Putting Material Science to Work: Use of a Self-Polishing, Universal Nanohybrid Composite

Robert A. Lowe, DDS


After more than 30 years of clinical use, there are few materials in dentistry that have undergone the continuous evolution that composite resin has ex­perienced. Restorative dentistry changed forever when successful bonding to enamel and dentin was achieved. Since then, one goal of clinical and material science has been to simplify the placement process of composite resin. Unlike dental amalgam, which is not affected by moisture and can be rapidly condensed and carved into a finished restoration, the placement of composite requires many more steps and fastidious technique to achieve optimal clinical results. The process of bonding, conditioning the tooth surface, application of primers and adhesives, followed by the layering of composite resins to complete the restoration, involves many independent steps that must be carefully executed to ensure good clinical outcomes.

The Search for the “Ideal” Direct Tooth-Colored Restorative Material
Many of today’s composite resins have been touted as “universal restorative materials” with anterior and posterior clinical applications. However, there has always seemed to be a trade-off when it came to the physical properties of wear resistance and the ability of the material to polish well and maintain a high luster. For this reason, many dentists still revert to the “gold standard” microfill composite for anterior application when high luster and aesthetics are required, and use a different material (with better physical properties) to restore posterior teeth because aesthetics is deemed not as important for the teeth “we don’t see.” Nanotechnologies have made significant strides, yet polishability and luster retention are still 2 clinical parameters in which inconsistency remains for many “universal” composite materials.

Figure 1. A preoperative occlusal view of the mandibular right first molar. There was a marginal defect in the distolingual area of the existing direct composite, so it was decided to replace the restoration to seal the margin. Figure 2. After removal of the old restoration, a small fracture line was noted on the pulpal floor in the area of the distolingual cusp. While there was still supportive dentin surrounding the cusp, the patient was told that this tooth may require a more extensive restoration in the future. One of the advantages of bonded restorations is that the new direct composite will help stabilize the fracture by bonding to the adjacent tooth structure and the opposite cavity walls.
Figure 3. A universal adhesive (G-Premio Bond [GC America]) was used for the adhesive step of this restoration. Figure 4. A selective-etch protocol was used on the enamel margins (37% phosphoric acid for 15 seconds).

A High-Luster Composite for Posterior and Anterior Use
According to the manufacturer, it is a unique type of surface treatment of the nano inorganic fillers coupled with high density and uniform dispersion that gives G-ænial Sculpt (GC America) high wear resistance and, at the same time, helps to create a shiny surface texture like natural enamel, with high luster and beautiful aesthetics. This filler technology uses a new formulation of strontium glass, which is highly translucent, acid resistant, and radiopaque. The glass is milled down to an extremely uniform and fine particle size (200-nanometer [nm]), which is approximately half the size of previous generations of microhybrid composite materials. This small particle size is coupled with a new silanation technique to strengthen the adhesion among the glass particles, and the resin matrix improves the hydrolytic stability and durability of the composite matrix. It is this individual silanation of the 200-nm glass particles that is the key to gaining polish retention and wear resistance in one composite material. A complete 360° silanation of these particles allows them to be packed extremely close, creating a homogenous paste with no agglomeration. All this technology produces a sculptable and easily polished (self-polishing in the mouth) material that has excellent physical properties and strength for posterior applications, while at the same time has excellent aesthetic qualities for anterior applications as well.

“Morphology Is Destiny!” – H. M. Shavell, DDS
Dr. Harold M. Shavell eloquently defined a dental restoration as “the utopian reintegration of lost morphotypia via biomorphomimickry.” To put it another way, long-term restorative and aesthetic success are made possible by the dedication of the clinician to carefully replicate natural tooth contours. The posterior direct composite resin restoration, by being a “hand-made miniature sculpture,” expresses of “the will and creativity of the dentist spatially.” The occlusal surfaces of the posterior teeth are made up of a series of elevations (cusps) and depressions (fossae), allowing the interdigitation of the opposing elements in what is termed “maximum intercuspation.” Dr. Shavell taught that the key to an understanding of occlusion is the understanding of proper dentate morphology. The mesiolingual and distobuccal cusps touch in the central fossa, while the mesiobuccal and distolingual cusps do not touch. Cuspal elements, which are not static or linear by design, are parabolic and free-flowing in form. When sculpting the occlusal surfaces of direct posterior composite resin restorations within a patient’s natural occlusion, these concepts should always be followed.1

Diagnosis and Treatment Planning

The patient in Figure 1 presented with a posterior composite restoration on tooth No. 30 that was exhibiting incompetent margins and microleakage. After clinical examination, it was decided to replace the restoration, remove any recurrent decay, and reseal the restorative margins. Figure 2 shows the preparation after removal of the old restoration. It was evident that an amalgam restoration had preceded the composite since the pulpal floor showed staining, and there were fracture lines present at the internal line angles of the preparation. At this time, the fracture lines were not deemed to be severe (deep) enough to warrant cuspal coverage, as a good amount of supportive dentin was present. Therefore, a more conservative replacement, a bonded direct posterior composite, was chosen to restore this tooth.

Clinical Protocol
A universal bonding agent (G-Premio Bond [GC America]) and a selective-etch technique was utilized in the bonding steps of the procedure (Figure 3). First, a 15-second etch (Figure 4) was done on all enamel cavosurface margins of the preparation using 37% phosphoric acid. Next, the etchant was removed with a copious water rinse for an additional 15 seconds.

Figure 5. After through rinsing for a minimum of 15 seconds, the bonding agent (G-Premio Bond) was applied to all dentin and enamel surfaces. According to the manufacturer, the amount of water in the bonding agent has been increased to dissolve and improve removal of the smear layer, while increasing the carboxylic monomer to maintain an acidic pH. Also, the amount of photo initiator has been increased to improve light-curing. The result is high bond strengths in less than 10 seconds. Figure 6. The bonding agent was light-cured (Demi Ultra [Kerr]) for 20 seconds.
Figure 7. G-ænial Universal Flow and G-ænial Sculpt (GC America) unidose tips. Figure 8. An increment of flowable resin (G-ænial Universal Flow) was placed, covering all internal aspects of the cavity preparation. This ensures uniform adaptation of the first layer of composite to the dentin and enamel of the cavity.
Figure 9. A facial view of the placement of the lingual increment of composite. Isolation was accomplished with Isolite (Isolite Systems). A plastic composite placement instrument (Goldstein Flexithin Mini 4 [Hu-Friedy]) was used to create the anatomic form of the mesiolingual and distolingual cusps. G-ænial Sculpt allows for effortless manipulation as the morphology of the occlusal surface is released by the “sculptor.” Figure 10. Once the cuspal forms are sculpted into the composite material and prior to light-curing, an artist’s brush (No. 2 Keystone Flat [Patterson Dental]) was used to further shape the anatomy, rounding off sharp corners and adapting the composite material slightly over the margin of the cavity preparation to later facilitate the finishing procedure. This virtually eliminates “white lines” after finishing.
Figure 11. A carbide composite finishing bur (FG 7901 [SS White Burs]) was used for fine occlusal adjustment and marginal finish. Care was taken not to flatten the cuspal parabolic form, but to shape the cusp into occlusal harmony. Figure 12. A pointed composite one-step polisher (Jazz Polisher [SS White Burs]) was used to place the final luster on the restoration.
Figure 13. An occlusal view of the completed restoration. Note the excellent luster exhibited from the G-ænial Sculpt material—a luster that rivals the natural enamel of teeth.

The selective-etch technique is espoused by many clinicians as it helps create a better seal of the enamel, while not removing smear layer or smear plugs on the dentin. The self-etch adhesive will modify and penetrate the smear layer, making a good bond to the dentin without the potential for postoperative sensitivity that can be manifested when using the total-etch technique inappropriately.

Universal adhesive was then applied to the enamel and dentin using a microbrush (Figure 5). It was scrubbed into the prepared surfaces for 20 seconds to ensure good penetration into the etched enamel prisms and to modify the smear layer and interact with the dentin surface of the preparation as well to form a good adhesive bond. Next, air was used to evaporate the solvent and uniformly thin the adhesive material. Once accomplished, the adhesive was light cured using an LED curing light (Demi Ultra [Kerr]) for 20 seconds (Figure 6). Figure 7 shows the materials chosen for this restoration, G-ænial Universal Flow and G-ænial Sculpt (GC America). The first increment of composite, a flowable resin (G-ænial Universal Flow), was placed to a thickness of about 1.0 mm. The flowable material uniformly covered the cured adhesive layer flowing into all the geometric irregularities of the cavity preparation (Figure 8). Once the flowable increment was cured, a lingual increment of G-ænial Sculpt was placed (Figure 9) using a composite placement instrument (Goldstein Flexi-thin Mini 4 [Hu-Friedy]). The nanohybrid compactable material maintains its shape very well as it is sculpted into the parabolic forms of the lingual cusps.

Prior to light-curing, a No. 2 Keystone flat sable brush (Figure 10) was used to gently smooth and adapt the composite material over the cavosurface margins while at the same time smoothing any sharp angles in the material. The lingual increment was light-cured, and then the buccal increment was placed, sculpted, and light-cured in a similar fashion.

The occlusion was then marked with articulating paper and adjusted using a composite finishing bur (FG 7901 [SS White Burs]) (Figure 11). Final luster was imparted using a one-step rubber composite polishing point (Jazz Polisher [SS White Burs]) (Figure 12). Figure 13 is a bucco-occlusal view of the completed BOL composite restoration on tooth No. 30. Note the exceptional luster and morphologic form of the new restoration as compared to the previous restoration shown in Figure 1. In fact, the luster of the restoration matches the natural luster of the adjacent natural enamel surface.

According to Dr. Shavell,1 “any direct restorative material placed by the dentist carries his or her personal ‘signature.’” Successful placement and long-term stability requires a combination of a knowledge of material science and artistic endeavor of the dentist. It is imperative to understand the steps necessary for proper placement and at the same time to “release the artist within” and create a dental restoration that actually resembles natural teeth. Equally important is a complete understanding of proper tooth morphology and a reproducible, systematic approach that allows the dentist to place an anatomic restoration in a reasonable amount of time. It is within the capability of all clinicians to follow this basic morphologic approach to tooth restoration.

Choosing the appropriate shades and opacities of composite material, and having a material that has excellent physical properties that can be finished to an “enamel-like” luster, the clinician can produce a dental restoration that defies detection. Being able to accomplish this can be rewarding for the dentist and very satisfying to the patient.


  1. Lowe RA. Creative artistry for crown-and-bridge provisional restorations. Inside Dentistry. 2007;3(2). dentalaegis.com/id/2007/02/creative-artistry-for-crown-and-bridge-provisional-restorations. Accessed on: March 29, 2016.

Dr. Lowe received his doctor of dental surgery degree, magna cum laude, from Loyola University School of Dentistry in 1982. Following graduation, he completed a general practice residency program at Edward Hines Veteran’s Administration Hospital. After completion of dental school, he taught restorative and rehabilitative dentistry on a part-time basis and an additional 5 years on a full-time basis at Loyola University School of Dentistry as well as building a private practice in Chicago, where he currently practices part time in addition to his full-time practice in Charlotte, NC. He is a member of Catapult Elite Speakers’ Bureau and has Fellowships in the AGD, International College of Dentists, Academy of Dentistry International, Pierre Fauchard Academy, American College of Dentists, the International Academy of Dento-Facial Aesthetics, and the American Society for Dental Aesthetics. In 2004, he received the Gordon Christensen Outstanding Lecturer Award for his contributions in the area of dental education. In 2005, he was nominated to receive Diplomate status on the American Board of Aesthetic Dentistry, an honor shared by less than 50 dentists in the entire United States. Throughout his career, he has authored and published several hundred articles in many phases of cosmetic and rehabilitative dentistry. He can be reached at (704) 450-3321 or via email at boblowedds@aol.com.

Disclosure: Dr. Lowe received honorarium support from GC America.