Effects of Cold-Light Bleaching on Enamel Surface and Adhesion of Streptococcus mutans.

Bo Zhang,Ling Zou,Xuedong Zhou,Mingyun Li,Lei Cheng,Shiyu Liu,Sibei Huo,Romeo Patini

doi:10.1155/2021/3766641

Abstract

Tooth bleaching is becoming increasingly popular among patients with tooth staining, but the safety of bleaching agents on tooth structure has been questioned. Primarily thriving on the biofilm formation on enamel surface, Streptococcus mutans has been recognized as a major cariogenic bacterial species. The present study is aimed at investigating how cold-light bleaching would change enamel roughness and adhesion of Streptococcus mutans. Human premolars were divided into 72 enamel slices and allocated into 3 groups: (1) control, (2) cold-light bleaching with 35% hydrogen peroxide (Beyond™), and (3) 35% hydrogen peroxide (Beyond™) alone. Biofilms of Streptococcus mutans were cultivated on enamel slices in 5% CO2 (v/v) at 37°C for 1 day or 3 days. Enamel surfaces and biofilms were observed using scanning electron microscope (SEM). Atomic force microscopy (AFM) was applied to quantify the roughness of enamel surface, and the amounts of biofilms were measured by optical density of scattered biofilm and confocal laser scanning microscopy (CLSM). Cold-light bleaching significantly increased (p < 0.05) surface roughness of enamel compared to controls, but significantly inhibited (p < 0.05) adhesion of Streptococcus mutans on enamel in the bacterial cultures of both 1 day and 3 days. In conclusion, cold-light bleaching could roughen enamel surface but inhibit Streptococcus mutans adhesion at the preliminary stage after the bleaching treatment.

Highlights

Tooth bleaching has enjoyed great popularity among patients suffering from intrinsic and extrinsic tooth staining
We combined the analyses of scanning electron microscope (SEM) and Atomic force microscopy (AFM) to investigate morphological alterations of enamel surfaces caused by bleaching procedure
In the cold-light bleaching (CLB) group and 35% hydrogen peroxide (HP) group, enamel surface morphology became rougher with more pittings in images of SEM (Figure 1) and 3D images of AFM (Figures 2(a)–2(c))

Summary

Introduction

Tooth bleaching has enjoyed great popularity among patients suffering from intrinsic and extrinsic tooth staining. It can efficiently improve the shade of dental fluorosis, tetracycline pigmentation teeth, and pulpless tooth [1]. CP, which is rapidly decomposed of HP and urea after applied on teeth, shares similar bleaching mechanism with. Urea from CP can degrade organic matrix in enamel, facilitating the diffusion of bleaching agents through enamel to reach the dentino-enamel junction [4, 5]. The efficacy is based on the application of highconcentrated bleaching agents combined with the activation of special blue light (wavelength between 480 nm and 520 nm). The cold-light lamp is equipped with filter to exclude the harmful infrared (wavelength λ > 750 nm) and ultraviolet (λ < 380 nm) to reduce the risk of thermal pulp

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Conclusion