The conventional light source used for tooth bleaching has the potential to cause thermal damage, and the actual role of the light source is doubtful. In this study, we evaluated bleaching efficacy, temperature, and morphological safety after tooth bleaching with nonthermal atmospheric pressure plasma. Tooth bleaching combined with plasma had improved efficacy in providing a higher level of brightness. The temperature of the pulp chamber was maintained around 37°C, indicating that the plasma does not cause any thermal damage. The morphological results of tooth bleaching with plasma did not affect mineral composition under scanning electron microscopy (SEM) observations. On the basis of these results, the application of plasma and low concentration of 15% carbamide peroxide (CP) has a high capability for effective tooth bleaching. It can be documented that plasma is a safe energe source, which has no deleterious effects on the tooth surface.
The demand for an improved appearance and a whiter smile has made tooth bleaching a very popular dental procedure [
Clinical bleaching agents use a high concentration of hydrogen peroxide (HP; H2O2) or carbamide peroxide (CP; CH6N2O3), both of which provide oxidative power [
However, tooth bleaching with a high concentration of HP bleaching agent and a high-intensity light source has the potential to cause adverse effects on the surface enamel [
Plasma is the fourth state of matter, the others being solid, liquid, and gas. Plasma forms when gas is ionized. It has the ability to conduct electricity and respond to electromagnetic fields, because plasma contains many radicals, a strong electric field, and charged particles. Since 2000, nonthermal atmospheric pressure plasma sources have been used for biomedical applications such as bacterial sterilization, cancer treatment, wound healing, and dental applications [
Figures
The application of nonthermal atmospheric pressure plasma for tooth bleaching with low concentrations of 15% CP. (a) The plasma device and (b) the process during bleaching treatment.
Twenty freshly extracted intact human teeth were stored in 0.4% sodium azide solution at room temperature until required. Any teeth with signs of fracture, dental caries, or structural anomalies were discarded. Before experimental use, all teeth were removed with a soft-tissue ultrasonic scaler and polished in a dental rubber cup with water or pumice slurry prophylaxis. The roots were cut with water-cooling using a diamond saw (Struers Minitom, Copenhagen, Denmark) approximately 0.5 mm below the cement-enamel junction. The crown was cut in half longitudinally and cut surfaces were coated with two layers of nail varnish. The study was approved by the Research Ethics Committee of the Pusan National University Yangsan Hospital, Yangsan, Republic of Korea (Approval number 04-2012-010).
Before the tooth bleaching, the buccal surface of each tooth was photographed using a digital-imaging system provided by a stereomicroscope (SZ-CTV, Olympus, Tokyo, Japan) at 10x magnification. The teeth were randomly assigned to two groups (
The tooth images were captured with a 10x magnification digital-imaging system consisting of a stereomicroscope connected to a camera (Pixel Link PL-B686 CU, Canada) at 10 min intervals. The images were loaded onto a computer through Image-Pro Plus 5.1 software (Media Cybernetics Inc., Washington, DC, USA). The overall color changes (
The temperature increase in each tooth was measured independently from the tooth bleaching experiments using a fiber-optic temperature measurement system (FTI-10 fiber-optic signal conditioner, FOT-L-SD fiber-optic temperature sensor; FISO Technologies Inc., Quebec, Canada). The fiber-optic temperature sensor was located within the pulp chamber. The distance between the emitting tip of the plasma source and the fiber-optic temperature sensor was set at 1 cm during “plasma-on” for 30 min at room temperature (25°C).
Immediately after drying, the images were then assessed using scanning electron microscopy (SEM; S3500N, Hitachi Co., Tokyo, Japan) at 15 kV accelerating voltage. The images were then assessed at 2,000x magnification.
Statistical analysis was performed with the SPSS computer program (SPSS Inc., Version 18.0, Chicago, IL, USA). Student’s
Today’s bleaching systems are the result of efforts to increase patient benefits in terms of better bleaching efficacy and ease of use [
The mean
Observation times | Bleaching agents |
|
Mean |
|
|
---|---|---|---|---|---|
Plasma | Without plasma | ||||
10 min | 15% CP | 20 |
|
|
0.000* |
20 min | 15% CP | 20 |
|
|
0.000* |
30 min | 15% CP | 20 |
|
|
0.000* |
CP: carbamide peroxide,
*
Many studies have demonstrated thermal damage induced by light sources. It is also known that temperature increases in the pulp chamber may be a serious threat to the vitality of the pulp [
Measurement of the dental cavity temperature during the bleaching treatment.
In most cases, SEM studies were used to analyze the morphological changes of the tooth surface at high resolution and magnification [
SEM photomicrographs of enamel surface morphology for each group at 2000x magnification.
The combination of nonthermal atmospheric pressure plasma with 15% CP has a greater capability for effective tooth bleaching than conventional light sources. The tooth surface temperature was maintained around 37°C, indicating that the plasma does not cause any thermal damage to the tooth. The application of plasma did not cause any structural changes to the bleached surface. Nonthermal atmospheric pressure plasma has been proven to have no deleterious effect on bleached enamel. Therefore, tooth bleaching techniques using plasma represent a method of cosmetic dentistry with many practical applications in the future.
Scanning electron microscopy
Carbamide peroxide.
The authors declare that there is no conflict of interests regarding the publication of this paper.
Jin Woo Hong and Gyoo Cheon Kim contributed equally to this work.
This work was supported by a 2-Year Research Grant of Pusan National University.