Effects on tooth movement of force delivery from nickel-titanium archwires

The aim of this project was to determine the in vivo effects of tooth movem ent with nickel-titanium archwires on the periodontium during the early sta ges of orthodontic treatment. The extent of tooth movement, severity of gin gival inflammation, pocket probing depth, gingival crevicular fluid (GCF) f low and the amount of the chondroitin sulphate (CS) glycosaminoglycan (GAG) component of the GCF of one maxillary canine in each of 33 patients treate d with a pre-adjusted appliance were measured before and at four stages dur ing the first 22 weeks of treatment. The methods involved the use of a refl ex metro-graph to determine the type of tooth movement and electrophoresis to quantitate the CS in the GCF. It was found that GCF flow increased after 4 weeks of tooth movement wherea s the increase in the amount of CS in the GCF, which is taken to be indicat ive of periodontal tissue turnover, occurred at the later stage of 10 weeks . Teeth which showed the greatest amount of tooth movement continued to exp ress large amounts of CS in large volumes of GCF until 22 weeks, whilst the CS levels in those teeth moving to a smaller extent declined. These data suggest that nickel-titanium archwires may produce a super-elast ic plateau effect in vivo on canine teeth, which are initially displaced fr om the arch such that large amounts of tooth movement occur in the first 22 weeks of treatment.