. 2019 Mar 22;19:49. doi: 10.1186/s12903-019-0739-z

Table 2.

Elemental composition of different tooth tissues. Values are the mean ± SD. The number of images used in each analysis is given in parentheses

Parameter	Darker area (5)	Brighter area (5)	Dentin (5)	Enamel (5)
Carbon (%)	78.81 ± 3.10^b,d	29.60 ± 1.39^a,c,d	79.31 ± 1.76^b,d	14.21 ± 0.95^a,b,c
Oxygen (%)	10.94 ± 2.42^b,d	16.75 ± 0.26^a,c	10.14 ± 0.61^b,d	18.75 ± 0.95^a,c
Phosphorus (%)	3.77 ± 1.01^b,d	18.98 ± 0.30^a,c,d	4.32 ± 0.88^b,d	23.77 ± 0.47^a,b,c
Calcium (%)	5.25 ± 1.60^b,d	33.36 ± 1.39^a,c,d	6.49 ± 1.69^b,d	42.56 ± 0.84^a,b,c
C:O ratio (%)	7.49 ± 1.61^b,d	1.77 ± 0.10^a,c	7.74 ± 0.32^b,d	0.76 ± 0.06^a,c
Ca:P ratio	1.42 ± 0.32^b,d	1.76 ± 0.08^a	1.49 ± 0.14	1.79 ± 0.04^a

The statistical significance of differences between tooth tissues was analyzed by one-way ANOVA followed by Tukey’s post hoc test

^asignificantly different from the darker area

^bsignificantly different from the brighter area

^csignificantly different from the dentin

^dsignificantly different from the enamel

Differences were considered significant at P ≤ 0.05