Acupuncture therapeutic protocols for the management of temporomandibular disorders *

BACKGROUND AND OBJECTIVES: For most cases, temporomandibular disorders should be treated by a non-invasive, interdisciplinary and integrative process. In traditional Chinese medicine, acupuncture is an excellent tool aiming at treating and healing this disease. This study was a critical literature review to observe the efficacy of traditional Chinese acupuncture to treat muscular temporomandibular disorders and to identify primary acupoints. CONTENTS: Pubmed, LILACS, Scielo and Cochrane databases were queried to identify scientific articles relevant for the study. Articles were selected from January 2000 to May 2013. A total of 125 articles were found and 21 were included. Acupuncture treatment alone or as additional therapy, or even compared to other techniques, was superior and effective to improve pain and function of patients with temporomandibular disorders and most commonly used acupoints were IG4, E6, E7 and F3. CONCLUSION: This study has shown that acupuncture is a technique recommended by national and international literature to treat muscular temporomandibular disorders, promoting pain relief and/or total intensity, improvement of joint movements and oral function and decrease of masticatory muscles hyperactivity.


INTRODUCTION
Orofacial pain is associated to head, face and neck soft tissues and may be defined as dysfunction and pain affecting sensory and motor transmission in the trigeminal nervous system 1 .Among pains affecting this region there are temporomandibular disorders (TMD) which represent a collective term related to a group of musculoskeletal and joint problems which affect the temporomandibular joint (TMJ) and associated structures 1,2 .TMD may present as facial pain, stiffness sensation, joint sounds (clicks), deviation of mandibular midline, restricted movements and pain during function 3 .Among such disorders, one should stress myofascial pain, which has been documented as the most prevalent disorder in this region 1,2 and may affect individuals' routine to a greater or lesser extent [4][5][6] .Current interventions to manage TMDs involve therapies with muscle relaxant plates, drugs, physiotherapy, self-care guidance and education and surgeries 7,8 .Noninvasive or even nonsurgical therapies are the most widely used and prescribed therapies and according to the literature they have been very successful to date 9 .Studies have shown that 74% of patients with TMD look for conservative, more alternative and complementary therapies, especially looking for manual therapies, massage therapy and acupuncture 10,11 .Acupuncture is indicated and effective to manage TMD, based on pain decrease mechanisms, anti-inflammatory properties and with endocrine neuro-hormonal effects 9,11 .The Traditional Chinese Medicine (TCM) is an energetic medicine, that is, it is based on the existence of an energetic structure beyond the physical body, and states that in our body the energy circulates by channels or meridians which, when punctured, reorganize the energetic circulation throughout the body.Disease, in turn, is always a disorganization of the functional energy which controls and dynamizes organs.Chinese philosophical conception about the universe is based on three basic pillars: Yang/Yin theory, five movements and Zang Fu (organs and viscerae) 12,13 .Acupuncture aims at managing and healing diseases by the application of skin stimuli with the insertion of needles on specific points called acupoints 14,15 .This is also a reflex therapy where the stimulation of one area acts on other(s).For such, it primarily uses nociceptive stimuli 14,15 .This study aimed at carrying out a critical literature review, in Portuguese and English, to check the efficacy of traditional Chinese acupuncture to treat muscle-type TMD, as well as at identifying major acupoints which will help guiding clinical approaches of acupuncture professionals.

CONTENTS
PubMed, LILACS, Scielo and Cochrane (including Central Cochrane) databases were searched to identify scientific articles relevant to the study.Articles were selected from January 2000 to May 2013 using the following keywords (DeCS Descriptors in Health Science): Temporomandibular Disorder AND Acupuncture OR Chinese Acupuncture OR Acupuncture Techniques, in Portuguese and English languages.After the search, a previous screening of articles was carried out, based on articles title and abstract, excluding possible publications unrelated to the subject.Then, criteria for the final selection of articles were applied.Table 1 shows the results of the search.

Studies selection criteria
Controlled randomized studies, cohort clinical trials, clinical studies, case-control studies, cross-sectional studies and case series reports having in their methodology the application of different acupuncture techniques, types of used points and meridians, were included.Case reports, systematic literature reviews and literature reviews were excluded.Inclusion criteria were limited to studies where participants were: • Humans of both genders, aged between 18 and 80 years; • Individuals diagnosed with muscle-type TMD, meeting the following criteria: Criteria for muscle TMD 1,6 Myofascial pain in masseter and/or temporal masticatory muscles: • Pain on mandible, temple or ear region in the last month; • Pain modified with movement, function or parafunction; • Report of family pain at masseter or temporal muscle palpation; • Individuals with our without mouth opening limitation; • Individual with muscle pain caused by systemic diseases, patients with toothache, individuals with psychological disorders previously identified and individuals with recent history of face and neck trauma were excluded.Relevant data were part of studies where acupuncture protocols were applied to patients with muscle-type TMD and whose results were mentioned in the study.

Data collection
A reviewer has selected articles as from abstract data and in cases when abstracts were unavailable, through title information.Relevant data for this stage were type of study and sample profiles.Selected articles should also meet all selection criteria in their complete publication.

Articles review
The next step was to evaluate selected articles to determine their internal and external validity.If there was inadequate information not allowing criteria evaluation, the author would be contacted by e-mail to explain study design and characteristics.We have found 125 potential scientific articles.After analyzing the abstract, 21 articles were selected to be fully evaluated.One hundred and four articles were excluded from the study for not meeting inclusion criteria.Among them, 25 articles were dated before 2000, five were excluded for being a single clinical case report, two articles had no relevant results and just clinical observations and five articles were not written in the defined standard language (two in Spanish, one in German and two in Chinese).A total of 54 articles were excluded for not matching the theme proposed by this review.
The 21 selected articles are shown in table 2. Most articles are in English being just two in Portuguese.Tables 2 and 3 show major features of included studies, such as studied disease, primary treatment (treatment recommended and treatment of choice for the case), additional treat- IG4 and E6 (real acupuncture) and points close to IG4 and E6 for placebo Both groups had significant pain intensity decrease, without difference between groups ment, number of evaluated and treated patients, number of acupuncture sessions, as well as the list of all major acupuncture points used and results found with a certain technique or comparison among techniques.
Most described and applied meridians were stomach, with 26 cases, followed by large intestine with 15 cases and gall bladder with 12 cases.Figures 1 and 2 describe all points mentioned by the 21 included articles.

DISCUSSION
This study has provided data showing that acupuncture is a TCM technique indicated and recommended by national and international literature to treat TMD.In most of the 21 articles selected and described in this review, acupuncture alone or as complementary therapy or even as compared to other techniques was superior and efficient to improve pain and function of patients with muscle-type TMD.Acupuncture directly impacts mental stress, decreases anxiety and improves sleep quality.Acupuncture holistic approach allows dealing with other comorbidities, as well as with integrative problems, such as headache and body pain, aiming at reaching physical and mental balance 27 .
Studies have shown that acupuncture to treat musculoskeletal pain is a promising technique.In a study with 92 patients, 69% had good or excellent response to treatment, with at least 30% pain decrease 36 .
In our study, all articles show a predilection for IG4 as a distant point with very strong energetic action.IG4 has excellent function as potent anti-inflammatory and analgesic 13,36 .Even so, many meridians and points had more indications and utilization.In 17% of all cases, IG4 was used as the point of choice to treat muscle TMD, followed by 11% of points E6 and E7 and 6% of point F3.Also, in 4% of cases, points ID19 and TA17 were indicated.It is also interesting to note that some extra points were more frequently used, indicating that their prescription should be always recommended.Points Taiyang and Yintang are extra points of easy access and greatly improve painful symptoms of TMD patients 27 .Currently, and following the Western vision, channels or meridians through which the whole energy of our body circulates are considered integrative or functional areas where there is the participation of several local and systemic systems, such as nervous, circulatory, lymphatic, endocrine and immune systems, among others 17,26,36 .Acupuncture action mechanisms may be explained by three principles.The first is based on the placebo effect of the technique, which is somehow controversial, because acupuncture is effectively used also in non-suggestible beings such as animals and plants 37 .The second principle is based on Mendell's control gate theory 38 and the third principle involves the descending release by the central nervous system of hormones and neurochemical substances such as steroids, endorphin, serotonin and other natural analgesics 39 .
The biggest problem of current scientific studies using acupuncture as treatment is primarily based on the Western theory of creating therapeutic protocols for each case.For example, to treat patients with muscle TMD, one should use specific acupuncture points.However, acupuncture is a TCM technique which presents an energetic diagnosis and tailors the treatment for each patient, inter-relating consequences for the environment, emotional, psychosocial and biological factors.Scientific articles, in addition to creating therapeutic proto-cols, have always a Western diagnosis and the treatment is the same, with the same acupoints for the whole sample.So, when analyzing articles using acupuncture as therapy, one should observe that acupuncture is an Eastern technique looking for tailoring patients' treatment and always in search of a more holistic vision.Obviously, each scientific article has to standardize its methodology, and treatment tailoring is very often unfeasible.

CONCLUSION
Muscle TMD treatment with acupuncture promotes pain relief and/or total intensity decrease, improves jaw movements and decreases muscle hyperactivity of masticatory muscles.Acupuncture professionals should have in mind that some points were effective to treat muscle TMD, such as stomach, large intestine and gall bladder acupoints.TMD patients may, in most cases, resort to acupuncture as alternative, complementary or even primary treatment to decrease painful symptoms and to improve oral function.

Table 1 .
Result of the search carried out in different literature databases.

Table 2 .
Summarized information of articles about treatment, number of sessions and number of evaluated patients

Table 3 .
Summarized information of articles about acupuncture points used and results obtained