Table 2. Means ± SDs for surface roughness (Ra) of specimens by surface treatment protocol.

	DP	DSP	NP	NSP	P
Roughness (µm)	0.87 ± 0.11a	0.64 ± 0.10b	0.32 ± 0.06c	0.29 ± 0.07c	< .001

DP: diamond bur + polishing bur, DSP: diamond bur + stone grinding bur + polishing bur, NP: no diamond bur + polishing bur, NSP: no diamond bur + stone grinding bur + polishing bur.

Significant differences are represented by different superscript lowercase letters within a row.