Certain diagnostic tools can also be used to help determine the extent of dysgeusia. Electrophysiological tests and simple reflex tests may be applied to identify abnormalities in the nerve-to-brainstem pathways. For example, the blink reflex may be used to evaluate the integrity of the trigeminal nerve–pontine brainstem–facial nerve pathway, which may play a role in gustatory function.

Structural imaging is routinely used to investigate lesions in the taste pathway. Magnetic resonance imaging allows direct visualization of the cranial nerves. Furthermore, it provides significant information about the type and cause of a lesion. Analysis of mucosal blood flow in the oral cavity in combination with the assessment of autonomous cardiovascular factors appears to be useful in the diagnosis of autonomic nervous system disorders in burning mouth syndrome and in patients with inborn disorders, both of which are associated with gustatory dysfunction. Cell cultures may also be used when fungal or bacterial infections are suspected.

In addition, the analysis of saliva should be performed, as it constitutes the environment of taste receptors, including transport of tastes to the receptor and protection of the taste receptor. Typical clinical investigations involve sialometry and sialochemistry. Studies have shown that electron micrographs of taste receptors obtained from saliva samples indicate pathological changes in the taste buds of patients with dysgeusia and other gustatory disorders.

In order to further classify the extent of dysgeusia and clinically measure the sense of taste, gustatory testing may be performed. Gustatory testing is performed either as a whole-mouth procedure or as a regional test. In both techniques, natural or electrical stimuli can be used. In regional testing, 20 to 50 µL of liquid stimulus is presented to the anterior and posterior tongue using a pipette, soaked filter-paper disks, or cotton swabs. In whole mouth testing, small quantities (2-10 mL) of solution are administered, and the patient is asked to swish the solution around in the mouth.

Threshold tests for sucrose (sweet), citric acid (sour), sodium chloride (salty), and quinine or caffeine (bitter) are frequently performed with natural stimuli. One of the most frequently used techniques is the "three-drop test." In this test, three drops of liquid are presented to the subject. One of the drops is of the taste stimulus, and the other two drops are pure water. Threshold is defined as the concentration at which the patient identifies the taste correctly three times in a row.

Suprathreshold tests, which provide intensities of taste stimuli above threshold levels, are used to assess the patient's ability to differentiate between different intensities of taste and to estimate the magnitude of suprathreshold loss of taste. From these tests, ratings of pleasantness can be obtained using either the direct scaling or magnitude matching method and may be of value in the diagnosis of dysgeusia. Direct scaling tests show the ability to discriminate among different intensities of stimuli and whether a stimulus of one quality (sweet) is stronger or weaker than a stimulus of another quality (sour). Direct scaling cannot be used to determine if a taste stimulus is being perceived at abnormal levels. In this case, magnitude matching is used, in which a patient is asked to rate the intensities of taste stimuli and stimuli of another sensory system, such as the loudness of a tone, on a similar scale. For example, the Connecticut Chemosensory Clinical Research Center asks patients to rate the intensities of NaCl, sucrose, citric acid and quinine-HCl stimuli, and the loudness of 1000 Hz tones. Assuming normal hearing, the results of this cross-sensory test show the relative strength of the sense of taste in relation to the loudness of the auditory stimulus. Although many of the tests are based on ratings using the direct scaling method, some tests do use the magnitude-matching procedure.

Other tests include identification or discrimination of common taste substances. Topical anesthesia of the tongue has been reported to be of use in the diagnosis of dysgeusia as well, since it has been shown to relieve the symptoms of dysgeusia temporarily. In addition to techniques based on the administration of chemicals to the tongue, electrogustometry is frequently used. It is based on the induction of gustatory sensations by means of an anodal electrical direct current. Patients usually report sour or metallic sensations similar to those associated with touching both poles of a live battery to the tongue. Although electrogustometry is widely used, there seems to be a poor correlation between electrically and chemically induced sensations.

BMS is a diagnosis of exclusion, i.e. all other explanations for the symptoms are ruled out before the diagnosis is made. There are no clinically useful investigations that would help to support a diagnosis of BMS (by definition all tests would have normal results), but blood tests and / or urinalysis may be useful to rule out anemia, deficiency states, hypothyroidism and diabetes. Investigation of a dry mouth symptom may involve sialometry, which objectively determines if there is any reduction of the salivary flow rate (hyposalivation). Oral candidiasis can be tested for with use of a swabs, smears, an oral rinse or saliva samples. It has been suggested that allergy testing ("e.g.", patch test) is inappropriate in the absence of a clear history and clinical signs in people with a burning sensation in the mouth. The diagnosis of a people with a burning symptom may also involve psychologic screening e.g. depression questionnaires.

The second edition of the International Classification of Headache Disorders lists diagnostic criteria for "Glossodynia and Sore Mouth":

BMS is benign (importantly, it is not a symptom of oral cancer), but as a cause of chronic pain which is poorly controlled, it can detriment quality of life, and may become a fixation which cannot be ignored, thus interfering with work and other daily activities. Two thirds of people with BMS have a spontaneous partial recovery six to seven years after the initial onset, but in others the condition is permanent. Recovery is often preceded by a change in the character of the symptom from constant to intermittent. No clinical factors predicting recovery have been noted.

If there is an identifiable cause for the burning sensation (i.e. primary BMS), then psychologic dysfunctions such as anxiety and depression often disappear if the symptom is successfully treated.

The diagnosis of DH may be challenging. It is a diagnosis of exclusion, reached once all other possible explanations for the pain have been ruled out. A thorough patient history and clinical examination are required. The examination includes a pain provocation test by blasting air from a dental instrument onto the sensitive area, or gentle scratching with a dental probe. If a negative result for the pain provocation test occurs, no treatment for dentinal hypersensitivity is indicated and another diagnosis should be sought, such as other causes of orofacial pain.

Inflammation of the dental pulp, termed pulpitis, produces true hypersensitivity of the nerves in the dental pulp. Pulpitis is classified as "irreversible" when pulpal inflammation will irreversibly progress to pulpal necrosis due to compression of the venous microcirculation and tissue ischemia, and "reversible" when the pulp is still capable of returning to a healthy, non-inflamed state, although usually dental treatment is required for this. Irreversible pulpitis is readily distinguishable from DH. There is poorly localized, severe pain which is aggravated by thermal stimuli, and which continues after the stimulus is removed. There also is typically spontaneous pain without any stimulus. Reversible pulpitis may not be so readily distinguishable from DH, however usually there will be some obvious sign such as a carious cavity, crack, etc. which indicates pulpitis. In contrast to pulpitis, the pain of DH is short and sharp.

Dentin hypersensitivity may affect individuals' quality of life. Over time, the dentin-pulp complex may adapt to the decreased insulation by laying down tertiary dentin, thereby increasing the thickness between the pulp and the exposed dentin surface and lessening the symptoms of hypersensitivity. Similar process such as formation of a smear layer (e.g. from toothbrushing) and dentin sclerosis. These physiologic repair mechanisms are likely to occur with or without any form of treatment, but they take time.

"Relative dentin abrasivity" ("RDA") is a standardised measurement of the abrasive effect that the components of the toothpaste have on a tooth.

The RDA scale was developed by the American Dental Association (ADA). The RDA scale compares toothpaste abrasivity to standard abrasive materials and measures the depth of cut at an average of 1 millimetre per 100,000 brush strokes onto dentine. This comparison generates abrasive values for the dentifrices that would be safe for daily use. In vitro dental studies showed a positive correlation between the highest RDAs and greater dentin wear.

Since 1998, the RDA value is set by the standards DIN EN ISO 11609. Currently, the claim on products such as toothpaste are not regulated by law, however a dentifrice is required to have a level lower than 250 to be considered safe and before being given the ADA seal of approval. The values obtained depend on the size, quantity and surface structure of abrasive used in toothpastes.

While the RDA score has been shown to have a statistically significant correlation to the presence of abrasion, it is not the only contributing factor to consider. Other factors such as the amount of pressure used whilst brushing, the type, thickness and dispersion of bristle in the toothbrush and the time spent brushing are other factors that contribute to dental abrasion.

X-ray/CT scan taken from the TMJ to see if there is any damage to the TMJ and surrounding structures.

Diagnosis of otodental syndrome was established using clinical, histopathological and audiometric methodologies. In normal individuals, by the age of 2-3, radiograph images should depict any signs of premolar development. A formal diagnosis of no premolar growth can be done by age 6 in order to check for signs of otodental syndrome. Sensorineural hearing loss can be another measure for proper diagnosis as well as checking for ocular coloboma. The latter is usually noticed at an around birth.

Molecular genetic testing can aid in the diagnosis of the affected individual, which would determine if there are any abnormalities in the FGF3 gene (11q13) or the FADD gene (11q13.3). Additional tests that can help diagnose otodental syndrome are ear infection tests, hearing tests, oral examination, and eye examinations to check for the specific phenotypic associations. Due to the rarity of otodental syndrome, most symptoms are looked at on an individual basis unless multiple symptoms are all apparent at once.

There is potential for differential diagnosis due to similarities in symptoms. Other diseases that share common symptoms are chondroectodermal dysplasia, achondrodysplasia, and osteopetrosis

Electromagnetic hypersensitivity is not an accepted diagnosis; medically there is no case definition or clinical practice guideline and there is no specific test to identify it, nor is there an agreed-upon definition with which to conduct clinical research.

Complaints of electromagnetic hypersensitivity may mask organic or psychiatric illness. Diagnosis of those underlying conditions involves investigating and identifying possible known medical causes of any symptoms observed. It may require both a thorough medical evaluation to identify and treat any specific conditions that may be responsible for the symptoms, and a psychological evaluation to identify alternative psychiatric/psychological conditions that may be responsible or contribute to the symptoms.

Symptoms may also be brought on by imagining that exposure is causing harm, an example of the nocebo effect. Studies have shown that reports of symptoms are more closely associated with belief that one is being exposed than with any actual exposure.

Rarely, trismus is a symptom of nasopharyngeal or infratemporal tumors/ fibrosis of temporalis tendon, when patient has limited mouth opening, always premalignant conditions like oral submucous fibrosis (OSMF) should also be considered in differential diagnosis.

In response to a WHO call for papers at the 5th Paris Appeal Congress of Environmental Idiopathic Intolerance conference that took place in Belgium on the 18th of May, a report that was generally supportive quoted a number of international practitioners. This was provisionally accepted by the Spanish health ministry, and later found proven by a judge in the case of a plumber in the Province of Castellón

MCS is a diagnosis of exclusion, and the first step in diagnosing a potential MCS sufferer is to identify and treat all other conditions which are present and which often explain the reported symptoms. For example, depression, allergy, thyroid disorders, orthostatic syndromes, lupus, hypercalcemia, and anxiety need to be carefully evaluated and, if present, properly treated. The "gold standard" procedure for identifying a person who has MCS is to test response to the random introduction of chemicals the patient has self-identified as relevant. This may be done in a carefully designed challenge booth to eliminate the possibility of contaminants in the room. Chemicals and controls, sometimes called prompts, are introduced in a random method, usually scent-masked. The test subject does not know when a prompt is being given. Objective and subjective responses are measured. Objective measures, such as the galvanic skin response indicate psychological arousal, such as fear, anxiety, or anger. Subjective responses include patient self-reports. A diagnosis of MCS can only be justified when the subject cannot consciously distinguish between chemicals and controls, and when responses are consistently present with exposure to chemicals and consistently absent when prompted by a control.

A 1999 consensus statement recommends that MCS be diagnosed according to six standardized criteria:

1. Symptoms are reproducible with repeated (chemical) exposures

2. The condition has persisted for a significant period of time

3. Low levels of exposure (lower than previously or commonly tolerated) result in manifestations of the syndrome ("i.e." increased sensitivity)

4. The symptoms improve or resolve completely when the triggering chemicals are removed

5. Responses often occur to multiple chemically unrelated substances

6. Symptoms involve multiple-organ symptoms (runny nose, itchy eyes, headache, scratchy throat, ear ache, scalp pain, mental confusion or sleepiness, palpitations of the heart, upset stomach, nausea and/or diarrhea, abdominal cramping, aching joints).

In various studies, about one half of the patients who seek medical treatment for symptoms of MCS meet the criteria for depressive and anxiety disorders. Because many people eliminate whole categories of food in an effort to reduce symptoms, a complete review of the patient's diet may be needed to avoid nutritional deficiencies.

In order for successful treatment of abrasion to occur, the aetiology first needs to be identified. The most accurate way of doing so is completing a thorough medical, dental, social and diet history. All aspects needs to be investigated as in many cases the cause of abrasion can be multi-factorial. Once a definitive diagnosis is completed the appropriate treatment can commence.

Treatment for abrasion can present in varying difficulties depending on the current degree or progress caused by the abrasion. Abrasion often presents in conjunction with other dental conditions such as attrition, decay and erosion however the below treatment is for abrasion alone. Successful treatment focuses on the prevention and progression on the condition and modifies the current habit/s instigating the condition.

A 2006 systematic review and a 2005 review by the UK Health Protection Agency each evaluated the evidence for various medical, psychological, behavioral, and alternative treatments for EHS and each found that the evidence-base was limited and not generalizable. The conclusion of the 2006 review stated: "The evidence base concerning treatment options for electromagnetic hypersensitivity is limited and more research is needed before any definitive clinical recommendations can be made. However, the best evidence currently available suggests that cognitive behavioural therapy is effective for patients who report being hypersensitive to weak electromagnetic fields."

As of 2005, WHO recommended that people presenting with claims of EHS be evaluated to determine if they have a medical condition that may be causing the symptoms the person is attributing to EHS, that they have a psychological evaluation, and that the person's environment be evaluated for issues like air or noise pollution that may be causing problems.

Periodontal abscesses may be difficult to distinguish from periapical abscesses. Since the management of a periodontal abscess is different from a periapical abscess, this differentiation is important to make (see Dental abscess#Diagnostic approach) For example, root canal therapy is unnecessary and has no impact on pain in a periodontal abscess.

Also termed "lip dermatitis", eczematous cheilitis is a diverse group of disorders which often have an unknown cause. Chronic eczematous reactions account for the majority of chronic cheilitis cases.

It is divided into endogenous (due to an inherent characteristic of the individual), and exogenous (where it is caused by an external agent). The main cause of endogenous eczematous cheilitis is atopic cheilitis (atopic dermatitis), and the main causes of exogenous eczematous cheilitis is irritant contact cheilitis ("e.g.", caused by a lip-licking habit) and allergic contact cheilitis. The latter is characterized by a dryness, fissuring, edema, and crusting. It affects females more commonly than males, in a ratio of about 9:1.

The most common causes of allergic contact cheilitis is lip cosmetics, including lipsticks and lip balm, followed by toothpastes. A lipstick allergy can be difficult to diagnose in some cases as it is possible that cheilitis can develop without the person even wearing lipstick. Instead, small exposure such as kissing someone who is wearing lipstick is enough to cause the condition.

Allergy to Balsam of Peru can manifest as cheilitis. Allergies to metal, wood, or other components can cause cheilitis reactions in musicians, especially players of woodwind and brass instruments, "e.g.", the so-called "clarinetist's cheilitis", or "flutist's cheilitis". "Pigmented contact cheilitis" is one type of allergic cheilitis in which a brown-black discoloration of the lips develops. Patch testing is used to identify the substance triggering allergic contact cheilitis.

Currently there are no open research studies for otodental syndrome. Due to the rarity of this disease, current research is very limited.

The most recent research has involved case studies of the affected individuals and/or families, all of which show the specific phenotypic symptoms of otodental syndrome. Investigations on the effects of FGF3 and FADD have also been performed. These studies have shown successes in supporting previous studies that mutations to FGF3 and neighboring genes may cause the associated phenotypic abnormalities. According to recent studies involving zebrafish embryos, there is also support in that the FADD gene contributed to ocular coloboma symptoms as well.

Future research studies are required in order to better grasp the specific relationship between the gene involved and its effect on various tissues and organs such as teeth, eyes, and ear. Little is known and there is still much to be determined.

Common causes of drug-related cheilitis include Etretinate, Indinavir, Protease inhibitors, Vitamin A and Isotretinoin (a retinoid drug). Uncommon causes include Atorvastatin, Busulphan, Clofazimine, Clomipramine, Cyancobalamin, Gold, Methyldopa, Psoralens, Streptomycin, Sulfasalazine and Tetracycline. A condition called "drug-induced ulcer of the lip" is described as being characterized by painful or tender, well-defined ulcerations of the lip without induration. It is the result of oral administration of drugs, and the condition resolves when the drugs are stopped.

MAV is not recognized as a distinct diagnostic entity. Lembert and Neuhauser propose criteria for definite and probable migraine-associated vertigo.

A diagnosis of "definite migraine-associated vertigo" includes a case history of:

- episodic vestibular symptoms of at least moderate severity;

- current or previous history of migraine according to the 2004 "International Classification of Headache Disorders";

- one of the following migrainous symptoms during two or more attacks of vertigo: migrainous headache, photophobia, phonophobia, visual or other auras; and

- other causes ruled out by appropriate investigations.

A diagnosis of "probable migraine-associated vertigo" includes a case history of episodic vestibular symptoms of at least moderate severity and one of the following:

- current or previous history of migraine according to the 2004 "International Classification of Headache Disorders";

- migrainous symptoms during vestibular symptoms;

- migraine precipitants of vertigo in more than 50% of attacks, such as food triggers, sleep irregularities, or hormonal change;

- response to migraine medications in more than 50% of attacks; and

- other causes ruled out by appropriate investigations.

Note that, in both of the above criteria, headache is not required to make the diagnosis of migraine-associated vertigo.

They add that, in patients with a clear-cut history, no vestibular tests are required. Other historical criteria which are helpful in making the diagnosis of migraine-associated vertigo are vertiginous symptoms throughout the patient’s entire life, a long history of motion intolerance, sensitivity to environmental stimuli, illusions of motion of the environment, and vertigo that awakens the patient.

Treatment of migraine-associated vertigo is the same as the treatment for migraine in general.

An important factor is whether the involved tooth is to be extracted or retained. Although the pulp is usually still vital, a history of recurrent periodontal abscesses and significantly compromised periodontal support indicate that the prognosis for the tooth is poor and it should be removed.

The initial management of a periodontal abscess involves pain relief and control of the infection. The pus needs to be drained, which helps both of these aims. If the tooth is to be removed, drainage will occur via the socket. Otherwise, if pus is already discharging from the periodontal pocket, this can be encouraged by gentle irrigation and scaling of the pocket whilst massaging the soft tissues. If this does not work, incision and drainage is required, as described in Dental abscess#Treatment.

Antibiotics are of secondary importance to drainage, which if satisfactory renders antibiotics unnecessary. Antibiotics are generally reserved for severe infections, in which there is facial swelling, systemic upset and elevated temperature. Since periodontal abscesses frequently involve anaerobic bacteria, oral antibiotics such as amoxicillin, clindamycin (in penicillin allergy or pregnancy) and/or metronidazole are given. Ideally, the choice of antibiotic is dictated by the results of microbiological culture and sensitivity testing of a sample of the pus aspirated at the start of any treatment, but this rarely occurs outside the hospital setting.

Other measures that are taken during management of the acute phase might include reducing the height of the tooth with a dental drill, so it no longer contacts the opposing tooth when biting down; and regular use of hot salt water mouth washes (antiseptic and encourages further drainage of the infection).

The management following the acute phase involves removing any residual infection, and correcting the factors that lead to the formation of the periodontal abscess. Usually, this will be therapy for periodontal disease, such as oral hygiene instruction and periodontal scaling.

In examining the published studies on opioid-induced hyperalgesia (OIH), Reznikov "et al" criticize the methodologies employed on both humans and animals as being far-removed from the typical regimen and dosages of pain patients in the real world. They also note that some OIH studies were performed on drug addicts in methadone rehabilitation programs, and that such results are very difficult to generalize and apply to medical patients in chronic pain. In contrast, a study of 224 chronic pain patients receiving 'commonly-used' doses of oral opioids, in more typical clinical scenarios, found that the opioid-treated patients actually experienced no difference in pain sensitivity when compared to patients on non-opioid treatments. The authors conclude that opioid-induced hyperalgesia may not be an issue of any significance for normal, medically-treated chronic pain patients at all.

Opioid-induced hyperalgesia has also been criticized as overdiagnosed among chronic pain patients, due to poor differential practice in distinguishing it from the much more common phenomenon of opioid tolerance. The misdiagnosis of common opioid tolerance (OT) as opioid-induced hyperalgesia (OIH) can be problematic as the clinical actions suggested by each condition can be contrary to each other. Patients misdiagnosed with OIH may have their opioid dose mistakenly decreased (in the attempt to counter OIH) at times when it is actually appropriate for their dose to be increased or rotated (as a counter to opioid tolerance).

The suggestion that chronic pain patients who are diagnosed as experiencing opioid-induced hyperalgesia ought to be completely withdrawn from opioid therapy has also been met with criticism. This is not only because of the uncertainties surrounding the diagnosis of OIH in the first place, but because of the viability of rotating the patient between different opioid analgesics over time. Opioid rotation is considered a valid alternative to the reduction or cessation of opioid therapy, and multiple studies demonstrate the rotation of opioids to be a safe and effective protocol.

Tuber cinereum hamartoma may be associated with Pallister-Hall syndrome, a diagnosis characterized by multiple malformations, including polydactyly and imperforate anus. Neurologic symptoms are less severe in Pallister-Hall than in isolated cases of hamartoma.

Clinicians will often follow a diagnostic checklist to test whether or not an individual is exhibiting behaviors and characteristics that may lead to a diagnosis of ARFID. Clinicians will look at the variety of foods an individual consumes, as well as the portion size of accepted foods. They will also question how long the avoidance or refusal of particular foods has lasted, and if there are any associated medical concerns, such as malnutrition. Unlike most eating disorders, there may be a higher rate of ARFID in young boys, than there is in young girls.