Real-Time Photocatalytic Measurement of Dental Materials in an Open System

Abstract

It is common to encounter discrepancies between in vitro and in vivo studies, particularly when assessing the antibiofilm efficacy of dental materials. Typically, dental materials are tested in a closed system where fresh nutrients are not replenished, the test conditions are static, and the same planktonic bacteria persist. However, real environments are characterized by the continuous supply of fresh nutrients, dynamic saliva flow, and the periodic removal of planktonic bacteria through swallowing. To address these differences, we used an open system approach using microfluidic chips that simulate the nutrient and fluid flow conditions of the mouth. This setup enables the spatiotemporal development of biofilms, facilitates real-time observation, and provides deeper insights into the biofilm formation and removal processes. Photocatalytic dental materials are particularly suitable for use with microfluidic chips, as these devices allow real-time tracking of biofilm dynamics, both with and without light exposure. Nitrogen-doped titanium dioxide effectively produces reactive oxygen species (ROS) under visible light conditions, even when embedded in a resin matrix. These ROS have been shown to inhibit Enterococcus faecalis biofilms. The evaluation of the photocatalytic effects of dental materials using microfluidic chips showed that both new and established biofilms were disrupted by ROS production. ROS weakens the interface between the biofilm and dental material, allowing the biofilm mass to be removed by fluid flow. Furthermore, the open system provided by microfluidic chips demonstrated higher accuracy in evaluating antibiofilm efficiency than the conventional system did. Thus, the developed microfluidic chip is a novel and promising tool for assessing antibiofilm properties, with potential applications in various fields.