Class V composite restorations are placed every day in the restorative dental practice. Whether the cause is dental caries or abfraction, this area of the tooth can be deceptively difficult to restore in a predictable fashion. Because of the proximity of the cervical third of the tooth to the alveolar bone (fulcrum), the gingival margin of any restoration can undergo a considerable amount of flexure during the masticatory process. This stress concentration can be a problem, particularly in patients who clench and/or grind their teeth. Since enamel is brittle and dentin is resilient, the enamel in this area can cleave, forming a “notch-like” abfracted area. Without treatment, these abfraction lesions can progress toward the center of the tooth, and eventually weaken the entire (natural) clinical crown. Long-term restoration of this area is difficult because of the continued stress on the gingival margin of the restoration that is bonded to dentin (root). Therefore, a restorative material that can release protective ions can potentially help protect these areas of the restoration that are so prone to recurrent caries and ultimate restorative failure.
|Figure 1. A facial view of a Class V abfraction lesion on tooth No. 5.||Figure 2. Microabrasion was used (PrepStart [Danville Materials]) to make the abfracted dentin more micromechanically retentive for adhesive materials.|
|Figure 3. The Comfort Prep System (SS White Burs).|
Prep Design: Reducing the Effects of Occlusal Stress
In order to minimize the effect of occlusal stress on the performance of the Class V composite restoration, the preparation must be made more retentive.
Increasing the bevel on the enamel portion of the preparation to extend to the middle third of the tooth will: (1) maximize the amount of micromechanical retention to enamel so the effects of flexural stress on the restoration will be minimized, and (2) allow the composite material to better blend aesthetically with the natural tooth surface eliminating the typical “kidney bean” appearance of most Class V composite restorations.
In addition, placing a retentive groove at the gingivo-pulpal line angle similar to what was done to retain Class V amalgam restorations will help decrease flexure of the gingival margin during function.
GIOMER: A Class of “Smart” Composites
Marginal breakdown and recurrent decay have always been steps of the processes by which many dental restorations ultimately fail. Aside from placement technique, another challenge for long-term clinical success of a dental restorative is to find a mechanism by which the restorative material itself can slow down, or even prevent this process. Glass ionomer (GI) materials are known for their release of fluoride ions and their ability to help remineralize demineralized tooth structure. The limitation of the fluoride release has always been that, because of the solubility of the material in the oral environment, there is a short/finite amount of time that this protection can be available. Also, aesthetics is a concern when GI is used as the restorative material in Class V cavities.
Based on information from the manufacturer, GIOMER (Shofu Dental) products are composite materials recognized by their exceptional surface pre-reacted glass (S-PRG) filler. The S-PRG filler’s glass core is pre-reacted with a polyacrylic acid solution. The GI phase in GIOMER fillers is secure from water sorption and material degradation by a surface modified layer. This results in an ion exchange from a composite material that contains GIOMER technology, which has the capability to help neutralize acids that are the product of bacterial metabolism, and these acids are the direct cause of tooth demineralization and decay for lengthy periods of time. BEAUTIFIL Flow Plus (Shofu Dental) is a material currently on the market that incorporates GIOMER technology. GIOMERs can give the benefit of ion exchange similar to GI cement, which can be especially important in patients that are prone to developing caries.
“Smart” Cavity Preparation With the Comfort Prep System
Reducing the operative armamentarium and increasing efficiency at the chair can save both time and money while not compromising the restorative result. In a changing economic climate, each dentist must find a way to maximize chair time when financial reimbursements for many routine restorative procedures are shrinking. Fissurotomy burs are part of the Comfort Prep System (SS White Burs). This minimally invasive preparation system has 2 distinct advantages over traditional preparation protocols: (1) minimally invasive outline and convenience forms of the cavity preparation can be instrumented in enamel without the use of anesthesia, and (2) carious lesions in dentin can be instrumented with Smart Bur II (SS White Burs) polymer burs, oftentimes without any local anesthesia. This approach can create a more pleasant patient experience as well as expedite treatment times in the busy dental practice.
Fissurotomy burs (SS White Burs) are commonly indicated for use in making conservative Class I cavity preparations for minimal carious lesions and for opening fissures prior to placement of enamel sealants. Another excellent use for this bur, which will be demonstrated in this article, is in preparing a Class V cavity for a restoration. For this application, a fissurotomy bur will be used to place auxiliary retention in the cervical portion of the lesion (preparation) to lessen the effect of flexural stress on the cavosurface margin of the restorative material. For those Class V lesions that have caries, another bur included in the Comfort Prep System, the Smart Bur II, is used to excavate the decay. Because of the specific hardness of this unique polymer bur, it will only remove carious dentin. When it encounters healthy (hard) dentin, the flutes become dull and the bur will stop cutting. Studies conducted at New York University School of Dentistry concluded that 85% of the patients who had Smart Bur II used for caries excavation could tolerate the procedure well without the use of local anesthesia. Completing the preparation, the enamel in the middle third of the tooth adjacent to the occlusal margin of the lesion is easily beveled with a coarse, tapered diamond, completing the preparation phase of treatment.
Case 1: Class V Abfraction Lesion
The patient in Figure 1 presented with a typical abfraction lesion due to occlusal stresses. This area is not hypersensitive, so the clinical decision was to either keep the area under observation or to restore the lesion with an appropriate restorative material. Of course, the source of the occlusal stress should be determined and treated if possible; however, it is the author’s opinion that restoring these areas will at least provide a “cushion” to prevent (or lessen) continual damage from the occlusal trauma. Abfraction lesions do not typically need much preparation, but the dentin in these areas is not particularly good dentin to bond adhesive materials. For this reason, some clinicians will choose to use a GI material that will better seal the dentin. Then, a layer of composite material is added over the GI dentin replacement to improve the aesthetic appearance of the restoration.
As shown here, in another approach, the dentin in the abfraction lesion was made more microretentive using a microetcher (PrepStart [Danville Materials]) with 25-µm aluminum oxide powder (Figure 2). Next, a fissurotomy bur (SS White Burs) was used at the gingivo-pulpal line angle of the lesion in dentin, to make a retentive trough/groove across the entire mesio-distal width of the lesion (Figures 3 and 4). A coarse tapered diamond (Piranha Diamond SE8F [SS White Burs]) was then used to bevel the enamel from the occlusal margin of the abfraction lesion to approximately the junction of the middle and occlusal third of the facial surface (Figure 5). Once the preparation was complete, a 7th generation self-etching bonding agent (BeautiBond [Shofu Dental]) was applied to the enamel and dentin surfaces according to manufacturer’s instructions then light cured for 20 seconds. In this case, BeautiBond was chosen because studies have shown it will produce better bond strengths to enamel than many of the traditional 7th generation self-etching adhesives. Total-etch adhesive bonding was not done because the placement of 37% phosphoric acid in approximation with the gingival tissue may have caused irritation and bleeding, which would have contaminated the preparation surfaces during the restorative process. BEAUTIFIL Plus – F00 (Shofu Dental) was used, and it represents a good choice for the first composite layer of a Class V restoration because the high viscosity flowable material will “wet” and flow precisely into the preparation without running or slumping prior to light curing (Figure 6). A nanomicrohybrid layer (BEAUTIFIL II [Shofu Dental]) was placed and contoured over the cured flowable layer to create a convex cervical profile near the gingival tissue. It was thinned out over the length of the beveled enamel surface to seamlessly blend into the enamel in the middle third of the tooth (Figures 7 to 9). After curing of the nanomicrohybrid layer, composite finishing burs (Finishing Carbide Bur No. 8903 [SS White Burs]) and abrasive finishing discs (Composite finishing and polishing kit No. 18220 [SS White Burs]) were used to contour the restoration prior to starting the polishing process (Super-Snap Polishers [Shofu Dental]) (Figure 10). Figure 11 is a one-year postoperative facial photo of the completed Class V restoration.
Case 2: Class V Facial Caries
The patient in Figure 12 presented with facial caries at the mesio-facial of a previously placed Class V composite restoration on the mandibular left cuspid. A diode laser (Picasso Lite [AMD LASERS]) was used to plasty the gingival tissues, making the cervical margin of the cavity preparation more accessible. For the preparation in Figure 13, without using local anesthesia, the enamel in the carious area was penetrated using a 330-carbide (SS White Burs). Next, using a small-diameter Smart Bur II, the caries was excavated from the lesion. Again, a diode laser (Picasso Lite) was used at about 1.0 W to trough the marginal gingival adjacent to the preparation to facilitate restoration. After excavation was completed, the flutes of the Smart Bur II no longer cut the remaining dentin. At this point, since there may still be some affected dentin remaining, a bioactive liner (Theracal LC [BISCO Dental Products]) was placed to stimulate apatite formation and promote pulpal healing, while at the same time creating a moisture-proof seal over the excavated area (Figure 14). After application of the adhesive (Figure 15), the cavity was filled with BEAUTIFIL Plus – F00, light cured, and then shaped using the flame-shaped composite finishing bur from the Comfort Cavity Prep Kit (Figure 16). After use of the abrasive polishing discs (Super-Snap [Shofu Dental]), a polishing point (Jazz Polishers) was used to complete the polishing process (Figure 17).
Case 3: Replacement of Defective Class V Composite
The patient in Figure 18 had a defective Class V composite restoration in tooth No. 28 that was removed because of leakage and recurrent decay at the gingival margin. During the preparation phase, the fissurotomy bur was used to place mechanical retention (a trough) into the internal line angle of the preparation at the gingival margin. Figure 19 shows the completed Class V preparation after the adhesive procedure was completed and the flowable composite layer was placed while making sure that the retentive groove at the gingivo-pulpal line angle was completely filled. Note how the enamel bevel extended laterally to the facial proximal line angles of the tooth and followed the contour of the line angle (anatomic form) as the bevel extended occlusally to the middle third of the tooth. Not only will the extended bevel increase the resistance form of a restoration, but it will also serve to make the transition of composite to tooth less visible. As previously discussed, a nanomicrohybrid layer (BEAUTIFIL) was placed as the final increment to restore the natural cervical contour to the tooth (Figure 20). This final photo (Figure 21) of tooth No. 28 was taken after completion of the restoration. This “smart” preparation and restoration provided not only a very aesthetic (no half-moon or kidney bean-shaped restoration), but also a good functional seal to the gingival aspect of the margin that would also be protected with ion exchange and acid resistance, giving this restoration the best chance for long-term success.
The Dreaded Brown Line
One clinical dilemma that frequently arises with Class V restorations is the presence of the “dreaded brown line” at the cervical margin (Figure 22). Usually this margin is on dentin (root) so many clinicians equate the “brown line” with microleakage and recurrent decay. This is not always the case. One of the advantages of composite restorations is that they are often “renewable.” Sometimes the line can be “erased,” and if need be, restored with fresh composite. Once preparation was completed, and the brown line has been removed with a piezo scaler (Figures 23 and 24), it is apparent that microleakage and recurrent decay were not an issue. In fact, this old restoration was still clinically serviceable. Replacement of this Class V area was desired by the patient for aesthetic reasons; however, there was no “catastrophic” dentin bond failure here!
Tooth preparation, as demonstrated and described in this case report article, can create not only a better patient experience, but give the dentist an efficient and predictable way to minimally prepare teeth, excavate decay, finish, and polish composite resin restorative materials. Placing restorative materials in the Class V area can be challenging due to occlusal stresses, tooth flexure, and acid attack at the gingival margin from plaque retention. The combination of comfortable preparation, auxiliary retention, then placement of a “smart” composite that will help protect the gingival marginal seal is an excellent approach to handling Class V composites in restorative practice.
Disclosure: Dr. Lowe received honorarium support from SS White for writing this article.