Filler Mixed Into Adhesives Does Not Necessarily Improve Their Mechanical Properties.

OBJECTIVES: To investigate the influence of filler type/loading on the micro-tensile fracture strength (µTFS) of adhesive resins, as measured 'immediately' upon preparation and after 1-week water storage ('water-stored'). METHODS: The morphology and particle-size distribution of three filler particles, referred to as 'Glass-S' (Esschem Europe), 'BioUnion' (GC), and 'CPC_Mont', were correlatively characterized by SEM, TEM, and particle-size analysis. These filler particles were incorporated into an unfilled adhesive resin ('BZF-29unfilled', GC) in different concentrations to measure the 'immediate' µTFS. After 1-week water storage, the 'water-stored' µTFS of the experimental particle-filled adhesive resins with the most optimum filler loading, specific for each filler type, was measured. In addition, the immediate and water-stored µTFS of the adhesive resins of three experimental two-step universal adhesives based on the same resin matrix but varying for filler type/loading, coded as 'BZF-21' (containing silica and bioglass), 'BZF-29' (containing solely silica), and 'BZF-29_hv' (highly viscous with a higher silica loading than BZF-29), and of the adhesive resins of the gold-standard adhesives OptiBond FL ('Opti-FL', Kerr) and Clearfil SE Bond 2 ('C-SE2', Kuraray Noritake) was measured along with that of BZF-29unfilled (GC) serving as control/reference. Statistics involved one-way and two-way ANOVA followed by post-hoc multiple comparisons (α<0.05). RESULTS: Glass-S, BioUnion, and CPC_Mont represent irregular fillers with an average particle size of 8.5-9.9 µm. Adding filler to BZF-29unfilled decreased µTFS regardless of filler type/loading. One-week water storage reduced µTFS of all adhesive resins except BZF-21, with the largest reduction in µTFS recorded for BZF-29unfilled. Among the three filler types, the µTFS of the 30 wt% Glass-S and 20 wt% BioUnion filled adhesive resin was not significantly different from the µTFS of BZF-29unfilled upon water storage. CONCLUSIONS: Adding filler particles into adhesive resin did not enhance its micro-tensile fracture strength but appeared to render it less sensitive to water storage as compared to the unfilled adhesive resin investigated.

Effect of a hyperbaric environment (diving conditions) on adhesive restorations: an in vitro study.

Objectives No recent study has addressed the effect of diving conditions (pressure increase) on adhesive restorations. We evaluated the impact of a simulated hyperbaric environment on microleakage of the dentine-composite resin interface. The ultimate aim was to propose recommendations for restorative dentistry for patients who are divers to limit barodontalgia (dental pain caused by pressure variations of the environment) and may lead to dangerous sequelae.Methods We bonded 20 dentine disks by using an adhesive system (Scothbond Universal) to ten intact composite cylinders and ten composite cylinders with porosity (Ceram X mono). For each group, the samples were divided into two subgroups, one submitted to a simulated hyperbaric environment and the other to an ambient environment. All samples were immersed in a silver nitrate solution to evaluate microleakage at the interface after analysis with a camera.Results Dye percolation for groups in the hyperbaric environment was greater than groups in ambient environment. For each subgroup, dye percolation was greater for samples with than without porosity.Conclusions High percolation percentages demonstrate that our simulated hyperbaric condition led to loss of sealing at the dentine-composite resin interface, especially with porous composites.Clinical significance Respect of the protocol and the quality of condensation for adhesive restorations are important in all clinical situations, especially for patients who are divers. A more interventionist approach must be adopted with these patients.