Objectives: The purpose was to investigate the effect of saliva/biofilm contamination on bond strength of an orthodontic self-etching primer (SEP)/adhesive system. Methods: We mounted 120 sections of deciduous bovine enamel in single-plane lap shear bond strength holders. These holders ensure that the load on the specimen is parallel to the surface of the enamel and better confine the fracture path to the bonded interface. Prior to applying an orthodontic cement (Transbond XT; 3M Unitek) to the enamel, groups of 30 randomly selected SEP-coated (Transbond Plus Self Etching Primer, 3M Unitek) enamel sections received either 1) no saliva (control); 2) saliva that was left wet; 3) saliva that was allowed to evaporate; or 4) saliva followed by rinsing with water and drying with compressed air. Using a mechanical testing machine, we fractured the specimens at 0.5 mm/min., recorded the load at fracture, and calculated the bond strength (MPa). Results: Examination of the fractured bonds a 63X revealed that nearly all the specimens fractured nearly parallel to the enamel surface. The mean bond strengths (MPa) were: Grp. 1. 24.8 ± 8.3; Grp. 2. 16.7 ± 8.3; Grp. 3. 16.9 ± 9.9; and Grp. 4. 21.0 ± 7.7. ANOVA showed that at least one treatment had a significant affect on bond strength (F = 5.93; p < 0.0001). Tukey HSD test ranked the groups, in descending order: 1, 4, 3, 2. Mean bond strengths for groups 2, 3, and 4 were not significantly different from one another and groups 2 and 3 were significantly weaker than the uncontaminated controls in group 1 (p < 0.05). Conclusions: Neither drying the saliva nor rinsing and drying the saliva restored the enamel bond strength to that of uncontaminated specimens. Even the saliva-contaminated specimens had enamel bond strengths that may be sufficient for retention of orthodontic brackets.

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