Skeletal pattern in subjects with temporomandibular joint disorders

Impact of Dental Midline Shift on the Perception of Facial Attractiveness in Young Adults

Background/Objectives: The aim of this study was to quantify the threshold of a dental midline shift that would compromise facial attractiveness and indicate a need for treatment from the points of view of laypeople and dental professionals. Methods: Whole-face natural photographs of a male and a female model were digitally manipulated to create various degrees of upper and lower dental midline shifts through bodily movement of the upper or lower midlines as well as alteration of the axial inclination of the upper teeth. The samples were then assessed by two groups of observers (laypeople (LP) and dental professionals (DP)). Results: The lower midline shift did not negatively affect the DP and LP's perceptions of smile attractiveness. The first significant loss of attractiveness was registered by the DP with an upper midline shift of 1 mm in the female model. However, the LP registered this at 2 mm. The DP registered the necessity of treatment at a threshold of 2 mm in the female model and 3 mm in the male model. LP identified the need for treatment at 3 mm for both males and females. The female model was judged more critically than her male counterpart by both female and male observers. Conclusions: DP assess the midline deviation more critically than LP. Both DP and LP were more sensitive to midline deviations in the female model regardless of their own gender. Both groups registered the need for treatment at a higher threshold than the reduction in smile attractiveness.

Effect of the magnitude of condylar head displacement on the TMJ function in skeletal class II patients undergoing different degrees of mandibular advancement: A retrospective comparative study

PURPOSE

This study aimed to compare the condylar head displacement (CHD) after bilateral sagittal split ramus osteotomy (BSSO) between different degrees of mandibular advancement in skeletal class II patients and to evaluate whether the temporomandibular joint (TMJ) function would be affected.

PATIENTS AND METHODS

Fifty-nine patients (118 condyles) were included in this retrospective study and were divided into three groups based on the distance of mandibular advancement. The CHD in three directions, x (sagittal direction), y (coronal direction), and z (axial direction), was measured before operation (T0), immediately after operation (T1), and at least 6 months after operation (T2), and the TMJ function of patients was followed up and scored using the Helkimo index system. All the abovementioned data were statistically analyzed, and p < 0.05 was considered the statistical difference standard.

RESULT

During the BSSO surgery, the condyle was predominantly displaced in a lateral, posterior, and superior direction whenever in T1 and T2, even though the degree of CHD was different. Regarding the amount of CHD, the large advancement group was higher than the other two groups in T1 and T2 (p＜0.01). The Helkimo index scores of the three groups were evaluated, and there was no significant statistical difference between the Ai and Di index of the three groups.

CONCLUSION

In our center, CHD occurred in lateral, posterior, and superior directions following mandibular advancement in skeletal class II patients, with a positive correlation between the CHD and the mandibular advancement; however, the TMJ function of the three groups did not show significant differences.

Prevalence and associated factors of myofascial pain in orthognathic patients with skeletal class II malocclusion

Orthognathic patients with skeletal class II malocclusion frequently suffer from myofascial pain (MP).

PURPOSE

This study aimed to evaluate the prevalence and associated factors of MP in these patients.

METHODS

This cross-sectional study was performed in adult patients with skeletal Class II malocclusion requiring orthognathic surgery. They were divided according to the presence or absence of MP. The predictor variables were craniofacial morphology, sex, temporomandibular disorders, chronic pain, depression, and polymorphisms of dopamine receptors DRD2 (rs6275 and rs6276) and ANKK1 (rs1800497) genes. Data were submitted to statistical analyses using the linear regression model and Poisson regression with a significance level of 0.05.

RESULTS

Sixty-five individuals were selected, of which 50 (76.92%) were females. A total of 21 (32.3%) patients had MP. Individuals with MP showed a decrease in the mandible gonial angle (p = 0.042) and an increased risk of having temporomandibular joint (TMJ) disc displacement (p = 0.003), TMJ pain (p = 0.030), chronic pain (p = 0.001), and severe depression (p = 0.015). Additionally, individuals carrying AA and AG genotypes in rs6275, and CC genotype in rs6276, were more likely to have MP (p < 0.05).

CONCLUSION

In this study, 32.3% of skeletal class II orthognathic patients had MP, which was associated with a decreased gonial angle, TMJ disc displacement, TMJ pain, chronic pain, depression, and polymorphisms in the DRD2 gene.

Analysis of the relationship between condylar changes and anterior disc displacement with reduction: a preliminary study

OBJECTIVES

To predict temporomandibular joint (TMJ) anterior disc displacement with reduction (ADDWR) from condylar shape, position, and dimensions obtained from CBCT images.

METHODS

This cross-sectional study was performed on 17 patients suffering from temporomandibular disorders diagnosed by history taking according to the chart of the American Association of orthodontists, clinical examination according to the Helkimo index and MRI. CBCT and MRI examinations were performed within one-week interval. Disc position, diagnosed by MRI was used as the gold standard. TMJs with posterior disc displacement or anterior disc displacement without reduction were excluded. Qualitative and quantitative analyses were performed on CBCT images to find the correlation between condylar variables and ADDWR. A logistic regression model was created to estimate ADDWR from condylar dimensions (height, width and depth).

RESULTS

Condylar shape and condylar position in the glenoid fossa were significantly correlated with ADDWR (P < 0.05). Condylar width, height and depth were significantly smaller in condyles with ADDWR compared to condylar dimensions in normal disc position. Logistic regression analysis could be used to predict the probability of anterior disc displacement with reduction from condylar dimensions.

CONCLUSION

Condylar shape, position, and dimensions assessed by CBCT are significantly correlated with ADDWR of the TMJ. Substituting the values of condylar width, height and depth in the equation suggests the probability of ADDWR.

The association between problematic smartphone use and the severity of temporomandibular disorders: A cross-sectional study

Objective

To evaluate the prevalence of different types of temporomandibular disorders (TMD) symptoms in young adults and determine their associations with problematic smartphone use (PSU).

Methods

The data of the study were collected from local university students through an online questionnaire survey. Demographic information, Fonseca Anamnestic Index (FAI), Smartphone Addiction Scale-Short Version (SAS-SV), and Patient Health Questionnaire-4 (PHQ-4) responses were gathered electronically and analyzed using multiple logistic regression analysis.

Results

There were 163 male and 307 female respondents were participated in this study. The prevalence of PSU and TMD were 83.6% and 66.4%, respectively. There was a moderate statistical correlation between PSU and TMD among young adults (r = 0.31, p < 0.01). The logistic regression model revealed that the risk of TMD was 1.77 times higher in people with PSU than in those without PSU (OR = 1.77; 95% CI 1.04-3.06). PSU is a risk factor for pain-related TMD (OR = 1.81; 95% CI 1.08-3.04) but not intra-articular TMD.

Conclusion

Subjects showed high prevalence of both TMD and PSU. People with PSU experienced more severe and frequent pain-related rather than intra-articular TMD symptoms than those without PSU. By reducing the problematic smartphone use, the risk factor of TMD might be avoided.

Evaluation of the Mandibular Condyle Morphologic Relation before and after Orthognathic Surgery in Class II and III Malocclusion Patients Using Cone Beam Computed Tomography

Simple Summary

In individuals with severe malocclusions, orthognathic surgery seeks to rebalance the relationships between the jaws by providing a stable occlusion, a healthy muscle balance, and the functioning of the temporomandibular joint. Cone beam computed tomography may be used to determine the position of the mandibular condyle in the glenoid fossa. This study aimed to assess how the position of the mandibular condyle varies in class II and III malocclusions before and after bimaxillary orthognathic surgery. Before and after orthognathic surgery, 56 TMJs from 28 patients were studied. Following surgery, both class II and class III patients experienced changes in the anterior joint space, posterior joint space, condyle position, and condyle angle. The preliminary findings are promising for determining changes in condyle position and joint spaces that might guide oral and maxillofacial surgeons to address a debilitating clinical affliction.

Abstract

This study aimed at evaluating the mandibular condyle position changes before and after bimaxillary orthognathic surgery in class II and III malocclusion patients. CBCT scans from patients who underwent bimaxillary orthognathic surgery were analyzed: Le Fort I osteotomy and bilateral sagittal split osteotomy (BSSO). Both condyles were independently assessed for their largest anterior and posterior joint spaces, smallest medial joint spaces, and condyle angles concerning the transverse line. In the sagittal plane, the minimum size of the anterior and posterior joint spaces was measured. In the coronal plane, the smallest medial joint space was measured. The position of the condyle within the glenoid fossa was determined before and after surgery. A total of 56 TMJs from 28 patients were studied. Following orthognathic surgery, the anterior and posterior space in class II increased. Postoperatively, the anterior joint space in class III decreased. In 42.85% of malocclusion class II patients and 57.14% of malocclusion class III patients, the pre-and post-surgical position of the condyle changed, the condyle was anteriorly positioned (42.85%) in class II patients and centrically positioned (71.4%) in class III patients. Significant changes in the joint space, condylar position, and condyle angle were found in the class II and class III subjects.

TMJ Position in Symmetric Dentofacial Deformity

The aim of this research was to analyze the facial class, presence of malocclusion, and the mandibular plane and to relate this to the mandibular condyle position. A cross-sectional study in subjects under analysis for orthognathic surgery was done. The mandibular plane, the gonial angle, and the molar class were included to compare the coronal and sagittal position of the condyle and the joint space observed in the CBCT. The measurements were obtained by the same observer at an interval of two weeks. In addition, the Spearman test was performed to determine the correlation using a p value < 0.05 to observe any significant differences. Eighty-nine male and female subjects (18 to 58 years old, 24.6 ± 10.5) were included. In the coronal section, subjects with CIII had a greater mediolateral distance (MLD, p = 0.0001) and greater vertical distance (SID, p = 0.0001) than subjects with CII. In terms of the skeletal class and the mandibular plane, it was observed that subjects in the CII group had a greater mandibular angle (open angle) (p = 0.04) than the CII group and was related to the anterior position of the condyle. The most anterior condylar position was observed in the CII group (p = 0.03), whereas a posterior condylar position was significant in CIII subjects (p = 0.03). We can conclude that the sagittal position of the TMJ was related to the mandibular plane and the skeletal class showing a higher mandibular angle and most anterior position of the condyle in CII subjects and a lower mandibular angle and most posterior position of the condyle in CIII subjects. The implications for surgical treatment have to be considered.

Temporomandibular Joint Disk Displacements in Class II Malocclusion and Cervical Spine Alterations: Systematic Review and Report of a Hypodivergent Case with MRI Bone and Soft Tissue Changes

(1) Background: This study aimed to perform a literature review related to disk displacement (DD) in class II malocclusion or cervical vertebrae position alterations and to report a hypodivergent case with cervical pain and right anterolateral DD with reduction, left anterolateral DD with reduction, and left joint effusion. (2) Methods: A structured electronic search was conducted between March 2022 and April 2022, without time limits, following PRISMA guidelines, in the following databases: PubMed, Scopus, Embase and Cochrane; the terms “disc displacement”, “disk displacement”, “temporomandibular joint”, “class II malocclusion” and “cervical vertebrae” are searched. (3) Results: the following thirteen publications are included in this review: two prospective studies and eleven cross-sectional studies; for evaluating disk position, eight included publications used magnetic resonance imaging (MRI), whilst six studies used lateral cephalogram to determine craniofacial morphology and relationships between the cranial base, vertical skeletal pattern, maxilla and mandible. (4) Conclusions: although the literature still shows contradictory opinions, a relationship between temporomandibular disorders and cervical posture has been shown in the presented case as well as in the literature review.

Craniofacial Morphology of Orthodontic Patients with and without Temporomandibular Disorders: A Cross-Sectional Study

Purpose

We aimed to explore the relationship between temporomandibular disorders (TMDs) and craniofacial morphology in orthodontic patients.

Methods

Altogether, 262 orthodontic patients were included and divided into two groups according to their Fonseca Anamnestic Index (FAI) scores: a no-TMD group (control group, FAI < 20) and a TMD group (FAI ≥ 20). Cephalometric parameters including cranial, maxillary, mandibular, and dental parameters were traced on cephalograms. Craniofacial morphology was compared between TMD and control groups, followed by subgroup analyses based on TMD severity, gender, age, and temporomandibular joint (TMJ) symptoms.

Results

The prevalence of TMDs was 52.7% among included patients (138/262). The mean age of TMD patients was higher than that of the control group. No significant difference in gender distribution between the groups was observed. The most commonly reported FAI items were misaligned teeth, neck pain, and emotional tension. The Frankfort-mandibular plane angle (FMA) was larger in the TMD patients than in the control group, whereas no significant differences in other parameters were observed. Subgroup analysis based on TMD severity revealed that FMA and anterior facial height of moderate/severe TMD patients were significantly larger than those of mild or no-TMD patients. Among male patients, the anterior cranial base length was smaller, and the anterior facial height was larger in the TMD group. Among female patients, no significant differences in craniofacial morphology between the groups were observed. In juvenile patients, overjet and overbite were smaller in the TMD group. In adult patients, SNA, ANB, FMA, and gonial angle were larger in the TMD group. Within the TMD group, patients with TMJ pain or noises exhibited characteristic craniofacial features compared to patients without these symptoms.

Conclusions

Orthodontic patients with TMDs have specific craniofacial morphology, suggesting a relationship between TMDs and particular craniofacial features in orthodontic patients.

Osteoarthritis of the temporomandibular joint: A review of aetiology and pathogenesis

The aim of this review was to assess the level of evidence for genetic, biological, and functional predictive and predisposing factors for end-stage temporomandibular joint arthritis within the published literature. A comprehensive review based upon PRISMA guidelines was performed from all literature relevant to the topic. Case series and animal studies were included given the rare nature of the disease and goal of finding root-cause predictive factors. Clinical and radiographic measures were used specifically to identify factors which may have contributed to disease onset and progression. A total of 249 abstracts were identified based on search terms of major databases. After application of exclusion and inclusion criteria, 63 full-text articles were included in the analysis of this paper. There were few factors that could be reliably used to predict end-stage temporomandibular joint disease. Limited evidence is available to adequately predict end-stage temporomandibular joint osteoarthritis. No descriptive process exists that explains how and why this process can occur in younger adults. A better understanding of the aetiology and pathogenesis of TMJ-OA may lead to prevention and more effective management strategies that may reduce the need for drastic surgical intervention, particularly in young adults.

Mapping research trends of temporomandibular disorders from 2010 to 2019: A bibliometric analysis

BACKGROUND

Because of various clinical manifestations and complicated courses, temporomandibular disorders (TMDs) are difficult to treat. Current knowledge about this disease remains insufficient for precise treatment after diagnosis.

OBJECTIVES

The objective of this study is to obtain and map the overall literature trends and most cited keywords in TMDs research.

METHODS

Many indicators, including annual number of publications, country distribution, global cooperations, author contributions, original journals, cited references and keywords, were calculated and evaluated using VOSviewer v.1.6.13, which visualised many results, from the WoSCC database.

RESULTS

A total of 3121 papers on TMDs research were retrieved from 2010 to 2019. The United States produced the most articles published, but the most productive institution was the University of Sao Paulo (Brazil). Researchers and institutions conducting TMDs research have shown a very widespread and close connection. TMDs have been studied worldwide by many research centres. Professor Svensson P was the most published researcher in TMDs research and the Journal of Oral Rehabilitation published the most TMDs research articles. The top cited references mainly presented diagnostic criteria of TMDs. The most cited keywords formed clusters: (a) Anatomical factor of TMDs, (b) Symptoms of TMDs and (c) RDC/TMD, the risk factors, biopsychosocial factors and epidemiology of TMDs.

CONCLUSIONS

The research results provide very valuable data for a thorough understanding of the research status of TMDs and demonstrated international cooperation.

Evaluation of Disclusion Time in Various Angle's Malocclusions by T-Scan III System

Objective  The main purpose of this article is to evaluate the disclusion time (DT) in the lateral excursions and protrusion among subjects with Angle’s malocclusions using a T-Scan III system.

Materials and Methods  One hundred subjects with malocclusions were divided into Class I, Class II division 1, Class II division 2, and Class III ( n = 25 per group). All groups’ DT of each excursion was evaluated by a T-Scan III system.

Statistical Analysis  One-way analysis of variance, followed by a post hoc test, was used to analyze the numerical data at p < 0.05.

Results  In the respective malocclusions, means ± standard deviations in second(s) of the DT were 2.08 ± 0.65, 2.13 ± 0.74, 2.12 ± 0.72, and 3.19 ± 1.34 during left excursion; 2.15 ± 0.94, 2.58 ± 1.16, 2.37 ± 1.07, and 3.28 ± 1.25 during right excursion; and 1.88 ± 0.99, 2.08 ± 1.11, 2.07 ± 0.68, and 3.01 ± 1.53 during protrusion. When compared to Class I and Class II malocclusions, Class III showed a significantly higher mean DT of each excursion ( p < 0.05).

Conclusion  Class III had the significantly highest mean DT of each excursion and the significantly longest DT in all excursions.

The study of facial morphology in patients with vertical growth pattern (hyperdivergent) lacking or showing temporomandibular disorders symptoms

AIM

According to the large number of studies, there seems to be a significant relation between hyperdivergence growth pattern and temporomandibular disorders. However, it is not clearly scrutinized which morphological factors can contribute to the development of temporomandibular disorders. The aim of this study was to investigate the relation between some skeletal and facial morphologic features of hyperdivergent facial growth pattern patients and temporomandibular disorders.

MATERIALS AND METHODS

This case-control study was performed on a population of 50 patients including 25 patients with temporomandibular disorder and 25 non- temporomandibular disorder individuals aged between 15-30 years with hyperdivergent growth pattern (Frankfurt Mandibualr plane angle between 28 and 35 degree). Two groups of symptomatic and asymptomatic patients (case and control) were matched for age and gender. In order to evaluate the skeletal and dental variables, lateral cephalometries was taken and traced after obtaining written consent from the patients. The measured variables were A point to Nasion to B point, Frankfurt plane to Nasion to Pogonion, Nasion to A point to Pogonion, Sella to Gnathion to Frankfurt plan, Articular point to Gonion-Menton, Sella to Articular point to Gonion, Palatal plane to Mandibular plane, and Articular point to Gonion angles. The intervals of Basion to Nasion, Sella to Basion, Gonion to Menton, and amounts of Anterior facial height meas, Upper Anterior facial height ratio to Lower Anterior facial height, posterior facial height, overjet, and overbite Data were analyzed by Chi² test, t-test, and multivariate test.

RESULTS

According to the descriptive statistics, the age of the control and case groups averaged 21.12±1.99 and 21.63±1.58 years respectively. Among the people referred to the dental school, the frequency of males and females in the control and case groups were 6, 7 and 19, 18 respectively. The results of t-test and multivariate tests indicated significant differences between the two variables of overbite and mandibular length.

CONCLUSION

The present study revealed increased overbite (dental feature) and mandibular length (skeletal feature) is more likely to be associated with a higher risk of temporomandibular disorders joint disease in patients with hyperdivergent facial growth pattern.

CLINICAL SIGNIFICANCE

Treatment of the deep bite condition can be helpful in improving temporomandibular disorder.

Evaluation of vertical facial height reduction and severity of temporomandibular joint disorders using Shimbashi number and cephalometric analysis

Objective: This study was designed to evaluate the correlation between vertical dimension at occlusion (VDO) and various grades of temporomandibular disorders (TMDs) versus controls.Methods: Clinically measured Shimbashi number and radiographic cemento-enamel junction (CEJ-CEJ) measurements on 120 TMD patients and 40 controls were evaluated. Radiographic lateral cephalometric skull images of the patients were subjected to cephalometric analysis. The relationship between Shimbashi number, the cephalometric values, and its correlation with the degree of TMD were evaluated and statistically analyzed.Results: Shimbashi number and radiographic CEJ-CEJ values in the TMD patients were significantly lower than those in the controls. TMD severity appeared to increase with the increase in interincisal angle and the decrease in both Shimbashi number and radiographic CEJ-CEJ value.Conclusion: These findings indicate that radiographic evaluation of cephalograms is a reliable indicator of presence and degree of TMD, and the severity of TMD increases with the degree of reduction in VDO.

Condylar long axis and articular eminence in MRI in patients with temporomandibular disorders

OBJECTIVE

To compare morphologic findings in MRI and skeletal divergence of a group of patients with temporomandibular joint disorders (TMD) subdivided into condylar symmetric and asymmetric.

METHODS

Fifty-nine adults (26.7 years old) with TMD were retrospectively recruited. Condylar height symmetry was evaluated by orthopantomography (Habets's method) and used to divide patients into Symmetric and Asymmetric groups; skeletal divergence was assessed on lateral cephalograms. MRI was used to evaluate the condylar long axis' angle, the glenoid fossa morphology, and the degree of disc displacement.

RESULTS

Asymmetric subjects showed a hyperdivergent skeletal pattern (p = 0.036), asymmetric condylar long axis (p = 0.018), and deeper (p = 0.025) and asymmetric (p = 0.001) glenoid fossa compared to symmetric subjects.

CONCLUSION

Patients with TMD and condylar asymmetry diagnosed with orthopantomography are more likely to show hyperdivergent skull in cephalometry, condylar asymmetry of both height and major axis, and a steeper glenoid fossa in MRI.

TMD symptoms and vertical mandibular symmetry in young adult orthodontic patients in North Sumatra, Indonesia: a cross-sectional study

Background: Temporomandibular joint disorder (TMD) includes symptoms of pain and dysfunction in the muscles of mastication and the temporomandibular joint. Differences in vertical condylar height, observed in the assessment of mandibular asymmetry, is a structural alteration that represents a risk factor for TMD. The study aimed to evaluate the association between TMD symptoms and vertical mandibular symmetry in young adult orthodontic patients in North Sumatra, Indonesia.  Methods: The cross-sectional study included 18-25-year-old (mean ± SD, 21.9 ± 2.0 years) old orthodontic patients admitted to the Dental Hospital of Universitas Sumatera Utara, Medan, between June 2016 and March 2017. Vertical mandibular asymmetry was assessed from all 106 subjects using Kjellberg's technique from pre-treatment panoramic radiographs. The TMD symptoms were assessed by structural interviews using modified questionnaires based on Temporomandibular Disorder Diagnostic Index and Fonseca's Anamnestic Index. Results: Of the 106 subjects, 26 (24.5% of the total) with vertical mandibular symmetry and 39 (36.8%) with vertical mandibular asymmetry were positive for TMD symptoms. By contrast, 17 patients (16.0% of the total) with vertical condylar symmetry and 24 patients (22.6%) with vertical mandibular asymmetry were regarded negative for TMD symptoms. There was no significant difference (p=0.520) in TMD symptoms based on vertical mandibular symmetry. Conclusion: The results from this studied Sumatran population indicate that there are common TMD symptoms in young adult orthodontic patients, but there is no significant association between vertical mandibular asymmetry and TMD symptoms. Further study on the development of TMD, mandibular asymmetry and treatment planning for growing patients is suggested, using longitudinal and transitional approaches.

TMD symptoms and vertical mandibular symmetry in young adult orthodontic patients in North Sumatra, Indonesia: a cross-sectional study

Background: Temporomandibular joint disorder (TMD) includes symptoms of pain and dysfunction in the muscles of mastication and the temporomandibular joint. Differences in vertical condylar height, observed in the assessment of mandibular asymmetry, is a structural alteration that represents a risk factor for TMD. The study aimed to evaluate the association between TMD symptoms and vertical mandibular symmetry in young adult orthodontic patients in North Sumatra, Indonesia.  Methods: The cross-sectional study included 18-25-year-old (mean ± SD, 21.9 ± 2.0 years) old orthodontic patients admitted to the Dental Hospital of Universitas Sumatera Utara, Medan, between June 2016 and March 2017. Vertical mandibular asymmetry was assessed from all 106 subjects using Kjellberg's technique from pre-treatment panoramic radiographs. The TMD symptoms were assessed by structural interviews using modified questionnaires based on Temporomandibular Disorder Diagnostic Index and Fonseca's Anamnestic Index. Results: Of the 106 subjects, 26 (24.5% of the total) with vertical mandibular symmetry and 39 (36.8%) with vertical mandibular asymmetry were positive for TMD symptoms. By contrast, 17 patients (16.0% of the total) with vertical condylar symmetry and 24 patients (22.6%) with vertical mandibular asymmetry were regarded negative for TMD symptoms. There was no significant difference (p=0.520) in TMD symptoms based on vertical mandibular symmetry. Conclusion: The results from this studied Sumatran population indicate that there are common TMD symptoms in young adult orthodontic patients, but there is no significant association between vertical mandibular asymmetry and TMD symptoms. Further study on the development of TMD, mandibular asymmetry and treatment planning for growing patients is suggested, using longitudinal and transitional approaches.

Association of midline discrepancy with tempromandibular joint disorder. A systematic review

Aim

The aim is to evaluate the association between midline discrepancies and tempromandibular disorders (TMDs).

Methods

Literature search was performed by using various search engines to include human studies in English. TMDs include a wide variety of signs and symptoms such as pain in and around TMJ, jaw muscles, clicking and locking of jaws, pain during mandibular movement and restricted mandibular movements. The etiology is multifactorial, including one or several of the following factors like severe malocclusions (increased overjet, retroclination of incisors, cross bite, CR CO discrepancies etc), stress and psychological factors, structural abnormalities as possible etiology. There are controversies concerning the association between different traits of malocclusion and TMDs. The aim of the present study was to find out any association between signs and symptoms of TMDs with midline discrepancies, which represent an important trait of malocclusion.

Result

Of the seven studies evaluated in this systematic review for investigating the association between midline discrepancy and TMD, six had moderate grade (B) of evidence. Four studies of moderate grade evidence (B) showed a significant association between the presence of midline shift and TMDs, and the remaining studies (two) had non-significant association. Only one study had a strong grade of evidence (A) and interestingly it denies the presence of midline shift to be a causative factor for TMDs. So, it can be concluded that the results are inconclusive regarding the association of midline discrepancies with TMDs. Nonetheless, this requires concrete evidence which necessitates further long term research into this aspect.

Factors involved in the etiology of temporomandibular disorders - a literature review

BACKGROUND AND AIM

This review aims at presenting a current view on the most frequent factors involved in the mechanisms causing temporomandibular disorders (TMD).

METHOD

We conducted a critical review of the literature for the period January 2000 to December 2014 to identify factors related to TMD development and persistence.

RESULTS

The etiology of TMD is multidimensional: biomechanical, neuromuscular, bio-psychosocial and biological factors may contribute to the disorder. Occlusal overloading and parafunctions (bruxism) are frequently involved as biomechanical factors; increased levels of estrogen hormones are considered biological factors affecting the temporo-mandibular-joint. Among bio-psychosocial factors, stress, anxiety or depression, were frequently encountered.

CONCLUSIONS

The etiopathogenesis of this condition is poorly understood, therefore TMDs are difficult to diagnose and manage. Early and correct identification of the possible etiologic factors will enable the appropriate treatment scheme application in order to reduce or eliminate TMDs debilitating signs and symptoms.

Association of temporomandibular dysfunction with the 102T-C polymorphism in the serotonin receptor gene in Brazilian patients

INTRODUCTION

Serotonin is a key neurotransmitter in the central nervous system. It has been suggested that serotoninergic dysfunction mediates the pathophysiology of temporomandibular dysfunction (TMD). Polymorphisms in the serotonin receptor gene (HTR2A) can alter its transcription, affecting the number of receptors in the serotoninergic system, altering nociceptive pain and hyperalgesia in TMD. The aim of this study is to investigate the association of the 102T-C polymorphism in the HTR2A gene in Brazilian patients with TMD.

MATERIAL AND METHODS

This cross-sectional study examined 100 patients, of both genders, with TMD as index cases and 100 healthy volunteers as controls, also of both genders. DNA was extracted from peripheral blood leukocytes, and the site that encompassed the polymorphism in the HTR2A gene was amplified by polymerase chain reaction followed by restriction fragment length polymorphism (PCR-RFLP).

RESULTS

Our results revealed that there were significantly more females among index cases compared with the control group (p < 0.05). The CC genotype of the 102T-C polymorphism was more frequent in patients with TMD vs. controls (OR: 2.25; 95% CI: 1.13-4.46; p < 0.05).

CONCLUSIONS

The present study supports the view that the 102T-C polymorphism in the HTR2A gene is associated with TMD in this studied Brazilian population.