Influence of Clinical-applications to Prepared Abutment-surface on Bonding of CAD/CAM-ceramic-crown-restoration

Objectives: The purpose of this study was to examine the influence of clinical applications to prepared abutment surface on bonding of CAD/CAM-ceramic-crown-restoration.
Methods: Standardized CAD/CAM-ceramic-crown abutment was prepared in 40 extracted human mandibular-premolars. Abutment specimens were divided into two groups; an immediate-dentin-sealing group(S+) and a non-sealing group(S-), 20 each. Dentin surfaces of S+ specimens were sealed with an all-in-one adhesive system and a flowable resin-composite(CLEARFIL Universal Bond Quick and CLEARFIL Majesty ES Flow, Kuraray Noritake Dental). Optical impression was taken by CEREC AC Omnicam(SW v4.3, Dentsply Sirona) and then CAD/CAM-crown was individually fabricated from VITABLOCS Mark II(VITA) by CEREC MC XL. A half of both S+ and S- specimens were temporarily restored(T+, 10 each) using a bis-acrylic composite(Protemp4 Temporization Material, 3M ESPE) and non-eugenol zinc-oxide cement(TempBond NE, Kerr), regardless of sealing mode. The other specimens were not temporarily treated(T-). After storage for 1 week in 37°C water, the temporary restorative of T+ group was removed, and the abutment surfaces were cleaned with a low-speed-rotated polishing-brush. Each fabricated crown was cemented to individual abutment with an adhesive-resin-cement(PANAVIA V5, Kuraray Noritake Dental). All restored specimens were subjected to cyclic-load at 157N for 90cycles/min, 3 × 105cycles in total, in water at 37°C. Two slabs 1.0mm thick were obtained from each specimen, and were trimmed into a standardized dumbbell-form specimen bonded to the occlusal-dentin-wall(O) and axial-dentin-wall(A). Thereafter, micro-tensile bond strength(µ-TBS) were measured(n=10) and the data were analyzed using two-way ANOVA and Tukey’s test.
Results: Mean µ-TBS in MPa(SD) to O/A were S-T- specimen;3.1(1.4)/4.8(1.5), S-T+;3.6(1.5)/3.5(1.7), S+T-;4.8(1.5)/5.2(2.6), S+T+;4.7(1.2)/4.7(2.7). The temporary restoration did not affect the µ-TBS. Immediate-dentin-sealing influenced the µ-TBS, especially the O-value of S+T- specimens was significantly greater than that of S-T- specimens at p<0.05.
Conclusions: Bonding of CAD/CAM-ceramic-crown-restoration was improved by the immediate-dentin-sealing, and the temporary restoration did not influence the bond-strength.