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A series of factors are important for the long-term success of Class II restorations. Some of these, including the design of the contact points and the adhesive joint, have already been addressed in this series of articles on the "Class II Solution" concept (Dentsply Sirona Restorative). This time, we quite literally take a look at the core of the treatment – the filling material itself. Our examinations focus on study data on the proven SDR technology in the original flowable bulk fill composite SDR and now also SDR flow+.
As tooth-colored filling materials, composites play an important role in today’s dental practices, especially when patients ask for an esthetic restoration. Bulk fill versions of these materials also enable the practitioner to forgo complex layering techniques and, instead, create fillings thicker layers and less steps. As the first composite with a flowable consistency which could be used for this technique, SDR (Dentsply Sirona Restorative) is a true pioneer in the bulk fill sector. Since its launch in 2009, this material has been used in more than 50 million restorations. In addition to real-life experience, the efficiency of SDR technology has also been confirmed conclusively in scientific studies which, in turn, has resulted in the creation of the new bulk fill generation SDR flow+.
The purpose of bulk fill materials is not only to tighten cavities in an esthetic and long-term manner; they are also designed to make the treatment process less stressful for the practitioner and patient alike. By making it possible to work in larger increments – up to 4 mm in the case of SDR flow+, the number of layering and polymerization steps is reduced. This also reduces the treatment duration and makes application easier. However, whilst this may be advantageous for patients and practitioners, it is often linked to increased stress within materials used. Van Ende, van Meerbeek et al. noted that "…when filling 4-mm-deep cavities using the bulk fill technique […] the micro-tensile bond strength dropped significantly, except in the case of the bulk fill composite SDR" [1]. The researchers concluded that the material from Dentsply Sirona Restorative was able to retain its adhesive strength even with this increment thickness.
The stress factor is also significant for the filling material itself, particularly in the form of shrinkage stress. This happens when the material contracts during polymerization. The resulting stress can compromise the integrity of the adhesive layer and might create gaps to the cavity walls, which can lead to post-operative sensitivity, penetration by bacteria and, ultimately, secondary caries. SDR technology provides a stress-free option: in a comparative study [2] which looked at the polymerization stress of 6 composites, SDR achieved the best results (1.1 ± 0.01 MPa). In this context, the SDR technology again showed itself to be a key success factor which enables the formation of a more relaxed polymer network during light curing. This helps to reduce stress by up to 60%.
Three clinical studies have already confirmed that bulk fill restorations using materials based on SDR technology correspond in terms of quality with conventionally layered fillings. Over an observation period of five [3] and six [4] years, van Dijken and Pallesen compared 100 / 49 Class I and Class II fillings, with SDR and an enamel capping made from an esthetic composite (ceram.x), with the same number of fillings produced using the conventional layering technique (ceram.x).No significant difference was observed between the bulk fill and layering technique. The researchers concluded that bulk fill restorations with SDR are a safe option and offer very good durability. A further clinical study over a period of 36 months performed by Burgess and Munoz also demonstrated the safety of the SDR filling technique with practically no post-operative hypersensitivities or other negative impacts. [5]
[1] Van Ende A, van Meerbeek B et al: Bulk-filling of high C-factor cavities: Effect on adhesion to cavity bottom dentin. University of Leuven, Belgium. Dental Materials 29 (2013) 269-277.
[2] Ilie N, Hickel R: Investigations on a methacrylate-based flowable composite based on the SDR® technology Dental Materials 27 (2011), 348-355.
[3] Van Dijken JWV, Pallesen U: Posterior bulk-filled resin composite restorations: A 5-year randomized controlled clinical study; J Dent 2016 Aug;51:29-35.
[4] Internal report # 14.1488 (2016-11-07); data on request.
[5] Internal report # 765-540 (2012-02-17); data on request.
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