A previous study has found individuals with reduced salivary flow rate (<0.1 ml/min) to be up to five times more likely to have dental erosion than individuals with higher flow rate, thus salivary flow may be particularly important in protecting against dental erosion among people with dry mouth.
Individuals with a low salivary flow rate also often have low salivary buffer capacity. This may also affect their susceptibility to dental erosion, as individuals with low buffer capacity have been shown to be at risk of developing dental erosion.
Additionally, salivary protein which forms the basis of acquired pellicle on the enamel, is known to protect tooth enamel. Therefore, data on salivary status may help to determine individual susceptibility to developing dental erosion.
HAp+ is clinically proven to be saliva stimulating and non-erosive in 90% of the dry mouth population tested
At least 10% of a population may have dry mouth
The prevalence of xerostomia, the subjective feeling of dry mouth, was found to be around 10% in 1996.
The 10% prevalence of xerostomia positively correlates with the objective measurement of reduced salivary flow, hyposalivation. It is however also generally known that the prevalence of dry mouth patients has significantly increased over the last decade. The most well known cause of xerostomia and hyposalivation is the intake of medication, autoimmune diseases such as Sjögren’s syndrome, and irradiation therapy on the head and neck area. Although the radiated patients comprise a very small group, their radiation-induced xerostomia and hyposalivation often belong to the most severe end of the spectrum. As it is generally acknowledged that patients with dry mouth seek oral relief through intake of acidic candies, these patients may be at greater risk of developing dental erosion than normal salivating individuals.
Xerostomia and hypsalivation
Xerostomia is the subjective feeling of dry mouth, whereas hyposalivation refers to an objective measurement of a low salivary flow rate.
If the salivary flow rate in the unstimulated state is less than 0.1 ml/min and in the stimulated state less than 0.5 ml/min, the diagnosis of hyposalivation is given. Efficient dilution, which is driven by the flow of saliva, is crucial to rinse substances from the oral cavity and protect the oral tissues. The average unstimulated salivary flow is normally 0.2 to 0.5 ml per minute. The average flow of stimulated saliva varies between 1 and 2 ml on average per minute when stimulated by chewing a flavorless substance such as paraffin, parafilm, non-tasting gum etc. The stimulated salivary flow rate can, however, become as high as 5-10 ml per minute in individuals with normal unstimulated saliva flow, when stimulated by an acidic taste from acidic foodstuffs or citric acid solutions.
Oral clearance refers to the elimination of substances from the mouth and thus the salivary flow.
When measuring oral clearance, the disappearance of a substance, normally sugar, from the mouth is determined as a function of time. Two factors, in particular, are important for oral clearance: the salivary flow rate and the frequency of swallowing. Oral clearance after rinsing with citric acid has been shown to be highly dependent on the individual. Slow oral clearance refers to the situation where the substance is present in the mouth for a long period of time (minutes or hours) after ingestion. Such a situation is almost always caused by a low salivary flow rate, and especially a low unstimulated salivary flow rate. If the oral clearance is slow, acid can accumulate in the mouth and the destructive process of dental erosion is accelerated. The destructive process depends on the type of food- in question and its stimulatory effect on flow and thus how much saliva is produced upon eating or drinking the particular foodstuff. Some foodstuffs have certain physical properties, measured as thermodynamic property of adhesion, which makes them adhere to the tooth substance. Accordingly, the clearance of such foodstuffs will be prolonged. In healthy individuals with normal salivary flow it has been proposed that erosive damage will be limited to the time of ingestion of acidic foodstuffs because of the rapid clearance of acid. Thus, the ability to produce saliva is important for protection against dental erosion, especially with respect to clearing acidic compounds.