Effect of silanization of poly (urea-formaldehyde) microcapsules on the flexural strength and self-healing efficiency of an experimental self-healing dental resin composite (An in-vitro study).

OBJECTIVES: This study investigated the impact of using γ-methacryloxypropyl trimethoxy silane (MPS) for surface silanization of poly (urea-formaldehyde) (PUF) microcapsules which enclose a healing liquid of "triethylene glycol dimethacrylate (TEGDMA) and N,N dihydroxyethyl-p-toluidine (DHEPT)" on some mechanical properties of an experimental dental composite as well as its self-healing efficiency. METHODS: Synthesis of PUF microcapsules was done via in situ polymerization, followed by silanization with MPS silane. Silanized and non-silanized microcapsules were incorporated into a composite containing 30% polymer matrix and 70% fillers at different weight percentages (0%, 5%, 7.5% and 10%). The composite strength and elastic modulus were evaluated by Flexural testing. Fracture toughness KIc and self-healing efficiency were assessed by utilizing the "single edge notched beam" method. RESULTS: Flexural strength of all groups containing silanized microcapsules was non-significantly different from control group without microcapsules. However, in contrast to control group, all groups containing non-silanized microcapsules displayed considerably decreased flexural strength. Adding silanized and non-silanized microcapsules didn't show a significant change in the KIc-virgin. The silanized microcapsules' groups achieved a self-healing efficiency of about 49-77% recovery in KIc-virgin compared to 38-69% for their non-silanized counterparts. SIGNIFICANCE: In order to increase the interfacial adhesion with the polymer matrix, improve the mechanical properties, and increase the efficiency of self-healing of dental resin composite, PUF microcapsules were silanized for the first time in the dental field using MPS silane. This innovative silanized microcapsule-containing self-healing composite may hold promise for repairing the damage caused by restorative cracks and extending their service life.

Evaluation of the pH, calcium ion release, and antibacterial effect of a premixed bioceramic endodontic sealer.

This study sought to compare a bioceramic sealer (TotalFill) and a calcium hydroxide (Ca[OH]2) sealer (Sealapex) in terms of their pH, calcium ion (Ca²âº) release, and antibacterial effect against Enterococcus faecalis bacteria. For the pH and Ca²âº release tests, 20 polyethylene tubes (10 mm in height and 1 mm in internal diameter) were filled with the appropriate sealer (n = 10 per sealer), immersed in glass flasks each containing 10 mL of deionized water, and stored in an incubator at 37°C. The water was changed after 1, 7, 28, and 90 days. At each water change, the eluates were measured with an advanced electrochemistry meter to determine the pH and with a flame atomic absorption spectrometer to determine the Ca²âº release. The antibacterial effect was measured using the turbidimetry-based direct contact test in which the wells of a microtiter plate were coated with a thin, even layer of freshly prepared sealer (10 wells per sealer), which was allowed to set before application of a suspension of E faecalis. Control wells were obtained by placing an identical bacterial suspension in 10 uncoated wells. The optical density of the sealer and control groups was measured immediately and 1, 3, and 7 days after sealer preparation. Data were analyzed for normality with the Shapiro-Wilk and Kolmogorov-Smirnov tests. Two-way analysis of variance (ANOVA), Student t test, and 1-way ANOVA with Tukey post hoc tests were all utilized with a significance level of P < 0.05. TotalFill maintained significantly higher pH and Ca²âº release levels than Sealapex at all evaluation times (P < 0.05). Both sealers demonstrated significantly greater antibacterial effect (lower optical density) than the control group; however, TotalFill resulted in significantly lower optical density values than Sealapex (P < 0.05). TotalFill bioceramic sealer demonstrated superior Ca(OH)2-related properties compared to Sealapex Ca(OH)2 sealer.