Objectives: The aim of this pilot study was to estimate the sample size for an ex-vivo study evaluating the influence of application time on penetration the depth of a low viscosity resin (infiltrant) into proximal caries lesions in primary molars.
Methods: Ethical approval was obtained and parents gave informed consent. Fifteen primary molars with proximal caries lesion diagnosed radiographically with radiolucencies restricted to the enamel (E1, E2) or in the outer third of dentine (D1) and expected to exfoliate within the next 6 months were selected. Proximal lesions were treated with an infiltrant (Icon; DMG) using three application times (60s, 180s, 300s) in vivo. After treatment, teeth were extracted and thin sections were prepared. Lesion depth was analyzed using polarization light microscopy. Subsequently, specimens were etched with 5% HCl (30s) and penetration depth was analyzed using backscattered scanning electron microscopy.
Results: Sample size calculation based on mean percentage penetration depths revealed that 33, 14, and 94 specimens are needed to obtain significant differences between 60s/180s, 60s/300s, and 180/s300s application time, respectively (α=0.05;1-β=0.8; chi-square test).
Time (s) | N | median(25th;75th percentile) [µm] | ||
Lesion depth | Penetration depth | %Penetration depth | ||
60 | 4 | 487(182;644) | 283(128;511) | 74(49;93) |
180 | 6 | 642(472;757) | 481(341;580) | 82(71;85) |
300 | 4 | 616(525;874) | 520(376;795) | 91(66;93) |
No significant differences between groups within all columns were observed (Kruskal-Wallis test; p>0.05).
Conclusion: Even after a relatively short application time of an infiltrant (1 min), shallow lesions in primary molars seem to be thoroughly infiltrated. Sample size calculation revealed that more than 30 teeth are needed, to show significant different percentage penetration depths between clinically relevant application times.
Supported by the Deutsche Forschungsgemeinschaft (PA 1508/1-2). HML and SP receive a research grant and royalties, VS receives a research grant from DMG, Hamburg.