BACKGROUND:Subepithelial connective tissue grafts are generally considered as the gold standard for soft tissue augmentation.However,it needs a second surgical site,which will prolong the surgical time and increase patients'pain. OBJECTIVE:To compare the histological and thickness changes of attached gingiva following grafting with different soft tissue substitutes in the labial region of the cuspids. METHODS:In three Beagle dogs,attached gingival augmentation was performed with double-layer allogeneic acellular dermal matrix membrane(AADM),bovine-derived acellular dermal matrices(BADM)combined with concentrated growth factor membrane or BADM combined with collagen sponge.Thickness of attached gingiva was measured before augmentation,and 1,2,3,and 4 months after augmentation.Histological analyses were performed after 4 months. RESULTS AND CONCLUSION:The mean values of attached gingival thickness and attached gingival thickness augmentation were higher in the double-layer AADM group than in the other two groups(all P<0.05)from the 1st to 4th month after surgery.At 1 month after surgery,the attached gingival thickness of the three groups increased significantly and then decreased.At 3 months after surgery,the BADM combined with collagen sponge group and the BADM combined with concentrated growth factor membrane group showed no significant difference in the attached gingival thickness of the graft area compared with that before surgery(P>0.05).At 4 months after surgery,the mean value of attached gingival thickness in the double-layer AADM group was still significantly increased compared with that before surgery(P<0.05).The value of attached gingival thickness was highest in the double-layer AADM group,followed by the BADM combined with collagen sponge group,and the lowest in the BADM combined with concentrated growth factor membrane group at 1-4 months after surgery.Histological analyses revealed that AADM was well integrated with the host gingival tissue,and new fibrous connective tissue and fibroblasts grew into the AADM.But the grafts in the other two groups were absorbed and the augmentation area was remodeled into a structure consistent with the surrounding host tissue.To conclude,AADM is superior to BADM combined with concentrated growth factor and BADM combined with collagen sponge with regard to gingival augmentation.