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Reliable Composite Restorations for Primary Teeth
Follow this proven method to create restorations that will please young patients and their parents.
The attitude that restoring primary teeth is only a temporary measure is an enduring myth (Table 1). While it is, of course, a valid point that primary teeth have a finite lifespan, restorations for these teeth must be placed with the same meticulous care as for permanent teeth. The primary teeth that most commonly require restoration are the molars, which typically exfoliate at age 11 to 12. Therefore, depending on the age of the child, these should have an expected lifespan of anywhere up to 10 years. Given that (1.) caries progression in primary teeth is much more rapid than in the permanent dentition; (2.) children’s cooperation level varies; and (3.) placing the initial restoration with unpredictable behavior may well be challenging enough, the author wonders why any dentist would want to have to go back and replace restorations or, worse, have a failed restoration lead to an extraction. Thus, decay in primary molars must be treatment planned and restored with these factors in mind.
According to Christensen, a significant number of dental practitioners have abandoned the use of amalgam for class II restorations and are relying solely on composite.1 The demand for esthetic fillings in primary teeth is on the rise. In light of the increase in demand for composite fillings and the current economic situation, it only makes sense to master the procedure in order to keep children in the practice and not in the referral bin.
Analyzing and addressing the reasons for failure can maximize the success of composite restorations. According to recent studies, the primary reasons for failure of composite restorations are secondary caries related to marginal deficiencies.2-4 To decrease marginal deficiencies, one solution is to place a layer of flowable composite on the floor of the preparation as a liner. In past literature, one version of this technique has been termed the “snowplow technique.”5 The author has modified this technique slightly; it is summarized in Table 2. The snowplow technique or modified snowplow technique used by the author for many years takes advantage of the properties of the two main materials used, a flowable composite and a paste composite. The author regards this “go to” procedure as her “bread and butter” restoration, one that serves both her and her patients well. It is simple, fast and, above all, reliable. The technique, combined with excellent materials, has been successful over the years, proving that it is indeed possible to have it all—the ability to create excellent restorations while keeping young patients and their parents happy.
Case Studies—Modified Snowplow Technique
Using examples from two case studies involving high-risk patients, the modified snowplow technique is explained below.
In Case 1, interproximal decay was present on the distal of the first primary molar and the mesial of the second primary molar (Figure 1). In Case 2, which was to be restored with a stainless steel crown, there was decay on the first and second maxillary primary molars, with the decay on the first molar decay extending into the pulp (Figure 2).
Traditional Class II preparations were completed for both cases, taking care not to overextend the buccal and lingual walls (Figure 3 and Figure 4). Next, matrices and a wedge—a VOCO Curvy wedge (VOCO America, www.vocoamerica.com) for both—were placed (Figure 5 and Figure 6). The matrices used for Case 1 were T-bands (Pulpdent®, www.pulpdent.com) that were cut into thirds (Figure 5). A Triodent V3 Ring® matrix (Triodent, www.triodent.com) was used in Case 2 (Figure 6).
Step 1—Self-Etch Adhesive
The use of self-etch adhesives, such as Futurabond® DC (VOCO), has been a great advantage for use in children. It is fast, simple, and reliable. One of the main advantages of a self-etch system is the elimination of a “wash/dry” step. The process is thereby shortened and working time is decreased. It is especially important when using self-etch adhesives to ensure that the tooth surface is completely free of any contaminants, blood, and saliva before the self-etch is applied. A contaminated tooth surface may result in impaired adhesion, open dentinal tubules, and ultimate failure of the restoration.6 The application procedure is 35 seconds from start to finish. In certain instances when a child is unable or unwilling to cooperate for an extended period of treatment time, any elimination of steps is helpful. Futurabond DC single dose is a choice product because of its ease of application, because a dry field is not absolutely necessary due to its hydrophilic component, and because its dual-cure feature (DC) allows for a complete cure even after placement of the composite. Above all, the bond strengths of Futurabond DC are comparable to those of an etch-and-rinse system.7
Clinically, the preparations are washed and dried. Futurabond DC is applied to the surfaces of the preparation and occlusal enamel and rubbed in for 20 seconds. The Futurabond DC is air-dried for 5 seconds, and light-cured for 10 seconds.
Step 2—Placement of Flowable Composite Resin
Restoration margins, among other factors, can be affected by the difference in thermal expansion between the restorative material and the tooth, polymerization shrinkage, and application methods. Microleakage can be defined as “the marginal permeability of bacterial, chemical, and molecular invasion at the interface between the teeth and restorative material.”8 An ingress of bacteria will then result in recurrent decay and ultimate failure of the restoration.9 The use of a flowable composite as a liner beneath composite paste has been shown to reduce the marginal micro-leakage.10-12 Because flowables have the ability to adapt to the restoration and flex with the tooth, microleakage is reportedly decreased.13 The flowable composite will act as a layer of “caulking.” In addition, it flows easily into areas that are too small for the heavy composite paste to reach.
The author’s choice of flowable of choice is Grandio® SO Flow (VOCO), which is a highly filled, 80.2% w/w, flowable composite. Grandio SO Flow contains up to 81% less resin than other flowable composites. The high filler content is possible through VOCO’s use of nanohybrid technology. High filler content means lower shrinkage. What this means to the clinician is that its physical properties for this application are excellent. Additionally it is radio-opaque, a distinct advantage when used as a liner, as it will not be mistaken on future radiographic examination for recurrent or residual decay. Grandio SO Flow exhibits excellent affinity to the tooth surface, which allows for an excellent seal. The flowable composite is placed in a thin layer on the gingival floor and in the area of the interproximal box. The goal is to have the flowable make up approximately 5% to 10% of the total volume of composite in the restoration.
Step 3—Placement of Composite Paste
The basis of the snowplow technique involves placement of composite paste in bulk over a thin layer of uncured flowable composite. Injection of the composite paste over the top of the uncured flowable pushes the flowable composite toward the occlusal, gingival, and interproximal areas—much like the action of a snowplow pushing out snow ahead of its plow. This action fills in any deficiencies and allows for a void-free margin. This results in the most homogeneous restoration.14 It has been shown in the cited research that the snowplow technique leads to better adaptation and decreased marginal leakage.15,16
Composite is placed in bulk to decrease the possibility of voids between layers of composite as well as to decrease placement time. An additional advantage is the elimination of layering and the inadvertent addition of bond between layers. While placing composite, many clinicians habitually dip their condensing instrument into the bond agent, which has been shown to dramatically decrease the cohesive strength of the restorations.17 Bulk-fill techniques have been reviewed, with many clinicians and researchers advocating the technique as reliable and successful.18 However, others have criticized the technique, citing an increase in polymerization shrinkage stress and untimely failure of the restoration. It is important to bear in mind that preparations in most primary teeth have a deepest point in the range of 4 mm and a small intercuspal distance. Therefore, in this situation, bulk fill is a practical and valid technique. It would be unreasonable to expect success with a very deep preparation, something that should always be considered when this technique is used. Bulk filling techniques have been advocated to show only slightly greater, and not statistically significantly more, cuspal flexure in restorations than incremental techniques.19 By placing a combination of flowable composite and paste composite, dentists can take advantage of the best qualities of both materials.
There are three excellent alternatives from VOCO. One is x-tra fil, which is a posterior multi-hybrid composite. It comes in one universal shade and can cure a 4-mm depth in 10 seconds, which is a definite advantage when treating children. The second is Grandio®, a highly filled nanohybrid multi-use composite resin with excellent wear and excellent esthetics. (Note that highly filled nanohybrid composites show the greatest wear resistance.20) The third is Grandio SO, which is the highest-filled nanohybrid and the most wear-resistant of the three composites. Figure 7 shows both molars in Case 1 restored with Grandio SO Flow and x-tra fil. Figure 8 shows the molar in Case 2 restored with Grandio SO Flow and Grandio SO. The method of placement preferred is the use of individual compules, as this allows for a controlled smooth delivery. The compule tip should be placed at the gingival-most position and pulled back slowly as the composite paste is extruded. It is important to inject the paste smoothly with steady pressure and to avoid pullback as the preparation is filled. The syringe tip should be wiped against the occlusal margin when the fill is complete. The very low polymerization shrinkage exhibited by the VOCO materials is imperative in this technique. It should be noted in this technique that the depth of the preparation must be taken into consideration. Very deep preparations will not allow for complete cure with a single-step application, and this technique should be reserved for shallower preparations, as described previously, with a depth of generally 4 mm or less.
The clinician should shape and model the restoration and light-cure. It has been suggested that bulk placement requires high-intensity light-curing.21
Step 4—Sealing the Restoration
In the final of the modified snowplow technique, a layer of flowable composite or sealant is placed over the entire occlusal surface and cured. Placement of sealant significantly decreases microleakage in restorations.22 Either Grandio® Seal, Grandio Flow, or Grandio SO Flow can be used. The “flowables” give a very esthetic result, as can be seen in Figure 9, which shows the Case 1 sealed restoration using Grandio Flow, and in Figure 10, which shows the Case 2 sealed restoration using Grandio SO Flow.
Quality materials and reliable techniques are essential for success. With so many other variables—patient compliance, moisture control, the extent of decay—it is imperative to have excellent, reliable materials and a reliable technique. Primary teeth are important; they allow children to eat without pain, to speak clearly, to grow and to smile. Children deserve the best treatment available. Dentists should always remember that the experience that children have at their dental office will stay with them for the rest of their lives. They are not just treating children; they are shaping their future and growing patients for life.
The author received an honorarium from VOCO America for this manuscript.
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About the Author
Carla Cohn, DMD
Winnipeg, Manitoba, Canada