hydroxide and the control group at 10 days. On 60 days, dento-alveolar ankylosis was found significantly increased in the MTA Fillapex, in comparison to the control group (p < 0.05). For immunohistochemical analysis, the expression of both RANK and RANKL was reduced in calcium hydroxide and WMTA groups, from 10 to 60 days of evaluation, an effect that was accompanied by increased OPG immunolabelling. Otherwise, the MTA Fillapex group presented a general increase of RANKL immunopositivity, similarly to that observed in the negative control group. Our data showed that none of tested materials was able to fully prevent the root resorption, although the white MTA cement presented an outcome comparable to that seen for calcium hydroxide. MTA cements might present some advantages when considering no need of frequent changes, although the effects of MTA cements in dental avulsion still require further investigation.