The aim of the planned in-vivo trial is to investigate the effectiveness of the the caries infiltration technique for the repression of approximal caries progression. .

Within the framework of this investigation it is intended that the hypothesis be substantiated that carious cavities, which have been treated with the caries infiltration technique, exhibit significantly reduced radiological progression than those cavities that have been treated using standard treatments.

Modern dentistry, which is focused more towards preventive and minimally invasive treatment, attempts - with the aid of fluoride therapies and improved oral hygiene - to prevent the onset and progression of carious lesions as much as possible.

Even today, approximal lesions pose a particular problem to the treating dentist. A primary reason for this is the difficulty accessing the localized area of the carious cavity. Treating this area usually requires invasive treatment, in which healthy tooth structure must be removed. Furthermore, it is possible that the filling material may deteriorate as a result of the aging process, meaning that the restoration will require replacement at some point in the future. In order to prevent this, the development of a treatment oriented towards prevention and minimal invasion is key.

For a number of years there has been an option to seal pits and fissures on the occlusal surfaces, which is assessed in the literature as being highly efficacious and effective (Splieth et al. 2010, Ahovuo-Saloranta et al. 2008, Griffin et al. 2008). It constitutes a vital component of the caries prevention approach especially in the event of an increased risk of caries (Hiiri et al. 2010). In recent years there has been an attempt to transfer this treatment concept to applications in the approximal area, in order to prevent unnecessary substance ablation. A fissure sealing resin and a dental adhesive were used for the first time in an attempt at creating a surface diffusion barrier (Gomez et al. 2008, Gomez et al. 2005, Paris et al. 2006, Martignon et al. 2006, Robinson et al. 2001). Coating the tooth surface in the approximal area with various plastic foils after tooth separation opened up a whole new treatment approach for dealing with these carious lesions (Alkilzy et al. 2010, 2009).

The caries infiltration technique constitutes an additional new treatment concept. Here, the surface alone is not exclusively coated but a diffusion barrier is instead created inside the cavity itself, through the penetration of the "infiltrant" into the carious lesion (Paris et al. 2010, Meyer-Lueckel et al. 2010, 2009, 2008, Phark et al. 2009). In current studies, it has been possible to demonstrate inhibition of the progression of carious lesions with the infiltration technique, both in bovine teeth in situ and in artificially generated carious lesions in human teeth in vitro (Paris et al. 2010).

The development of the infiltration technique started back in the 1970's with the first low-viscosity plastic materials. However, these were never put into clinical application due to their toxicity (Robinson et al.1976). During their course of development, adhesive systems were employed for sealing carious lesions (Donly et al. 1992, Garcia-Godoy et al. 1997). These also exhibit a caries-inhibiting effect. However, it has only been possible to determine limited penetration depths. The reason for this is the surface morphology of the carious cavity, with a very limited pore volume on the surface, and the characteristics of the adhesive itself (Paris et al. 2007). In order to facilitate removal of the limiting surface layer, a hydrochloric acid gel was used for the infiltration technique in place of orthophosphoric acid gel for the adhesive technology. Using this conditioner it was possible to guarantee better penetration of the materials up to a depth of 58 µm due to an erosive removal of the surface layer (Meyer-Lueckel et al. 2007, Paris et al. 2007, 2009). In order to better utilize the capillary effect in the altered surface and to thereby increase the penetration depth of the material, monomer mixtures were developed with a high penetration coefficient. These enable a fast penetration of the infiltrant into the altered carious surface up to a depth of 750 µm (Paris et al. 2007, 2009). The sealing of the carious cavity is now no longer restricted to the surface alone, but also encompasses the body of the cavity.

The anticipated result of this trial shall deliver information on the long-term effectiveness of caries infiltration and thereby result in an improvement in caries prevention within the scope of dental treatment, and prevent the progression of existing carious lesions . This is a micro-invasive form of treatment, which largely facilitates the delay or avoidance of conventional invasive initial dental treatment with the associated inevitable loss of healthy tooth structure. Further studies on the optimization of the infiltration technique can be built upon these results. In the long-term, it will be possible to use these findings to develop new prevention and treatment options for approximal carious lesion .