Retention of CAD/CAM Crowns Luted with a New Biomimetic Cement

Objectives: To measure the tensile strength of e.max copings cemented with different cements following thermocycling.
Methods: 40 extracted non-carious mandibular premolar teeth were mounted in acrylic. The teeth were prepared to uniform dimensions (22° total taper) using a flat-end tapered diamond bur (846.11.025HP, Brasseler) and a 3mm preparation height. The surface area of the prepared surface was calculated with digital microscopy. The teeth were scanned with a Cerec 3 (Sirona) digital scanner. E.max crowns were milled using Cerec 3 mill (Sirona) and sintered in a Programmat CS2 oven (Ivoclar Vivadent). The crowns (n=10) were then cemented with either Activa Bioactive (PulpDent), Ceramir (Doxa), Multi-Link Automix (Ivoclar Vivadent), or RelyX Unicem 2 (3M ESPE) cement. Monobond Plus (Ivoclar Vivadent) was applied to the crowns in the Activa Bioactive, Multi-link Automix and RelyX Unicem 2 groups. Crowns were allowed to self-cure under a 2.5kg weight. The crowns were stored in a moist bag for 24hours at 37°C, thermocycled for 10,000cycles from 5-50⁰C with a 30second dwell time. The specimens were placed in a custom fixture in a universal testing machine and loaded in tension at a crosshead speed of 0.5mm/min until debonding. The retention strength (MPa) at debonding was determined from the maximum recorded tensile force and surface area of the preparation. Data were compared with a 1-way ANOVA and Tukey analysis (alpha=0.05).
Results: Significant differences between cements were noted with 1-way ANOVA (p=0.02). Materials can be categorized into significantly different groups with Tukey analysis as represented by the letters in the chart below.
Conclusions: One of the bioactive cements produced statistically similar crown retention strength as both the reference resin cements.