Polishing of dental hybrid materials

While the use of hybrid materials has recently gained popularity in fabricating indirect restorations, polishing such material pushes conventional polishing agents to their limits. For this reason, a technical and scientific analysis depicts how Renfert Polish hybrid materials addresses this concern to achieve fast, economical polishing with optimal outcomes.

By Dr Frank Weber and MDT Manfred Tauber

Uniting the positive properties of two distinct materials, hybrids like CAD/CAM materials and filled veneer composites are increasingly used to fabricate indirect restorations (Fig. 1). This combination of ceramics and polymers exhibits a high load-bearing capacity with improved abrasion behaviour while reducing brittleness to easily process restorations.

But polishing pushes conventional polishing agents to their limits because each of the two materials has distinct requirements.

Another complicating factor is the uneven material ratio — high ceramic, low composite content — which varies from supplier to supplier. Thus, much more preparation and polishing work was previously required to achieve a satisfactory gloss level albeit with limited results.

Renfert Polish hybrid materials comprises a specialised diamond polishing paste which does precise justice to the unique needs of these hybrid materials (Fig. 2). The paste is designed to account for both the complex wetting behaviour as well as the different degrees of hardness of the two material proportions.

Why is it so important to polish the surface to a high gloss?

In addition to aesthetic aspects, various authors1 have demonstrated that the roughness of a surface correlates with the gloss within the high-gloss range.

On the other hand, the surface roughness has a critical mechanical impact on the antagonist and affects the growth of plaque. That means achieving a consis­tently long-lasting high gloss is the most viable indicator of low roughness and, in turn, reflective of high-quality work.

For that reason, Renfert develops, investigates and compares internally as well as through an external authoritative institute the roughness and level of gloss as defined by the gloss units (GU) of the various materials. This is the only way to achieve optimal outcomes, with consistently smooth surfaces even upon closer inspection.

Lubrication with oils and the application of soft waxes can be used to easily im­itate a visual high gloss on the materials, creating a short-term appearance, but that cannot be the objective.

Particularly when using veneer composites and modern hybrid materials with composite content, the objective must be to re­duce the plaque affinity as effectively as possible in order to extend the lifetime of the restorations.

The following presents the comparative studies of GU and topographic investi­gations of the surface roughness measurements of CAD/CAM-produced hybrid materials.

Continue reading here. Published in Dental Asia July/August issue.

About the authors

Dr rer nat Frank Weber joined Renfert GmbH in December 2016 as head of the Chemical Development Department. Prior to this, he was internationally active in various development and consulting positions in the solar industry. Dr Weber also worked in process development and evaluation for the chip industry at Infineon Technologies AG, especially in the field of cleaning and chemical mechanical polishing for nine years. This resulted in several patent submissions in Germany and the United States. Today, drawing from this broad professional experience, he is able to find unorthodox approaches to pragmatic solutions.
MDT Manfred Tauber is an active speaker at international dental congresses and conventions, as well as a publisher of many articles published in the international dental press. He built up his expertise through the 19 years of dental technician activities in Austria and Germany.