请教一下曹老师,Decreasing in the depth of caries lesion was notified by polarized-light micrographs as applying either nano-hydroxyapatite toothpaste or nano-hydroxyapatite gel as greater than fluoride varnish, with no reduction in the depth for untreated group.
如何理解句中as applying either nano-hydroxyapatite toothpaste or nano-hydroxyapatite gel as greater than fluoride varnish的结构?这里的两个as分别做什么成分?表示何种含义?