Evaluation of experimental resin infiltrant containing nanohydroxyapatite on color stability and microhardness in demineralized enamel.

OBJECTIVE: The aim of the study was to evaluate the effect of the addition of 10% nanohydroxyapatite in an experimental resin infiltrant on color stability and mineral loss. MATERIAL AND METHODS: Bovine enamel blocks were randomized into five groups (n = 27/group): SE (sound enamel); ICL (initial caries lesion); I (Icon(R)); E (experimental infiltrant); EH (experimental infiltrant containing 10% nanohydroxyapatite). Color evaluation (n = 15) was performed and CIEL*a*b* values were obtained at points T(0) (baseline), T(1) (14 days immersed on coffee solution), and T(2) (28 days immersed) and data were calculated ∆E(00), ∆W(ID), ∆L*, ∆a*, and ∆b*. Cross-sectional microhardness (n = 12) was performed and lesion area (∆S) was calculated. Images were obtained with polarized light optical microscopy at 40 x magnification (n = 5). RESULTS: In color stability results, there was significant difference between time (14 and 28 days); ICL demonstrated significant difference among treated groups in all measures (∆L*, ∆a*, ∆b*, ∆E(00), ∆W(ID)) regardless of time; I and E demonstrated similar behavior on those measures and EH differed from I in ∆L*. For ∆S, ICL group showed a significant difference compared to I and EH groups, but did not differ from E. CONCLUSION: The nanohydroxyapatite incorporation suggested an effective mineral recovery on initial caries lesion in depth; however, it showed high color variation, such as Icon. In terms of ∆S, I and EH had lower mineral loss, suggesting a reinforcement on initial caries lesion. CLINICAL RELEVANCE: Commercial and experimental infiltrants containing nanohydroxyapatite present low color stability and might reinforce mineral in initial caries lesion.