49 Differences in perceived intra-oral dryness INTRODUCTION Saliva plays a crucial role in the preservation and maintenance of oral health due to its multiple functions, which include buffering capacity, lubrication, moistening, microbial homeostasis, and wound healing [1–4]. The consequences when salivary flow is impaired are therefore multidimensional, transcending oral health. For example, hyposalivation increases the risk of dental caries, gingivitis, and periodontitis. In addition, patients with impaired salivary flow can experience dry mouth, oral discomfort and pain, difficulty in speaking, taste alterations, and difficulty in swallowing [1, 2, 5]. Altogether, the effects of hyposalivation can have physical, emotional, and social impacts, thereby negatively affecting the quality of life, and particularly oral health [5, 6]. Dry-mouth symptoms can be caused by the use of xerogenic medications or multiple medications, but also by radiotherapy of the head and neck region, systemic diseases such as Sjögren’s syndrome, and chronic stress [1, 5, 7, 8]. Obviously, dry-mouth symptoms may also be induced by a combination of factors [5]. For example, multiple medication usage is common in patients with Sjögren’s syndrome. These etiologic factors produce dry-mouth symptoms through a variety of mechanisms. For example, dry-mouth–inducing medications have anticholinergic or sympathomimetic actions that affect the neural control of salivary glands, have a cytotoxic effect on the salivary glands, have a diuretic effect that depletes fluids, or damage the ion-transport pathways in the acinar cells. Irradiation of tumour sites in the head and neck region can also damage the salivary glands, leading to complete dysfunction of acini. On the other hand, Sjögren’s syndrome induces progressive immunemediated self-destruction of the salivary glands and lacrimal glands [1, 5]. Several mechanisms thus lead to impaired salivary function, and, as a consequence, hyposalivation and xerostomia, i.e., perceived oral dryness. As hyposalivation and xerostomia are not correlated per se [9, 10], any diagnosis of dry mouth should include objective parameters such as total salivary flow and subjective parameters such as total perceived oral dryness. However, due to the complex etiology of drymouth and the variousmechanisms underlying them, these parameters do not seem entirely discriminative. Diagnosis is difficult, especially for early-stage Sjögren’s patients who lack specific clinical manifestations and biomarkers [11]. As the median delay between the onset of Sjögren’s syndrome and diagnosis is 4 years (range 0– 28 years) [12], these current diagnostic tools are not sufficient for a more advanced dry-mouth diagnosis. 3
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