Bond strength between framework materials and gingiva colored materials of implant supported hybrid prosthesis

Full mouth reconstruction of an edentulous patient with osseointegrated implants is a well-accepted treatment in dentistry. Treatment options for the edentulous patient mainly depend on the residual bone quality and bone volume. The treatment can be a challenge when vertical and horizontal tissue resorption limits the desired implant position and prosthesis type. Although some of the lost tissue may be reestablished, challenges still exist. To reestablish function, esthetics, and gingival architecture, different material combinations have been used including metal alloy-acrylic, metal alloy-composite, metal alloy-ceramic, zirconia-composite and zirconia-ceramic. Biological and technical complications frequently occur with full-arch implant-supported fixed prosthesis. Especially, the lack of passive fit between implant and abutment, fatigue load and stress were the most common prosthesis-related technical complications reported with implant-supported complete dental prostheses. The aim of this in-vitro study was to compare the shear bond-strength between two different gingiva-colored materials bonded to Co-Cr alloy and zirconia framework materials. Laser sintered Co-Cr alloy (EOS Co-Cr SP-2, EOS) and pre-sintered zirconia (IPS e.max ZirCAD, Ivoclar) discs with dimensions of 25 mm×3 mm were prepared. SiC papers were used for wet-grinding. Specimens were subjected to AlO2 sandblasting and treated with ultrasonic-cleaning using 90% alcohol, kept in room-temperature distilled-water. Specimens in both groups were pre-treated using primer (Clearfil Ceramic Primer, Kuraray) and resin cement (Panavia Fluora Cement, Kuraray). Opaque (Ceramage Pre-Opaque, Kuraray) was applied only on Co-Cr specimens. Gingiva-colored composite material (Gradia Gum Shades, GC) was applied on half of the specimens while pink porcelain (IPS e.max Ceram, Ivoclar) was applied on the rest in both groups. Shear bond-strength was measured in a universal testing machine with a crosshead speed of 1mm/min. SEM and EDS devices were used to evaluate the fracture surface and elemental content of the prepared specimens. Both framework and gingiva materials significantly affected the bond-strength. The mean (±SD) bond-strength of Co-Cr groups (10,09±5,25 MPa) was significantly higher than zirconia groups (7,91±3,53 MPa). The mean (±SD) bond-strength of porcelain specimens (12,09±4,20 MPa) was significantly higher than composite specimens (5,80±2,04 MPa). A statistically significant difference was also found between all subgroups. Metal-porcelain group (14,11±3,83 MPa) showed the highest bond-strength value, followed by zirconia-porcelain (9,98±3,53 MPa), zirconia-composite (5,95±2,19 MPa) and metal-composite (5,65±1,92 MPa) groups. Results gained from fracture surface and elemental analysis results were in accordance with the bond strength results. Selection of framework and gingiva materials when constructing implant-supported hybrid restorations is critical since both factors affect the bond-strength.