Autonomous-Strengthening Adhesive Provides Hydrolysis-Resistance and Enhanced Mechanical Properties in Wet Conditions

• Published in: Molecules (Basel, Switzerland) Vol. 27; no. 17; p. 5505
• Main Authors: Ezazi, Mohammadamin, Ye, Qiang, Misra, Anil, Tamerler, Candan, Spencer, Paulette
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 27-08-2022; MDPI
• Subjects: Adhesives; Aging; Analysis; Bond strength; Composite materials; Composite Resins - chemistry; Copolymers; Demineralizing; dental adhesive; dynamic mechanical analyses; Enzymes; Free radical polymerization; Glass transition temperature; Hydrolysis; hydrolytic degradation; Investigations; Leachates; Load transfer; Materials Testing; Mechanical properties; Methacrylates - chemistry; Oral fluids; Polymerization; Polymers; self-strengthening; Sol-gel processes; sol-gel reaction; Statistical analysis; Statistical tests; Teeth; Transition temperatures; Water - chemistry; dental adhesive; dynamic mechanical analyses; hydrolytic degradation; sol-gel reaction; self-strengthening
• ISSN: 1420-3049; 1420-3049
• DOI: 10.3390/molecules27175505

The low-viscosity adhesive that is used to bond composite restorative materials to the tooth is readily damaged by acids, enzymes, and oral fluids. Bacteria infiltrate the resulting gaps at the composite/tooth interface, demineralize the tooth, and further erode the adhesive. This paper presents the preparation and characterization of a low-crosslink-density hydrophilic adhesive that capitalizes on sol-gel reactions and free-radical polymerization to resist hydrolysis and provide enhanced mechanical properties in wet environments. Polymerization behavior, water sorption, and leachates were investigated. Dynamic mechanical analyses (DMA) were conducted using water-saturated adhesives to mimic load transfer in wet conditions. Data from all tests were analyzed using appropriate statistical tests (α = 0.05). The degree of conversion was comparable for experimental and control adhesives at 88.3 and 84.3%, respectively. HEMA leachate was significantly lower for the experimental (2.9 wt%) compared to control (7.2 wt%). After 3 days of aqueous aging, the storage and rubbery moduli and the glass transition temperature of the experimental adhesive (57.5MPa, 12.8MPa, and 38.7 °C, respectively) were significantly higher than control (7.4MPa, 4.3 MPa, and 25.9 °C, respectively). The results indicated that the autonomic sol-gel reaction continues in the wet environment, leading to intrinsic reinforcement of the polymer network, improved hydrolytic stability, and enhanced mechanical properties.