ALP, ACP, ALT, AST and CK are intracellular enzymes incorporated in metabolic pathways of cells and they are mostly present in cells of soft tissues. These enzymes are indicators of a higher level of cellular damage and their increased activity in gingival crevicular fluid and saliva is a result of their increased discharge from the damaged cells of soft tissues of soft and attached gingival, cementum, periodontal ligament etc. Increased level of these enzymes directly reflects the metabolic changes in the inflamed soft and attached gingiva (6). Previous studies mainly investigated the levels of these enzymes in the GCF, which is in closer contact with periodontal tissues.
But, the problem with the GCF is the collection is very complicated and hardly practicable. The activities of these enzymes can also be found in saliva, since these enzymes are also found in blood of healthy people. When a periodontal tissue becomes become damaged due to oedema or destruction of a cellular membrane these intracellular enzymes are released into the GCF and saliva where their activity or level can be measured (7). Compare to the GCF, there is plenty of saliva; and its sampling is much easier and more acceptable for the patient. Being a simple and non-invasive collection process, salivary diagnostic tests hold promise for the future. ALP and ACP are intracellular enzymes present in most of tissues and organs, but especially found in bones. Their increased activity in saliva is probably due to the result of destructive processes in the alveolar bone during advanced stages of periodontal disease (8). The positive correlation between the activity of ALP and the percentage of the alveolar bone loss has been shown by some (9, 10).
Some studies have shown a remarkably increased activity of ALP in the acute phase of periodontal disease, and after the periodontal therapy, the activity of these enzymes restored to the value as found with the healthy persons (11).This research has shown that the increased level of ALP, ACP, ALT, AST and CK enzymes in periodontal disease can be found in saliva as a result of pathological changes in cells of periodontal tissues. The value of their activity can reflect the severity of pathological processes and destruction of periodontal tissues and can point toward the prognosis of the disease.
The increased activity of ALP, ACP, ALT, AST and CK indicates the pathological changes located in soft tissues only, primarily in gingiva what could coincide with the initial stage of periodontal disease. However, the increased activity of ACP, especially ALP, indicates that the pathological destructive process has affected the alveolar bone what means that periodontal disease has significantly advanced and thus the prognosis is much worse. The activity of these enzymes in saliva can be of useful for the assessment of efficiency of changing the therapy in curing periodontal disease (12).