Influence of resin removal treatments on the surface topography and strength of de-bonded lithium disilicate ceramic.

AIM: This study aims to assess the influence of resin removal treatment regimes on the surface topography and compressive strength of de-bonded ceramic surfaces. MATERIAL AND METHODS: Sixty-five lithium disilicate ceramic (LDC) discs were prepared, cleaned, and polished with carbide paper. All samples were etched using 9.6% hydrofluoric acid (HFA). Fifteen samples were taken as positive controls; the remaining 50 samples were subjected to the process of silanization. Resin build-up using dual-cure cement was performed incrementally and light cured. Based on different methods of resin cleaning from de-bonded LDC, the samples were divided into five groups, n=10 each: group 1 (no treatment), group 2 (slow-speed diamond bur), group 3 (1 min heat treatment), Group 4 (6 min heat treatment), and group 5 (sandblasting with Al2O3). Following resin removal, LDC samples were tested under compressive failure load in a universal testing machine. Five disc specimens from each group were sputter coated with gold for scanning electron microscopy (SEM). Analysis of variance (ANOVA) and Tukey's post hoc test was used for descriptive statistics. Level of significance was established at p<0.05. RESULTS: The highest compressive strength with significant difference among all experimental groups was found in group 5 (321.54 ± 13.25 MPa) (p<0.05). The lowest compressive strength values, presenting significant difference compared with all other groups, were displayed in group 1 (158.57 ± 5.22 MPa) (p<0.05). Compressive strength among group 2 (231.54 ± 15.55 MPa), group 3 (237.81 ± 10.81 MPa), and group 4 (255.53 ± 8.95 MPa) specimens was statistically comparable (p>0.05). On SEM, heat-treated specimens confirmed coarser granules, with mild porosities and roughening, whereas sandblasted specimens exhibited consistent evenness with moderate porosity and loss of glazed surface. CONCLUSION: De-bonded LDC surface, treated with heat treatment and sandblasting procedures, exhibited removal of residual resin and significantly high compressive strength compared with non-cleansed ceramic surface.

Influence of resin cements and root canal disinfection techniques on the adhesive bond strength of fibre reinforced composite post to radicular dentin.

AIM: To determine the push out bond strength (PBS) of fibre reinforced composite post (FRCP) bonded to radicular dentin using different cement types total etch resin cement (TERC) and Self-adhesive resin cement (SARC) conditioned with (PDT, 5.25 % NaOCl with EDTA and 1% NaOCl) MATERIALS AND METHODS: Sixty freshly extracted (orthodontic purpose) human single rooted mandibular premolars were collected. Teeth were disinfected and coronal part of all samples were removed. Cleaning shaping and finishing of canal space was performed and filled with gutta percha via lateral condensation. Post space was prepared and disinfected with three irrigating solutions. Samples in group 1 and 2 disinfected 5.25 % NaOCl with EDTA, group 3 and 4 steriled with 1% NaOCl and group 5 and 6 disinfected with Methylene Blue photodynamic therapy (PDT). Based on the resin cement, FRCP was luted with TERC in group 2, 4 and 5; and with SARC in group 1,3 and 6 respectively. All specimens were subjected to aging and push-out bond strength (PBS) on universal testing machine after sectioning of each sample in three segments (coronal, middle and apical). Following push out bond strength (PBS), debonded surface were observed under stereomicroscope at 40x magnification. PBS were equated by means of analysis of variance (ANOVA) and Tukey's post hoc test maintaining level of significance (p < 0.05) RESULTS: Group 1 (SARC) and 2 (TERC) disinfected with 5.25 % NaOCl with 17 % EDTA, TERC (group 2) showed higher extrusion bond strength at all three levels coronal (9.25 ±â€¯0.21 MPa) middle (8.81 ±â€¯0.94 MPa) and apical (8.21 ±â€¯0.93 MPa). Whereas, canal space sterilized with 1% NaOCl [group 3 (SARC) and group 4 (TERC)], posts cemented with TERC exhibited the higher PBS at all three levels of root canal (10.22 ±â€¯0.36 MPa), (9.68 ±â€¯0.51 MPa), (6.33 ±â€¯0.08 MPa). Similarly, among PDT disinfected fiber post [group 5 (TERC) and group 6 (SARC)], TERC exhibited the greater PBS values at coronal, middle and apical levels (6.25 ±â€¯0.39 MPa) (5.17 ±â€¯0.22 MPa) (4.32 ±â€¯0.69 MPa) compared to SARC specimens CONCLUSION: Irrespective of canal irrigant, fiber post bonded with TERC showed higher PBS at coronal and middle third. Fiber post bonded with SARC when irrigated with 5.25 % NaOCl with EDTA, 1% NaOCl displayed higher PBS at apical third. Canal disinfected using PDT showed lower PBS for FRCP compared to 5.25 % NaOCl with EDTA and 1% NaOCl.

Bond strength of universal adhesives to air-abraded zirconia ceramics.

The bond strength of universal adhesives to air-abraded zirconia ceramic was evaluated. Overall, 40 zirconia ceramic blocks with dimensions of 6 × 6 × 4 mm were cut from pre-sintered blanks. The sintered blocks were embedded in self-cured acrylic resin. The zirconia blocks were then randomly allocated to four groups (n = 10) in which different universal adhesives were used, except for the control group in which no universal adhesive was used. A silicon mold was used to build the resin cement. All specimens were stored in distilled water for 24 h at 37°C and mounted on a universal testing machine. They were then subjected to shear bond strength testing at a cross-speed of 0.5 mm/min until failure occurred. The failure modes were analyzed using a digital microscope at 50× magnification. Univariate one-way analysis of variance and Tukey's post-hoc test were used for statistical analysis. Compared with the control group, the groups with universal adhesives showed statistically significant differences (P < 0.05). In addition, there was no statistically significant difference in the bond strengths of the groups with universal adhesives (P > 0.05) . After 24 h of storage, the cementation bond to air-abraded zirconia ceramic was improved by the application of a universal adhesive.