Microshear bond strength of preheated silorane- and methacrylate-based composite resins to dentin

Effect of preheating nano-hybrid and bulk-fill composites with warm airstream on their microtensile bond strength to dentin

Aims

This study assessed the effect of preheating nano-hybrid and bulk-fill composites with warm airstream on their microtensile bond strength (MTBS) to dentin.

Materials and Methods

In this in vitro study, dentin was exposed in 42 extracted premolars that were assigned to two groups (n = 21) for bonding to EverX Posterior bulk-fill and Grandio nano-hybrid posterior composite. Each group was subdivided into three subgroups for preheating of composite to 50°C by a commercial composite warmer (Subgroup 1), a warm airstream by a hair dryer for 10 s (Subgroup 2), and no heating (room temperature; Subgroup 3). Composite cylinders with a 4-mm height were bonded to the tooth surface with a 5th-generation bonding agent using the incremental technique and cured (each increment for 30 s). The MTBS to dentin was measured, and the bonding interface was evaluated under a stereomicroscope and a scanning electron microscope (SEM). Data were analyzed using one-way and two-way ANOVA, Tukey's test, and independent t-test (α =0.05).

Results

In both composite groups, the mean MTBS of the warm airstream subgroup was significantly higher than that of warmer (P < 0.001) and control (P < 0.001) subgroups. The mean MTBS of the warmer subgroup was significantly lower than that of control subgroup (P = 0.01). The MTBS of the EverX composite was significantly higher than that of the Grandio composite only in the warmer group (P < 0.05). Adhesive failure occurred more frequently in all groups with the highest frequency in airstream subgroup of both composite types.

Conclusion

Preheating with a warm airstream significantly increased the MTBS of both composite types to dentin.

Effect of preheating on the physicochemical properties and bond strength of composite resins utilized as dental cements: An in vitro study

STATEMENT OF PROBLEM

Little is known regarding the use of preheated composite resins to bond indirect restorations and its impact on mechanical properties when compared with resin cements.

PURPOSE

The purpose of this in vitro study was to compare the chemical and physical properties and bond strength to enamel and ceramics of preheated composite resins and resin cements.

MATERIAL AND METHODS

Two composite resins, the microhybrid Filtek Z250XT and the nanoparticulate Z350XT were tested, and 2 commercially available resin cements, the dual-polymerized Rely-X ARC and the light-polymerized Rely-X Veneer were used as controls. A device (HotSet) was used to preheat the composite resins to 69 °C before light-polymerization. The following properties were tested: flexural strength, modulus of elasticity, fracture toughness, microshear bond strength to enamel and ceramics, degree of conversion, flow, sorption and solubility, and color stability. Statistical analysis was done with ANOVA and Holm-Sidak for multiple comparisons (α=.05).

RESULTS

Preheating had no significant effect on the degree of conversion, flexural strength, fracture toughness, solubility, or microshear bond strength to the enamel of the tested composite resins (P>.05). However, preheating increased the sorption and reduced the microshear bond strength to the ceramic (P<.05). The flowability of the composite resins increased with heating but showed lower values when compared with both resin cements (P<.05). Color stability was more affected in the preheated composite resins than in the resin cements.

CONCLUSIONS

The preheating process resulted in little to no benefit in the evaluated properties for the composite resins. Resin cements appear to be the best option for cementing indirect restorations.

[Comparison of the film thickness of composites of different degrees of viscosity]

The measurement of the film thickness of the composite cement Variolink Esthetic («Ivoclar-Vivadent», Liechtenstein) and the microhybrid composite Enamel («Micerium», Italy) was carried out according to ISO 4049: 2009 standards with a load force of 5 kg. While reducing the load force to 5 kg, all materials showed an increase in the film thickness; the film thickness of the Variolink Esthetic composite cement was changed from 23 microns (at 15 kg) to 32 microns (at 5 kg), and the film thickness of the microhybrid composite film Enamel was changed from 39 microns (at 15 kg) to 102 microns (at 5 kg). After preheating, the film thickness was changed from 23 microns (at 15 kg) to 44 microns (at 5 kg).

Bonding Effectiveness of Contemporary Materials in Luting Glass-Ceramic to Dentine: An In Vitro Study

Aim:

To evaluate the shear bond strength (SBS) of resin cements, flowable composites, and a preheated composite in luting glass-ceramic to dentin.

Materials and Methods:

In total, 108 noncaries human third molar teeth embedded in acrylic blocks, grinded from the occlusal surfaces until dentin was exposed, and divided into 9 randomized groups ( n = 12). In total, 108 ceramic samples prepared in disc shape (3mm × 3mm) from IPS e. max CAD (Ivoclar Vivadent) blocks. Four adhesive resin cements: Variolink Esthetic DC (Ivoclar Vivadent), G-CEM LinkForce (GC), Panavia V5 (Kuraray Noritake), Maxcem Elite Chroma (Kerr), and three flowable composites: G-ænial Universal Flo (GC), Herculite XRV Ultra Flow (Kerr), Vertise Flow (Kerr), and one preheated composite: Enamel Plus HRI (Micerium) luted to the prepared occlusal surfaces of the teeth with total-etch, self-etch, and self-adhesive protocols. Then samples were thermocyled (5,000 cycles, 5–55°C, dwell time 20 s). SBS test was performed in a universal testing machine (at 0.5 mm/min). Failure modes were examined under a stereomicroscope at ×25 magnification. Data were analyzed using Kruskal–Wallis and Dunn–Bonferroni tests ( α = 0.05).

Results:

There were statistically significant differences among material types ( P < .05). Highest SBS values found in G-ænial Universal Flo (15.43 ± 5.67), and the lowest values obtained in Maxcem Elite Choroma (SA) (1.25 ± 1.47). There were no significant differences between self-etch (Panavia V5, Maxcem Elite Choroma [SE]) and self-adhesive (Maxcem Elite Choroma [SA], Vertise Flow) protocols ( P > .05).

Conclusion:

Flowable composites can be alternatives to resin cements when bonded with total-etch procedures. Bond strength of self-etch and self-adhesive applications is still to be developed.

Influence of Pre-Heating Regular Resin Composites and Flowable Composites on Luting Ceramic Veneers with Different Thicknesses

The aim of this study was to evaluate of pre-heating, filler contents and ceramic thickness on film thickness, microshear bond strength, degree of conversion and color change on ceramic veneers. Two experimental composites were prepared (Bis-GMA/UDMA/BisEMA/ TEGDMA), with different amounts of filler (65% or 50%wt) simulating a conventional and a flowable composite. The flowable (F) was used at room temperature and, the conventional either at room temperature (C) or pre-heated (CPH). Disk-shaped ceramics with different thickness (0.4 mm, 0.8 mm, 1.5 mm) were prepared. The film thickness was evaluated according to the ISO 4049 (n=10). The microshear bond strength (n=10) was evaluated in enamel using tubing specimens light-cured through the ceramic veneer. The degree of conversion was evaluated using Raman spectroscopy. The color change of the ceramic restorations (n=10) was evaluated by spectrophotometry. The results were submitted to 2-way ANOVA and Tukey's post hoc test (a=5%). For the film thickness 1-way ANOVA was used (a=5%). The C presented the thicker film thickness; the CPH produced a similar film thickness in comparison to the F. All composites showed similar microshear bond strength. The degree of conversion of the F was higher than the C and CPH. The degree of conversion of the composites photo-activated through a 0.4 mm was higher than the composites photo-activated through thicker ceramics. The C showed the highest color change, while the CPH showed similar color change to the F. In conclusion, pre-heated conventional composites seem to be a potential alternative to lute ceramic veneers such as the flowable composites.