Effects of dental acid etchants in oral epithelial cells

Abstract

Phosphoric acid (P.A.; 37%) can induce necrosis on the oral mucosa and cause the ulceration of periodontal tissue. However, most studies reported are clinical case studies, with few basic science studies on oral epithelial cells. Our study aimed to investigate the effects of dental acid etchants on oral epithelial cells. After treatment with dental acid etchants for the indicated periods (0 second, 10 seconds, 30 seconds, 1 minute, and 5 minutes), cell damage, including vacuoles, pyknosis, and karyolysis, was observed by hematoxylin-eosin staining. The percentage of cell damage significantly increased after 10 seconds of etchant application. Furthermore, as the etchantapplied time increased from 10 seconds, 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay results showed that cell viability was significantly reduced. Dental acid etchants were diluted with distilled water at ratios of 1:2 (18.5% P.A.) to 1:10 (3.7% P.A.). After the application of 1:5 (7.4% P.A.) diluted etchants, cells were enlarged, with some cells showing nuclear injury, including pyknosis. When treated with 1:2 (18.5% P.A.) diluted etchants, karyorrhexis and vacuoles were observed. The percentage of damaged cells significantly increased after the application of 1:2 (18.5% P.A.) diluted etchants. Moreover, cell viability significantly decreased in cells treated with 1:5 (7.4% P.A.) and 1:2 (18.5% P.A.) diluted etchants. This study examined the effects of dental acid etchants on oral epithelial cells as a basic experimental study in vitro and demonstrated the risks of dental acid etchants. Therefore, dentists and dental hygienists should pay strict attention to the handling of acid etchants during restoration and orthodontic treatments.

Cytotoxicity of V-Prep Versus Phosphoric Acid Etchant on Oral Gingival Fibroblasts

“…The results of this study regarding the acid etchant application at different concentrations and durations are in complete accordance with similar studies [17,23,24]. Kim et al found that the acid etchant can damage the vacuoles and the nucleus of the cells when it is applied for 10 s or more at a concentration of 18.5% (referring to 1:2 in our study).…”

“…Clinical research and studies have examined the effects of dental acid etchants on human tissues [17]. Necrosis and chemical burns were reported on the gingiva, the facial skin and the tongue [19].…”

“…Kim et al found that the acid etchant can damage the vacuoles and the nucleus of the cells when it is applied for 10 s or more at a concentration of 18.5% (referring to 1:2 in our study). Accordingly, they also found that the cell viability was significantly reduced even when the acid etchant was applied for less than 30 s at a concentration of 1:10 [17]. Frob et al found that both self-etchant adhesive and etchant-rinse adhesive methods are toxic on the normal human gingival fibroblasts [23].…”

“…Gingival fibroblasts are the first surrounding tissue to become in contact with the diluted etchant in different concentrations. Studies comparing the effect of the acid etchant on gingival fibroblasts tested three concentrations of contact, 1:1 (undiluted), 1:2 and 1:10 [17]. The toxicology and the damage caused on the oral cells have not been tested for V-prep.…”

Impact of different acid concentrations on bond strength of metallic brackets and enamel damage – an in vitro study.

“…Another reason to reduce the acid concentrations used during orthodontic etching is the problems that acid can cause on oral mucosa. It was reported that inadequate rinsing of dental acid etchants or remaining dental acid etchants can cause problems, including chemical burning, irritation and inflammation, intra and extra orally 6 .…”