The total amount of cytokine IL-17 in GCF samples and in the culture supernatants of gingival cells are significantly increased in periodontal disease.

Significant correlations between the severity of the periodontal disease and the actual MMP activity, the active form of MMP-8 and the low level of both TIMP-1 and TIMP-2 were found.

The total amount and concentration of cytokine IFN-gamma in GCF samples and transcription factor T-bet expression were increased in progressive periodontal lesions in patients with chronic periodontitis.

This study describes an alternative way of applying failure mode and effects analysis (FMEA) to a wide variety of problems. It presents a methodology based on a decision system supported by qualitative rules which provides a ranking of the risks of potential causes of production system failures. By providing an illustrative example, it highlights the advantages of this flexible system over the traditional FMEA model. Finally, a fuzzy decision model is proposed, which improves the initial decision system by introducing the element of uncertainty.

Background: Receptor activator of nuclear factor κB ligand (RANK‐L) is a cytokine involved in the regulation of osteoclastogenesis in bone remodeling and inflammatory osteolysis. One of the major causes of tooth loss in humans is bone destruction. The aim of our study was to determine the presence of RANK‐L in gingival crevicular fluid (GCF) samples from adult patients with untreated chronic periodontitis and in healthy controls. We also identified the RANK‐L present in lesions undergoing episodic attachment loss from GCF. Methods: GCF samples were collected from two periodontally affected sites (probing depth ≥5 mm, attachment loss ≥3 mm) in 20 patients (N = 40). After monitoring for 4 months, seven patients showed active periodontal disease, and GCF samples were collected from one active and one inactive site (N = 14 samples). The comparison with healthy controls was carried out by collecting GCF samples from 12 healthy volunteers (N = 24 samples). GCF was collected using a paper strip, and enzymelinked immunosorbent assay (ELISA) was performed to determine the total amount of RANK‐L. Results: RANK‐L was found in a higher proportion (85%) of samples from patients than from controls (46%). The total amount of RANK‐L was significantly higher in patients (115.53 ± 78.18 picograms [pg]) than in healthy subjects (63.08 ± 55.08 pg) (P = 0.003). Active sites, presumably associated with tissue destruction, had significantly higher levels of RANK‐L than their inactive counterparts (125.95 pg versus 91.80 pg, P = 0.007). Conclusion: GCF total amount of RANK‐L is significantly increased in periodontal disease, supporting its role in the alveolar bone loss developed in this disease. J Periodontol 2004;75: 1586‐1591.