a, b Sealant layer abatement by mean OpalSeal-scores in sub-groups with positive or negative API scores indicate a significant increase in abatement from front teeth to posterior teeth (see also Table 1). On average, well brushed (left) and non-brushed (right) anterior teeth undercut the 50% sealant presevation (score “1) at T3 (week 14). The slightly better sealant preservation before and after T3 in API-positive teeth was globally not significant. On average, re-application of sealant can therefore be expected to be necessary after 3.5 months in active treatment. c, d Percentages of teeth with sealant scores higher than 0. At T5, approximately 50% of front teeth #1-#4 with positive API had at T5 a sealant score higher than 0, while in the case of well brushed teeth percentages were slightly lower. See also Table 3 for details.