| Abstract|| |
Aim: This study describes the relationship of the chronophysiological organization of the lateral teeth occlusion and the parameters of the chewing unit of the human dentofacial system (bioelectric potentials, the force of the masticatory muscles, masticatory efficiency) which should be considered in modeling of prosthesis occlusal surfaces. Materials and Methods: Examination of 200 respondents with a “day” chronotype, with Angle class I bilateral occlusion at the age of 18–35 years was conducted daily for 3 days. From 8.00 to 20.00, every 4 hours, the amplitude of the electromyography, the jaw muscles' force, the masticatory efficiency, the area of the occlusal contacts, and the near-contact zones were determined. Results: The activity of the masticatory muscles increased during the period from 12.00 to 16.00, which coincided with the escalation of the masticatory efficiency and of the occlusal contacts area. The relationship between the occlusal surfaces' relief and masticatory efficiency is described by two types of occlusal surfaces' topography – smoothed and pronounced, differing by the ratio of the areas of the occlusal contacts and the near-contact zones in 0.25- and 1-mm wide. Conclusion: The modeling of the occlusal surface of the permanent prosthetic restorations for patients with the “day” chronotype should be carried out with the area values of occlusal contacts and near-contact zones corresponding to the period of masticatory muscles activity from 12.00 to 16.00 and in accordance with the characteristic type of the occlusal surfaces' relief.
Keywords: Circadian rhythms, jaw muscles, masticatory efficiency, occlusal contacts
|How to cite this article:|
Shemonaev VI, Mashkov AV, Patrushev AS. Circadian dynamics in the functional interaction of the lateral teeth occlusal surfaces' relief. Indian J Dent Res 2020;31:363-7
|How to cite this URL:|
Shemonaev VI, Mashkov AV, Patrushev AS. Circadian dynamics in the functional interaction of the lateral teeth occlusal surfaces' relief. Indian J Dent Res [serial online] 2020 [cited 2020 Sep 23];31:363-7. Available from: http://www.ijdr.in/text.asp?2020/31/3/363/291500
| Introduction|| |
The human body is subjected to daily range and is characterized by increased activity at certain intervals. According to the literature data, masticatory muscles also have their own circadian dynamics, which undoubtedly affect the functioning of the entire dentofacial complex.,,, When the teeth are occluded by the masticatory muscles, occlusal contacts and near-contact zones occur., The near-contact zone is a projection on the occlusal surface of a various thickness space, located between the occlusal surfaces of the antagonist teeth closed in the maximum intercuspal position [Figure 1]. It is supposed that the circadian change in the masticatory muscles activity leads to a change in the area of occlusal contacts and near-contact zones during the day.
|Figure 1: Occlusal contacts and near-contact zones on the teeth joining model|
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When modeling the occlusal surface of dental prostheses, it is important to observe the individual typological ratio of the areas of occlusal contacts and near-contact zones for restoration of the patient's chewing function in full., However, when modeling prosthesis, changes in occlusion, caused by the circadian rhythms of the masticatory muscles, are not taken into account. A chronophysiological approach to the manufacture of permanent prosthetic restorations is the modeling of prosthesis occlusal surfaces with individual typological characteristics of the lateral teeth occlusion within the circadian rhythm. According to the principles of the chronotherapy, the presence of daily fluctuations in occlusal activity requires the modeling of permanent prosthetic restorations' occlusal relief with values of the area of occlusal contacts and near-contact zones corresponding to the maximum activity of the masticatory muscles. It will ensure the maximum conformity of the occlusal surface relief of the dental prostheses with the relief of the patient's natural teeth and, as a result, the earliest adaptation to the prosthesis.
The aim of the study was to determine the relationship of the chronophysiological organization of the lateral teeth occlusion and the parameters of the chewing unit of the human dentofacial system (bioelectric potentials and the force of the masticatory muscles, masticatory efficiency) which should be considered in modeling of prosthesis occlusal surfaces.
| Materials and Methods|| |
A survey of 200 respondents (97 men and 103 women) age 18–35 years with Angle class I bilateral occlusion and intact dentitions was carried out. Small tooth fillings were allowed, occupying no more than 10% of the occlusal surface, not disturbing the occlusal surfaces' relief of the premolars and molars in the places of characteristic occlusal contacts. Subjects with temporomandibular disorders, parafunctional habits, pathological dental abrasion, and periodontal diseases were excluded. The informed consent form was obtained from each respondent at the beginning of the study. This study was approved by the institutional ethics committee. The experimental group included persons without severe medical pathology and mental diseases with similar vegetative status (according to indications of arterial pressure, heart rate, and body temperature) and chronotype (according to the results of the Ostberg test). The prevailing number of respondents was characterized by a “day” chronotype, which indicates the greatest activity of the human organism in the interval from 8.00 to 20.00 (this time interval coincides with the working time of outpatient dental clinics).
To reveal the relationship between the chronophysiological organization of the lateral teeth functional interaction and the parameters of the chewing unit of the dentofacial system daily for 3 days in the period from 8.00 to 20.00, surface electromyography of the masticatory muscles with the device “Neuromyoanalyzer NMA-4-01 NEYROMIAN” and gnathodinametry in the region 1.6–4.6 and 2.6–3.6 teeth using the “Vizir-E” device were conducted to each of the respondents with an interval of 4 hours. An assessment of the masticatory function was carried out during the day every 4 hours in the dynamics (8.00, 12.00, 16.00, 20.00) with the help of the masticatory function test based on the degree of mixing of the two-color vinyl polysiloxane impression material during chewing process. The impression material of both colors was shaped as 1-cm3 balls and given to each respondent for chewing it in 20 chewing movements. Then the chewing mass was placed between two glass plates for flattening and photographed from two sides. The photographs of the reference color masses were also taken. The mixing quality of two masses and the masticatory efficiency were analyzed by measuring the ratio of the mixed colors' area to the total area of the chewed mass. The area of mixed colors was found by excluding the reference color areas from the total area using the RGB-scale in the software Adobe Photoshop.
The control of occlusal relationships was carried out by measuring the area of occlusal contacts and near-contact zones with the help of an occlusion record using baseplate wax. After the registration of occlusal contacts on the wax plate, it was photographed to the light with the wax samples in 0.25-, 0.5-, 0.75-, and 1-mm thickness. Using the RGB-scale in Adobe Photoshop, the areas of occlusal contacts and near-contact zones were found by matching the colors of the occlusion record wax plate with the colors of wax samples.
The circadian dynamics simulations of the dentofacial system parameters were carried out by the method of cosinor analysis using the software “Cosinor for Excel.”
For the assessment of the functional interaction of the occlusal surfaces' relief, the masticatory efficiency was compared with the area of occlusal contacts and the near-contact zones of the teeth masticatory surfaces. The area of occlusal contacts and the near-contact zones was evaluated as a percentage of the total area of the occlusal surfaces' impression. According to the results of the chewing test, all the respondents were divided into three groups in conformity with the degree of masticatory efficiency. The first group of respondents was represented by persons with high masticatory efficiency (60% and more), the second group with an average masticatory efficiency (40%–60%), and the third group with low masticatory efficiency (up to 40%).
Data analysis was carried out using descriptive statistics with the help of Microsoft Office Excel 2010 software. Statistical analysis of the data was conducted by comparing mean values. For each parameter, the arithmetic mean, the standard deviation, and the standard error were calculated. The statistical significance in the results obtained was evaluated by Student's t-test (t). The differences were considered statistically significant for the 95% confidence interval and t >2.
| Results and Discussion|| |
The diagnostic manipulations in persons of the “day”-type performed in the established time intervals showed that the greatest activity of the dentofacial system's components was observed at 16.00. The activity of the masticatory muscles increased during the period from 12.00 to 16.00, which coincided with the escalation of the masticatory efficiency and of the occlusal contacts' area. An inverse relationship between the parameters of the area of near-contact zones and the parameters of electromyography and gnathodynamometry was identified. These differences are statistically significant (P < 0.05). No significant differences in circadian activity of dentofacial system parameters were found between men and women.
Daily range in the dentofacial system's parameters is confirmed by modeling the circadian rhythm of these parameters using the method of cosinor analysis [Figure 2], [Figure 3], [Figure 4], [Figure 5].
|Figure 5: Chronogram of changes in the area of near-contact zone in 1 mm thickness|
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Thus, the dependence of the antagonistic teeth reliefs' functional interaction, expressed in the masticatory efficiency, on the activity time of the jaw muscles is revealed. The increasing strength of the masticatory pressure results in a more dense teeth joining, which is reflected in the ratio of the area of the occlusal contacts and near-contact zones. It confirms the important role of the occlusal surface relief in the transfer of the masticatory pressure and, in particular, the dependence of this index on such biometric characteristic as the occlusal contacts' area.
The diagnostic manipulation results clearly correlate with the time interval of their measurements in accordance with the obtained data of the dentofacial system parameters. It indicates the circadian activity of the dentofacial system elements.
When studying the relationship between masticatory efficiency and the occlusal surfaces' relief of the teeth, a significant change in the area of occlusal contacts and near-contact zones in 0.25-, 0.75-, and 1-mm thickness was found (the data are statistically significant, P < 0.05) in the absence of fluctuations in the area of the near-contact zones in 0.5 mm (no statistical differences, P < 0.05) in comparison groups [Table 1].
|Table 1: Ratio of the areas of the occlusal contacts and the near-contact zones, depending on masticatory efficiency (as a percentage of total occlusal area)|
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The average area of occlusal contacts in group I (respondents with high masticatory efficiency) is 2.44 times higher than the similar index in group III (the differences are statistically significant, P < 0.05) and corresponds to the index of group II. The area of the near-contact zones in 1 mm in the group with a low masticatory efficiency is 1.5 times higher in comparison to the group of respondents with a high chewing efficiency. The near-contact zones in 0.25 mm in the experimental group I are significantly higher than this parameter in groups II and III (1.5 and 1.6 times, respectively), without significant differences in the area of this near-contact zone in the last two groups. In group III, in comparison to group I, the area of the near-contact zone in 0.75 mm is 1.2 times higher.
When assessing the significance of the differences in the mean values of the area of the occlusal contact and the near-contact zones within the experimental groups, it was found that in group I there are no differences between the near-contact zones in 1 and 0.25mm, and between occlusal contacts and near-contact zones in 0.5 mm. There are no significant differences in the average area between the near-contact zone in 0.5 mm and the occlusal contacts in group II. In group III, the area mean value of the occlusal contacts and all near-contact zones differs significantly. No significant differences in the obtained data were found between men and women.
According to the received data, the relief of the occlusal surface is characterized by the ratio of occlusal contacts and near-contact zones, in particular, in 0.25- and 1-mm thickness. Thus, the smoothed relief of the occlusal surface (ROS I) is characterized by a slight prevalence of the area of the near-contact zones in 0.25-mm thick above the near-contact zones in 1-mm thick and also a large area of occlusal contacts. The pronounced relief of the occlusal surface (ROS II) differs by the prevalence of the area of the near-contact zones in 1 mm above the near-contact zones in 0.25 mm with a smaller total occlusal contacts' area (the differences between the area mean values of the near-contact zones in 1 and 0.25 mm in experimental group III are statistically significant, P < 0.05) [Figure 6] and [Figure 7].
|Figure 6: Example of dentitions fragments' with ROS I type (occlusal contacts – blue, near-contact zones in 0.25 mm thick – green, in 1 mm thick – yellow)|
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|Figure 7: Example of dentitions fragments' with ROS II type (occlusal contacts – blue, near-contact zones in 0.25 mm thick – green, in 1 mm thick – yellow)|
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The mean value statistical analysis within the experimental groups indicates a more uniform distribution of the near-contact zones and occlusal contacts on the masticatory surface in respondents with a high masticatory efficiency, while in group III there is a significant predominance of near-contact zones in 1 and 0.75 mm above the occlusal contact area.
At the same time, there is a clear dependence of masticatory efficiency on the expressiveness of the occlusal surface. Patients with a smoothed relief of the occlusal surface have a greater masticatory effect and, presumably, a grinding type of chewing. The masticatory efficiency of patients with a pronounced occlusal surface relief is low. Such patients are characterized by a crushing type of chewing.
| Conclusion|| |
The presented results of the study testify to the presence of circadian dynamics in the functional interaction of the occlusal surface reliefs of the dentitions. It is explained by changes in the activity of the jaw muscles, which is confirmed by a daily range in the parameters of the electromyography and gnathodynamometry. Similar fluctuations are observed in the indexes of masticatory efficiency and the area of occlusal contacts. The function of the jaw muscles has a direct effect on the functional interaction of the antagonist teeth occlusal surfaces, which plays a key role in the perception and transmission of the masticatory pressure.
The revealed differences in the occlusal surfaces' relief of the dentitions, based on the ratio of the areas of the occlusal contacts and near-contact zones, allow to distinguish two varieties of occlusal surfaces' reliefs. ROS I is characterized by smoothness of the relief, which allows achieving high masticatory efficiency, while in ROS II the expression of the occlusal surface relief is higher and the masticatory efficiency is lower.
The results obtained in the study can be used to develop a prosthodontic treatment regimen with a chronophysiological approach. The revealed patterns of the occlusal surfaces' relief structure of the dentitions and the circadian dynamics of their interaction require from the orthopedist and dental lab technician the manufacture of permanent dental prostheses, taking into account the individual typological features of the occlusal surface relief.
The maximum masticatory muscles' activity of patients characterized by a “day” chronotype is observed in the period from 12.00 to 16.00. Thus, the modeling of the occlusal surface of the permanent prosthetic restorations should be carried out with the area values of occlusal contacts and near-contact zones corresponding to this time interval. Fixation of the prefabricated dental prosthesis in this case is also recommended during the period of the patient's daily peaks of the masticatory muscles' force. It will improve the patient's adaptation to permanent prosthetic restorations and ensure the recovery of the masticatory function in full.
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Conflicts of interest
There are no conflicts of interest.
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Dr. Anton Sergeevich Patrushev
10, Komsomolskaya st., 126, Volgograd, 400066
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]