Micro‐computed tomography assessment of root dentin around fluoride‐releasing restorations after demineralization/remineralization

Abstract

Using micro-computed tomography (micro-CT), this study assessed the inhibitory effect of three different types of restorations on root-caries formation under a cariogenic challenge. Bovine-root dentin blocks with a cylindrical cavity were divided into three restoration groups: a fluoride-free self-etch adhesive and a resin composite (SE-ES); a self-etch adhesive and a resin composite with multi-ion release (FL-BF); and a glass ionomer cement (Fuji-VII). After the restorative procedures, the specimens were stored in artificial saliva for 1 d, then subjected to a demineralization solution for 4 d and a remineralization solution for 28 d. Mineral density and mean mineral loss of dentin around the restorations were measured using micro-CT. The mean mineral loss values of dentin around the restorations were highest among SE-ES restorations and lowest among Fuji-VII restorations. Fuji-VII showed the highest mineral density and the lowest mineral loss after 28 d of remineralization. The observations made by scanning electron microscopy demonstrated that Fuji-VII created the smallest outer lesion followed by FL-BF and SE-ES. Fuji-VII has a larger inhibitory effect on root caries around the restorations and enhances remineralization more effectively than either FL-BF or SE-ES. Multi-ion and fluoride release from the restorative materials may be beneficial for inhibition of root-dentin caries around the restorations.

Effect of poly (γ-glutamic acid)/tricalcium phosphate (γ-PGA/TCP) composite for dentin remineralization <i>in vitro </i>

“…MD=(Gray value×0.1834)−35.778 29) The lesion depth (LD) was defined as the distance from the immediate surface to the point where the MD was 95% of the sound tissue, and the sound dentin was set as 48 vol% mineral 30,31) . Mineral loss (ΔZ, vol% • μm) was calculated by subtracting the lesion MD value from the sound dentin MD value.…”

Micro-CT assessment of the effect of silver diammine fluoride on inhibition of root dentin demineralization

“…The specimens were rotated through 360° with 0.6° steps. The distances from the X-ray source to the detector and from the X-ray source to the specimen were 300 and 73.5 mm, respectively 23) . A brass 0.2 mm-thick filter was positioned in the beam path to cut off low-energy X-rays, to decrease any beam-hardening effects 24) .…”

“…A brass 0.2 mm-thick filter was positioned in the beam path to cut off low-energy X-rays, to decrease any beam-hardening effects 24) . A MD calibration curve was obtained by scanning three reference phantoms: two hydroxyapatite disks (0.60 and 0.80 gHAp cm −3 ) (Phantoms, S/N-1001-39, Ratoc System Engineering, Tokyo, Japan) and a pure aluminum wire (0.9 mm diameter, 1.55 gHAp cm −3 ) which were scanned using the same setup and parameters as the tooth specimens 23) . In order to avoid dehydration of the specimens, scanning was performed under 100% humidity where the specimens were put in a vial with wet cotton.…”

“…The computed tomography (CT) values were converted to MD (gHAp cm1 −3 ) using a calibration curve derived from a linear regression (R 2 >0.999) based on the phantom scans. The assessment was performed with a volume of interest (VOI) of 600×600×600 voxels at the center of the test window 23) .…”

“…The reference point of the depth axis (0 µm) in the mineral profile was set at the axial position of the sound dentin surface at the baseline. These calculations were performed by importing the MD data into a spreadsheet software package (Microsoft Excel 2016 for Windows, Microsoft, Redmond, WA, USA) 23) .…”