[Enamel pearls: the ultrastructural aspects and morphogenesis hypotheses]. / Les perles d'émail: aspects ultrastructuraux et hypothèses de morphogenèse.

Five enamel pearls were examined by scanning electron microscope. Some external pearls presented a bare enamel surface, others were covered by a thin layer of cementum. The enamel pearls showed irregular dystrophic enamel surface or a thin layer without structure, rows of irregular Tome's processes pits, enamel caps and focal holes. Some enamel pearls revealed little areas of enamel surface resorption like-resorbing lacunae with, in some cases, areas of tissue repair.

[In vitro and in vivo biocompatibility tests of some endodontic cements]. / Considerazioni su prove di biocompatibilità "in vitro" ed "in vivo" di alcuni cementi endodontici.

The major goal of endodontic therapy has been achieved by condensing filling materials into the root canal. It is not uncommon to find excess material in the periapical tissue. It therefore becomes obligatory to use filling materials that have acceptable biocompatibility. The purpose of this investigation was to obtain a "toxicity profile" of some root canal materials and to compare our observations to study results found in literature. Gutta-percha and five endodontic filling cements were tested in vivo and in vitro. The in vivo biocompatibility involved the placement of the test material in 10 mm teflon tubes with an outer diameter of 1,3 mm which were then implanted subcutaneously into rats. The implants were left in situ for periods of 30 and 90 days. The hemolysis test was used for in vitro evaluations. The histological examination showed cellular responses of different intensity and extent. In some cases severe infiltration of inflammatory cells and areas with necrostis were observed. As a result, the root canal materials evaluated showed slight, moderate, and severe reactions, therefore, a different pattern in tissue response.