CLINICAL PRACTICE
CASE REPORT |
JADA Continuing Education
Using microabrasive material to remove fluorosis stains
KENNETH ALLEN, D.D.S., M.B.A.,
CLAUDINE AGOSTA, B.S. and
DENISE ESTAFAN, D.D.S., M.S.
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ABSTRACT
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Background. Increased public access to fluoride has decreased the prevalence of caries and increased the prevalence of fluorosis staining. This article provides a case report involving a conservative method of removing fluorosis stain, as well as describes an in vitro test of the method.
Case Description. A healthy man sought treatment at New York University College of Dentistry for removal of severe, dark brown fluorosis staining on his anterior teeth. To remove the stain, the treating clinician used a microabrasive material, which leaves enamel intact, instead of a tooth-whitening agent, which requires removal of all affected enamel.
Methods. To demonstrate that enamel structure is not disturbed by the microabrasive material, the authors performed a study using scanning electron microscopy, or SEM. They viewed enamel structure under SEM at x1,000 magnification. They viewed untreated microabraded enamel and compared it with enamel that had been treated for 20 seconds with 37 percent phosphoric acid.
Results. An etch pattern was not discernible on the tooth treated with the microabrasive material. The enamel prisms remained intact and the cores were not exposed.
Clinical Implications. Microabrasion removes intrinsic fluorosis stain effectively while protecting enamel. In this case, an enamel shade of brown not in the range of any tooth color shade guide was reduced.
Since the origins of modern dentistry, dentists have strived to re-create the oral environment to make it more esthetically pleasing. A collaborative effort among dentists, government and local communities has been successful at reducing the prevalence of caries in the adolescent population. Public education about the negative effects of sucrose on the teeth, increased access to preventive care, governmental prevention initiatives and local communities’ fluoridation of drinking water are a few of the measures that have been taken. Communities that fluoridated their public water systems in the 1940s through the 1960s typically experienced a 50 percent reduction in caries prevalence.1
Microabrasion removes intrinsic fluorosis stain effectively while protecting enamel.
While an increased exposure to fluoride results in decreased caries, it also results in an increased prevalence of enamel fluorosis.1–3 In the United States, more than 144 million people live in areas with access to fluoridated water4; therefore, discolored dentitions are encountered in the dental office with increasing frequency.5 Dental fluorosis has become a challenge to esthetic re-creation of the oral environment.
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FLUOROSIS
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Fluorosis is a hypomineralization of enamel caused by the retention of amelogenin proteins by fluoride.6 The affected enamel does not mature and has surface and subsurface porosities.6 It can be characterized by white spots or striations on the teeth. More severe cases result in brown staining. Fluorosis staining has attracted significant attention owing to the psychological impact of unesthetic maxillary anterior teeth.7
The degree to which fluorosis creates an esthetic dental problem is related to the amount of fluoride ingested during the development of the affected teeth. The critical period for clinically significant dental fluorosis is during the second and third years of life, when the adult teeth are forming. Ingestion of more than 1 part per million of fluoride during this time may cause fluorosis.8 This can occur in children who ingest fluoride from several daily sources (such as toothpaste, rinses, supplements) and in children who swallow tooth-paste while they brush. In some countries, water fluoridation is so prevalent that the bulk of processed food and drink is manufactured with 1 ppm already contained within it.9
Diagnosis.
The differential diagnosis of dental fluorosis can be made if the defect is bilaterally symmetrical. The condition’s etiology can be toothpastes, vitamin supplements, drinks and infant food prepared with fluoridated water. These affected teeth are extremely caries-resistant, but unesthetic.6
Treatment.
In the past, restoring teeth with fluorosis could not be done conservatively. The clinician had to remove several millimeters of tooth structure to place a material with adequate thickness to hide the fluorosis stain. Some of the methods involved the use of concentrated hydrogen peroxide with heat, phosphoric acid with Superoxol (Sultan Chemists, Englewood, N.J.) and heat, sandpaper abrasion, and placement of resin-based composite restorations or laminate veneers.10–13 Tooth-whitening products cannot remove the intrinsic stain; the affected tooth structure has to be removed and a tooth-colored material that bonds to tooth structure must be placed. A study by Ateyah and Akpata14 found that the shear bond strength of resin-based composite to fluorosed enamel was significantly lower in people older than 40 years of age than in people younger than 40 years of age. This increases the chance of the restoration’s failure.
In the past, restoring teeth with fluorosis could not be done conservatively.
Other recent techniques for correcting fluorosis staining include the use of vital tooth whitening agents,10,12 as well as modified microabrasive techniques.10,15 One new microabrasive material (Opalustre, Ultradent Products, South Jordan, Utah) is a chemical and mechanical enamel microabrasion slurry containing 6.6 percent hydrochloric acid, or HCl. It is delivered via syringe for fast, easy application and provides a natural enamel "glazed" surface. The microabrasive material can correct enamel demineralization defects up to 0.2 millimeter in depth, according to the manufacturer. The approach is effective in treating defects that do not respond to regular tooth-whitening systems, again according to the manufacturer.
To provide a treatment modality that conserves enamel structure, we undertook the following case study. At the time we conducted this study, there were no other similarly formulated microabrasive materials available for our clinical trial.
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MATERIALS AND METHODS
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A healthy, 40-year-old man with severe fluorosis staining sought treatment at New York University College of Dentistry. His chief complaint was the esthetics of his smile. The clinician performed scaling and root planing. The clinician took photographs and discovered that she could not record a pretreatment shade because the staining was darker than any shade on the tooth color scales.
The clinician placed a 2- to 3-mm–wide bead of gingival tissue protectant along the contour of the free gingiva to prevent leakage between the rubber dam and gingiva. She placed a rubber dam to protect the gingiva and to prevent enamel particles from aerosolizing to the face. To prevent interaction with the 6.6 percent HCl (Opalustre), the clinician sealed existing restorations. The clinician used a 701.7F fine-grit diamond bur (Brasseler USA Dental Rotary Instruments, Savannah, Ga.) in a water-cooled high-speed handpiece and applied it to the affected enamel for five to 10 seconds. The purpose of the fine diamond bur was to roughen the enamel surface and allow for penetration of the 6.6 percent HCl. The bur was not used to remove affected enamel.
The clinician placed a 1.0-mm layer of microabrasive material on the labial surface of the affected enamel. She used a rubber cup with a minibrush inserted into the center in a contra-angle slow-speed handpiece and microabraded the tooth for 60 seconds. She then rinsed and reevaluated the tooth and performed the procedure a second time. After a desirable shade was achieved, the clinician treated the teeth with an in-office topical fluoride gel for 30 minutes. She removed the rubber dam and tissue protector, flossed the teeth and rinsed them again. The clinician then recorded the final shade achieved, which was shade A3 on the Portrait IPN Shade Guide (Dentsply Trubyte, York, Pa.).
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SCANNING ELECTRON MICROSCOPIC ANALYSIS
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To demonstrate that enamel structure is not disturbed by the microabrasive material, we then performed a study using scanning electron microscopy, or SEM. We viewed enamel structure under SEM at x1,000 magnification. We viewed untreated and microabraded enamel and compared it with enamel that had been treated for 20 seconds with 37 percent phosphoric acid.
We used three freshly extracted human noncarious mandibular central incisors in this study. We sterilized the teeth in 10 percent sodium hypochlorite. We acid-etched one tooth with 37 percent phosphoric acid for 20 seconds, rinsed it with copious amounts of water and air-dried it for three seconds. We roughened a second tooth with a 701.7F fine-grit diamond bur in a water-cooled high-speed handpiece that was applied to the enamel for five seconds. We placed a 1.0-mm layer of microabrasive material on the labial surface of enamel. Using a rubber cup with a minibrush inserted into the center in a contra-angle slow-speed handpiece, we microabraded the tooth for two minutes. Then we rinsed it with copious amounts of water and air-dried it for three seconds. The last tooth served as the control. We slightly roughened the enamel with a 701.7F fine-grit diamond bur in a water-cooled high-speed handpiece for five seconds.
We desiccated the specimens and coated them with a thin (50-nanometer) film of gold-palladium alloy within a vacuum coating unit. We then examined them in a scanning electron microscope at an accelerating voltage of 20 kilovolts and at x1,000 magnification.
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RESULTS
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Case study.
Preoperative photographs taken of the affected enamel show severe deep brown staining across the facial surfaces of the anterior teeth (Figure 1
). Postoperative photographs reveal effective penetration of the microabrasive product through complete removal of brown staining (Figure 2). The enamel still was glossy after treatment. The incisal edges of the treated teeth were reduced to shade A2, and the cervical area was reduced to shade A3. We should note that if the patient had wanted to receive a lighter final shade, he could have had the microabrasion treatment repeated or used a tooth-whitening agent.
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Figure 2. Postoperative photo of patient after treatment with microabrasive slurry, shade A3 on the Portrait IPN Shade Guide (Dentsply Trubyte, York, Pa.).
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Laboratory study.
An etch pattern was not discernible on the tooth treated with the microabrasive material (Figure 3). The enamel prisms are still intact and the cores are not exposed. This was the expected result because the enamel surface was only roughened using a fine diamond bur for five to 10 seconds. In addition, only 6.6 percent HCl was used, in comparison to 37 percent phosphoric acid, which can produce Type I and Type II etch patterns.
The control tooth of untreated enamel revealed normal patterns of enamel prisms (that is, intact peripheries and unexposed cores) (Figure 4). The micromorphological patterns of enamel prisms in Figures 3
and 4 are similar.
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DISCUSSION
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Enamel etching results in three different micromorphologic types, which can be seen with SEM.16–18 A Type I etch pattern is dissolution of enamel prism cores while the prism periphery remains intact. A Type II etch pattern is dissolution of enamel prism peripheries while the core remains intact. A Type III etch pattern contains some areas that may resemble Types I or II, but the remaining areas do not resemble enamel.
Scanning electron microscopic analysis of the tooth treated with 37 percent phosphoric acid revealed a mixture of Type I and Type II etch patterns in the enamel (Figure 5). The etch pattern exhibits a hollowing of prism cores with intact peripheral borders.10,19 Some of the peripheries also appear to be etched, resulting in a Type II pattern. Silverstone and colleagues19 found that treating enamel with 30 to 40 percent phosphoric acid resulted in very retentive Type I etch patterns.
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Figure 5. Scanning electron microscopic photo of Type I etch pattern in a tooth treated with 37 percent phosphoric acid.
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Researchers have found that microabrasive techniques using 18 percent HCl have been effective in removing intrinsic enamel stains.10,13 The technique used in this study involves microabrasion or roughening of the enamel so the 6.6 percent HCl and silicon carbide microparticles can penetrate the tooth structure. The material is applied to the affected tooth structure, and slow rotary pressure from a slow-speed handpiece helps to remove the staining.10,15
This method proved to be successful for cases involving staining that in-office carbamide peroxide cannot correct. The carbamide peroxide reacts with water to form hydrogen peroxide and free oxygen radicals. It is the free oxygen radicals that react with the enamel to release stains. Rotary pressure helps the silicon carbide microparticles in the tooth-whitening product abrade the stain and remove it. Therefore, this process is more effective at removing intrinsic stains.
Previous research showed that 18 percent HCl and pumice removed 7 to 22 micrometers and 36 to 62 µm of surface enamel on five-second and 25-second applications, respectively.20 Use of only 6.6 percent HCl in our study probably would remove less surface enamel than would 18 percent HCl, since one-third the concentration of HCl would be used. The SEM photo (Figure 3) of a microabraded or roughened tooth does not show an etch pattern. Treatment with 37 percent phosphoric acid (Figure 5) removes more enamel particles than does 6.6 percent HCl (Figure 3). The micromorphological pattern of the microabrasion-treated enamel (Figure 3) is similar to that of the untreated enamel (Figure 4).
This SEM study was conducted on enamel that was not fluorosed. However, we would expect similar findings for the micromorphological structure of fluorosed enamel. Fluorosed teeth have the highest concentration of fluoride in the outer 200 µm of enamel,14,21 and this makes them highly resistant to acid etching.14,22
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CONCLUSION
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The results of this study verify that the microabrasive material tested was an effective treatment for removing intrinsic enamel staining. The microabrasive material removed fluorosis stain without requiring removal of all affected tooth structure. Roughening of the enamel surface with a fine diamond bur was sufficient to allow penetration of the HCl and removal of the fluorosis stain without damaging the structure of enamel prisms.
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FOOTNOTES
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Dr. Allen is an assistant professor and the director of general dentistry simulation, New York University College of Dentistry, 345 East 24th St., Room 608, New York, N.Y. 10010, e-mail "kenneth.allen{at}nyu.edu". Address reprint requests to Dr. Allen.
Ms. Agosta is a fourth-year student, New York University College of Dentistry, New York.
Dr. Estafan is an associate professor and the director of esthetics, New York University College of Dentistry, New York.
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ABSTRACT
FLUOROSIS
