Orofacial pain in cancer: part I--mechanisms

The mechanisms involved, and possible treatment targets, in orofacial pain due to cancer are poorly understood. The aim of the first of this two-part series is to review the involved pathophysiological mechanisms and explore their possible roles in the orofacial region. However, there is a lack of relevant research in the trigeminal region, and we have therefore applied data accumulated from experiments on cancer pain mechanisms in rodent spinal models. In the second part, we review the clinical presentation of cancer-associated orofacial pain at various stages: initial diagnosis, during therapy (chemo-, radiotherapy, surgery), and in the post-therapy period. In the present article, we provide a brief outline of trigeminal functional neuro-anatomy and pain-modulatory pathways. Tissue destruction by invasive tumors (or metastases) induces inflammation and nerve damage, with attendant acute pain. In some cases, chronic pain, involving inflammatory and neuropathic mechanisms, may ensue. Distant, painful effects of tumors include paraneoplastic neuropathic syndromes and effects secondary to the release of factors by the tumor (growth factors, cytokines, and enzymes). Additionally, pain is frequent in cancer management protocols (surgery, chemotherapy, and radiotherapy). Understanding the mechanisms involved in cancer-related orofacial pain will enhance patient management.     

Orofacial pain: basic mechanisms and implication for successful management

Orofacial Pain is the field of dentistry devoted to the diagnosis and management of chronic, complex, facial pain and oromotor disorders. This specialty in dentistry has developed over a number of years out of the need for better understanding of a group of patients who somehow were not clearly suffering from dental pain disorders, but still did not seem to have a clearly defined medical problem. After a long period of treating patients based on the mechanicist aspect of the disease, our profession has realized the importance of basic knowledge and differencial diagnosis in order to proper manage these patients. This modification in the approach has caused severe changes in education as well as in clinical activities. Historically considered as a problem of occlusion, Orofacial Pain, including Temporomandibular Disorders (TMD) has recently reached the status of "Specialty" in Brazil. Therefore, this paper aims to discuss the main differences between musculoskeletal and neuropathic pain and the importance of basic knowledge to perform successful management.     

Orofacial pain and neurosensory disorders and dysfunction in cancer patients

Orofacial pain and altered nerve sensation may be the initial sign of oropharyngeal or nasopharyngeal cancer. This article focuses on the most common orofacial pain conditions and neurosensory alterations that affect cancer patients, such as neuropathic pain, muscle spasm or contractures, mucositis, and increased or decreased sensory discrimination in the affected area. The various pharmacotherapeutic modalities for cancer pain management ranging from non steroidal anti-inflammatory drugs (NSAIDs) for mild pain to opioids for severe pain are discussed in detail.     

Orofacial disease: update for the clinical team: 9. Orofacial pain

Orofacial pain, the main reason why many patients seek dental advice, usually has a local cause--primarily the sequelae of dental caries--but a wide range of diseases, particularly neurological, psychogenic and vascular disorders, can cause orofacial pain. This article will discuss disorders that can present with pain and the neurological, psychogenic and vascular causes of orofacial pain. The first article in this series made several general observations on diagnosis and treatment which should be borne in mind in relation to the material presented here.     

Orofacial pain assessment and management for patients with dementia: A meta‐ethnography

Delivering dental treatment for patients with dementia can be challenging, and the complexity of treatment provision can increase as dementia progresses. Treatment at the later stages of dementia can be associated with ethical challenges and procedural risk meaning that a comprehensive patient assessment is crucial; the presence of orofacial pain is a key indication for active intervention from dental teams. To explore the process of oro‐facial pain assessment and management, a comprehensive review of qualitative literature was undertaken by searching six electronic databases. No literature specific to orofacial pain assessment was identified. The inclusion criteria were widened to explore assessment and management of pain in general for patients with dementia. Meta‐ethnography with reciprocal translation was used to identify key concepts and themes and synthesise information applicable to the dental setting. Three major themes arose as follows: challenges with pain assessment, challenges with pain management and logistics and education. Healthcare teams struggle with pain identification in patients with dementia though many signs were identified which may suggest a patient is experiencing pain. The long‐term knowledge of individual patients held by family members and care teams can allow identification of deviation from patients’ normal states; this knowledge can assist healthcare professionals in determining whether to provide specific treatments or interventions. Pain assessment tools were found to be problematic and are unlikely to be a practical solution to use for complex patients in dental settings. Education for dental and wider care teams on orofacial pain would be highly valuable; yet, this needs to be based on suitable evidence.     

Orofacial pain and sensory disorders in the elderly

Many orofacial pain conditions occur in the elderly. Specifically,this article reviews the prevalence of general and orofacial-related pain in the elderly. The authors also describe and discuss the likely disorders and diseases that produce facial pain and burning pain in the mouth. They do not cover jaw joint pain, oral sores, or ulceration-induced pain, as these conditions are better discussed in the context of arthritis and oral pathologies of the mouth. The authors discuss oral motor disorders, myogenous pain, vascular pain, headaches, trigeminal neuralgia, trigeminal neuropathic dis-ease, postherpetic neuralgia, burning mouth syndrome, and occlusal dysesthesia.     

Orofacial pain and jaw muscle activity: a new model

Two major theories proposed to explain the effect of pain on muscle activity are the Vicious Cycle Theory and the Pain Adaptation Model. Comprehensive reviews demonstrate conflicting or limited evidence in support of a critical aspect of the Vicious Cycle Theory, namely that pain leads to increased muscle activity. The Pain Adaptation Model proposes that changes in muscle activity limit movement and thereby protect the sensorimotor system from further injury. This model is generally considered the most appropriate explanation of the effect of pain on muscle function. Although there is much literature consistent with the model, there are a number of lines of evidence that appear inconsistent with it. Possible reasons for the lack of consistency between studies include the functional complexity of the sensorimotor system (eg, the possibility of different pain effects at different sites within functionally heterogeneous muscles), and the multidimensional nature of pain. The latter consists of sensory-discriminative, cognitive-evaluative, and motivational-affective components, where factors such as pain location, intensity, and characteristics and other supraspinal/suprabulbar influences may modify the effects of pain on motor activity. The variety of changes in electromyographic (EMG) activity features during pain suggests that pain and motor function are not hardwired. The authors propose that the existing Pain Adaptation Model is a subset of a broader model that could be called the Integrated Pain Adaptation Model. Given the recent view of pain as a homeostatic emotion requiring a behavioral response, this new model states that pain results in a new, optimized recruitment strategy of motor units that represents the individual's integrated motor response to the sensory-discriminative, motivational-affective, and cognitive-evaluative components of pain. This recruitment strategy aims to minimize pain and maintain homeostasis.     

Orofacial pain: racial and sex differences among older adults

OBJECTIVES: This study investigated racial differences in orofacial pain symptoms in a sample of older adults. Orofacial pain prevalence, persistence, severity, and behavioral impact were assessed. We also tested whether sex and race interact, such that racial differences are only observed for a single sex, or whether sex differences only occur within a single racial group. METHODS: Telephone interviews were conducted with a stratified random sample of 1,636 community-dwelling older (age 65+ years) north Floridians. RESULTS: Racial differences were not found for 12-month prevalence or pain ratings for any painful oral symptom, or in the total number of symptoms. The most consistent racial differences were in behavioral impact associated with pain. Blacks reported greater behavioral impact as defined by pain having reduced their daily activities or motivating them to take some action in response to pain. For toothache pain, that action was more likely to have been some form of self-medication. These relationships persisted after controlling for socioeconomic status, approach to health care, and pain intensity in multivariable models. CONCLUSION: Although pain prevalence is an important public health variable, this study suggests that other pain-related variables, such as behavioral impacts, are useful when describing disparities associated with orofacial pain.     

Orofacial pain of cardiac origin: a case report

It is the responsibility of the dentist to make the differential diagnosis of pain in the region of the oral cavity. Cardiac pain most commonly radiates to the left arm, shoulder, neck and face. In rare instances the pain may present as dental pain. In this case report, the patient presented with complaints of intense bilateral pain in the jaws which was diagnosed as pain of cardiac origin.     

Orofacial pain in patients with sickle cell disease

The potential danger of low oxygen tension to patients with sickle cell disease is widely known. However, less well known is the phenomenon of patients with sickle cell disease presenting with toothache in the absence of any dental pathology. This study investigated the experience of orofacial pain in three matched groups, comprising patients with sickle cell disease, sickle cell trait and patients with no known blood dyscrasia. There were no differences in pain experience between those groups with sickle cell trait and no known blood dyscrasia. The sickle cell disease patients experienced significantly more orofacial pain in the same 12-month period than the other groups. The pain was also more frequent and of longer duration. In two-thirds of those sickle cell disease patients who experienced toothache, no dental pathology was found, in direct contrast to patients with trait or no known blood dyscrasia. Sickling of blood cells within the dental pulp in a sickle cell crisis may result in pain within teeth. These patients may then present as experiencing toothache in the absence of any dental pathology. General dental practitioners should be aware of this phenomenon when providing care for these susceptible patients.