Study design
This was a retrospective observational cohort study performed in a dental office and in a physiotherapy and osteopathic practice. The retrospective study was initiated by the investigators and self-coordinated. Investigators from the dental office and from the physiotherapy and osteopathic practice designed the study, collected, and managed the data, and a PhD student from Lyon I University performed the statistical analyses.
Participants
Participant recruitment was carried out on patients treated first at the dental office in Lyon (France) and then oriented at the physiotherapy and osteopathic practice in Lyon (France) for a joint care over a period of 10 months (from September 2019 through June 2020).
A total of 21 adult clinical cases (≥ 18 years of age) presenting mouth opening restriction with X-rays of normal temporomandibular joints resulting from trauma (chin shock or tooth extraction) or clenching due to stress were included. Exclusion criteria were patients with cophosis (total deafness), patients with major mechanical injury, and those with severely impaired cognitive or psychiatric abilities (inability to understand and/or communicate).
Treatment / Interventions
The Alphabox® is medical device (Fig. 1), which is part of the ALLYANE method. The human hearing frequency range of a healthy young person is about 20 to 20 000 Hz. This device is a generator which emits specific low frequency sounds from 50 to 400 Hertz (Hz) through headphones (LFS: low frequency sounds). These sounds are emitted with different sequences and modes during the rehabilitation period. Alphabox® allows to emit two types of sounds: pulsed sounds and associated sounds (Byrne, 2017).
According to the ALLYANE® process, the session took place in a treatment room including the Alphabox®, a massage table, video analysis and specific software (Visible Body©). These tools allow the patient to become aware of his motor pattern as well as the visualization of the patient’s progress by the investigator during the sessions.
MMO was defined as the maximal interincisal distance on unassisted active mouth opening. Measurement of maximal mouth opening capacity reflects mandibular range of motion. It is simple but important clinical parameter for follow-up and outcome of diverse affections of the stomatognathic system. MMO was measured using a TheraBite® Range of Motion Scale (Atos, Sweden) (Fig. 2). Each participant’s mouth opening was measured before and immediately after intervention. The participants were positioned supine on a flat therapy table in an examination room. The investigator instructed the participants to slowly and comfortably open their mouths as wide as possible. The TheraBite® Range of Motion Scale was passively placed between the edges of upper and lower central incisors. The measurement was read and recorded to the nearest millimeter (Fig. 3). Measurements of right and left lateral deviation were also included. The results were entered into an Excel datasheet.
Results were divided into three groups:
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All the 21 tested patients.
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Group with “limitation of mouth opening”: number of millimeters measured from the incisal edge of the upper anterior teeth to the incisal edge of the lower anterior teeth with the TeraBite ruler (opening limitation < 40mm).
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Group without “limitation of mouth opening”: number of millimeters measured from the incisal edge of the upper anterior teeth to the incisal edge of the lower anterior teeth with the TeraBite ruler (opening limitation > 40mm).
Participants underwent a rehabilitation session with neuromotor reprogramming. At the beginning of the session, we track the patient’s medical and complaint history (anamnesis). Then we took videos (iPad AIR© and iPad PRO©) of all patients to follow their evolution but more important to allow the patient to be conscious of his/her mouth opening. At this stage, MMO and lateral deviations were measured.
Visible Body© application (Muscle Premium 2018) is a detailed guide to understanding how muscles and bones interact. Thanks to this application and the explanations provided by the practitioner, the patient can visualize the anatomical position of the masticatory muscles responsible for the clenching of the teeth which, through their contractions, prevent the proper development of the mouth opening (masseters, temporal, medial and lateral pterygoid muscles).
Neuromotor reprogramming used with the ALLYANE process is a tripod-based method including proprioception, mental imaging, and low frequency sounds (Fig. 4).
Proprioception, also referred to as our 6th sense, is today the subject of many scientific studies in the field of rehabilitation (Jahn and Krewer, 2020; Roll, 2003; Smith, 2011). Dependent on mechano-receptors located at the level of muscles, tendons, joints, ligaments, and support tissues, it is directly involved in the apprehension of the position of our body in space, our movements (coordination, movements), and balance. During the neuromotor reprogramming, the patient has to be conscious of his environment and his movement based on somatosensory information.
In a stable environment, healthy people rely approximately 70% on somatosensory information (proprioception), 10% on vision and 20% on vestibular information (Le Goïc et al. 2013). The masticatory system (orofacial sensory receptors, bones, masticatory muscles, temporomandibular joints) also plays a role in postural control (Tardieu et al., 2009).
Motor imagery (MI) is “the mental representation of an action without executing it physically. It stimulates the brain’s motor networks and promotes motor learning after a spinal cord injury” (Di Rienzo et al., 2015). MI is known to engage overlapping cerebral substrates with physical practice of the same action (functional equivalence principle). MI shares many similarities with the actual execution of movements with regard to the processes that take place in the central nervous system. For instance, it leads to similar activations of brain regions as planning, preparation and execution of movements (Decety and Boisson, 1990; Grafton et al., 1996; Mellet et al., 1998). To imagine a movement is to stimulate a large part of the areas that allow the gesture (Jeannerod, 2001; Jeannerod and Frak, 1999). For this reason, patient is asked to focus his attention on visual and kinesthetic motor imagery for a few minutes during neuromotor reprogramming.
Relaxation with low frequency sounds. This stage consists in a general relaxation protocol performed after installing the Alphabox® with a duration between 3 and 10 minutes. From this step, the pulsed sounds emitted by the Alphabox® aims at placing the patient in a state of hypo-vigilance allowing sensory isolation from external stimuli.
Outcome parameters
Personal and anthropometric data were evaluated at baseline (before treatment). The outcome parameters described hereafter were evaluated at baseline (before treatment) and after treatment neuromotor reprogramming: TMD parameters (maximum mouth opening and deduction movements (right and left)).
Data handling and data analysis
All data were confidentially secured by storing it on a password-protected computer attainable only by the principal investigators. All individual details were replaced with ID codes. At the end of the data collection, all data were transferred securely to a server and stored without any time limitation.
Statistical analysis
Statistical analysis was carried out using R Statistical Software (version 3.6.3; R Foundation for Statistical Computing, Vienna, Austria). The level of significance was set at p < 0.05 for all statistical tests. Descriptive statistical methods were used for calculating the means and standard deviation of the means. Paired t-tests on the differences of scores obtained before and after sessions were used to compare the pre- and post- neuromotor reprogramming results. The Cohen’s d effect size was used to study the effect size.