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hygiene tribune Dental Tribune Middle East & Africa Edition | May-June 20152B > Page 4B Shape and colour – factors in sectional matrices as well? By Prof. Claus-Peter Ernst D irect composite restora- tions can now be consid- ered a proven standard treatment method in the poste- rior region [1, 3]. However, treat- mentcandiffersignificantlywith regard to extension and stress, and this can have a definite in- fluence on long-term survivabil- ity. There are many factors that determine the long-term suc- cess of a composite restoration: tightly sealed edges are primar- ily guaranteed by the adhesive technique [2]. For dental materi- als, besides low shrinkage stress [4, 11], the material also has a high flexural strength [6, 10] in order to minimise the risk of the restoration undergoing a co- hesive-type failure. A fractured filling is clearly a more dramatic event for the patient than a dis- coloured edge. For the patient, the success of direct posterior tooth treatment with compos- ites thus depends on its stability. Besides the adhesive technique and the selection of materials for the restoration, the crucial key function of correct light poly- merisation also playes a decisive role [5]. It is completely possible to double the flexural strength of one’s own composite just by us- ing the correct light curing and light curing technique. A further possible influence on the stabil- ity of a posterior tooth composite restoration is less well-known: the correct anatomical shape of the interproximal surface. If this is shaped like a natural tooth, the interproximal contact is at the height of the tooth equator and the marginal ridge is not too excentric. This reduces the risk of ridge fractures – both purely cohesive chipping fractures as well as more complex, mixed cohesive/adhesive failure pat- terns. Lohmanns et al. [8] were able to show that the stability of an interproximal composite res- toration can be increased signif- icantly by using an anatomically shaped matrix. The correct posi- tioning of the interproximal con- tact also facilitates the achieve- ment of sufficient contact strength – provided clamping rings are used correctly. Surpris- ingly, the interproximal contact strength is not the result of the pressure of a wooden wedge; it is primarily caused by the sepa- ration force of the sectional ma- trix ring [7, 9]. Automatically – as a side effect - fewer interproxi- mal food impactions occur as a result. For this reason, sectional ma- trices are now the first choice when it comes to correctly de- signing interproximal contact surfaces. Circular matrices, even when they are anatomi- cally shaped, should be used when it is not possible to fix sec- tional matrices in place. This is the case, for instance, for distal cavities on the last tooth in a row, as well as for teeth that are not in an anatomically correct position as for example a rotated tooth. The general acceptance of sectional matrix systems is also shown by the extensive range of sectional matrices and rings, which are now available. In gen- eral, sectional matrices can be roughly divided into two groups: dead-soft matrices and stable steel versions. The supporters of dead-soft sectional matrices like their easy mouldability and adaptability to the tooth. Howev- er, critics dislike their lack of sta- bility if an interproximal contact that is left untouched and has to be surpassed by the matrix or if a wooden wedge, cannot be op- timally placed and thus the sec- tional matrix presses it into the cavity. Three clinical cases are pre- sented below in which a new sectional matrix system is ap- plied that, because of the special dyeing method despite dead- soft steel, belongs in the second group of stable and thus some- what more safely used sectional matrix systems. Clinical case 1: Upper right 2nd premolar The 48-year-old patient was treated six months ago with a Biodentine (Septodont) filling to the 2nd upper right premolar 15 (Fig. 1). The temporary fill- ing is now to be replaced with a permanent filling. The sub- sequent excavation of the very deep occlusal-mesial cavity was possible without any problems; it was possible to avoid a pulp opening using this two-step ap- proach. Figure 2 depicts the cavity with the Polydentia Lu- miContrast sectional matrix in combination with the associated ring under rubberdam isolation. The extremely stable and thus “wrinkle-resistant” sectional matrix can be easily manipulat- Fig. 1: Biodentine temporary treat- ment the upper right 2nd premolar. Fig. 6: The treated upper right 2nd premolar at a further follow-up ap- pointment one year later. Fig. 2: The cavity margins can easily been identified by means of the Poly- dentia LumiContrast sectional ma- trix in combination with the associ- ated sectional ring under rubberdam isolation. Fig. 7: Cohesive type fracture in the mesio-occlusal amalgam filling in a lower right 2nd molar. Fig. 3: Conditioning of the cavity with phosphoric acid gel. Fig. 8: The excavated, prepared cav- ity, isolated under rubberdam and equipped with the LumiContrast sec- tional matrix system. Fig. 4: Sealing of the cavity with a tra- ditional two-bottle adhesive. Fig. 9: The finished composite resto- ration. Fig. 5: Finished and polished restora- tion (tooth 15). Fig. 10: The lower right 2nd molar - once treated with the resin composite - one year later: possibility of conduct- ing a clinical-visual inspection of the interproximal surface of tooth due to the fracture of the amalgam filling the 1st molar. Fig. 11: Lower right 1st molar with MIH, which needed a restorative treatment. Fig. 12: The excavated, prepared cav- ity equipped with the LumiContrast sectional matrix system under rub- berdam. Fig. 13: Completed, direct composite restoration to the lower right 1st mo- lar. ed and positioned in the contact area. One benefit of this matrix system is the almost black col- our, which has been achieved using a special dyeing process (no coating!) for the metal car- rier foil. This produces an out- standing contrast in the transi- tion to the hard tooth tissue. This makes it much easier to inspect the cervical seal, as there is no disruption caused by reflections in the metal film. A traditional wooden wedge was used cervi- cally to tighten the cervical mar- gin there. The LumiContrast separation ring can be used in two versions: firstly, as shown in the figure, corresponding to a classic Silver separation ring. However, there is also the pos- sibility of fitting small triangu- lar silicone sleeves that enable improved interproximal seal- ing of the sides, as they better press the sectional matrix films to the sides of the interproximal preparation surfaces. However, this was not necessary in the present case. Figure 3 shows the cavity conditioned with phos- phoric acid gel, figure 4 shows the adhesive surface sealed with a traditional two-bottle adhesive (Optibond FL, Kerr). The resto- ration was built out of a nano hy- brid composite (Venus Diamond A3, Heraeus Kulzer, Hanau, Germany) using an oblique lay- ering technique (Fig. 5). Figure 6 shows the same tooth at a fur- ther follow-up appointment one year later. Clinical case 2: 2nd lower right molar The 50-year-old patient present- ed with a cohesive type fracture in the mesio-occlusal amalgam filling of his lower right 2nd mo- lar (Fig. 7). In the distal marginal ridge, a minor amount of abfrac- tured enamel was visible . After explaining all possible treatment options to the patient, there was consent, that the best option might be the directly placed res- in composite restoration. Figure 8 shows the excavated, prepared cavity, isolated with rubberdam and also equipped with the Lu- miContrast sectional matrix sys- tem(Polydentia,Switzerland).In contrast to case 1, the interproxi- mal sides were far more open compared to case 1. For this reason, the triangular silicone sleeves were fitted to the Lumi- Contrast separation ring. This made it possible to better adapt the sectional matrix foil to the sides of the preparation and thus consequently minimise the ma- terial overhang, resulting in less finishing and polishing work. Due to the silicone sleeves that can be fitted individually from case to case, e.g. only one ring foot may need to be fitted with a sleeve, the others meay remain free. This significantly increases flexibility in using the clamp- ing ring and also simplifies the preparation procedure in that there is no need to prepare the ring separately as were perma- nent silicone inlets have to be taken care of. Figure 9 shows the finished composite restora- tion (Optibond FL /Kerr, Venus Diamond A3/Heraeus Kulzer); figure 10 shows the situation af- ter another year: the distal por- tion of the amalgam filling in the 1st lower right molar fractured – this offered the rare opportunity for a clinical-visual inspection of the interproximal surface of the 2nd right lower molar created one year earlier. Clinical case 3: 1st lower right molar The 20-year-old patient exhib- ited molar-incisor hypominer- alisation (MIH). His lower right 1st molar required restorative treatment in the region of the occlusal-buccal surface (Fig. 11). For cost reasons, as well as from the viewpoint of minimal- ly-invasive caries treatment, it was agreed with the patient to initially undertake direct treat- ment in the form of a resin composite restoration. Figure 12 shows the excavated, pre- pared cavity equipped with the LumiContrast sectional matrix system under rubberdam. In the present case – similar to case 1 – it was again not necessary to fit the silicone sleeves to the LumiContrast clamping ring. Sufficient moulding and adapta- tion of the sectional matrix foil was possible there. The excel- lent contrast between the almost black sectional matrix foil and the interproximal -cervical tooth enamel margin can once again be seen. The direct composite restoration was again made out of the nano hybrid composite Venus Diamond (Heraeus-Kulz- er), this time in the shade A2,5 using a traditional two-bottle adhesive system (Optibond FL,