An exploratory study on increases in masseteric muscle activity induced by caffeine.

In a crossover double blind experimental design, the nocturnal masseteric activity of 14 selected volunteers was evaluated by means of a portable electromyograph recording unit. The recordings lasted for a period of 16 days following ingestion of caffeine or placebo for five specific days each. There were no significant differences between caffeine or placebo on masseteric activity associated with bruxism. But when the two periods were compared, there was a tendency towards reduction of masseteric area activity and increase of stress levels in the second period of ingestion.