The effect of a bimaxillary occlusion splint ­(Stressbite® dynamic splint system) on postural ­control and balance in patients with bruxism

Kwidzinski Marc (Physiotherapeut, M.Sc., OMT)¹, Dr. med. Vavken Patrick^2
1 Zürcher Hochschule für Angewandte Wissenschaften ZHAW, Department Gesundheit/Institut für Physiotherapie, Technikum­strasse 71, 8400 Winterthur, Schweiz
2 Alphaclinic Zürich, Kraftstrasse 29, 8044 Zürich, Schweiz

Abstract

Background: The craniomandibular system (CMS) has a great influence on the musculoskeletal system via neuroanatomical connections. Bruxism is a disorder of the CMS and can therefore negatively affect other parts of the body. Standard therapy includes the preparation of “crunch splints”.

Objective: To study the influence of the dynamic dental splint system Stressbite^®, on posture and balance in patients with bruxism.

Methods: The diagnosis bruxism was made with the Bruxism Status Protocol. The Stressbite was worn at night for six weeks. With the posture analysis system of Misura la Postura the movements of the body center of gravity, the plantar pressure distribution, the cervical spine movement and the posture were recorded at three measuring points. The general and pain condition was recorded with standardized questionnaires.

Results: There were statistically significant improvements in cervical mobility. The competence of the musculoskeletal system to stabilize the body’s center of gravity improved but did not show statistical significance. The evaluation of the plantar pressure distribution showed no significant changes without statistically significant changes in posture. The general condition as well as the intensity of pain improved significantly.

Discussion: The study could show that there are correlations in the neuromuscularly controlled alignment of body statics and occlusion. The occlusal references changed with the Stressbite system seem to result in positive changes in body statics and cervical mobility. The extent to which the statistically non-significant results are clinically relevant must be further investigated.

Conclusion: The Stressbite creats occlusal standard references that significantly improve cervical ROM and pain intensity and have a positive effect on stabilizing of the body’s center of gravity. Further studies are necessary.

Zusammenfassung

Hintergrund: Das Craniomandibuläre System (CMS) hat über neuroanatomische Verbindungen einen grossen Einfluss auf den Bewegungsapparat. Bruxismus ist eine Störung des CMS und kann daher andere Körperteile negativ beeinflussen. Zur Standardtherapie gehört die Anfertigung von «Knirschschienen».

Ziel: Untersuchung des Einflusses des dynamischen Zahnschienensystems Stressbite® auf Körperhaltung und Gleichgewicht bei Patienten mit Bruxismus.

Methoden: Die Diagnose Bruxismus wurde mit dem Bruxism Status Protocol gestellt. Stressbite wurde sechs Wochen lang nachts getragen. Mit dem Haltungsanalysesystem von Misura la Postura wurden an drei Messpunkten die Bewegungen des Körperschwerpunktes, die plantare Druckverteilung, die Halswirbelsäulenbewegung und die Körperhaltung erfasst. Der Allgemein- und Schmerzzustand wurde mit standardisierten Fragebögen erfasst.

Ergebnisse: Es gab statistisch signifikante Verbesserungen der zervikalen Beweglichkeit. Die Fähigkeit des Bewegungsapparates, den Körperschwerpunkt zu stabilisieren, verbesserte sich, zeigte aber keine statistische Signifikanz. Die Auswertung der plantaren Druckverteilung zeigte keine signifikanten Veränderungen ohne statistisch signifikante Haltungsänderungen. Der Allgemeinzustand sowie die Schmerzintensität verbesserten sich deutlich.

Diskussion: Die Studie konnte zeigen, dass es Zusammenhänge in der neuromuskulär gesteuerten Ausrichtung von Körperstatik und Okklusion gibt. Die mit dem Stressbite- System veränderten okklusalen Referenzen scheinen zu positiven Veränderungen der Körperstatik und der zervikalen Beweglichkeit zu führen. Inwieweit die statistisch nicht signifikanten Ergebnisse klinisch relevant sind, muss weiter untersucht werden.

Fazit: Stressbite schafft okklusale Standardreferenzen, die den zervikalen ROM und die Schmerzintensität deutlich verbessern und sich positiv auf die Stabilisierung des Körperschwerpunkts auswirken. Weitere Studien sind notwendig.

Introduction

Bruxism refers to the non-physiological clenching and grinding of the teeth, due to repetitive masticatory muscle activity. A distinction is made between sleep and awake bruxism [1]. Waking bruxism occurs with a prevalence of 22-31% and sleep bruxism with 9-15%. The prevalence peaks in the 2nd -3rd decade of life [2]. Differences between the sexes have not yet been clearly clarified [3-5].
The development is a multifactorial process with peripheral factors (e.g. occlusal interference), psychological influencing factors (stress, anxiety) as well as central or pathophysiological causes with involvement of the neurotransmitters and basal ganglia [6,7] Exogenous factors, such as antidepressants, Ritalin, alcohol and nicotine are considered risk factors [8]. There are correlations between bruxism and craniomandibular dysfunctions (CMD) but no causal relationship [3,9].
The craniomandibular system has functional connections with other body segments and thus plays an important role for the entire neuromuscular system [10]. The connections of the trigeminal nerve with nuclei of the brainstem, cerebellum and spinal cord play a crucial role here [11-13].
Kian Dilmaghani (Implantologist, M.Sc., Basel, CH) developed a bimaxillary occlusal splint, the dynamic dental splint system Stressbite® (SB) in 2014. (Figure 1)
The SB is made on the basis of dental impressions of the upper and lower jaw and a special registration procedure in the dental laboratory of the Schifflände practice. The occlusion is an actual value to which all jaw components orientate and adapt. If this is changed from the original situation due to bruxism, the physiology of all connected systems adapts [14-16].
This change should be resolved with the SB and stimulate a permanent maximum intercuspidation in different jaw positions (simulation of occlusal norm references).
The present work addresses the question:
“What effect does a bimaxillary occlusal splint (Stressbite® dynamic dental splint system), have on postural control and balance, in patients with bruxism?”

Methods

Design

This is a non-controlled clinical trial.

Subjects

Twenty-two study participants, men and women, aged between 20-40 years, with bruxism were recruited. Of these, 17 cases could be evaluated. The exclusion criteria listed in Table 1 were intended to reduce possible negative influencing factors on balance and posture.

Experimentation

Demographic data and the inclusion and exclusion criteria were checked with the following questionnaires:
– general medical history questionnaire
– Bruxism status protocol
– EQ-5D-5L (Quality of Life)
– Neck Disability Index (NDI)
– Graded Chronic Pain Scale (GCPS)
– Patient Health Questionnaire 9 (PHQ-9)
– Generalized Anxiety Disorders 7 (GAD-7)
– Mandibular Function Impairment Questionnaire (MFIQ)

The Bruxism Status Protocol was used for diagnosis. The PHQ-9 was used to screen for depression and the GAD-7 to screen for anxiety disorders. The GCPS was used in relation to facial pain [17]. The NDI was used to check the neck pain [18]. Both the GCPS and the NDI were collected again in the final examination. The MFIQ is used to record subjectively expressed temporomandibular joint complaints. [19] The MFQI and the EQ-5D-5L were completed in the baseline and final examinations (Figure 2).
Pregnancy was checked with a commercial urine pregnancy test (pharmacy), at each measurement time point.

Outcomes

The outcomes were recorded with the posture analysis system of the company Misura la Postura. [20] (Figure 3)

Primary Outcome

– Central position of the body’s centre of gravity and movements around this centre of gravity (Stabiloboard [21]).

Secondary Outcomes

– Plantar pressure distribution with a Stabiloboard
– Image analysis of the cervical spine ROM (Cervical R.O.M./R.O.M. BT, for measuring the mobility of the cervical spine [22])
– Posture (Physical Analyser, analysis of the posture in the frontal and sagittal plane [23])

The data were collected and stored using the Global Postural Analysis (GPA) software.
The variables ellipse area (EA), ellipse rotation (ER) and speed (indicates how fast the ER occurs around the EA) are used in this study to describe the construct of the position of the body’s centre of gravity and the movements around this centre of gravity.
First, the actual condition without SB was recorded, then with SB. To check the reprogramming processes, a follow-up measurement was carried out after one and six weeks, first without and then with SB.
The SB had to be worn at night during the 6 weeks. The test persons were supposed to go about their daily lives and leisure time as usual, without additional therapies, to be able to make as accurate a statement as possible about the effect of the SB.

Statistical analysis

The demographic data were analysed using descriptive statistics. First, the data of the recorded outcomes were tested for normal distribution of the residuals using the Kolmogorov-Smirnov test and for sphericity (5% level) using the Mauchly test. The histograms, skewness and kurtosis were also considered to assess normal distribution. [27]
The condition of normal distribution was fulfilled for the primary and secondary outcomes, so that a two-factor analysis of variance with repeated measures (ANOVA) could be performed for dependent data sets. Tests were performed on the occlusal splint factor (2 factor levels; with and without), on the time factor (3 factor levels; baseline measurement, 1st and 2nd follow-up) and on the interaction factor between these at the 5% level. Multiple comparisons were adjusted using the Bonferroni correction.
In addition to significance, the 95% confidence intervals are also of interest as well as clinically relevant changes. In case of violation of sphericity, the Greenhouse-Geisser correction was used.
The differences of the NDI, the GCPS and the MFQI were checked for normal distribution (Kolmogorov-Smirnov and Shapiro-Wilk test). The MFQI violated the requirement of normal distribution, which is why the Wilcoxon test was used here. The NDI, the GCPS and the EQ-VAS were evaluated with the t-test for dependent samples (two sided). The EQ-5D-5L was also evaluated with the Wilcoxon test, the presentation of the data was based on the EQ-5D-5L guidelines version 3.[28] Missing values were defined as such with 999.

Results

Descriptive statistics

Nineteen subjects were enrolled (12 women, 7 men; mean age 28.58 years, SD 5.47 years). Three subjects were smokers (1 man, 2 women) and six were former smokers. At the last follow-up, there were two dropouts. A total of 17 participants, 12 women and 5 men (15 non-smokers, 2 smokers) were evaluated.

Primary Outcome

Ellipse Area (EA)

For EA, the significance in the multivariate tests in the factor time of measurement is p = 0.265, in the factor SB p = 0.582 and in the interaction effect between time of measurement and SB p = 0.310. The Mauchly test for sphericity reached a significance of p = 0.023 in the factor time of measurement and a significance of p = 0.869 in the interaction effect. Sphericity is redundant with the factor SB, as this only has two factor levels. Sphericity can therefore be assumed in the in the interaction factor (p = 0.251). Sphericity cannot be assumed in the factor time of measurement. The Greenhouse-Geisser correction was applied (p = 0.318). However, there is a tendency to reduce EA with SB and from the 1st to the 3rd measurement point (Table 2).

Ellipse Rotation (ER)

For ER the significance in the multivariate tests in the factor time of measurement is p = 0.494, in the factor SB p = 0.793 and in the interaction effect p = 0.086. The Mauchly test for sphericity reached a significance of p = 0.928 in the factor time of measurement and a significance of p = 0.906 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.485) and in the interaction factor (p = 0.079). However, the angle, especially without SB, decreases from the first to the last time point from an average of 99.18° to 92.18°. Interestingly, at measurement time 3, with SB, there is a clear increase in the ER (Table 3).

Speed

For Speed, the significance in the multivariate tests in the factor time of measurement is p = 0.787, in the factor SB p = 0.036 and in the interaction effect p = 0.331. The Mauchly test for sphericity reached a significance of p = 0.502 in the factor time of measurement and a significance of p = 0.225 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.829) and in the interaction factor (p = 0.443). Speed increases with SB from measurement to measurement, without SB it initially falls and then rises again (Table 4).

Weight difference of the feet

The difference was formed from the weight load of the right and left foot. The smaller the difference, the more the person stands in the middle.
For the weight difference of the feet, the significance in the multivariate tests in the factor time of measurement is p = 0.333, in the factor SB p = 0.541 and in the interaction effect p = 0.069. The Mauchly test for sphericity reached a significance of p = 0.889 in the factor time of measurement and a significance of p = 0.196 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.264) and in the interaction factor (p = 0.164). The weight difference without SB increases from the first to the last measurement from 2.94 kg to 3.18 kg. Except for the second measurement, the SB leads to an increase in the weight difference (Table 5).

Secondary Outcomes

Plantar foot pressure distribution

For metatarsal 1 right (M1 right), the significance in the multivariate tests in the factor time of measurement is p = 0.752, in the factor SB p = 0.606 and in the interaction effect p = 0.156. The Mauchly test for sphericity reached a significance of p = 0.419 in the factor time of measurement and a significance of p = 0.475 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement
(p = 0.812) and in the interaction factor (p = 0.158).
For metatarsal 1 left (M1 left), the significance in the multivariate tests in the factor time of measurement is p = 0.443, in the factor SB p = 0.616 and in the interaction effect p = 0.804. The Mauchly test for sphericity reached a significance of p = 0.116 in the factor time of measurement and a significance of p = 0.096 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.619) and in the interaction factor (p = 0.736).
For metatarsal 5 (M5 right), the significance in the multivariate tests in the factor time of measurement is p = 0.148, in the factor SB p = 0.135 and in the interaction effect
p = 0.391. The Mauchly test for sphericity reached a significance of p = 0.800 in the factor time of measurement and a significance of p = 0.034 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.136). Sphericity cannot be assumed in the interaction effects factor. The Greenhouse-Geisser correction was applied (p = 0.207).
For metatarsal 5 left (M5 left), the significance in the multivariate tests in the factor time of measurement is p = 0.578, in the factor SB p = 0.678 and in the interaction effect
p = 0.706. The Mauchly test for sphericity reached a significance of p = 0.090 in the factor time of measurement and a significance of p = 0.822 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.739) and in the interaction factor (p = 0.718).
For right heel, the significance in the multivariate tests in the factor time of measurement is p = 0.459, in the factor SB p = 0.651 and in the interaction effect p = 0.468. The Mauchly test for sphericity reached a significance of p = 0.487 in the factor time of measurement and a significance of
p = 0.726 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.512) and in the interaction factor (p = 0.481).
For left heel, the significance in the multivariate tests in the factor time of measurement is p = 0.707, in the factor SB p = 0.962 and in the interaction effect p = 0.834. The Mauchly test for sphericity reached a significance of p = 0.131 in the factor time of measurement and a significance of p = 0.512 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.699) and in the interaction factor (p = 0.871).
For the M1 on the right, the percentage load decreased by 1.75% from the 1st to the 3rd measurement. In the measurement with SB, there was an increase of 0.37%. For the M1 on the left, the percentage load decreased from the first to the second measurement and increased again at the third measurement, both without and with SB.
The differences are very small in percentage terms. For the M5 on the right, the pressure load increases by 3.7% without the brace from the first to the third measurement. With the splint, the pressure load is lower than without, except for the 1st measurement. The observed changes in the M5 left heel are 1.5% without and with brace and between the different measurement times. For the right heel, a decrease in the percentage pressure load from the 1st to the 2nd measurement and an increase from the 2nd to the 3rd measurement, without SB, can be observed. With SB, there is a reduction of the pressure load in the 1st measurement.
There is an increase in the last two measurements. In the left heel, the pressure load changed from an average of 52.65% to 52.32%, without SB, from the 1st to the 3rd measurement. With SB, the value changed from 53.04% to 51.84%. The differences between without and with SB within one measurement are less than 1% (Figure 4; Table S1).

Mobility of the cervical spine

For flexion of the cervical spine, the significance in the multivariate tests in the factor time of measurement is p = 0.347, in the factor SB p = 0.084 and in the interaction p = 0.223. The Mauchly test for sphericity reached a significance of p = 0.075 in the factor time of measurement and a significance of p = 0.593 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement
(p = 0.565) and in the interaction factor (p = 0.247). However, a continuous improvement without SB can be observed at the 3 measurement points, from 67.65° to 72.12°. An improvement in flexion with SB can also be seen at measurement time points 1 and 2.
For the extension, the significance in the multivariate tests in the factor time of measurement is p = 0.060, in the factor SB p = 0.485 and in the interaction effect p = 0.965. The Mauchly test for sphericity reached a significance of p = 0.946 in the factor time of measurement and a significance of p = 0.956 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement
(p = 0.029) and in the interaction factor (p = 0.965). From the 1st to the 3rd measurement, the extension without SB increases from 71.35° to 77.8° and with SB from 72.26° to 78.53°. The extension is approx. 1-1.5° better with SB than without.
For the lateral flexion on the right (LF r.) the significance in the multivariate tests in the factor time of measurement is p = 0.012, in the factor SB p = 0.012 and in the interaction effect p = 0.904. The Mauchly test for sphericity reached a significance of p = 0.053 in the factor time of measurement and a significance of p = 0.707 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.001) and in the interaction factor (p = 0.917). From the 1st to the 3rd measurement, it increases without SB. from 47.06° to 56.00°, with SB from 49.65° to 48.65°. With SB the mobility is 2-3° better. The SD deviation increases from the 1st to the 3rd measurement point, and the 95%-CI is also greatest at the last measurement point.
For the lateral flexion on the left (LF l.) the significance in the multivariate tests in the factor time of measurement is p = 0.002, in the factor SB p = 0.270 and in the interaction effect p = 0.166. The Mauchly test for sphericity reached a significance of p = 0.570 in the factor time of measurement and a significance of p = 0.761 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p ≤ 0.001) and in the interaction factor (p = 0.100). Without SB it increases, from the 1st to the 3rd measurement, from 45.82° to 55.82°, with SB from 49.47° to 55.18°. The SD are on average less than 10°.
For the rotation on the right (rot. r.) the significance in the multivariate tests in the factor time of measurement is p = 0.002, in the factor SB p = 0.174 and in the interaction effect p = 0.102. The Mauchly test for sphericity reached a significance of p = 0.849 in the factor time of measurement and a significance of p = 0.014 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.001). Sphericity cannot be assumed in the interaction effects factor. The Greenhouse-Geisser correction was applied (p = 0.318). From the 1st to the 3rd measurement, it increases from 91.24° to 104.88° without SB, and from 94.94° to 104.76° with SB. With SB, the mobility is slightly better, except at the last measurement point.
For the rotation on the left (rot. l.) the significance in the multivariate tests in the factor time of measurement is
p = 0.009, in the factor SB p = 0.922 and in the interaction effect p = 0.800. The Mauchly test for sphericity reached a significance of p = 0.734 in the factor time of measurement and a significance of p = 0.862 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0,008) and in the interaction factor (p = 0.810). Overall, the rotation on the left without SB improves from the 1st to the 3rd measurement from 86.12° to 95.71°, with SB from 87.24 to 95.76°. Only at the 2nd measurement time point is the ROM greater without than with SB, at the last measurement there are hardly any differences.
Fig. 5 and Table S2 gives an overview of the mobility of the cervical spine.

Assessment of the sagittal and frontal plane

To evaluate the changes in the sagittal plane, the distance between the scapula and forehead circumference (S1) and the distance between the lateral malleolus and forehead circumference (S2) were taken. The lines were drawn by hand on the PC and the distances were recorded automatically by the software. There were no statistically significant changes in sagittal D1 and D2. changes (Figure 6). In the frontal plane, the distance from the midline to the right (F1) and left (F2) eye was measured.
For S1, the significance in the multivariate tests in the factor time of measurement is p = 0.956, in the factor SB p = 0.510 and in the interaction effect p = 0.160. The Mauchly test for sphericity reached a significance of p = 0.196 in the factor time of measurement and a significance of p = 0.445 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.970) and in the interaction factor (p = 0.172).
For S2, the significance in the multivariate tests in the factor time of measurement is p = 0.923, in the factor SB p = 0.423 and in the interaction effect p = 0.584. The Mauchly test for sphericity reached a significance of p = 0.609 in the factor time of measurement and a significance of p = 0.359 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.921) and in the interaction factor (p = 0.591).
For F1, the significance in the multivariate tests in the factor time of measurement is p = 0.720, in the factor SB p = 0.979 and in the interaction effect p = 0.065. The Mauchly test for sphericity reached a significance of p = 0.323 in the factor time of measurement and a significance of p = 0.558 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.655) and in the interaction factor (p = 0.061).
For F2, the significance in the multivariate tests in the factor time of measurement is p = 0.538, in the factor SB p = 0.920 and in the interaction effect p = 0.102. The Mauchly test for sphericity reached a significance of p = 0.355 in the factor time of measurement and a significance of p = 0.418 in the interaction effect. Sphericity can therefore be assumed in the factor time of measurement (p = 0.494) and in the interaction factor (p = 0.110).
The distance from the midline to the left eye became smaller from the first to the third measurement time point, and correspondingly larger to the right eye. This indicates a shift to the left in the frontal plane (Figure 6, Table S3).

Evaluation of the questionnaires

The NDI showed a stat. sig. difference of the mean values
(p ≤ 0.001). In the 1st measurement the mean was 7.88 and in the 2nd follow-up 3.00 points, resulting in a difference in means of 4.88. The 95% CI lies between 3.51-6.25 points, with an SD of 2.67 points (Table S4).
Fifteen subjects had grade 1 in the GCPS and 2 subjects had grade 2. There was no change in the grades in the 2nd follow-up. However, there were changes in pain intensity (PI). The mean value of PI was 37.25 in the 1st measurement and 21.96 in the last, resulting in a difference in means of 15.29, which is highly sig. with p ≤ 0.001. The 95% CI lies between 12.02-18.57, with an SD of 6.37 (Table S5).
For MFIQ. the mean was 5.94 (SD 9.52) in the 1st measurement and 1.88 points (SD 3.14) in the 2nd follow-up. The maximum in the 1st measurement is 35 and in the last measurement 10 points. The minimum is zero in each case. Twelve participants improved, one worsened and four subjects did not change. The stat. sig. is p = 0.006 (Table S6, S7).
The EQ-5D-5L shows a stat. sig. difference in the dimension pain (p ≤ 0.001) and the dimension anxiety/depressed (p = 0.020; Table S8).
The mean value of the EQ-VAS was 82.76 points (SD 8.47) at the first measurement point and 93.06 points (SD 3.67) at the second follow-up. The difference between the mean values is thus -10.29 points (SD 6.67; CI: -13.72- -6.87) and is highly significant with p ≤ 0.001 (Table S9). A decrease in the SD from the first to the last measurement is noticeable. This indicates a homogenisation of the group. The assessment of the state of health is already high with an average of 82.76 (out of 100).

Discussion

Primary Outcome

The occlusal references changed with the SB seem to result in positive changes in body statics. With the exception of Speed, there were no statistically significant results. results. Whether these have any clinical relevance cannot be assessed, as no reference values were found. However, a trend towards improvement is visible.
The EA was significantly lower in the 1st measurement with SB than without, which speaks for an immediate effect of the SB. In the 3rd measurement, the values without and with SB are close to each other.
This could be attributed to the wearing time of the SB. In the case of ER, the mean value in the 3rd measurement, without SB is close to 90°, which indicates a rotation around the main axis that is hardly inclined to the right or left. Both EA and ER show quite large 95% CI and partly large SD. This indicates a certain uncertainty of the estimated parameters. When the tonic system is not functioning competently, the body stabilises itself using the arms, legs and head. This balancing is sluggish and the speed is low. A competent system has a high speed (Interview Dilmaghani, K., 20.03.2020). With SB, the speed was higher, which indicates a more stable stand.
The minimal slowing down without SB in the course could also be due to the EA becoming smaller. With the weight difference of the feet, the changes are so small that there is probably no clinical relevance.

Secondary Outcome

The plantar pressure distribution should be as follows: 50% on the heel, about 33% on M1 and 17% on M5 [24]. Kapandji (2009) refers to Morton (1935) for this rule of thumb. There are hardly any differences with or without SB. On average, the tested population loads M1 slightly too little and M5 slightly too much. The loads on the heels are close to the “ideal value”. The changes are minimal and no clinical relevance can be concluded.
In the cervical spine, the sometimes large angles were noticeable (e.g. rot. > 100°). This was despite the fact that the subject’s shoulder girdle was fixed during LF and rotation. A possible reason for the high values could be the age and gender of the population with an averagely high basic mobility. Interfering magnetic fields can almost be excluded, as this was investigated in advance. The sensor is also designed to detect rotations of up to 180°, but with a decrease in measurement accuracy towards the maximum value, due to the linear course of the earth’s magnetic field.
The flexion of the cervical spine did not show any statistically significant changes. The flexion of the cervical spine did not show any statistically significant changes and was also not within the range of the Minimal Detectable Change (MDC). Minimal Clinical Important Differnces (MCID) could not be found in the literature search. All other directions of movement were statistically significant and were within the MDC range [25]. Even if the significance is due to the time factor, it must be remembered that the SB was worn at night during the 6 weeks. Thus, the effect in the factor time can also be attributed to the long wearing of the SB.
In the sagittal plane, an approximation of distance 1 would have indicated an erection of the trunk, shoulder girdle and cervical spine/skull. With distance 2 it could have been checked whether it was mainly due to a cervicothoracic and or (high) cervical extension. This could not be confirmed. There were also no statistically significant differences in the frontal plane. Differences.
In the frontal and sagittal planes, the values are so close together that there is probably no clinically relevant change. The lines were inserted by hand on the PC, which can result in measurement errors.

Patient population

The age of the test persons was chosen because they usually have their own teeth and no dentures. Furthermore, static postural control worsens in 40 to 49 year olds, measured on a force plate [26]. Muscle mass also reduces significantly between 40 and 80 years of age [27,28].

Effect of the occlusal splint

The SB is intended to resolve the adaptive final bite position in bruxism and create a permanent maximum intercuspidation in different jaw positions and thus simulate multiple occlusal norm references. In the present study, statistically significant and clinically relevant results were found in the area of cervical spine mobility. One reason for the clear effect in this outcome could be the anatomical proximity and biomechanical connections between the craniomandibular and craniocervical regions.
Some studies have shown that changes in the stomatognathic system (e.g. through splints) have effects on the spine, the plantar pressure distribution and the deflections of the body’s centre of gravity [29-32].

Questionnaires

The NDI is considered a valid measurement tool [18]. On average, the scores improved statistically significantly by 4.88 points. The MDC is 5 points [33]. The MCID is given between 3.5 -9.5 points [33,34]. Jorritsma et al. (2012) suggests a value of 8,4 points. Scores in the NDI were low overall, making large changes unlikely.
The GCPS is considered valid [17,36,37]. A value for the MCID in relation to the PI of the GCPS could not be found in the literature search.
The MFIQ is also valid [19]. The MFIQ scores were low overall, resulting in an average reduction of only 4.06 points. A total of 68 points are possible in the MFIQ and the MDC is given as 14 points. Most of the test persons were below this value. However, the maximum was 35 in the 1st measurement and 10 in the 2nd follow-up.
The EQ-5D-5L is also valid [38-41]. Most changes occurred from level 2 (slight) to level 1 (no pain or anxiety) (Table S8). With such slight changes, no clear statement can be made about the effect of SB.
In the EQ-VAS, there was a stat. sig. improvement of a total of 10.29 points. Whether this change is clinically relevant would have to be investigated specifically for a population with bruxism.

Limitations

The design of the clinical non-controlled study limits the power of the results. Future studies could examine a larger population, with a more balanced ratio of men and women, to also examine gender differences. A more symptomatic population might better capture changes in the questionnaires. Control groups with other types of OKS and or use in a healthy population would also be conceivable. Similarly, in a given patient population, one group could receive the intervention with SB compared to a control group without intervention to assess the strength of the time factor. Plantar pressure distribution was measured purely statically in the bipedal stance. It would be interesting to investigate whether there are significant changes with SB in single leg stance or walking.

Practical implications

The stressbite establishes occlusal norm references that significantly improve cervical spine ROM and pain intensity and positively influences stabilisation of the body’s centre of gravity. The clinical relevance of some results should be investigated in follow-up studies. Whether reciprocal effects on the neuromuscular control of the masticatory organ can be achieved through targeted therapies on the musculoskeletal system should be further investigated. This could possibly lead to new forms of therapy for the treatment of bruxism.

Acknowledgments, conflict of interest and ­funding

First of all, I would like to thank Kian Dilmaghani (M.Sc. Implantology), with whom I conducted the research project. Special thanks also go to my supervisor PD Dr. med. Patrick Vavken, for his professional support.
A big thank you also goes to André Meichtry (M.Sc. Physiotherapy, M.Sc. Statistics) and Marina Bruderer (M.Sc. Physiotherapy), who gave me and my fellow students feedback on our statistical considerations in the module Biostatistics 3 and helped us with open questions. I would also like to thank Dr. Ea de With, who also supported me with statistical questions via email.
Furthermore, I would like to thank Dr. Otto Kruse and Dr. Morgan Powell, who supervised me and my fellow students in the module Scientific Writing 2 and gave us helpful feedback.
A big thank you also goes to my family and friends who supported me morally and stood by my side during this time.
And last but not least, a special thank you goes to the study participants. Without their interest and commitment, the study would not have been possible.

Corresponding author

Marc Kwidzinski  
Blatterstrasse 16, 8400 Winterthur
Tel: +41 78 751 17 22
Email: marc.k.mscpt@gmail.com

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