The Meso-Porous Ceramics Research Group of Ceramics Research Institute (CRI), National Institute of Advanced Industrial Science and Technology (AIST), one of independent administrative institutions, succeeded in developing new denture cleaner based on photo-catalyst in collaboration with Nissin Dental Products, Inc.

The newly developed cleaning agent has cleaning power drastically enhanced owing to the photo-catalytic effects, allowing to remove smell, scale and tar in a simple and safe manner, with additional merit of antibacterial action, eliminating some of problems inherent to commercially available detergents. Moreover, the cleaner does not affect dental materials such as denture itself and metal clasps.

The cleaner has already been commercialized and will be put on the market in a few days via Morita Corporation.

Tough stains accumulated on a denture in the course of every day use cannot be removed easily with existing denture cleaner. Titanium oxide (TiO₂) has been known to be stable and have photo-catalytic effect with associated actions of deodorizing, stain-removing, water-cleaning, germicidal and air clean-up. Dr. Toru Nonami, leader of the Meso-Porous Ceramics Research Group, CRI, AIST has been engaged in R&D works to apply TiO₂ to denture cleaner in collaboration with Nissin Dental Products, Inc.

For making TiO₂ photo-catalyst fully effective, irradiation with near-ultraviolet rays is needed using a special lighting device (black light lamp), which is hardly available for household use. The denture cleaner for everyday use is requested to be as user-friendly as existing cleaner, and to be resistant to stain accumulation, making clag tougher despite daily cleansing efforts. In order to overcome these problems, R&D works have been initiated aiming at the application of TiO₂ photo-catalyst.

The cleaning capability was evaluated by the rate of bleaching methylene blue added to the cleaner at a concentration of 10 ppm. Under illumination with black light, the solution with TiO₂ was not so effective, but a certain treatment accelerated bleaching, decolorizing methylene blue in 5 minutes or so. On the basis of these findings, it has been intended to improve the performance of denture cleaner.

A piece of model test paper with tobacco tar, one of persistent stains for denture, was immersed in a cleaner solution, irradiated with black light and ΔL value was determined before and after the immersion to assess the cleaning effect. The effect varied for different light sources: while the sunlight at the window was effective to some extent, the use of black light enhanced the cleaning power markedly.

In this way, it has been demonstrated that TiO₂ photo-catalyst activated the cleaning ingredient resulting in more pronounced cleansing. To the questionnaire after the trial use of sample cleaner, many of users returned favorable comments in comparison to cleaner being currently used: "Stains were removed effectively", "Denture was deodorized restoring nice breath" and so on. Encouraged by these results, the development of new denture cleaner with excellent cleaning effect based on photo-catalyst was brought to a success.

The developed denture cleaner is characterized by the following merits;
(1) Persistent stains are effectively removed and bad smell of denture is eliminated.
(2) Viscous covering of denture is cleaned efficiently, and anti-bacterial effect is exerted.
(3) Cleansing denture without leaving dark stain on metal parts.

Cleaning effects under illumination with different light sources