Effect of temporary cement on the bond strength of adhesively cemented ceramic overlays. An in vitro study

Determine whether temporary cement penetrates into dentin tubules and how it affects the tensile bond strength of adhesively cemented restorations. Twenty six extracted intact premolars were included in this study. Six teeth were grounded to expose dentine surface and PMMA overlays were cemented with TempBond NE (Kerr Dental)on them. Temporary cement residues were polished for three samples, and left for the other three. All specimens were broken along vertical axis to undergo SEM/EDX (SEM, Tescan Mira/ LMU; EDX, Oxford Instruments X-MaxN detector size 150 mm2) analysis to detect Zn ions that are present in temporary cement. Remaining twenty teeth were embedded in 16x25mm PMMA cylinder perpendicular to vertical tooth axis. The teeth were grounded to expose dentine surface. Twenty zirconia overlays (Katana Zirconia STML, Kuraray Noritake) (13.15x3.2 mm) and ten PMMA overlays were fabricated to simulate temporary restoration. All teeth were divided in two equal groups. In the first group temporary PMMA overlays were cemented on each tooth surfaces by TempBond NE, subsequently cleaned by rotary polishing brush and pumice and sequentially zirconia overlays were cemented adhesively by Panavia V5 (Kuraray Noritake) – (PV5-1) according to protocol. For second group zirconia overlays were directly cemented by PanaviaV5 to teeth surfaces – (PV5-2). After cementation the bond strength was evaluated by tensile bond strength test (Instron Universal Machine, Norwood, USA) with a head speed of 0.5mm/min. Zn ions were detected in both groups respectively up to 25μm in depths despite whether temporary cement is removed or not. PV5-2 showed statistically higher tensile bond strengths (70,6-108,59 N) than PV5-1 (60,3-80,8 N). In limitation of this study it is concluded that after temporization temporary cement remnants remain in dentine tubules. The use of temporary cement does not alter bond strength of ceramic restorations luted to teeth surfaces using the tested adhesive system significantly.