Sialochemistry; A Diagnostic Tool
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Submandibular and sublingual saliva can be collected by cannulation of the duct with micropipette, but in practice this is both uncomfortable for the patients and technically difficult since the duct orifice is mobile and has a strong sphincter. Because of that, alginate and silicone impression material is used for retention of the collecting tube. As alternative and simple technique is to block off secretion from the parotid glands with absorbent swabs and collect mixed submandibular and sublingual saliva by pipette from the floor of the mouth. Saliva from labial and palatal glands can be collected by filter paper disc or disc of other synthetic materials.10 Salivary flow rate is given as ml/min/gland. Under ‘resting’ conditions the flow rate of the parotid gland amounts to 0-0.1 ml/min. After citric acid stimulation the range is 0.5-1.5 ml/min. Stimulated values below 0.3 ml/min are considered pathological. Elevated flow rates will be seen under conditions such as gingivitis, recent prosthesis and dominant cholinergic activity in Parkinson’s disease, intoxication etc. Low values are found during the use of tricyclic
antidepressants, after duct disintegration caused by inflammation or irradiation and after radical surgical treatment. The effects are more dramatic in resting saliva on account of intensified water reabsorption in the resting state.
SIALOCHEMISTRY
The choice of laboratory investigations should be based on presumed relationships with intra glandular transport processes (sodium), intra cellular synthesis (protein, amylase), and diffusion by plasma constituents (urea). Saliva also influences the oral environment in a number of ways. Measurements are given as concentrations c.q. mmol/1. This facilitates the assessment of ion/water shift and osmotic values. Secreted solutes, given as mmol/min or in mg/min (mmol/1 x ml/min), are useful in judging acinar destruction, as in irradiation and aging. Routine laboratory investigations include potassium calcium, sodium, chloride, bicarbonate, urea, total protein, amylase, and osmolarity measurements.
The diagnostic use of saliva has attracted the attention of numerous investigators because of the noninvasive nature and relative simplicity of collection. Saliva collection also simplifies the diagnostic process in special populations in whom blood drawing is difficult, i.e. individuals with compromised venous access (e.g., injecting drug users), patients with hemophilia and children.
The presence of six enzymes was established in parotid saliva: acid phosphatase, total esterases, cholinesterase, lipase, beta-glucuronidase, and lysozyme. Broth cultures used for this study with whole saliva indicated that all but sulfatase and lysozyme were produced by the oral flora.8
Abnormal proteins are also produced under exceptional conditions, such as the development of tumours and nutritional deficiency. Low a-amylase concentrations are seen in cases of starvation and after destruction and degeneration of the acinar cells. Elevated a-amylase is seen in abnormal ductal water loss. Furthermore, acute inflammation of the glands produces a rise in plasma and urine amylase due to gross glandular leakage. This will be seen in mumps as well as in the presence of a salivary calculus.11Salivary analysis can be valuable to discriminate and monitor swellings of major salivary glands such as chronic recurrent parotitis, where the blood-saliva barrier is violated in the inflammatory flare-ups and characterized by the leakage of serum components (albumin) and lactoferrin into saliva
Higher enzyme activities were found in the adult periodontitis patients compared to the healthy controls for alkaline phosphatase, esterase, β-glucuronidase, β-glucosidase, and other aminopeptidases. Saliva from patients with localized juvenile periodontitis contained the highest levels of butyrate esterase and cystiene aminopeptidase12.
Sialochemistry can be expected to reveal the differentiation between normal and abnormal function of the glands, information about gland dysfunction and its impact on the oral environment, clues to homeostatic fluctuations as a result of circulatory, innervatory, or hormonal adjustments. The development of microchips for salivary components offers great possibilities to use oral fluid for point-of-care testing.13
Another fertile area of application for salivary analysis is in laboratory medicine, where determining and monitoring levels of various hormones (cortisol, progesterone, estriol, testosterone etc.) and drugs (diazepam, caffeine,