JOR-CORE recommendations on rehabilitation of temporomandibular disorders

In the long history of temporomandibular disorders (TMD), the term ”rehabilitation“ has been often associated with ”occlusal rehabilitation“ indicating a specific philosophy in which occlusion is the crucial factor for TMD and that intervention on the occlusion could ”cure“ the problem. In this paper, the term rehabilitation is used to denote any medical, physical, or psychological treatment which brings or restores an individual to a normal or optimal state of health, and this revised concept therefore significantly broadens the scope of rehabilitation of TMD. The purpose of the JOR-CORE in Siena, 2009 was to critically examine the current state-of-the-science in the field of TMDs. This lead to four extensive reviews (1-4) and the present summaries and recommendations for future research into rehabilitation of TMDs. The pathophysiology of temporomandibular disorders (TMD) is complex and involves several mechanisms discussed in Cairns (1). The principal symptom of TMD that causes sufferers to seek medical care is pain in the temporomandibular joint (TMJ) and/or masticatory muscles. Degenerative changes in the TMJ likely underlie pain in only a subgroup of patients with TMD and consequently there is often a poor correlation between the severity of pain complaints and pathological changes in joint and muscle tissues. It has been demonstrated that some patients with TMD appear to have altered central nervous system pain processing and deficits in their ability to recruit endogenous analgesic mechanisms; collectively, these two central processes likely contribute to the development of chronic pain in certain individuals. Recent findings suggest that the propensity to develop chronic craniofacial pain may also result from genetic variability that leads to altered levels of neurotransmitters implicated in the activation and modulation of pain pathways. Stress reactivity, which may exert significant modulatory effects on pain processing, is recognized as an important factor for both the development and maintenance of pain in TMD and other chronic pain conditions. There is a greater prevalence of TMD amongst women, possibly related to sex hormones and in particular oestrogen, although how different sex hormones promote (or protect) against TMD pain is unknown and therefore remains an area of active research. Unfortunately, the specific mechanisms that underlie TMD-related pain in the vast majority of patients with TMD remain enigmatic. The pathophysiology of TMD and its associated pain clearly requires a sound foundation of scientific knowledge, particularly with regard to its pathogenesis to permit the development of more rational and biologically based approaches to diagnosis and treatment, but despite extensive investigations, this has not yet been achieved. One area of scientific study that might bear fruit in this regard is the determination of predisposing factors for the development of TMD. For example, there are a number of interesting polymorphisms of genes that have been or may be associated with the development of chronic pain conditions. Catechol-O-methyl-tranferase (COMT) is one such gene/gene product that has received much attention, while other possible candidates include serotonin transporters and oestrogen receptors which need to be characterized further. Other potential ‘biomarkers’ of TMD pain could include neuropeptides and neurotransmitters such as calcitonin gene-related peptide (CGRP) and serotonin. Large population-based prospective studies of patients with TMD and healthy controls, such as the ‘Orofacial Pain: Prospective Evaluation and Risk Assessment’ (OPPERA) study currently being supported by the National Institute of Dental and Craniofacial Research in the US, will be necessary to screen for potential markers. Such studies, which focus on putative risks factors, will also be required not only to determine whether predictive markers are reliable but also to define possible mechanisms that regulate/potentiate pain. Furthermore, influence of stress and stress hormones on nociceptive processing and clinical manifestation of TMD pain need to be better understood. It will not be possible to employ rational and biologically based treatments for TMD-related pain until these mechanisms are defined more clearly and precisely than they are now. This should lead to much more effective means for treatment and possibly prevention of TMD-related pain and dysfunction. The current literature does not support any strong associations between occlusal variables and TMD or any significant beneficial or detrimental effects of orthodontic interventions on manifest TMD pain (2). Two caveats, however, need to be recognized. First, there is lack of specificity regarding the definition of ‘occlusion’ and ‘malocclusion’. From a clinical point of view, malocclusion could be any occlusion in which the structural characteristics are different from those established for a theoretically ‘ideal’ occlusion. Although ‘ideal’ is difficult to define, a definition is undoubtedly necessary if rational treatment goals are to be established. It is also critical to recognize that even if ‘ideal’ has no bearing on what is ‘normal’ or ‘typical’ in terms of what is necessary for health, reconstruction of teeth (and supporting structures) according to ideal standards should be a target of treatment if treatment is indicated for other reasons, given that the boundary of what constitutes clinically acceptable is even harder to define. By extension, even if the prefix ‘mal’ means ‘bad’ or ‘ill’, the term ‘malocclusion’ does not necessarily imply that such an occlusion is non-physiologic or that therapy is indicated. Second, it is important to recognize that the term ‘TMD’ has been used, and still is used, very differently in the published literature; for example, the criteria used to denote presence or absence of TMD vary. Indeed, TMD is a very general term that defines a wide group of clinical entities (5), each with quite different and mostly unknown aetiology and pathophysiology (1) that only share in common the clinical features of producing pain and/or functional limitation in the masticatory apparatus. Therefore, research protocols should continue to investigate well-defined subtypes without merging pain, joint sounds and/or mechanical dysfunction as though those symptoms necessarily represent a single disorder. While the current literature clearly supports the absence of a relationship between occlusion and TMD, definitional problems warrant further exploration of possible associations between occlusion and TMD. This recommendation is not made to suggest that such an association exists, but rather it is made in the interest of adhering to the principles of good science: methodological problems that may underlie the absence of proposed relationships deserve further exploration. To pursue further exploration of any possible relationship between occlusion and TMD, three developments are needed: (i) the boundary between acceptable versus pathologic occlusion needs to be much better delineated; (ii) the existing occlusal variables that have already received much attention in published research need to be augmented by additional factors pertaining to the occlusion; and (iii) subtypes of TMD, which may have greater potential to be affected by structural factors, need to be defined based on mechanisms by which the putative structural factors would affect the subtypes and why specific subtypes might be more at risk. It is notable that most research regarding occlusion and TMD has been limited to structural characteristics associated with purely static occlusion (e.g. Angle’s classification) or with pre-defined aspects of articulation (e.g. so-called balancing interferences), assuming that there is necessarily some measurable functional correlate or consequence of the identified characteristic. As more specific recommendations for further exploration, four directions are suggested. The first involves true dynamics of how structure and function interrelate (e.g. mastication where a bolus of food prevents actual tooth contact for the most part, or parafunctional behaviours involving direct tooth–tooth contact) which are poorly understood and clearly deserve more research to understand the relative contributions of structure and functional patterns to TMD onset or maintenance. The second direction involves symptom perception associated with occlusal structures. Based on research in other areas of chronic pain (e.g. back pain), cognitive (e.g. catastrophizing), attentional (e.g. hypervigilance) and perceptual (symptom amplification) factors clearly contribute to psychophysiologic reactivity, treatment seeking and perpetuation of the condition. Of these, one factor in particular, hypervigilance – a state in which an individual, possibly because of a combination of predisposing genetic, psychosocial and environmental factors, is exceedingly aware of the sensory experience associated with a part of the body – merits investigation in association with occlusal variables. Hypervigilance is hypothesized to account for reported outcomes of occlusal treatment in patients with TMD where symptoms associated with the occlusion and, in particular, any modifications performed on the occlusion, independently of its anatomical or functional status, are predominant. Research and better understanding of hypervigilance as a ‘perceptual habit’ in which attention is focused on sensations of a particular type with subjective amplification of perceptions will be needed. It can be speculated that hypervigilance, together with other psychological states such as anxiety or catastrophizing, could be a risk factor in patients with TMD when the therapeutic management includes a modification of the occlusion. Any alteration of the existing occlusal pattern (even if minimally invasive) may, especially in these patients, trigger a ‘bodily distress disorder’ (as has been termed in the back pain area), e.g. an occlusal dysesthesia disorder leading to further distress. A third direction warranting more research is the adaptive capability or resilience of the individual which could influence the definition of ‘normal’ as well as the results of any typical occlusal interventions provided to patients with dental restorative needs (or perhaps aesthetic needs) and who also have a TMD with, we assume, an external aetiology (e.g. trauma to the jaw). One testable hypothesis is that TMD causes irreversible degenerative alterations in the masticatory apparatus and, consequently, the system reacts with adaptive changes, in some cases also irreversible, in an attempt to regain the functional equilibrium. In this clinical situation, any occlusal modification procedure performed in these patients, even if appropriately indicated for occlusal rehabilitation purposes and technically correct, may exceed the adaptation capability of the system, the patient, or both, compromising the clinical status of the condition. Adaptation capability is important for all of dentistry, in that procedures regarded by the profession as routine may not be routine for a given individual, and consequently occlusal modification performed as part of an extensive plan of restorative treatment may exceed that capability and trigger the onset of an iatrogenic ‘TMD’. A fourth direction is the relation between occlusal characteristics and muscle activity. Hyperactivity of the masticatory apparatus may include both functional (chewing habitual food, chewing gum, tobacco, sun seeds) and ‘parafunctional’ oral habits, including but not restricted to non-functional tooth contacts; clenching and grinding of the teeth; biting of objects such as nails, fingers, or lips; and non-tooth contact behaviours such as bracing or thrusting the jaw. Carefully designed research projects are still needed to evaluate whether patients with waking-state or sleep-state non-functional tooth contacts are at higher risk of developing particular subtypes of TMD; what has not been considered with this well-known question is whether the effects of these parafunctional behaviours occur perhaps in an occlusal-dependent manner. The current literature does not support the belief that occlusion per se influences the occurrence of non-functional tooth contacts; however, the interaction between occlusal variables and specific patterns associated with parafunctional activity should be evaluated to determine (i) the boundaries of ‘normal’ for occlusal status; (ii) whether occlusal modifications in patients with TMD are more risky if the patient already has or is independently at risk for increased muscle activity related to parafunctional behaviours; and (iii) whether otherwise non-TMD patients with increased muscle activity (e.g. the individual with chronic asymptomatic sleep-bruxism) are at higher risk of developing a TMD when an occlusal modification In there is a need for critical and of studies the associations between occlusal variables and TMD are to be It is difficult for to current with the of scientific and recommendations and to evaluate the and of published and it is particularly difficult for to this a to this of – a to and the that it is clinically is the of (i) research with (ii) clinical experience and (iii) patient three are to to optimal clinical and of for the and patients a and therapeutic that has the potential to clinical outcomes and of is to focus on how needs to be in clinical research and and to and of clinical and reviews in clinical and research Two important in research and clinical are defined by (i) research means clinically research not only from the but also from clinical research regarding the and of the clinical and the and of and and (ii) clinical is the ability to clinical and to each state and their individual risks and of potential and their and In of a patient and treatment are a combination of (i) the literature and investigations, (ii) clinical experience and (iii) the specific needs of each It would that in clinical the should the The however, is whether are to all three does the of scientific affect of are to and in clinical One limitation to the of is the of studies clinical to the typical clinical often have very specific and which not the typical Therefore, the from an to the patient in the may be used in such as the are considered by some as and not to in a clinical procedures and are a for to clinical some of the principles used in clinical research. because they the research for a specific can be for and from are not however, and consequently, are likely to be most in treatment that are to be This can be used in clinical and for the One limitation is that who are not in would have problems and this to the patient because it requires a significant in how one and scientific in The focus in has been a clinical for In the of is that are how to critically and One limitation is that because not all are in is as a and not into the in the dental for In the medical studies have reported that those patients who have better outcomes than those who Although no that on that specific to TMD has been it is to that the findings from such studies in other areas are to TMD, such that we can suggest that does patient care for TMD. and medical however, may from to and influence the of treatment and its The treatment, as identified is not to The third important in is patient and it was defined by as the and each patient brings to a clinical and which be into clinical if they are to the the individual and of each patient be considered in a particular treatment in clinical problems in study in several studies include and or The results of are not because the diagnosis and treatment from the features of patients and treatments in clinical studies their results to such as pain pain or all of which are if not therapeutic for clinical but which are not necessarily the variables of to a given research would be an research the of TMD pain in a it may be that research the of TMD pain in an The of research is to understand the in rather than with an on understanding the and of and of a are because they a and for both the and of the literature on a specific and it a of identified can be used to and patients that they more understand their and will to the of an individual exceed the of the studies being if there are in the (e.g. from the will be if are the will have to the individual studies in the because one factor the of research findings to a particular patient is the in characteristics between the given patient and the of the particular more studies or studies that not in the could affect the of include the they by on only studies and the to that lack or are Research which of treatment outcomes are needed. Such would those outcomes that are important for a particular patient more than outcomes that are important for that For example, if patient that better was would have higher in than other that considered if patient that affect was most this would be more than Such an might for research summaries that whether the intervention provided in symptom areas that most important for patients, even if different patients different outcomes To in study recommendations should be by the and required by all that clinical studies should be designed in a likely to into at clinical research if not clinical In a clinical research more regarding and of is needed. In more is needed TMD and the that TMD on also on regarding patient with to treatments and the of treatment is currently A methodological would some on this and patient medical often will not studies because of and of In a research it is important that the of treatment outcomes include which together can a more of the pain condition. For patients with TMD with chronic pain, recommendations include these of and with treatment, and and are being the to the also and is a in TMD, and these with pathophysiology and are to as as and and have these to other areas of as it to be a to the concept of into dental and dental clinical with published of the problem. In there is a lack of of the of not the of this the most for of into clinical requires for and to several is with to both and clinical management of of dental treatment can be the to a be even more of and The question therefore be as to how to in this Any of be and into any general dental The of the to the general dental the of an dental and to the patient and the A already in for back pain which the concept of and such as pain that the patient from or that have or psychosocial to treatment to a part of medical care may have for a for in clinical The type of system should the of such dentistry, that all patients in a given the of for limitation and The and presence or absence of would determine whether or not a for limitation and was the number of that routine might for routine of into general clinical and For routine of status of being evaluated and in dental a of as by more is A is regarded as the most for Based on from other areas of the should focus on the of and pertaining to can be in routine clinical two for (i) a for not other and (ii) clinical for The of such should denote specific of The should in no more than distress and and as for as it was that they would significant of and A to be in the would whether it was necessary or (or to with of the to more examine the of of the patient in This is to be a to the of for the as not all patients will need a for The distress of the would also for significant problems such as The distress and needs to be further The second of is the clinical in this is the need for additional and clinical that dental are and well with psychosocial in a of the areas that might be associated with and might further investigation the of the chronic pain, for example, is associated with greater of clinically significant and alterations in central nervous system processing of nociceptive functional limitation status with to and of the for other these areas would be to determine whether the individual has such and the of the need only be but could be For example, pain associated with a temporomandibular disorder should be by problems in function as a in whether there is a between reported symptoms versus such can point to significant other factors to the symptom of history for or of or other for to the such can be or whether the regarding or of treatment are or such on the part of the patient can point to a number of problems that with good care that may also have or the of treatment but that is a that needs attention to whether treatment has been associated with in the treatments not well for the currently This is also by the at each of from is one symptom this of the that is a and requires Other possible warrant further investigation and will be for the most part, by the of the as well as by standards for a history of pain complaints as well as by the medical The two for are into a modification of the care system for a dental patient as in While the procedures for of and should as in of it remains into procedures already and In to that includes of the of psychosocial (and and at would as A patient, or a patient with a the distress and and it is to the exploration of the The are the history of and any further are in the The number of needed to trigger the of the is not yet but clearly associated with any should into clinical and possibly lead to of the it would that any should result in attention for further investigation and or the first symptom status or other could be and if the patient is as an to the treatment the should the treatment, or to treatment is at this the would also all as well as One more of treatment could be treatment the should continue with treatment and continue to for and the second of treatment does not further in the area of is other medical should be considered at this as well in that poor with treatment could be because of medical or psychosocial factors, and each should be further at this without the This further investigation of psychosocial factors would be performed of the for limitation and The can pursue this if and experience the necessary clinical or the could the patient at this to a who has that would be by the at the of in of the distress and however, a that requires to for its and Therefore, these recommendations (i) and be and and (ii) extensive field of the of the proposed for in This is critical to that any changes made in the of clinical are based and The present summaries and recommendations are based on the extensive reviews (1-4) and the four the these recommendations are based on current understanding of the published dental particularly as it to TMD pain, and a to rehabilitation of not only patients with TMD but all dental patients The and are for their support to the JOR-CORE which would not have been possible without the The who are in to the for their and contributions to of this The

Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.