The use of photoreactive riboflavin and blue light irradiation in improving dentin bonding

Abstract

For contemporary dentin bonding systems problems are encountered such as collagen collapse incomplete infiltration of resin monomer and the collagen hydrolysis by the matrix metalloproteinase (MMPs) Recently the riboflavin (RF) has been approved to improve dentin bond through enhancing collagen crosslinking under UVA irradiation However the blue light is commonly used in dental clinic The purpose of this study was to evaluate the use of RF combining blue light irradiation as a collagen cross-linker in improving dentin bonding Extracted human molars were collected and occlusal enamel was removed The exposed dentin was acid-etched then divided into six experimental groups: Control no treatment; RF0 1UV2 0 1% RF treatment followed by 2-minute UVA irradiation; RF0 1BL1 and RF0 1BL2 0 1% RF followed by 1- or 2-minute blue light irradiation; RF1BL1and RF1BL2 1% RF followed by 1- or 2- minute blue light irradiation The dentin surfaces received bonding treatment and composite restorations These teeth received the microtensile bond strength (?TBS) test at initial stage after storage for 24 hours and after enzymatic degradation In addition the fracture modes of these microbeams were evaluated The morphology of hybrid layers was also evaluated by removing dentin with phosphoric acid and NaOCl A nanoindentation test was used for the mechanical properties of treated dentin The teeth were also powdered and demineralized to extract collagen and received zymography assay of MMP2 activity For the initial μTBS RF0 1UV2 and RF0 1BL1 showed the highest values the other RFBL groups showed comparable μTBS as control After enzyme degradation all groups showed decreased but the same order of μTBS All RF treated groups presented thicker hybrid layers than control with RF0 1BL1 showed the thickest one The nanoindentation and zymography assay showed the highest hardness and MMP inhibition in RF0 1BL2 and RF1BL2 RF0 1UV2 and RF0 1BL1 showed mild improvement than the control With these results RF0 1BL1 showed comparable bond strength as RF0 1UV2 by constructing the thickest hybrid layer 2-min BL irradiation increased mechanical properties and MMP inhibition but they caused hybrid layer condensation and thus affected the dentin bonding Accordingly the protocol using RF and BL as a collagen crosslinker need an appropriate protocol while RF0 1BL1 improve dentin bonding and durability

Date of Award	2014 Aug 27
Original language	English
Supervisor	Shu-Fen Chuang (Supervisor)