Occlusal splint effects on visual capacities in patients with temporomandibular disorders (TMD)
Published in General & Internal Medicine
The existing literature suggests the potential impact of TMDs on vision; furthermore the visual function is linked, mainly through neurological connections, to the stomatognathic apparatus. So our challenge was to explore a new topic still little known, about the possible effects of occlusal splint therapy (one of the most common methods to manage TMD) in individuals with temporomandibular disorders (TMD) on visual functions; more precisely we concentrated our attention on the accommodative capacity and ocular convergence.
The choice to do this type of study was courageous because the stomatognathic system's influence on dental and ophthalmic apparatus is acknowledged and limited research has explored the therapeutic impact on vision. The novelty lies in bridging disciplinary boundaries and proposing innovative therapeutic strategies to enhance our understanding of the symbiotic relationship between the stomatognathic system and the visual apparatus in the context of TMD.
After several searches in literature, we chose for the simplest and most easily reproducible method for an inexperienced operator (a dentistry student) to perform the orthoptic examination for both, convergence and accomodation tests (called the Duane’s test) as you see in the picture below. It is suggestive to underline that before including patients in our study we experimented the visual test on colleagues to understand how it was performed(in another picture below you can see the first operator and a colleague during the execution of the vision test at the department of the Operative Unit of Odontostomatology of ASST Santi Paolo e Carlo, associates of the University of Milan). This department is run by dentistry students, professors and tutors. Thursday was the day dedicated to the gnathological visits. For each patient we examined a medical history and the decision to include the patient in our study was based on the pre-established inclusion and exclusion criteria. At this point, after the gnathological visit and after asking the patient for consent, the vision test was performed. Two people were needed to perform the orthoptic test: always the same operator who measured the patient’s accomodation and convergence values with the stick of Duane, and another operator, who could also change from time to time for recording the collected data. The duration of the test was approximately 10 minutes per patient. We managed to visit and include in our research an average of approximately three patients per week. After this all the collected data were reported in an excel file to be analyzed. None of the patients we asked for consent refused to undergo visual tests. Indeed all the partecipants were happy to give their contribution to the research.
It is important to highlight that the whole study was the result of teamwork and constant collaboration between colleagues. The support of an orthoptist was also essential to try to understand some of the main aspects relating to visual functions.
The rationale of this study stems from the intricate interdependence between the stomatognathic system and the visual apparatus, as evidenced, in different studies, by neural connections between dental pulp, periodontal, temporomandibular joint (TMJ) receptors, masticatory and extraocular muscles: in particular it seems that the proprioception of these structures find anatomical contiguity in the mesencephalic nucleus of the trigeminal nerve.
Even if there aren’t recent studies on the topic, so further research will be necessary, we can suppose that in clinical practice our study could be an interesting starting point. In fact some authors observed alterations in visual capacities in subjects with temporomandibular disorders; this because oro facial afferents may involve physiological synaptic interconnections with the visual neural apparatus and therefore can produce improving or worsening effects in the functioning of both, intrinsic(accomodation) and extrinsic(convergence) ocular muscles. It is therefore possible to hypothesize that occlusal splint therapy, by improving TMD symptoms and related pain, might help reduce alterations in nerve conduction that affect visual function. In fact the main occlusal splint functions are to change the working length of the masticatory muscles during clenching due the variation in the vertical dimension, reducing tension, muscle fatigue and pain. Furthermore, thanks to its thickness, it should favor a decompression of the joint surfaces burdened by overload, optimizing TMJ’s work. Even if we obtained some effects during an occlusal splint treatment on visual abilities however we can not conclude definitively that the use of an occlusal splint in patients with temporomandibular disorders could improve some visual capacities. In fact we have to recognize that we can’t give a certain explanation to the results obtained due some critical points of our study such as a small sample’s size, visual tests not very accurate and precise and the little experience of the operator as well as the lack of studies in literature on the same topic with strong scientific evidence. So it would definitely be interesting to continue projects that include high levels of incisiveness (randomized clinical trials), with visual test more accurate and precise in order to be reproducible and repeatable and recruiting large numbers of subjects. On that perspective, it could be interesting to assess with other researches, whether the stomatognathic and visual apparatus could also influence other districts such as the postural system (for example concerning the head position) to understand if the treatment of a single stomatognathic, visual or postural problem could have a beneficial effect not only on a particular district but also on others. It could be interesting for example using neuroimaging techniques to observe brain activity changes in patients with TMD during jaw movements; consider new diagnostic tools that simultaneously measure jaw function and visual performance to provide a more integrated approach to diagnosing and treating TMD. We think that in future it could be useful to integrate the different disciplines so that the approach to the patient in the treatment of some stomatognathic, visual and postural system is multidisciplinary in order to find a new therapeutic pattern to help people to reduce pain and, in the same time, improve quality of life. Therefore we hope that our study will arouse interest in carrying forward research in this field. Also because we need for further investigations to strengthen our findings.
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BDJ Open
This is an international, peer-reviewed, open-access, online-only journal publishing dental and oral health research from all disciplines. The journal is owned by the British Dental Association (BDA) and is the sister journal of the British Dental Journal.
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