Microbial growth on the surfaces of various orthodontic bonding cements.

An experimental technique was developed to examine the adhesion of a strain of Streptococcus mutans to the surface of discs of selected orthodontic bonding composites and a glass ionomer cement. Colonization by the bacterium was assessed by weight gain and scanning electron microscopy. Initial colonization occurred after about 3 days, and the specimens were usually completely covered by the fourth day. There were statistically significant differences between materials for weight gain, a strong correlation between weight gain and surface free energy of the materials measured as droplet contact angle (r = 0.9) and a moderate correlation between weight gain and surface roughness (r = 0.6).