Placing Predictable Posterior Restorations
Innovative bulk-fill composite offers long-lasting esthetic restorations and saves chairtime.
The most common procedures performed by general and restorative dentists—other than prophylaxis—are direct Class I and Class II composite restorations, which are often fraught with complications.1-3 Taking most clinicians at least twice the time to complete, composite restorations are more technique-sensitive than conventional amalgam fillings. However, because composites demonstrate unparalleled esthetics, they are the preferred treatment option of many patients.4
Although the chemical composition has remained mostly unchanged, manufacturers have changed the size of filler particles to address some early difficulties associated with composite resins.4 Today, most resin-based composites demonstrate a mean glass-filler particle size ranging from 0.4 µm (400 nm) to 0.6 µm (600 nm), with surrounding silicone-dioxide particles smaller than 0.1 µm (100 nm).3 This decreased filler particle size allows composites to be finished to a smooth and esthetic surface.3
Because all composite resins demonstrate some degree of polymerization shrinkage—typically around 2% to 3%—added strain is placed on the restoration and the surrounding tooth structure to which the resin is bonded.3,4 Dentists, therefore, have become accustomed to the formation of the "white line" caused by the stress released from the tooth, which is usually due to some sort of trauma.3 Aside from being unesthetic, the white line may contribute to marginal leakage and the development of secondary caries.3
The most significant challenge faced in Class II composite restorations, leakage at the gingival level, can cause a plethora of problems for patients and dentists.3,5,6 Marginal leakage, which is often caused by polymerization shrinkage, typically leads to the need for endodontic therapy.3 When composite shrinks, it strains and breaks the union between the bond and the tooth, creating a gap and, consequently, causes flexing of the entire cusp.3 The gap then represents an entryway that enables leakage and the development of proximal and marginal decay.3
In the past, dentists used resin-based glass-ionomer products to thinly line the base of preparations before placing bonding agents to prevent leakage and sensitivity.3 A flowable resin was then placed over the bonding agent to further reduce shrinkage effects.3,6 However, recent studies have found that this type of preventive technique is mostly ineffective.6-8
To achieve predictable and stable results, dentists then transitioned to a sandwich-layering technique.9,10 Although effective, incremental layering was time-consuming and had its shortcomings, such as polymerization shrinkage within the bulk of the restoration, which still led to stress on the tooth and leakage at the gingival margins.7,11,12 Therefore, new materials and techniques were necessary to solve the problems often associated with posterior composite resin restorations.
Although polymerization shrinkage and marginal leakage cannot be completely eliminated, advances in material sciences and placement techniques have minimized their consequences. Demonstrating far less polymerization shrinkage than previous techniques, recent advancements in bulk-fill composites offer a new solution to an old problem.10 Because bulk-fill composites are flowable and more elastic, they can be used as a base for posterior restorations.10,13,14 Bulk-fill products also offer many added benefits, such as enabling clinicians to increase marginal adaptation in the gingival area, reduce microleakage, and counter polymerization shrinkage by decreasing stress.10,13,14 The general consensus among dental professionals is that the problems typically encountered with large-fill composite restorations are nearly eliminated by using of this new breed of bulk-fill resins.10
Rated for greater depths of fill (eg, around 4 mm), bulk-fill composites demonstrate radiopaque and translucent properties, allowing for excellent light transmission.10 Because bulk-fill materials are placed with larger quantities of material at a time, they adapt quickly to the preparation and are self-leveling to eliminate the need for excessive manipulation.10 Once in place, dentists can expect this class of materials to demonstrate reduced shrinkage rates and less stress on the tooth structure.10
A new flowable, light-curing, radiopaque nanohybrid composite, Venus® Bulk Fill (Heraeus, www.heraeus-venus.com) can be used in the posterior region and as a base for Class I restorations. For Class II and Class V restorations, Venus Bulk Fill is indicated for use in conjunction with a universal material, including Venus and Venus Diamond (Heraeus). With on-demand flow characteristics that enable the material to adapt well to preparation walls, this universal, highly translucent material can be placed in 4-mm increments. Demonstrating low shrinkage stress within the restoration and on the surrounding tooth structure, Venus Bulk Fill can be used for a variety of indications, including deep lesions and Class II restorations.15,16
Exhibiting a higher resistance to wear in contact areas, Venus Bulk Fill has a compressive strength of 331 MPa and a high flexural strength of 120 MPa. Because the material is flowable, it is much easier to completely cover the preparation floor without excessive manipulation. Also, because Venus Bulk Fill will not cure under ambient light, longer working times—approximately 80 seconds—can be expected.
Venus Bulk Fill demonstrates low polymerization shrinkage stress; therefore, the risk of postoperative gap formation, marginal leakage, secondary caries, and postoperative sensitivity are of no concern when using this product. By eliminating shrinkage issues, restorations completed with Venus Bulk Fill have proven to be durable and long lasting, without the need for incremental layering techniques.
The material is more cost-effective per restoration than traditional resin-based composites because it enables easier and faster restorative solutions. With a high radiopacity of 300%-Al, the material also is much easier to detect on radiographs. The combination of these characteristics and that the dentists can fill in 4-mm increments suggest that Venus Bulk Fill is a more efficient filling method, with fewer steps for the dentist and decreased chairtime for the patient.
A patient presented with a direct composite resin veneer in the maxillary first premolar (Figure 1). Upon clinical examination, recurrent decay was discovered in the mesial area of the tooth (Figure 1). The treatment plan included restoration and retreatment using Venus Bulk Fill. The patient was anesthetized with a 1:100,000 hydrochloride with epinephrine local anesthetic. Isolation with a rubber dam was achieved, and the following treatment protocol was undertaken.
Initial preparation was completed with a carbide bur. A round bur was used to remove all carious tooth structure. To ensure an anatomically correct and tight contact, a matrix (Composi-Tight 3D®, Garrison Dental Solutions, www.garrisondental.com) was placed around the preparation (Figure 2). An adhesive bonding agent (iBOND® Self Etch adhesive, Heraeus) was applied and rubbed thoroughly around the preparation, then gently air-dried (Figure 3). The bonding agent underwent a 20-second cure with an LED curing light.
A flowable, light-curing, radiopaque bulk-fill material (Venus Bulk Fill) was placed in the preparation, making sure to keep the tip of the material submerged while filling the restoration. The bulk-fill material was placed into the dentin/enamel junction. Note that Venus Bulk Fill self-adapts to the cavity preparation (Figure 4). Immediately following placement, the bulk-fill composite was light-cured for 20 seconds. A universal composite (Venus) was applied to further develop the restoration replacing the enamel layer (Figure 5). The restorative composite was light-cured for 20 seconds (Figure 6). The matrix was removed, and the restoration was contoured and polished (Figure 7).
With qualities such as low polymerization shrinkage rates, exceptional handling qualities, and radiopacity—which allows a clear image of the restoration upon completion (Figure 8)—Venus Bulk Fill composite offers many benefits over previous materials.1 The ability to restore in bulk saves substantial procedural time for dentists and chairtime for patients.1 When restorations are provided using these techniques and materials, dentists can predictably place functional and clinically sound restorations, and patients can receive the highly esthetic and long-lasting treatments they expect.
1. Ruiz JL, Mitra S. Using cavity liners with direct posterior composite restorations. Compend Contin Educ Dent. 2006;27(6):347-351.
2. Sarrett DC. Clinical challenges and the relevance of materials testing for posterior composite restorations. Dent Mater. 2005;21(1):9-20.
3. Christensen GJ. Remaining challenges with Class II resin-based composite restorations. J Am Dent Assoc. 2007;138(11):1487-1489.
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13. Van Ende A, De Munck J, Mine A, et al. Does a low-shrinking composite induce less stress at the adhesive interface? Dent Mater. 2010;26(3):215-222.
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15. Wieczkowski G Jr, Joynt RB, Klockowski R, Davis EL. Effects of incremental versus bulk fill technique on resistance to cuspal fracture of teeth restored with posterior composites. J Prosthet Dent. 1998;60(3):283-287.
16. Lazarchik DA, Hammond BD, Sikes CL, et al. Hardness comparison of bulk-filled/transtooth and incremental-filled/occlusally irradiated composite resins. J Prosthet Dent. 2007;98(2):129-140.
About the Author
Ross W. Nash, DDS
Huntersville, North Carolina