Ligature wires and elastomeric rings: two methods of ligation, and their association with microbial colonization of Streptococcus mutans and lactobacilli.

Twelve orthodontic patients undergoing treatment with fixed appliances took part in the present study. In all patients elastomeric rings were used for ligation on one side of the dental arch midline, whereas steel wires were used on the opposite side. The number of micro-organisms in samples of plaque, taken from the labial surface of the upper lateral incisors, was recorded on five occasions during treatment. In samples of saliva, the numbers of Streptococcus mutans and lactobacilli were recorded on the same occasions. This registration was also made on two occasions before insertion of the fixed appliance, and 6 weeks after the period of active treatment. The results showed that, in the majority of patients, the incisor which was attached to the arch-wire with an elastomeric ring, exhibited a greater number of micro-organisms in the plaque than the incisor ligated with steel wire. Following insertion of fixed appliances the number of S. mutans and lactobacilli in saliva increased significantly. Variations in the number of micro-organisms in the saliva during active treatment were not reflected in any relative increase or decrease in microbial colonization on either steel ligatures or elastomeric rings. The use of retainers after active treatment was not associated with increased numbers of micro-organisms in the saliva.