It is possible to have an allergic reaction to the materials used in dentistry. These reactions may be type I reactions (immediate) or type IV reactions (delayed). While type I reactions are characterized by the release of humorally active substances and may lead to asthmatic attacks, mucosal swelling, and the much dreaded anaphylactic shock, type IV reactions are characterized by the formation of incomplete antigens (haptens) that bind to tissue proteins to form complete antigens. According to the relevant medical guidelines, diagnosing an allergy requires that allergy testing is used to confirm any allergy suspected based on clinical symptoms.
In the field of so-called alternative dentistry, testing is by far more extensive. Testing of dental materials is conducted in countless variations, and it also contributes to the marketing efforts in this field.
Moreover, testing is not limited to materials, but extended to teeth that have undergone root canal procedures, and to areas of the jaw bone, in particular the spongiosa. Practitioners will conduct so-called muscle testing and declare teeth with previous root canal procedures or fully healed wounds from previous tooth extractions pathological areas in need of sanitation. Testing is usually done with various devices that are of a dubious, but always impressive nature, and that are referred to by mysterious names. Practitioners use so-called electromedical diagnostic procedures to generate a diagnosis that they will present to the patient as an objectively established fact. A staggering number of electromedical diagnostic procedures is available. As G.-M. Ostendorf reports, “there is a barely manageable variety of these unconventional electromedical methods, which is all the more confusing as publications on these methods are usually not circulated outside interested parties.” (Quote translated from German)
The following list (based on Ostendorf’s work) does not claim to be exhaustive:
* Electroacupuncture according to Voll (EAV)
* Bioelectronic function diagnostics
* Vega testing
* Electrophysical terminal point diagnostics
* Electroneural diagnostics according to Croon
* Mora therapy
* Bioresonance therapy
* Biophysical information therapy
* Mora color therapy
* Multi-resonance therapy
* Metabolism testing and treatment device
* Matrix regeneration therapy
* Decoder dermography
All of these mysterious measuring techniques used in dental material testing are intended to detect incompatible materials used in dental prostheses the patient has previously received. Whenever subjected to closer scrutiny, however, incompatibilities postulated based on electromedical diagnostic procedures are found to be non-existent.
A scientific study has shown that results of the aforementioned electromedical diagnostic and treatment procedures cannot be reproduced and that they do not deliver any diagnostic value that goes beyond that of the use of divining rods. 
If you want to believe the apologists of the so-called alternative dentistry, testing of the materials used in dental procedures can also be accomplished entirely without any complicated equipment. According to statements made by the proponents of the so-called “applied kinesiology,” health information and the therapeutic consequences they require, can also be determined simply by getting physically close to the patient. Using this approach, the “therapist” senses a patient’s muscle activity and believes he or she can derive information on the patient’s health from this sensation. However, aside from generating physical closeness, the methods of applied kinesiology have been shown not to have any evidential value, and they have also been shown to be invalid in terms of diagnostics. 
Any positive resonance on the patient’s part to treatments following the approach of applied kinesiology is most likely due to the physical closeness between the “therapist” and the patient. This type of placebo effect should not be underestimated, and may lead to positive subjective assessments of the treatment by the patient. The fact that touching the patient during dental treatments can be very effective is readily illustrated using the gag reflex that may be triggered during impression taking: When the dentist hugs the patient this reflex is interrupted immediately. The hugging creates a sudden distraction and stimulus satiation in regions of the brain that are not involved in the gag reflex.
When comprehensive treatments are initiated based on the type of divining-rod-like misdiagnosis described above, dramatic consequences such as mutilations of the jaw bone and severe restrictions of masticatory function can arise [4-6,13].
As early as 1992, forensic medicine professor I. Oepen warned that “Unconventional, i.e. disputed medical methods are offered to many patients. However, the propagated effects of such methods could not be confirmed by controlled studies. So neither any risk taken by the use of these methods, can be justified nor are any costs for treatment vindicated .”
When it comes to material testing, laboratory medicine plays a special role, as it uses blood analysis to generate a medical diagnosis. These analytical procedures, e.g., the lymphocyte transformation test (LTT), are often very expensive while of very low specificity, which renders them useless for diagnosing potential allergic reactions to the metals used in the mouth. Due to the limited significance of these test results, testing generates costs without providing any benefit to the affected patients–aside from the potential benefit to the local economy.
In allergy diagnostics, the level of significance and interpretation associated with test results depends on the type of allergy present. On the one side, measuring IgE antibodies to pollen, dust mite, and animal hair antigens is of high diagnostic value. When it comes to variations of type IV allergic reactions, on the other side, the situation is different. These include the so-called contact allergies such as allergic reactions to metals in the mouth. Procedures for diagnosing contact allergies often deliver false-positive results, which makes them useless for diagnosing metal allergies in dentistry, as Harald Renz, director of the Institute of Laboratory Medicine and Pathobiochemistry, Molecular Diagnostics, of Philipps-Universität Marburg, explained to me:
“Interpreting the results of the LTT and other cellular tests is significantly complicated by the possibility of false-positive and false-negative findings. The LTT is not fully standardized, and it is a complex test that requires not only a lot of experience in conducting the test itself, but also in interpreting the results. Anyone performing this test has to adhere, without fail, to the quality assurance requirements as outlined by the test manufacturer. In addition, the test exhibits large inter-individual variability, and there are no ‘standard’ or ‘reference’ values. The only thing the LTT actually detects is whether the specific immune system has mounted a T-cell response to the metal in question. Positive and negative controls have to be tested as well.
Furthermore, there also are differences in the clinical significance between different metals: While its sensitivity to beryllium and nickel is sufficient, data for other metals are still lacking, and this is true also for metals that are relevant in dental implants and prostheses. What is particularly important: A positive test result on its own is not equivalent to a clinical diagnosis! Any test result needs to be interpreted in conjunction with all clinical findings for the patient in order to reach a meaningful conclusion. Furthermore, a single positive test result does not indicate that the patient is currently and acutely exposed to the metal in question. The exposure may have happened years ago, and may still produce a positive result. This is due to memory cells that may be circulating in the blood stream.”(Translated from German)
When disease is clearly present, it is, therefore, reckless to focus on a possible material intolerance without conducting sound diagnostic testing. Major damages may arise, e.g., because adequate therapy is not sought. To illustrate these types of damages, Ostendorf cites the case of a patient who was suffering from initially undiagnosed sleep apnea. This in turn caused a lack of oxygen and of relaxing periods of deep sleep, which led to daytime fatigue. As a reaction to this situation, the patient developed major mental problems. A physician practicing homeopathy conducted “resonance testing” on this patient, and the results, in conjunction with the physician’s considerable level of ignorance, led to a diagnosis of “exposure to pollutants.” The sheer number and duration of measurements and tests not only prolonged the patient’s suffering, it eventually led to the patient becoming suicidal. 
It is obvious that this is not an isolated case, and that similar misdiagnoses will be frequent for mental health issues as well.
An unpleasant diagnosis, such as depression, is often not readily accepted by affected patients, and is likely to be ignored. For these patients, it may be much easier to accept an external cause of their suffering than to face the idea of being mentally ill. Providing them with the false diagnostic pathway of ‘material intolerance’ may be very tempting to them. At one ‘holistically oriented’ dental office, the author experienced first-hand how patients were told that their suffering from depression was a reaction to material intolerance, all with the aim of generating large revenues from prostheses. Instead of suggesting a psychiatric examination in order to find the real reasons of their mental issues, the dentist suggested an external cause. Providing such a false diagnostic path may not only cause significant and sustained damage to the masticatory system, but it may also prevent appropriate and timely treatment. [16,17]
11. Ostendorf, G.-M. Spezielle Diagnostik im Überblick Teil 1: Unkonventionelle elektromedizinische Diagnose- und Therapiemethoden im Überblick. In Naturheilverfahren und unkonventionelle medizinische Richtungen, Springer Verlag: 2003.
12. Ernst, E. Komplementärmedizinische Diagnoseverfahren (Diagnostic methods in complementary medicine). Deutsches Ärzteblatt 2005, 102, 3034-3037.
13. Nimtz-Köster, R. Störfelder im Gebiss. Der Spiegel 2002.
14. Oepen, I. Kritische Bewertung unkonventioneller diagnostischer und therapeutischer Methoden in der Zahnheilkunde (Critical evaluation of unconventional diagnostic and therapeutic methods in dentistry). Fortschritte der Kieferorthopädie (Journal of Orofacial Orthopedics) 1992.
15. Ostendorf, G.-M. Elektroakupunktur nach Voll (EAV) – ein kritischer Kommentar. skeptiker 2018, 17-19.
16. Berger, U. Die Praxis der “Alternatvmedizin”: Ein Insider berichtet. In Kritisch gedacht, 2012; Vol. 2018.
17. Prchala, G. Weg mit der Zusatzbezeichnung “Homöopathie”. In zm online, Deutscher Ärzteverlag: 2018.