Table 2.

Kappa values, inter and intra-rater. O1 to O4: observers. Results are linearly weighted kappa

Modality		Histological state of the surface
Inter-rater		Sound		Enamel		Dentine		Total
		k ± S.E.	Sig.	k ± S.E.	Sig.	k ± S.E.	Sig.	k ± S.E.	Sig.
O1-O2	tooth	0.41 ± 0.16	*	0.33 ± 0.10	**	0.65 ± 0.07	***	0.64 ± 0.04	***
O1-O2	photo	0.55 ± 0.12	**	0.26 ± .14	*	0.46 ± 0.10	***	0.57 ± 0.05	***
O1-O3	photo	0.44 ± 0.12	*	0.02 ± 0.14	ns	0.17 ± 0.12	ns	0.39 ± 0.06	***
O1-O4	photo	0.30 ± 0.13	*	0.20 ± 0.13	ns	0.33 ± 0.11	**	0.44 ± 0.05	***
O2-O3	photo	0.53 ± 0.12	**	0.31 ± 0.11	*	0.32 ± 0.12	**	0.52 ± 0.05	***
O2-O4	photo	0.51 ± 0.12	**	0.25 ± 0.10	ns	0.52 ± 0.10	***	0.58 ± 0.05	***
O3-O4	photo	0.40 ± 0.14	**	0.15 ± 0.12	ns	0.26 ± 0.12	*	0.42 ± 0.06	***
Intra-rater		Sound		Enamel		Dentine		total
O1	tooth	0.82 ± 0.07	***	0.54 ± 0.09	***	0.86 ± 0.06	***	0.85 ± 0.03	***
O2	tooth	0.54 ± 0.12	*	0.49 ± 0.09	**	0.75 ± 0.06	***	0.74 ± 0.04	***
O1	photo	0.62 ± 0.15	**	0.54 ± 0.11	***	0.67 ± 0.10	***	0.74 ± 0.04	***
O2	photo	0.50 ± 0.11	**	0.34 ± 0.14	*	0.53 ± 0.10	***	0.61 ± 0.05	***
O3	photo	0.44 ± 0.16	*	0.29 ± 0.12	*	0.81 ± 0.07	***	0.59 ± 0.05	***
O4	photo	0.82 ± 0.07	***	0.57 ± 0.15	***	0.73 ± 0.06	***	0.78 ± 0.04	***

Significance levels are given as follows: ns: not significant (p > 0.05), * p < 0.05 > 0.01, **p < 0.01.0.001, ***p < 0.001