Free amino acid levels in oral fluids of normal subjects and patients with periodontal disease.

The content of free amino acids in submandibular, parotid and whole saliva and in gingival fluid was measured by automatic analyser in patients with progressive periodontitis and in controls. The concentration of individual amino acids showed considerable variation in all the fluids. Two amino acids, proline and delta-aminovaleric acid, were never found in gingival fluid or in submandibular and parotid saliva, although detectable in whole saliva. Thus, these amino acids must appear in whole saliva as a result of bacterial metabolism or by degradation of salivary proteins rich in proline. The free amino acid levels in whole saliva did not reflect those of any of the single oral fluids analysed, further stressing the importance of bacterial metabolism as a cause of the wide range of amino acid concentrations. Because of the multifactorial origin of these free amino acids, their determination in oral fluids is of no practical diagnostic value except perhaps in extreme cases.