Magnetic motion of superparamagnetic iron oxide nanoparticles- loaded dental adhesives: physicochemical/biological properties, and dentin bonding performance studied through the tooth pulpal pressure model.

The limited durability of dentin bonding harshly shortens the lifespan of resin composites restorations. The controlled, dynamic movement of materials through non-contacting forces provides exciting opportunities in adhesive dentistry. We, herein, describe comprehensive investigations of a new dental adhesive with superparamagnetic iron oxide nanoparticles (SPIONs) sensitive to magnetic fields for bonding optimization. This contribution outlines a roadmap of (1) designing and tuning of an adhesive formulation containing SPIONs to enhance penetrability into etched dentin guided by magnetic-field; (2) employing a clinically relevant model of simulated hydrostatic pulpal pressure on the microtensile bond to dentin; and (3) investigating a potential antibacterial effect of the formulated adhesives, and their biocompatibility. SPION-concentration-dependency chemical and mechanical behavior was shown via the degree of conversion, ultimate tensile strength, and micro shear bond strength to dentin. The effects of SPIONs carried on a dental adhesive on the bonding strength to dentin are studied in depth by combining experiments with in vitro simulated model. The results show that under the guided magnetic field, 0.07 wt.% of SPIONs-doped adhesive increased the bond strength that surpasses the reduction caused by hydrostatic pulpal pressure. Using a magnetic guide workflow during the bonding procedures, SPIONs-doped adhesives improved dentin's adhesion without changing adhesives' physicochemical properties. This outcome addresses the key challenge of poor resin infiltration of dentin's conventional total etching during the bonding procedure. The real-time magnetic motion of dental adhesives may open new paths to enhance resin-based restorations' longevity. STATEMENT OF SIGNIFICANCE: In this study, dental adhesives containing superparamagnetic iron oxide nanoparticles (SPIONs) were developed to enhance penetrability into dentin guided by a magnetic field. The adhesives were screened for physical, chemical, antibacterial properties, and cytotoxicity. For the first time, simulated pulpal pressure was used concurrently with the magnetic field to simulate a clinical setting. This approach showed that it is feasible to overcome pulpal pressure jeopardization on bond strength when SPIONs and a magnetic field are applied. The magnetic-responsive adhesives had great potential to improve bond strength, opening new paths to enhance resin-based restorations' longevity without affecting adhesives' biological properties. The use of magnetic-responsive particles and magnetically assisted motion is a promising strategy to improve the sealing ability of dental adhesives.

Efficacy of color discrimination tests used in dentistry.

OBJECTIVE: To evaluate the efficacy of visual discrimination tests used for color research in dentistry. MATERIALS AND METHODS: Volunteers (N = 120) were divided in three groups of observers (n = 40; gender-balanced): S-dental students; D-dentists; and L-laypersons. Two general color discrimination tests (I-Ishihara and FM-Farnsworth-Munsell 100 Hue) and the test of color discrimination competency in dentistry using the VITA Classical shade guide (VC) were performed and data were recorded according to manufacturers' or literature recommendations. Data were statistically analyzed using Mann-Whitney U test for the gender influence and Kruskal-Wallis test for the observer influence, and Bonferroni as post-hoc test (α = 0.05). Pearson (α = 0.05) was used to examine the correlation among visual tests (I, FM, and VC). RESULTS: Observers and visual tests were not influenced by gender (P > .05). Different observer groups had no influence on I test (P > .05). S and D showed similar level of color perception using FM and VC (P > .05), but these observers showed greater color perception than L (P ≤ .05). FM and VC also showed significant correlation (P ≤ .05) for the overall D observers (r = -0.362), male D (r = -0.594) and female S (r = -0.457). CONCLUSION: Observer experience significantly influenced on color perception, irrespective of gender. FM test showed greater correlation to color correspondence in dentistry (VC) than I test. CLINICAL SIGNIFICANCE: Observer experience is more relevant than gender for the color selection process in dentistry. Considering the visual discrimination tests for color research in dentistry, the Farnsworth-Munsell 100 Hue test seems to be more efficacious than the Ishihara test.