Influence of application frequency of an infiltrant on enamel lesions

Objectives: The aim of this study was to evaluate the application frequency of two experimental low viscous resins (infiltrants) on lesion progression and micro hardness of resin infiltrated artificial enamel lesions in vitro. Methods: Twenty-six bovine enamel specimens were demineralized (pH 4.95; 50 days) to prepare three windows of caries-like lesions. Two of these windows were etched with phosphoric acid (37%) for 5s, the third one served as control. Both etched lesion parts were treated with either one of two infiltrants (A: BisGMA 25%, TEGDMA 75%; B: BisGMA 20%, TEGDMA 60%, ethanol 20%). The respective infiltrant was applied onto both windows (10s), excessive material was removed and the material light cured (60s). This procedure was repeated on one of the two windows of each specimen. Subsequently, lesions were cut in two halves, one being stored in the demineralizing solution for another 50 days, the other serving as baseline control. Lesion depths and mineral losses were evaluated by microradiography (n=13). Vickers hardness numbers (VHN) were assessed on cut surfaces 50µm below the surface (n=9). Results: Control lesions of the baseline halves showed a mean (SD) mineral loss of 15,205 (1,820) vol%µm and a lesion depth of 357 (32) µm. Irrespective of the material control lesions as well as those being infiltrated once progressed significantly (t test, p<0.05), whereas those being infiltrated twice revealed no significant progression (p>0.05). Lesions being infiltrated twice [48 (17)] showed significantly higher VHN compared with those being infiltrated once [37 (16)], which were again significantly higher than those of the control lesions [7 (5)] (p<0.05). No significant differences in micro hardness could be observed between the materials (p>0.05). Conclusion: Twice infiltration results in a hampered lesion progression and a gain in micro hardness in artificial lesions.

This study was supported by the Deutschen Forschungsgemeinschaft (PA 1508/1-1).