"Parafunctional grinding of teeth or an oral habit consisting of involuntary rhythmic or spasmodic non-functional gnashing, grinding or clenching of teeth in other than chewing movements of the mandible which may lead to occlusal trauma." "Periodic repetitive clenching or rhythmic forceful grinding of the teeth." Classification by temporal pattern
Bruxism can be subdivided into two types based upon when the parafunctional activity occurs – during sleep ("sleep bruxism"), or while awake ("awake bruxism"). This is the most widely used classification since sleep bruxism generally has different causes to awake bruxism, although the effects on the condition on the teeth may be the same. The treatment is also often dependent upon whether the bruxism happens during sleep or while awake, e.g., an occlusal splint worn during sleep in a person who only bruxes when awake will probably have no benefit. Some have even suggested that sleep bruxism is an entirely different disorder and is not associated with awake bruxism. Awake bruxism is sometimes abbreviated to AB, and is also termed "diurnal bruxism", DB, or "daytime bruxing". Sleep bruxism is sometimes abbreviated to SB, and is also termed "sleep-related bruxism", "nocturnal bruxism", or "nocturnal tooth grinding".
The fact that WPW patients are young and do not have structural heart disease, lead to using catheter ablation of the APs with the elimination of the atrial fibrillation as well as the episodes of re-entrant ventricular tachycardia. This elimination of the atrial fibrillation with ablation implies APs have some pathophysiologic role in the development of a-fib in the WPW patient.Functionally defined re-entry does not require the alternative anatomically defined circuit accessory pathways and it may not reside in just one location. Ventricular fibrillation (VF) following ventricular tachycardia (VT) may be described as a functionally defined re-entry problem caused by multiple mini re-entrant circuits spontaneously created within the ventricular myocardium. The original re-entrant circuit breaks down into multiple mini reentrant circuits. (VF becoming the grand finale of a single prolonged VT larger circus movement, propagating change in the "functional core" of the ventricular myocardium, dissipating mini reentrant circuits, exhibited as ventricular fibrillation.) Ischemia, electrolyte, pH abnormalities, or bradycardia are potential causes of functionally defined re-entry due to changes in the properties of the cardiac tissues functional core. (No accessory pathway required). For reentry to occur, the path length of circuit should be greater than the wave length (ERP × conduction velocity) of impulse. See also
AV reentrant tachycardia
AV nodal reentrant tachycardia

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