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

根据世界卫生组织（WHO）的数据，目前全球60-90%的学龄儿童仍然患有龋齿。大多数新的龋损发生在第一磨牙的裂隙和小坑中，直到12岁。不幸的是，氟化物在这些区域的效果较差，用复合材料密封这些裂缝的效果有限。临床研究显示，5年后的失败率为30%至55%，主要是由于填充材料与牙齿表面之间的粘附性差。除了龋齿问题之外，另一种引起牙齿物质损失的情况，即牙齿侵蚀也有所增加。后一种情况可能会导致广泛的牙齿破坏，当与机械因素（例如刷牙），磨损相结合时可能会更糟。此外，这些破坏性口腔疾病仅通过目前可用的预防措施（饮食变化/氟化物）得到轻度控制，并且严重依赖于患者的依从性。因此，仍然有一个很大的需求，创新的方法，可以保护这些高度受影响的牙齿表面从酸溶解，相关的龋齿和侵蚀。因此，本项目的目的是测试一种新的非侵入性的牙齿表面涂层程序，以实现增加龋齿和侵蚀保护，在龋齿或夸大的牙齿侵蚀的高风险患者的偏好牙齿部位。为此，将测试一种基于激光的方法，该方法允许将施加在牙齿表面上的材料转化为陶瓷保护层。 通过对激光照射过程中牙齿硬组织的材料改性和化学及结构变化的基本理解，应该可以实现天然牙齿表面与陶瓷涂层之间的紧密连接。然而，本研究计划中的主要挑战是颗粒材料成功转化为均匀涂层所需的高峰温度与牙齿极低的热稳定性之间的二分法。例如，在牙髓处，温度升高5.5 °C就已经导致不可逆的组织损伤。解决本项目困难的方法之一是使用定制的玻璃陶瓷涂层材料，与纯陶瓷相比，该材料的熔化温度显著降低。此外，激光的精确时间和局部可控性将允许对激光诱导的温度-时间曲线进行微调，从而避免牙齿损伤。最后，将使用临床上类似的龋齿、侵蚀和机械挑战（体外和原位）对所获得的涂层进行系统测试，以研究其临床和预防适用性。

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.