Sialochemistry; A Diagnostic Tool
Sialochemistry; A Diagnostic Tool
Introduction
A large number of diagnostic analytes have been shown to be present in saliva, including steroid hormones1 and the HIV antibody.2 For the past two decades, oral health researchers have been developing salivary diagnostic tools to monitor oral diseases (including periodontal diseases),3,4 as well as for caries risk assessment5 .These diagnostic advances range from genetic susceptibility analysis of interleukin-1 (IL-1) genetic alleles to the analysis of oral pathogens identified via lectin staining for caries risk assessment.6 The current development of diagnostic biomarkers (via proteomic and genomic approaches) in conjunction with technological developments in salivary diagnostics will lead to the development of robust diagnostic tools for dentists to use in making clinical decisions and predicting treatment outcomes. 7
SALIVA COLLECTION
Whole saliva is a product of secretion of 3 major glands (parotid, submandibular, sublingual) and many minor glands (labial, buccal, palatal). Unstimulated saliva is usually obtained as the patient spits out every 60 sec or by forward bended head, the patient allows saliva to drip off the lower lip into a cylinder. By collection of saliva in the tube the flow rate per unit time can be measured. When volume measurement is not required the saliva can be collected on cotton rolls, gauze or filter paper. For evaluating salivary gland function or when large volumes of saliva are required for analytic purposes, stimulated whole saliva is used. Method of collection is the same as for unstimulated saliva.8
The usual masticatory stimuli are paraffin wax or a washed rubber band. A standard gustatory stimulus is obtained by 2% citric acid applied directly to the tongue every 15 to 60 sec. Parotid saliva can be collected by aspiration from the duct opening with a micropipette. Parotid saliva is best collected with Lashley’s vacuum chamber(fig1& 2)9
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 usual masticatory stimuli are paraffin wax or a washed rubber band. A standard gustatory stimulus is obtained by 2% citric acid applied directly to the tongue every 15 to 60 sec. Parotid saliva can be collected by aspiration from the duct opening with a micropipette. Parotid saliva is best collected with Lashley’s vacuum