Abstract
ABSTRACT. This study aimed to nondestructively evaluate sealing performance of eight one-step self-etch adhesives (1-SEAs) using optical coherence tomography (OCT). The two-step self-etch adhesive (2-SEA) served as the control. Round tapered class-I cavities (D=4 mm, H=2 mm) were prepared in bovine incisors, treated with each adhesive (n=5), and restored with a flowable resin composite. Cross-sections were obtained from each restoration using swept-source OCT with 1310-nm laser. The average percentage of the sealed interface (SI%) for each adhesive was calculated using image analysis software, considering increased signal intensity at the interface as gap. Samples were then sectioned and observed under confocal laser scanning microscope (CLSM). Significantly different SI% values were found among different adhesives (analysis of variance, Bonferroni, p<0.05). There was also a significant correlation in SI% between OCT and CLSM (p<0.0001, r=0.96). Additionally, microscopic analysis revealed that the gaps in 1-SEAs occurred not only at dentine-adhesive interfaces but also frequently at adhesive-composite interfaces. Some recent 1-SEAs could achieve reliable short-term sealing comparable to 2-SEA. OCT is a unique tool to nondestructively evaluate the sealing performance of the restoratives through the cavity, provided that cavity walls have a certain minimum inclination with respect to the beam.
Highlights
Restorative dentistry has been revolutionized with the introduction of resin-based dental adhesives, enabling bonding of biomaterials to the dental hard tissues
The axial resolution of this SS-optical coherence tomography (OCT) system in air is 11 μm, which corresponds to 7 μm within dental tissue having a refractive index of about 1.5 (Ref. 25)
The null hypothesis of the present study was rejected since one-way ANOVA analysis of the OCT data revealed significantly different SI% values among different adhesives (p < 0.05)
Summary
Restorative dentistry has been revolutionized with the introduction of resin-based dental adhesives, enabling bonding of biomaterials (mainly composites) to the dental hard tissues. The adhesives have evolved in the past decades toward complex formulations with simplified clinical procedures. Reduced technique sensitivity and short period of application procedure have made one-step self-etch adhesives (1-SEAs) more popular among dentists in recent years. The problem of postoperative sensitivity can be remarkably reduced as the smear plugs remain when 1-SEAs are applied, in vitro and clinical reports on bonding performances of 1-SEAs have indicated controversial results.[1,2,3] 1-SEAs act as a permeable membrane, facilitating water movement across the polymerized resin and leading to bond degradation over time.[4] Besides hydrophilicity, there are other important factors that contribute to the marginal integrity of 1-SEAs, for instance, operator’s
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