Written by Jeff T. Blank, DMD Thursday, 13 March 2014 12:40
During the past 10 to 12 years, significant advances have been made in dental composite resin technology. Among these improvements have been the introduction of various filler materials, filler size, loading and aggregation, resin monomers, and methods of adhering filler particles to the resin matrix. In addition to increasing the physical properties, color stability, and degree of conversion of the composite formulation, contemporary composite materials conduct, reflect, and refract visible light similar to natural tooth structure and are capable of generating seamless, highly aesthetic dental restorations. However, regardless of these modern improvements, it remains incumbent upon the dental clinician to utilize appropriate post-placement finishing and polishing techniques to yield restorations that biomimetically generate the desirable surface luster. Untoward surface irregularities resulting from poor finishing and polishing may lead to the accumulation of plaque, recurrent decay, chronic gingival inflammation, and staining by chromagenic foods and beverages—all of which shorten the efficacy and durability of even the most meticulously placed composite restoration.
This article offers a brief review of contemporary finishing/polishing materials and techniques, introducing a novel product designed to expedite the process and permit easier access to difficult-to-reach areas.
A Brief Review
Prior to discussing various materials and techniques for finishing and polishing dental composites, it is important to clarify the steps and terms used to define the procedures. Lutz et al1 describe the 4 essential post-placement steps as: (1) gross finishing, (2) contouring, (3) fine finishing, and (4) polishing. Before a clinician can properly utilize any material or technique, it is imperative to understand that each of these individual steps must be properly executed to completion prior to moving on to the next. In general, the progression is from coarse, medium, fine, to super-fine, and to omit one or more of these steps typically brings about inferior results.
Gross finishing is defined as the expeditious removal of gross excess, superfluous composite material that typically results from overfilling the cavity form or aesthetic restoration. This step is typically accomplished with coarse or medium grit diamond burs or 8- to 12-fluted carbide finishing burs in a high-speed handpiece. Coated Mylar abrasive systems in the form of discs or strips (such as Sof-Lex XT Discs and Strips [3M ESPE], PoliPro Discs [Premier Dental Products], and Super Snap Finishing Discs and Strips [Shofu Dental]) offer coarse and medium grits (100 µm or greater) that can also be effective for gross finishing, particularly in large planar surfaces and tight interproximal areas. Some clinicians may utilize bonded abrasive systems (such as Enhance [DENTSPLY Caulk]; Diacomp Composite Polishing Kit [Brasseler USA]; and FlexiCups, Discs, and Points [Cosmedent]) that are typically elastomeric materials in which the abrasive particles are evenly distributed, and which come in the form of points, cups, or discs.
Contouring is defined as the creation of the final aesthetic and functional form of the restoration and readying the surface for fine finishing and polishing. In anterior and posterior direct composite restorations, the contouring step involves the establishment of outline form, surface morphology, marginal adaptation, and proper occlusion. Contouring should not alter the cavosurface margin or surrounding healthy tooth structure. Therefore, medium to fine rotary diamonds and/or 12- to 16-fluted carbide burs used at lower speeds (30,000 to 40,000 rpm), as well as medium grit coated and/or bonded abrasive systems (40 to 60 µm) are highly useful. In the author’s opinion, failure to progress from the coarse instruments used in gross finishing to medium to fine instruments during contouring is common in a busy dental practice, and destroys the possibility of creating a durable luster, regardless of the system used. While numerous one- or 2-step polishing systems are available and often effective, their efficacy is predicated on adequate gross finishing and contouring prior to utilization.
Fine finishing can best be described as the first step in creating luster and involves the removal of scratches and defects left by gross finishing and contouring. While gross finishing and contouring by definition alter the shape and form of the restoration, fine finishing does not. The key objective of fine finishing is to improve surface smoothness sufficiently enough to ready the composite surface for the creation of a high luster. Typical instruments employed in fine finishing include fine and super-fine diamond finishing burs (25 to 15 µm diamond particles), 16- to 24-fluted carbide finishing burs, and medium-fine sandpaper abrasives and silicone-based materials with grit sizes ranging from 600 to 1,200 µm.
Polishing is the final step(s) in creating a high luster or shine. Once fine finishing is accomplished, all that remains is to buff the composite surface to free it from microscopic irregularities and voids. Typically, ultrafine abrasive systems with particle sizes of 8 µm or less are utilized, and the motion and pressure of the stroke are as important as the material used. While super-fine diamond (less than 15 µm) and 24-fluted carbide burs can be effective, the majority of dentists utilize sandpaper discs and silicone-based materials (grit sizes greater than 1,200 µm) to polish restorations, based on access and convenience. When clinicians desire an extremely glossy surface, numerous loose-particle systems or polishing pastes (such as Enamelize [BISCO Dental Products], Prisma Polishing Paste [DENTSPLY Caulk], and Diamond Twist SCO [Premier Dental Products]) are available in conjunction with felt buffs, goat hair wheels, or synthetic fiber brushes, wheels, and points.
Current Challenges With Finishing and Polishing
While many clinicians are proficient in the utilization of rotary fine diamond and carbide finishing burs, the dexterity, “touch,” or “feel” required when using these instruments prove difficult for some practitioners, particularly at high rotational speeds. In a study on finishing and polishing of composite restorations conducted by Fruits et al,2 several diamond and carbide burs as well as coated and bonded abrasive systems were evaluated along with the respective motions and axis of rotation. They concluded that overall, the best results were created when clinicians utilize the planar approach (perpendicular to the surface being smoothed) compared to the parallel rotary or circular motion commonly utilized with burs and often silicone impregnated points and cups. Sanding discs (such as the Sof-Lex Finishing and Polishing System [3M ESPE]) are popular for this reason, but are primarily indicated for large planar surfaces and interproximal zones of anterior and posterior teeth.
Posterior Composite Finishing and Polishing
The most common direct composite restoration placed in a contemporary dental practice is a direct posterior composite, and the occlusal surfaces of posterior teeth pose a unique challenge for fine finishing and polishing due to the inherent undulating in/evaginations, pits, and fissures. While the degree of polish or high luster required for these restorations can be debated, it remains imperative that the surfaces of these restorations must be finished sufficiently to resist recurrent decay caused by food and plaque accumulation as well as unsightly stain accumulation.
While rotary diamond and carbide burs are available in shapes designed to access these areas, they are best used at low speeds (5,000 to 15,000 rpm) and the time and skill required to sequence through various grits/flutes without damaging the surrounding tooth structure proves impractical for some practitioners.
Numerous bonded abrasive systems (ie, silicone-based cups, discs, and points) have, in theory, been designed to access posterior pits and fissures. These systems are generally categorized as multiuse or single-use instruments, with the former designed to endure either heat or chemical sterilization procedures. (Examples of multiuse systems are Diacomp [Brasseler USA], Politip [Ivoclar Vivadent], and Jazz [SS White Burs]. Examples of single-use systems are Enhance/Pogo [DENTSPLY Caulk], UltraGloss [Axis|SybronEndo], and OneGloss PS [Shofu Dental]). Both categories typically offer small flame- or bullet-shaped points, cups, and knife edge wheels, and some are suited for accessing the undulating pits, fissures, cuspal inclines, and slopes of posterior occlusal surfaces. In the author’s opinion, the finishing and polishing efficacy of either category is predicated on the durability and flexibility of the fine point or edge.
|Figure 1. Recurrent caries on teeth Nos. 17 and 18.||Figure 2. Selective etching of the enamel.|
|Figure 3. Application of adhesive (Scotchbond Universal Adhesive [3M ESPE]).||Figure 4. The solvents were volatilized with oil-free air for 5 seconds.|
|Figure 5. The adhesive was light cured.||Figure 6. Application of the composite resin increments (Filtek Supreme Ultra; Body Shade B1B [3M ESPE]) restorative.|
While multiuse systems are attractive for obvious reasons, they are typically more expensive than single-use products. And once the fine edges have been degraded and/or the flexibility of the elastomeric substrate has been lost from chemical or heat sterilization, the system is rendered useless, hence the rationale for manufacturers to offer single-use, disposable systems that are designed to maintain shape and flexibility for one to 3 restorations in a single operative visit and discarded.
Given the findings in the study conducted by Lutz et al,1 which showed that polishing systems that utilize a planar or perpendicular approach and motion were superior to rotary instruments like burs, cups, and points designed to polish parallel (on the “sides” of the instrument) to the surface, the practicality and efficacy of using these instruments on posterior occlusal surfaces can be questioned. Combined with the dilemma of fast point or knife-edge deterioration with use, alternative instruments such as conventional prophy bristle brushes (for example, Crescent/Rinn [Buffalo Dental], and aluminum oxide impregnated brushes, such as Jiffy Brushes [Ultradent Products] and Astrobrushes [Ivoclar Vivadent]) are frequently utilized. At slower speeds (8,000 to 15,000 rpm), these brushes are capable of accessing narrow fissures and pits more effectively than some elastomeric materials, but are mostly incapable of fine finishing and at best create a moderate-high luster.
A New Finishing and Polishing System
Recently, a novel system called Sof-Lex Spiral Finishing and Polishing Wheels has been released by 3M ESPE. This system offers a solution for finishing and polishing for not only posterior composites, but all classes of direct and indirect composite restorations, resin-modified glass ionomers, and bis-acrylic temporary materials.
Sof-Lex Spiral Wheels represent a hybridization of elastomeric impregnated points, cups, wheels, and brushes with the approach, convenience, and efficacy of sandpaper discs. It is a 2-step, disposable system in which the darker (tan) wheel is designed for finishing or removal of coarse scratches and irregularities, and the lighter (white) wheel is designed to achieve a high luster or polish. The unique wheel design employs 2 parallel rows of 15 individually radiating elastomeric “bristles” uniformly impregnated with abrasives. Wheels pop on to the same mandrel as the Sof-Lex sanding discs. The primary objectives of this technology are to create a design that provides a continuous supply of mineral to the work surface, regardless of approach angle or side of the instrument used; offer appropriate grits in a flexible form that can adapt to nearly every surface of a restoration; and minimize heat formation and build-up to permit visualization without the need for water coolant.
|Figure 7. Refinement of margins and anatomy with a diamond bur (Diamond Composite Finishing Kit [Komet USA]).||Figure 8. The polishing (white) and finishing (tan) wheels (Sof-Lex Spiral [3M ESPE]).|
|Figure 9. Removal of scratches and irregularities with the Sof-Lex Spiral finishing wheel.||Figure 10. Creating a natural luster with the Sof-Lex Spiral polishing wheel.|
|Figure 11. The completed restorations, as seen at one week postoperatively.|
Given the predilection for dentists to use silicone/elastomeric points and cups and/or bristle brushes with or without polishing pastes, this new system combines the best of both, and simplifies finishing and polishing into 2 efficient steps. The planar or perpendicular approach has proven to generate superior results compared to the rotary or parallel approach required by fine burs and abrasive points, cups, and discs. Additionally, the “bristle” arrangement accesses tight interproximal spaces, pits, and fissures more effectively. The spiral wheels are designed for use at low speeds (10,000 to 20,000 rpm) and the unique, patented design easily adapts to concave and convex surfaces using either side, with the tips of the bristles providing flexibility of use.
The following case report demonstrates the use of this system for fast, efficient, and predictable placement of a direct posterior composite restoration.
The patient presented with recurrent decay around failing composite restorations on teeth Nos. 17 and 18 (Figure 1). Following removal of the restorations and recurrent caries, an equal mixture of enamel and dentin remained on the preps.
A universal adhesive (Scotchbond Universal Adhesive [3M ESPE]) was utilized in a selective-etch mode in order to maximize bond strength to the enamel. After the etchant was applied to only the exposed cavosurface enamel for 15 seconds (Figure 2), it was rinsed with an air/water spray and dried. Adhesive was then applied to both the enamel and dentin surfaces for 20 seconds (Figure 3). Next, a stream of oil-free air was used for 5 seconds to evaporate the water/ethanol solvents and to ensure that the adhesive was evenly dispersed (Figure 4). The area was then light cured (Elipar S10 [3M ESPE]) for 10 seconds (Figure 5).
Filtek Supreme Ultra Shade B1B (Body Shade B1 [3M ESPE]) was then layered into the preparation in 2 vertical increments (Figure 6), and each increment was then light cured for 10 seconds. The optical properties of Filtek Supreme permitted seamless blending of the restorative material with the surrounding cavosurface margins of the natural tooth. Anatomic contouring and margin refinement was accomplished with a series of diamond composite finishing burs (Diamond Composite Finishing Kit [Komet USA]) (Figure 7). Following this, the rubber dam was removed and the occlusion adjusted.
The darker tan-colored Sof-Lex Spiral finishing wheel was used at a low speed to finish the restoration and remove scratches and marred finish (Figures 8 and 9). The white Sof-Lex Spiral polishing wheel was then used to create a gloss-like luster (Figure 10). As seen in the one-week postoperative view (Figure 11), the final restoration was smoothly polished with detailed morphological features intact.
The pits and fissures found in posterior teeth can make finishing and polishing direct composite restorations with traditional silicone and sanding instruments challenging. The finishing and polishing system used in this case has the flexibility and versatility of sandpaper discs, along with an ability to reach into tight spaces in both anterior and posterior applications, giving dentists an efficient tool for finishing and polishing.
- Lutz F, Setcos J, Phillips R. New finishing instruments for composite resins. J Am Dent Assoc. 1983;107:575-580.
- Fruits T, Miranda F, Coury T. Effect of equivalent abrasive grit sizes utilizing differing polishing motion on selected restorative materials. Quintessence Int. 1996;27:279-285.
Disclosure: Dr. Blank was granted an honorarium from 3M ESPE for writing this article.
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