Association between craniomandibular disorders and occlusal interferences in children

Temporomandibular Disorders: Implications in Restorative Dentistry and Orthodontics

Over the past several decades, the science of restorative/reconstructive dentistry and orthodontics has evolved tremendously, following sound principles passed down from robust literature and scientific rationale. These principles have been solid and instrumental in enhancing dentistry, from a single tooth restoration to complex full-mouth rehabilitations. However, it must be noted that some of the principles and philosophies followed over these decades have been questioned based on the advances in science, technology, and evidence-based medicine. The scenario became complex when clinicians were faced with the question of guidance for optimum joint and muscle health as related to restorative dentistry and orthodontics.

Effect of occlusal equilibration on masticatory muscle activity in females with sleep bruxism: a double-blind randomised controlled trial

Masticatory muscle activity during sleep has been considered independent of variations in the structural characteristics of the dental occlusion. However, scientific evidence contradicting an occlusal causal role is missing. The purpose of this study was to test the null hypothesis that sleep bruxism (SB) is independent of the presence of occlusal interferences. A total of 17 healthy female subjects (mean [SD] age 24.9 [4.1] years) presenting with SB, and randomly divided into two groups, were evaluated after receiving either elimination of occlusal interferences (Test group) or elimination of sharp margins without change in occlusal contacts (Control group). Audio-video polysomnography (PSG) recordings were undertaken before and after treatment (mean [SD] duration 14.4 [3.8] months). Two subjects in each group (< 2 rhythmic masticatory muscle activity [RMMA]/h) were excluded for statistical analysis. During the total sleep time (TST), the Test group exhibited a higher reduction in frequency of episodes per hour than the Control group (p < 0.05). The reduction in duration of episodes was also higher in the Test group during the TST. The Test group presented an increase in sleep stage N3 (p < 0.05) at the final PSG when compared with the initial PSG, and a higher percentage of N3 (p < 0.05) at the final PSG when compared to the Control group. Elimination of occlusal interferences resulted in a significant reduction of masseter and temporal muscle activity during sleep in females presenting with SB. Based on these results, the null hypothesis is rejected. The hypothesis of occlusal interferences as a risk factor for SB is still patent.

Temporomandibular pain

Temporomandibular joint pain has various medical and dental etiological factors. The etiology of the temporomandibular joint pain is enigmatic, no single etiological factor is regarded as the cause. Its distribution is also not confined to a single area. This article presents the basic etiologic factors, its epidemiology, distribution of pain, classification of patients and the psychosocial behavior of patients suffering with temporomandibular pain. As overwhelming majority of medical and dental conditions/issues related to etiology of temporomandibular pain in patients have traditionally been presented and interpreted from the clinician's point of view.

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.

Muscular Activity Disorders in Relation to Intentional Occlusal Interferences

The electromyographic activity (EMG) of the anterior temporal (AT), masseter (M), trapezius (T) muscles and anterior aspect of the digastric (D) was measured in 50 subjects, during six seconds of maximum contraction, bilaterally with and without unilateral premature contacts and individually for each tooth. Special occlusal interferences were designed to assess muscular activity. Muscular activity was measured simultaneously by placing premature contacts on each tooth, under T-Scan monitoring. Premature contacts reduced EMG activity during maximum contraction of the AT, D and M muscles, the highest disruption is in the AT muscle, at the level of upper right 2nd molar, with a 56% reduction in activity. Conversely, there was an increase of activity of the T muscle in all teeth when placing artificial occlusal premature contacts, with the highest difference in the upper right 1st bicuspid. Therefore, occlusal interferences can cause neuromuscular disruptions, thus inducing important muscular discrepancy. Both the EMG and T-Scan monitoring can be considered suitable methods to use in daily dental practice to identify premature contacts and to measure EMG activity.

Occlusal stability

Occlusion is the foundation for clinical success in fixed, removable, and implant prosthodontic treatment. Understanding those principles is critical when restoring a patient's occlusion. Many philosophies, devices, and theories of occlusion have evolved based on anecdotal clinical observations and applied geometric perceptions. The literature has reported these classic and contemporary occlusal concepts. As evidence-based dentistry emerged, it championed scrutiny of previously held beliefs, resulting in the abandonment of many pragmatic, yet beneficial occlusal procedures. The impetus toward scientific discovery, whereby factual information might be universally applied in dental education and clinical practice, has renewed interest in occlusal studies.

Temporomandibular disorders: A position paper of the International College of Cranio-Mandibular Orthopedics (ICCMO)

PURPOSE

Two principal schools of thought regarding the etiology and optimal treatment of temporomandibular disorders exist; one physical/functional, the other biopsychosocial. This position paper establishes the scientific basis for the physical/functional. THE ICCMO POSITION: Temporomandibular disorders (TMD) comprise a group of musculoskeletal disorders, affecting alterations in the structure and/or function of the temporomandibular joints (TMJ), masticatory muscles, dentition and supporting structures. The initial TMD diagnosis is based on history, clinical examination and imaging, if indicated. Diagnosis is greatly enhanced with physiologic measurement devices, providing objective measurements of the functional status of the masticatory system: TMJs, muscles and dental occlusion. The American Alliance of TMD organizations represent thousands of clinicians involved in the treatment of TMD. The ten basic principles of the Alliance include the following statement: Dental occlusion may have a significant role in TMD; as a cause, precipitant and/or perpetuating factor. Therefore, it can be stated that the overwhelming majority of dentists treating TMD believe dental occlusion plays a major role in predisposition, precipitation and perpetuation. While our membership believes that occlusal treatments most frequently resolve TMD, it is recognized that TMD can be multi faceted and may exist with co-morbid physical or emotional factors that may require therapy by appropriate providers. The International College of Cranio-Mandibular Orthopedics (ICCMO), composed of academic and clinical dentists, believes that TMD has a primary physical/functional basis. Initial conservative and reversible TMD treatment employing a therapeutic neuromuscular orthosis that incorporates relaxed, healthy masticatory muscle function and a stable occlusion is most often successful. This is accomplished using objective measurement technologies and ultra low frequency transcutaneous electrical neural stimulation (TENS).

CONCLUSION

Extensive literature substantiates the scientific validity of the physical/functional basis of TMD, efficacy of measurement devices and TENS and their use as aids in diagnosis and in establishing a therapeutic neuromuscular dental occlusion.

CLINICAL IMPLICATIONS

A scientifically valid basis for TMD diagnosis and treatment is presented aiding in therapy.

Experimental occlusal interference induces long-term masticatory muscle hyperalgesia in rats

Temporomandibular joint or related masticatory muscle pain represents the most common chronic orofacial pain condition. Patients frequently report this kind of pain after dental alterations in occlusion. However, lack of understanding of the mechanisms of occlusion-related temporomandibular joint and muscle pain prevents treating this problem successfully. To explore the relationship between improper occlusion (occlusal interference) and masticatory muscle pain, we created an occlusal interference animal model by directly bonding a crown to a maxillary molar to raise the masticating surface of the tooth in rats. We raised the occlusal surface to three different heights (0.2, 0.4, and 0.6mm), and for one month we quantitatively measured mechanical nociceptive thresholds of the temporal and masseter muscles on both sides. Results showed a stimulus-response relationship between the height of occlusal interference and muscle hyperalgesia. Removal of the crown 6 days after occlusal interference showed that the removal at this time could not terminate the 1 month duration of mechanical hyperalgesia in the masticatory muscles. Lastly, we systemically administered NMDA antagonist MK801 (0.2, 0.1, and 0.05 mg/kg) to the treated rats and found that MK801 dose dependently attenuated the occlusal interference-induced hyperalgesia. These findings suggest that occlusal interference is directly related to masticatory muscle pain, and that central sensitization mechanisms are involved in the maintenance of the occlusal interference-induced mechanical hyperalgesia.

The electromyographic activity of masseter and anterior temporalis during orofacial symptoms induced by experimental occlusal highspot

The aim of the present study was to investigate the short-term impact of an occlusal highspot on the occurrence of orofacial symptoms by collecting self-evaluation and using electromyography (EMG) evaluation. A rigid unilateral intercuspal occlusal highspot (A cast onlay of 0.5 mm) was placed on the right lower first molar of six adult volunteers (three males, three females), and remained for 6 days. Continuously all the induced orofacial symptoms were collected and the subjects scored the orofacial pain on a 10-cm visual analogue scale (VAS) during the placement of onlay. The surface EMG was recorded before the placement of onlay, during (on the 3rd and 6th day) and after the onlay was removed. Then the contractile symmetry of bilateral masseter (MAL, MAR) and anterior temporalis (TAL, TAR) was measured by using an asymmetry index. On the 3rd day of the placement of the occlusal highspot, all subjects complained of headache in right temporal region (mean VAS +/- s.d.=3.7+/-0.5); the activity of TAR at rest position of mandible increased significantly (P=0.027). In addition, on the 3rd and 6th day with the highspot the EMG activity of the tested muscles during maximal voluntary contraction (MVC) was significantly reduced; the asymmetry index of bilateral anterior temporalis during MVC was increased significantly (P(3rd)=0.028; P(6th)=0.046). A unilateral occlusal highspot may make the ipsilateral anterior temporalis become tenser at rest position. Furthermore, the activity of bilateral anterior temporalis becomes more unsymmetrical during MVC although there are inter-individual differences between subjects. The changes in muscular activity may have some relationship with the occurrence of tension-type headache in temporal region.

Occlusal Risk Factors for Temporomandibular Disorders

OBJECTIVE

To determine the role of occlusal variables (overbite; overjet; number of anterior and posterior teeth; bilateral canine guidance on lateral and protrusive movements; anterior centric slide; Angle Classes I, II, and III malocclusion) as risk indicators for the development of temporomandibular disorders (TMDs).

MATERIALS AND METHODS

Seventy-two TMD patients with myofascial pain, with or without limited opening and arthralgia, as well as 30 age- and gender-matched pain-free concurrent controls were included. The association (critical odds ratio [OR] = 2.0) between the significant occlusal variables and TMD was calculated. Confounders were controlled in the inclusion-exclusion criteria as well as in the analysis stage (unconditional logistic regression) by variation in the OR (15%).

RESULTS

Angle Class II malocclusion (crude OR = 8.0, confidence interval [CI] = 2.2 to 29.3) and the absence of bilateral canine guidance on lateral excursion (crude OR = 3.9, CI = 1.6 to 9.7) were statistically more common in patients than in controls. Spontaneous pain as well as pain on palpation (Class II or higher) were also statistically worse in TMD patients. Significant confounders (ie, employment, age, cigarette and alcohol consumption) acted as effect modifiers not changing the critical OR (adjusted OR Angle Class II and bilateral canine guidance = 8.3 to 12.4 and 2.2 to 4.1, respectively).

CONCLUSIONS

Absence of bilateral canine guidance on lateral excursion and particularly Angle Class II malocclusion were considered important risk indicators for the development of TMD in this investigation, even when some sociodemographic factors were considered as effect modifiers.

TMD and occlusion part II. Damned if we don't? Functional occlusal problems: TMD epidemiology in a wider context

OBJECTIVES

To review studies investigating how functional occlusion may relate to TMD and how bruxism may relate to TMD; to review the epidemiology of TMD and relate this to the context of clinical occlusal studies and other aetiological factors. Deficiencies in study design are highlighted and suggestions made to improve future study designs in order to provide an evidence-base for clinical practice.

DESIGN

Review article.

METHODS

Electronic databases (MEDLINE and the Cochrane Database of Systematic Reviews) were used to select relevant and frequently cited studies (mean: 40 citations). Citation rate was confirmed using the Web of Science. Study designs are reviewed and weaknesses and implications discussed.

RESULTS

Evidence is lacking to suggest functional occlusal factors cause TMD. Investigation of other aetiological factors has been relatively neglected.

CONCLUSIONS

Neither static nor dynamic occlusal factors (including orthodontics) can be said to 'cause' TMD. However, other potential aetiological factors exist which would benefit from more investigation. This, together with improved study designs, would help provide a stronger evidence-base for clinical practice in the future.

No effect of experimental occlusal interferences on pressure pain thresholds of the masseter and temporalis muscles in healthy women

It has been suggested that occlusal interferences may lead to pain and tenderness of the masticatory muscles. Tender jaw muscles are more sensitive to pressure pain, as assessed by means of pressure algometry. We tested the effects of occlusal interferences on the pressure pain threshold of the jaw muscles by means of a double-blind randomized crossover experiment carried out on 11 young healthy females. Golden strips were glued either to an occlusal contact area (active interference) or to the vestibular surface of the same tooth (dummy interference) and left for 8 d each. Pressure pain thresholds of the masseter and anterior temporalis muscles were assessed under interference-free, dummy-interference and active-interference conditions. The results indicated that the application of an active occlusal interference, as used in this study, did not influence significantly the pressure pain thresholds of these muscles in healthy individuals.

Effect of occlusal interference on habitual activity of human masseter

It has been suggested that occlusal interference may increase habitual activity in the jaw muscles and may lead to temporomandibular disorders (TMD). We tested these hypotheses by means of a double-blind randomized crossover experiment carried out on 11 young healthy females. Strips of gold foil were glued either on a selected occlusal contact area (active interference) or on the vestibular surface of the same tooth (dummy interference) and left for 8 days each. Electromyographic masseter activity was recorded in the natural environment by portable recorders under interference-free, dummy-interference, and active-interference conditions. The active occlusal interference caused a significant reduction in the number of activity periods per hour and in their mean amplitude. The EMG activity did not change significantly during the dummy-interference condition. None of the subjects developed signs and/or symptoms of TMD throughout the whole study, and most of them adapted fairly well to the occlusal disturbance.

Quantification of the relative risk of multiple occlusal variables for muscle disorders of the stomatognathic system

STATEMENT OF PROBLEM

There is no consensus on the association between occlusion and temporomandibular disorders (TMD).

PURPOSE

The purpose of this study was to quantify the relative risk of multiple occlusal variables for muscle disorders of the stomatognathic system.

MATERIAL AND METHODS

Eight occlusal features: retruded contact position (RCP) to maximum intercuspation (MI) slide length, vertical overlap, horizontal overlap, unilateral posterior reverse articulation, anterior open occlusal relationship, incisor dental midline discrepancy, mediotrusive interferences, and laterotrusive interferences, were clinically assessed by the same trained operator. The sample consisted of 81 women with a Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) axis I diagnosis of muscle disorder, for example myofascial pain, with or without limited opening, and 48 healthy women (control group). A stepwise multiple logistic regression was used to identify the significant associations between occlusal features and disease.

RESULTS

A slide from the retruded contact position to maximum intercuspation > or =2 mm and mediotrusive interferences were the only 2 occlusal features significantly associated with the presence of myofascial pain according to the RDC/TMD criterion symptoms. The odds ratio for myofascial pain was 2.57 for a slide from RCP to MI > or =2 mm and 2.45 for mediotrusive interferences. The percentage of the total log likelihood for myofascial pain explained by the significant occlusal factors amounted to 10.8% (Nagelkerke's R2=0.108). The multifactorial model, including the 2 significant occlusal factors, showed an acuracy to predict disease of 66.7% (sensitivity 71.6%; specificity 58.3%).

CONCLUSION

Occlusal features showed a low predictive value to detect muscle disorders of the stomatognathic system. Multifactorial complex pathologies, such as TMD, should be studied using multivariate statistical analyses, as univariate models may overestimate some resulting associations.

Effect of artificial occlusal interferences depends on previous experience of temporomandibular disorders

Studies on artificial interferences in subjects with no temporomandibular (TMD) history have shown adaptation to the interference within a fairly short period of time. The role of occlusal factors in the etiology of TMD has therefore been questioned. The results might have been different, however, if subjects with a prior TMD history had been included in the study groups. To test this assumption in a randomized double-blind clinical set-up, we included healthy women without (n = 26) as well as with (n = 21) an earlier TMD history. Both groups were randomly divided into true and placebo interference groups. Artificial interferences were introduced in the true interference groups and simulated in the placebo groups. The subjects were followed for 2 weeks, after which the interferences were removed. The subjects without a TMD history showed fairly good adaptation to the interferences, but the subjects with a TMD history and true interferences showed a significant increase in clinical signs compared to the other groups. We suggest that the etiological role of occlusal interferences in TMD may not have been correctly addressed in previous studies with artificial interferences and allow no conclusions as regards TMD etiology.

Occlusion and temporomandibular disorders (TMD): still unsolved question?

The rejection of the occlusal hypothesis cannot be justified with the present empirical evidence.

Control of bias in randomized controlled trials published in prosthodontic journals

STATEMENT OF PROBLEM

Randomized controlled trials (RCTs) have become the gold standard for evaluating the effectiveness of treatment interventions. If not properly controlled, bias in the design of trial methodology can affect the validity of the study results.

PURPOSE

The purpose of this investigation was to assess the methodological quality of RCTs published in 3 prosthodontic journals over a 10-year period.

MATERIAL AND METHODS

Issues of The International Journal of Prosthodontics, The Journal of Prosthetic Dentistry, and The Journal of Prosthodontics published between 1988 and 1997 were searched manually to identify RCTs. Specific inclusion and exclusion criteria were established to identify articles about studies that qualified as RCTs. Two independent reviewers evaluated all qualified RCTs on the basis of how potential sources of bias in the trial methodology were controlled. Three areas-control of bias at entry, control of bias in assessment of outcome, and control of bias after entry-were evaluated with a scheme developed through the Cochrane Collaboration. A score of 1 or 0 was assigned for each of the 3 potential sources of bias, with the maximum quality score for an RCT being 3 (good bias control) and the minimum 0 (poor control). Frequencies were calculated for each dimension of trial methodology and overall quality scores of the RCTs.

RESULTS

Sixty-two RCTs were identified from 3631 articles screened. The method of randomization was explicit in only 47% of the RCTs. Forty percent of RCTs incorporated blinding in the assessment of outcome, and 76% accounted for all subjects at the end of the study. Overall quality scores revealed that only 16% of RCTs attempted to control bias in all 3 areas examined. Forty percent were deficient in 1 area, 34% were deficient in 2 areas, and 10% were deficient in all areas examined.

CONCLUSION

The quality of RCTs published in prosthodontic journals may be improved by minimizing potential sources of bias and adequately reporting trial methodology.

An evidence-based assessment of occlusal adjustment as a treatment for temporomandibular disorders

STATEMENT OF PROBLEM

Occlusal adjustment therapy has been advocated as a treatment modality for temporomandibular disorders. In contrast to this position, a panel at the 1996 National Institute of Health technology assessment conference on TMD indicated that no clinical trials demonstrate that occlusal adjustment is superior to noninvasive therapies.

PURPOSE

This article summarizes the published experimental studies on occlusal adjustments and temporomandibular disorders.

MATERIAL AND METHODS

Eleven research experiments involving 413 subjects with either bruxism (n = 59), temporomandibular disorders (n = 219), headaches and temporomandibular disorders (n = 91), or chronic cervical pain (n = 40) were selected for critical review from the English dental literature.

RESULTS

Three experiments evaluated the relationship between occlusal adjustment and bruxism. Six experiments evaluated occlusal adjustment therapy as a treatment for patients with primary temporomandibular disorders. One experiment looked at occlusal adjustment effect on headache/temporomandibular disorder symptoms; another looked at its effect on chronic neck pain. Most of these experiments used a mock adjustment or a comparison treatment as the control condition in adults who had an existing nonacute general temporomandibular disorder. Overall, the data from these experiments did not demonstrate elevated therapeutic efficacy for occlusal adjustment over the control or the contrasting therapy.

CONCLUSION

The experimental evidence reviewed was neither convincing nor powerful enough to support the performance of occlusal therapy as a general method for treating a nonacute temporomandibular disorder, bruxism, or headache.

Quantification and validation of predictive values of occlusal variables in temporomandibular disorders using a multifactorial analysis

STATEMENT OF PROBLEM

A consensus is lacking on the association between occlusal variables and temporomandibular disorders (TMDs).

PURPOSE

This study estimated the maximum potential power of occlusal variables to differentiate patients with TMD from asymptomatic normal adult subjects.

MATERIAL AND METHODS

The occlusal characteristics in 2 sets of female patients with intracapsular TMD (1993, n = 257, and 1998, n = 124) differentiated into disk displacement and osteoarthrosis subdiagnoses were compared with asymptomatic female controls (n = 51 and 47) with multiple logistic regression analysis. Significant variables and total contribution to the log likelihood were compared with the predictive value of univariate analysis, including sensitivity and specificity.

RESULTS

Occlusal factors in the females (1993, 1998) explained no more than 4.8% to 27.1% of the log likelihood. In comparison to the logistic regression analysis, univariate analysis was less predictive of patients with TMD, due to notably lower sensitivity. Patients with disk displacement were mainly characterized by unilateral posterior crossbite and longer RCP-ICP slides. Patients with osteoarthrosis were most consistently characterized by longer RCP-ICP slides and larger overjet, and in part to reduced overbite. Significant relative risk for disease (odds ratio > 2:1) was mainly associated with infrequent, more extreme ranges of occlusion measurements.

CONCLUSION

Occlusal factors may be cofactors in the identification of patients with TMD, but their role should not be overstated. Some occlusal variation may be a consequence of rather than a cause for TMD. Single variables have more limited value and it takes sets of adverse variables to model TMD. Combinations of variables appear to be disease specific. Some extreme ranges of occlusion were the domain of patients with TMD, but most patients were within the normal ranges.

Analysis of occlusal variables, dental attrition, and age for distinguishing healthy controls from female patients with intracapsular temporomandibular disorders

STATEMENT OF PROBLEM

Confusion about the relationship of occlusion to temporomandibular disorders (TMD) persists.

PURPOSE

This study attempted to identify occlusal and attrition factors plus age that would characterize asymptomatic normal female subjects.

METHODS AND MATERIAL

A total of 124 female patients with intracapsular TMD were compared with 47 asymptomatic female controls for associations to 9 occlusal factors, 3 attrition severity measures, and age using classification tree, multiple stepwise logistic regression, and univariate analyses. Models were tested for accuracy (sensitivity and specificity) and total contribution to the variance.

RESULTS

The classification tree model had 4 terminal nodes that used only anterior attrition and age. "Normals" were mainly characterized by low attrition levels, whereas patients had higher attrition and tended to be younger. The tree model was only moderately useful (sensitivity 63%, specificity 94%) in predicting normals. The logistic regression model incorporated unilateral posterior crossbite and mediotrusive attrition severity in addition to the 2 factors in the tree, but was slightly less accurate than the tree (sensitivity 51%, specificity 90%). When only occlusal factors were considered in the analysis, normals were additionally characterized by a lack of anterior open bite, smaller overjet, and smaller RCP-ICP slides. The log likelihood accounted for was similar for both the tree (pseudo R(2) = 29.38%; mean deviance = 0.95) and the multiple logistic regression (Cox Snell R(2) = 30.3%, mean deviance = 0.84) models.

CONCLUSION

The occlusal and attrition factors studied were only moderately useful in differentiating normals from TMD patients.

Developing a register for randomized controlled trials in prosthodontics: results of a search from prosthodontic journals published in the United States

STATEMENT OF PROBLEM

Treatment decisions are often made despite absence of evidence from well-conducted clinical trials. Conclusions about treatment efficacy derived from nonexperimental approaches often overestimate treatment effect. Randomized controlled trials (RCTs) provide the most reliable basis for evaluating effectiveness of treatment interventions.

PURPOSE

This study attempted to identify and catalog RCTs in prosthodontic journals published in the United States as an initial step in creating a register of clinical trials that would be a resource in setting up systemic overviews of prosthodontic literature.

METHODS

The International Journal of Prosthodontics, The Journal of Prosthetic Dentistry, and The Journal of Prosthodontics published between 1988 and 1997 were searched manually to identify clinical trials. Clinical trials had to meet the following criteria for inclusion in the register: the trial must involve human subjects, must include at least 2 treatment groups, and treatment group allocation must be randomized.

RESULTS

A total of 3,631 articles in 196 journal issues were screened. Sixty-two articles (1.7%) met the minimum criteria for inclusion in the RCT register.

CONCLUSION

Given the lack of randomized controlled trials in prosthodontic journals, a concerted effort by the organized prosthodontic community should be made to screen national and international journals and contribute to the development of a register of randomized controlled trials relevant to prosthodontics.

The effects of a single intercuspal interference on electromyographic characteristics of human masticatory muscles during maximal voluntary teeth clenching

In 13 healthy subjects (eight men and five women, mean age, 22 years), an aluminum intercuspal interference (height, 0.25 mm) was placed on the maxillary right first premolar to study its effect on the contractile symmetry of the right and left masseter and anterior temporalis muscles when measured through a Percentage Overlapping Coefficient (POC), derived from surface electromyographic recordings of maximum voluntary teeth clenching. Additionally, and to estimate the potential of the experimental intercuspal interference to induce lateral displacement of the mandible, a Torque Coefficient (TC) was derived from surface electromyographic recordings. The conclusion was that the experimental occlusal interference gave rise to asymmetric contractile activity in the studied mandibular elevator muscles as well as a potential to displace the mandible in a lateral direction.

Occlusal adjustment and the incidence of demand for temporomandibular disorder treatment

STATEMENT OF PROBLEM

Contrary to clinical opinion, the structural risk from dental occlusion in temporomandibular disorders has been questioned or considered to be insignificant in clinical practice.

PURPOSE

This study tested the effect of elimination of occlusal interference through occlusal adjustment, on the incidence of temporomandibular disorders.

MATERIAL AND METHODS

In a controlled clinical trial of 146 healthy children and adolescents, half of the subjects underwent occlusal adjustment aimed at elimination of the presumed structural risk, and the other half underwent mock adjustment. Adjustments were repeated every 6 months over a period of 4 years. The outcome variable was the incidence of temporomandibular disorders, operatively defined as request for treatment of symptoms characteristic of the disorders with presence of clinical signs demonstrated in the muscles of mastication and/or jaw joint.

RESULTS

The cumulative incidence rate was 9/67 in the mock adjustment group and 1/60 in the real adjustment group, for a relative risk of 8.06. The difference between groups was statistically significant (p = 0.019).

CONCLUSIONS

Elimination of the presumed structural risk from the dental occlusion appeared to significantly reduce the incidence of temporomandibular disorders in a select group of young subjects.

Prevention of temporomandibular disorder-related signs and symptoms in orthodontically treated adolescents. A 3-year follow-up of a prospective randomized trial

Recommendations about the need for occlusal adjustment after malocclusion therapy are inconclusive. A total of 123 orthodontically treated healthy adolescents (88 girls, 35 boys; 14.8 +/- 1.7 years old) agreed to participate in the present study. The subjects were interviewed and examined for signs and symptoms related to temporomandibular disorder (TMD) and were randomly allocated to intervention (n = 63) and control (n = 60) groups. At base line, occlusal adjustment was carried out for the intervention group and repeated every 6 months thereafter as needed. Mock adjustments were performed for the control group. At the end of the 3rd year 118 subjects (96%) turned up for re-examination. The number of subjects with palpatory pain of the masticatory muscles, and with occlusal centric slides decreased significantly in the intervention group but not in the control group (P < 0.001). In conclusion, occlusal adjustment therapy may prevent the occurrence of TMD signs in orthodontically treated healthy adolescents.

The role of occlusal adjustment in the management of temporomandibular disorders

The use of occlusal adjustment as a treatment for temporomandibular disorders has been questioned because of lack of evidence that occlusal factors play an etiologic role; lack of evidence that this irreversible treatment modality has sufficient efficacy, when reversible modalities are available; the self-limiting character of the disorders; and the possibility of adverse effects. However, controlled clinical trials have yielded results that are difficult to explain unless occlusal factors have a causal role in temporomandibular disorders. Controlled clinical trials also suggest an effect for occlusal adjustment on chronic headaches and on chronic neck and shoulder pain in comparison with conventional treatments. Moreover, no adverse effects of properly conducted occlusal adjustments have been reported. In view of the possibility that occlusal factors have a causal role in temporomandibular disorders, research efforts on the role of occlusion should be intensified, and teaching should be revised accordingly.

The validity and utility of disease detection methods and of occlusal therapy for temporomandibular disorders

Our evaluation of the clinical usefulness or devices for the diagnosis or treatment of temporomandibular disorders (TMD) led to the conclusion that the only current gold standard for TMD is a global clinical examination, because none of the instruments can be said to provide more than ancillary documentation and none have proven diagnostic validity or utility. Regarding the therapeutic efficacy of occlusal adjustment, we could find no comparative studies that test the efficacy of occlusal adjustment in preventing TMD. The studies we reviewed on the relationship of occlusion to TMD are not convincing, powerful, or practical enough to make any recommendations about a causal association.

The concepts prevalence, need for treatment, and prevention of temporomandibular disorders: a suggestion for terminology

The concepts active and passive treatment need and active and passive prevention need are suggested, to systematize some concepts used in discussions about temporomandibular disorders (TMD), to separate the treatment need figures from the prevalence figures, and to understand the great variation among TMD prevalence studies. On the basis of a summary of recently published papers and on a clinical 2-year follow-up study of 411 subjects, the suggestions seem to provide a reasonably good fit with clinical experience and earlier epidemiologic studies of TMD.

Experimental occlusal interferences. Part IV. Mandibular rotations induced by a pliable interference

In 12 subjects, a pliable, yet unbreakable, intercuspal interference (aluminum shim onlay splint; uniform height of 0.25 mm) was placed between either the right or left maxillary and mandibular second premolars and first molars. During brief and forceful biting (dynamic chewing stroke of about 20 kg force) the interference emulated a semisoft food bolus, and at the end of biting (subsequent static clenching stroke of about 20 kg force) it emulated a rigid metal interference. During dynamic/static biting, rotational electrognathography measured maximum frontal and horizontal plane torque of the right and left mandibular condyles. Eleven subjects (92%) showed frontal plane upward rotation (mean of 1.0 degree) of the condyle contralateral to the interference, and one subject (8%) showed frontal plane upward rotation (0.4 degree) of the condyle ipsilateral to the interference. Two subjects (17%) showed no horizontal plane rotation; seven subjects (58%) showed backward rotation (mean of 0.4 degree) of the condyle contralateral to the interference; and three subjects (25%) showed backward rotation (mean of 0.3 degree) of the condyle ipsilateral to the interference. It is suggested that, in the presence of an occlusal interference, mastication may have both short- and long-term detrimental effects.

Odds ratio in the estimation of the significance of occlusal factors in craniomandibular disorders

The usage of odds ratios for estimating the significance of occlusion is based on the assumption that the aetiological factors are additive and interchangeable in several different composite causes. If the factor studied is a necessary causal factor, odds ratios cannot be used in risk estimation. The present study analysed odds ratios in a sample of children half of whom had undergone an annual prophylactic elimination of occlusal interferences. The sample consisted of 178 children followed up for 5 years from the baseline age of 5 or 10. The distribution of interferences was computed for children with tenderness of the masticatory muscles ('cases'), and for children without ('controls'). Although the increase in the number of children free from interferences was not remarkable, the overall result was statistically significant (P < 0.01). None of the children free from interferences showed muscular tenderness at any of the annual examinations. Therefore, odds ratios could not be calculated in our study sample. It is concluded that estimation by means of odds ratios of the significance of occlusal factors in CMD may be misleading.

Annual review of selected dental literature: report of the Committee on Scientific Investigation of the American Academy of Restorative Dentistry

The annual review of selected dental literature this year cites 384 published papers and reports. This year's review contains more editorial comment than reviews of years passed. New data on the biological responses to materials is emphasized in several sections. Observations on new compounds able to prevent plaque formation are presented. Clinically relevant advances in knowledge concerning the etching of different tooth structures are reported along with the effect of etching procedures on the dental pulp. Evaluation of periodontal diseases in all age groups is a topic. Limitations of current diagnostic techniques in periodontal disease, temporomandibular disorders, and implant therapy are included. There are new views on the use of dental amalgam. The future use of dental mercury is predicted. Interest in new ceramic systems is indicated as the demand for esthetics continues. Clinical information is emphasized over scientific information throughout this year's review.