Relyx unicem

The endocrowns in each preparation design group (n = 30) were assigned into three subgroups (n = 10) based on the zirconia surface treatment applied as follows;
Subgroup A: The intaglio surfaces of the endocrowns underwent air‐porn particle abrasion for 15 s with 50 μm Al₂O₃ particles from a 10 mm distance and a pressure of 0.3 MPa.
Subgroup Co: Specimen surfaces were air‐born particles abraded using silica‐coated Al₂O₃ (CoJet™ Sand; 3 M™) with a particle size of 30 μm under 2.8‐bar pressure for 15 s from a distance of 10 mm using the CoJet™ device (CoJet™ Prep; 3 M™).
Subgroup Z: specimens were etched for 30 min at 30°C using Zircos‐E® Etching Solution (M & C Dental).
All zirconia endocrowns were cleaned in an ultrasonic bath and gently dried with oil‐free air. The prepared teeth were cleaned for 15 s using a rubber cap and fluoride‐free pumice and washed with water. The endocrowns were then cemented with self‐adhesive resin cement (RelyX™ Unicem, 3 M™). The restorations were held in a specially designed device under a 4.9 N axially directed load for 5 min. Excess cement was removed, and light curing was performed for 20 s on each side of the endocrown restorations. The cemented endocrowns were placed in distilled water and stored in an incubator at 37°C for 24 h, before undergoing thermocycling for 5000 cycles with 5–55°C temperature fluctuations, and a dwell time of 15 s.

To assemble the titanium insert and zirconia abutment, the inner surface of the zirconia abutment was treated with silica-modified aluminum oxide sandblasting (Rocatec; 3M ESPE) to enhance the bonding strength with the titanium insert, and then a ceramic primer (Monobond Plus; Ivoclar Vivadent, Schaan, Liechtenstein) was applied. The zirconia abutment was bonded with the titanium insert using dual-cure self-adhesive resin cement (RelyX Unicem, 3M ESPE, St. Paul, MN, USA) according to the manufacturer’s instructions. Remaining adhesive was removed under a microscope at 10X magnification.
The abutment was connected to the implant through a titanium abutment screw using a torque wrench (Dentium, Seoul, Korea) with 30 Ncm of tightening torque, as recommended by the manufacturer. Implant–abutment joint stability was ensured by retightening the screw to establish sufficient preloading [6 (link), 17 ].
Then, the abutment was stored in distilled water at 37°C for 24 hours to eliminate the effect of volume change due to adhesive hydration. Thermocycling (Thermal Cyclic Tester, Thermocycling: R&B, Inc.) was performed at 5–55°C in a water bath at intervals of 15 seconds and 10 seconds to simulate five years of exposure to moist oral conditions [18 ].

Five different dual cure resin cements were used for cementing rods to bovine dentin; Multilink Automix (Ivoclar Vivadent), Variolink Esthetic (Ivoclar Vivadent), Panavia F2.0 (Kuraray Noritake Dental), Duo-Link (Bisco) RelyX Unicem (3 M ESPE) (Table 1).
Cementation was performed according to producers’ manual and primer was applied when recommended (Table 1).
Ten rods from each of the three groups; KHF₂ etched zirconia, air borne particle abraded zirconia and HF etched lithium disilicate, were cemented by each cement.
Dentine was cleaned using pumice powder dispensed in water prior to cementation.
After placing the rods onto dentin, a standardized 882 g seating load was applied by a cementation jig. Excess cement was removed using quick stick micro-brush before light curing 20 s each from 4 directions.
All specimens were kept dry at room temperature for 15 min following cementation and thereafter immersed in 37°C distilled water for 24 h.
Specimens were sandblasted using Al₂O₃ to remove cement remnant outside the rods and evaluated by light microscopy. Test units were thermocycled 5000 cycles in 5 °C and 55 °C water baths.

The root-canal treated teeth were randomly assigned into six groups of 10 teeth each (Table-I).
In all groups, a size # 3 tapered fiber post of 15mm length and 1.6mm diameter (3M ESPE RelyX Fiber Post, St. Paul, MN, USA) was used. To create an 11mm post space, the condensed gutta-percha was removed using a heated plugger. The post space was then irrigated with 2ml of the assigned irrigant solution. With a low speed hand piece, sequential reamers (3M ESPE) were used to shape the canals. RelyX-Unicem (3M ESPE) and MultiCore Flow (Ivoclar Vivadent Inc, Amherst, NY, USA) were used to cement the fiber posts according to the manufacturers’ guidelines.