Masticatory system activities can be classified into two categories; functional category comprises of mastication, phonation, and parafunctional
category includes clenching or grinding of the teeth (called bruxism).
As for the multifactorial etiology, temporomandibular disorder (TMD) is related to anatomic and neuromuscular aspects, as well as parafunctional
habits, postural deviations, traumas and psychosocial changes.
Studies with police with TMD correlated the symptomatology of the syndrome with biopsychosocial symptoms, such as stress, sleep disorders, pain and smoking (33,34), as well as with parafunctional
  Furthermore, the involvement of parafunctional
habits such as bruxism might also be a cause of Temporomandibular joint disorders, while muscular hyperactivity induced by psychological stress and persistently poor oral habits, that might cause muscular fatigue may lead to spasm, resulting in Temporomandibular joint disorders.
Prevalence and association of self-reported anxiety, pain, and oral parafunctional
habits with temporomandibular disorders in Japanese children and adolescents: a cross-sectional survey.
The adverse effects of tobacco use, chronic hyperglycemia, poor oral hygiene status, periodontitis history, and parafunctional
habits on the survival and success of standard dental implants are chronicled in the literature; (3,4,15) however, very few studies have evaluated the risk factors associated with the long-term success of short dental implants.
Since the functional and parafunctional
forces occurring within the mouth result in extremely complex structural responses by the oral tissues, rehabilitation of the oral environment is difficult.
On the other hand, some studies have reported that TMJ disorders originate from malocclusion, parafunctional
habits, stress and trauma (1-4).
NCTSL can lead to significant and progressive loss of tooth structure over time, even in patients without parafunctional
Primary predictors of implant failure are poor bone quality, chronic periodontitis, systemic diseases, smoking, unresolved caries or infection, advanced age, implant location, short implants, acentric loading, an inadequate number of implants, parafunctional
habits and absence/loss of implant integration with hard and soft tissues.
Bruxism is a parafunctional
habit defined among sleep disorders as "repetitive jaw muscle activity characterized by the clenching or grinding of teeth and/or bracing or thrusting of the mandible"  that can occur during the morning (awake bruxism) or night time (sleep bruxism--SB).