Which of the following is the most common trigger factor for bruxism?
Etiology

Bruxism is a parafunctional activity associated with psychological disturbances and emotional stresses. It is seen in occupations associated with overstress.
Bruxism occurs when freedom in centric is lost. It results from occlusal interferences during sliding from centric relation to centric occlusion. Large discrepancy between centric relation and centric occlusion also contributes to bruxism. Absence of proper interdigitation during transitional dentition also contributes to bruxism.
Various systemic factors such as worm infestations, sub-clinical nutritional deﬁciencies, magnesium deﬁciency, allergies and endocrinal disorders have also been attributed.
Bruxomania is associated with certain cortical lesions of the CNS.

Ref: Textbook of orthodontics Gowrishankar 1st ed page no 557
Temporomandibular joint dysfunction
Pericoronitis
Discrepancy between centric relation and centric occlusion
Acute periodontal disease