A new hand-held optical reflectometer to measure enamel erosion: correlation with surface hardness and calcium release

In the present study, the surface reflection intensity (SRI) was measured from enamel with different induced erosion degrees using a hand-held pen-size reflectometer (Hand-Held) and a Table-Top reflectometer. To validate the Hand-Held reflectometer, we correlated its optical signals with the change of surface microhardness (SMH), and amount of calcium released from the enamel samples during erosion. We used 124 tooth enamel specimens that were exposed to an erosive challenge of either 1, 2, 4, 6, 8, or 10 minutes. SRI and SMH were measured before and after the erosive challenge and we also measured the amount of calcium released to the citric acid. Relative SRI loss (rSRI(loss)) and relative SMH loss (rSMH(loss)) were calculated. rSRI(loss) from the Hand-Held and the Table-Top reflectometers were similar and significantly correlated to rSMH(loss) and calcium release. The regression analyses showed a significant association between rSRI(loss) from both reflectometers and rSMH(loss) and calcium, showing that both reflectometers can be used to measure erosive demineralization of enamel. The Hand-Held reflectometer is capable of assessing in vitro erosion, correlating to other commonly used methods. It is small, easy to handle and provides fast measurement, being a possible candidate to measure erosion in clinical studies.