Orthodontic adhesives induce human gingival fibroblast toxicity and inflammation

To test the null hypothesis that the resin base and the resin hybrid glass ionomer base adhesives do not cause inflammation after contacting primary human gingival fibroblasts in vitro.

The resin base and resin hybrid glass ionomer base adhesives were used to treat human gingival fibroblasts to evaluate the survival rate using MTT colorimetric assay to detect the level of cyclooxygenase-2 (COX-2) mRNA by reverse transcription polymerase chain reaction (RT-PCR) technique and COX-2 protein expression using Western blot analysis. The results were analyzed using one-way analysis of variance (ANOVA). Tests of differences of the treatments were analyzed using the Tukey test and a value of P < .05 was considered statistically significant.

The paste and primer of the resin base adhesive and the liquid of glass ionomer adhesive showed decreasing survival rates after 24 hours of treatment (P < .05). All orthodontic adhesives induced COX-2 protein expression in human gingival fibroblasts. The exposure of quiescent human gingival fibroblasts to adhesives resulted in the induction of COX-2 mRNA expression. The investigations of the time-dependent COX-2 mRNA expression in adhesive-treated human gingival fibroblasts revealed different patterns.

The hypothesis is rejected. For orthodontic patients with gingival inflammation, except for those with oral hygiene problems, the activation of COX-2 expression by orthodontic adhesive may be one of the potential mechanisms.