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Abstract:

Tooth-restoration materials need to withstand chewing forces and diverse forms of chemical and thermal stresses in the challenging oral environment. Dental restorative materials that combine the needed physico-mechanical strength and degradation resistance with 'therapeutic' potential, remain however to be developed. Nevertheless, 'bioactive' materials that would enable diseased tooth tissue to be healed in situ rather than that the dentist needs to replace it with an artificial restorative material, are highly desirable. Techniques to re-mineralize tooth enamel have well been adopted in clinical practice. However, in contrast to enamel, the process of dentin re-mineralization is more complex. Residual hydroxyapatite (HAp) crystals that can act as existing 'seed' crystals and thus re-mineralization initiation sites, are absent in dentinal carious lesions. Thus, the formation of organized nanocrystals is crucial for successful dentin remineralization. In fact, the first paper describing re-mineralization of fully demineralized dentin only very recently appeared. Besides inorganic minerals (mainly HAp), dentin includes an organic matrix that consists of Type-I collagen and non-collagenous proteins (NCP's), some of which may even inhibit the re-mineralization process. 'Biomimetic re-mineralization' imitates the natural process of mineralization; it involves a technique to grow HAp in demineralized dentin in a manner, shape and with mechanical properties similar to that of the natural mineral fraction of the host dentin substrate. More specifically, biomimetic re-mineralization has been described achievable by phosphorylation of Type-I collagen using phosphate solutions, followed by exposure to calcium in a suitable medium. The collagen matrix of demineralized dentin hereby serves as scaffold. Recent laboratory studies have indeed shown that it is possible to re-mineralize demineralized dentin surfaces. Clinically, biomimetic re-mineralization is especially thought to be very useful to prevent further progress of active dentinal caries. Obviously, the bacterial infected tissue remains to be removed, but the underlying bacteria-free and demineralized caries-affected dentin could be transformed into a mineral barrier that protects the dental pulp underneath. If this non-infected deep caries can be 'healed' (=re-mineralized) in situ, it should not necessarily be removed anymore by bur, thereby reducing the possibility of pulp exposure. From a clinical standpoint, it would indeed be advantageous to preserve the softened demineralized dentin, if it can be re-mineralized to a sufficient degree and so also restore the mechanical strength of the tooth needed to function in the mouth. Another important indication of biomimetic re-mineralization agents is to repair accidental (iatrogenic) pulp capping or (tiny) exposures of the pulp in an attempt to maintain the pulp vitality and thus to avoid root-canal treatment. The objective is to stimulate exposed pulp tissue to produce new dentin and so to seal the pulp exposure by dentin-bridge formation. Therefore, the main objective of this exploratory research is to develop a clinically applicable technique to repair demineralized dentin lesions and exposed pulps.