196 Chapter 9 When developing a new saliva substitute, it is also important to try to mimic the complex biological properties of natural saliva, including neutralizing harmful bacteria and optimizing the mouth flora. Many Sjögren’s syndrome patients with a reduced salivary flow have alterations in the composition of the oral bacterial plaque despite good oral hygiene measures [20, 21], which causes an increased risk of caries and candidiasis [20, 21]. Moreover, the salivary pH, bicarbonate concentration, and buffer capacity were significantly lower in the Sjögren’s syndrome patients than healthy controls [21]. Besides an increased caries risk, these patients have also a higher risk of tooth erosion, as they experience a greater decline in salivary pH after exposure to acidic challenges. These factors might explain the urge of Sjögren’s syndrome patients for a salivary substitute that “neutralizes harmful bacteria” and “optimizes the mouth flora”. Saliva plays a major role in taste perception, as the hypotonicity of unstimulated saliva allows the taste buds to perceive different tastes without being masked by normal plasma sodium levels [22]. Moreover, saliva is very important for the solubilization of flavours in saliva, for the chemical interaction between flavours and salivary ingredients, and for the dilution and/or the diffusion of flavours in saliva [23]. Based on these factors, it is conceivable that taste sensitivity is easily affected by changes in saliva [23], especially in Sjögren’s syndrome patients with a low unstimulated salivary flow rate [24–30] and altered rheological properties of saliva [31]. This altered taste sensitivity may explain why these patients had objections against the presence of “artificial sweeteners” and “alcohol” and why they preferred a “neutral flavour” or “no flavour” at all. Previous studies showed that an unpleasant taste is a major reason for Sjögren’s syndrome patients to discontinue the use of saliva substitutes [12]. Sjögren’s syndrome patients having sicca syndrome are recommended to avoid alcohol [32], which may explain why patients prefer saliva substitutes without alcohol. Given these reasons, it is important to develop new saliva substitutes with a “neutral flavour” without “artificial sweeteners” nor “alcohol”. In contrast to our expectation described in the “Introduction”, the presence of specific animal-based ingredients seems of very limited importance, compared to other ingredients such as “artificial sweeteners” or “alcohol”. Sjögren’s syndrome patients reported major objections against discoloration of the teeth or the oral mucosa as potential side-effects of the use of saliva substitutes. Discoloration was not mentioned in a study reporting side-effects of some saliva substitutes [33]. Possibly, these objections against
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