Aspartate aminotransferase activity in crevicular fluid from dental implants

Background: Aspartate aminotransferase (AST) is an enzyme normally confined to the cytoplasm of cells, but released to the extracellular environment u pon cell death. Its levels are associated with the severity of experimental gingivitis and the loss of periodontal attachment. The aim of the present study was to investigate the presence and activity levels of AST in peri-im plant crevicular fluid (PCF) from healthy and diseased endosseous implants in order to assess if AST in PCF can be further studied as a possible objec tive diagnostic aid in oral implantology. Methods: Eighty-one fixtures from 81 systemically healthy subjects were div ided into 3 groups, 27 healthy implants (HI), 27 implants with mucositis (M I) and 27 implants affected by peri-implantitis (PI) according to well-defi ned clinical and radiographic criteria. PCF was collected by the insertion of a # 40 standardized endodontic paper point to the base of the crevice or pocket for 30 seconds. AST activity was determined spectrophotometrically at 25 degreesC. The results were expressed as AST Units/ml in PCF. Results: An AST activity was detected in each sample from HI, MI and PI. Th e mean AST activity in HI was 0.26 +/- 0.16 U/ml; in MI, 0.38 +/- 0.27 U/ml ; in PI, 0.62 +/- 0.29 U/ml. ANOVA showed that the difference among HI, MI, and PI was statistically significant at P <0.01 level. Post-hoc tests demo nstrated that a significant difference in AST activity existed between HI/P I (t = 5.14; P <0.01) and MI/PI (t = 3.09; P<0.01). No statistically signif icant difference was found between HI/MI (t = 1.07; P>0.1) AST activity was significantly (P <0.01) associated with probing depth (r = 0.55), the amou nt of bone loss (r = 0.60) and bleeding on probing (r = 0.67). When the thr eshold for a positive AST test was set <greater than or equal to>0.4 U/ml, a sensitivity = 0.81 and a specificity = 0.74 were found in the detection o f peri-implantitis; the positive predictive value was 61% and the negative predictive value was 88%. Conclusions: Within the limits of this study, our results may suggest that PCF analysis could be further investigated in longitudinal studies as a sui table diagnostic strategy in the evaluation of dental implants.