What is Smart Dentin Replacement?

by Dr. Frank Pfefferkorn

Do you remember how a crumbling mixture could turn an easy and safe amalgam filling into a challenge? Have you found the stickiness of the material troublesome when placing tooth-coloured fillings with a composite material? Do you loathe constructing a filling using the layering technique? If so you probably wish for a more simple yet reliable and safe procedure during your hectic daily routine. How such a process works, and how it was developed, is described below.

Besides the correct application of the bonding agent, and for this please follow the manufacturer’s instructions for use carefully, the following step is of vital importance. What is the advantage of a filling material that shows excellent mechanical properties under ideal circumstances in the laboratory but is difficult to apply in a cavity? Here, the intimate adaptation to the adhesive layer, as well as the smooth application of small increments without surface defects, is the most important factor for a high quality filling. The use of flowable composites has found widespread use particularly where a simple and safe initial adaptation is required. However, there is no proof that this, in general, is accompanied by a reduction of polymerization stress1.

Researchers at DENTSPLY have now developed modified monomers2 which, in combination with conventional methacrylate-based monomers, lead to significantly reduced polymerization stress independent of the filler load. With this, the idea was created to develop a flowable material that allows an efficient and safe cavity filling technique. As a flowable consistency is not ideal for either the occlusal reconstruction or the required wear resistance, the occlusal capping with a universalcomposite was considered from the beginning. In other words, dentine can be cleverly replaced with SDR™ – Smart Dentin Replacement.

What makes SDR™different?
SDR™ is based on the chemistry of conventional universal composites and therefore, a certain adhesive or a combination of a special material for occlusal coverage is not necessary. The main difference lies in a modulator that is incorporated into a urethane-based dimethacrylate. With this, a conventional network structure is built from conventional monomers and the SDR™monomer (Fig.1).

Fig. 1 The SDR™ monomer with modulator builds a network with conventional monomers.


The difference is not that the modulator becomes a part of the polymerized network but that it influences its development and, especially, how quickly the network is built. With this, polymerization stress is reduced from the very beginning.

What has been tested?
Measurements conducted at the University of Munich recorded the contraction force during polymerization in 0.2 sec. intervals demonstrating how SDR™ differs from other materials (Fig.2).

Fig 2. Contraction force in the first 5 seconds after polymerization. Ilie N (2009).

This difference remains during further polymerization and leads to significantly reduced polymerization stress (Fig. 3).

Fig. 3 Polymerization stress after 5 minutes. Ilie N. (2009)3

Besides low polymerisation stress it is important to have a high depth of cure. This is achieved with one universal shade with sufficient translucency. Samples prepared with different layer thickness have been tested after a curing time of 20 seconds. Successful curing is achieved when the hardness of the lower side of a sample reaches a minimum of 80% of the upper side. Figure 4 shows SDR™ compared to other flowable materials applied in increments of up to 5mm. It is clear that SDR™ has a much higher depth of cure than other flowable materials.

Fig. 4 Relative Knoop Hardness of different flowable composites as a measure for depth of cure.


The combination of very low polymerization stress, along with a high depth of cure, allows layering in 4mm increments. This simplified procedure with SDR™, in comparison to conventional flowable composites, is shown in Fig. 5.

Fig. 5 Conventional layering technique with composites vs. Simplified filling technique with SDR.


Representative for many other studies regarding the compatibility (of SDR™) with adhesives and composites for the capping layer is the result of a chewing simulation shown below. Incrementally layered fillings (adhesive and composite of the same manufacturer) were compared with simplified filled cavities using the same bonding agent and composite and additionally SDR™, before and after chewing simulation regarding their marginal quality. All cases showed that using SDR™ in 4mm layers and capping with a universal composite, provides the same level of marginal quality compared to a restoration using incremental layering (Tab.1)4.

Tab.1 Adhesive systems tested with chewing simulation.

Summary
SDR™ allows the use of a simplified filling technique applied in increments of up to 4mm and capped with a universal composite at the occlusal surface. This is achieved with a reduction in the polymerization stress and a high depth of cure. To achieve this, a modulator has been built into the conventional monomer – this also allows SDR™ to be used with other conventional adhesives and composites. A chewing simulation demonstrated that, with this simplified filling technique; the same marginal quality of a restoration can be achieved compared to a restoration created using an incremental layering technique. With this a new, simplified and safe procedure becomes available for use in your daily practice.

References
1. Braga RR et al. J Am Dent Assoc 2003;134;721-728

2. Patent pending

3. Ilie N (Academy of Dental Materials 2009 Poster #10)

4. Frankenberger R. 2008. (Details in Scientific Compendium SDR www.dentsply.eu) * Filtek Supreme XT, Filtek Supreme Flow, Filtek Silorane, Tetric EvoFlow, Premise Flow, Grandio Flow, Syntac, Adper Prompt L-Pop, iBond SE and Venus Diamond are not registered trademarks of DENTSPLY International.

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