A new category of composite resin

March 21, 2012

There is no material in the history of dentistry that has undergone as much evolution as composite resin. The face of restorative dentistry changed forever when successful bonding to dentin was achieved. Since then, the goal of clinical and material science has been to find simple, predictable approaches to the composite restorative process.

There is no material in the history of dentistry that has undergone as much evolution as composite resin. The face of restorative dentistry changed forever when successful bonding to dentin was achieved. Since then, the goal of clinical and material science has been to find simple, predictable approaches to the composite restorative process.

Unlike dental amalgam, the patrician of direct restoratives, placing composite requires many more steps and exacting technique to achieve the best results. The process of adhesion, conditioning the tooth surface, applying primers and adhesives, followed by layering the composite resins to complete the restorative process involves many independent steps that must be properly executed to ensure good results. Successive generations of dentin adhesives have sought to decrease the number of steps for placement without sacrificing clinical results. The seventh-generation self-etching dentin bonding systems have helped decrease technique and post-operative sensitivity issues while still yielding clinically acceptable restorations. Many clinicians even have used flowable resins as the first layer of composite resin after placing adhesive to ensure precise wetting of the adhesive surface, while creating a layer with less polymerization stress because of a lower modulus of elasticity (< 0.5 mm thickness).

A new composite material, Kerr Corp.’s Vertise Flow (kerrdental.com), combines the adhesive and flowable steps into one, resulting in one of the first self adhering composite materials on the market.

Mechanism of adhesion

There are two distinct mechanisms of adhesion for self adhering materials-chemical and micro-mechanical. The primary bonding mechanism for Vertise Flow is chemical bonding between the calcium ions in the hydroxyapatite crystals and the phosphate groups in the glycerol diphosphate dimethacrylate (GPDM), which is the adhesive monomer common to all adhesives in Kerr’s OptiBond family of dentin adhesives.

Vertise Flow also bonds to tooth structure via micro-mechanical retention, which is the result of the interpenetrating network formed between the polymerized monomers in the material and the collagen fibers and hydroxyapatite crystals within the smear layer. Brushing this first layer of material vigorously into the tooth surface enhances this penetration into the smear layer and creates a bond comparable to what most available seventh-generation dentin bonding agents can achieve.

A simplified approach

Two clinical cases will be presented to illustrate a “simplified approach” to matrix and placement of direct posterior composites. This technique provides an accurate reproduction of the proximal surface and contact, also decreasing the number of steps involved in the adhesive restoration process. Decreasing the amount of rotary finishing and contouring required to complete the restorative process also saves chair time.

Preparation and matrix

The patient presented with a Class II cavity present on the mesial surface of a maxillary left second molar (Fig. 1). After preparation of the proximal box portion of the preparation, the interproximal gingival papillae was “nicked” with the bur, causing hemorrhage that could interfere with the bonding process. A new hemostatic product, Kerr’s Hemostasyl, is syringed into the proximal area. It remains in place for about one minute (Fig. 2) and is then rinsed away with an air-water spray. Hemostasyl’s consistency keeps it in place until it is removed, unlike liquid-type hemostatic agents. Fig. 3 shows two approximating preparations in the maxillary left first and second premolars.

After placing and rinsing Hemostasyl, the proximal area between the premolar preparations is devoid of blood, and placement of the matrix can be done easily without causing the tissue to bleed (Fig. 4).

A sectional matrix, Garrison Dental Solution’s Composi-Tight 3D
(garrisondental.com) is used to simplify the restorative process. The “soft anatomically shaped pads” of the 3D ring fill the proximal embrasure spaces, adapting the sectional matrix strip precisely to the cavosurface margins. The contact is assured without burnishing the band against the adjacent tooth, causing deformation of the restoration. As long as the band is visually touching the adjacent surface, because the ring causes separation by compressing the periodontal ligament spaces, a curved hemostat will be required to remove the band when the restoration is complete.

The latest improvement to the Composi-Tight 3D system is “Slick Bands.” The non-stick inner surfaces allow for more accurate and smooth proximal surfaces when placing the composite material.

Simplifying the process

Once the sectional matrix is placed, the restorative process begins. Vertise Flow self adhering flowable composite replaces the need for the conventional bonding steps of etching, rinsing, and adhesive placement prior to the application of the flowable resin. A thin layer of Vertise Flow (less than 0.5 mm in thickness) is brushed onto all cavity walls, enamel and dentin, (bevels included) with moderate pressure for 15 to 20 seconds. Any excess around the margins is removed with the brush (Fig. 5) and the material is then light cured for 15 to 20 seconds. Fig. 6 shows the preparation after application of Vertise Flow to all cavity surfaces and light curing. Notice the appearance of the cavity surface compared with the freshly prepared surfaces in Fig. 4. The surfaces of the cavity appear similar to a “faux painted,” textured surface. This is indicative of the correct amount of Vertise Flow used for the initial creation of the adhesive layer to dentin and enamel. If desired, an additional increment of Vertise Flow can then be applied (up to 0.5 mm) as a cavity liner and spread with a brush into all line and point angles of the preparation (Fig. 7). This ensures complete and accurate covering of all internal cavity walls.

Placing the nanohybrid composite

As direct composites have evolved for universal application, there always has been a trade off in handling and polishablity for materials designed for anterior and posterior use. A new nanohybrid, Kerr’s Herculite Ultra, simplifies esthetic anterior and posterior placement of composite resins, according to the manufacturer. This product has been positioned for use in a mono-layering technique as an alternative to complicated layering to achieve optimal esthetic results. The consistency of Herculite Ultra is creamy, yet it is a sculptable material with no slumping and good chameleon effect.

The first increment of Herculite Ultra is placed and condensed using a non-serrated plugger (Fig. 8). A plastic filling instrument is used to sculpt the occlusal layer of the maxillary left second premolar (Fig. 9). Note that in this case, where adjacent proximal surfaces require restoration, apply the matrix and restore one preparation to completion, then matrix the other tooth and restore it creating contact to the first restoration. Always contour and polish the finished composite surface as needed before filling the adjacent preparation.

Axis Dental’s TDF- 3 (axisdental.com), a small 8-fluted carbide finishing bur, is used to finesse the occlusal embrasure occlusal to the proposed contact area (Fig. 10). Remember, the proximal contact is located 1 mm apical to the height of the marginal ridge. Once polished, the sectional matrix is applied to the adjacent tooth, and the restoration is completed (Fig. 11). Figs. 12 and 13 show the completed restorations after application of surface sealant. Note how nicely the restorations blend into the natural tooth.

The message

A technique has been shown using an innovative self adhering composite and a simplified mono-layering nanohybrid composite system. Vertise Flow has been shown to deliver comparable results to many of the seventh-generation bonding systems without the need for a separate bonding step. Combined with a simplified restorative system, such as Herculite Ultra, a more concise, less technique sensitive alternative to traditional direct composite placement is now available.