Electrolytes in stimulated whole saliva in individuals with hyposalivation of different origins
Introduction
Saliva consists of 99% water and 1% organic and inorganic components. The main inorganic components are sodium, potassium, chloride, calcium, phosphate and bicarbonate, all contributing to the ionic strength of saliva. Access to calcium and phosphate is of importance for the remineralisation of the tooth surfaces after acid challenge. Bicarbonate, phosphate and the organic components contribute to the buffer capacity of the saliva. Bicarbonate is the principal buffer at pH 7 down to pH 5,1 while the organic components perform this role from pH 5 down to pH 4. The phosphates contribute to the buffer capacity at a low salivary flow rate.1 A pH around neutral is optimal for the growth of micro-organisms associated with oral health.2., 3. A pH below neutral promotes the growth of cariogenic micro-organisms and other acid-tolerant species associated with mucosal infections, while a pH above neutral favours micro-organisms associated with periodontitis.2., 3.
In individuals with a normal salivary secretion rate, the concentrations of sodium, calcium and bicarbonate are positively correlated with the stimulated secretion rate.4 The potassium concentration is independent of flow rate and the phosphate concentration decreases slightly when the flow rate increases.5
In those with hyposalivation due to primary Sjögren’s syndrome and those treated with radiation therapy in the head and neck region, in spite of a reduction in salivary secretion rate, the sodium and chloride concentrations in stimulated whole saliva are higher than in individuals with normal salivary secretion6., 7., 8. However, for potassium and calcium, the concentrations were found to be increased in stimulated whole saliva in primary Sjögren’s syndrome,7., 8. while in radiation-induced hyposalivation, the potassium concentration was comparable with pre-irradiation levels and the calcium concentration was lower.6 Furthermore, in our previous study,9 the buffer capacity was lower in individuals on neuroleptic treatment than in those with radiation-induced hyposalivation or primary Sjögren’s syndrome, despite a higher stimulated secretion rate. So there are reasons to believe that the concentrations of inorganic components in saliva not only vary according to the saliva secretion rate but also according to the reason for the hyposalivation.
Our aim now was to assay bicarbonate, sodium, potassium, calcium and phosphate in stimulated whole saliva from individuals with hyposalivation of different origins, due to radiation therapy, primary Sjögren’s syndrome, neuroleptic treatment, medication or of unknown origin.
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Material and methods
The study was approved by the ethics committee at Göteborg University. To be included, the participants had to be between 45 and 65 years of age and dentate with ≥16 natural teeth and no removable prosthetic constructions or implants. After obtaining informed consent, the participants comprised nine individuals who had completed radiation therapy in the head and neck region 1–2 years earlier, 10 with primary Sjögren’s syndrome diagnosed according to the Copenhagen criteria10 7±5 years
Results
The age and sex distributions, clinical measures, salivary secretion rates, pH and buffer capacities in the groups are presented in Table 1. The neuroleptic group had the highest number of sites with bleeding on probing, about 80% of the total number of sites. The radiotherapy and Sjögren’s syndrome groups had both the lowest unstimulated and the lowest stimulated secretion rates. In the neuroleptic group, the unstimulated secretion rate was slightly higher than in the control group, while the
Discussion
The most common disorders in the mouth, caries, periodontitis, gingivitis and mucosal infection, are associated with an increase in specific micro-organisms. There is reason to believe that changes in the secretion rate of saliva, as well as changes in its protein and electrolyte composition, promote the growth of micro-organisms associated with these disorders.2., 3., 15., 16., 17. A knowledge of the electrolytes in the saliva of individuals with hyposalivation of different origins might
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