Restorative Dentistry & Endodontics

Research Articles

Bonding and fractographic characterization of universal adhesives applied to dentin in multimode strategies: an in vitro study: Samaa M. Morsy, Rim Bourgi, Louis Hardan, Carlos Enrique Cuevas-Suárez, Naji Kharouf, Ahmed A. Holiel; Restor Dent Endod 2026;51(1):e12. Published online February 26, 2026; DOI: https://doi.org/10.5395/rde.2026.51.e12

Abstract PDF PubReader ePub: Objectives
Universal adhesives (UAs) are marketed as versatile systems for both self-etch (SE) and total-etch (TE) modes. While their bond strength has been widely investigated, evidence linking fracture characteristics to bonding performance remains limited. This study evaluated the micro-shear bond strength (μSBS) and failure patterns of three UAs applied in SE and TE modes, complemented by fractographic scanning electron microscopy (SEM) analysis.
Methods
Eighteen extracted human molars were sectioned to expose mid-coronal dentin and randomly allocated to SE or TE application. Three UAs were tested: Tetric N-Bond Universal, All-Bond Universal, and Single Bond Universal (SBU). Composite micro-rods (n = 72) were bonded, thermocycled for 500 cycles between 5°C and 55°C, and subjected to μSBS testing. Fracture surfaces were examined under SEM and classified as adhesive, cohesive, or mixed. Data were analyzed using two-way analysis of variance, Tukey post hoc test, and Spearman correlation (α = 0.05).
Results
In TE mode, SBU demonstrated the highest μSBS (p < 0.001), whereas no significant differences were observed among adhesives in SE mode (p > 0.05). SEM analysis revealed adhesive failures as interfacial fractures, cohesive failures with beach marks, and mixed failures involving crack propagation through both dentin and composite. Adhesive failures correlated negatively with μSBS (r_s = –0.77), while mixed failures correlated positively (r_s = 0.81).
Conclusions
Both the etching strategy and adhesive formulation significantly affect bond strength and fracture behavior. Fractographic SEM analysis provides critical insights into the mechanical reliability of UAs and informs their clinical application.

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Physicochemical characterization of two bulk fill composites at different depths: Guillermo Grazioli, Carlos Enrique Cuevas-Suárez, Leina Nakanishi, Alejandro Francia, Rafael Ratto de Moraes; Restor Dent Endod 2021;46(3):e39. Published online July 5, 2021; DOI: https://doi.org/10.5395/rde.2021.46.e39

Abstract PDF PubReader ePub

Objectives

This study analyzed the physical-chemical behavior of 2 bulk fill resin composites (BFCs; Filtek Bulk Fill [FBF], and Tetric-N-Ceram Bulk Fill [TBF]) used in 2- and 4-mm increments and compared them with a conventional resin composite (Filtek Z250).

Materials and Methods

Flexural strength and elastic modulus were evaluated by using a 3-point bending test. Knoop hardness was measured at depth areas 0–1, 1–2, 2–3, and 3–4 mm. The translucency parameter was measured using an optical spectrophotometer. Real-time polymerization kinetics was analyzed using Fourier transform infrared spectroscopy.

Results

Flexural strength was similar among the materials, while TBF showed lower elastic modulus (Z250: 6.6 ± 1.3, FBF: 6.4 ± 0.9, TBF: 4.3 ± 1.3). The hardness of Z250 was similar only between 0–1 mm and 1–2 mm. Both BFCs had similar hardness until 2–3 mm, and showed significant decreases at 3–4 mm (FBF: 33.45 ± 1.95 at 0–1 mm to 23.19 ± 4.32 at 3–4 mm, TBF: 23.17 ± 2.51 at 0–1 mm to 15.11 ± 1.94 at 3–4 mm). The BFCs showed higher translucency than Z250. The polymerization kinetics of all the materials were similar at 2-mm increments. At 4-mm, only TBF had a similar degree of conversion compared with 2 mm.

Conclusions

The BFCs tested had similar performance compared to the conventional composite when used in up to 2-mm increments. When the increment was thicker, the BFCs were properly polymerized only up to 3 mm.

Citations

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Microhardness According to Surface, Distance and Time of Photopolymerization of a Bulk-Fill Resin: In Vitro Study
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Odovtos - International Journal of Dental Sciences.2026; 1(1): 384. CrossRef
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Polymers.2023; 15(8): 1847. CrossRef
The Microhardness and Surface Roughness Assessment of Bulk-Fill Resin Composites Treated with and without the Application of an Oxygen-Inhibited Layer and a Polishing System: An In Vitro Study
Ann Carrillo-Marcos, Giuliany Salazar-Correa, Leonor Castro-Ramirez, Marysela Ladera-Castañeda, Carlos López-Gurreonero, Hernán Cachay-Criado, Ana Aliaga-Mariñas, Alberto Cornejo-Pinto, Luis Cervantes-Ganoza, César Félix Cayo-Rojas
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