Dentinal adhesive with composite restorations: a clinical and microstructural evaluation.

It is generally accepted that the application of dentin-enamel adhesive should involve not only the etched enamel but also the dentinal surface. For this purpose, new bonding agents requiring dentin etching and the combined use of bifunctional groups (Primers) as well as hydrophilic resins have been introduced. This study used scanning electron microscopy to analyze the relationship between dentin and fluid resin of three bonding agents. The results demonstrated that the adhesive monomers easily penetrated the etched dentin, sealing the dentinal tubules and creating a resin dentin interdiffusion zone (hybrid layer). As a result, the microleakage between dentin and resin composite restorations, responsible for postoperative tooth sensitivity, pulpal inflammatory reaction, and secondary decay, is greatly reduced.

In vivo and in vitro analysis of a bonding agent.

Recently many researchers have become interested in the adhesion of composite resin to the dentinal surface. Because it is easier to obtain good composite resin adhesion when a surface is free from smear plug, several chemical agents (acids or linking agents) have been suggested for surface preparation. Nevertheless, the pretreatment of dentin leads to an increase of pulpal outflow, which can interfere with the bonding agent's adhesion. Thus, new-generation dentinal bonding agents appeared on the market. They use a pool of highly absorbent primers to facilitate the scattering of the agent in the dentin substratum under humid conditions. The present study shows the results, obtained with the help of scanning electron microscopy, of resinous penetration into the tubular structures of dentin using a latest-generation bonding system. The in vivo and in vitro tests showed a deep scattering of intermediate fluid resin into tubules, even in the presence of physiologic outflow of dentinal fluids.

[An ultrastructural analysis of dentin treated with chemical agents]. / Analisi ultrastrutturale della dentina trattata con agenti chimici.

Dental last generation bonding systems require the total removal of smear layer and smear plug by chemical solutions. Intermediate fluid resin can penetrate the dentinal tubes obtaining a better anchorage to the dental structures. The department of Operative dentistry of the University of Rome "La Sapienza" has carried research observing by means of the SEM the ultrastructural aspect of smear layer and the effect of dentin treatment with five different chemical agents.

[An ultrastructural analysis of the peritubular dentin and of the tubular lumen in healthy teeth]. / Analisi ultrastrutturale della dentina peritubulare e del lume tubulare di denti santi.

In this study the authors examined some specimens of fractured dentine of embedded healthy teeth, of people aged between 20 and 30. Connecting the scanning electron microscopy to a system of computerised analysis of spectrometry (EDS) allowed the analysis of the qualitative composition of the specimens. Therefore, the authors described the tubular structure of the sound, the peri- and the intertubular dentine, the winding course of the dentinal tubules and in some specimens, the presence of cylindrical structures inside the tubules. The EDS analysis demonstrated that these tubular structures have the same composition as the intertubular dentine. Former studies described hollow cylindrical structures having a similar morphology solely as a response of the odontoblasts to white spots. On the contrary, in this study it was demonstrated that it is possible to find cylindrical structures which are definitely mineralized in sound teeth without caries. However, the presence of such formations is not concomitant with the disappearance of peritubular dentine which is a typical structural modification of the pathological advancement of the carious lesion.