Entwicklung eines neuen Applikationsverfahrens für fließfähige Komposite zur Reduktion polymerisationsbedingter Spannungen

The polymerisation shrinkage and the resulting stress in teeth is one of the most frequent reasons of composite restorations failing today. Therefore, the composite research has been dealing with this problem for years. To reach a suitable adhesion of the filling and a sufficient polymerisation of the composite, the incremental technique (by using a conventional composite) is state of the art. However, this technique is time-consuming. To save time when filling big cavities, so-called bulk-fill composites were launched several years ago and became increasingly popular. For this study the two bulk-fill composites SDR® (Dentsply DeTrey, Konstanz, Germany) and x-tra base (VOCO, Cuxhaven, Germany) were researched. Based on the “Gradientenmodell” by Sommer and Gente we hypothesized that precuring the composite during application could reduce the stress significantly. This is achieved by inducing the gel-phase of the composite immediately after its adaption to the cavity wall. Using this method the “gel-shrinkage” of the composite applied before should be reduced by the subsequent flow of the material. The appropriate amount of light is crucial for the success. Basis of comparison was the bulktechnique (according to the manufacturer’s information) and the incrementaltechnique. The stress measurement was performed by using the established photoelastic method. The present study is believed to demonstrate a new solution to reducing stress and show a first technical implementation of the aforementioned method. This was achieved by putting a white LED onto the application gun. By using an analogue computer an automated adjustment of the curing light was reached, and the composite could be applied at variable speeds. This application method and device were registered as an invention by Prof. Dr. M. Gente and myself. The Philipps-University (Marburg, Germany) applied it for a patent.The results of the research show a significant reduction of the stress by using the precuringtechnique. An overall conclusive explanation of the observed stress reduction could be made by the extension of the „Gradientenmodell“ by Sommer and Gente from three to four phases. A difference in the effectiveness of the precuringtechnique between the two bulk-fill materials arised. Using x-tra base with precuringtechnique is as effective as the incrementaltechnique; using SDR® with precuringtechnique achieved even significantly lower stress results. In future an improvement of the technical realization of this promising method will follow. Likewise the feasibility of other composites should be looked at.