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.

This study aimed at evaluating the efficacy of a novel silver-citrate root canal irrigation solution (BioAKT) on smear layer removal, sealer penetration after root canal instrumentation and antibacterial activity. Single-root teeth were endodontically treated, sealed with an epoxi-amine resin sealer and irrigated using: Group I: 5.25% sodium hypochlorite (NaOCl); Group II: silver-citrate solution (BioAKT); Group III: phosphate buffer solution (PBS); Group IV: 17% ethylenediaminetetraacetic acid (EDTA). Smear layer removal and silver deposition at the coronal, middle and apical portion of each canal were analyzed using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Sealer penetration into dentinal tubules at coronal, middle and apical portion was assessed through dye-assisted confocal microscopy (CSM). Both SEM and CSM micrographs were evaluated by two examiners (κ = 0.86), who were blind to the irrigation regimens; scores were given according to the degree of penetration of the sealer. Data analysis included Pearson’s x² and Sidak’s multiple comparisons. Dentin discs were polished and sterilized. Enterococcus faecalis biofilms were grown using a continuous-flow bioreactor under anaerobic conditions for 72 h. Specimens were irrigated with the tested solutions, and bacterial viability was assessed using a tetrazolium salt assay (MTT). Statistical analysis included one-way ANOVA and Student’s post-hoc t-test (p < 0.05). BioAKT and EDTA were the most efficient solutions both in removing the smear layer and allowing sealer penetration. However, at the apical portion BioAKT performed significantly better compared to EDTA both in smear layer removal and sealer penetration (p < 0.05). BioAKT and NaOCl showed comparable antibacterial effect (p = 0.53). In conclusion, BioAKT represents a suitable smear layer removal agent, which allows for reliable sealer penetration at the apical portion of the root canal system and offers significant antibacterial properties.

Evaluate the remineralisation ability of experimental resin-based materials containing Fluoride-Doped Calcium Phosphate (FDCP), applied in mineral-deficient dentine in combination with a biomimetic dual-analogue primer. Artificial dentine carious lesions were created in occlusal cavities of human molars. An experimental resin-based adhesive and flowable composite, containing FDCP (10wt% and 20wt%, respectively), were applied (±) with a biomimetic primer containing polyacrylic acid and sodium tripolyphosphate. A glass-ionomer cement and a conventional adhesive/composite were used as comparative materials. All specimens were submitted to chewing simulation in artificial saliva (AS). Subsequently, these were cut into slabs and submitted to Knoop microhardness testing and Raman spectroscopy (AS: 0, 15, 30 and 60 days). Further specimens were analysed through confocal scanning microscopy (AS: 0, 60 days). Total demineralised dentine and disc-shape materials were analysed through FTIR, SEM and EDX (Ca/P ratio) after prolonged contact in AS. Data were statistically analysed (two-way ANOVA and multiple comparison Bonferroni; α=0.05). Only the experimental FDCP materials induced a significant increase in microhardness after storage in AS, especially in those specimens pre-treated with the biomimetic primer, except at 50 µm underneath the interface. Raman and CLSM analysis corroborated such results. The ability of the experimental FDCP resin-based materials to induce apatite-like deposition was demonstrated through SEM-EDX and FTIR. Resin-based materials containing FDCP can mineralise the mineral-deficient dentine, especially when combined with a biomimetic dual-analogue primer. Such Innovative ion-releasing restorative systems applied after selective caries removal might promote remineralisation of fully and partially demineralised dentine and increase the durability of dental restorations.

This study evaluated at baseline (T0) and after thermocycling (TC) the dentine bonding performance of an experimental bonding system containing fluoride-doped calcium phosphate (FDCP) used in combination with a biomimetic dual-analogue dentine conditioner (PRM). Their effect on dentine enzymatic activity was also evaluated, along with fractographic and ultramorphology/nanoleakage characteristics. An experimental FDCP-containing primer and bond resin system was generated and applied on dentine with or without PRM. Controls included a commercial universal adhesive (SCH) and a glass ionomer cement (GIC). Resin-dentine matchsticks were created and subjected to microtensile bond strength (µTBS) testing at 24 h or after thermo-aging (10,000 cycles). Failure mode and fractographic SEM analyses were performed post-µTBS test. Interfacial characteristics and in situ zymography were evaluated through confocal microscopy at T0 and after TC. Gelatine zymography was performed on protein extracts from dentine powder pretreated with the tested materials. Data from the µTBS test were statistically analysed (α = 0.05). SCH showed a significant drop in µTBS (p < 0.05) with adhesive failures and collagen degradation often observed after TC. GIC specimens had the lowest µTBS values (p < 0.05), but no significant drop after TC (p > 0.05). The experimental system was characterised by lower µTBS values than SCH, but with no significant drop after TC (p > 0.05). However, specimens in the experimental groups showed at the bonding interface evident mineral deposition, with less enzymatic activity compared to controls. The FDCP-containing experimental adhesive system maintained the bonding performance after TC, protecting the hybrid layer especially when used in combination with PRM. Innovative ion-releasing restorative systems play a crucial role in preserving the integrity of hybrid layers. These systems promote a remineralisation process that not only reinforces the hybrid layers but also inhibits dentine proteolytic enzymes, thereby enhancing the chances of creating long-lasting dental restorations.