A new non-invasive preventive measure in cariology: laser-based tooth coating. Investigation of tooth-protective, material science and laser technical aspects.

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According to the world health organization (WHO) currently 60-90% of school children worldwide still have dental caries. Most of the new caries lesions occur in fissures and pits of the first molars until the age of 12 years. Unfortunately, fluoride is less effective in these areas and sealing of these fissures with composite materials presents only limited effectiveness. Clinical studies show 30 to 55% failure rates after 5 years, mostly due to the poor adhesion between the filling material and the tooth surface. Additionally to the caries problem, there has been an increase, of another condition causing tooth substance loss, the dental erosion. This latter condition may cause extensive tooth destruction, which can be even worse when combined with mechanical factors (e.g. tooth-brushing), the abrasion. Also these destructive oral disorders are only mildly controlled by the currently available preventive measures (diet changes / fluoride) and strongly dependent on patient compliance. Thus, there is still a great demand for innovative methods which can protect these highly affected tooth surfaces from acid dissolution, related both to caries and erosion.Therefore the aim of this project is to test a new non-invasive tooth surface coating procedure for achieving an increased caries and erosion protection, on predilection tooth sites of patients at high risk for caries or exaggerated dental erosion. For this, a laser-based method will be tested, which allows the transformation of materials applied on the tooth surface into a ceramic protective layer. Through a fundamental understanding of the material modifications and the chemical and structural changes at the dental hard tissues during the laser irradiation should be possible to achieve a tight connection between the surface of the natural teeth and the ceramic coat. The major challenge within this study plan is, however the dichotomy between the high peak temperatures required for a successful transformation of the particulate material into a homogeneous coating and the very low heat stabilities of the tooth. At the pulp, for example, a temperature increase of 5,5 °C leads already to irreversible tissue damage.One of the approaches to solve the difficulties in the present project will be the use of a customized glass ceramic coating material that presents a significantly reduced melting temperature compared to a pure ceramic. Furthermore, the exact temporal and local controllability of the laser will allow for a fine adjusting of the laser-induced temperature-time-profile, so that tooth damage can be avoided.Finally, the obtained coatings will be systematically tested using clinically similar carious, erosive and mechanical challenges (in vitro and in situ) in order to investigate their clinical and preventive applicability.