Two primary goals of treating carious lesions are maintenance of as much tooth structure as possible and placement of restorations that have longevity and durability. Traditionally, occlusal caries required cavity preparations that fulfilled the concept of extension for prevention. All pits and fissures were eradicated with a bur when the tooth was prepared. These preparations were suited for placement of dental silver amalgam. When composite resins gained acceptance as a restorative material for posterior teeth, the preparations were comparable to classical amalgam preparations.
In 1978, Simonsen described a minimally invasive preparation and restoration, which he named the preventive resin restoration (PRR).1 This preparation only removed carious pits and fissures using small burs (No. 1/2 round, No. 1 round, and No. 330), with tooth removal barely into dentin, and in some cases only the carious enamel was removed. The tooth was restored using an adhesive technique with a highly filled composite resin for the prepared pits and fissures, covering the remaining pits and fissures with a sealant. Subsequent reports demonstrated the clinical efficacy of this conservative restoration.2 One problem with the preventive resin technique was it required the use of two different restorative materials.
Flowable composite resins were first described for use in restoring cervical erosion.3 In 1982 a flowable composite resin that received acceptance as a Type II ADA restorative, Rembrandt Natural (Den-Mat, Santa Maria, Calif) was introduced. As PRRs evolved, flowable composites became a logical choice to restore these lesions. This material had a viscosity that allowed it to be used for the minimally invasive preparations and also as a sealant for the untouched part of the occlusal surface. These flowable composites could be injected into a cavity preparation.3-5 Most manufacturers package these flowable composites in small syringes that allow for delivery with very small-bore needles (usually 20 gauge). This type of application of flowable composites made them ideal for use in preventive resin restorations. Some manufacturers have provided the clinician with a full selection of aesthetic shades so flowable composite resins can be used in both anterior and posterior regions.
Flowable composites also have some specific properties that must be taken into account when using them. Flowable composite resins do not have the depth of cure of other composites.6 Most manufacturers recommend that flowable composites be layered with a thickness of 2 mm and a curing time of 20 seconds with a conventional quartz halogen light. This light intensity translates to 40 seconds with a first generation LED curing light, 3 to 5 seconds with a plasma arc light, and 5 to 10 seconds with a high-intensity quartz halogen light. The viscosity of flowable composite resins varies, with some having low viscosity and others having air bubbles after dispensing that can be problematic to the resin surface.
Another physical property the practitioner should be aware of is the difference in radiopacity between brands of flowable composite resin.7 The most radiopaque flowable composite resin is Tetric Flow (Ivoclar Vivadent). A useful tip is to prepare an occlusal preparation on an extracted molar. Place a 1-mm thickness of flowable composite and light cure. Place a more highly filled hybrid composite resin over the top and light cure. Make a radiograph of the restoration to compare radiographic density. This will be useful when making diagnoses of a restoration that contains a flowable composite resin as a liner or as the first increment in the proximal box of a class II restoration. In some cases the more radiolucent flowable composite resins appear to be similar to caries. In some cases, dispensing a flowable composite resin may be difficult for a practitioner with less than average hand strength or with skeletal muscular weakness due to arthritis or another orthopedic disorder. In these cases, the clinician should look at unit dose tube dispensing instead of a syringe with a needle. Examples of unit dose tube dispensing are VersaFlo (Centrix) or Tetric Flow (Ivoclar Vivadent). A clinician should evaluate several different brands to find the one most suitable.
With the clinical success of PRRs (conservative cavity preparations restored with flowable composite resins), there have been continuing investigations concerning the most accurate means of diagnosing pit and fissure caries. Recent articles have described the difficulty of diagnosing occlusal caries.8,9 With the use of fluoride, the characteristic demineralization and carious lesion of enamel is not present. Even if enamel is clinically intact, there may be significant dentinal caries present. These lesions have been referred to as “hidden caries.” Other terms that have been used to describe this occurrence include “fluoride syndrome,”10 “covert caries,”11 and “occult caries.”12 In the United States, pit and fissure caries has been diagnosed using a sharp explorer, with the tactile determination of whether the explorer tip has “tug back.” In recent years other diagnostic methods have become available, and this diagnostic technique has come into question. The lack of reliability with the use of a sharp explorer was identified in one study where this finding was correct only 24% of the time (this means there is low sensitivity); 76% of the time that there was tug back caries was not present. The explorer tip rarely stuck in a sound fissure (high specificity).13 Today, there are several methods that can be used to assist in the diagnosis of dentinal caries at the base of a pit or fissure. These include radiographs, use of sharp explorer, caries disclosing dye, fiber-optic transillumination, electrical conduction methods, and laser fluorescence.5,14-16
For most clinicians the use of a sharp explorer and radiographs in caries diagnosis is second nature. It is important that the use of a sharp explorer for caries detection be minimized. It has been shown that the sharp tip can damage a white spot of initially demineralized enamel by breaking through and cavitating the surface. More intense use of the explorer tip, especially on the occlusal surface, can cause the initiation of a lesion.17 With the introduction of newer technologies, caries detection for pits and fissures can be more reliable. Fiber-optic transillumination is the shining of a high intensity light source through the enamel, and visualizing the shadowing that can be either enamel staining or penetrating caries. Electrical conduction uses a mild electrical current. Two probes are placed, one on the lesion and the other distal to the lesion. Based upon the current flow, a determination can be made whether a carious lesion is present. Certain devices introduced in Europe had a meter to note electrical conductance values. While reasonably reliable, these devices were not well accepted. Laser fluorescence using the DIAGNOdent (Kavo) takes advantage of the light- reflecting and fluorescing properties of altered tooth structure and those bacteria that inhabit pits and fissures. The laser light of the DIAGNOdent is at a wavelength of 655 nm. This wavelength of light demonstrates no fluorescence to sound, healthy tooth structure. On the display of the instrument, the values will be very low. In contrast, carious tooth structure has elevated fluorescence. The greater degree of caries, the higher the fluorescence with coincident higher readings in the DIAGNOdent display. The device also has an audio signal that parallels the fluorescent value readings.
In a comparison of visual and caries detection solution techniques for diagnosis of occlusal caries, visual techniques were correct only 53% of the time and caries disclosing dyes were accurate only 43% of the time.18 In another study, a comparison was made of four different techniques.19 Radiographic findings of caries were false-positive for almost 25% of cases. The use of a sharp explorer missed 25% of the caries present, and when the diagnosis was made that caries was present, the diagnosis was incorrect in 12% of cases. Caries disclosing dye was the least accurate. This technique missed 40% of the caries present, and there were 20% false-positives. The most accurate diagnostic tool was laser fluorescence (the DIAGNOdent). While 10% of carious lesions were not diagnosed using this device, there were no false positives (ie, when the DIAGNOdent noted occlusal caries, occlusal caries was present).
Better diagnosis of occlusal caries combined with the ease of filling minimally invasive preparations with flowable composites have led to improvements in preparation techniques that emphasize conservative cavity preparations. Air abrasion, while not a new technology, has seen greater acceptance for the preparation of small carious lesions.20 Air abrasion units use a fine aluminum oxide particle, and force it through a narrow tube at a high velocity. This energy allows the particles to cut tooth structure, opening suspected pit and fissure caries. Air abrasion is well suited for preparation of small carious lesions that will be restored with flowable composites,21 but is not appropriate for use in more extensive dentin carious lesions. Difficulties with air abrasion include the significant cost of the equipment, the large amount of space required in the operatory, and the need for additional equipment to adequately evacuate residual particles during preparation to avoid leaving a thin film of abrasive aluminum oxide particles on surfaces in the operatory.
Originally, smaller burs were recommended for preparing PRRs. Recently a new class of thin burs was introduced to allow penetration into pits and fissures (Fissurotomy burs, SS White Burs).22 These burs often allow the clinician to prepare the pit or fissure without the need for anesthesia. Once the preparation access has been opened and the caries explored, decisions about further extensions can be made.
In summary, the keys to success for PRRs are the ability to diagnose the presence of caries, remove the caries efficiently and effectively, and use of an adhesive technique with low-viscosity resins.
CASE REPORT
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| Figure 1. Clinical caries adjacent to occlusal sealants on the maxillary first premolar and first molar teeth. | Figure 2. Rubber dam placement. |
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| Figure 3. Small preventive resin preparations on the first premolar and first molar. |
A 22-year-old patient was seen for a recall appointment. It had been 4 years since her last dental visit. She had a dental history of small occlusal restorations and sealants. A clinical exam revealed obvious clinical caries at the margins of sealants on the maxillary first premolar and first molar teeth (Figure 1). The sealant on the occlusal surface of the maxillary second premolar was intact. After administering local anesthesia, a rubber dam was placed (Figure 2). The teeth were prepared using a pear-shaped No. 329 bur (SS White). The preparations were kept small with only the removal of the defective sealant and caries (Figure 3). These small preparations were the ideal size for use of a flowable composite resin delivered with a needle.
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| Figure 4. Teeth etched for 15 seconds. | Figure 5. Application of dentin/enamel primer. |
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| Figure 6. Thin coat of resin adhesive applied to cavity preparations. |
The teeth were etched for 15 seconds with a 25% phosphoric acid etchant (Figure 4). The tooth was then rinsed for 10 seconds with an air-water spray and dried, leaving the dentin slightly moist. Several coats of a mixed A+B primer (Tenure A+B, Den- Mat) were applied to the preparation using a microapplicator (BendaBrush Micro, Centrix) (Figure 5). When the primer was air dried, the tooth had a shiny appearance. The resin adhesive (Tenure S, Den-Mat) was then applied to the preparation in a thin coat (Figure 6). The adhesive was light cured for 10 seconds with a conventional quartz halogen light (Optilux 401, Kerr Demetron). Although not available at the time this procedure was performed, a plasma arc curing light (eg, Sapphire Xenon Power Arc curing light, Den-Mat) can be used for three seconds to polymerize the adhesive.
| Table. Partial Listing of Flowable Composite Resins | ||||||||||||||||||||||||
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The flowable composite resin selected was Virtuoso Flowable (Den-Mat). Virtuoso Flowable has a silica, barium glass filler, and is filled 50% by weight and 43% by volume. This material is easy to apply with pinpoint placement, is self-smoothing once placed (making it easy to finish and polish), is radiopaque, and releases fluoride. Its average filler particle size of 0.7 µm allows for polishability, and it has been shown to be one of the most wear resistant flowable composite resins.4 See the Table for a partial listing of flowable composite resins that are available.
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| Figure 7. Precise application of flowable composite resin to minimally invasive cavity preparations. | Figure 8. Completed flowable composite resin restorations. |
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| Figure 9. Five-year follow-up demonstrates good clinical result. |
The flowable composite resin was applied to the cavity preparations (Figure 7) and light cured for 20 seconds with the quartz halogen light (a plasma arc light would require only 5 seconds of curing6). The result was a well-sealed restoration (Figure 8). The rubber dam was removed and occlusion was adjusted. Figure 9 shows the 5-year follow-up.
It is important to remember that flowable composite resins should not be used as a replacement for sealant material in pits and fissures. Thin application of flowable resin composites will not be durable under function. For patients with fully erupted teeth in occlusion, if a flowable composite resin is desired, some preparation of the tooth is necessary to increase the bulk of the composite to improve durability and resistance to fracture. For these cases, air abrasion or a small round diamond bur can create space for the restorative material. Even with sealant placement, the clinician must apply a minimum thickness of 0.3 to 0.4 mm to achieve clinical success in sealing the occlusal surface.23
DISCUSSION
When flowable composite resins were first introduced, they appeared to be a one-dimensional restorative material for use only in PRRs. During the last few years, the clinical success of flowable composite resins for this use has been demonstrated.21 The case report described in this article is part of a long-term clinical evaluation conducted by the first author of Virtuoso Flowable (originally named FloRestore) for PRRs using Tenure MP as an adhesive. Of the 12 patients and 23 restorations that have been followed for 5 years, none have debonded, fractured, or were lost. All restorations are still functioning. Two restorations have demonstrated slight marginal staining, but there have been no cases of recurrent caries.
Today, most flowable composite resins are available in a variety of shades to manage most aesthetic clinical situations. Over the past several years there have been case reports on a variety of uses for flowable resin composites.24-35 These include:
•PRRs.
•pit and fissure sealants.
•routine class I restorations.
•small class III restorations.
•small, angular class V abfraction lesions.
•sealing ditched amalgam margins.
•repair of small porcelain fractures in nonstress-bearing areas.
•surfacing ribbon-reinforced composite resin splints.
•repairing temporary restorations and adding to margins of temporary restorations fabricated with bis-acryl composite resins.
•inner layer for class II posterior composite resin restoration (specifically for sealing the gingival margin to avoid deficiencies).
•enamel defect repair.
•repair of crown margins.
•repair of composite resin margins.
•luting porcelain and composite resin veneers.
CONCLUSION
Since the introduction of flowable composite resins in 1996, the clinical usefulness of this restorative material has been demonstrated. While the primary use of the flowable composite is for restoring small occlusal preparations, these materials have been shown to have a variety of other uses, and are now a valuable adjunct to any clinician’s restorative armamentarium.
References
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22. Hamilton JC, Dennison JB, Stoffers KW, et al. A clinical evaluation of air-abrasion treatment of questionable carious lesions. A 12-month report. J Am Dent Assoc. 2001;132:762-769.
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26. Chuang SF, Liu JK, Chao CC, et al. Effects of flowable composite lining and operator experience on microleakage and internal voids in class II composite restorations. J Prosthet Dent. 2001;85:177-183.
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31. Roberts HW, Charlton DG, Murchison DF. Repair of non-carious amalgam margin defects. Oper Dent. 2001;26:273-276.
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34. Christensen GJ. Reducing postoperative sensitivity in class I and class II resin restorations. Dental Products Report. 2001;35:94-96.
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Dr. Strassler is professor and director of operative dentistry at the University of Maryland Dental School in the Department of Restorative Dentistry. He has lectured nationally and internationally on clinical techniques and a selection of dental materials and aesthetic restorative dentistry. He is a fellow in the Academy of Dental Materials, a member of the ADA, Academy of Operative Dentistry, and International Association of Dental Research. Dr. Strassler was selected for the Weclew Honorary Fellowship for the Academy of General Dentistry in 2000. He is on the editorial boards of several journals. Dr. Strassler has published many articles in the field of restorative dentistry and has coauthored several chapters in texts. He has a general practice in Baltimore, Md, that is limited to restorative dentistry and aesthetics.
Disclosure: Dr. Strassler has conducted funded research for the Den-Mat Corporation and is a consultant to the Den-Mat Corporation.
Dr. Goodman is associate professor in the Department of Pediatric Dentistry at the University of Maryland Dental School in Baltimore, Md, and was previously the Maryland State Dental Director. He has written articles and presented on dental public health issues.
