# Temporomandibularibular Disorders and Bruxism in Patients Attending a Tinnitus Clinic
## 1 Introduction  
Temporomandibularibular disorder (TMD) refers to the whole range of disorders involving the masticatory muscles, the temporomandibular joint (TMJ), and nearby structures [1]. It occurs in approximately 5-12% of the population, and about 50-60% of individuals with TMJ disorders will seek treatment [2]. TMD affects mostly women, especially those aged 20-45 years, and represents the main reason for facial pain caused by non-odontogenic reasons [3]. A patient presenting with TMD characteristically feels pain in the head, face, ear, or teeth, and may exhibit TMJ dysfunction, such as limited mouth opening, TMJ clicking, and functional discomfort. The etiology of TMD is multifactorial, involving genetics, biology, environmental reasons, cognition, emotional and psychological distress, age, sex, and habits, such as smoking or teeth clenching [4]. The most common clinical signs include chronic myofascial pain of the masticatory muscles, and limited mouth opening [5]. TMD can occur concomitantly with chronic tension headaches, migraine headaches, fibromyalgia/generalized pain, lower back pain, autoimmune diseases, sleep apnea, and psychiatric disorders [6]. Clicking sounds originating from the TMJ are generated during mouth opening, closing, or movement. The sound derives from the extension of the condylar head over the edge of a displaced articular disc. When clicking is objectively verified by the examiner, further investigation is warranted to evaluate the occlusion, joints, and the masticatory muscles [7], although clicking alone does not increase the risk of developing TMJ pain [8]. TMD is often diagnosed by the Diagnostic Criteria for TMD (DC/TMD) or the Research Diagnostic Criteria for TMD (RDC/TMD) from which the DC/TMD had originated. DC/TMD is composed of Axis I, which provides physical information, including articular information (e.g., TMJ disc displacement) and extra-articular information (e.g., facialmyalgia), and Axis II which provides psycho-social information (e.g., anxiety) [6]. Axis II is especially relevant to the current study because of the observed overlap of the reported psychological factors contributing to TMD and tinnitus [3]. Bruxiism is a repetitive uncontrolled parafunction consisting of excessive and abnormal activation of the TMJ, the jaws, and the masticatory muscles (especially the temporalis and the masseter muscles), such as clenching or grinding of the teeth by bracing or thrusting of the mandible. It is argued that bruxiism should not be considered a disorder but rather a risk factor for oral health because it is a behavior that may or may not increase the risk for chronic muscular pain, TMJ pain and disc disorder, teeth wear or destruction, and TMD [9]. There are two types of bruxiism, sleep and awake [10]. Sleep bruxiism, whose prevalence is 8% among the adult population, originates in the brainstem by the reticular ascending system's increasing the activity of the motor and autonomic systems of the masticatory muscles [11]. Awake bruxiism, which is prevalent in 20% of the population, is strongly related to stress and anxiety. Little is known about its physiology and pathophysiology, but stress, anxiety, and low socioeconomic status have been considered risk factors. Unlike sleep bruxiism, which is mostly characterized by teeth grinding, awake bruxiism is usually associated with jaw clenching, making its diagnosis more complicated signs are not always apparent, such as the absence of dental wear [12; 13; 14; 15; 16]. The diagnosis of bruxiism is problematic since it is based upon medical history and examination. Not all patients are aware of their parafunctions and oral behaviors, nor do they all present with definitive signs of the condition. Specifically, a hallmark of bruxiism is dental wear, but clenching and bracing of the jaws, while causing pain, do not necessarily cause teeth wear. The impression of the teeth on the tongue is called \"indentations\", this is also a sign of bruxiism.