Amalgam substitute in posterior region with an ormocer combination – a clinical case study

Direct composite restorations for the posterior region have become a standard part of modern conservative/ restorative dentistry. This type of restoration is very popular with patients and dentists alike, and its performance in the masticatory load-bearing posterior teeth has now been demonstrated in numerous clinical studies. In addition to composites based on conventional methacrylate chemistry, ormocer composites can also be used for this range of indications.

INTRODUCTION

The range of products available in the field of direct composites has expanded greatly in recent years[ 1- 3]. In addition to the conventional universal composites, the enormous rise in patients’ aesthetic expectations has resulted in the launch of a large number of so-called “aesthetic composites” on the market. These offer composite materials in different opacities and translucencies, each in a sufficient number of different shades[ 4]. Opaque dentine shades and translucent enamel shades make it possible to achieve highly aesthetic direct restorations using the multi-shade (polychromatic) layering technique. They are practically indistinguishable from the dental hard tissue and, in individual cases, they even rival the aesthetics of all-ceramic restorations[ 5, 6]. Some of these composite systems comprise more than 30 different composite materials of different shades and degrees of translucency. It is, however, essential to have appropriate experience in the handling of

these materials, which are primarily used in the anterior region[ 4, 7]. On the other hand, another trend observed in composite development in recent years consists in making the use of these materials in the posterior region simpler and more reliable at the same time[8-14]. The introduction of bulk-fill composites made it possible to achieve this goal while also improving cost-efficiency in use by increasing the layer thicknesses that can be light-cured – from 2 mm previously to 4-5 mm – and simultaneously shortening the curing times[ 15- 19]. Most composites contain organic monomer matrices based on conventional methacrylate chemistry[ 20]. Silorane technology[ 21-26] and ormocer chemistry[ 27-34] present alternative approaches. Ormocers (“organically modified ceramics”) are organically modified, non-metallic, inorganic composites[ 35]. Ormocers can be classified between inorganic and organic polymers and possess both an inorganic and an organic network[ 32, 36- 38]. This group of materials was developed by the Fraunhofer Institute for Silicate Research (ISC) in Würzburg and marketed for the first time as a dental restorative material in 1998 in collaboration with partners in the dental industry[ 29, 30]. Since then there has been considerable further development of the ormocer-based composites for this range of applications. In the dental ormocers to date, additional methacrylates were added to the pure ormocer chemistry (in addition to initiators, stabilisers, pigments and inorganic fillers) in order to improve workability and adjust the viscosity of the matrix[ 39]. Therefore, it is better to speak of ormocer-based composites here. The nanohybrid ormocer restorative material Admira Fusion (VOCO, Cuxhaven) does not contain any conventional monomers alongside the ormocers in its matrix. It features a nanohybrid filler technology with an inorganic filler content of 84% by weight. The material displays a polymerization shrinkage of 1.25% by volume with a simultaneously low shrinkage stress (3.87 MPa). Thanks to its material composition, Admira

Fusion also has high biocompatibility and colour stability. Admira Fusion is available in a wide spectrum of shades in three levels of translucency/ opacity (10 universal Vita shades, 4 opaque dentine shades, 4 special shades) and can thus be used in aesthetically demanding situations in both the simplified single-shade technique, for example in the posterior region, and a polychromatic multiple-layer technique, according to requirement. This restorative material is complemented by the low-viscosity, flowable Admira Fusion Flow (VOCO, Cuxhaven), which is available in 12 shades and displays outstanding flow properties even in the narrowest of cavity regions thanks to its excellent wetting properties. For a flowable material, Admira Fusion Flow displays a low polymerization shrinkage of 2.75% by volume with a simultaneously low shrinkage stress (7.27 MPa).

CLINICAL CASE

A 42-year-old patient presented in our practice requesting the replacement of an amalgam restoration in tooth 46 (lower right first molar) with a tooth-coloured restoration (Fig. 1). The tooth responded sensitively to the cold test without delay and the percussion test was also normal. Hav- ing been informed of the possible treatment alternatives and their costs, the patient elected to have a composite restoration with the nanohybrid ormocer Admira Fusion (VOCO GmbH, Cuxhaven) in the single-shade technique. Treatment started with thorough cleaning of the tooth with a fluoride-free prophylaxis paste and a rubber cup to remove external deposits. The appropriate composite shade was then determined on the still wet tooth using the shade guide supplied with the system. Following administration of local anaesthetic, the amalgam was carefully extracted from the tooth (Fig. 2). After excavation, the preparation was finished with a finegrit diamond bur (Fig. 3) and the treatment area then isolated using a rubber dam (Fig. 4). The rubber dam separates the operating site from the oral cavity, facilitates clean and effective working, and guarantees that the working area remains free of contaminating substances such as blood, crevicular fluid and saliva. Contamination of the enamel and dentine would result in considerably poorer adhesion of the composite to the dental hard tissue and would endanger the long-term success of a restoration with optimal marginal integrity. Additionally, the rubber

dam protects the patient from irritating substances such as the adhesive system. The rubber dam is thus an essential aid in ensuring quality and facilitating work in the adhesive technique. The minimal effort required in applying the rubber dam is also offset by avoiding the changing of cotton rolls and the patient’s requests for rinsing. The cavity was then demarcated with a sectional matrix made of metal, which was adapted to the cervical shoulder with the help of a plastic wedge (Fig. 5). The matrix system’s clamping ring guarantees sufficient separation of the tooth from the mesial adjacent tooth and ensures tight approximal contact of the new restoration. The universal adhesive Futurabond M+ (VOCO GmbH, Cuxhaven) was chosen for the adhesive pre-treatment of the dental hard tissue. Futurabond M+ is a modern one-bottle adhesive which is compatible with all conditioning techniques: the self-etch technique and both phosphoric acid-based conditioning techniques (selective enamel etching or com- plete etch and rinse pre-treatment of enamel and dentine). In this case, the total etch pre-treatment of enamel and dentine with phosphoric acid was employed. Firstly, 35% phosphoric acid (Vococid, VOCO GmbH, Cuxhaven) was applied in a circle along the enamel margins and allowed to work for 15 seconds. Subsequently, all the dentine in the cavity was additionally covered with etching gel (total etch) (Fig. 6). After a further 15 seconds, the acid, along with the products dissolved from the dental hard tissue, was rinsed off for 20 seconds with the compressed air and water spray, and excess water then carefully removed from the cavity with compressed air (Fig. 7). Figure 8 shows the application of a generous amount of the universal bonding agent Futurabond M+ to the enamel and dentine with a microbrush. The adhesive was thoroughly rubbed into the dental hard tissue with the applicator for 20 seconds. The solvent was then carefully dried off with dry, oil-free compressed air (Fig. 9) and the bonding agent light-cured for 10 seconds (Fig. 10). The result was a