The retention and stability of the cast crowns on the prepared stumps are the most important biomechanical objectives of prosthodontics, determining the success or failure of prosthodontic therapy.
Purpose: This study aims at comparing the retention for three types of cast crowns (metallic, ceramic, composite), fixed with the help of three types of anchorage cements (FOZ, CIS, resin cement) on metal stumps with three different geometries. The assessment of the retention is done by measuring the traction force necessary for the removal of the crown from the stump for each sample.
Material and method: 27 samples were tested by applying an increasingly growing traction force until de crowns detach from the stumps. The maximum traction force for each type of crown, cement and stump was registered with the help of an original testing and measuring device conceived and manufactured for these very purposes. Findings: the highest values for the traction forces and implicitly the best retention was obtained for the samples cemented on higher stumps, with a larger diameter, regardless of the type of crown. Also, the additional retention grooves proved their utility for the improvement of these properties, in comparison with the samples fixed on stumps having the same dimensions, but without grooves. From the perspective of anchorage cements, the worst results are invariably registered by the FOZ, and the best retention is obtained by the resin cement; CIF has intermediate, but sufficiently good retention qualities, being positioned between the FOZ and the resin cement, and can thus be recommended, together with the latter, for the anchorage of all types of dentures belonging to the cast crown type.
Conclusions: The geometry of the stump and the type of anchorage cement used for the cementing of the samples are the essential factors that influence retention in a decisive manner, whereas the biomaterial used for manufacturing the cast crown is less important from this perspective.