Effect of Implant Abutment Modification on Excess Cement Extrusion at the Crown-Abutment Margin Using two Types of Cements

Abstract

Success or failure of cement retained implant restorations depend on many factors. Marginal discrepancies and extruded cement at restoration/abutment interface are among these risk factors. Multiple trials and techniques were suggested by many authors to minimize these complications and to achieve optimum results. One of these techniques is modifying implant abutments to minimize the amount of extruded cement and provide better marginal adaptation. This study was done to evaluate the effect of implant abutment modifications and change in type of cement on amount of extruded cement and marginal adaptation at abutment/restoration interface. Thirty anatomic implant abutments with same diameter (4.5mm) were fixed to their corresponding implant analogs and fixed in acrylic blocks of equal dimensions. Thirty standardized polymethylmethacrylates temporary crowns resembling the anatomy of upper first premolar with standard shape,weight and cement gap of30μm were fabricated using CAD/CAM system. Specimens were divided into 3 groups according to types of modifications of abutments. In first group the screw access opening was completely closed while second group hadthe access opening was left open and third group with open access opening and two 1.5mm vent holes 3mm below occlusal top 180 degree apart. The groups were further subdivided into 2 subgroups according to type of cement: temporary and permanent resin cement.The weight of excess cement was calculated for all specimens. Vertical marginal adaptation of all crowns was evaluated before cementation using digital microscope.