The effect of repressing on surface topography and microshear bond strength of two pressable ceramics

Objective: This in-vitro study was carried out to investigate the effect of repressing on surface topography and micro-shear bond strength of Lithium di-silicate (IPS e.max press) and zirconia reinforced lithium di-silicate (Celtra press).
Materials and Methods: Two commercially available glass ceramic materials were used in this study; IPS e.max press (Ivoclar, vivadent) and Celtra press (Dentsply, Sirona). The two materials were used to fabricate disc samples. A total of thirty two ceramic disc specimens with 1.2 mm height and 12 mm diameter were constructed. The flat round disc samples for each material(n=16) were randomly divided into two equal groups: group I: Pressed ceramic discs and group II: Repressed ceramic discs (n=8).The disc samples were further subdivided into two equal subgroups according to the type of cement used (n=4): subgroup A: samples were cemented with Multilink automixed ,self-adhesive resin cement. Subgroup B: samples were cemented with Rely X-unicem 2 automixed, self-adhesive resin cement. Fabrication of disc samples for the two tested materials, surface treatment and cementation procedures were done for both types of cements according to manufacturer instructions.
Results: For IPS e.max or Celtra press; there was no statistically significant difference between mean Ra value (µm) of press and repress conditions. IPS e.max showed statistically significantly higher mean micro-shear bond strength than Celtra press.
Conclusions: Pressing of glass ceramics for one injection is recommended. Repressing of glass ceramics improved surface topography but compromises the bond strength.