Table 1.

Treatment comparisons by day for enamel loss (μm)^*

Visit/treatment	Original scale in μm, estimated median* (SE)	Log scale, mean (SE)	Two-sided P-value
Day 5†
NaF/KNO3 dentifrice	1.83 (0.233)	0.834 (0.097)	0.0169
NaF/SnCl2 dentifrice	1.37 (0.177)	0.612 (0.096)
Day 15‡
NaF/KNO3 dentifrice	3.30 (0.379)	1.328 (0.100)	<0.0001
NaF/SnCl2 dentifrice	2.03 (0.274)	0.919 (0.099)

^*Estimated medians in μm were obtained by using the exponential function on means from the natural logarithm scale, and subtracting the normalizing constant (e^mean – 0.472). Back-transformed standard errors were estimated using the statistical delta method.

^†Day 5 variance components: subject = 0.180, residual = 0.280.

^‡Day 15 variance components: subject = 0.171, residual = 0.325.

^*Log scale = natural logarithm scale.