Self-Ligated Versus Elastomeric Orthodontic Brackets: Quantitative Comparison of Plaque Bacteria

Objectives: A side effect of orthodontic appliances is increased retention of cariogenic bacteria, often leading to enamel demineralization and visible white-spot lesions on the facial surfaces of teeth. The objectives of this study were to compare the numbers and types of bacteria found in plaque surrounding two distinct orthodontic brackets, self-ligated versus elastomeric, using a split-mouth design.

Methods: Patients (males and females; ages 11-17) were bonded with a complementary mix of the self-ligated and elastomeric orthodontic brackets in opposite quadrants in upper (14 patients) and lower (12 patients) arches. Patients were recalled at 1 and 5 weeks after bonding for collection of plaque from standardized areas of the tooth surrounding the brackets. Plaque specimens were assayed for total bacterial number, total oral streptococci, and Streptococcus mutans number. Mean, standard error, and significance values (p; Student's t-test) were calculated.

Results: At one week post-bonding, the mean and standard error values for self-ligated versus elastomeric brackets were statistically lower for total bacteria (1.6 X 10⁶ + 4.79 X 10⁵ versus 5.29 X 10⁶ + 1.46 X 10⁶ bacteria, respectively; p=0.008) and for total oral streptococci (6.66 X 10⁵ + 2.23 X 10⁵ versus 2.52 X 10⁶ + 9.16 X 10⁵ streptococci, respectively; p=0.03). Similar statistical differences were identified at five weeks post-bonding between self-ligated and elastomeric brackets for both total bacteria and oral streptococci. Statistically-significant differences were also observed for total bacteria between the self-ligated and elastomeric brackets in the upper arch (p=0.01) with no statistically-significant differences in the lower arch (p=0.17).

Conclusions: The self-ligated appliances promote reduced retention of oral bacteria, including streptococci, at both one week and five weeks post-bonding. Statistically-significant differences comparing plaque bacteria collected from self-ligated and elastomeric appliances appear to hold for the upper arch, but not for the lower arch.