Horseradish peroxidase interacts with the cell wall peptidoglycans on oral bacteria.

Salivary peroxidase and myeloperoxidase are known to display antibacterial activity against oral microbes, and previous indications have pointed to the possibility that horseradish peroxidase (HRP) adsorbs onto the membrane of the major oral streptococci, Streptococcus mutans and Streptococcus sanguinis (S. sanguinis). However, the mechanism of interaction between HRP and the bacterial cell wall component is unclear. Dental plaques containing salivary glycoproteins and extracellular microbial products are visualized with 'dental plaque disclosing agent', and are controlled within dental therapy. However, current 'dental plaque disclosing agents' are difficult to evaluate with just dental plaques, since they stain and disclose not only dental plaques but also pellicle formed with salivary glycoproteins on a tooth surface. In this present study, we have demonstrated that HRP interacted with the cell wall component of the major gram-positive bacterial peptidoglycan, but not the major cell wall component of gram-negative bacteria lipopolysaccharide. Furthermore, we observed that the adsorbed HRP labeled with fluorescence was detected on the major oral gram-positive strains S. sanguinis and Streptococcus salivarius (S. salivarius), but not on a gram-negative strain, Escherichia coli (E. coli). Furthermore, we have demonstrated that the combination of HRP and chromogenic substrate clearly disclosed the dental plaques and the biofilm developed by S. sanguinis, S. salivarius and the major gram-postive bacteria Lactobacillus casei on tooth surfaces, and slightly disclosed the biofilm by E. coli. The combination of HRP and chromogenic substrate did not stain either the dental pellicle with the salivary glycoprotein mucin, or naked tooth surfaces. These results have suggested the possibility that the adsorption activity of HRP not only contributes to the evaluation of dental plaque, but that enzymatic activity of HRP may also contribute to improve dental hygiene.

Reinforcement of bond strength of self-etching orthodontic adhesive.

OBJECTIVE: To determine the reinforcement of bond strength of a self-etching system by applying a pretreatment agent. MATERIALS AND METHODS: Sixty extracted human premolars were used in this study. The enamel surfaces were treated with four pretreatment agents-phosphoric acid, polyacrylic acid, citric acid, and ammonium hexafluorosilicate (SiF)-and were examined under a scanning electron microscope. Afterward, orthodontic brackets were bonded with a self-etching adhesive system (n  =  10 for each agent), and shear bond strength was measured through a debonding process. The adhesive remnant index (ARI) was also assessed. RESULTS: Enamel surfaces treated with polyacrylic acid seemed almost the same as intact enamel. Treatment with SiF induced slight shallow depressions compared with the intact enamel. On the other hand, enamel surfaces treated with citric acid and phosphoric acid showed severe etching patterns. All pretreatments increased the bond strength, but SiF-treated specimens revealed the greatest strength (12.201 ± 1.048 MPa), followed by polyacrylic acid (12.030 ± 2.103 MPa). The control group with no pretreatment showed the least strength (9.078 ± 1.678 MPa). All pretreatments increased ARI score compared with the control group. CONCLUSIONS: Surface conditioning before bracket adhesion could reinforce the bond strength of the self-etching adhesive system, resulting in a more reliable bonding system.

Antibacterial activity of composite resin with glass-ionomer filler particles.

The purpose of this study was to examine the antibacterial activity of composite resin with glass-ionomer filler particles versus that of contemporary commercial composite resins. Three composite resins were used: Beautifil II (containing S-PRG filler), Clearfil AP-X, and Filtek Z250. Resin blocks were bonded to maxillary first molars, and plaque accumulation on the resin block surface was examined after 8 hours. For the antibacterial test, the number of Streptococcus mutans in contact with the composite resin blocks after incubation for 12 hours was determined, and adherence of radiolabeled bacteria was evaluated. Less dental plaque was formed on Beautifil II resin block as compared to the other two materials. Antibacterial test revealed that there were no significant differences in the number of Streptococcus mutans among the three composite resins. However, the adherence of radiolabeled bacteria to the saliva-treated resin surface was significantly (p<0.01) lower in Beautifil II than in the other two materials. These results suggested that Beautifil II could reduce dental plaque formation and bacterial adherence, leading to prevention of secondary caries.

Influence of different self-etching primers on the bond strength of orthodontic lingual buttons.

The aim of this study was to evaluate the influence of six self-etching primers (SEPs) on the shear/peel bond strength (SPBS) of orthodontic lingual buttons. A total of 150 extracted human premolars were randomly divided into six equal groups. In all groups, the lingual buttons were bonded with BeautyOrtho Bond and the enamel was conditioned with the following-group I (Control): Primers A & B; group II: Transbond Plus SEP; group III: Clearfil Mega Bond FA™; group IV: AdheSE; group V: Peak SE & Peak LC Bond; and group VI: Bond Force. The teeth were stored at 37°C for 24 hours and the SPBS was tested (0.5 mm/minute). The results were calculated in mega pascals (MPa) and statistically analysed [mean, standard deviation, Scheffè, analysis of variance (P < 0.05)]. The adhesive remnant index (ARI) was also evaluated and statistically analysed with a chi-square test. All groups demonstrated higher SPBS than the force suggested as necessary to accomplish orthodontic tooth movement, except group IV (7.7 ± 1.7 MPa), which showed a significantly lower value than groups I (10.7 ± 2.4 MPa), II (11.3 ± 3.1 MPa), and V (10.9 ± 2.8 MPa). The values of groups III (9.9 ± 1.6 MPa) and VI (10.5 ± 1.6 MPa) were comparable with those of groups I and V. Significant differences (P < 0.05) were found among the groups in ARI scores. The SPBS values of all groups could be clinically acceptable and lingual buttons might be successfully bonded with any of these SEPs except AdheSE since that conditioner significantly influenced bond strength. As the SPBS was lower in all groups than the value at which enamel fractures have been found, a sound enamel surface might be left after removal of lingual buttons.