Table 2.

Proportion benefiting from the intervention and number needed to treat in the two included studies

Study	Intervention (test group)	Caries arrest rate in test group	Caries arrest rate in control group	Proportion benefiting from intervention	Number needed to treat
		P (A)	P (B)	P(C) = P(A) - P(B)	NNT = 1/P(C)
Chu et al. 2002 [13]	38% SDF + excavation	0.65	0.34	0.31	3.2
	38% SDF	0.65	0.34	0.31	3.2
	5% NaF + excavation	0.38	0.34	0.04	25
	5% NaF	0.44	0.34	0.10	10
Lo et al. 1998 [9]	Brushing with fluoridated toothpaste	0.28	0.12	0.16	6.3