Characterization of oral biomarkers during early healing at augmented dental implant sites

Abstract

Aim: The aim of this study is to assess early wound healing expression of local angiogenic biomarkers following connective tissue graft (CTG) at dental implant sites.

Methods: Twenty-eight subjects with single dental implants exhibiting a soft tissue dehiscence were included and randomly treated with CTG, either with coronally advanced flap (CAF) or with tunnel technique (TUN). Peri-implant crevicular fluid (PICF) was collected at the midfacial and midlingual aspect of the implant sites at baseline and at 3, 7, 14, 30, and 90 days after the surgical intervention. The expression of angiogenin (ANG), fibroblast growth factor-2 (FGF-2), platelet-derived growth factor (PDGF), tissue inhibitor of metalloproteinases-2 (TIMP-2), and vascular endothelial growth factor (VEGF) was investigated over a period of 3 months. Patient-reported outcomes, clinical measurements, and ultrasonography scans at multiple time points were also evaluated.

Results: The longitudinal regression revealed a significant difference in the expression of VEGF and TIMP-2 between CAF- and TUN-treated sites over 3 months (p = .033 and p = .004, respectively), whereas no significant differences were observed for ANG, FGF-2 and PDGF between the two groups. At 7 days, a direct correlation was observed between ANG levels and ultrasonographic color velocity in the CAF group (p < .001) and between ANG levels and ultrasonographic color power in the TUN group (p = .028). VEGF levels and ultrasonographic mean perfused area of the CTG were significantly correlated at the 7-day time point (p < .001 for both CAF and TUN). The expression of VEGF at 7 days was directly associated with mucosal thickness gain at 1 year (p < .001 for both groups). Early TIMP-2 expression showed an inverse correlation with time to recovery (p = .002). TIMP-2 levels at 3 months exhibited inverse correlations with mean dehiscence coverage (p = .004) and the rate of complete dehiscence coverage (p = .012).

Conclusion: PICF biomarkers can be used to monitor early wound healing events following soft tissue grafting at implant sites. VEGF and TIMP-2 showed correlations with the 1-year clinical and volumetric outcomes, as well as with post-operative patient-reported outcomes and Doppler Ultrasonographic tissue perfusion-related parameters.

Keywords: blood circulation; blood flow velocity; crevicular fluid; dental implants; graft; ultrasonography; wound healing.

FIGURE 1

Collection of the peri‐implant crevicular fluid at 1 week and related high frequency ultrasonographic (HFUS) scans recorded at the midfacial aspect. It is possible to appreciate the implant‐supported crown (“Cr”), the implant fixture (“Imp”), the graft, and the flap. Doppler ultrasonographic blood flow evaluation included Color Power Doppler, Color Doppler Velocity, and dynamic tissue perfusion assessment. In particular, the right panel displays the dynamic tissue perfusion evaluation in terms of perfusion relief intensity (pRI) of the connective tissue graft after 1 week. pRI refers to the number of pixel within the region of interest (graft) that relate to the intensity of the respective value. Areas with zero intensity/perfusion within the ROI are shown in black, whereas areas with half of the maximum intensity/perfusion and maximum intensity/perfusion are visualized in white and red, respectively.

FIGURE 2

Graphs depicting the variations of ANG, FGF‐2, PDGF‐BB, TIMP‐2, and VEGF at the buccal aspect of implant sites augmented with CTG (either with CAF or TUN), and at their lingual aspect. Mean and standard error reported for each panel. Legend. “a” denotes a statistically significant difference (p < .001) between the buccal aspect (either CAF or TUN) and the lingual aspect. “b” and “c” denote a statistically significant difference (p < .01 and p < .05, respectively) between the buccal aspect (either CAF or TUN) and the lingual aspect. “d” indicates a statistically significant difference (p < .05) between CAF and TUN.

FIGURE 3

(A) Graph depicting the correlation between VEGF expression and tissue perfusion of the graft in terms of perfusion relief area (pA) at 1 week (p < .001 for both CAF and TUN). (B) Dynamic tissue perfusion assessment and pA quantification in an ultrasonographic scan obtained at the midfacial aspect of a dental implant 1 week after soft tissue augmentation.