Methodological aspects in the study of periodontal breakdown in rats: influence of the presence and time of ligature.

The aim of the present work was to evaluate the effect of different times on alveolar bone loss (ABL) and whether the presence of ligature on one side affects ABL on the contralateral site. This is a secondary analysis of databases from studies conducted at the Federal University of Rio Grande do Sul. Included studies used ligature-induced periodontal disease in rats. In order to be included, the studies were required to have a control group without any ligatures and an intra-group control. Three studies were included, which used different time periods: 2 weeks with ligature and 8 weeks without ligature; 5 weeks with ligature and 17 weeks without ligature; 22 weeks with and without ligature. Animals were raised similarly and sacrificed by decapitation. Maxillae were defleshed with 9% sodium hypochlorite. Pictures were taken and five measurements were obtained from each image. The presence of ligature generated significantly greater ABL compared to sides without ligature. Comparing sides with ligature, ABL was lower at 2 weeks than at 5 and 22 weeks. Sides without ligature showed no significant difference between 8 and 17 weeks for spontaneous periodontitis. However, after 22 weeks, animals exhibited significantly greater ABL when compared to other periods. The presence of ligature on one side did not influence ABL on the contralateral side. Two weeks of ligature-induced periodontal disease seems to be sufficient to demonstrate significant ABL. Teeth without ligature contralateral to teeth with ligature may be considered sound controls, thereby reducing the amount of animals needed in periodontal research.