Table 3.

Decay in tooth surfaces after intervention

	Type of decay
Variable	ND01	ND02	ND03
Study group (N)
Experimental (n = 17,060)	4.4 (746)	0.7 (116)	1.4 (231)
Control (n = 17,900)	5.1 (914)	1.0 (186)	1.7 (309)
Statistical data
χ2	10.386	13.157	7.958
P	0.001	<0.001	0.005

Data are presented as % (n).

The bold values indicated the differences between two groups were statistically significant.

Sound surfaces at baseline, which developed enamel decay, dentine decay or dentine decay close to the pulp after 3 years, were classified as ND01, ND02 or ND03, respectively.

A chi-square test was used to compare differences between the two groups (P < 0.05).