Protease activities in peri-implant sulcus fluid from patients with permucosal osseointegrated dental implants. Correlation with clinical parameters

The 15 patients included in this study each had 2-6 permucosal Branemark osseointegrated implants that had functioned successfully for 18 months or more. They were given a full oral examination which included measurements of probing depth and gingival, bleeding and plaque indices around the implants. Marginal bone reduction during the functional life of the implants was estimated from radiographs. At a separate visit, peri-implant sulcus fluid (PISF) was collected on filter paper strips from the deepest probing site of each implant. PISF volumes were measured and the samples eluted into buffer. Proteases activities in the eluates were determined by fluorimetric assay with peptidyl derivatives of 7-amino-4-trifluoromethyl coumarin. Enzyme levels followed the order: cathepsin B/L > elastase > dipeptidyl peptidase IV > trypsin-like activity. Total enzyme activities and concentrations both correlated positively with all clinical parameters in linear regression analysis. This was true on both a patient level using mean patient values and a site level using pooled patient data. Nearly all of the site level correlations were statistically significant, though coefficients were generally higher for total enzyme activities than concentrations. Elastase-like activity gave the best overall correlations of the different proteases measured. Amongst the clinical parameters, correlations were generally best with gingival index and bone reduction. Total enzyme activities had good diagnostic specificity and sensitivity as predictors of clinical parameters and the figures were especially high for elastase-like activity as a marker of bone reduction. PISF proteases may thus be of value in monitoring tissue responses to osseointegrated implants.