Effect of Different Adhesive Strategies and Time on Microtensile Bond Strength of a CAD/CAM Composite to Dentin

PURPOSE

The aim of this study was to evaluate the effect of adhesive strategy and time on the microtensile bond strength of a computer-aided design/computer-aided manufacturing (CAD/CAM) composite to dentin.

METHODS AND MATERIALS

Sixty CAD/CAM composite blocks were bonded to human dentin with simplified bonding agents using etch-and-rinse and self-etching approaches and amine-based and amine-free resin cements, with and without the application of a dual-cure activator (DCA; n=10): SBP-ARC (Adper Single Bond Plus + RelyX ARC), SBP-RXU (Adper Single Bond Plus + RelyX Ultimate), SBP-DCA-RXU (Adper Single Bond Plus + DCA + RelyX Ultimate), SBU-ARC (Scotchbond Universal + RelyX ARC), SBU-RXU (Scotchbond Universal + RelyX Ultimate), and SBU-DCA-ARC (Scotchbond Universal + DCA + RelyX ARC). Each specimen was light cured for 40 seconds under load and stored in distilled water at 37°C for seven days. Stick-shaped specimens (1.0 mm²) were obtained. Half of the specimens underwent microtensile bond strength testing, and the other half were subjected to the same tests after six months of storage. Failure mode was determined using an optical microscope (40×). The data were analyzed by a two-way analysis of variance followed by the Games-Howell test and Student t-test (preset alpha of 0.05).

RESULTS

After seven days, SBU-RXU presented the highest mean bond strength, statistically different from only SBU-ARC (p<0.05). Most of the groups exhibited a statistically significant reduction in bond strength after 6 months (p<0.05), except SBP-RXU and SBU-ARC (p>0.05).

CONCLUSION

The adhesive strategy, with different associations between adhesive systems and resin cements, as well as the use of a DCA, affected the bond strength of both amine-free and amine-based resin cements to a CAD/CAM composite.

Light curing in dentistry and clinical implications: a literature review

Contemporary dentistry literally cannot be performed without use of resin-based restorative materials. With the success of bonding resin materials to tooth structures, an even wider scope of clinical applications has arisen for these lines of products. Understanding of the basic events occurring in any dental polymerization mechanism, regardless of the mode of activating the process, will allow clinicians to both better appreciate the tremendous improvements that have been made over the years, and will also provide valuable information on differences among strategies manufacturers use to optimize product performance, as well as factors under the control of the clinician, whereby they can influence the long-term outcome of their restorative procedures.

Indirect Restoration Thickness and Time after Light-Activation Effects on Degree of Conversion of Resin Cement

<p>This study evaluated the effects of indirect restorative materials, curing conditions and time on the degree of conversion (DC) of a dual-cured resin cement using infrared spectroscopy. The resin cement (RelyX Unicem 2, 3M ESPE) was applied to the diamond surface of a horizontal attenuated-total-reflectance unit and activated using one of following conditions: self-cure, direct light exposure, light exposure through indirect restorative materials (resin nano-ceramic: Lava Ultimate, 3M ESPE or feldspathic ceramic: Vita Blocks Mark II, Vita Zahnfabrik). Four thicknesses (0.5, 1.0, 1.5 or 2.0 mm) of each indirect material were analyzed, and the light-activation was performed using a blue LED light. Data (n=5) were analyzed by three-way ANOVA, Tukey's post hoc and Dunnett's tests (α=5%). No significant differences in DC were observed between indirect materials of similar thickness. All groups exhibited higher DC after 10 min than after 5 min. At both times points, the self-cure group exhibited significantly lower DC than all the light exposure groups. Only when the overlying indirect restoration had a thickness of 2 mm did DC decrease significantly. The presence of a thick, indirect restoration can decrease the DC of resin cement. DC after 10 min was higher than after 5 min. The self-cure mode yielded lower DC than the light-activating one.</p>

Effects of coronal substrates and water storage on the microhardness of a resin cement used for luting ceramic crowns

Composite resin and metallic posts are the materials most employed for reconstruction of teeth presenting partial or total destruction of crowns. Resin-based cements have been widely used for cementation of ceramic crowns. The success of cementation depends on the achievement of adequate cement curing.

In Vitro Performance of Class I and II Composite Restorations: A Literature review on Nondestructive Laboratory Trials—Part II

A literature review was conducted on adhesive Class I and II restorations and nondestructive in vitro tests using the PubMed/Medline database for the 1995-2010 period. The first part of this review has presented and critically appraised selected literature dealing with the quality and in vitro behavior of adhesive Class II restorations using photoelasticity, finite element analysis, and microleakage study protocols. This second part reviews additional parameters, which are deformation and fracture resistance to cyclic loading, shrinkage stress and tooth deformation following restoration placement, bond strength (microtensile, tensile, and shear tests), and marginal and internal adaptation. In addition, a “relevance score” has been proposed that aims to classify the different study protocols according, firstly, to the resulting quality, quantity, and consistency of the evidence and then, secondly, to their potential clinical relevance, as estimated by their ability to simulate oral and biomechanical strains. The highest clinical relevance was attributed to marginal and internal adaptation studies, following cyclic loading in a moist environement. However, a combination of in vitro protocols will have an even greater predictive potential and has to be considered as a crucial preclinical research approach with which to investigate the numerous restorative configurations that cannot be efficiently and rapidly tested in vivo.

Effect of waiting interval on chemical activation mode of dual-cure one-step self-etching adhesives on bonding to root canal dentin

OBJECTIVES

The purpose of this study was to evaluate the effect of waiting interval on the chemical activation of dual-cure one-step self-etching adhesives before placing resin core materials on the regional bond strength to root canal dentin.

MATERIALS AND METHODS

Forty-eight post spaces prepared in human lower premolars were applied with four dual-cure one-step self-etching adhesives Estelite Core Quick: ECB/ECQ, Clearfil DC Core Automix: CDB/CDC, Unifil Core EM: UNB/UNC, BeautiCore: BTB/BTC as the manufacturers' instructions. These adhesives were cured with light activation for 10 s, or chemical activation with 0, 10, and 30 s waiting intervals prior to placing resin core material. Resin core materials were then placed into the post space and light-cured for 60 s. After 24h water storage, each specimen was serially sliced into 8, 0.6 mm × 0.6 mm thick beams for the μTBS test. The regional μTBS data were analyzed using three-way ANOVA and Dunnett's T3 test (p < 0.05).

RESULTS

For the chemical activation with 10 and 30 s waiting intervals, ECB and CDB exhibited significantly improved μTBS, whereas for UNB and BTB, the μTBS were not significantly different but increased with waiting interval. On the other hand, light-activation of all the adhesives produced significantly higher μTBS to root canal dentin than chemical activation (p < 0.05), except for the UNB group.

CONCLUSIONS

For the chemical activation of dual-cure one-step self-etching adhesives, a waiting interval prior to placing resin core material improved μTBS to root canal dentin. Polymerising the adhesives before polymerisation reaction of resin core material would be effective for bonding to root canal dentin.

CLINICAL RELEVANCE

For chemical activation mode as well as light activation mode, pre-curing of adhesive layer before proceeding polymerisation of resin filling material would produce higher bonding performance to dentin in the cavity.

Activation Mode Effects on the Shear Bond Strength of Dual-cured Resin Cements

The light activation of dual-cured resin cements is essential for improved shear bond strength. Bond strength is low in the first minutes following insertion of a resin cement and increases over time. Under clinical conditions, care should be taken to limit occlusal stress immediately after luting an indirect restoration.