[Importance of intracardiac perfusion fixation technique for in vivo studies in dentistry]. / Importancia de la técnica de perfusión intracardiaca para los estudios in vivo en odontología.

In vivo studies in dentistry require a high level of precision, since they involve the experimentation with a living organism, and further comprehensive histological analysis to validate the initial hypothesis. However, the process to obtained the histological slides to be studied is often wrongly minimized. In order to obtain high quality histological sections, which may be able to react favorably to more complex immunological techniques, it is necessary to preserve or "fix" the tissues of interest in an optimal manner. Intracardiac perfusion fixation has been described as a technique that offers superior results to other tissue fixation methods, allowing not only adequate sample stability, but also a deep cleansing and hardening of the tissues to allow further manipulation. Through a variation of the technique, it is possible to occlude the main arterial supply of the abdominal region to maintain direct perfusion of the fixator in the region of interest, such as the maxillofacial and thoracic region.

Role of osteopontin in the process of pulpal healing following tooth replantation in mice.

Introduction: The role of osteopontin (OPN) following severe injury remains to be elucidated, especially its relationship with type I collagen (encoded by the Col1a1 gene) secretion by newly-differentiated odontoblast-like cells (OBLCs). In this study, we examined the role of OPN in the process of reparative dentin formation with a focus on reinnervation and revascularization after tooth replantation in Opn knockout (KO) and wild-type (WT) mice. Methods: Maxillary first molars of 2- and 3-week-old-Opn KO and WT mice (Opn KO 2W, Opn KO 3W, WT 2W, and WT 3W groups) were replanted, followed by fixation 3-56 days after operation. Following micro-computed tomography analysis, the decalcified samples were processed for immunohistochemistry for Ki67, Nestin, PGP 9.5, and CD31 and in situ hybridization for Col1a1. Results: An intense inflammatory reaction occurred to disrupt pulpal healing in the replanted teeth of the Opn KO 3W group, whereas dental pulp achieved healing in the Opn KO 2W and WT groups. The tertiary dentin in the Opn KO 3W group was significantly decreased in area compared with the Opn KO 2W and WT groups, with a significantly low percentage of Nestin-positive, newly-differentiated OBLCs during postoperative days 7-14. In the Opn KO 3W group, the blood vessels were significantly decreased in area and pulp healing was disturbed with a failure of pulpal revascularization and reinnervation. Conclusions: OPN is necessary for proper reinnervation and revascularization to deposit reparative dentin following severe injury within the dental pulp of erupted teeth with advanced root development.