Past concepts that the pulp does not become infected until an actual cariou
s exposure takes place have been challenged. The antibacterial effects of t
he dentin bonding systems Single Bond, Prime&Bond NT, and Excite were evalu
ated using the bacteria Streptococcus mutans ATCC 25175, Streptococcus inte
rmedius, Lactobacillus acidophilus, Prevotella oris, Prevotella bivia, Prev
otella denticola, Porphyromonas gingivalis, Porphyromonas endodontalis, and
Clostridium ramosum with a disk diffusion method. Chlorhexidine (0.2%) was
used as a positive control. After incubation zones of inhibited bacterial
growth were measured. Prime&Bond NT showed growth inhibition for all bacter
ial strains. Lactobacillus acidophilus and Streptococcus mutans were remark
ably resistant to Single Bond, whereas EX produced no inhibitory effect on
Porphyromonas endodontalis, although the adhesive produced the maximum halo
inhibition to Streptococcus mutans (15 +/- 1 mm), showing an antibacterial
effect closest to chlorhexidine. The variety of results obtained in this s
tudy suggest that antibacterial properties of current dentin adhesives may
depend on components that are originally incorporated to promote adhesion.