Purpose: To evaluate the response of human peri-implant soft tissue (PIST) on different healing
abutment materials 24 hours after positioning, by assessing the expression of genes related to the
early connective tissue wound healing response. Materials and Methods: Experimental abutments of
4 different materials (A): grade 4 titanium, (B) grade 5 titanium, (C) zirconia and (D) PEEK, were
mounted on installed implants in 5 patients, four different abutments each. Before implant
placement, a gingival biopsy (control-CT) was obtained using a 2 mm diameter punch (T0). After
24 hours (T24), PIST biopsies were collected using a specifically designed custom-made cutting
device. Real-time PCR was performed to analyze the expression of the following genes: COL-I,
COL-III, MMP-1, TIMP-1,TGF-b1, FN, ITGA4, ITGA5, ITGB1, RAC-1, COL-IV, aSMA, IL-6
and CXCL-1. Results: Gene expression analysis showed some differences between CT and
abutment of different materials, although no significant differences were detected comparing the
experimental groups. COL-I was significantly down-regulated in groups A and C compared to CT.
MMP-1 and TIMP-1 increased in all the experimental groups, although at a lower extent in group
A. FN, RAC-1, COL-IV and aSMA were down-regulated, especially in group A, in which CXCL-1
and IL-6 showed the lowest expression. Conclusions: The results of grade 4 titanium and zirconia
abutments seem to be promising, since a lower expression of genes related with inflammation,
myofibroblasts activation and ECM remodeling was observed when compared with grade 5
titanium and PEEK, without triggering a pro-fibrotic response in the early phases of PIST repair.
Keywords: gene expression analysis, PEEK, peri-implant soft tissue, titanium, zirconia, wound healing