Abstract
In recent years zirconia ceramics hold a remarkable place in restorative dentistry because of their advanced mechanical properties. One of their drawbacks is the inferior bonding potential to dental cements compared to other etchable ceramics. There is still no universally accepted protocol for adhesion to zirconia. Purpose: The aim of this study was to determine the influence of different surface treatment and resin cements on shear bond strength in monolithic zirconia surfaces in order to define the optimal adhesive combination. Μaterial and Methods: One hundred eigthty monolithic zirconia ceramic disks were fabricated and were boxed in plastic tubes. They were separated in three main groups according to surface treatment. Control group (POL), sandblasting group (AL) and tribochemical group (SJ). The surface parameters of ten specimens from each group were determined employing an optical interferometric profiler. Two amplitude (Sa, Sz), one hybrid (Sdr) and one functional (Sci) par ...
In recent years zirconia ceramics hold a remarkable place in restorative dentistry because of their advanced mechanical properties. One of their drawbacks is the inferior bonding potential to dental cements compared to other etchable ceramics. There is still no universally accepted protocol for adhesion to zirconia. Purpose: The aim of this study was to determine the influence of different surface treatment and resin cements on shear bond strength in monolithic zirconia surfaces in order to define the optimal adhesive combination. Μaterial and Methods: One hundred eigthty monolithic zirconia ceramic disks were fabricated and were boxed in plastic tubes. They were separated in three main groups according to surface treatment. Control group (POL), sandblasting group (AL) and tribochemical group (SJ). The surface parameters of ten specimens from each group were determined employing an optical interferometric profiler. Two amplitude (Sa, Sz), one hybrid (Sdr) and one functional (Sci) parameters, were acquired. Two specimens from each group were further analyzed by Raman microspectroscopy to quantify the zirconia phase ratio of all treated surfaces.Three different concept resin cements were used: Panavia 2.0 (PAN), Multilink Automix (ML) and Permacem 2.0 (PC). A prehydrolyzed silane primer was applied on the surface of SJ group. All specimens were stored for a week in deionized water at 37 °C and half of them (N=90) underwent further water thermocycling for 500 cycles (5 oC and 55 oC, with 10 s dwell time and 20 s immersion time). All samples were loaded under shear testing in a universal testing machine (Tensometer 10, Monsanto, USA) at a cross-head speed of 0.5 mm/min up to fracture. The debonded zirconia surfaces were examined under a stereomicroscope (M80, Leica, Weltzar, Germany) at 25× magnification to assess the failure modes. Areas which were covered with zirconia primer in SJ group without resin cement remnants were added in the remaining resin cement percentage. The debonded areas were characterized with 5 different scores, based on the percentage area covered by resin (1: 0-20%, 2: 20-40%, 3: 40-60%, 4: 60-80% and 5: 80-100%). Score 1 is considered as predominating adhesive, 2-4 as mixed and 5 as predominating cohesive. In optical profilometry, one way ANOVA was used to evaluate overall statistical significance (Wilk’s λ) and subsequent evaluations were done using the standard univariate procedure. Individual comparisons were carried out using the LSD method (Least Significant Difference). A 3-way ANOVA was used in order to statistically evaluate the surface treatment, cement type and immersion type combinations as measured by shear bond strength. Individual comparisons were performed using the LSD statistic. For the statistical evaluation of each resin cement type of fracture a 3X2 cross tabulation was used. All two way tables were tested for statistical significance using the Pearson-chi-square statistic. All analyses were performed using the STATISTICA 10 software from StatSoft Inc. Results: Control group (POL) had significant lower roughness measurements in all parameters than surface treatment groups AL and SJ. Groups AL and SJ had no significant differences in three roughness parameters (Sa, Sz and Sdr). Sdr ranged from 4,5 % in POL group to 23,5 % in AL and SJ group. Monoclinic fraction was high (33-43 %) and was not influenced by surface treatment. Thermocycling reduced shear bond strengths. Permacem 2.0 and Mutilink Automix combined with tribochemical silica coating and primer Monobond plus had the highest shear bond strengths (24,9 and 23,8 MPa respectively). Panavia F 2.0 had higher bond strength aftel AL treatment (15,7 MPa). Multilink Automix had almost zero values in POL and AL treatments (0,4 and 2,4 MPa respectively). The increase in shear strength values is followed by transition to a more cohesive failure mode. The groups with low bond values had less residual cement (score 1 and 2), while groups with high values had significantly larger amounts of cement (score 3,4 and 5).Conclusion: Within the limitations of the current experiment, it can be concluded that silica coating treatment in combination with chemical active monomers is a promising luting concept for zirconia materials
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