A survey on the potential relationships between TMD, possible sleep bruxism, unilateral chewing, and occlusal factors in Turkish university students

A nomogram for predicting the risk of temporomandibular disorders in university students

OBJECTIVES

Temporomandibular disorders (TMDs) have a relatively high prevalence among university students. This study aimed to identify independent risk factors for TMD in university students and develop an effective risk prediction model.

METHODS

This study included 1,122 university students from four universities in Changchun City, Jilin Province, as subjects. Predictive factors were screened by using the least absolute shrinkage and selection operator (LASSO) regression and the machine learning Boruta algorithm in the training cohort. A multifactorial logistic regression analysis was used to construct a TMD risk prediction model. Internal validation of the model was conducted via bootstrap resampling, and an external validation cohort comprised 205 university students undergoing oral examinations at the Stomatological Hospital of Jilin University.

RESULTS

The prevalence of TMD among university students was 44.30%. Ten predictive factors were included in the model, comprising gender, facial cold stimulation, unilateral chewing, biting hard or resilient foods, clenching teeth, grinding teeth, excessive mouth opening, malocclusion, stress, and anxiety. The model demonstrated good predictive ability with area under the receiver operating characteristic curve (AUC) values of 0.853, 0.838, and 0.821 in the training cohort, internal validation cohort, and external validation cohort, respectively. The calibration curves demonstrated that the predicted results were consistent with the actual results, and the decision curve analysis (DCA) indicated the model's high clinical utility.

CONCLUSIONS

An online nomogram of TMD in university students with good predictive performance was constructed, which can effectively predict the risk of TMD in university students. The model provides a useful tool for the early identification and treatment of TMDs in university students, helping clinicians to predict the probability of TMDs in each patient, thus providing more personalized and accurate treatment decisions for patients.

Evaluation of the effect of unilateral mastication on the morphology of temporomandibular joint from the perspective of dynamic joint space

BACKGROUND

Unbalanced alterations of temporomandibular joint morphology were associated with unilaterally masticatory habits.

OBJECTIVE

This study aimed to investigate the effect of unilateral mastication on the remodelling of the temporomandibular joint using dynamic joint space.

METHODS

Twelve volunteers with non-maxillofacial deformity and healthy temporomandibular joints were recruited. The 3D models of the mandible and the maxilla were reconstructed according to computed tomography. The subjects were asked to masticate French fries and peanuts unilaterally, which was recorded by a 3D motion capture system. The dynamic joint space during unilateral mastication was analysed.

RESULTS

During early closure, the joint space reduction on the non-masticatory side was significantly greater than on the masticatory side (p < .05). During later closure, the joint space reduction on the non-masticatory side was significantly lower than that on the masticatory side (p < .05). The difference in joint space reduction between both sides was greater than the French fries while masticating the peanuts.

CONCLUSIONS

Unilateral mastication resulted in a different major pressure area on the bilateral TMJs. Therefore, unilateral mastication might be an essential factor in the bilateral asymmetrical remodelling of the TMJ.

Occurrence of Cervical Spine Pain and Its Intensity in Young People with Temporomandibular Disorders

Background: The main aim of this cross-sectional study was to compare the occurrence and severity of cervical spine pain in young adults diagnosed with TMDs with a healthy control group (without TMDs). Methods: The study was conducted from June to July 2023. Inclusion criteria were age (18-30 years), cervical spine pain (for at least 1 month), and consent to participate in the study. The study was conducted based on RDC/TMD protocol, an original questionnaire, and a physiotherapeutic examination focused on detecting TMDs. The cervical pain level was assessed using the Visual Analogue Scale (VAS). Thus, a total of 95 subjects were registered for the trials, 51 people (53.7%) constituted the control group (without TMDs), while 44 (46.3%) people constituted the study group (with TMDs). Results: The mean age of people participating in the study was 22.2 ± 2.2 years in the study group and 22.5 ± 3.1 years in the control group. The largest group was people aged 21-25 (n = 51 people, 53.7%). Patients from the study group more often experienced pain in the stomatognathic system during palpation (both in the muscle, joint, and musculoskeletal groups) and had reduced mobility of the temporomandibular joints in every movement (p < 0.001). People from the study group were also characterized by less mobility of the cervical spine (p < 0.05), apart from extension movement (p > 0.05). The analysis showed that of the 95 people participating in the study, 85.4% reported problems in the cervical spine area (n = 81), of which almost all people in the study group struggled with this problem (n = 43, 97.7%). It was found that cervical spine pain was significantly more common in people with TMDs (p < 0.05, chi2 = 10.118, df = 1, rc = 0.31). The level of pain was significantly higher in people from the study group (p < 0.001, chi2 = 45.765, df = 4, rc = 0.57). Conclusions: Our research has shown that the occurrence of cervical spine pain is more common in the group of young people with temporomandibular disorders (TMDs). In young people, this problem is rarely recognized and properly treated.

Effects of occlusal conditions on masseter and temporalis muscle activity: An electromyographic evaluation

Introduction

Dental occlusion contributes to the development of temporomandibular disorder.

Objective

This case control study examined the influence of different occlusal conditions on the surface electromyography (sEMG) of the superficial part of the masseter muscle (MM) and anterior part of the temporalis muscle (TA) during clenching in the maximum intercuspal position (MIP).

Materials and methods

Twelve healthy subjects had their anterior, right posterior, or left posterior teeth added by composite resin to generate the bilateral posterior, unilateral left, or unilateral right posterior tooth losses, respectively. Muscle activity in the resting stage, MM's and TA's maximum voluntary clenching (MVC; µV) in MIP, each muscle activity's symmetry (%), and ipsilateral MM and TA synergy (%) were measured by sEMG. All parameters were analyzed by SPSS version 23.0, and the significance level was set at p < 0.05.

Results

The MM's and TA's sEMG activity at the resting stage significantly differed from those at the other occlusal conditions (p < 0.05). Both muscles' MVC were highest at the MIP during clenching but lowest during anterior clenching. During unilateral posterior clenching, such MVC was higher at the occluding than at the non-occluding sides. The TA's symmetry during clenching at the anterior and unilateral posterior teeth was lower than that at the MIP during clenching. No significant difference was seen in the ipsilateral MM and TA synergy.

Conclusion

Different occlusal conditions influenced the MM's and TA's sEMG activity. Each masticatory muscle responded differently to the same occlusal conditions.

The association between sleep quality, depression, anxiety and stress levels, and temporomandibular joint disorders among Turkish dental students during the COVID-19 pandemic

OBJECTIVE

This study aimed to examine the association between sleep quality, depression, anxiety and stress levels, and the frequency of temporomandibular disorders in a sample of Turkish dental students during the COVID-19 pandemic.

METHODS

The current cross-sectional study was conducted with 699 dental university students during the COVID-19 pandemic. Fonseca Anamnestic Index (FAI), Pittsburgh Sleep Quality Index (PSQI), and Depression Anxiety Stress Scale-21 (DASS-21) were used in the present study.

RESULTS

The incidence of temporomandibular joint disorders in the present study was found to be 77.5%. Female students' FAI scores were found to be statistically significantly higher than males (p < 0.05). Additionally, higher depression and anxiety and stress levels caused increased PSQI and FAI scores.

CONCLUSION

During the COVID-19 pandemic, increased temporomandibular joint disorders were observed with increased impaired sleep quality and higher depression, anxiety and stress levels among dental university students.

Remodeling dental anatomy vs sham therapy for chronic temporomandibular disorders. A placebo-controlled randomized clinical trial

BACKGROUND

Evidence regarding the etiology or effective treatments for chronic orofacial pain, the majority diagnosed as temporomandibular disorder (TMD), is limited.

PURPOSE

To investigate whether occlusal equilibration therapy (ET) and decreasing the (higher) angle of the lateral guidance on the nonworking-side leads to a reduction in chronic TMDs intensity.

METHODS

It was conducted a randomized, explanatory, single blind with blinded assessment, placebo-controlled trial with strong protection against bias involving patients with chronic TMDs. Participants were randomly assigned to receive equilibration therapy or sham therapy. ET in this study consisted of minimal invasive occlusal remodeling to obtain balanced occlusion with reduction of the steeper angle of lateral mandibular movement with respect to the Frankfort plane. The primary outcome was a change in the pain intensity score (on a 0-10 point scale, with 0 indicating no pain and 10 the worst possible pain) at month 6. Secondary outcomes include maximum unassisted mouth opening and psychological distress.

RESULTS

A total of 77 participants underwent randomization, 39 of whom received ET and 38 sham therapy. The trial was stopped early for efficacy, according to preestablished rules when 67 participants (n = 34, n = 33, respectively) had completed the analysis. At month 6, the mean unadjusted pain intensity score was 2.1 in the ET and 3.6 in the sham therapy group (adjusted mean difference, -1.54; 95% confidence interval [CI] -0.5 to -2.6; P = 0.004; ANCOVA model). The mean increase in maximum unassisted mouth opening (main secondary outcome) was significantly higher in the real therapy group (adjusted mean difference 3.1 mm, 95% CI 0.5-5.7, p = 0.02).

CONCLUSION

ET significantly reduced the intensity of facial pain associated with chronic TMDs and increased maximum unassisted mouth opening, as compared with sham therapy, over the course of 6 months. There were no serious adverse events. Funded by the Instituto de Salud Carlos III from the Ministry of Science and Innovation of the Government of Spain and European Regional Development Fund, Grant nº PI11/02507; "una manera de hacer Europa".

Research progress in effect of chewing-side preference on temporomandibular joint and its relationship with temporo-mandibular disorders

Chewing-side preference is one of the risk factors for temporomandibular disorders (TMD), and people with chewing-side preference is more prone to have short and displaced condyles, increased articular eminence inclination and glenoid fossa depth. The proportion of TMD patients with chewing-side preference is often higher than that of the normal subjects. Clinical studies have shown a strong correlation between chewing-side preference and TMD symptoms and signs; and animal studies have shown that chewing-side preference can affect the growth, development, damage and repair of the mandible. After long-term unilateral mastication, changes in the stress within the joint cause the imbalance of temporomandibular joint (TMJ) structural reconstruction, the transformation and even destruction of the fiber structure of masticatory muscle, resulting in uncoordinated movement of bilateral muscles. The joint neurogenic diseases caused by the increase of neuropeptide substance P and calcitonin-gene-related-peptide (CGRP) released locally by TMJ may be the mechanism of TMD. This article reviews the research progress of the influence of chewing-side preference on the structure of TMJ, the relationship between chewing-side preference and TMD, and the related mechanisms.

Temporomandibular disorder prevalence and its association with oral parafunctions, neck pain, and neck function in healthcare students: A cross-sectional study

OBJECTIVE

To determine the temporomandibular disorder (TMD) prevalence in female students and to assess its association with oral parafunctions, neck pain, and function.

METHODS

One hundred forty-four participants were included. The severity of TMD was assessed with Fonseca's Anamnestic Index (FAI). The oral parafunctions were self-reported with the Oral Behaviors Checklist (OBC). Neck pain and neck function were recorded with the Core Outcome Measure Index (COMI). The Spearman correlation analysis was used for statistical analysis.

RESULTS

Seventy participants (48.6%) had mild TMD. All participants had a positive OBC score, which indicated an oral parafunction. A moderate correlation between TMD and oral parafunctions (p < 0.001) was detected.

DISCUSSION

TMD is common in female healthcare students, and its presence is associated with oral parafunctions, neck pain, and function. It is recommended to evaluate oral health habits and neck pain and function in females with TMD.

COVID-19 vaccination and psychological status of Iranian dental students

Objective

The purpose of the present study was to investigate the association of COVID-19 vaccination with the quality and quantity of sleep, the level of stress, and temporomandibular joint (TMJ) disorders (TMDs) in Iranian dental students.

Materials and methods

In this cross-sectional research, we applied a questionnaire including 30 questions on the Perceived Stress Scale (PSS), sleep quality and quantity, Diagnostic Criteria for Temporomandibular Disorders (DC/TMD), and vaccination status. All vaccinated students of the dental schools located in the city of Tehran were invited to participate in the study. Participants were divided into three groups: those vaccinated for less than a month, those vaccinated for 1-3 months, and those vaccinated for more than 3 months. A paired t-test served for statistical analysis.

Results

Overall, 171 out of 235 students (72.77%) completed the questionnaire, among which 90 individuals were fully vaccinated, and were included in the data analysis. Stress levels decreased (mean difference = -1.23, p-value = 0.002) and sleep quality and quantity improved mostly 1-3 months after the vaccination (mean difference = -0.5, p-value = 0.016). However, TMD symptoms were mostly alleviated in people vaccinated for more than 3 months (mean difference = -2.86, p-value <0.05). In this respect, no significant difference was observed between the two genders.

Conclusion

According to the results of the study, vaccination was associated with the improvement of psychological consequences of the COVID-19 pandemic. It is recommended that further longitudinal studies be conducted on larger sample sizes and different age groups by using various data collection methods (especially regarding the assessment of TMD).

The effect of mandibular movement on temporomandibular joint morphology while eating French fries

BACKGROUND

The preferred masticatory side was reported to be almost always the same as the affected side of the temporomandibular disorder. Unbalanced alterations of temporomandibular joint morphology were found to be associated with unilaterally masticatory habits. The aim of this study was to investigate the effect of the mandibular movement on the remodeling of temporomandibular joint during eating French fries using a 3D motion capture system.

METHODS

Twelve volunteers with non-maxillofacial deformity and a healthy temporomandibular joint were recruited. The 3D models of the mandible and the maxilla were reconstructed according to computed tomography. The subjects were asked to eat French fries by unilaterally mastication, which was recorded by a 3D motion capture system. The trajectories of the incisors and the condyles and the condylar acceleration during unilateral mastication were analyzed.

RESULTS

During incisal biting, there was no significant difference in the condylar trajectories between the left and right sides (P > 0.05). During unilateral mastication, the average displacement and acceleration of the masticatory condyles were significantly lower than those of the non-masticatory condyles (P < 0.05). The trajectory angles of the masticatory condyles were significantly steeper than those of the non-masticatory condyle (P < 0.05). During swallowing, there was no obvious movement of the mandible.

CONCLUSIONS

Between both temporomandibular joints, unilateral mastication resulted in significant differences in the regions of the condylar movement within the articular fossa, and then caused different compressive regions of the temporomandibular joints. Thus, unilateral mastication might result in a significantly different pattern of temporomandibular joint remodeling between the two sides.

Oral health-related quality of life and psychological states of dental students with temporomandibular disorders

PURPOSE/OBJECTIVES

This study investigates the frequency of temporomandibular disorders (TMD) in dental students, and evaluates the association between TMDs, psychological states, and oral health-related quality of life (OHRQoL). The presence of bruxism was also determined.

METHODS

Two hundred ninety-three dental students completed the Symptom Checklist 90-Revised (SCL-90-R) and Oral Health Impact Profile 14 (OHIP-14) questionnaires and underwent a clinical examination according to Diagnostic Criteria for TMDs.

RESULTS

TMDs were detected in 46.4% of the dental students. OHIP-14 scores of students with TMDs were significantly higher than scores for students without TMDs (p < 0.05). Significant differences were observed in all SCL-90-R scores among students with and without TMDs, except for phobic anxiety and additional SCL-90-R subscale scores (p < 0.05). The prevalence of myalgia was significantly higher in clinical students (26.6%) than in preclinical students (15.6%). OHIP-14 scores of clinical students were significantly higher than preclinical students (p < 0.05).

CONCLUSIONS

In dental students, there was a high frequency of TMDs and bruxism. OHRQoL was poorer in clinical students. Levels of anxiety, depression, and somatization were not different in clinical and preclinical students. SCL-90-R scores are higher in students with TMDs except for phobic anxiety and additional SCL-90-R subscale scores.

A comparative study of condyle position in temporomandibular disorders patients with chewing side preference using cone-beam computed tomography

BACKGROUND

Chewing side preference (CSP) could cause structural and morphological changes of temporomandibular joint (TMJ) and has been suggested as one etiology of temporomandibular disorders (TMDs), but the condylar position in TMD patients with CSP is unknown.

OBJECTIVE

To compare the condylar position in the TMD patients with and without CSP.

METHODS

Ninety TMD patients with unilateral symptom (69 with CSP and 21 without CSP) and 20 asymptomatic participants received cone-beam computed tomography. The condylar position was determined based on the measurements of sagittal joint spaces. Intergroup and intragroup comparisons of the condylar position were performed.

RESULTS

The condyles in asymptomatic participants located nearly randomly in anterior, centric, and posterior positions. Patients without CSP had significantly more posterior condyles than asymptomatic participants (57.1% vs 30.0%, P<0.05). In patients with CSP, 50.7% of the condyles on the preferred chewing side and 42.0% on the unpreferred side located posteriorly, reaching no significant level compared with the asymptomatic participants and patients without CSP (P>0.05). The symptomatic joints and asymptomatic joints in patients with CSP and without CSP showed no significant differences in condylar position. While patients without CSP had significantly more posterior condyles in symptomatic joints than asymptomatic participants (P<0.05), patients with CSP showed a trend towards more posterior condyles in symptomatic joints compared with the asymptomatic participants (53.6% vs 30.0%, P=0.054).

CONCLUSION

Condylar position is not a strong indicator to differentiate CSP-related TMDs from none-CSP-related TMDs. Posterior condyle could not be viewed as one indicator of TMD.

Temporomandibular disorders among medical students in China: prevalence, biological and psychological risk factors

BACKGROUND

The purpose of the present study is to evaluate the prevalence of temporomandibular disorders (TMD) and their associated biological and psychological factors in Chinese university students.

METHODS

A total of 754 students were included from Zunyi Medical University, each participant completed questionnaires and clinical examinations according to the Diagnostic Criteria for Temporomandibular Disorders.

RESULTS

The overall prevalence of TMD was 31.7% among medical students. Subjects with TMD had a high prevalence of bruxism, empty chewing, unilateral chewing, chewing gum, anterior teeth overbite, anterior teeth overjet, depression, anxiety, and sleep disturbance. Moreover, sleep bruxism, empty chewing, unilateral chewing, anterior teeth overbite, depression, and anxiety were the strongest risk factors for TMD.

CONCLUSIONS

Individuals with TMD have a high prevalence of psychological distress and oral parafunctional habits. Except for the psychological factors associated with TMD, bruxism, abnormal chewing, and malocclusion also shared similar risks for TMD.

Changes of the condylar cartilage and subchondral bone in the temporomandibular joints of rats under unilateral mastication and expression of Insulin-like Growth Factor-1

OBJECTIVES

This study aimed to define changes in the rat condylar cartilage and subchondral bone using the unilateral mastication model.

MATERIALS AND METHODS

In this study, forty 4-week-old Wistar rats were randomly divided into experimental (n = 20) and control group (n = 20). In the experimental group, unilateral dental splints were placed on the occlusal surface of left maxillary molars. The rats were sacrificed at 1, 2, 3, and 4 weeks after placement of the splint. Micro-CT scanning and histological staining were performed to observe the changes in the mandibular condylar cartilage and subchondral bone. Levels of insulin-like growth factor-1 (IGF-1) were determined via immunohistochemistry to analyse the occurrence of osteogenic changes.

RESULTS

Micro-CT scanning findings demonstrated the occurrence of asymmetric growth of condyle in the experimental group. The condylar cartilage and subchondral bone exhibited degradation on the chewing side of the experimental group and showed decreased bone mineral density, thinner cartilage thickness, and increased degree of degeneration and osteoclast activity. Compared with the control group, the expression of IGF-1 was remarkably higher on the non-chewing side.

CONCLUSION

Long-term unilateral mastication can lead to the occurrence of degenerative changes in the condylar cartilage and subchondral bone during growth and development. IGF-1 may play a role in promoting the process of osteogenesis.

Cone-beam computed tomographic assessment of the inclination of the articular eminence in patients with temporomandibular disorders and chewing side preference

Background

Chewing side preference (CSP) has been proposed as one etiology of temporomandibular disorders (TMDs) as it can induce the structural changes of the temporomandibular joint. But its association with the inclination of the articular eminence (IAE) is unknown. This study aimed to compare IAE between patients with CSP and without CSP.

Methods

Cone-beam computed tomography images of 90 patients with TMD (mean age of 45.6 years, 69 with CSP, 21 without CSP) and 20 participants without TMD and CSP (mean age of 41.3 years) were measured to compare IAE and depth of the glenoid fossa (DGF)

Results

IAE and DGF showed a positive correlation among all the participants. Compared with the participants without TMD and CSP, the TMD patients without CSP presented a similar IAE but with a significantly higher value of DGF (p < 0.05); in contrast, the TMD patients with CSP presented a significantly greater IAE and DGF (p < 0.05). No bilateral differences in IAE and DGF were observed in all the participants. Except the male patients with CSP had a deeper fossa than did the female, no differences in IAE and DGF according to gender were observed.

Conclusions

TMD patients with CSP seem to have a deep glenoid fossa with steep eminence which might be considered one characteristic imaging feature.

Temporomandibular disorders in patients with polysomnographic diagnosis of sleep bruxism: a case-control study

BACKGROUND

Temporomandibular disorders (TMD) is a collective term that refers to complaints of temporomandibular joint (TMJ) pain, fatigue and/or pain of the craniocervical muscles, limitation of movement of the mandible, and TMJ noises. Sleep bruxism (SB) is a disorder involving rhythmic (phasic) or non-rhythmic (tonic) masticatory muscle activity during sleep and is not a movement disorder or a sleep disorder in otherwise healthy individuals. The present study aimed to support or reject the null hypothesis that there is no association between SB and TMD.

METHODS

The study population was recruited from patients who visited the Artmedica Clinic, Mossoro city, Rio Grande do Norte, Brazil. Patients who underwent polysomnography received information about the research and were invited to participate following the inclusion and exclusion criteria. The study sample consisted of 40 individuals with age ranging from 19 to 76 years. The subjects were administered the questionnaire of the European Academy of Craniomandibular Disorders (AEDC). Those who answered affirmatively to at least one question of the questionnaire were recommended to visit the primary researcher's dental clinic for examination; those who met the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) were evaluated, and their condition was classified into one or more subtypes of TMD. The subjects were divided into 4 groups according to the polysomnographic findings and the responses to the AEDC questionnaire. Of the 40 individuals who answered the AEDC questionnaire and underwent polysomnography, 28 presented with TMD symptoms. The data were expressed as simple frequency and percentage values using statistical software. Values of p < 0.05 were considered to be significant.

RESULTS

The results showed that the frequency of TMD in individuals diagnosed to have SB was 46.4%. According to the DC/TMD of the 28 individuals, the most prevalent TMD subtype was local myalgia (85.7%). Of the total subjects, 32.5% had TMD and SB, 36.4% were males, and in the age range of 31 to 40 years (40%).

CONCLUSION

In this study sample, there was no association between SB as currently defined and TMD, thus confirming previous findings on this topic.

Oral behaviors, bruxism, malocclusion and painful temporomandibular joint clicking: is there an association?

The present cross-sectional case-control study aimed to determine if there is an association between specific oral behaviors, sleep bruxism (SB), awake bruxism (AB), and painful temporomandibular joint (TMJ) clicking. Ninety individuals were dived into three groups; Group 1 (n = 30): painful TMJ clicking; Group 2 (n = 30): painless TMJ clicking; and Group 3 (n = 30): control group. The following clinical data were studied: oral behaviors (unilateral chewing, gum chewing, nail biting, foreign objects biting, leaning with jaw against the hand, and sleeping in a position that pressures the jaw), SB, AB (including the frequency in 10 days, evaluated by ecological momentary assessment), and malocclusions investigated based on clinical inspections (anterior open bite, posterior cross-bite, abnormal overbite/overjet, occlusal guidance, mediotrusive and/or laterotrusive interferences, retruded contact position to maximum intercuspation slide, missing posterior teeth). All statistical tests (Kolmogorov-Smirnov, chi-square, and one-way ANOVA) were performed with a 5% significance level. Group 1 had the highest frequency of and a significant association with leaning with jaw in the hand, sleeping position that pressures the jaw, gum chewing, nail biting, and AB (p<0.05). Gum chewing, nail biting, and AB were associated with Group 2 only when compared to Group 3 (p<0.05). No significant difference among groups was found for other behaviors (unilateral chewing and foreign objects biting), SB, and all malocclusions (p>0.05). It can be concluded that patients with painful TMJ clicking had a higher frequency of and a significant association with some specific harmful behaviors and AB.

Asymmetry of dental or joint anatomy or impaired chewing function contribute to chronic temporomandibular joint disorders

INTRODUCTION

The etiologies of most chronic temporomandibular joint disorders are unknown. However, an association between habitual chewing on a particular side and chronic temporomandibular joint disorders has been reported. The aim of this study was to investigate the differences between sides (affected vs unaffected) of biodynamic factors (including lateral dental guidance determined by dental anatomy) or condylar path angles (determined by temporomandibular joint morphology) and chewing function (physiological alternate chewing vs single habitual chewing side). The study scope was to investigate possible etiological factors to improve the understanding of temporomandibular joint disorders. The null hypothesis was that no difference would be found between sides that are or are not affected by chronic temporomandibular joint disorders in chewing function or in levels of dental or temporomandibular joint remodeling.

METHODS

This cross-sectional, double-blind study involved 24 adults with substantial, chronic, unilateral symptoms diagnosed as temporomandibular joint disorders. Chewing function, temporomandibular joint remodeling (using axiography) and dental anatomy (lateral guidance angles using kinesiography) were assessed.

RESULTS

Habitual chewing on one particular side was observed in 17 of 24 participants; significantly more (n=15) chewed on the affected side than on the unaffected side (P=0.002 in a two-tailed Fisher's exact test; risk estimate=4.5; 95% CI 1.326-15.277). The condylar path (CP) angle was steeper on the affected side than on the unaffected side (mean (standard deviation)=50.52° (9.98°) versus 45.50° (7.98°); P=0.002 in a two-tailed t-test). The lateral guidance (LG) angles were flatter on the affected side in all 24 participants.

CONCLUSION

Our results suggest that habitual chewing on one side may be associated with increasing condylar path, with flattening lateral guidance angles, and also with chronic temporomandibular joint disorder on the habitual chewing side.

Sleep bruxism and temporomandibular disorders: A scoping review of the literature

OBJECTIVE

To provide a scoping review of the literature by assessing all the English-language papers that investigated the relationship between sleep bruxism (SB) and temporomandibular disorders (TMDs).

STUDY DATA AND SOURCES

A search was performed in the National Library of Medicine (PubMed) and Scopus databases, in order to identify all the articles published assessing the relationship between SB and TMDs, by several different approaches. The selected articles were then structurally read and summarized in PICO tables. The articles were selected independently by the two authors.

STUDY SELECTION

Out of 185 references that were initially retrieved, 47 articles met the inclusion criteria and were thus included in the review. The studies were divided into four categories based on the type of SB assessment: 1. questionnaire/self-report (n = 26), 2. clinical examination (n = 7), 3. electromyography (EMG) (n = 5), and 4. polysomnography (PSG) (n = 9).

CONCLUSIONS

Studies based on questionnaire/self-report SB featured a low specificity for SB assessment, and in general they found a positive association with TMD pain. On the contrary, instrumental studies (i.e., electromyography, polysomnography) found a lower level of association or even a negative relationship between SB and TMD pain. Findings from this updated review confirmed the conclusions of a previous review by Manfredini & Lobbezoo, suggesting that literature findings on the relationship between SB and TMDs are dependent on the assessment strategies that are adopted for SB. Future studies should consider SB as a multifaceted motor behavior that must be evaluated in its continuum spectrum, rather than using a simplified dichotomous approach of presence/absence.

Possible sleep and awake bruxism, chronotype profile and TMD symptoms among Turkish dental students

It was hypothesized that an individual's chronotype profile has an effect on the performance of work or study tasks. Dental students have to cope with both academic and clinical workloads, and the latter requires extra concentration. The first aim was to evaluate the association of sleep bruxism (SB) and awake bruxism (AB) with sleep related items, temporomandibular disorder (TMD) complaints, and chronotype profile; the second aim was to evaluate the association between complaints of TMD and chronotype profile among dental students. The present cross-sectional descriptive study involved 218 dental students whose ages ranged between 18 and 30 years. In order to gather data, students were required to respond to a questionnaire, which aimed to evaluate possible SB and possible AB occurrence and demographics, sleep-related items and complaints of TMD. For the assessment of the chronotype profile, the morningness-eveningness questionnaire (MEQ) was used. The chi-square test, the Mann-Whitney U test, and t-test analyses were performed to evaluate the factors associated with SB, AB and chronotype profile. The frequency of self-reported SB was 25.2% and AB was 28.9%. The prevalence in the eveningness profile who reported possible AB was 45.3%, while it was 24.2% in intermediate individuals and 18.8% in the morningness profile. An association was also found between possible AB and eveningness chronotype profile (p = .009). No association was found between other temporomandibular joint (TMJ) pain and noise and chronotype profiles (p > .05). An association was found between possible AB and eveningness chronotype profile but no association was found between possible SB and chronotype profile. Moreover, complaint of TMD (face, head, neck pain) was observed particularly in students with an eveningness profile.

Identifying predictive factors for sleep bruxism severity using clinical and polysomnographic parameters: a principal component analysis

STUDY OBJECTIVES

The aim was to identify predictive factors for sleep bruxism (SB) severity among polysomnographic parameters, salivary cortisol levels, temporomandibular disorders, age, and sex.

METHODS

Young adults (19-30 years) were screened for self-/roommate reports of teeth grinding/clenching during sleep associated with clinical signs of tooth wear. Individuals positive for both conditions were administered a polysomnographic exam to provide a definite diagnosis of SB (n = 28). Healthy participants without SB signs/symptoms were also included (n = 15). The Research Diagnostic Criteria for Temporomandibular Disorders was applied to determine functional, muscular, and articular domains of the Temporomandibular Index. Cortisol awakening levels were measured in saliva. Principal component analysis was used to extract the latent components emerging from polysomnographic results, and 2 regression models were adjusted to predict the number and duration of bruxism episodes.

RESULTS

Principal component analysis resulted in 4 components-C1: %N1, total sleep time, sleep efficiency, arousals/microarousals; C2: %N2, %N3; C3: periodic limb movements and apneas; C4: %REM and REM latency. The number of SB episodes/h was predicted by increasing muscular scores and C2 (decrease in %N2 and increase in %N3) (adjusted R² = 45%; P =.001). The total time of SB episodes was predicted by decreased articular and increased functional scores, age, and female sex (adjusted R² = 36%; P = 0.010). Salivary cortisol levels were not associated with SB severity and did not differ between groups.

CONCLUSIONS

The findings showed that SB severity was predicted by muscular and functional scores, female sex, and distinct polysomnographic patterns, contributing to the deeper knowledge of the underlying pathophysiology of SB severity; additionally, the findings can help to formulate health approaches that are specific to the patient and will better assist in treating this condition.

An evaluation of peri-implant marginal bone loss according to implant type, surgical technique and prosthetic rehabilitation: a retrospective multicentre and cross-sectional cohort study

To evaluate implant loss (IL) and marginal bone loss (MBL); follow-up period of up to 10 years after prosthetic loading. Retrospective multi-centre cross-sectional cohort study. Double analysis: (1) all the implants (n = 456) were analysed; (2) to allow for possible cluster error, one implant per patient (n = 143) was selected randomly. Statistical analysis: Spearman's correlation coefficient; Kruskal-Wallis (post-hoc U-Mann-Whitney); Chi-square (post-hoc Haberman). (1) Analysing all the implants (456): IL was observed in patients with past periodontitis (6 vs. 2.2%, p < 0.05), short implants (12 vs. 2.8%, p < 0.001) and when using regenerative surgery (11.3 vs. 2.9%, p < 0.001); greater MBL was observed among smokers (0.39 ± 0.52 vs. 0.2 ± 0.29, p < 0.01), maxillary implants (0.28 ± 0.37 vs. 0.1 ± 0.17, p < 0.0001), anterior region implants (0.32 ± 0.36 vs. 0.21 ± 0.33, p < 0.001), external connection implants (0.2 ± 0.29 vs. 0.63 ± 0.59, p < 0.0001), and 2-3 years after loading (p < 0.0001). (2) analysing the cluster (143): IL was observed in smokers (18.8 vs. 3.5%, p < 0.05), splinted fixed crowns (12.9%, p < 0.01), short implants (22.2 vs. 4.0%, p < 0.01) and when using regenerative surgery (19.2 vs. 3.4%, p < 0.01); greater MBL was observed in maxillary implants (0.25 ± 0.35 vs. 0.11 ± 0.18, p < 0.05), in the anterior region (p < 0.05), in the first 3 years (p < 0.01), in external connection implants (0.72 ± 0.71 vs. 0.19 ± 0.26, p < 0.01) and in short implants (0.38 ± 0.31 vs. 0.2 ± 0.32, p < 0.05). There is greater risk in smokers, patients with past periodontal disease, external connection implants, the use of short implants and when regenerative techniques are used. To prevent MBL and IL, implantologists should be very meticulous in indicating implants in patients affected by these host factors.

The Reliability of MyotonPRO in Assessing Masseter Muscle Stiffness and the Effect of Muscle Contraction

BACKGROUND Temporomandibular disorders (TMD) are accompanied by masticatory muscle-related pain, making it meaningful to assess the stiffness of the masticatory muscles. The present study investigated the intra- and inter-operator reliabilities of MyotonPRO for assessing the elasticity of masseter muscles, to determine minimal detectable changes, and to quantify changes in stiffness from conditions of relaxation to maximal contraction. MATERIAL AND METHODS Twenty healthy subjects (10 men and 10 women) were recruited. The stiffness of their masseter muscles was quantified with MyotonPRO in both relaxed and maximal contraction conditions. Two experienced operators (A and B) measured stiffness on the same day, and operator A repeated this procedure 5 days later. RESULTS Intra-rater reliability was good (ICC=0.78) and inter-operator reliability was excellent (ICC=0.95) for assessing masseter muscle stiffness with MyotonPRO. The mean stiffness of the masseter muscle on the dominant side was 369.5 N/m under relaxed conditions and 618.3 N/m at maximum bite force, an increase of 67.4%. Stiffness on the dominant and non-dominant sides did not differ significantly under both conditions (P>0.05). CONCLUSIONS MyotonPRO is a reliable method for quantifying the stiffness of the masseter muscle and monitoring its changes under different contraction conditions.

Changes in masticatory laterality 3 months after treatment with unilateral implant-supported fixed partial prosthesis

OBJECTIVE

This study assessed changes in masticatory laterality in patients with unilateral posterior missing teeth 3 months after treatment with an implant-supported fixed partial prosthesis (ISFPP).

METHODS

Thirty patients with unilateral posterior missing teeth participated in this prospective study. They were treated with one-, two- or three-unit ISFPPs. The control group comprised 10 healthy individuals with complete natural dentition. Each participant performed masticatory assays at baseline and at 3-month follow-up, chewing pieces of silicon inside a latex bag. Masticatory laterality was determined using three different methods: assessment of the first chewing cycle, of all cycles and application of a visual analogue scale. Data were compared using the Kruskal-Wallis or the Mann-Whitney U test as appropriate.

RESULTS

Three months after treatment, a significant change in the asymmetry index towards the treated side and a significant reduction in the Unilateral Chewing Index were observed in the ISFPP group. No significant differences in masticatory laterality between groups were detected at 3-month follow-up, regardless of the method assessed.

CONCLUSION

Treatment with ISFPPs alters the masticatory laterality, moving it to the treated side and increasing the degree of bilateral chewing in patients with unilateral posterior missing teeth.

The correlation between sleep bruxism, salivary cortisol, and psychological status in young, Caucasian healthy adults

Objective: To analyze the association between sleep bruxism (SB), salivary cortisol, and psychological state in healthy adults.Methods: Sixty healthy students (with or without SB) were included in the study. The subjects completed a questionnaire that evaluated the presence of SB and analyzed the general and work-related psychological states and job-related frustration. Clinical examinations of TMJs and dental wear were performed. The salivary cortisol was determined using ELISA technique.Results: Subjects with SB had a general status characterized by anxiety or stress compared to subjects without SB. They also presented a work-induced depressive or anxious attitude compared to healthy individuals. The salivary cortisol levels were higher in subjects with SB and in females and were correlated with subjects' general anxiety, but not with a job-induced psychological state.Conclusion: SB is correlated with general and job-induced psychological changes. Salivary cortisol could be a non-invasive marker for the evaluation of SB severity.

Temporomandibular joint disorder determined by Fonseca anamnestic index and associated factors in 18- to 27-year-old university students

OBJECTIVE

The aim of this study was to investigate temporomandibular disorder (TMD) and associated risk factors.

METHODS

This study was conducted using 212 university students. Based on the Fonseca anamnestic index, the population was divided into two groups: those with TMD and those without TMD. The two groups were compared in terms of global body posture, craniohorizontal and craniovertebral angles, neck and temporomandibular joint range of motion, stress level, and sleep quality.

RESULTS

Stress level, sleep quality, and left cervical rotation were found to have statistical differences between the groups (p = 0.00, 0.00, and 0.046, respectively). Sleep quality and stress level were found to be important risk factors for the presence of TMD (p = 0.017 and 0.00, respectively).

DISCUSSION

In the prevention and treatment of TMD, a holistic approach that evaluates mechanical factors and psychosocial factors should be adopted.

Changes in the temporomandibular joint disc and temporal and masseter muscles secondary to bruxism in Turkish patients

Objectives:

To analyze the relationships between temporalis and masseter muscle hypertrophy and temporomandibular joint (TMJ) disc displacement in patients with severe bruxism using magnetic resonance imaging (MRI).

Methods:

This retrospective study included 100 patients with severe bruxism, referred to the Department of Oral and Maxillofacial Surgery, University of Marmara and Istanbul Medipol University, Istanbul, Turkey, between January 2015 and December 2016. Patients underwent TMJ MRI with a 1.5-T system in open and closed mouth positions. The masseter and temporalis muscles were measured in the axial plane when the patient’s mouth was closed.

Results:

At its thinnest, the disc averaged was 1.11±0.24 mm. At their thickest, the masseter averaged was 13.65±2.19 mm and temporalis muscles was 12.98±2.4 mm. Of the discs, 24% were positioned normally, 74% were positioned anteriorly, and 2% were positioned posteriorly. The temporalis muscle was significantly thicker in patients with normally positioned discs than in those with anteriorly positioned discs (p=0.035).

Conclusions:

The temporalis muscle was significantly thicker in patients with normally positioned discs than in those with anteriorly positioned discs (p=0.035). Additional studies should be conducted to evaluate the relationships between all masticatory and surrounding muscles and disc movements in patients with bruxism.

Study of Associated Factors With Probable Sleep Bruxism Among Adolescents

STUDY OBJECTIVES

To evaluate the prevalence of probable sleep bruxism (SB) and its association with sleep features, orthodontic fixed appliance wearing, and extraoral and intraoral clinical signs and symptoms in a population of adolescents.

METHODS

Two hundred thirty-nine 12-year-old adolescents enrolled in private and public schools in Brumadinho, southeast Brazil, and their parents were invited to participate. They answered a questionnaire containing information regarding adolescents' sleep features and history of SB. Extraoral and intraoral examination was performed to identify some clinical signs (ie, absence of lip competence, presence of mouth breathing, clicks in the temporomandibular joint [TMJ], tooth wear) and symptoms (ie, pain in the masseter muscle upon palpation), and ongoing orthodontic treatment with fixed appliances. Parental report and clinical examination were used to determine probable SB. Descriptive statistics and logistic regression were performed to identify association of probable SB with independent variables.

RESULTS

Of 239 adolescents initially selected, 231 (96.6%) participated in the study. Prevalence of probable SB was 16.9%. Adolescents who snored during sleep (odds ratio [OR] = 3.14; 95% confidence interval [CI] = 1.47-6.70), adolescents who did not have clicks in the TMJ (OR = 3.37; 95% CI = 1.11-10.15), and those who wore orthodontic appliances (OR = 2.72; 95% CI = 1.04-7.14) were more likely to be in the group with probable SB.

CONCLUSIONS

Snoring, absence of clicks in the TMJ, and fixed appliance wearing were associated with probable SB among adolescents. This study adds to the ongoing research on SB in adolescents and its associated factors.

COMMENTARY

A commentary on this article appears in this issue on page 1281.

Jaw biodynamic data for 24 patients with chronic unilateral temporomandibular disorder

This study assessed 24 adult patients, suffering from severe chronic unilateral pain diagnosed as temporomandibular joint (TMJ) disorder (TMD). The full dentate patients had normal occlusion and had never received an occlusal therapy, i.e., were with natural dental evolution/maturation. The following functional and dynamic factors were assessed: (1) chewing function; (2) TMJ remodeling or the condylar path (CP); and (3) lateral jaw motion or lateral guidance (LG). CPs were assessed using conventional axiography, and LG was assessed by K7 jaw tracking. Seventeen (71%) of the 24 (100%) patients consistently showed a habitual chewing side. The mean (standard deviation [SD]) of the CP angles was 47.90 (9.24) degrees. The mean (SD) of the LG angles was 42.95 (11.78) degrees. Data collection emerged from the conception of a new TMD paradigm where the affected side could be the habitual chewing side, the side with flatter lateral jaw motion or the side with an increased CP angle. These data may lead to improved diagnosis, therapy plans and evolution in TMD patients.