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The study aimed to evaluate the effect of graphene oxide (GO) nano-filler content in experimental dental adhesive on its degree of conversion (DC), microtensile bond strength (μTBS) and structural reliability, using Fourier transform infrared spectroscopy (FTIR), Micro-Raman spectroscopy and Scanning electron microscopy (SEM). A resin adhesive was fabricated (control adhesive - CA) and fabricated GO nano-particles were added at 0.5% and 2.0% (m/m) to produce adhesives GOA1 and GOA2 respectively. One hundred and two teeth (specimens) were prepared for dentin exposure and conditioned with 36% phosphoric acid. Specimens in each group (n = 34) were treated with formulated adhesives (CA, GOA1 & GOA2) and photo-polymerized for 20 s followed by composite build up. Sixty specimens were used for μTBS testing in the adhesive groups (CA, GOA1 & GOA2), with half exposed to thermocycling (TC) whereas the remaining half (n = 10) stored in distilled water. Seven specimens each were assessed using SEM and Micro-Raman spectroscopy, in each adhesive group (n = 7). DC for the adhesives was assessed using FTIR. The means of μTBS and DC were analyzed using ANOVA and post hoc Tukey multiple comparisons test. GO nano-filler content showed significant influence on the adhesive μTBS in comparison to controls (p < 0.01). Ageing (TC) revealed significant reduction in the μTBS, except in GOA2 specimens, which showed comparable outcomes among TC and non-TC specimens (p > 0.05). DC was significantly higher in control adhesive [46.8 (3.6)%] compared to GOA2 [37.7 (4.2)%] specimens, however DC was comparable among GOA1 [42.3 (2.9)%] and GOA2 [37.7 (4.2)%] specimens (p > 0.05) respectively. GO exhibited interaction within adhesive and tooth dentin comparable to control adhesive. Increasing GO content showed increase in μTBS of adhesive to dentin, but a decrease in degree of conversion. Under ideal conditions, experimental adhesive with 2% GO content showed acceptable bond strength and DC; and should be further assessed under dynamic conditions to recommend clinical use.

Aim: The study aimed to assess graphene oxide (GO) adhesive and its dentin interaction using scanning electron microscopy (SEM), MicroRaman spectroscopy and Microtensile bond strength (μTBS). Materials and Methods: Experimental GOA and control adhesives (CA) were fabricated. Presence of GO within the experimental adhesive resin was assessed using SEM and Micro-Raman spectroscopy. Ninety specimens were prepared, sixty teeth were utilized for μTBS, twenty for SEM analysis of interface for CA and GOA and ten were assessed using microRaman spectroscopy. Each specimen was sectioned and exposed dentine was conditioned (35% phosphoric acid) for 10 s. The surface was coated twice with adhesive (15 s) and photopolymerized (20 s). Composite build-up on specimen was photo-polymerized. Among the bonded specimens, thirty specimen were assessed using Micro-Raman spectrometer, SEM and energy dispersive X-ray spectroscopy (EDX), whereas remaining specimens were divided in to three sub-groups ( n = 10) based on the storage of 24 h, 8 weeks and 16 weeks. μTBS testing was performed at a crosshead speed of 0.5 mm/min using a microtensile tester. The means of μ-tbs were analyzed using ANOVA and post hoc Tukey multiple comparisons test. Results: No significant difference in μTBS of CA and GOA was observed. Storage time presented a significant interaction on the μTBS ( p < 0.01). The highest and lowest μTBS was evident in CA (30.47 (3.55)) at 24 h and CA (22.88 (3.61)) at 18 weeks. Micro-Raman analysis identified peaks of 1200 cm-1 to 1800 cm1, D and G bands of GO nanoparticles in the resin. Uniform distribution of graphene oxide nanoparticles was present at the adhesive and hybrid layer. Conclusion: GO showed interaction within adhesive and tooth dentin similar to CA, along with formation of hybrid layer. In ideal conditions (absence of nanoleakage), graphene oxide modified adhesive shows comparable bond strength and durability of resin dentine bond.

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This study evaluates the repair bond strength of resin-matrix and glass-matrix CAD/CAM ceramic materials based on two repair systems. Thirty specimens measuring 2.5 mm in thickness were prepared from Crystal Ultra (CU), Vita Enamic (EN), Lava Ultimate (LU), Cerasmart (CS), and Vitablocs Mark II (VM2) materials and aged for 5000 thermal cycles. Specimens were randomly allocated into three groups: control, Monobond-S (MS) primer, and Monobond Etch & Prime (MEP). Composite resin (Tetric N Ceram) (5 mm in diameter and 2 mm thick) was packed and light-cured onto treated specimen surfaces. Subsequently, the specimens’ shear bond strength (SBS) was evaluated, and failure modes was recorded. Statistical analysis was performed using factorial ANOVA and Tukey’s post hoc tests (a = 0.05). The factorial ANOVA revealed significant interactions between the material type and repair system, which was significant (p < 0.01). The highest and lowest SBS were obtained for CU (27.09 ± 1.11) and VM2 (4.30 ± 0.59) in MS and control groups, respectively. In all the groups, CU demonstrated higher SBS, whereas VM2 demonstrated lower SBS. There were no significant differences in SBS between EN and LU, and CS and CU in all the study groups (p > 0.05). The Monobond-S repair system provided non-significantly higher SBS compared to the MEP systems, except for VM2 and LU materials. The new resin-matrix CAD/CAM material demonstrated the highest SBS compared to the other materials for both conventional and MEP repair systems. Both repair systems showed clinically acceptable bond strength and allowed for successful repair of the resin-matrix ceramic materials.

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