Table 4

Variable	S group	M group	GM group	S vs. M	S vs. GM	M vs. GM
Variable	Mean (SD) in mm			P-value
VBT < 1.5 mm
ΔHVC	-2.14 (0.08)	-1.27 (0.64)	-1.21 (0.26)	< 0.0001	< 0.0001^a	< 0.0001^a
ΔRW	-4.14 (0.39)	-1.24 (0.37)	-1.18 (0.52)	< 0.0001	< 0.0001^a	< 0.0001^a
VBT ≥ 1.5 mm
ΔHVC	-2.08 (0.71)	-0.42 (0.64)	-0.39 (0.26)	< 0.0001	< 0.0001^a	0.0578^b
ΔRW	-3.12 (0.58)	-0.72 (0.36)	-0.85 (0.19)	< 0.0001	< 0.0001^a	0.0593^b

^aStatistically significant at P ≤ 0.05 (Kruskal-Wallis test).
^bStatistically significant at P > 0.05 (Kruskal-Wallis test).
SD = standard deviation; ΔRW = changes in ridge width, ΔHVC = changes in height of the vestibular crest; S = spontaneous healing;
M = porcine-derived collagen membrane alone; GM = porcine-derived graft material associated with collagen membrane.