Plane dentin surfaces were abraded perpendicular to the radicular axis of sound human molars. They were cleaned to reveal the tubules, and the morphological features of each surface were studied microscopically. For a first series of teeth, the Vickers microhardness of the dentin surfaces was measured and the calcium and phosphorus composition was determined by electron microprobe analysis. For a second series, the microhardness and wettability of the surface by the Scotchbond adhesive were compared. Positive correlations were found between the following parameters: degree of minerality, dentin compactness, hardness, and spreading capability of the adhesive.

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Plane human enamel and dentin surfaces were used for microstructural investigation and shear bond testing. The dental tissue microstructure was characterized through the surface topology, the concentration in mineral elements (determined by electron microprobe analysis), and the Vickers microhardness for the same dental tissue. The etched prismatic enamel presents a surface roughness of about 200% of the apparent area, while the intertubular surface fraction of the dentin is, on the average, equal to 75%. The calcium concentration lies between 23.2 and 37.8% of the enamel total mineral content, and 18.5 and 28.2% of the dentin. The microhardness varies from 205 to 378 Hv for the enamel and from 37 to 98 Hv for the dentin. Also, the shear bond strength to a chemosetting adhesive/composite system varies from 10.4 to 23.9 MPa for the enamel and from 0.0 to 5.0 MPa for the dentin. It is shown that the shear bond strength is strongly correlated to the microhardness through a simple linear equation valid for both enamel and dentin surfaces. In turn, the microhardness is correlated to the calcium concentration through two distinct linear relations. These correlations lead to the intrinsic dependence of the shear bond strength on the calcium concentration of the dental tissue, providing that corrections are applied to the bond strength data in order to take into consideration the effective solid area of the adherend and the polymerization retraction stress. Consequently, it is proposed that the adhesion mechanisms for the both enamel and the dentin are controlled, to a major extent, by the mineral content and the surface topology of the tooth.

The aim of this study was to quantify the sealing ability of four temporary filling materials over 9 days using a new electrochemical technique. Fifty-two extracted human maxillary bicuspids were selected and prepared for the measurements. They were divided into four groups of 12 teeth each, in addition to two positive and two negative controls. After preparation of the endodontic access cavity the sealing ability was registered. After a randomization procedure one group was obturated with IRM, another group with Cavit, a third group with CavitW and the last group with CavitG. The sealability was measured just after obturation (time 0) and after days 1, 2, 3, 4, 7 and 9. The results showed that the IRM group was significantly more watertight than the different Cavit formulations. Throughout the experiment no significant difference was noticed between the Cavit and CavitW groups (P > 0.05). The CavitG group was significantly less watertight throughout the measurements (P < 0.05).