A study by Torrado, et al published in the Journal of Prosthetic Dentistry evaluated cement-retained, implant-supported metal ceramic crowns versus screw-retained crowns in terms of load at fracture. Four groups of 10 crowns each were evaluated using standardized maxillary premolar metal copings. In addition to cement versus screw retention, location of the screw access was evaluated. In one group, the access hole was in the center of the occlusal surface, and in another group the opening was offset 1 mm from the center of the oc-clusal surface and toward the buccal cusp, with both groups having a bucco-lingual width of 5 mm for the occlusal surface of the re-storation. In the 2 cement-retained groups, the occlusal surface bucco-lingual width of the restoration was 5 mm in one group and 4 mm in the second group. In the 4-mm group, the copings were designed with a smaller occlusal surface width. Measurements of the mean value of load at fracture were compared among the groups. The study found that crowns retained with screws fractured at a significantly lower level of force than cement-retained crowns. There was no difference for the variables of screw access location and width of the occlusal table.
(Source: Dental Abstracts, Vol. 50, No. 1, 2005)
