Histopathology of artificial periodontal defects in beagle dogs before and after ligature removal

The aim of the resent study was to investigate the histopathological characteristics of artificial periodontal defects before and after removal of ligatures. The defects were created in 12 young adult beagle dogs using cotton floss ligatures. The supracrestal dentogingival fibres were dissected around 6 lower premolars (₂P₂, ₃P₃, and ₄P₄) after which closely adapted copper bands were cemented to the teeth. After 3 weeks these copper bands were replaced by subgingival cotton floss ligatures which were left in place for a further 11 weeks. The placement of ligatures around the different teeth and their removal prior to sacrifice was scheduled to provide histological observations of the periodontal defects both with ligatures in situ, and 1 day and 1, 3, 7, 15, or 31 weeks after their removal.
Defects with ligatures in situ showed histopathological characteristics of advanced chronic periodontitis. Removal of the ligatures and the subsequent production of a notch (to mark the bottom of the pocket) resulted initially in an exacerbation of the inflammatory process but 3 weeks after ligature removal, a distinct decrease in size of the infiltrated connective tissue (I. C. T.) could be observed especially in the deeper part of the lesion. The tissues of the periodontium showed signs of repair whack became more pronounced with time. There was no indication that the lesion had become progressive in the remaining period of 7–31 weeks after ligature removal.
It is concluded that the maintenance of the established lesion is dependent on the persistence of subgingival plaque containing ligatures.