Retention of different all ceramic endocrown materials cemented with two different adhesive techniques

The purpose of this in vitro study was to evaluate the influence of two adhesive techniques on the retentive force of four all ceramic endocrowns.

Forty maxillary first molars of approximately similar size and shape were collected. The teeth were all decoronated 2 mm above the level of proximal cement-enamel junction (CEJ) and were all endodontically treated. The teeth were then randomly divided equally into four groups (10 each) according to all ceramic material used, as follows: Group I (VE) - Ten prepared molars were restored with hybrid ceramic (Vita Enamic); Group II (LU) - Ten prepared molars were restored with resin Nano-ceramic (Lava Ultimate). Group III (CD) - Ten prepared molars were restored with zirconia-reinforced lithium di-silicate ceramic material (Celtra Duo); Group IV (LZ) - Ten prepared molars were restored with zirconia ceramic (Lava Zirconia). Each group was then subdivided into two equal subgroups (n=5) according to the type of cement (adhesive technique) used for cementation. Subgroup A (RX ARC): the endocrowns were cemented with a total-etch adhesive resin cement (RelyX ARC). Subgroup B (RXU): the endocrowns were cemented with self-adhesive resin luting cement (RelyX UniCem). The restorations were designed with an outer cylindrical handle located on buccal and palatal surfaces to provide a mean for the removal of the endocrowns during the pull-out testing. The cemented endocrowns were thermocycled and then removed along the path of insertion using a universal testing machine at 0.5 mm/min. The retentive force was recorded, and the stress of dislodgement was calculated using the surface area of each preparation.

The highest mean dislodgement stresses were 64.3 MPa for Group I (VE), whereas there was no statistically significant difference between Group I, II and III and LZ showed the lowest values with significant difference between the other three groups. Regarding the type of cement, there was a statistically significant difference between RelyX ARC (mean=60.09 MPa) and RelyX Unicem (mean=49.73 MPa).

Retention of Vita Enamic, Lava Ultimate, and Celtra Duo are significantly higher than Lava Zirconia.