Abstract
Our study aimed to synthesize and compare the mechanical properties and dentin interaction of two adhesives; experimental adhesive (EA) and EA containing 5 wt.% calcium fluoride (CaF2) nano-crystals (CaF2 adhesive-CAFA). CaF2 nano-crystals were synthesized by reacting two solutions (containing calcium and fluoride) in a glass chamber using a heated air system. The EA was produced using a mix of monomers, photo-initiators, camphorquinone, and electron initiators. The synthesized CaF2 nano-crystals were centrifuged to guarantee that inside the adhesive there is homogenized dispersion of the filler particles. Their integration in the EA yielded two groups; Gp-1: EA (without CaF2, control) and Gp-2: (5 wt.% CaF2 containing adhesive, CAFA). Sixty teeth were prepared and set to form bonded specimens using the two adhesives. The CaF2 nano-crystals were irregularly shaped with an average particle size of 30–200 nm. The highest μTBS values were obtained for CAFA-non-thermocycled (NTC) samples (32.63 ± 3.15), followed by EA-NTC (31.80 ± 3.75) specimens. On thermocycling (TC), both adhesive groups presented lower μTBS values (CAFA-TC: 29.47 ± 3.33 and EA-TC: 24.04 ± 3.69). Hybrid layer (HL) formation and resin tags of varying depths were perceived for both adhesive groups. The EDX analysis demonstrated the presence of carbon (C), silica (Si), calcium (Ca), and fluoride (F) for CAFA group. Micro-Raman spectroscopy revealed distinct peaks for CaF2 nano-crystals. The CAFA group presented the greatest DC. The addition of CaF2 nano-crystals in the adhesive caused improved bond μTBS and DC. The incorporation also demonstrated suitable dentin interaction, depicted by appropriate HL and resin tag development.
Highlights
Dental caries is a widespread oral disease, with a prevalence of over 50% reported in some countries [1,2]
The study results indicated enhanced μTBS and DC, and suitable dentin interaction of CaF2 containing adhesive
CaF2 nano-crystals could serve as a pool of slowly releasing calcium and fluoride ions that could be used to remineralize tooth structure [30]
Summary
Dental caries is a widespread oral disease, with a prevalence of over 50% reported in some countries [1,2]. Carious lesions that cannot be naturally reversed are restored with restorative materials, including glass-ionomer cement (GICs), amalgam, and dental resin composites [3]. The clinical success of restoration is hugely reliant on dentin adhesives’ properties as adhesion forms an intimate bond between the resin and tooth’s hard tissue [9]. The integration of fillers could improve various adhesive properties, improving the longevity of the composite restorations [14]. One such bioactive fillers are calcium fluoride (CaF2 )
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