Dental Science - Review Article Gustatory dysfunction T. Maheswaran, P. Abikshyeet1, G. Sitra2, S. Gokulanathan3, V. Vaithiyanadane4, S. Jeelani2 Department of ABSTRACT Oral Pathology and Tastes in humans provide a vital tool for screening soluble chemicals for food evaluation, selection, and avoidance Microbiology, Vivekanandha Dental College for of potentially toxic substances. Taste or gustatory dysfunctions are implicated in loss of appetite, unintended Women, Elayampalayam, weight loss, malnutrition, and reduced quality of life. Dental practitioners are often the first clinicians to be Tiruchengode, 1Kalinga presented with complaints about taste dysfunction. This brief review provides a summary of the common causes Institute of Dental Sciences, of taste disorders, problems associated with assessing taste function in a clinical setting and management Bhubaneswar, 2Oral options available to the dental practitioner. Medicine and Radiology, Indira Gandhi Institute of Dental Sciences, Puducherry, 3Periodontics, Vivekanandha Dental College for Women, Elayampalayam, Tiruchengode, 4Physiology, Vivekanandha Dental College for Women, Elayampalayam, Tiruchengode, India Address for correspondence: Dr. T. Maheswaran, E-mail: maheswaranmds@ yahoo.in Received : 30-03-14 Review completed : 30-03-14 Accepted : 09-04-14 KEY WORDS: Ageusia, dysgeusia, hypergeusia, hypogeusia, phantogeusia, taste disorders, taste disturbances he chemosensory functions of taste and smell play a vital report increased use of sugar and salt to compensate for T role in human physiology. They determine the flavor and diminished sense of taste, a practice that is detrimental to those palatability of foods and beverages, the selection of nutrients with diabetes mellitus or hypertension.[2] essential for life, and the warning of toxic vapors, fire, and spoiled foodstuffs. Chemosensory dysfunctions have serious Anatomy and Physiology of Taste implications for the preservation of oral and systemic health, with dramatic effects on quality-of-life.[1] Patients frequently The specialized sense organ for taste (gustation) consists of approximately 10,000 taste buds, which are ovoid bodies Access this article online measuring 50-70 µm. There are four morphologically Quick Response Code: Website: distinct types of cells within each taste bud: Basal cells, www.jpbsonline.org dark cells (Type I), light cells (Type II), and intermediate cells (Type III). Basal cells do not extend processes into the DOI: taste pore and are likely to be undifferentiated or immature 10.4103/0975-7406.137257 taste cells. The later three cell types are sensory neurons that respond to taste stimuli or tastants. In humans, the taste buds How to cite this article: Maheswaran T, Abikshyeet P, Sitra G, Gokulanathan S, Vaithiyanadane V, Jeelani S. Gustatory dysfunction. J Pharm Bioall Sci 2014;6:S30-3. S30 Journal of Pharmacy and Bioallied Sciences July 2014 Vol 6 Supplement 1 Maheswaran, et al.: Gustatory dysfunction are located in the mucosa of the epiglottis, palate, and pharynx pathways, and neurotransmitters) results in altered taste and in the walls of the papillae of the tongue.[3] Each taste bud perception at any age. The mechanistic cause of gustatory has receptors at the apical portion exposed to the oral cavity dysfunction can be of three types: Transport, sensory or neuronal and a basolateral area separated by a tight junction.[1] Taste problem [Table 1].[1] Drug-induced taste disorder was found buds across the oral cavity serve similar functions. Although, to be the most common etiology among the patients visiting there are subtle regional differences in sensitivity to different a taste clinic in Japan [Table 2].[13] The drug interactions and tastants, the concept of a “tongue map” defining distinct zones side-effects index lists over 200 drugs with chemosensory for sweet, bitter, salty, and sour has largely been discredited.[4] dysfunction. A partial list of these medications affecting taste Taste sensation can be evoked by a diverse group of chemicals is shown in Table 3.[14] ranging from simple ions (H+, Na+) to inorganic molecules to carbohydrates and complex proteins.[5] Oral sources of altered taste function are common and can be evaluated by a dentist. Trauma (burns, lacerations, surgery, Taste modalities generally fall into five established basic tastes and local anesthesia), local antiplaque medicaments and drugs according to the receptor type most strongly activated: Sweet, excreted into saliva, infections (dentoalveolar, periodontal, sour, salty, bitter, and umami.[6] Accumulating evidence suggest soft tissue), vesiculobullous conditions, removable prostheses, a taste component for free fatty acids in humans as the sixth metallic dental restorations, and salivary dysfunction can modality of taste.[7] The sensory nerve fibers from the taste directly or indirectly affect taste function.[1] Gastroesophageal receptors reach the gustatory nucleus of the medulla oblongata by VII, IX, and X cranial nerves. From there, the signals reach Table 1: Mechanistic cause of gustatory dysfunction[1] the ventral posteromedial nucleus of the thalamus through the Disorder Description Examples axons of the second order neurons. From the thalamus, the third order neurons reach the gustatory cortex.[3] Transport Stimulus cannot Salivary dysfunction, oral problem reach the receptor candidiasis Sensory Damage to peripheral Radiotherapy, Taste is also commonly confused with somatosensory sensations problem sensory organs chemotherapy, burn, trauma such as the cool of menthol or the heat of chili peppers Neuronal Damage to peripheral Tongue surgery, neoplasm, perceived through trigeminal nerve. The capacity of cutaneous, problem nerves or CNS brain tumor including trigeminal, glossopharyngeal (IX cranial), and vagal CNS: Central nervous system (X cranial) nerve fiber endings, to detect chemicals is known as chemesthesis or cutaneous chemosensation. Oral chemesthesis Table 2: Etiology of gustatory dysfunction in 2,278 patients[13] explains the pungent or sharp feel of many different foods and spices such as chili peppers, horseradish, the coolness of Cause Total no. Percentage peppermint, the tingle of carbonated drinks, and the irritation Drug-induced 495 21.7 produced by substances such as raw garlic extracts.[8] Idiopathic 341 15.0 Zinc deficiency 330 14.5 Psychogenetic 243 10.7 Terminologies Flavor disorder 171 7.5 Systematic disease 169 7.4 Smell or olfaction is the perception of odor by the nose, whereas Oral disease 146 6.4 Postinfluenza taste and smell disorder 60 2.6 taste or gustation is the perception of salty, sweet, sour, or bitter Peripheral nerve disorder 59 2.6 by the tongue. Flavor is the combination of taste, smell, and CNS disorder 38 1.7 trigeminal sensation. Trigeminal stimulation (pain, tactile, Endocrine disorder 23 1 and temperature) contributes to flavor perception throughout Other 203 8.9 the eating process.[1] Gustatory dysfunctions are classified Total 2278 100 as quantitative or qualitative disorders.[9] Quantitative taste CNS: Central nervous system disorder include ageusia, hypogeusia and hypergeusia, while qualitative disorders are dysgeusia and phantogeusia. Ageusia Table 3: Drugs causing gustatory dysfunction[14] is an absence of the sense of taste; hypogeusia is a decreased sensitivity to all tastants.[10] Hyperguesia refers to enhanced Class Agents gustatory sensitivity.[11] Dysgeusia or pargeusia is an unpleasant Antibiotics Ampicillin, macrolides, metronidazole, quinolones, sulfamethoxazole, trimethoprim, and tetracycline perception of a tastant and phantogeusia, is a perception of taste Neurologic Antiparkinsonians, CNS stimulants, migraine [3,10] that occurs in the absence of a tastant. medications medications, and muscle relaxants Cardiac medications Many antihypertensives, diuretics, statins, Etiology antiarrhythmics Endocrine medications Most thyroid medications Psychotropics Most tricyclic antidepressants, some Majority of the gustatory dysfunctions are caused by impairment antipsychotics, anxiolytics, mood stabilizers, and of smell rather than taste perception. The most common hypnotics causes of olfactory dysfunction include allergic rhinitis, chronic Other Antihistamines, antineoplastics, bronchodilators, rhinosinusitis and upper respiratory infection.[12] Any condition anti-inflammatories, smoking cessation aids, that results in a compromised environment for the mediators antifungals, and antivirals of chemosensation (e.g. tongue, saliva, oral mucosa, neural CNS: Central nervous system Journal of Pharmacy and Bioallied Sciences July 2014 Vol 6 Supplement 1 S31 Maheswaran, et al.: Gustatory dysfunction reflux disease can produce apparent phantogeusia, which requested to assess the quality and intensity of the taste.[16] may be intermittent or persistent and are often described Other test methods are based on presenting the stimuli in the as sour.[15] form of a tastant-saturated filter paper or so-called taste strips with the dried tastants – the task of the patient is to identify Systemic conditions such as diabetes mellitus, pernicious the taste. When compared to taste solution, taste strips have anemia, Sjogren syndrome and Crohn’s disease are also known the advantage of a long shelf life.[11] to cause gustatory dysfunction.[16] Radiation therapy can injure the taste buds, transmitting nerves, and salivary glands, resulting For evaluation of a gustatory dysfunction, one can apply a topical in gustatory dysfunction.[16] Zinc deficiency is responsible