A comparison of Terahertz Pulsed Imaging with Transverse Microradiography and Microhardness to measure mineral changes in enamel after treatment with fluoride dentifrices

摘要

The aim of this study was to determine the ability of Terahertz Pulsed Imaging (TPI) to measure mineral changes in enamel lesions during de/remineralisation studies. A comparison was made between transverse microradiography (TMR) and microhardness measurements. Artificial lesions were formed in bovine enamel using a solution of 0.1 M lactic acid (pH 5.0) containing 0.2% Carbopol C907 and 50% saturated with hydroxyapatite. The 20 day experimental protocol consisted of four, one-minute treatment periods with dentifrices containing 10, 675, 1385 and 2700ppm fluoride, a 4 h/day acid challenge, and for the remaining time specimens were stored in a 50:50 pooled human / artificial saliva mixture. Terahertz images were generated by positioning the specimens at the focus of the beam and raster scanning the optics to collect the reflections from the air / enamel (AEI) and lesion / enamel (LEI) interface. Significant differences were observed in the intensity change from baseline of the AEI and LEI reflections upon treatment with the four dentifrices. A linear correlation was observed between ΔAEI vs ΔVHN (r~2 = 0.997), ΔAEI vs ΔKHN (r~2 =0.964), ΔII (ratio of LEI to AEI) vs ΔΔZ (r~2 =0.875) and ΔLEI vs ΔΔZ (r~2 =0.870). Statistically significant correlations (p<0.05 Pearson correlation coefficient) were also found between the TPI and microhardness / microradiography data. This study has demonstrated that TPI is a useful technology to measure in vitro (and possibly in situ) mineral changes in enamel and is sufficiently sensitive to discriminate between the levels of remineralization produced by the different dentifrices.