ABSTRACT
Background: The removable partial denture (RPD) continues to be an essential prosthetic consideration especially when edentulous ridges posterior to a patient's remaining teeth are to be restored. Precision attachments are used as extra-coronal retainers which are characterized by considerable retention improvement. In the current study, we aim to assess strains develop in supporting structures of two study groups resembling Kennedy class I partially edentulous cases which are rehabilitated with Co-Cr cast metal and CAD/CAM milled zirconia successively.
Objective: To evaluate the effect of two different extra-coronal attachments, (Co-Cr cast metal and CAD/CAM milled zirconia) on stresses induced in supporting structure in Kennedy class I cases.
Materials and Methods: This in vitro study was conducted on partially edentulous Kennedy class I cases. Two materials used in the construction of extra-coronal attachment retaining removable partial dentures were investigated; cast Co-Cr and CAD/CAM milled zirconia. The stresses induced were evaluated using the electric strain gauge analysis technique.
Results: evaluating the strains developed in both groups showed a statistically significant increase in stresses induced in the group rehabilitated with Co-Cr cast metal attachments compared to the group of CAD/CAM milled zirconia on the loaded side and a statistically insignificant difference in the unloaded side.
Conclusion: CAD/CAM milled zirconia and Co-Cr cast metal attachments showed a different distribution of forces as the zirconia attachment transmits fewer stresses to the loaded and unloaded sides compared to the metal attachment.
Keywords: Removable partial denture, Extra-coronal attachments, CAD/CAM zirconia