['Although some studies have reported a negative influence of caffeine on bone metabolism, there is no information about its effect on the progression of periodontitis. The aim of this study was to evaluate the effect of high doses of caffeine on ligature-induced periodontitis in rats.', 'Twenty-two Wistar rats were assigned to one of the following groups: non-caffeine group (n = 12) = animals without caffeine ingestion; caffeine group (n = 10) = animals ingesting 10 mg/100 g body weight/day of caffeine via drinking water for 56 days. Two weeks after the beginning of caffeine intake, one of the mandibular molar was randomly assigned to receive a ligature, whereas the contralateral molar was left unligated. Forty-two days later, the animals were sacrificed, and the specimens were processed to obtain decalcified sections. The area of periodontal ligament and/or bone loss in the furcation region of the first molars was histometrically determined.', 'Caffeine intake did not have a direct effect on the alveolar bone loss in unligated teeth. But on the ligated tooth, a greater area of bone loss was observed in the animals that ingested caffeine compared to those that did not (P <0.05).'] Does administration of high doses of caffeine increase alveolar bone loss in ligature-induced periodontitis in rats?