Functional Analysis of Rhythmic Jaw Movements Evoked by Electrical Stimulation of the Cortical Masticatory Area During Low Occlusal Loading in Growing Rats

Evaluation of occlusal bite force distribution by T-Scan in orthodontic patients with different occlusal characteristics: a cross sectional-observational study

BACKGROUND

The aim of orthodontic treatment, apart from esthetic and functional corrections, is uniform force distribution. Hence Occlusal analysis using a T scan gives scope for a precisely targeted treatment plan. The T-scan evaluation of occlusal force, time, and location of contacts from initial occlusal contact to maximum intercuspation enables the orthodontist to sequentially balance the occlusal forces on the right and left sides through specific treatment plan options.

OBJECTIVE

The current study aimed to determine the force distribution in the different individuals by using a T-Scan as well as the net discrepancies of forces generated at a maximum intercuspation position in the first molar region between the left and right sides of the mouth.

METHODS

This is a descriptive-correlational study that was carried out in Ras Al Khaimah College of Dental Sciences clinics and Ajman University clinics from January 2020 to September 2022 by using the convenience sampling technique. The T-scan III Novus was employed in this investigation to record multi-bite scans for several patients. T-scan was utilised to examine various malocclusions.

RESULTS

The present study consisted of 158 participants. Analysis of Variance (ANOVA) showed that there is a statistically significant difference in the percentage of force between the three types of malocclusions (I, II, and III) on the right molar side (B-16 and B-46) (p < 0.05). Moreover, the overall discrepancy showed a statistically significant difference in the three types of malocclusion classifications (p < 0.05). On the other hand, there was no statistically significant difference in the percentage of force between B-26 and B-36 (p > 0.05). Post hoc analysis showed a statistically significant difference in the percentage of force between malocclusion classes I and III on the right molar, with a mean difference of 4.11190 (p < 0.05). Similarly, there was a statistically significant difference in B-46 between Malocclusion Classes I and II, 4.01806 (p < 0.05). Additionally, post hoc analysis showed a statistically significant difference between malocclusion classes I and III, with a mean difference of -4.79841 (p < 0.05) on the right molar.

CONCLUSION

The T-Scan is a useful tool for assessing occlusal discrepancies and can be helpful during treatment planning and follow-up, especially for orthognathic surgery patients. A T-scan could be used in orthodontic therapy in a simple and efficient way. Also, it turned out to be a useful tool for diagnosing problems and gave us new information about how therapies work. In this study, T-Scan showed that it can measure occlusal forces in timing in an objective, accurate, and repeated manner. The current study found that T-Scan was better able to report the difference in the percentage of force on the right molar side than on the left side.

Effect of Obesity on Masticatory Muscle Activity and Rhythmic Jaw Movements Evoked by Electrical Stimulation of Different Cortical Masticatory Areas

This study investigates rhythmic jaw movement (RJM) patterns and masticatory muscle activities during electrical stimulation in two cortical masticatory areas in obese male Zucker rats (OZRs), compared to their counterparts-lean male Zucker rats (LZRs) (seven each). At the age of 10 weeks, electromyographic (EMG) activity of the right anterior digastric muscle (RAD) and masseter muscles, and RJMs were recorded during repetitive intracortical micro-stimulation in the left anterior and posterior parts of the cortical masticatory area (A-area and P-area, respectively). Only P-area-elicited RJMs, which showed a more lateral shift and slower jaw-opening pattern than A-area-elicited RJMs, were affected by obesity. During P-area stimulation, the jaw-opening duration was significantly shorter (p < 0.01) in OZRs (24.3 ms) than LZRs (27.9 ms), the jaw-opening speed was significantly faster (p < 0.05) in OZRs (67.5 mm/s) than LZRs (50.8 mm/s), and the RAD EMG duration was significantly shorter (p < 0.01) in OZRs (5.2 ms) than LZR (6.9 ms). The two groups had no significant difference in the EMG peak-to-peak amplitude and EMG frequency parameters. This study shows that obesity affects the coordinated movement of masticatory components during cortical stimulation. While other factors may be involved, functional change in digastric muscle is partly involved in the mechanism.

Evaluation of occlusion parameters using T-scan III in patients receiving fixed orthodontic treatment

Objectives:

The aim of this study is to examine the relationship between occlusal factors and temporomandibular joint diseases (TMD).

Material and Methods:

In our study, 43 individuals who had fixed orthodontic treatment and 20 individuals who did not need treatment at Istanbul Aydin University Faculty of Dentistry Department of Orthodontics were included in the study. Evaluations were made at the beginning of treatment (T0) and at 6 months (T1). T-Scan® computerized Occlusion Analyzer was used to evaluate the number of contact points, occlusal force parameters during centric occlusion and lateral movements, and occlusion and disclusion times. Differences between groups were evaluated with Mann–Whitney or independent t-test, and within-group differences were evaluated with Wilcoxon sign test or paired t-test, depending on whether the data showed normal distribution or not.

Results:

There was no statistically significant distinction between the gender-based parameters and right and left joint of Joint Vibration Analysis record in all three groups (P > 0.05). At the beginning of orthodontic treatment, there was no statistical difference in the variables within the group and between the groups. As a result of the comparison between the beginning of treatment (T0) and the 6th month (T1), no significant difference was found between the parameters of the anterior/posterior occlusal force distribution of the right-left quadrant and the force distribution of the working and non-working sides in lateral movements, and the occlusion and disclusion time parameters. Maximum intercuspal position left/right (MxlntlTSCANT1) was found to be statistically significant at 6 months in individuals who received fixed orthodontic treatment with extraction compared to the none xtraction treatment group (P < 0.05).

Conclusion:

According to our research, T-scan is one of the best devices for the early detection of TMD, especially for people undergoing orthodontic treatment. T-scan offers fast, non-invasive, and repeatable occlusion recording.

Examination of chewing performance with extraction and non-extraction fixed orthodontic treatment – A prospective clinical 1-year study

Objectives:

It shows that patients receiving orthodontic treatment may have a risk of developing temporomandibular disorder symptoms. The aim of this study is to examine the changes in the chewing system of occlusal contact parameters related to joint vibrations, chewing patterns, and measured excursive movements in fixed and non-extractive orthodontic treatments.

Material and Methods:

A total of 43 individuals with premolar extraction (n = 23) and without extraction (n = 20) who applied to the Department of Orthodontics, Dentistry Faculty of Istanbul Aydin University and needed orthodontic treatment were included in the study. In this study, 43 active fixed orthodontic treatment patients were conducted at the beginning (T0) and 6th month (T1) and 12th month (T2) on the parameter recorded during chewing. For occlusion analysis, T-Scan® computerized occlusion analysis recording and examination of the chewing pattern were used for JVA and JT temporomandibular joint parameters. Depending on whether the data showed normal distribution or not, differences between groups were evaluated using the Mann–Whitney or independent t-test, and intragroup differences were evaluated using the Wilcoxon sign test or paired t-test.

Results:

At the beginning, 6th month and 12th month of orthodontic treatment, it was observed that the opening, closing, and occlusion times and joint vibration frequencies in the chewing pattern in cases with and without tooth extraction, the integral value differences of total integral, and frequencies below 300 Hz and above 300 Hz were statistically significant (P < 0.001). In digital occlusion analysis values, the right-left differences were not found statistically significant in the measurements made in cases with and without extraction (P > 0.05), while there were statistically significant differences in disclusion values at the beginning, 6th and 12th months (P < 0.05).

Conclusion:

At the beginning of the orthodontic treatments with or without extraction, it was observed that the values at the joint level changed significantly in the 6th month. However, the changes in the joints during the treatment, when they return to their ideal values at the end of the 12th month, are more than the change in occlusion.

BBS7-SHH Signaling Activity Regulates Primary Cilia for Periodontal Homeostasis

Objectives: Mechanical stimuli are essential for the maintenance of periodontal ligament (PDL) homeostasis. Although there are several studies on atrophic changes in PDL due to occlusal hypofunction, the underlying mechanism is still unknown. Here, we aimed to explore the changes of gene expression in occlusal hypofunctional PDL and elucidate the related role in maintaining the PDL homeostasis.

Methods: To investigate the transcriptomic difference between control and hypofunctional PDL tissue from patients, RNA sequencing was performed on 34 human teeth. The atrophic changes in PDL were evaluated by histological analysis. The effect of the Bardet-Biedl syndrome 7 (BBS7) knockdown was evaluated by the RT-qPCR, Western blot, wound healing, and tubule formation assay.

Results: We detected that the expression of BBS7 was downregulated in occlusal hypofunctional PDL through RNA sequencing. Dynamic changes, including the number of periodontal ligament cells, alignment of collagen fibers, diameter of blood vessels, appearance of primary cilia, and torturous oxytalan fibers, were observed following occlusal hypofunction. Furthermore, Sonic hedgehog signaling (Shh) activity was closely associated with BBS7 expression in PDL cells. In addition, the cell migration and angiogenesis were also suppressed by BBS7 knockdown in vitro.

Conclusion: We suggest that BBS7 plays an essential role in maintaining Shh signaling activity for PDL homeostasis.

Effects of low occlusal loading on the neuromuscular behavioral development of cortically-elicited jaw movements in growing rats

The effect of altered occlusal force on masticatory-related neuromuscular control, which projects from the anterior part of the cortical masticatory area (A-CMA), during growth remains unclear. This study sought to evaluate the effect of occlusal hypofunction on neuromuscular development of jaw muscle activities and cortically-induced rhythmic jaw movements (RJMs) in growing rats. Sixty-four 2-week-old male albino Wistar rats were divided into the control (fed normal diet) and experimental (fed soft diet) groups soon after weaning. Electromyographic activity was recorded at 5, 7, 9, and 11 weeks from the right masseter and anterior digastric along with RJMs. We found a significantly longer onset latency and smaller peak-to-peak amplitude in the experimental group than that in the control group. The RJMs showed an increase in gape size and lateral excursion until up to 9 weeks in both groups. However, both the average gape size and lateral excursion were significantly smaller in the experimental group than that in the control group after 9 weeks. The jaw movement pattern also showed a significant decrease at the maximum opening period in the experimental group. Our findings indicate that inadequate occlusal function during growth alters neuromuscular control of masticatory behaviors and impairs the pattern of RJMs.