In a recent study published in the American Chemical Society (ACS) Nano, researchers reviewed nanoparticles (NPS) as a new generation of teeth whitening agents.
Dental aesthetics such as color are essential for patients; For example, a study found that 34% of adults in the United States are dissatisfied with the color of their teeth. A survey in the United Kingdom (UK) reported that more than 96% of respondents believed that cosmetic dentistry affects their self-confidence and psychosocial behavior.
Various methods of teeth whitening have been introduced, such as whitening toothpaste, exfoliation, and polishing. There are three ways to whiten teeth: at-home, in-office whitening, and over-the-counter whitening. All methods use carbamide peroxide and hydrogen peroxide (H2O2) as bleaching agents. A high concentration of H2O2 generates more free radicals which lead to teeth whitening.
NPS can stabilize bleaching agents and regulate their release in oral environments. Moreover, recent studies revealed that most NPs also exhibit teeth whitening effects. In this review, researchers discuss different perspectives on NP-based teeth whitening as next-generation solutions for whitening.
Teeth whitening procedures and their complications
The in-office whitening procedure, called chair-side whitening, is performed by a professional dentist with 15%-20% H2O2 up to three times for 15 to 20 minutes. The at-home method requires self-administration of treatment for three to eight hours for several weeks, under the supervision of a dentist. This method uses 3.5% - 6.5% H2O2 for overnight application or 7.5% if done during the day.
OTC methods can be done with bleaching toothpaste, dental floss, rinses, or a toothbrush, which is less than 3% H2O2. Moreover, modern teeth whitening products contain inactive ingredients that have specific functions in increasing the effectiveness of teeth whitening. These inactive ingredients can be thickening agents, stabilizers, preservatives, carriers, flavors, and activating agents.
Although the use of larger amounts of H2O2 results in an excellent whitening effect, overexposure in the amount and time may cause mouth burns. However, since dentists regulate the H2O2 concentration, adverse effects can be reduced.
NPS for teeth whitening
NPS has unique biological properties, unlike whitening agents, and has been used in various applications in prosthetic dentistry, implants, restorative dentistry, periodontal therapy, and oral cancer treatment. NPS also exhibits antibacterial, antifungal, and antiviral properties. However, few studies have used NPS for teeth whitening due to the belief that NPs may irreversibly damage teeth through gas whitening.
However, the use of NPS for teeth whitening has received a lot of attention recently, since some NPs have been found to enhance the chemical activity in non-invasive whitening. Gold NPs (AuNPs), zinc oxide (ZnO), titanium dioxide (TiO2), silica, and hydroxyapatite (HA) are the NPs currently used for teeth whitening.
Metal or metal oxide NPs such as AuNP, ZnO, TiO2, and silver NP (AgNP) are known for their antibacterial and anti-inflammatory properties. They have been used to prevent oral diseases in oral care products. NPs produce reactive oxygen species (ROS) such as monooxygenase, superoxide radicals, hydroxyl radicals, and H2O2 when bacteria are present in oral environments.
The type of ROS varies based on the NPs; For example, ZnO and AuNPs generate H2O2, while AgNPs form hydroxyl radicals. Therefore, it has been reported that AuNPs, ZnO and copper oxide (CuO) are suitable for bleaching.
Metals and Metal Oxide NPs
In one study, researchers showed that mice given 20 mg/kg of AuNPs for 90 days had minimal changes in biochemical and hematological parameters and that the differences were toxicologically nonsignificant. Another research group showed that the bleaching effect of H2O2 was significantly increased with AuNPs, although the toxicity of AuNPs during bleaching could not be excluded.
A research team showed that the ZnO-biomass carbon (BC) compound has an excellent whitening effect by using long wave light. Furthermore, levels of tooth color were improved, and no toxicity was detected in vitro and in vivo. In a study, researchers investigated the effect of light irradiation on bleaching using TiO2 NPs containing H2O2. They show that TiO2 NPs containing 3.5% H2O2 has the same bleaching effect as 35% HO, with the most substantial effect at 405 nm diode laser.
Ceramic materials such as NPs
Hyaluronic acid is a ceramic that forms the inorganic component of bone. Thus, HA NPs have significant advantages as they possess a strong affinity for demineralized surfaces and feature similar properties to enamel building blocks. Thus, these NPs can form the apatite layer that encapsulates the prismatic and prismatic enamels. HA NPs can help restore mineral density and transparency.
One study reported that the bleaching effect is amplified with increasing concentrations of HA NPs.
In a randomized controlled trial, researchers found that people who brushed their teeth with toothpastes containing HA NPs significantly improved tooth color. Besides, some reported that oral products containing HA NP were safe. Toothpaste containing hydrated silica has been shown to make teeth less yellow and whiter after brushing, while others have found excellent stain-removing and antifouling properties.
The authors explained the various NPs for teeth whitening. AuNPs, TiO2 and ZnO NPs can produce reactive oxygen species with bleaching and antibacterial effects, while HA can remineralize
To teeth besides whitening. They hypothesize that metals and nitrogenous metal oxides could have great potential as next-generation bleaching agents. However, many challenges remain for the application of NPs for teeth whitening, and the commercial use (of NPs) could advance in the future with increasing evidence.
Kim DH, Bae J, Heo JH, Park CH, Kim EB, Lee JH. (2022). Nanoparticles as Next-Generation Tooth-Whitening Agents: Progress and Perspectives. ACS Nano. doi: 10.1021/acsnano.2c01412 https://pubs.acs.org/doi/10.1021/acsnano.2c01412