[Fracture resistance of Procera Allceram depending on the framework design--an in vitro study]

Procera AllCeram is one of the all-ceramic systems with an aluminium-oxide core employing CAD/CAM technology. The aim of the current study was to investigate the fracture resistance of Procera AllCeram full-ceramic crowns with a reduced core design compared to the conventional method. In addition, a possible influence of the preparation form (molars or premolars) and the cementation material (glas-ionomer or composite) was analyzed. For both preparation forms, 30 ceramic cores with reduced margins (collarless cores, test) and 30 cores with extended cores (control) were veneered with porcelain in a standardized procedure (total 120 crowns). For the test group, Procera-AllCeram-margin ceramic material was used for the porcelain collar. 40 crowns each were cemented on stainless steel dies with either Ketac-Cem Aplicap or Panavia F. The additional 40 crowns were set on polyurethane dies without cementation and occlusally loaded until fracture occurred. Among the molar crowns, no differences were observed in fracture resistance neither for the different core designs (test or control) nor for the cementation materials. For the premolar form, fusing of a porcelain margin was associated with a reduction in fracture resistance, while the use of composite cement was accompanied with an increase. The present in vitro results indicate that for Procera AllCeram crowns with a highly undulating preparation margin, a conventional core design combined with adhesive cementation is preferable, especially in the posterior region due to higher chewing forces; this assumption needs to be proven in clinical studies.