Have you ever had a patient who complains about everything that you use in their mouth during a dental appointment? Are they often bothered by the normal scents in your dental office? Perhaps they complain about the smell of disinfectant, the scent of a drill as it cuts tooth structure or maybe tactile stimulation such as the saliva ejector or possibly the placement of cotton rolls? The patient may complain about the highly flavoured taste of fluoride to the extent it is almost intolerable and they may exhibit a gag reflex when a flavoured prophy paste is used? Any dental products that are used in tooth restoration preparation, etc. may be profoundly objectionable to such patients. Perhaps you may be treating what is termed a patient who is a Supertaster! Or perhaps these characteristics remind you of a relative or even yourself. Could you be a supertaster?
So what is a supertaster? Supertasters are defined as a subgroup of individuals who are genetically programmed with a bitter receptor gene (TAS2R38). In testing for the supertaster status, the patient will report intense bitterness, specifically from the chemical propylthiouracil (PROP) and phenylthiocarbamide (PTC). Supertasters are genetically programmed to react to “bitter” taste and find food sources that are on the bitter side highly objectionable. See Appendix 1 for a list of foods that supertasters “like” and “dislike.” PROP is usually the chemical that is used since it is the least bitter and also the safest.10 Supertasters are also more sensitive to fats and sweet foods with a tendency to avoid these types of foods. According to previous research studies, approximately 25% of the population may fall into this category of a supertaster. Most of the world’s general population tends to fall into a middle category, (sometimes referred to as a General Taster) 50% and at the other end of the spectrum are the non-tasters (sometimes called sub-tasters) that account for the other 25%. Non-tasters are opposites on a continuum with supertasters and find sugar, fat and sweeter foods more favorable.
It is interesting that individuals do not taste products to the same extent, nor do we all experience scents with the same intensity. The sense of smell and taste are highly linked. The sense of smell is also a developed one, and we react to certain scents after being exposed to them in a prior experience with some being pleasant and others unpleasant. Our thoughts and emotions become associated with these scents of the past. Within the United States, roughly 25% of the population who are known to be supertasters are women, Asians and African-Americans. The mid-range of the population (approximately 50%) fall into a central category between the two extremes. The taste perception of these individuals may also vary depending upon the number and size of the individual’s own taste buds and receptors. There are ranges within each of these categories. Since most people have not heard of supertasters, it is probably safe to say these percentages may be considered estimates. The percentages are based on previous studies of select groups, and this is discussed in more depth within this article.
Taste and smell are intertwined. The NIH estimates over 200,000 individuals visit a physician yearly because of chemosensory problems such as taste disorders and many more go undiagnosed, but the patient may complain about taste and smell issues. Patients report surprise when they find that taste and most flavours are recognised through the sense of smell.24,25 Because of this association, many supertasters cannot tolerate certain scents such as perfumes, scented lipsticks or, as mentioned previously, the scents in a dental office. So why is the designation of a supertaster important to the dental professional? Some disease states result in the total loss of the ability to detect an odour (anosmia) or the reduced ability to smell (hyposmia) along with these changes, a loss of taste (ageusia) may also suggest a disease state such as Parkinson’s Disease. We continue to learn about these connections in taste or smell and their relation to serious disease states.35,36 Rhinosinusitis is a common disorder accounting for an estimated 13 million physician office visits in the United States each year. It is known to have contributing factors such as genetics, environmental exposures, and impaired mucociliary clearance. Rhinosinusitis is associated with a poorer quality of life and may encompass a loss in the sense of smell over time, sinus/nasal surgeries, plus many office visits. Recent studies by Adappa, et al.40 sought to determine if a correlation between T2R38 phenotype and in vitro biofilm formation existed.39 The researchers found a correlation with bitter taste receptor T2R38 and decreased function in nonpolypoid chronic rhinosinusitis that may make patients more susceptible to sinonasal infections.
Although supertasters have some tendencies toward a few health concerns, and, according to current research, they may also be more protected from other disease states such as dental caries while sub-tasters are more prone to dental caries and even obesity because of their food choices (e.g., sugar and fats). Supertasters reportably use more salt and eat less vegetables because of their aversion to bitter tastes and this may predispose them to heart disease and to colon cancer.
Supertasters are found more often in women, and women tend to have more fungiform papillae than men. Women also perceive more oral burn from mouth irritants.3 Since supertasters are genetically programmed, these tendencies to prefer certain foods may be observed in young children and may answer some age-old questions as to why my child will not eat certain foods or why the child is a “picky eater!” With our youth, who are susceptible to dental decay, obesity and even diabetes, this deserves considerable research now and in the future. Obesity rates continue to rise in the United States, and the current generation may be the first to have a shortened life span compared to their parents because of chronic diseases related to being overweight. From a dental perspective, their food choices may affect the oral tissues, future oral disease states and the teeth long-term. This course also gives the practitioner a better understanding of why some products used in the dental practice cause discomfort for the patient.
Figure 2. Closer view of a supertaster tongue.
Figure 3. Unstained tongue: large fungiform papillae visible.
Studies by Melis et al. evaluated the density and morphology of fungiform papilla along with the gene that controls the salivary trophic factor known as gustin. Gustin has been described as a trophic factor responsible for the growth and maintenance of taste buds. In the study by Melis, the higher the taste intensity of the supertasters on a scale determined by the researchers, the greater the density of the fungiform papillae.23 The fungiform papillae can be counted within a small area of the tongue after being stained with a blue dye or blue food colouring (Figures 4 and 5). The filiform will stain blue and the fungiform will retain a pink colour making them appear more prominent.
Figure 5. Supertaster with stained tongue.
The higher numbers of fungiform papillae can be associated with those numbers found in supertasters. The density is determined by more sophisticated histology and microscope procedures. Other simple tests can be performed such as the PROP or PTC tests that will be discussed later in this course. These tests are used to differentiate a supertaster from a non-taster or from the rest of the general population. Another indicator that assists in confirming a supertaster is to count the number of fungiform papillae in a designated area on the tongue after staining the tongue so the fungiform papillae are more distinct (Figures 6-10). The authors believe that since the numbers do vary greatly, the most accurate way to determine the supertaster is by using a genetic test or by using the PROP test strips.
Figure 7. Blue stain on tongue of a supertaster.
On average, supertasters will have noticeable fungiform papillae numbering 35, average tasters will have between 15 and 35 and non-tasters will have less than 15 papillae (Figure 9). The numbers will vary with different researchers. There is some thought that the numbers vary with some patients who use this technique and that it is too subjective. Eldeghaidy, et al. 2018, expands on the numbers of fungiform by an automated technique of counting the fungiform rather than a manual calculation. The researchers suggest that this technique is a more reliable quantification in numbers over the anterior surface of the tongue in supertasters who tested for PROP.38 It is known that the larger the fungiform, the more taste bud receptors the patient may have orally; therefore, the intensity of taste may increase with an increase of the receptors. The procedure of staining in the clinic does give the patient an opportunity to witness the appearance of the fungiform papillae as the clinician educates them about taste. Some studies have concentrated on small areas of the tongue and taste buds/receptors are throughout the mouth, so data has been very mixed with regard to the relationship of supertasters and numbers of fungiform papillae.
The three ways to evaluate a supertaster would be (1) genetic testing, (2) use of the PROP test and (3) clinically evaluating the fungiform papillae for size and number. Genetic testing is the most reliable way to confirm a supertaster. However, the PROP test is easy and very immediate.
The tongue is an important structure in the mouth and is a predictor of many disease states. It has been used for hundreds of years in Chinese medicine as an indicator of overall health and is one of the first structures someone who practices Chinese medicine will evaluate in a clinical examination.8 The tongue is covered with papillae containing numerous taste buds that are sensitive to the chemicals ingested in both food and drink. When these chemicals are dissolved in saliva, the specialized gustatory cells react to the chemicals (chemosensory acuity is heightened in supertasters). The receptor cells activate sensory neurons that are part of the facial and glossopharyngeal nerves (Figure 11).
Injury to the nerve supply may affect the taste sensations of the individual. So when a taste nerve is injured, taste may be affected. For instance if damage occurs to the chorda tympani in middle ear surgery, taste may be altered (Figure 11). Taste receptors are innervated by the chorda tympani branch of the facial nerve and oral burn receptors are innervated by the trigeminal nerve.4 Taste buds are surrounded by trigeminal fibres. Supertasters have more taste buds and are susceptible to more nerve fibre stimulation. A supertaster is described as someone who has an abundance of fungiform papillae as opposed to the “general tasters” and “sub-tasters” who have much fewer fungiform in number and density. Therefore, fewer taste buds may produce a decreased sense of taste. Taste is perceived in the brain via the nerves. Taste receptors actually are throughout the entire gut as well as the oral cavity. The entire tongue has abundant taste buds, and the fungiform papillae are most abundant in the anterior two thirds of the tongue. The taste buds have taste receptors that last about 10 days and are steadily replaced by the basal cells. The sister cells become a supporting cell and ultimately, a taste receptor cell (Figure 11).
Supertasters tend to enjoy foods that are relatively bland and non-spicy foods are preferred. Higher rates of supertasters are more likely to suffer from Burning Mouth Syndrome (BMS) in later life.
Sub-tasters or non-tasters, on the other end of the spectrum, have fewer fungiform papillae, in the anterior tongue region and are more likely to enjoy very spicy foods as they can better tolerate the nerve input since they also have fewer taste receptors and/or taste buds. The non-tasters, therefore, are also less likely to have BMS while the supertasters are believed to have higher rates of BMS. Orally, taste buds are receptors of taste and occur on the tongue, soft palate, pharynx and epiglottis. Early in life we have as many as 10,000 taste buds but these decrease with age. Each taste bud consists of three kinds of cells: basal cells, supporting cells and gustatory receptor cells. Supporting cells contain microvilli and gustatory receptor cells. In order to detect taste, the taste buds contain a taste pore with an opening allowing the gustatory hair to extend to the external surface (Figure 12).
A patient may complain of specific taste changes or changes in taste perception with no obvious stimulus. This is referred to as “taste phantom” and the patient may also complain of a “metallic or bitter” taste. Interestingly, patients who have BMS often voice this complaint of taste change.27 A retrospective study by Fark et al., presented study results of 4,680 patients and 491 exhibited taste disorders. The most frequent cause of disorders was posttraumatic injury (24%), postoperative (15%) but 34% were termed idiopathic and often BMS falls into this category. Those who were idiopathic and postoperative complained mainly of taste sensations of bitter, salty and sour taste. Fark points out taste is primarily related to the input from three different sensory systems: retronasal olfaction, mechano and chemo sensitivity via the trigeminal nerve and the gustatory system.11 Taste sensation is very complicated and patients with long-term complaints usually are referred to a taste and smell clinic that specializes in assisting the individual in assessing and eliminating the offending taste or smell problem. For a list of Smell and Taste Clinics in the United States see Appendix 2.