Effects of sandblasting and silicoating on bond strength between titanium and porcelain.

PURPOSE: The aim of this study was to evaluate the effects of the different sized alumina particles (50 and 150 µm) and tribochemical silica-modified alumina particles (110 µm) on titanium (Ti) surface to identify the most effective method of increasing the bond strength between porcelain and Ti. MATERIALS AND METHODS: Thirty rectangular plates (15 mm × 50 mm × 1 mm) of commercially pure Ti (Cp Ti) Grade 5 (GC Dental Industrial Corporation, Tokyo, Japan) were divided into three groups for different surface modification procedures (n = 10). Ti bonder porcelain, opaque, and dentin layers were fired separately on Ti plates. All specimens were placed in a bending jig for four-point bending test. The load and crosshead displacement data were collected to calculate the strain energy release rate as a G value. RESULTS: Lowest mean G values in J/m2 were in the group sandblasted with 150 µm Al2O3particles (Group 2) (18.6 ± 5), followed by the group sandblasted with 50 µm Al2O3particles (Group 3) (20.8 ± 6.1) and the group sandblasted with 110 µm silicoated Al2O3particles (Group 1) (24.5 ± 4.1). The one-way ANOVA and Bonferroni post hoc tests indicated that there was a statistically significant difference between Group 1 and Group 2 (P < 0.05). There were also no statistically significant differences between Group 1 and Group 3 and Group 2 and Group 3 (P > 0.05). CONCLUSION: The size of alumina particles is not a factor that is directly effective in enhancing the bond strength of Ti-porcelain systems. The bond strength of Ti-porcelain systems can be extremely improved by the application of sandblasting with silica-coated alumina particles.

Effect of final irrigation procedures on fracture resistance of root filled teeth: an ex vivo study.

AIM: To evaluate the effect of chlorhexidine (CHX) on fracture resistance of roots treated with different concentrations of ethylenediaminetetraacetic acid (EDTA). METHODOLOGY: One hundred and twenty intact single-rooted premolar teeth were sectioned below the cementum-enamel junction to standardize the length of the teeth to 12 mm. The canals of one hundred specimens were instrumented with ProTaper Universal rotary instruments up to size F4 and were randomly divided into five groups (n = 20) according to the final irrigating solutions: Group 1: distilled water (DW); Group 2: 5% EDTA and 2.5% NaOCl; Group 3: 17% EDTA and 2.5% NaOCl; Group 4: 5% EDTA, 2.5% NaOCl, DW and 2% CHX; Group 5: 17% EDTA and 2.5% NaOCl, DW and 2% CHX. Root canals were filled with gutta-percha and epoxy resin-based root canal sealer using a single-cone technique. Twenty teeth served as negative controls and were not instrumented nor root filled (Group 6). All specimens were embedded in self-curing acrylic resin and loaded vertically at 0.5 mm min-1 until fracture occurred. The data were evaluated statistically using one-way anova test followed by Holm-Sidak's multiple comparison test (P < 0.05). RESULTS: Group 1 (only DW) had the lowest vertical fracture strength, followed by Group 3 (17% EDTA and 2.5% NaOCl; P < 0.05). Group 6 (negative control group) had the highest fracture resistance. Final irrigation with CHX following irrigation with 17% EDTA or 5% EDTA and 2.5% NaOCl (groups 4 and 5) significantly increased the fracture resistance of roots (P < 0.05). However, the difference between Group 4 and Group 5 was not significant (P > 0.05). CONCLUSIONS: Intracanal CHX rinse of EDTA/NaOCl-treated root dentine enhanced the fracture resistance of roots filled with AH Plus.

Effect of chlorhexidine on bond strength between glass-fiber post and root canal dentine after six month of water storage.

Aim of this study was to assess the influence of chlorhexidine digluconate (CHX) application on bond strength of glass fibre reinforced composite (FRC) posts to root dentine using adhesive luting systems. Forty extracted human mandibular premolars were endodontically treated and root canals were prepared. Teeth were divided into 2 groups according to luting system as SuperBond C&B (etch-and-rinse/chemical cure) and FuturaBond DC (self-etch/ dual cure). Each group was further divided in 2 subgroups (n=10) according to whether CHX was applied or not. Group Futura/CHX: FuturaBond DC + CHX; group Futura: FuturaBond DC; group Super/CHX: Super Bond C&B + CHX; group Super: SuperBond C&B + CHX. Mean and standard deviation (in parenthesis) values of bond strength in MPa were: group Futura/CHX: 8.86 (1.96), group Futura: 7.65 (1.01), group Super/CHX: 17.47(2.93), group Super: 12.41 (3.83). Bond strength values were affected by the type of luting agent and CHX irrigation (p=0.001, two-way ANOVA). There were statistically significant differences among the groups according to one-way ANOVA (p<0.001). Significant differences were observed in bond strength between groups Super/CHX and Super (p=0.023), between groups Futura/CHX and Super/CHX (p<0.001). Application of CHX before luting procedure with etch-and-rinse/chemical cure luting agent of glass FRC post improved long-term bond strength between glass FRC and root dentine.

The evaluation of displacement resistance of glass FRC posts to root dentine using a thin slice push-out test.

AIM: To investigate and compare the displacement resistance of glass fibre reinforced composite (FRC) posts to root dentine after luting with different adhesive systems. METHODOLOGY: A total of 32 noncarious extracted human mandibular premolars were prepared for post-cementation using the FRC Postec system (Ivoclar Vivadent, Schaan, Liechtenstein) and divided into four groups (n = 8). The posts in each group were luted with one or other of the following materials. Group 1: Variolink II/Excite DSC (etch-and-rinse, dual-curing), group 2: Clearfil Esthetic Cement/ED Primer II (self-etch, dual-curing), group 3: Multilink/Multilink Primer (self-etch, chemical-curing) and group 4: Multilink Sprint (self-adhesive, dual-curing). Specimens were sectioned to obtain slices with the post in the centre and with the root dentine overlaid by the autopolymerizing acrylic resin on each side. The displacement resistance was measured using a Universal Testing Machine at a crosshead speed of 0.5 mm min(-1). The displacement resistance of the specimens were calculated and expressed in MPa. Data were analysed with one-way ANOVA and post hoc Tukey's test (P < 0.05). RESULTS: Mean (SD) values of displacement resistance data in MPa are as follows: group 1, 12.08 (2.13); group 2, 12.39 (2); group 3, 11.3 (1.23); group 4, 14.29 (1.84). There were statistically significant differences amongst the groups (P = 0.021). A statistically significant difference was observed for the displacement resistance values between groups 3 and 4 (P = 0.015), that is between Multilink/Multilink Primer and Multilink Sprint. CONCLUSIONS: Glass FRC posts luted with self-adhesive luting system exhibited higher displacement resistance than when luted with chemical-curing self-etch luting system.

The effect of spreader size on fracture resistance of maxillary incisor roots.

AIM: To assess the effect of spreader size used during cold lateral compaction of gutta-percha on fracture resistance of roots in maxillary incisor teeth. METHODOLOGY: The crowns of 50 human maxillary incisor teeth having no carious lesions, no fracture or crazing were resected 2 mm coronal to the cemento-enamel junction. The root canals of the teeth were prepared as follows: Group 1: No canal preparation. Group 2: Preparation using the stepback technique to a size 40 master apical file. Group 3: Canal preparation to size 40 and filling with laterally compacted gutta-percha; the first spreader used was equal to size 40. Group 4: Same as group 3 except the first spreader was equal to size 35. Group 5: Same as group 3 except the first spreader was equal to size 25. For each root, a simulated periodontal ligament was prepared. The roots were than mounted in polyester resin and fractured vertically on a universal testing machine (Shimadzu, Tokyo, Japan). The fracture values of teeth were analysed using Kruskal-Wallis and Mann-Whitney U-tests (P = 0.05). RESULTS: The uninstrumented group had the highest fracture resistance; instrumented, but unfilled roots, demonstrated the lowest resistance values (P = 0.009). There were no differences between the uninstrumented group and group 5 in which a size 25 spreader was used during filling. Use of spreaders larger than size 25 caused a significant reduction in fracture resistance of roots (P < 0.05). CONCLUSION: Spreader size used during lateral compaction of gutta-percha can affect the fracture resistance of roots in extracted teeth.