Table 2. Comparison of Mean Values Before and After the Treatment Within the Same Group Regarding the Dentinal Tubules number (paired t-test) .

Group	Time	Mean	SD	Difference		t	P
				Mean	SD
Control	Before	21.20	5.76	0	0	Not computed
	After	21.20	5.76
Eggshell NPs only	Before	21.80	2.59	19.60	2.51	17.46	0.000*
	After	2.20	0.84
Seashell NPs only	Before	27.40	4.34	24.00	4.36	12.31	0.000*
	After	3.40	2.07
Eggshell NPS + Nd:YAG laser	Before	22.20	2.95	20.60	3.36	13.70	0.000*
	After	1.60	1.52
Seashell NPs + Nd:YAG laser	Before	25.20	2.77	23.40	2.88	18.16	0.000*
	After	1.80	1.92

Significance level P ≤ 0.05, *Significant.