RESUMEN
The resistance to fracture of jacket crowns, fabricated of cast glass-ceramic and five traditional ceramics, was evaluated. Four identical jacket crowns of each type were constructed on absolutely equal dental abutments in epoxy resin, obtained from a primary mandibular molar. An increasing load was then applied to the mesiobuccal cusp of each of the 24 crowns. Although the glass-ceramic proved to have the highest fracture resistance, it was not significantly stronger than three other traditional ceramics; neither did it seem to be suitable for constructing jacket crowns on posterior teeth.
Asunto(s)
Cerámica , Coronas , Porcelana Dental , Análisis del Estrés Dental , Humanos , Ensayo de Materiales , Diente Molar , Falla de Prótesis , Resistencia a la TracciónRESUMEN
To determine the effect of pressure variations on the retention of prosthetic crowns, 36 identical, cast metal crowns were fixed to simulated, epoxy resin crown preparations with zinc oxyphosphate cement. Eighteen specimens were placed in a hyperbaric chamber and subjected to 15 cycles of simulated immersion at 30 m and decompression, as usually carried out by scuba divers. The untreated specimens served as controls. When the force required to dislodge the crowns was measured, the treated crowns were dislodged at about one third the load that was required to dislodge the control group, indicating that a statistically significant decrease in cement strength follows pressure variations.