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Chewing is one of the most important orofacial functions. Over the last twenty years, a number of authors have examined the correlation between an efficient chewing function and different aspects of body functions: implementation of cognitive functions, reduction of nociceptive impulse propagation, reduced levels of stress, reduced risk of developing atherosclerosis and desaturation, limitation of eating disorders and constipation. Starting from the above considerations, this study aims at investigating the correlation between occlusal balance – without which there would be no proper mastication – and fundamental aspects as cognitive function, stress, arousal and concentration. For this purpose, we used specific tools and software to observe the electrical activity of the brain in 10 healthy volunteers. All the measurements for each participant have been carried out in three different phases: a first phase in which all the individuals were in a condition of initial occlusion; a second phase in which the occlusion was modified using a functional orthodontic device; and a third phase, in which individuals removed the device. The variations between three phases have been evaluated by using the Student’s t-test, and we considered them significant for p&lt;0.05. The results have highlighted a significant variation in terms of stress, arousal and concentration among the three phases.
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1971-1441
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Aldo  Giancotti
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Annali di stomatologia
chewing 3
Modification of cognitive function induced by a functional orthodontic device
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Original Article
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Ann Stomatol (Roma)
Aldo  Giancotti
2023/11/20
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Department of Clinical Sciences and Translational Medicine, University of Rome “Tor Vergata
1971-1441
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chewing 3
en
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Modification of cognitive function induced by a functional orthodontic device
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                                                                                                     Original Article


Modification of cognitive function induced
by a functional orthodontic device



Francesco Pachì1                                              In the field of functional orthodontics, mastication can ac-
Ruggero Turlà1                                                tivate specific muscular groups, influencing trophism of
Anastasia Romano1                                             the bone segment which these muscles are inserted in
Roberta Condò1                                                [1] or originate from [2].
Aldo Giancotti1                                               Furthermore, several theories suggest that the stomato-
                                                              gnathic apparatus can be meant as an “access door” to
1
  Department of Clinical Sciences and Translational           the whole body. The lack of occlusal balance might have
Medicine, University of Rome “Tor Vergata”                    negative repercussions on different body locations, and
                                                              one may presume that recovering a proper masticatory
Corresponding author: Aldo Giancotti                          function seems to be associated to the resolution of nu-
giancotti@uniroma2.it                                         merous pathologies and diseases.
                                                              In the last two decades, literature has sought to exam-
Abstract                                                      ine the correlation between an impaired mastication and
Chewing is one of the most important orofacial                structural alterations of all those cerebral areas that are
functions. Over the last twenty years, a number of            involved during chewing. Masticatory performance could
authors have examined the correlation between an              be linked in a relationship of direct proportionality to ce-
efficient chewing function and different aspects of           rebral blood flow [3,4], to cerebral oxygenation, to gray
body functions: implementation of cognitive func-             volume matter (GMV) and to the number of intercon-
tions, reduction of nociceptive impulse propagation,          nections between different cerebral areas [5]. In elderly
reduced levels of stress, reduced risk of developing          individuals, with an inadequate number of dental ele-
atherosclerosis and desaturation, limitation of eating        ments, the cerebellar and motor cortex GMV undergoes
disorders and constipation. Starting from the above           a significant reduction, as well as a dorsolateral prefron-
considerations, this study aims at investigating the          tal cortex (DLPFC), which is physiologically involved in
correlation between occlusal balance – without which          cognitive processes and in the expression of personality.
there would be no proper mastication – and funda-             Based on findings, it is not difficult to understand how
mental aspects as cognitive function, stress, arousal         advancing age is, in most cases, associated with a loss
and concentration. For this purpose, we used specif-          of the cognitive function [6,7].
ic tools and software to observe the electrical activity      The use of functional connectivity magnetic resonance
of the brain in 10 healthy volunteers. All the measure-       imaging (fcMRI) allows to highlight the brain areas main-
ments for each participant have been carried out in           ly involved during chewing. In particular, there seems
                                                              to be a connection between the motor cortex and the
three different phases: a first phase in which all the
                                                              post-central gyrus, the cingulate and precuneus cortex,
individuals were in a condition of initial occlusion; a
                                                              as well as the cerebellum, with the bilateral sensory-mo-
second phase in which the occlusion was modified
                                                              tor cortex, the superior temporal gyrus and the superior
using a functional orthodontic device; and a third
                                                              cingulate left cortex. Deficient chewing can suppress the
phase, in which individuals removed the device. The
                                                              proliferation of dentate gyrus cells [8] and trigger hippo-
variations between three phases have been evaluated
                                                              campal degeneration [9], resulting in impaired spatial
by using the Student’s t-test, and we considered them
                                                              memory [10]. A limited number of dental elements seems
significant for p<0.05. The results have highlighted a
                                                              to be linked to worsened cognitive-attentive functions
significant variation in terms of stress, arousal and
                                                              in patients affected by Alzheimer’s disease [11]; it also
concentration among the three phases.
                                                              seems to be connected with impaired learning ability, re-
                                                              lated to degeneration of periodontal mechanoreceptors,
Keywords: cognitive function 1; elastodontic appli-
                                                              with a consequential suppression of sensory feedback,
ances 2; chewing 3
                                                              which becomes rather insufficient and can cause central
                                                              atrophy [8]. Moreover, because of human connectome,
Introduction                                                  there might be a correlation between the Broca praxic
                                                              language area and the area of the motor mastication and
Chewing is essential for the appropriate nutrition of every   swallowing control in brain cortex; hence, language skills
person, for both physical and mental well-being. Howev-       and feeding quality could be interconnected [12].
er, chewing is guaranteed only by the presence of most        In addition to cognitive functions, several studies have
or all dental elements, by a balanced intercuspation and      highlighted the interdependence between higher levels
proper intraoral and extraoral muscular function.             of trigeminal stress and nociception suppression, with


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     Modification of cognitive function induced by a functional orthodontic device

     rising levels of serotonin and norepinephrine in the blood      set; the latter must adhere to the scalp, corresponding
     [13,14], reduced stress and salivary cortisol [15,16],          to the main brain areas (Figure 1), to allow the uptake
     greater alertness and concentration [17-19], alleviation        of neuronal electrical signals. To monitor the percentage
     of depression [20] and improvement in coordination and          of contact between the helmet and the scalp – which
     posture [21,22].                                                should range between 98% and 100% to be optimal and
     Finally, other authors have examined the relation among         reliable, and to obtain useful data for experimental pur-
     impaired chewing and atherosclerosis [23], decreased            poses - the Emotiv BCI software was used.
     gastrointestinal motility [24], and higher incidence of         Thanks to its Performance Metrics, the function mea-
     chronic obstructive pulmonary disease [25].                     sures six cognitive conditions on a Time-Value graph:
     On the other hand, an adequate number of dental ele-            “stress” (FRU), “engagement” (ENG), “interest” (VAL),
     ments would seem to reduce obesity incidence, thanks            “focus” (FOC), “excitement” (EXC), “relaxation” (MED).
     to the stimulation of lipolysis in the visceral adipose tis-    “Stress” refers to the degree of comfort experienced
     sue and a better satiety state because of the activation        by the individual at the time of measurement. The “en-
     of histaminergic fibers of the hypothalamus’ ventrome-          gagement” condition indicates the extent of the state of
     dial [26]. Moreover, Kimura et al. have underscored the         alertness and attention to external stimuli. “Interest” is
     reduced incidence of anorexia disorders [27].                   nothing more than the amount of attraction or aversion
     Based on the above considerations, the following study          to existing stimuli. “Focus” expresses the degree of con-
     aims at exploring the correlation between the use of an         centration stability. “Excitement” reflects a physiological
     orthodontic device (i.e. functional activator) and varia-       state of “arousal”, or rather activation of the sympathetic
     tions in terms of cognitive function, stress, alertness and     nervous system. Finally, “relaxation” indicates the abili-
     concentration.                                                  ty to recover after an intense concentration phase. The
                                                                     changes in the values of such conditions were monitored
     Materials and Methods                                           and recorded in three distinct phases, each lasting 10
                                                                     minutes: phase 1) the subject was observed at rest, be-
     For the study, 10 volunteers were recruited, including          fore using the activator (Figure 2); phase 2) the subject
     7 males and 3 females, aged between 22 and 30, with             was monitored during the use of the activator; phase 3)
     an average age of 27.7 yrs (± SD 2.6). At the time of           data was collected at rest, after activator removal. For
     measurements, none of the individuals was undergoing            the experiment, a U4 activator was used, at a low level,
     orthodontic treatment. No temporomandibular joint dis-          both in the body and in the shields, for several reasons:
     orders nor degenerative disorders affecting the nervous         to avoid bulkiness, minimize discomfort and measure-
     system were recorded.                                           ment distortion, to guarantee a neutral action, thanks to
     Each patient was asked to wear the Emotiv Pro+ hel-             its advancement wall built in class I.
     met, a device that can detect brain electrical activity, re-    Data for each phase was recorded every 10 seconds; in
     turning a sort of electroencephalographic outcome. The          turn, at the end of the experiment, 60 values per phase
     device consists of 2 sensors, which must be positioned          were recorded for each subject. The value average of all
     in the retro-auricular region, in correspondence with the       subjects enabled to obtain a single reference parameter
     mastoid process of the temporal bone, and 14 sponge             for each cognitive condition in each phase. Hence, it was
     electrodes, screwed to the end of each arm of the head-         possible to compare phase 1 with phase 2, phase 2 with




                                                                     Figure 2. The activator is a removable elastomeric materi-
                                                                     al device, the “fulcrum” of functional orthodontic treatment
                                                                     based on dentosophy. It consists of a single block which
                                                                     contacts both arches, and it is equipped with vestibular, pal-
                                                                     atal and lingual shields, through which the proper balance
                                                                     between extrinsic forces – i.e. perioral musculature – and
     Figure 1. AF3, F7, F3, FC5, T7, P7, O1, O2, P8, T8, FC6,        intrinsic forces – i.e. tongue - is restored; this way, maxillary
     F4, F8, AF4 are the brain areas where the sponge elec-          growth is properly oriented. Moreover, by using such device,
     trodes are positioned. DRL and CMS indicate the position of     it is possible to re-educate neurovegetative functions such
     the control electrodes.                                         as swallowing, phonation, chewing and breathing.



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F. Pachi et al.

phase 3, phase 3 with phase 1. For this purpose, the “p”                   2 and 3 (Table 2), although the variations in “stress”, “en-
significance of variations was considered using a Stu-                     gagement” and “interest” were not statistically significant,
dent’s t-test. To be considered significant, the variation                 the conditions “focus”, “excitement” and “relaxation” as-
value was to be p value < 0.05. All measurements were                      sumed significance (p < 0.05). Also comparing phase 3
carried out by a single operator.                                          with phase 1 (Table 3), for both “focus” and “excitement”
                                                                           significant values were recorded; the same cannot be
Results                                                                    said for the other four conditions.

To compare phase 1 with phase 2, phase 2 with phase
                                                                           Discussion
3, phase 3 with phase 1, the average values of each
cognitive condition were calculated in each of the three                   In particular, “relaxation” was recorded as more remark-
phases. The significance of the variations between the                     able in phase 3 (Figure 3). A possible explanation could
phase pairs was assessed by means of the Student’s                         be that the insertion of the activator, in phase 2, as a
t-Test distribution. Comparing phases 1 and 2 (Table 1),                   new variable in the stomatognathic system led to an in-
no significant changes were recorded across the six con-                   crease of the muscular function of the patient and, con-
ditions (p > 0.05). On the other hand, comparing phases                    sequently, an impairment in terms of relaxation, though



Table 1. Comparison table between T0 (phase 2) and T1 (phase 1).

    VARIABLES                             T0                                     T1                                T1-T0
                             Average               DV               Average               DV            Average            t Test (p)
         FRU                  39,177             10,570              45,203             14,835            6,026            0,120 *
         ENG                  61,812              8,281              64,403             10,096            2,591            0,414 *
         VAL                  55,301              5,141              57,173              9,816            1,872            0,634 *
         FOC                  25,955              9,140              28,384             11,434            2,429            0,578 *
         EXC                  39,942              5,990              41,427              5,540            1,485            0,571 *
         MED                  26,793              9,210              30,736             11,612            3,943            0,182 *
* Student’s t-Test. Bold indicates statistically significant difference.



Table 2. Comparison table between T0 (phase 3) and T1 (phase 2).

    VARIABLES                             T0                                      T1                               T1-T0
                             Average               DV               Average                DV            Average           t Test (p)
         FRU                  45,169             14,825              39,177              10,570           -5,99            0,360 *
         ENG                  58,017              7,719              61,812              8,281            3,795            0,106 *
         VAL                  60,427              6,225              55,301              5,141            -5,126            0,112 *
         FOC                  38,542             12,478              25,955              9,140           -12.587           0,011 *
         EXC                  47,331              4,849              39,942              5,540            -7,389           0,026 *
         MED                  31,870             11,740              26,793              9,210            -5,077           0,045 *
* Student’s t-Test. Bold indicates statistically significant difference.



Table 3. Comparison table between T0 (phase 1) and T1 (phase 3).

    VARIABLES                             T0                                      T1                               T1-T0
                             Average               DV               Average                DV            Average           t Test (p)
         FRU                  45,203             14,835              45,169              14,825           -0,034            0,995 *
         ENG                  64,403             10,096              58,017               7,719           -6,386            0,093 *
         VAL                  57,173              9,816              60,427               6,225            3,254            0,176 *
         FOC                  28,384             11,434              38,542              12,478           10,159            0,035 *
         EXC                  41,427              5,540              47,331               4,849            5,904            0,052 *
         MED                  30,736             11,612              31,870              11,740            1,134            0,727 *
* Student’s t-Test. Bold indicates statistically significant difference.



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     Modification of cognitive function induced by a functional orthodontic device




     Figure 3. Histogram showing the mean values of each patient for each condition. The values in phase 1 are shown in pink,
     those in phase 2 in yellow, those in phase 3 in blue. The conditions we are most interested in are those that have shown
     significance in the variations between the phases in the previous tables, i.e. “focus”, “excitement” and “relaxation”. All three
     significantly reduce in phase 2, but only “focus” and “excitement” significantly increase in phase 3, after removing the activator.
     This could support the hypothesis that the occlusal balance is correlated with the systemic one, and that the functional activator,
     by restoring the occlusal balance, might have some repercussions at the systemic level, specifically on the cognitive sphere.



     quite statistically imperceptible, at p > 0.05 comparing             phases 2 and 3, as well as between phases 1 and 3.
     phases 1 and 2. However, after removing the activator,               Hence, one can presume that the activator’s use, com-
     the values increased again with a significant variation,             bined with the crunching muscular activity, generates
     as can be seen from the comparison between phase                     a proprioceptive stimulus that raises both “focus” and
     2 and phase 3; this would indicate an increase in the                “excitement”. Consequently, once activator use is com-
     relaxation level of the subject as the device is removed.            pleted, cortical activity increases, raising attention and
     Indeed, most patients in the sample reported having                  concentration levels in turn.
     perceived somewhat muscle soreness by the end of
     the experiment, associated with a sense of relief upon               Conclusions
     activator removal.
     On the other hand, “focus” and “excitement” report-                  Therefore, considering the collected data, the variables
     ed different results. Both being part of the cognitive               of concentration, excitement and relaxation are the as-
     sphere, these conditions significantly increased from                pects undergoing the most significant variation. Among
     phase 2 to phase 3. This would suggest that a modifi-                these, the ones that draw our attention are “focus” and
     cation of the proprioceptive inputs, which are centrally             “excitement”: they significantly increased in phase 3 –
     transmitted, can be associated with a variation of the               compared to phase 2, in which the activator was insert-
     cognitive function, thus confirming a theory support-                ed in the mouth, but also considering the initial situation
     ed by several authors, including Sakamoto. In one of                 represented by phase 1 – they suggest that the device
     his studies, the latter showed how the reaction time to              can actually trigger a change in the cognitive function,
     the auditory oddball paradigm substantially decreased                identified in the increased ability to concentrate and pay
     in the phase immediately after the end of a chewing                  attention to external stimuli. Moreover, it is possible to
     exercise [7]. Similarly, in a study conducted by Wilkin-             continue to hypothesize a link between the use of the
     son, the author explained that chewing gum can raise                 functional activator – and the related occlusal balance
     a subject’s learning skills [28]. Kawakami too highlight-            and benefits for brain activity. It is worth highlighting the
     ed a reduced reaction time to the Stroop test during                 fact that only 10 patients were observed in the study.
     a gum chewing exercise [3]. Furthermore, introducing                 One can assume that by expanding the sample, even
     the concept of dentosophy, Montaud hypothesized the                  those variations that have reached values not far from
     existence of an interdependence between occlusal bal-                significance – such as “engagement” between phase 2
     ance and systemic balance [29].                                      and phase 3 – one can reach a p < 0.05. Further studies
     Concerning “relaxation”, removing the device reduces                 are required to gain more insightful data.
     muscular activation due to the thickness of the utilized
     material. Such thickness generates greater muscular                  References
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