TMD and occlusion part I. Damned if we do? Occlusion: the interface of dentistry and orthodontics

Analysis of risk factors and interactions for pain in temporomandibular disorder: A cross-sectional study

BACKGROUND

Risk factors for temporomandibular disorder (TMD) pain remain unclear.

OBJECTIVES

This study aimed to identify risk factors for TMD pain using a biopsychosocial model and to investigate interactions between potential risk factors-oral behaviours (OBs), psychological factors and sleep quality-and their direct and indirect effects on TMD pain.

METHODS

This was a cross-sectional study of 488 patients with TMDs (422 women; 30.8 ± 9.4 years). Pain was assessed using the Numerical Rating Scale. Demographic, behavioural, psychological and biomedical data were collected through clinical examination, face-to-face interviews and questionnaires. Multiple linear regression analysis was used to identify factors associated with TMD pain. Mediation and moderation analysis were used to evaluate interactions between variables. Significant mediation ('0' not included in the 95% confidence interval (CI)) and moderation (p < .05) effects on TMD pain were identified.

RESULTS

Marital status, diagnosis subgroup, previous medication use, depression and sleep quality were significant risk factors for TMD pain (p < .05). Significant mediation effects were observed as follows: depression and sleep quality mediated the association between OBs and pain; sleep quality mediated the association between somatization, depression, anxiety and pain; and depression mediated the association between sleep quality and pain (all 95% CI did not contain '0').

CONCLUSIONS

(1) Marital status, diagnosis subgroup, previous medication use, depression and sleep quality were associated with TMD pain. (2) OBs can exacerbate pain by promoting depression and reducing sleep quality. Psychological factors and sleep quality can interact to exacerbate pain.

Exploring Temporomandibular Disorders (TMDs) and Occlusion Debate in Dentistry: Biting Into Controversy

Some conditions known as temporomandibular disorders (TMDs) affect surrounding muscles and jaw joints. In dentistry, there has been discussion and research on the connection between TMDs and occlusion, which is how the upper and lower teeth meet. Although some dental experts have proposed a direct link between TMDs and occlusion, the specifics of this relationship are still unclear and have many facets. More particularly, the research facets of "occlusion" remain one of the most contentious subjects in TMDs. This abstract aims to provide an overview of TMDs and occlusion, summarizing the key points from the literature. The etiological factors contributing to the TMDs, including occlusal, psychological, and hormonal factors, are also analyzed. The second part of the article includes the concept of malocclusion, emphasizing its significance in masticatory function and overall health. Anterior open and posterior open bites and the potential influence of occlusal factors on TMDs are elucidated.

Effects on Sleep Bruxism Activity of Three Different Oral Appliances: One Year Longitudinal Cohort Study

BACKGROUND

Different oral appliances (OAs) have been proposed to control sleep bruxism (SB) detrimental effects on the stomatognathic system.

OBJECTIVE

The aim of the study was to evaluate the effect of different OAs on SB activity and masticatory muscle activity (sMMA) measured by EMG.

METHODS

This longitudinal cohort study was conducted on 51 patients (21 M, 30 F, mean age 26,5 ± 3,5) suffering from SB diagnosed with a validated portable EMG-ECG holter and wearing different OAs: occlusal splints, functional appliance with metallic bites and clear aligners followed after 1 week, 1 month, 3 months, 6 months and 12 months from delivery. A control group of 16 non-treated SB patients (6 M, 10 F mean age 27,1 ± 1,4) was used as a reference. A multiple regression analysis was performed to estimate the differences between groups. The level of significance was set as P value <0,05.

RESULTS

Occlusal splint reduced sleep bruxism index after 1 week, 3, 6 and 12 months from delivery while functional appliance only after 12 months. Occlusal splints reduced general phasic contractions only in the first week and sleep bruxism-related phasic contractions at 1 week, 3 and 6 months after delivery with no significant reductions after 12 months. Patients wearing clear aligners showed a reduction in general tonic contractions after 6 and 12 months.

CONCLUSION

Resin and metal bites can reduce sleep bruxism index, while resin bites can reduce sleep bruxism-related phasic contractions. Clear aligners do not influence sleep bruxism index but can reduce tonic contractions.

Intraoral occlusal adjustment time and volume required for CAD/CAM crowns fabricated with different virtual mounting methods (A randomized crossover trial)

OBJECTIVE

To measure the required clinical time and volume of occlusal adjustment when the maxillary cast is positioned in a virtual articulator using one of three methods: digitization of a facebow-mounted mechanical articulator (group A), virtual Bonwill triangle (group B) or a 3D face scan (group F).

MATERIALS AND METHODS

In this randomized, triple-blind, crossover trial; 11 participants were enrolled. Every participant had one molar indicated for a single crown restoration. Three crowns were designed and milled for every participant molar totaling 33 crowns. Each of the three crowns was fabricated with the participant's casts virtually mounted utilizing a different method. An impression was taken of the crown in place before occlusal adjustment. The occlusal adjustment was then performed and timed with the three crowns in the different groups. After the occlusal adjustment, an impression of the adjusted crown was taken. The pre-adjustment and post-adjustment impressions were digitally superimposed and the volume difference was measured. The Kruskal-Wallis test was used to compare the groups.

RESULTS

Group A showed the shortest mean adjustment time (3:44.59 ± 3:39.07) followed by group F (4:30.09 ± 2:01.50) and group B (4:35.30 ± 2:32.33). The mean adjustment volume for group A was (28 ± 19.1 mm³) followed by group F (30.5 ± 18.8 mm³) and group B (40.6 ± 29.5 mm³). Different virtual mounting methods had no statistically significant effect on adjustment time (P-value = 0.538) or adjustment volume (P-value = 0.490).

CONCLUSIONS

A simplified approach in virtual articulator mounting appears to be justified in the construction of a single full-coverage prosthesis. Added labor, time and cost of more elaborate virtual mounting methods seem to be counterproductive.

Numerical investigation of the biomechanical effects of orthodontic intermaxillary elastics on the temporomandibular joint

Temporomandibular joint disorder (TMD) often coincides with malocclusion, and in some cases TMDs are reported after orthodontic treatment. Intermaxillary elastics (also known as orthodontic elastics, OE) are a common way to apply force during orthodontic treatment, and they might cause mechanical effects on the temporomandibular joint (TMJ), thereby lead to joint remodeling. It is still a controversial topic whether the adapted remodeling of the TMJ or of the alveolar bone is the main cause for the alteration of occlusion after treatment with OEs. It was the aim of this study to analyze whether variations of OEs would develop harmful effects on the healthy TMJ. A TMJ model with a masticatory system based on Hill-type muscle actuators was established. Mouth opening and closure with and without OEs were simulated, and maximum principal stresses in the disc and condylar cartilage as well as the displacement of the mandible were analyzed. We found no considerably difference in the mandibular movement without and with symmetrical OEs during mouth opening and closing. At full mouth opening, stresses in the disc and condylar cartilage of some models with OEs were much smaller than without OEs, but we did not find consistency in the results from the left and right sides of the same model (e.g. the lowest compressive stress on the left side of disc from the model with Class II OEs is much smaller than without OEs, -17.3 MPa compared with -28.2, while on the right side, there was no obvious difference). Hence, we could not conclude that OEs would develop deleterious effects on the healthy TMJ.

Evaluation of the effect of T-Scan™ as an adjunct to stabilization splint in the treatment of temporomandibular joint disorders

OBJECTIVE

To assess the effectiveness of the stabilization splint (SS) combined with the T-Scan™ III system in the treatment of temporomandibular joint disorder (TMD) with myofascial pain.

METHODS

Forty-eight enrolled patients were randomly assigned to the SS group or T-Scan™-guided SS group. Mandibular Function Impairment Questionnaire (MFIQ), Maximum Comfortable Opening (MCO), Visual Analog Scale (VAS), and Patient Health Questionnaire-9 (PHQ-9) were used as the outcome variables.

RESULTS

The occlusal contacts of patients in the SS plus T-Scan™ group showed lower Occlusal Time (OT), Disocclusion Time (DT), and Asymmetry Index of Occlusal Force (AOF) after occlusal adjustment under the guidance of the T-Scan™. Importantly, the TMD symptoms were alleviated more obviously in SS plus T-Scan™ group, with better scores for MCO and MFIQ.

CONCLUSION

T-Scan™-guided occlusal adjustment of SS can obtain better OT, DT, and AOF, which furthers improvement of the therapeutic effects on TMD with myofascial pain.

The Association between Occlusal Features and Temporomandibular Disorders in Northern Jordan: A Cross-sectional Study

Objective:

To evaluate the possible correlation between basic occlusal features and the outcomes of the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) Axis I.

Materials and Methods:

A convenient sample of Northern Jordanians was used in the study. Participants were examined in accordance with DC/TMD protocol. Nine occlusal features represented the independent variables; overjet, overbite, midline deviation, pain-free opening, maximum assisted opening, maximum unassisted opening, lateral excursions and protrusion, in addition to the opening pattern (classified as straight, corrected deviation and uncorrected deviation). DC/TMD diagnostic outcomes and their associated features represented the dependent variables, namely, pain-related TMD, Intra-articular Disorders (IAD), Degenerative Joint Disease (DJD), joint sounds (clicking and crepitus), joint locking and headache attributed to TMD. Binary logistic regression, multinomial logistic regression and Chi-square tests were used for statistical analyses.

Results:

A total of 400 participants represented the study population (mean age = 32.3±12.4 years, males=48%, females=52%). 71 subjects (18%) were diagnosed with pain-related TMD, 52 (13%) with IAD, 6 (1.5%) with DJD and 38 (10%) with headache due to TMD. Gender had a significant correlation with pain-related TMD (p= 0.014, OR= 2.16). Maximum pain free opening had a significant inverse relationship with pain related TMD (p= 0.013, OR=0.94), while midline deviation and corrected deviation mouth opening pattern had a significant correlation with IAD (p= 0.04,0.02, OR= 1.30,2.74, respectively). Overbite, midline deviation and pain free opening were significantly associated with unilateral open/close clicking (p= 0.04,0.05,0.03, OR= 0.77, 1.31, 0.94, respectively).

Conclusion:

There is a minimal clinical significance of the correlation between dental occlusion and TMD.

Orthodontic Treatment and Craniocervical Posture in Patients with Temporomandibular Disorders: An Observational Study

Orthodontic treatment acts through the application of forces and/or by stimulating and redirecting the functional forces within the craniofacial complex. Considering the interrelationship between craniomandibular and craniocervical systems, this intervention may alter craniocervical posture. Thus, our aim is to (a) compare craniocervical posture, hyoid bone position, and craniofacial morphology before, after, and also in the contention phase at least one year after the orthodontic treatment, in patients with temporomandibular disorders and (b) to verify whether the presence of condylar displacement, the skeletal class, or the facial biotype interferes with the abovementioned outcomes. To do so an observational, analytical, longitudinal, and retrospective design study was carried out. A non-probabilistic convenience sampling method was applied. The sample consisted of clinical records of patients diagnosed with temporomandibular disorders in order to compare pre-orthodontic treatment with post-orthodontic treatment (n = 42) and contention phase data (n = 26). A cephalometric analysis of several variables was performed. The p-value was set as 0.05. When the pre- and post-orthodontic treatment data were analyzed, there were statistically significant changes in variables concerning craniocervical posture (CV angle, C0-C1, and AA-PNS) and also concerning hyoid bone position (C3-Rgn). When pre- and post-orthodontic treatment and contention phase data were analyzed the variables concerning craniocervical posture (C0-C1, CVT/Ver, NSL/OPT, NSL/CVT, NSL/Ver; OPT/CVT, OPT/Ver) and facial biotype had statistically significant changes. This allowed us to conclude that in the sample studied, there were significant differences regarding hyoid bone position (pre- versus post-orthodontic treatment) and craniocervical posture (pre- versus post-orthodontic versus contention), with the craniocervical posture being prone to return to basal values. The presence of condylar displacement was found to significantly increase the H-H1 distance in the three moments of evaluation. Facial biotype was found to significantly increase the NSL/Ver angle on hypodivergent compared to hyperdivergent in the contention phase.

The neuro-pathophysiology of temporomandibular disorders-related pain: a systematic review of structural and functional MRI studies

Chronic pain surrounding the temporomandibular joints and masticatory muscles is often the primary chief complaint of patients with temporomandibular disorders (TMD) seeking treatment. Yet, the neuro-pathophysiological basis underlying it remains to be clarified. Neuroimaging techniques have provided a deeper understanding of what happens to brain structure and function in TMD patients with chronic pain. Therefore, we performed a systematic review of magnetic resonance imaging (MRI) studies investigating structural and functional brain alterations in TMD patients to further unravel the neurobiological underpinnings of TMD-related pain. Online databases (PubMed, EMBASE, and Web of Science) were searched up to August 3, 2019, as complemented by a hand search in reference lists. A total of 622 papers were initially identified after duplicates removed and 25 studies met inclusion criteria for this review. Notably, the variations of MRI techniques used and study design among included studies preclude a meta-analysis and we discussed the findings qualitatively according to the specific neural system or network the brain regions were involved in. Brain changes were found in pathways responsible for abnormal pain perception, including the classic trigemino-thalamo-cortical system and the lateral and medial pain systems. Dysfunction and maladaptive changes were also identified in the default mode network, the top-down antinociceptive periaqueductal gray-raphe magnus pathway, as well as the motor system. TMD patients displayed altered brain activations in response to both innocuous and painful stimuli compared with healthy controls. Additionally, evidence indicates that splint therapy can alleviate TMD-related symptoms by inducing functional brain changes. In summary, MRI research provides important novel insights into the altered neural manifestations underlying chronic pain in TMD.

Application of a Systematic Protocol in the Treatment of TMDs With Occlusal Appliances: Effectiveness and Efficiency in a Longitudinal Retrospective Study With Medium-Term Follow-Up

Objectives:

This study aimed to assess effectiveness, efficiency, and feasibility of a systematic protocol for the choice and management of occlusal splints (OA) in the treatment of temporomandibular disorders (TMDs).

Materials and Methods:

A longitudinal retrospective study was conducted. Two different samples, G1 + G2 (337 patients), between January 2011 and January 2014, were selected according to inclusion and exclusion criteria. G1 was composed of patients visited at Policlinico Umberto I, Head-Neck Department, Sapienza University of Rome, Italy, and patients in G2 visited at a private structure in Rome. Pain records and functionality were compared before (T0) and at the end of therapy (T1). A follow-up group, composed of 100 patients randomly selected among those who completed treatment for at least 1 year (T2), was analyzed and symptomatology records were compared. Descriptive statistical analysis was performed.

Results:

In the entire sample, joint and muscular pain, joint noises and mandibular functionality, headache, and neck pain improved from T0 to T2. The average time for articular and muscular recovery was 6.4 months. Comparing treatment outcomes, there were not statistically significant differences between the two groups.

Conclusions:

Treatment outcomes using this setting of protocol showed a positive trend also in the medium term. The use of a systematic protocol seems to reduce operator-dependent factors.

[Relationship between masticatory muscles activity and motor cortex activation during treatment of patients with distal malocclusion]

The processes of neuroplasticity of the motor cortex of the brain were evaluated in the treatment of 20 (12 women and 8 men) patients aged 18-35 years (22.5±1.5 years) with distal occlusion using functional magnetic resonance imaging (fMRI), as well as comparison of surface myography (EMG) data to assess the adaptive capabilities of the tooth-jaw system and the central nervous system against the background of orthodontic correction. Correction of distal occlusion was carried out using ceramic braces 'Damon' (f. 'Ormco', USA). The advancement of the lower jaw forward with bite enhancement was carried out using the Twin force device ('Ortho Orgonizers GmbH', Germany). The study was conducted in five stages: 1) before orthodontic correction; 2) before installing the Twin force device; 3) after anterior displacement of the lower jaw and bite enhancement on the Twin force device; 4) after removing the brackets; 5) 1.5 months after the treatment. FMRI proved to be a useful tool for orthodontic treatment efficacy assessment and neuromuscular adaptation of maxillofacial structures to changing functional status.

Síndrome da disfunção da articulação temporomandibular e o estresse presente no trabalho policial: revisão integrativa

Resumo O estudo objetivou investigar se o estresse presente nas atividades dos trabalhadores da polícia brasileira pode ter relação com o desenvolvimento da síndrome da disfunção da articulação temporomandibular (DTM), uma doença comumente associada a condições estressantes. Realizou-se uma revisão integrativa de literatura sobre os temas estresse, DTM e atividade policial. Foram identificadas diversas fontes estressoras no trabalho do policial brasileiro e observou-se que o estresse influencia no desenvolvimento, agravamento e tratamento dos sintomas da síndrome. Há comprometimento na qualidade de vida e saúde dos portadores de DTM. O fato de estudos terem mostrado associação entre estresse e atividades desenvolvidas pelos policiais brasileiros, bem como relação entre estresse e DTM, levou à suposição de que é possível haver relação entre o estresse gerado pelo trabalho executado por policiais e o risco de desenvolvimento da DTM por essa classe de trabalhadores. É recomendado que o indivíduo portador da síndrome seja avaliado como um todo antes da execução do tratamento e que esse tratamento seja multidisciplinar. A literatura sobre DTM em policiais ainda é incipiente, motivo pelo qual sugere-se o desenvolvimento de estudos sobre o tema.

Reduced corticostriatal functional connectivity in temporomandibular disorders

Although temporomandibular disorders (TMD) have been associated with abnormal gray matter volumes in cortical areas and in the striatum, the corticostriatal functional connectivity (FC) of patients with TMD has not been studied. Here, we studied 30 patients with TMD and 20 healthy controls that underwent clinical evaluations, including Helkimo indices, pain assessments, and resting-state functional magnetic resonance imaging scans. The FCs of the striatal regions with the other brain areas were examined with a seed-based approach. As seeds, we used the dorsal caudate, ventral caudate/nucleus accumbens, dorsal caudal putamen, and ventral rostral putamen regions. Voxel-wise comparisons with controls revealed that the patients with TMD exhibited reduced FCs in the ventral corticostriatal circuitry, between the ventral striatum and ventral frontal cortices, including the anterior cingulate cortex and anterior insula; in the dorsal corticostriatal circuitry, between the dorsal striatum and the dorsal cortices, including the precentral gyrus and supramarginal gyrus; and also within the striatum. Additionally, we explored correlations between the reduced corticostriatal FCs and clinical measurements. These results directly supported the hypothesis that TMD is associated with reduced FCs in brain corticostriatal networks and that these reduced FCs may underlie the deficits in motor control, pain processing, and cognition in TMD. Our findings may contribute to the understanding of the etiologies and pathologies of TMD.

Temporomandibular Disorders: "Occlusion" Matters!

By analogy with the journal's title Pain Research and Management, this review describes TMD Research and Management. More specific are the (1) research aspects of “occlusion,” still one of the most controversial topics in TMD, and (2) as much as possible evidence-based management aspects of “TMD” for the dental practitioner. Research. The disorders temporomandibular dysfunction and the synonymous craniomandibular dysfunction are still being discussed intensely in the literature. Traditionally, attention is mostly devoted to occlusion and its relationship with these disorders. The conclusions reached are often contradictory. Considering the definitions of temporomandibular and craniomandibular dysfunctions/disorders and “occlusion,” a possible explanation for this controversy can be found in the subsequent methodological problems of the studies. Based on a Medline search of these terms over the past 40 years related to contemporary terms such as “Evidence Based Dentistry” and “Pyramid of Evidence,” these methodological aspects are examined, resulting in recommendations for future research and TMD-occlusal therapy. Management. To assist the dental practitioner in his/her daily routine to meet the modern standards of best practice, 7 guidelines are formulated that are explained and accompanied with clinical examples for an evidence-based treatment of patients with this disorder in general dental practices.

Temporomandibular disorders in growing patients after treatment of class II and III malocclusion with orthopaedic appliances: a systematic review

OBJECTIVE

To determine if the use of orthopaedic appliances in growing patients applied to correct Class II and III malocclusion is related to the development of temporomandibular disorders (TMD).

MATERIAL AND METHODS

A systematic review was conducted between 1960 and July 2017, based on electronic databases: PubMed, Cochrane Library, Embase, Medline, Scopus, EBSCOhost, Scielo, Lilacs and Bireme. Controlled clinical trials (CCTs) and randomized controlled trials (RCTs) were identified. The articles were selected and analyzed by two authors independently. The quality of the evidence was determined according to the guidelines of the Cochrane Risk Bias Assessment Tool and the Cochrane Quality Study Guide.

RESULTS

Seven articles were included, four CCTs and three RCTs. The studies were grouped according to malocclusion treatment in (a) class II appliances (n = 4) and (b) class III appliances (n = 3). The quality of evidence was low due to the high risk of bias, independent of the association reported. All studies concluded that the use of orthopaedic appliances would not contribute to the development of TMD.

CONCLUSIONS

The quality of evidence available is insufficient to establish definitive conclusions, since the studies were very heterogeneous and presented a high risk of bias. However, it is suggested that the use of orthopaedic appliances to correct class II and III malocclusion in growing patients would not be considered as a risk factor for the development of TMD. High-quality RCTs are required to draw any definitive conclusions.

Evaluation of signs, symptoms, and occlusal factors among patients with temporomandibular disorders according to Helkimo index

Objective: This study sought to assess the clinical signs and subjective symptoms of TMD, including the occlusal condition. Methods: Recruited individuals included 123 patients (58 men, 65 women) aged 15 to 65 years (mean 38.6 years) who had been referred to the TMD department. Helkimo dysfunction, occlusal, and anamnestic indices were used to assess signs of TMD, occlusal condition, and symptoms, respectively. Relationships of occlusal factors with signs and symptoms of TMD were evaluated by Spearman's correlation test. Associations of TMD with sex and age distributions were assessed by Mann-Whitney and Spearman's test, respectively. Results: The prevalence of signs and symptoms was as high as 75%. Occlusal factors had significant associations with signs and symptoms of TMD. Conclusion: Prevalence of TMD in the study population was high, without preference for age or sex. Occlusal factors may play a role in the etiology of TMD.

Potential risks of orthodontic therapy: a critical review and conceptual framework

This review examines some of the potential risks of orthodontic therapy along with their evidence base. The risks of orthodontic treatment include periodontal damage, pain, root resorption, tooth devitalization, temporomandibular disorder, caries, speech problems and enamel damage. These risks can be understood to arise from a synergy between treatment and patient factors. In general terms, treatment factors that can influence risk include appliance type, force vectors and duration of treatment whilst relevant patient factors are both biological and behavioural. Hence, the natural variation between orthodontic treatment plans and patients gives rise to variations in risk. A good understanding of these risks is required for clinicians to obtain informed consent before starting treatment as well as to reduce the potential for harm during treatment. After considering each of these risks, a conceptual framework is presented to help clinicians better understand how orthodontic risks arise and may therefore be mitigated.

Adults seeking orthodontic treatment: expectations, periodontal and TMD issues

The growth in adult orthodontics presents new challenges to both the general dental practitioner and the orthodontist. Although many of the main objectives of orthodontic treatment are similar for adults, young adults and children, adult patients frequently bring significant challenges in several areas not often seen in the younger patient group. In areas such as planning realistic treatment outcomes, it is paramount that the patient's expectations are identified, respected and managed where appropriate. The adult patient's dental health often dictates deviation from the ideal treatment plan and periodontal problems are a common example. Based on current evidence, this paper presents an overview of some of the difficulties in the management of these issues, as well as highlighting developments with regard to pain conditions and their relevance to orthodontic treatment and its effects on temporomandibular joint disorders (TMD) management.

Influence of orthodontic treatment on temporomandibular disorders. A systematic review

Objectives

The aim of this literature systematic review was to evaluate the possible association between malocclusions, orthodontic treatment and development of temporomandibular disorders. Material and Methods: A search was carried out on PubMed-Medline database from January 2000 to August 2013 using the keywords “orthodontics and temporomandibular disorders”, “orthodontics and facial pain” and “malocclusion and temporomandibular disorders”. Human studies included in the study were those assessing signs and symptoms of temporomandibular disorders in relation to orthodontic treatment.

Material and Methods

A search was carried out on PubMed-Medline database from January 2000 to August 2013 using the keywords “orthodontics and temporomandibular disorders”, “orthodontics and facial pain” and “malocclusion and temporomandibular disorders”. Human studies included in the study were those assessing signs and symptoms of temporomandibular disorders in relation to orthodontic treatment.

Results

The search strategy resulted in 61 articles. After selection according to the inclusion/exclusion criteria 9 articles qualified for the final analysis. The articles which linked orthodontics and development of temporomandibular disorders showed very discrepant results. Some indicated that orthodontic treatment could improve signs and symptoms of temporomandibular disorders, but none of them obtained statistically significant differences.

Conclusions

According to the authors examined, there is no evidence for a cause-effect relationship between orthodontic treatment and temporomandibular disorders, or that such treatment might improve or prevent them. More longitudinal studies are needed to verify any possible interrelationship.

Key words:Malocclusion and temporomandibular disorders, orthodontics and facial pain, orthodontics and temporomandibular disorders, temporomandibular disorders, temporomandibular dysfunction.

Muscle fatigue in the temporal and masseter muscles in patients with temporomandibular dysfunction

The aim of this study is to evaluate muscle fatigue in the temporal and masseter muscles in patients with temporomandibular dysfunction (TMD). Two hundred volunteers aged 19.3 to 27.8 years (mean 21.50, SD 0.97) participated in this study. Electromyographical (EMG) recordings were performed using a DAB-Bluetooth Instrument (Zebris Medical GmbH, Germany). Muscle fatigue was evaluated on the basis of a maximum effort test. The test was performed during a 10-second maximum isometric contraction (MVC) of the jaws. An analysis of changes in the mean power frequency of the two pairs of temporal and masseter muscles (MPF%) revealed significant differences in the groups of patients with varying degrees of temporomandibular disorders according to Di (P < 0.0000). The study showed an increase in the muscle fatigue of the temporal and masseter muscles correlated with the intensity of temporomandibular dysfunction symptoms in patients. The use of surface electromyography in assessing muscle fatigue is an excellent diagnostic tool for identifying patients with temporomandibular dysfunction.

The impact of malocclusion on the quality of life among children and adolescents: a systematic review of quantitative studies

BACKGROUND

Among child and adolescent patients, persistent but untreated malocclusions may or may not have psychological and social impacts on the individual's quality of life.

OBJECTIVES

To gain knowledge of malocclusions and its impact on oral health-related quality of life (OHRQOL), we conducted a systematic review of quantitative studies for evidence regarding the influence of malocclusions on OHRQOL in children and adolescents.

MATERIALS AND METHODS

Five databases (MEDLINE via PubMed, EMBASE, Psychinfo, CINAHL, and the Cochrane Library) were searched using specified indexing terms. The following inclusion criteria were used: child or adolescent study population; healthy study participants without syndromes such as cleft lip/palate or severe illness; no previous or ongoing orthodontic treatment among participants; a focus on malocclusions and quality of life; controlled or subgrouped according to malocclusions/no malocclusions; malocclusions and/or orthodontic treatment need assessed by professionals using standardized measures; self-assessed OHRQOL estimated using validated questionnaire instruments; full-text articles written in English or Scandinavian languages. Quality of evidence was classified according to GRADE guidelines as high, moderate, or low.

RESULTS

The search produced 1142 titles and abstracts. Based on pre-established criteria, the full-text versions of 70 articles were obtained, 22 of which satisfied the inclusion criteria. After data extraction and interpretation, six publications were deemed eligible for full inclusion. All six were of cross-sectional design, and the quality of evidence was high in four cases and moderate in the remaining two. The four studies with a high level of quality reported that anterior malocclusion had a negative impact on OHRQOL, and the two with a moderate level of quality reported that increased orthodontic treatment need had a negative impact on OHRQOL.

CONCLUSION

The scientific evidence was considered strong since four studies with high level of quality reported that malocclusions have negative effects on OHRQOL, predominantly in the dimensions of emotional and social wellbeing.

Spontaneous neural activity alterations in temporomandibular disorders: a cross-sectional and longitudinal resting-state functional magnetic resonance imaging study

The involvement of the central nervous system in the pathophysiology of temporomandibular disorders (TMD) has been noticed. TMD patients have been shown dysfunction of motor performance and reduced cognitive ability in neuropsychological tests. The aim of this study is to explore the spontaneous neural activity in TMD patients with centric relation (CR)-maximum intercuspation (MI) discrepancy before and after stabilization splint treatment. Twenty-three patients and twenty controls underwent clinical evaluations, including CR-MI discrepancy, Helkimo indices and chronic pain, and resting state functional magnetic resonance imaging scans at baseline. Eleven patients repeated the evaluations and scanning after the initial wearing (T1) and 3months of wearing (T2) of the stabilization splint. The fractional amplitude of low-frequency fluctuation (fALFF) was calculated to compare the neural functions. At baseline, the patients showed decreased fALFF in the left precentral gyrus, supplementary motor area, middle frontal gyrus and right orbitofrontal cortex compared with the controls (P<0.05, AlphaSim corrected). Negative correlations were found between the fALFF in the left precentral gyrus and vertical CR-MI discrepancy of bilateral temporomandibular joints of patients (P<0.05, two-tailed). At T2, the symptoms and signs of the patients were improved, and a stable condylar position on the CR was recovered, with increased fALFF in the left precentral gyrus and left posterior insula compared with pretreatment. The fALFF decrease in the patients before treatment was no longer evident at T2 compared with the controls. The results suggested that TMD patients with CR-MI discrepancy showed significantly decreased brain activity in their frontal cortexes. The stabilization splint elicited functional recovery in these cortical areas. These findings provided insight into the cortical neuroplastic processes underlying TMD with CR-MI discrepancy and the therapeutic mechanisms of stabilization splint.

Impact of malocclusion on oral health related quality of life in young people

Background

The objectives for this study were to assess Oral Health Related Quality of Life (OHRQoL) in young people aged 15–25 who sought orthodontic treatment, and to measure the association between orthodontic treatment need (using the IOTN), sex, age and education level, and oral health related quality of life (OHRQoL).

Methods

Survey of a consecutive series of 323 young adults aged 15 to 25 years, attending orthodontic clinics at the Faculty of Dentistry, Universiti Teknologi MARA. Participants completed the Oral Health Impact Profile-14 (OHIP-14) and had a clinical examination including the Index of Orthodontic Treatment Need- Dental Health Component (IOTN-DHC). Data analyses included descriptive statistics, One-way ANOVA and bivariate and multivariate regression models.

Results

The mean overall score (± SD) for OHIP-14 in young people aged 15–25 was 22.6 ± 12.5. The psychological discomfort domain was the domain where highest impact was recorded with a mean (± SD) of 4.0 ± 1.9. The regression analyses showed a significant association of IOTN-DHC with overall OHIP-14 score (p < 0.05). Although females reported a slightly higher impact than males, this was not significant in both bivariate and multivariate analyses. Age group had a significant negative association with overall OHIP-14 score (p < 0.05). The 15–18 year old group showed the highest impact on their quality of life due to malocclusion. Participants with a university education report a significantly higher impact on OHRQoL as compared to participants with only secondary education.

Conclusion

Malocclusion has a significant negative impact on OHRQoL and its domains. This is greatest for the psychological discomfort domain. Younger people and those with a university education report higher levels of impact. There was no reported difference in impact between male and females.

A review of the oral health-related evidence that supports the orthodontic treatment need indices

BACKGROUND AND OBJECTIVES

To date, there is no evidence-based method of quantification for malocclusion. Consequently, how deviant occlusal traits should be scored and weighted relative to one another is a matter of serious debate. Orthodontic Treatment Need Indices (OTNI) use the subjective opinion of the experts, as their foundation, to define the pathological boundaries (cut-offs) of occlusal traits. This paper reviews the evidence relating malocclusions or deviated occlusal traits to oral health problems, and investigates if this evidence supports the cut-off points and the rationale used for OTNI.

MATERIALS AND METHODS

The relevant cited studies and reviews from the MEDLINE, Web of Science, Scopus, Cochrane databases, and scientific textbooks were used. The citation rate was confirmed by using the Google Scholar.

RESULTS

So far, the evidence for harmful effects of deviated occlusal traits on oral health is either lacking or exists as cross-sectional (mostly) and longitudinal (a few and primarily short-term) studies. When an association was reported between a deviated occlusal trait and an oral health problem, either the strength of that association was weak, or due to methodological issues, findings were not conclusive. Consequently, establishing a cause and effect relationship is difficult. Further, commonly used OTNI do not record a full spectrum of occlusal traits, and relating their ranking or scoring systems to the available evidence is difficult. Therefore, there is little evidence to suggest that individuals with a high need (high score), as measured by OTNI, will necessarily put at risk their oral health if they turn down orthodontic therapy.

CONCLUSION

OTNI have a role in the epidemiology and can be used for resource planning, but their predictive value to detect the future objective functional deficits or oral health problems is questionable. OTNI will need revalidation over time with emerging research findings.

Twenty-year cohort study of health gain from orthodontic treatment: temporomandibular disorders

INTRODUCTION

Temporomandibular disorder (TMD) is a common condition. Studies of TMD in relation to orthodontic treatment did not show an association, but longitudinal studies from adolescence to adulthood are lacking. The aim of this study was to investigate the relationship between orthodontic treatment and TMD with a longitudinal study design.

METHODS

This prospective cohort study was conducted in South Wales, United Kingdom. The baseline investigation was carried out in 1981 and involved children aged 11 to 12 years (n = 1018). Follow-up investigations were done in 1984 (n = 792), 1989 (n = 456), and 2000 (n = 337).

RESULTS

Overall TMD prevalence increased from the baseline (3.2%) to age 19 to 20 (17.6%) and decreased by age 30 to 31 (9.9%). TMD prevalence was higher in females at all follow-up points, except the baseline. Overall, incidences of TMD were 11.9%, 11.5%, and 6.0% at the first, second, and last follow-ups, respectively. Females were more likely to develop TMD than males (hazard ratio [HR], 2.1; 95% CI, 1.3 and 3.3), and those with high self-esteem were less likely to develop TMD (HR, 0.6; 95% CI, 0.4 and 0.8). There was no association between orthodontic treatment and new TMD onset. The incidences of persistent TMD were 20.0%, 34.9%, and 28.0% at the first, second, and last follow-ups, respectively. Females were more likely to have persistent TMD than males (HR, 2.5; 95% CI, 1.0 and 6.1). There was no association between orthodontic treatment and persistent TMD. The only significant predictors of TMD in adults aged 30 to 31 were female sex (odd ratio, 3.0; 95% CI, 1.1 and 8.2) and TMD in adolescence (odds ratio, 4.5; 95% CI, 2.0 and 10.0).

CONCLUSIONS

Orthodontic treatment neither causes nor prevents TMD. Female sex and TMD in adolescence were the only predictors of TMD in young adulthood.