Specimens treated with the Sn-containing NaF dentifrice showed 6.5 m of surface loss 1.2 ( SEM ) , which was not significantly different ( P < 0.05 , Fisher LSD ) from that of a clinically proven , stabilised SnF2 positive control [ Crest ( ) Pro-Health , 1,100 ppm F as SnF2 : 3.0 m of surface loss 1.1 ( SEM ) ] .