15 General introduction, aim and outline of the thesis the severity of dry mouth, which may predict hyposalivation [28]. For this questionnaire a binary scale is used [28, 29]. Eisbruch et al. evaluated the grade of xerostomia through a validated scale: subjective grade 1: no disability; grade 2: dryness requiring additional fluids for swallowing; and grade 3: dryness causing dietary alterations, interference with sleep, speaking, or other activities [28, 29]. In turn, Pai et al. developed an 8-item visual analog scale (VAS) to assess xerostomia [28, 29]. Finally, Suh et al. developed a questionnaire with a combination of a binary scale, categorical scoring scale and VAS [30]. Yet, at the moment there is no clear scientific consensus on the best form of grading xerostomia, mainly due to differences in opinion about the best way to obtain information from the patient [16]. In the past, Navazesh and co-workers developed a clinical scale consisting of four clinical measures; dryness of lips, dryness of buccal mucosa, absence of saliva produced by gland palpation, and total DMFT (decayed, missing, and filled teeth). Together, these four measures could successfully predict the presence or absence of salivary gland hypofunction [31]. More recently, the clinical oral dryness score (CODS) has been designed to objectively quantify clinical signs of reduced salivary secretion [32, 33]. The CODS has been developed to help oral health professionals with the objective and quick determination of salivary gland function in a clinical setting [32, 33]. The CODS is based on clinical and visual inspection of the mouth to inspect for various signs of oral dryness such as the presence of frothy saliva and stickiness of the dental mirror to the tongue or the buccal mucosa [32, 33]. In turn, measurement of the salivary flow rate is the objective tool for hyposalivation. It is relatively easy to perform and requires little time [28]. Salivary flow rates can be determined by various methods, either by collection of unstimulated and stimulated whole saliva or by collection of saliva from specific salivary glands [29]. By draining saliva passively into a pre-weighed cup unstimulated whole saliva can be collected (draining method) [28]. Alternatively, Leal et al. suggested the use of pre-weighed cotton rolls for collection of saliva from the orifices of the ducts of the major salivary glands. After a specific time, the cotton rolls are weighed again and saliva flow can be calculated. Also, absorbent strips can be used, which can be placed at various intra-oral locations to determine salivary flow [28]. Other methods to assess the unstimulated whole salivary flow rate include the so called ‘spitting method’ and the ‘suction method’ [28]. Stimulated salivary flow rate is determined while the patient chews an unflavored gum base or paraffin wax (1–2 g) for 1 or several minutes. Otherwise, saliva production can be stimulated with a solution 1
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