Optimizing the Clinical Protocol – Universal Adhesives and a New CAD/CAM Composite

Objectives: Surface modification of CAD/CAM composites is an important factor to achieve reliable results in adhesive cementation. During try-in, saliva contamination often cannot be avoided. This study examined the influence of surface roughness on bonding performance by testing shear bond strength ("SBS"). Furthermore, the influence of saliva contamination and its removal by water-spray on SBS was investigated.
Methods: SBS was tested in accordance with ISO 29022. Tetric CAD samples were ground using P120, P400, P1000 or P4000 SiC paper or sandblasted ( 1.5bar; corundum , 50 μm), cleaned with compressed air and rinsed with ethanol. Surface roughness was analyzed with a white-light interferometer (FRT Microprof).

SBS specimen were prepared by applying Adhese Universal (Ivoclar Vivadent) under agitation for 20s, thinning the adhesive layer to immobility with compressed air (4bar), inserting the specimen into the sample jig and applying Variolink Esthetic DC (Ivoclar Vivadent) through the jig mould before light curing (2x10s, 1200mW/cm²,Bluephase Style, Ivoclar Vivadent). Shear bond strength (n=5) was measured after aging (24h , 37°C, water) using a universal test machine (Zwick-Roell Z010) at crosshead speed of 1mm/s

Sandblasted Tetric CAD samples were contaminated using human saliva (60s contact time), rinsed with water-spray prior to bonding as described above.
Results: Highest SBS values were obtained with surface roughness of >0.8 μm, as achieved by sandblasting, and grinding with P400 or P120 (30–35MPa). Other treatments gave significantly lower SBS (14-20MPa). As shown by SBS, saliva contamination can be removed by water spray.
Conclusions: High bond strength to sandblasted Tetric CAD was obtained using Adhese Universal and Variolink Esthetic DC. Saliva contamination was effectively removed by cleaning with water spray prior to adhesive application.