EFFECT ON THE ADHESION OF ROOT CANAL SEALERS
Adhesion is defined as a process in which two surfaces of different molecular compositions are bonded by chemical, physical or mechanical attraction forces.[59] Mechanical adhesion occurs by entrapment of a material into another body, within the natural or artificial cavities. Chemical adhesion may result from primary valence forces, such as covalent and metallic bonds. Physical adhesion, in turn, relies on secondary valence forces, such as Van der Walls forces, London dispersion forces and hydrogen bonds.[60] For adhesion to occur, it is necessary that the materials to be adhered are sufficiently close to each other. Therefore, a primary condition is the wet ability of the liquid in a solid material,[61] which will provide the required proximity between the materials, facilitating molecular attraction and promoting adhesion.[59]
Adhesion of an endodontic sealer is defined as its capacity to adhere to the root canal walls and promote the union of Gutta-percha cones to each other and to the dentin.[62,63] Some variables may interfere with the outcome and understanding of sealer adhesion to root canal walls, namely the employed methodology, treatment of dentin surface and type of material.
Several resin-based sealer materials have been developed in an attempt to minimize leakage by improving the effectiveness of the seal between the filling material and the root canal walls.[64,65] Different monomers were used in the development of resin-based sealers. AH Plus (De Trey, Konstanz, Germany) is a two-component sealer based on an epoxy resin; it is used in combination with gutta-percha points. Epiphany SE self-etch (Pentron Clinical Technologies, Wallingford, USA) is a dual-curable self-etching methacrylate resin sealer that is used in association with Resilon points (Resilon Research LLC, Madison, USA), a thermoplastic synthetic polyester polymer-based material that replaces Gutta-percha. A related advantage of the Epiphany system could be its ability to seal the canal, creating a monoblock between the sealer and point materials.[66,67,68] Nevertheless, chemical irrigants used during the root canal preparation may alter the chemical composition of the dentin surface as well as the interaction between the dentin and resin-based sealer. In another study, Nunes et al.[69] showed that treating dentine with a combination of 1% NaOCl and 17% EDTA produced stronger adhesion of AH-Plus sealer compared to 1% NaOCl alone.
Go to:
BIOCOMPATIBILITY
Nygaard-Ostby[70] assessed the effect of 15% EDTA on the human pulpal and periapical tissues in teeth with vital and necrotic pulps. Findings revealed that even though EDTA was forced through the apical foramen into the periapical tissues, no periapical tissue damage could be detected after 14 months. Furthermore, he showed that placement of EDTA for 28 days after pulpotomy produced no pulpal tissue necrosis. Patterson[28] assessed the effect of intramuscular injection of EDTA and EDTAC and found that EDTAC caused much greater tissue irritation than EDTA. Lindemann et al.[71] showed that EDTA was not capable of destroying collagen.
In an investigation of the tissue reaction in rats after intramuscular implantation and injection of EDTA and EDTAC, Patterson[28] showed that 15% EDTAC caused much greater tissue irritation after implantation and after injection than 10% EDTA. No periapical tissue irritation or damage of any kind occurred in 200 clinical cases where EDTA was used as an irrigant.
Segura et al.[72] showed that extrusion of even a low concentration of EDTA solution through the apical constriction resulted not only in an irreversible decalcification of periapical bone but can also have consequences for neuroimmunological regulatory mechanisms. Segura et al.[73] investigated the effect of EDTA and EGTA on the binding of vasoactive intestinal peptides (VIPs) to macrophages. VIPs act not only as vasoactive substances, but also play an important role as neuropeptides in the communication between nerves and immune cells in the pulp and periapical tissue by modifying the macrophage function. EDTA inhibits vasoactive interstitial peptides binding to macrophages even in lower concentrations than those used in endodontics (10%). EDTA can prevent the adhesion of macrophages to substrate; this is time and concentration dependent.[73] EDTA concentrations measurable in the periapical tissues are capable of reducing binding by 50%.
However, changes in macrophage activity can cause the inflammatory reaction to be more easily initiated, but reduced capacity of phagocytosis can result. Furthermore, it has been discovered that EDTA improves plasma extravasation and mediator action. In an investigation of the effects of dental etchants and chelators on nerve compound action potentials,[74] RC-Prep and File-EZE were shown to reduce the compound action potentials after an application time of 160 min by 61% and 62%, respectively.
Go to: