Multiscale in-vitro analysis of photo-activated riboflavin incorporated in an experimental universal adhesive

Fu C 1 , Deng S 1 , Koneski I 1 , Awad MM 2 , Akram Z 1 , Matinlinna J 3 Show all authors , Pichika MR 4 , Daood U 5 , Fawzy AS 6

Affiliations 

  • 1 UWA Dental School, University of Western Australia, 17 Monash Avenue, Nedlands, WA, 6009, Australia
  • 2 Department of Conservative Dental Sciences, College of Dentistry, Prince Sattam Bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia
  • 3 Dental Materials Science, Applied Oral Sciences, Faculty of Dentistry, The University of Hong Kong, 34 Hospital Road, Sai Ying Pun, Hong Kong SAR, China
  • 4 Department of Pharmaceutical Chemistry, School of Pharmacy, International Medical University Kuala Lumpur, 126, Jalan Jalil Perkasa 19, Bukit Jalil, 57000, Bukit Jalil, Wilayah Persekutuan Kuala Lumpur, Malaysia
  • 5 Clinical Dentistry, Restorative Division, Faculty of Dentistry, International Medical University Kuala Lumpur, Bukit Jalil, 57000, Bukit Jalil, Kuala Lumpur, Malaysia. Electronic address: umerdaood@imu.edu.my
  • 6 UWA Dental School, University of Western Australia, 17 Monash Avenue, Nedlands, WA, 6009, Australia. Electronic address: amr.fawzy@uwa.edu.au
J Mech Behav Biomed Mater, 2020 12;112:104082.
PMID: 32979607 DOI: 10.1016/j.jmbbm.2020.104082

Abstract

OBJECTIVE: To investigate the effect of blue light photoactivated riboflavin modified universal adhesives on dentin collagen biodegradation resistance, dentin apparent elastic modulus, and resin-dentin bond strength with interfacial morphology.

METHODS: Dentin slabs were treated with 0.1% riboflavin-5-phosphate modified (powder added slowly while shaking and then sonicated to enhance the dispersion process) Universal Adhesive Scotch Bond and Zipbond™ along with control (non-modified) and experimental adhesives, photoactivated with blue light for 20s. Hydroxyproline (HYP) release was assessed after 1-week storage. Elastic-modulus testing was evaluated using universal testing machine at 24 h. Resin-dentin interfacial morphology was assessed with scanning electron-microscope, after 6-month storage. 0.1% rhodamine dye was added into each adhesive and analyzed using CLSM. Detection of free amino groups was carried out using ninhydrin and considered directly proportional to optical absorbance. Collagen molecular confirmation was determined using spectropolarimeter to evaluate and assess CD spectra. For molecular docking studies with riboflavin (PDB ID file), the binding pocket was selected with larger SiteScore and DScore using Schrodinger PB software. After curing, Raman shifts in Amide regions were obtained at 8 μm levels. Data were analyzed using Two-way analysis of variance (ANOVA, p ≤ 0.05) and Tukey-Kramer multiple comparison post hoc tests.

RESULTS: At baseline, bond strength reduced significantly (p ≤ 0.05) in control specimens. However, at 6 months' storage, UVA Zipbond™ had significantly higher μTBS. Resin was able to diffuse through the porous demineralized dentin creating adequate hybrid layers in both 0.1%RF modified adhesives in CLSM images. In riboflavin groups, hybrid layer and resin tags were more pronounced. The circular dichroism spectrum showed negative peaks for riboflavin adhesive specimens. Best fitted poses adopted by riboflavin compound are docked with MMP-2 and -9 proteases. Amide bands and CH2 peaks followed the trend of being lowest for control UA Scotch bond adhesive specimens and increasing in Amides, proline, and CH2 intensities in 0.1%RF modified adhesive specimens. All 0.1%RF application groups showed statistically significant (p 

* Title and MeSH Headings from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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