A lecturer and researcher from the Department of Conservative Dentistry, Faculty of Dentistry, Universitas Gadjah Mada (FKG UGM), drg. Margareta Rinastiti, M.Kes., Sp.KG(K)., Ph.D., together with a research team from the University Medical Center Groningen, the Netherlands, has identified a practical scientific solution for optimizing dental restoration repair procedures. The research demonstrated that adding a new layer over an existing restoration (repair) can achieve strong adhesion, provided that the surface of the existing restoration is prepared using a silica-coating technique (tribochemical silica coating).
Published in the Journal of Dentistry, this important finding provides a strong scientific basis for dental practitioners to avoid simply bonding new material onto an existing resin composite restoration during repair procedures. This innovation represents a step forward in supporting the principles of minimally invasive dentistry, which prioritize repairing restorations without removing the entire restoration and unnecessarily sacrificing healthy tooth structure, making the procedure more conservative and patient-friendly.
When dentists identify defects in a recently placed resin composite restoration—such as an inappropriate color, an unsuitable shape, or an area requiring correction—they face a dilemma. Removing the entire restoration and replacing it from scratch risks sacrificing more of the patient's natural tooth structure and potentially irritating the dental pulp. However, adding a new layer onto a hardened restoration is also challenging because its chemical bonding capacity is no longer active, meaning that the new layer may detach prematurely.
To overcome this challenge, drg. Margareta Rinastiti and her team conducted a laboratory experiment to test three commonly used types of resin composite: microhybrid, nanohybrid, and nanofilled. The researchers compared four different methods for preparing the restoration surface before applying the new material, ranging from leaving it untreated (control), using a thin plastic layer (Mylar strip), applying a conventional adhesive liquid (intermediate adhesive resin or IAR), and using an intensive silica-coating method (SC).
The results showed that the use of conventional adhesive liquid (IAR) did not significantly increase bond strength. The research team explained this phenomenon in their scientific report:
“The application of intermediate adhesive resin did not result in a significant increase in bond strength in fresh composite. This may be because the degree of conversion in newly cured composite was still high, so the benefit of IAR was not apparent.”
In contrast, restoration samples treated with silica coating (SC)—which involved spraying them with specialized silica-coated alumina particles, applying a silane chemical agent, and then applying IAR—showed remarkable results. This technique increased the average bond strength by 8.9 MPa compared with the other groups. In three of the four composite types tested, bond strength reached approximately 25–27 MPa, an ideal range approaching the target recommended in the scientific literature.
The superiority of the silica coating method was also demonstrated through analysis of fracture patterns under a microscope. All samples treated with the silica technique exhibited 100% cohesive failure. This means that when the samples were tested to their maximum limit, the damaged or fractured area was not the bond between the layers but the composite material itself. This provides strong evidence that the resulting bond was stronger than the restorative material itself and was therefore highly reliable from a clinical perspective.
X-ray spectroscopy analysis showed that silica spraying increased the silica content on the surface by up to fourfold and made the surface microscopically rougher. This rough surface created a mechanical area that allowed the new layer to interlock firmly with the existing material, aided by the silane agent, which strengthened the chemical bond.
Clinically, this research provides practical implications at the dental chairside. When patients require repair of a recently placed restoration, dentists now have scientifically supported guidance for applying the silica coating procedure to achieve more durable results.
Nevertheless, the researchers noted that certain composites, such as Tetric Evo Ceram, did not show a significant improvement because of the characteristics of their specific monomers. UGM hopes that these findings can be further developed through subsequent research, particularly to evaluate the performance of bond strength after prolonged exposure to the actual oral environment, thereby ensuring long-term oral health.
Author: drg. Achmad Zam Zam Aghasy, M.Kes., Annisa Dwi Noviyanti
Photo: Pixabay
Source DOI: https://doi.org/10.1016/j.jdent.2009.08.009