New attachment through periodontal treatment and orthodontic intrusion.

The present study was performed to investigate the tissue reaction related to orthodontic intrusion of teeth with a reduced periodontium and further to evaluate the influence of oral hygiene on this reaction. In each of five Macaca fascicularis monkeys, periodontal tissue breakdown was induced around the premolars and the upper incisors by placing orthodontic elastic ligatures around the teeth. The breakdown procedure was continued until a minimum of four pockets could be measured on probing. Following removal of the elastics, a flap operation was performed. The pocket epithelium and granulation tissue were excised. During the surgical procedure, a notch was placed just above the bone. The teeth were divided postoperatively into four groups according to treatment: group 1 = flap operation, no oral hygiene program; group 2 = flap operation plus oral hygiene program three times per week; group 3 = flap operation plus intrusion, no oral hygiene program; and group 4 = flap operation plus intrusion plus oral hygiene. Groups 3 and 4 were subdivided into two observation periods. A total of 60 teeth corresponding to 120 approximate surfaces were studied. The animals were killed with perfusion; histologic sections were produced and stained alternatively with hematoxylin and eosin, and van Gieson's solution. The histologic analysis showed that new cementum formation and new collagen attachment were observed following the surgical procedure if the oral hygiene was maintained, but also demonstrated that the intrusion improved the quantity of new attachment if carried out under healthy conditions. New attachment was a consistent finding in group 4, but varied from 0.7 to 2.3 mm. In case of intrusion without oral hygiene, the results varied from moderate new attachment to an aggravation of the periodontal bone loss. On the basis of the results presented here, the combination of periodontal treatment and orthodontic intrusion seems to be a method by which improvement of the periodontal condition can be obtained, provided that both the biomechanical force system and the oral hygiene are kept under control.