Tongue coating
Seerangaiyan, Kavitha
IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below.
Document Version
Publisher's PDF, also known as Version of record
Publication date: 2018
Link to publication in University of Groningen/UMCG research database
Citation for published version (APA):
Seerangaiyan, K. (2018). Tongue coating: It’s impact on intra-oral halitosis and taste. Rijksuniversiteit Groningen.
Copyright
Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).
Take-down policy
If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.
Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum.
CHAPTER
5
Tongue cleaning increases the perceived intensity of
salty taste
Seerangaiyan K, Jüch F, Atefeh F, Winkel EG
Abstract
Objectives: Tongue coating, which refers to a greyish white deposit on the tongue
surface, often covers the taste papillae on the dorsal tongue surface, decreasing taste sensitivity. This study investigated whether mechanical removal of the tongue coating affected the intensity of salt taste perception. Participants: This cross-sectional single blind study included 90 subjects (29 males, 61 females) with a mean age of 45 years (range 25–70 years). Intervention: The presence and the amount of coating on the six sextants of the tongue were scored using the Winkel Tongue Coating Index (WTCI); the 90 included subjects had total WTCI scores ≥ 3. The intensity of the salt taste was tested using a drop of prepared tomato soup applied to the middle of the dorsal surface of the tongue before and then after tongue cleaning. Measurement: The salt taste intensity was measured using a general Labeled Magnitude Scale (gLMS).
Results The mean salt taste intensity was significantly different (p value = 0.0002)
after the intervention versus before it, with the taste intensity increasing after tongue cleaning. Conclusions: The results indicated that the salt taste intensity increased after removal of the tongue coating. This study indicates that tongue cleaning, a simple technique used for oral hygiene, may be an effective way to reduce excess salt intake. Tongue cleaning could help individuals adhere to the WHO recommendations on dietary salt intake.
Key words:
Salt, tongue coating, taste intensity, tongue cleaning
Introduction
Sodium is an essential nutrient. Sodium helps maintain the electrolyte balance in humans, and it is important for normal physiological functions and for maintaining cellular homeostasis [1]. Salt (sodium chloride) is the main form of sodium intake in humans and is abundantly present in the typical daily diet. Salt intake in humans ranges from 5–9 grams of salt/day, which is almost twice the amount recommended by the World Health Organization (WHO) [2]. Notably, high salt intake is a risk factor for elevated blood pressure and consequently for cardiovascular disease, stroke, obesity, kidney disease, and gastric cancer [3]. Reducing daily salt intake is recommended to control and prevent these hypertension-associated diseases [4]. Consequently, the WHO guidelines on dietary salt intake advise a daily intake of less than 2 grams of sodium, which is equivalent to 5 grams of salt per day [2]. High salt intake by humans is the result of several factors but is mainly the result of salt being consumed mostly based on taste preference rather than to meet a physiological need [5]. Repeated exposure to salty foods often increases one’s enjoyment and increased acceptance of salt [6, 7].
Several strategies have been used to reduce salt intake as a matter of public health, including awareness and education campaigns that address salt intake, front package labeling of salt content, taxation of salty foods, and industrial reformulation for food preparation [8]. However, initiatives have failed to acceptably reduce salt intake in the general population. Voluntary reduction in salt intake often requires a behavioral change. According to the transtheoretical model of health behavior,
changing behavior can take a long time in order to establish a new pattern of behavior [9].
The taste perception system gives us information on food quantity, quality, electrolyte composition, and identity. Stimulation of taste receptors, oral mechano- and temperature receptors, and olfactory receptors produces particular taste sensations. These taste sensations can be expressed as the intensity, palatability, or hedonic values of the tasted substances [10]. Notably, poor oral hygiene is often associated with an increase in the tongue plaque deposits that together are termed the tongue coating [11]. The tongue coating consists of dead epithelial cells, food particles, and bacteria. It covers the taste papillae on the dorsal tongue surface and may block taste substances from reaching taste cells, thereby decreasing taste sensitivity. A recent study of the effect of tongue coating removal on taste perception clearly indicated that its removal improved salt recognition [12]. However, the relationship between tongue coating removal and taste intensity changes has not been studied.
The aim of this study was to investigate the effects of mechanical tongue coating removal on the intensity of salt taste perception. If simple tongue cleaning
CHAPTER 5 Abstract
Objectives: Tongue coating, which refers to a greyish white deposit on the tongue
surface, often covers the taste papillae on the dorsal tongue surface, decreasing taste sensitivity. This study investigated whether mechanical removal of the tongue coating affected the intensity of salt taste perception. Participants: This cross-sectional single blind study included 90 subjects (29 males, 61 females) with a mean age of 45 years (range 25–70 years). Intervention: The presence and the amount of coating on the six sextants of the tongue were scored using the Winkel Tongue Coating Index (WTCI); the 90 included subjects had total WTCI scores ≥ 3. The intensity of the salt taste was tested using a drop of prepared tomato soup applied to the middle of the dorsal surface of the tongue before and then after tongue cleaning. Measurement: The salt taste intensity was measured using a general Labeled Magnitude Scale (gLMS).
Results The mean salt taste intensity was significantly different (p value = 0.0002)
after the intervention versus before it, with the taste intensity increasing after tongue cleaning. Conclusions: The results indicated that the salt taste intensity increased after removal of the tongue coating. This study indicates that tongue cleaning, a simple technique used for oral hygiene, may be an effective way to reduce excess salt intake. Tongue cleaning could help individuals adhere to the WHO recommendations on dietary salt intake.
Key words:
Salt, tongue coating, taste intensity, tongue cleaning
TONGUE COATING - TASTE Introduction
Sodium is an essential nutrient. Sodium helps maintain the electrolyte balance in humans, and it is important for normal physiological functions and for maintaining cellular homeostasis [1]. Salt (sodium chloride) is the main form of sodium intake in humans and is abundantly present in the typical daily diet. Salt intake in humans ranges from 5–9 grams of salt/day, which is almost twice the amount recommended by the World Health Organization (WHO) [2]. Notably, high salt intake is a risk factor for elevated blood pressure and consequently for cardiovascular disease, stroke, obesity, kidney disease, and gastric cancer [3]. Reducing daily salt intake is recommended to control and prevent these hypertension-associated diseases [4]. Consequently, the WHO guidelines on dietary salt intake advise a daily intake of less than 2 grams of sodium, which is equivalent to 5 grams of salt per day [2]. High salt intake by humans is the result of several factors but is mainly the result of salt being consumed mostly based on taste preference rather than to meet a physiological need [5]. Repeated exposure to salty foods often increases one’s enjoyment and increased acceptance of salt [6, 7].
Several strategies have been used to reduce salt intake as a matter of public health, including awareness and education campaigns that address salt intake, front package labeling of salt content, taxation of salty foods, and industrial reformulation for food preparation [8]. However, initiatives have failed to acceptably reduce salt intake in the general population. Voluntary reduction in salt intake often requires a behavioral change. According to the transtheoretical model of health behavior,
changing behavior can take a long time in order to establish a new pattern of behavior [9].
The taste perception system gives us information on food quantity, quality, electrolyte composition, and identity. Stimulation of taste receptors, oral mechano- and temperature receptors, and olfactory receptors produces particular taste sensations. These taste sensations can be expressed as the intensity, palatability, or hedonic values of the tasted substances [10]. Notably, poor oral hygiene is often associated with an increase in the tongue plaque deposits that together are termed the tongue coating [11]. The tongue coating consists of dead epithelial cells, food particles, and bacteria. It covers the taste papillae on the dorsal tongue surface and may block taste substances from reaching taste cells, thereby decreasing taste sensitivity. A recent study of the effect of tongue coating removal on taste perception clearly indicated that its removal improved salt recognition [12]. However, the relationship between tongue coating removal and taste intensity changes has not been studied.
The aim of this study was to investigate the effects of mechanical tongue coating removal on the intensity of salt taste perception. If simple tongue cleaning
could change the perceived intensity of salt, it could be used to rapidly make lower salt concentrations more acceptably to people without changing the palatability of the food [13].
Materials and Methods
Ethical approval: The Medical Ethics Committee of the University Medical Center
Groningen approved the study protocol (reference number: METC 2015/601). Informed consent was obtained from all individual participants included in the study The study was conducted in accordance with all Dutch laws governing research ethics rules and principles and in accordance with the tenets of the Declaration of Helsinki.
Subjects
A total of 150 subjects, all Caucasian, were recruited via advertisement on social media, including Facebook and the departmental site on the university intranet. Potential subjects were asked to complete a questionnaire that asked about sex, age, general health, and medications.
The exclusion criteria were as follows: 1. Smoking
2. Chronic medical illness such as high blood pressure and cardiac problems 3. The use of medications that might alter taste perception
4. Pregnancy 5. Food allergies
The inclusion criteria were as follows: 1. Age ≥ 18 years
2. Capable of understanding the study and providing informed consent
3. The presence of a tongue coating as evaluated using the Winkel Tongue Coating Index (WTCI) [14]; only subjects with a WTCI score ≥ 3 were included in the study
A total of 90 subjects (60%) met the inclusion criteria and were included in the study. The sample size was established by power analysis.
Experimental procedure
This was a single blind cross-sectional study. Measurements were performed just before lunchtime from 11.00-11.30 A.M in a quiet room to avoid environmental stimuli, and the subjects were asked to refrain from eating and drinking for at least one hour before the experiment. First, the presence of a tongue coating was scored in each sextant of the tongue using the WTCI: 0 = no coating, 1 = light coating, and 2 = heavy coating. The tongue coating index was obtained by adding the scores of the six sextants (score range: 0–12). Each subject was asked to rinse their mouth with water
for 30 seconds and was then blindfolded and asked to stick out their tongue. Subsequently, a taste stimulus was applied to the dorsal tongue surface. After 5 seconds, the subject was asked to score the perceived salt taste intensity from 1 to 10, with 1 indicating “not salty” and 10 indicating “extremely salty” [15, 16]. After the blindfold was removed, the subject was instructed to clean their tongue using a standard tongue cleaning device (Scrapy™, www.clevercool.com) [17] until the coating was completely dislodged. After a waiting period of 20 minutes to allow the tongue to recover from the cleaning, the subject was blindfolded again, and the stimulation procedure was repeated, as was the scoring.
Taste stimulus
The taste stimulus was a drop of tomato soup from a piece of filter paper (5 × 5 mm) that was soaked in prepared tomato soup and shaken to remove the excess soup. The stimulus was presented on the dorsal tongue surface approximately 1 cm in front of the sulcus terminalis. The soup was prepared from a commercially available dry soup packet (Knorr, Drinkbouillon Tomaat, Rotterdam, The Netherlands); the prepared soup contained 1.6 g NaCl (27%) per serving. The stimulus solution (soup) was prepared according to the manufacturer’s instructions by adding 175 ml of hot water to the dry contents of the packet, then the soup was allowed to cool to 45°C–50°C.
Statistical analysis
The taste intensity responses before and after the tongue cleaning intervention, the WTCI scores, and the subjects’ sex and age data were analyzed using the Statistical Package for the Social Sciences software (IBM SPSS Statistics 23). A p value < 0.05 was considered significant. The effect of removing the tongue coating on salty taste intensity was determined by calculating the differences between the pre- and post-intervention scores using the non-parametric Wilcoxon signed rank test. The effect of sex and age on outcome, i.e. on the difference between the pre- and post-intervention scores, was tested using linear regression analysis.
Results
A total of 90 subjects (29 males and 61 females) with a mean age of 45 years (sd, ±11.47 years; range 25–70 years) participated in the study. Statistical analysis of the effect of removing the tongue coating on salt taste intensity revealed a significant difference before versus after coating removal (p value = 0.0002). Notably, age and sex had no effect on this finding. Figure 1 shows the responses to the salty stimulus after tongue cleaning using a general Labeled Magnitude Scale (gLMS) according to sex.
CHAPTER 5
could change the perceived intensity of salt, it could be used to rapidly make lower salt concentrations more acceptably to people without changing the palatability of the food [13].
Materials and Methods
Ethical approval: The Medical Ethics Committee of the University Medical Center
Groningen approved the study protocol (reference number: METC 2015/601). Informed consent was obtained from all individual participants included in the study The study was conducted in accordance with all Dutch laws governing research ethics rules and principles and in accordance with the tenets of the Declaration of Helsinki.
Subjects
A total of 150 subjects, all Caucasian, were recruited via advertisement on social media, including Facebook and the departmental site on the university intranet. Potential subjects were asked to complete a questionnaire that asked about sex, age, general health, and medications.
The exclusion criteria were as follows: 1. Smoking
2. Chronic medical illness such as high blood pressure and cardiac problems 3. The use of medications that might alter taste perception
4. Pregnancy 5. Food allergies
The inclusion criteria were as follows: 1. Age ≥ 18 years
2. Capable of understanding the study and providing informed consent
3. The presence of a tongue coating as evaluated using the Winkel Tongue Coating Index (WTCI) [14]; only subjects with a WTCI score ≥ 3 were included in the study
A total of 90 subjects (60%) met the inclusion criteria and were included in the study. The sample size was established by power analysis.
Experimental procedure
This was a single blind cross-sectional study. Measurements were performed just before lunchtime from 11.00-11.30 A.M in a quiet room to avoid environmental stimuli, and the subjects were asked to refrain from eating and drinking for at least one hour before the experiment. First, the presence of a tongue coating was scored in each sextant of the tongue using the WTCI: 0 = no coating, 1 = light coating, and 2 = heavy coating. The tongue coating index was obtained by adding the scores of the six sextants (score range: 0–12). Each subject was asked to rinse their mouth with water
TONGUE COATING - TASTE
for 30 seconds and was then blindfolded and asked to stick out their tongue. Subsequently, a taste stimulus was applied to the dorsal tongue surface. After 5 seconds, the subject was asked to score the perceived salt taste intensity from 1 to 10, with 1 indicating “not salty” and 10 indicating “extremely salty” [15, 16]. After the blindfold was removed, the subject was instructed to clean their tongue using a standard tongue cleaning device (Scrapy™, www.clevercool.com) [17] until the coating was completely dislodged. After a waiting period of 20 minutes to allow the tongue to recover from the cleaning, the subject was blindfolded again, and the stimulation procedure was repeated, as was the scoring.
Taste stimulus
The taste stimulus was a drop of tomato soup from a piece of filter paper (5 × 5 mm) that was soaked in prepared tomato soup and shaken to remove the excess soup. The stimulus was presented on the dorsal tongue surface approximately 1 cm in front of the sulcus terminalis. The soup was prepared from a commercially available dry soup packet (Knorr, Drinkbouillon Tomaat, Rotterdam, The Netherlands); the prepared soup contained 1.6 g NaCl (27%) per serving. The stimulus solution (soup) was prepared according to the manufacturer’s instructions by adding 175 ml of hot water to the dry contents of the packet, then the soup was allowed to cool to 45°C–50°C.
Statistical analysis
The taste intensity responses before and after the tongue cleaning intervention, the WTCI scores, and the subjects’ sex and age data were analyzed using the Statistical Package for the Social Sciences software (IBM SPSS Statistics 23). A p value < 0.05 was considered significant. The effect of removing the tongue coating on salty taste intensity was determined by calculating the differences between the pre- and post-intervention scores using the non-parametric Wilcoxon signed rank test. The effect of sex and age on outcome, i.e. on the difference between the pre- and post-intervention scores, was tested using linear regression analysis.
Results
A total of 90 subjects (29 males and 61 females) with a mean age of 45 years (sd, ±11.47 years; range 25–70 years) participated in the study. Statistical analysis of the effect of removing the tongue coating on salt taste intensity revealed a significant difference before versus after coating removal (p value = 0.0002). Notably, age and sex had no effect on this finding. Figure 1 shows the responses to the salty stimulus after tongue cleaning using a general Labeled Magnitude Scale (gLMS) according to sex.
Fig.1 Perceived change in salt taste intensity in response to a salty stimulus (tomato soup) after tongue cleaning according to sex. Salt taste intensity was scored by the subjects using a general Labeled Magnitude Scale.
Discussion
This is the first study to show a significant change in the intensity of salt taste perception after tongue cleaning. A previous study showed an improvement in salt taste perception after tongue cleaning at the recognition threshold [12]. Figure 1 shows that most of the participants (65% of the males and 59% of the females) reported increased salt intensity perception after tongue cleaning. Notably, 21% of the males and 23% of the females did not report a change in perceived salt taste intensity after the removal of their tongue coating, and 14% of the males and 18% of the females reported a decrease in salt taste intensity perception.
Removing the tongue coating with a tongue scraper results in mechanical stimulation of the tongue, and mechanical stimulus contributes to taste perception. The participants self-cleaned their tongues, and they may have applied different levels of force. We assume that the application of different levels of force could have stimulated the trigeminal nerve in different ways or to different extents in different people, which could explain the differences in perceived taste intensity [18]. The inter-stimulus time of 20 minutes might also have influenced the findings. It is possible that this was too short to eliminate all of the effects of mechanical stimulus, such as tongue burning.
In the elderly, there is a tendency for the thickness of the coating to increase. Winkler et al. (1999) suggested removing the coating twice a day in geriatric patients to give them better taste perception [19]. For medical reasons, it is of major
importance to reduce salt intake in this group of patients. Our results demonstrate that cleaning the tongue is an easy way to improve salt perception.
Conclusion
We conclude that removing the tongue coating can change the perceived intensity of salty taste. We therefore recommend that people remove their tongue coating everyday in order to adapt to foods with lower salt concentrations. This could help reduce salt intake and thereby help people attain the level of salt intake recommended by the WHO.
Abbreviation: WHO: World health organization; WTCI: Winkel Tongue Coating Index; gLMS: general Labeled Magnitude Scale
Acknowledgement: The authors thank Professor. Arie Jan van Winkelhoff for his feedback on the manuscript. The work was supported by the Center for Dentistry and Oral Hygiene, University Medical Center Groningen, Groningen, The Netherlands. Author’s contributions: KS, FJ, EGW designed the study. KS and FA conducted the study; KS analyzed the data; KS and FJ drafted the manuscript. All authors read and approved the final manuscript.
Conflicts of interest: Author KS declares that she has no conflict of interest. Author FJ and Author FA declare that they have no conflict of interest. Author EGW is the co-owner of CleverCool BV.
References
1. Farquhar WB, Edwards DG, Jurkovitz CT, Weintraub WS (2015) Dietary sodium and health: More than just blood pressure. J Am Coll Cardiol 65:1042– 1050.
2. Organization World Health (2012) WHO | Sodium intake for adults and children. World Heal Organ 56.
3. Ekmekcioglu C, Blasche G, Dorner TE (2013) Too much salt and how we can get rid of it. Forsch Komplementmed 20:454–460.
4. He FJ, Campbell NRC, MacGregor GA (2012) Reducing salt intake to prevent hypertension and cardiovascular disease. Am J Public Health 32:293–300. 5. Dotsch M, Busch J, Batenburg M, et al (2009) Strategies to reduce sodium
consumption: A food industry perspective. Crit Rev Food Sci Nutr 49:841–851. 6. Sullivan SA, Birch LL (1990) Pass the sugar, pass the salt: Experience dictates
preference. Dev Psychol 26:546–551.
7. Ayya N, Beauchamp GK (1992) Short-term effects of diet on salt taste preference. Appetite 18:77–82.
CHAPTER 5
Fig.1 Perceived change in salt taste intensity in response to a salty stimulus (tomato soup) after tongue cleaning according to sex. Salt taste intensity was scored by the subjects using a general Labeled Magnitude Scale.
Discussion
This is the first study to show a significant change in the intensity of salt taste perception after tongue cleaning. A previous study showed an improvement in salt taste perception after tongue cleaning at the recognition threshold [12]. Figure 1 shows that most of the participants (65% of the males and 59% of the females) reported increased salt intensity perception after tongue cleaning. Notably, 21% of the males and 23% of the females did not report a change in perceived salt taste intensity after the removal of their tongue coating, and 14% of the males and 18% of the females reported a decrease in salt taste intensity perception.
Removing the tongue coating with a tongue scraper results in mechanical stimulation of the tongue, and mechanical stimulus contributes to taste perception. The participants self-cleaned their tongues, and they may have applied different levels of force. We assume that the application of different levels of force could have stimulated the trigeminal nerve in different ways or to different extents in different people, which could explain the differences in perceived taste intensity [18]. The inter-stimulus time of 20 minutes might also have influenced the findings. It is possible that this was too short to eliminate all of the effects of mechanical stimulus, such as tongue burning.
In the elderly, there is a tendency for the thickness of the coating to increase. Winkler et al. (1999) suggested removing the coating twice a day in geriatric patients to give them better taste perception [19]. For medical reasons, it is of major
TONGUE COATING - TASTE importance to reduce salt intake in this group of patients. Our results demonstrate that cleaning the tongue is an easy way to improve salt perception.
Conclusion
We conclude that removing the tongue coating can change the perceived intensity of salty taste. We therefore recommend that people remove their tongue coating everyday in order to adapt to foods with lower salt concentrations. This could help reduce salt intake and thereby help people attain the level of salt intake recommended by the WHO.
Abbreviation: WHO: World health organization; WTCI: Winkel Tongue Coating Index; gLMS: general Labeled Magnitude Scale
Acknowledgement: The authors thank Professor. Arie Jan van Winkelhoff for his feedback on the manuscript. The work was supported by the Center for Dentistry and Oral Hygiene, University Medical Center Groningen, Groningen, The Netherlands. Author’s contributions: KS, FJ, EGW designed the study. KS and FA conducted the study; KS analyzed the data; KS and FJ drafted the manuscript. All authors read and approved the final manuscript.
Conflicts of interest: Author KS declares that she has no conflict of interest. Author FJ and Author FA declare that they have no conflict of interest. Author EGW is the co-owner of CleverCool BV.
References
1. Farquhar WB, Edwards DG, Jurkovitz CT, Weintraub WS (2015) Dietary sodium and health: More than just blood pressure. J Am Coll Cardiol 65:1042– 1050.
2. Organization World Health (2012) WHO | Sodium intake for adults and children. World Heal Organ 56.
3. Ekmekcioglu C, Blasche G, Dorner TE (2013) Too much salt and how we can get rid of it. Forsch Komplementmed 20:454–460.
4. He FJ, Campbell NRC, MacGregor GA (2012) Reducing salt intake to prevent hypertension and cardiovascular disease. Am J Public Health 32:293–300. 5. Dotsch M, Busch J, Batenburg M, et al (2009) Strategies to reduce sodium
consumption: A food industry perspective. Crit Rev Food Sci Nutr 49:841–851. 6. Sullivan SA, Birch LL (1990) Pass the sugar, pass the salt: Experience dictates
preference. Dev Psychol 26:546–551.
7. Ayya N, Beauchamp GK (1992) Short-term effects of diet on salt taste preference. Appetite 18:77–82.
8. Trieu K, Neal B, Hawkes C, et al (2015) Salt reduction initiatives around the world - A systematic review of progress towards the global target. PLoS One 10:e0130247. doi: 10.1371/journal.pone.0130247
9. Prochaska JO, Velicer WF (1997) The transtheoretical model of health behavior change. Am J Heal Promot 12:38–48.
10. Scott T, Smith D (2003) Gustatory Neural Coding. Handbook of Olfaction and Gustation, second edition, Chapter 35 CRC Press. doi: 10.1201/9780203911457.ch35
11. Christensen GJ (1998) Why clean your tongue? J Am Dent Assoc 129:1605– 1607.
12. Quirynen M, Avontroodt P, Soers C, et al (2004) Impact of tongue cleansers on microbial load and taste. J Clin Periodontol 31:506–510.
13. Mattes RD (1997) The taste for salt in humans. Am J Clin Nutr 65:692S–697S. 14. Winkel EG, Roldán S, Van Winkelhoff AJ, et al (2003) Clinical effects of a
new mouthrinse containing chlorhexidine, cetylpyridinium chloride and zinc-lactate on oral halitosis. J Clin Periodontol 30:300–306.
15. Green BG, Dalton P, Cowart B, et al (1996) Evaluating the “Labeled Magnitude Scale” for measuring sensations of taste and smell. Chem Senses 21:323–34.
16. White TL, Hornung DE, Kurtz DB, et al (1998) Phonological and perceptual components of short-term memory for odors. Am J Psychol 111:411–434. 17. Beekmans DG, Slot DE, Van der Weijden GA (2016) User perception on
various designs of tongue scrapers: an observational survey. Int J Dent Hyg. doi: 10.1111/idh.12204
18. Forde CG, Cantau B, Delahunty CM, Elsner RJ (2002) Interactions between texture and trigeminal stimulus in a liquid food system: effects on elderly consumers preferences. J Nutr Health Aging 6:130–133.
19. Winkler S, Garg AK, Mekayarajjananonth T, et al (1999) Depressed taste and smell in geriatric patients. J Am Dent Assoc 130:1759–1765.
CHAPTER 5
8. Trieu K, Neal B, Hawkes C, et al (2015) Salt reduction initiatives around the world - A systematic review of progress towards the global target. PLoS One 10:e0130247. doi: 10.1371/journal.pone.0130247
9. Prochaska JO, Velicer WF (1997) The transtheoretical model of health behavior change. Am J Heal Promot 12:38–48.
10. Scott T, Smith D (2003) Gustatory Neural Coding. Handbook of Olfaction and Gustation, second edition, Chapter 35 CRC Press. doi: 10.1201/9780203911457.ch35
11. Christensen GJ (1998) Why clean your tongue? J Am Dent Assoc 129:1605– 1607.
12. Quirynen M, Avontroodt P, Soers C, et al (2004) Impact of tongue cleansers on microbial load and taste. J Clin Periodontol 31:506–510.
13. Mattes RD (1997) The taste for salt in humans. Am J Clin Nutr 65:692S–697S. 14. Winkel EG, Roldán S, Van Winkelhoff AJ, et al (2003) Clinical effects of a
new mouthrinse containing chlorhexidine, cetylpyridinium chloride and zinc-lactate on oral halitosis. J Clin Periodontol 30:300–306.
15. Green BG, Dalton P, Cowart B, et al (1996) Evaluating the “Labeled Magnitude Scale” for measuring sensations of taste and smell. Chem Senses 21:323–34.
16. White TL, Hornung DE, Kurtz DB, et al (1998) Phonological and perceptual components of short-term memory for odors. Am J Psychol 111:411–434. 17. Beekmans DG, Slot DE, Van der Weijden GA (2016) User perception on
various designs of tongue scrapers: an observational survey. Int J Dent Hyg. doi: 10.1111/idh.12204
18. Forde CG, Cantau B, Delahunty CM, Elsner RJ (2002) Interactions between texture and trigeminal stimulus in a liquid food system: effects on elderly consumers preferences. J Nutr Health Aging 6:130–133.
19. Winkler S, Garg AK, Mekayarajjananonth T, et al (1999) Depressed taste and smell in geriatric patients. J Am Dent Assoc 130:1759–1765.
