Effects of Ions-Releasing Restorative Materials on the Dentine Bonding Longevity of Modern Universal Adhesives after Load-Cycle and Prolonged Artificial Saliva Aging

Abstract

This study aimed at evaluating the microtensile bond strength (MTBS) and fractographic features of dentine-bonded specimens created using universal adhesives applied in etch-and-rinse (ER) or self-etching (SE) mode in combination with modern ion-releasing resin-modified glass-ionomer cement (RMGIC)-based materials after load cycling and artificial saliva aging. Two universal adhesives (FTB: Futurabond M+, VOCO, Germany; SCU: Scotchbond Universal, 3M Oral Care, USA) were used. Composite build-ups were made with conventional nano-filled composite (AURA, SDI, Australia), conventional resin-modified glass ionomer cement (Ionolux VOCO, Germany), or a (RMGIC)-based composite (ACTIVA, Pulpdent, USA). The specimens were divided in three groups and immersed in deionized water for 24 h, load-cycled (350,000 cycles; 3 Hz; 70 N), or load-cycled and cut into matchsticks and finally immersed for 8 months in artificial saliva (AS). The specimens were cut into matchsticks and tested for microtensile bond strength. The results were analyzed statistically using three-way ANOVA and Fisher’s LSD post hoc test (p < 0.05). Fractographic analysis was performed through stereomicroscope and FE-SEM. FTB showed no significant drop in bond strength after aging. Unlike the conventional composite, the two RMGIC-based materials caused no bond strength reduction in SCU after load-cycle aging and after prolonged aging (8 months). The SEM fractographic analysis showed severe degradation, especially with composite applied on dentine bonded with SCU in ER mode; such degradation was less evident with the two GIC-based materials. The dentine-bond longevity may be influenced by the composition rather than the mode of application (ER vs. SE) of the universal adhesives. Moreover, the choice of the restorative material may play an important role on the longevity of the finalrestoration. Indeed, bioactive GIC-based materials may contribute to maintain the bonding performance of simplified universal adhesives over time, especially when these bonding systems are applied in ER mode.

Bonding Effectiveness of Bioactive Self-Adhesive Restorative Material to Enamel and Dentin Using Different Bonding Protocols

“…(29) Dentin specimens bonded directly with ACITVA showed significantly low bond strength results at 24 h but durable on storage. As previously mentioned, (9) modern ion-releasing restorative materials might have the ability of preserving bonding performance of universal adhesives vulnerable to degradation over time.…”

“…All enamel groups after 6 months storage, whether bonded using adhesive system in etch and rinse mode, self-etch mode or directly bonded to ACITVA, showed stable bond strength which might be related to the bioactivity of ACITVA. Sauro et al, 2019 (9) reported that the use of modern ionreleasing restorative materials such as ACTIVA may preserve the bonding performance of those universal adhesives that are more prone to degradation after aging. ESEM images of enamel specimens bonded directly to ACTIVA demonstrated the formation of interlinking mesh of minerals at the interfacial gaps between enamel and ACITVA after 6 m storage ( fig.…”

“…They are called universal systems as they could be used in different modes as etch and rinse and self-etch modes, with different substrates as enamel and dentin to be bonded to both direct and indirect restorations. (7)(8)(9) Considering their composition, universal adhesives can be classified as simplified systems because all ingredients, including acidic functional monomers and solvents, are incorporated into one bottle maintaining the "all-in-one" philosophy. (8) They are similar to one-step self-etch adhesive systems, so they still have presented some issues regarding their bonding performance, degradation, and longevity.…”

“…(8) They are similar to one-step self-etch adhesive systems, so they still have presented some issues regarding their bonding performance, degradation, and longevity. (9) Chemical adhesion to tooth tissue occurs as a result of an ion exchange process at the tooth ̸ restoration interface. This is attributed to chelation of the calcium ions in the surface of the hydroxyapatite layer (2) which might be more evident upon storage in biological fluid as saliva.…”

Effect of Casein Phosphopeptide–Amorphous Calcium Phosphate on Fracture Resistance of Reattached Tooth Fragments Using Conventional and Self-Adhesive Bioactive Flowable Composite

“…Fluoroaluminum silicate particles and polyacid components undergo the acid-base setting reaction. 19 The smart material of Activa has the potential of releasing and recharging significant amounts of calcium, phosphate, and fluoride from the saliva or in the presence of a source like CPP-ACP paste, and therefore stimulates the apatite formation. This dynamic role acts against the marginal microleakage and discoloration of the restoration margin and improves the mechanical properties.…”