Effects of facial tooth movement on the periodontium in rats: a comparison between conventional and low force.

BACKGROUND: Bone dehiscences and gingival recession have been associated with orthodontic arch expansion. The aim of this study was to assess and compare periodontal modelling during application of two force levels. METHODS: The second and third upper molars were orthodontically moved buccally with conventional or low forces for 60 or 90 days in 32 rats. Ten non-treated animals were used as controls. The influence of force level and time on dental, skeletal and periodontal parameters (i.e. height and thickness of gingiva and bone) was assessed on histomicrographs using a mixed linear model. RESULTS: Facial tooth position (725 mum, CI 379-1072 mum, distal root of the third molar) and maxillary skeletal width (295 mum, CI 168-421 mum) differed significantly between force groups. Despite bone apposition at the facial aspects of the moved roots, bone dehiscences were developing and bone thickness was decreasing during facial tooth movement. Development of gingival recession was scarce and in cases with extreme facial tooth movement. No remarkable differences between force levels were found for any of the periodontal parameters. CONCLUSIONS: Facial tooth movement with conventional or low forces resulted in similar modelling of facial alveolar bone and gingiva.