Use the following informations to answer this question: What is TMD? Write the answer solely based on the provided information and explain it to a layperson. [Document 1:

joint). The movement is dictated by associated muscles, limited by ligaments and affected by the morphology of the joi nt components a s well as the dentition (1). 
 
Like other joints, the TMJ can be affected by a number of different diseases and disorders. 
Temporomandibular disorders (TMD s) is an umbrella term for pain and dysfunction 
involving the TMJ and its supporting tissues (muscles, tendons).  TMD is recognized as a 
complex disorder with overlapping comorbidities of physical signs and symptoms, as well as changes in behav iors, emotional status, and social interactions as manifestations of general 
central nervous system dysregulation (8).
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Document 2:

1. Introduction
The term temporomandibular disorders (TMD) refer to sev-
eral clinical problems which involve the muscles, TMJ, andassociated structures, or both [1, 2]. TMD is the most com-
mon etiological factor of nondental pain in the orofacial
region and is considered to be a subgroup of musculoskeletaldisorders [3 –5], and its prevalence is very variable and
ranges between 16 and 68% in the literature [6, 7]. Disc dis-placements are the most commonly encountered disorder
type among these groups [8]. However, there is a discrep-
ancy between objective diagnosis and subjective patient-reported pain and disc displacement may be observed nearlyin one-third of the asymptomatic volunteer [7].
Diagnostic imaging is essential for detecting congenital,
developmental malformations neoplasia, fractures, disloca-tions, ankylosis and disc displacement, in ﬂammatory disease,
and arthritis of the TMJ [9]. Magnetic resonance imagingHindawi
BioMed Research International
Volume 2021, Article ID 6032559, 9 pages
https://doi.org/10.1155/2021/6032559
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Document 3:

Temporomandibular Disorders and Quality of Sleep in a Selected Iranian Population. Front Dent . 2019;16(3):20 6-213. 
doi: 10.18502/fid.v16i3.1592  
INTRODUCTION  
Temporomandibular disorder (TMD) is an 
umbrella term for a group of musculoskeletal 
and neuromuscular conditions that involve the temporomandibular joint (TMJ), masti -
catory  muscles, and all other associated 
tissues [1-4]. It is estimated that 50 -80% of the 
population has at 