Nobio Clinical Study

As a major issue in dentistry, it has been stated that two-thirds of all restorative dentistry involves the replacement of failed restorations. Secondary caries indicates a lesion developing at the margins of an existing restoration and is the major reason for replacement of amalgam and composite resin restorations in operative dentistry.

In research the use of experimental intra-oral caries models dealing with caries prevention has increased. The most realistic experimental model is the in vivo model that uses living teeth, followed by the in situ model using specimens with natural surfaces held in the mouth during the experimental period. In situ models have the potential to study both fundamental aspects of the caries process as well as more applied research problems in caries prevention in human subjects without actually causing caries in the natural dentition.

To simulate a failed interface between a tooth and a restoration, a gap can be formed between an enamel slab and the restoration prior to a cariogenic challenge. The "gap-model" will be inserted for instance into the denture flanges, and the cariogenic challenge occurs inside the mouth during the wear period..

Nobio has developed dental restorative materials with long term antibacterial properties in order to fight recurrent decay around restorations. These composites with incorporated non-leaching antibacterial agents might overcome the vicious circle of newly developed cavities around freshly placed fillings. The ongoing caries activity due to bacteria around the filling may be interrupted by quaternary ammonium silica dioxide (QASi) particles incorporated in the test composite at 1.2% (by weight). These particles are members of the Nobio Antimicrobial Particle (NAP) family (Nobio, Israel). QASi are synthesized to form a high concentration of antimicrobial groups that are covalently-bound onto a carrier core, such as silica. The resulting micro or nano-sized QASi particles are mixed with other fillers of the dental composite material, during manufacturing. Following in situ placement and light-initiated polymerization, QASi particles are permanently retained in the final dental restoration. Laboratory studies have shown that the quaternary ammonium silica particles are potent antibacterial agents, do not leach out in contrast to other antimicrobials or caries preventive active substances, inhibit the breakdown of the composite, and maintain antibacterial activity over time.

The study is an in situ study. Subjects, wearing lower partial dentures with acrylic flanges on both sides of the mouth will be recruited. On each side of the denture an enamel slab will be placed next to a composite, separated by a tiny gap. On one side of the denture the composite will be Nobio's antibacterial composite, on the other side a regular composite (a Nobio composite w/o particles or another commercial composite will serve as control material. Enamel slab and composite will be recessed into the flange, allowing microbial plaque to accumulate on top of it and especially in the gap.

After wearing the dentures for four weeks with the slabs, decalcification - ΔZ mineral loss - in the enamel slabs adjacent to the gap will be determined by cross-section microhardness testing in the laboratory. Average ΔZ mineral loss will be calculated for the Nobio group and the control group, and difference will be tested for statistical significance.