Abstract
The permeability characteristics of dentin are important factors which influence the transmission of variable stimuli to the pulp. The permeability of dentin is of crucial importance in obtaining good dentin bonding. We have, therefore, investigated to evaluate the potential value of the type I collagen to coat the acid-etched and opened dentinal tubules and to inhibit the permeation of dentinal fluid in vitro study.
The collagen solutions used in this study were prepared by mixing Cellmatrix type I -A®, PBS and 0.08 mM NaOH containing 200 mM HEPES at a final pH 7.4. The bovine dentin surfaces were treated with 10% phosphoric acid for 30 seconds to remove the smear layer and open the dentinal tubules, followed by application of the collagen solution at 37°C for 60 seconds. The microstructures of the dentin surfaces were observed using a scanning electron microscopy (SEM). The permeability of the dentin with or without the collagen application was evaluated under the simulated pulpal pressure of about 25 mmHg. A intrapulpal fluid in this study was reproduced by using 1% bovine serum albumin/PBS, and the value of BSA permeated on the dentin surface was quantified by the Lowly method.
As a result, the following findings were obtained.
1. SEM observation of the dentin surface treated with 10% phosphoric acid followed by the application of 0.3% type I collagen solution at 37°C for 60 seconds showed that the dentinal tubules were covered with a layer of membranous structure. However it was also observed that partially opened dentinal tubules still remained on the treated dentin surface.
2. Under the simulated pulpal pressure of about 25 mmHg, compared with the dentin treated with phosphoric acid only, the permeability of the dentin treated with 10% phosphoric acid followed by collagen solution application was significantly inhibited.
As a result of this basic study, we observed the ability of the collagen application to the dentin surface to seal the dentinal tubules and inhibit the permeation of dentinal fluid.
