September 12, 2022
by Ahmad Alkhazaleh, BDS, MSc; Akimasa Tsujimoto, BDS, PhD, FIADFE
Dental fluorosis is an enamel anomaly that adversely affects inorganic phase deposition and organization causing enamel hypomineralization.1 Despite the essential effect of fluoride in remineralization of dental hard layers when used topically, a direct relationship has been established between the frequency of fluoride ingestion and its quantity during tooth development and the severity of fluorosis during tooth development and the severity of fluorosis.2 Enamel fluorosis varies according to its severity, and may affect deeper layers of enamel, causing excessive porosity that renders the enamel fragile and prone to fracture once the tooth emerges into the oral cavity.3 Clinically, this disease is manifested by the white, yellow, or dark brown stains within enamel layers that may be pitted.4
Histologically, enamel scaffold proteins, such as Amelogenin, are routinely secreted by ameloblasts and deposited within immature enamel during the secretion stage. As the maturation stage begins, these proteins are degraded by protease activity, and spatially replaced by hydroxyapatites. In the case of fluorosis, an increased level of fluoride ions (instead of calcium ions) is detrimental to protease activity, leading to protein and water molecule retention within the enamel layers; as a result, the affected enamel is low in mineral content and is porous.4
Several treatment modalities have been suggested for treating fluorosis enamel discoloration, ranging from ultra-conservative tooth bleaching to invasive full crowning of the affected teeth.4 Resin infiltration, enamel macro- and micro-abrasion, and facial veneers are other options for correcting shade discrepancy.5 Choosing the appropriate treatment depends greatly on the size and depth of the lesion, clinician experience, and patient’s choice. In mild cases, bleaching alone may provide satisfactory esthetic results as the discolored spots will “blend” better with the surrounding healthy enamel.5 Alternatively, mild to moderate cases may be approached by bleaching treatment followed by resin infiltration, enamel macro- or micro-abrasion, resin or porcelain veneers, or a combination of the above. Nevertheless, deeper lesions are more challenging, and often require more invasive procedures such as full crown coverage.4
Dental bleaching is routinely done in-office or at-home, with similar long-term success.6 Resin infiltration is a technique that utilizes a low viscosity, polymerizable resin after the external enamel surface has been treated with 15% HCl. This novel technique was initially introduced as a conservative approach in arresting incipient carious lesions.5 Over time, clinical evidence has emerged suggesting its ability in masking opacities associated with hypomineralized enamel lesions.7 In contrast to resin infiltration, micro-abrasion utilizes an acidic slurry of HCl and pumice that is actively brought into contact with affected enamel using a rubber cup rotating at a slow speed. A recent systematic review concluded that resin infiltration has the highest effectiveness in treating mild to moderate lesions, followed by bleaching, and finally micro-abrasion. Macro-abrasion simply utilizes a dental bur to eliminate the affected hypomineralized area, which is subsequently restored with a restorative material. This clinical study aimed to visually evaluate the effectiveness of home bleaching followed by resin infiltration in resolving the esthetic concerns of a patient with fluorosis-affected central incisors.
A 27-year-old female patient attended the Operative Dentistry Clinic at the University of Iowa – College of Dentistry complaining of white spot enamel opacities on her upper front teeth, mainly the central incisor teeth (Fig. 1A). There was no discomfort or history of sensitivity. Other family members had similar white spot complaints, according to the patient. Her local dentist suggested that her condition was most likely due to the high fluoride content of the drinking water. Periapical radiographs were within normal limits, and vitality testing (liquid CO2) revealed a normal response. Conservative treatment options to correct shade discrepancy included resin infiltration, enamel macro- and micro-abrasion, and/or porcelain veneers. In theory, treating white spot lesions with resin infiltration obliterates enamel pores with a material (i.e., resin) that has a refractive index closer to healthy enamel (RI=1.62) than air and water (RI of resin is 1.42; air is 1.00 and water is 1.33).
Teeth bleaching was suggested to reduce color discrepancy and enhance the blending effect between the lesion body and the surrounding enamel. The patient opted for home bleaching using 10% Carbamide Peroxide with Potassium Nitrate and Fluoride (Opalescence PF 10%, Ultradent, South Jordan, UT). Custom-made trays and home instructions were also provided at the same visit. The patient was asked to discontinue bleaching two weeks prior to her upcoming infiltration treatment appointment. Six weeks after the initial appointment, the patient returned with visually whiter teeth, but the lesions were still noticeable. (Figs. 1B, 2A-C) According to a review, a waiting period of 1-3 weeks is recommended prior to resin composite bonding to reverse the detrimental effect of any remaining oxygen on resin polymerization and bonding.8 To determine the most conservative and effective technique to address her esthetic concerns, colored filters were attached to a curing-light tip and the light was projected from the lingual, observing the color changes on the facial surface. (Figs. 3A-D) This procedure can assist the clinician in estimating the depth of the lesion, the deeper the lesion, the greater the light blockage. For deeper lesions, a combination of various treatment means may be more appropriate. In this patient’s case, the right central’s lesion is less extensive as compared to the left central’s lesion, and thus, a better outcome is anticipated. Resin infiltration was selected to treat both lesions.
A rubber dam with tight floss ligation was placed (Fig. 4A) to assist in isolation, prevent saliva contamination, and protect soft tissues from the HCl 15%. Both central incisors were polished with a non-fluoride polishing paste and a rubber cup. The resin infiltration treatment was performed according to the manufacturer’s instructions. Icon-Etch (HCl 15%) (DMG America, Ridgefield Park NJ) was applied passively onto the affected areas, with periodic massage motion for 2 minutes. Then, the surfaces were wiped with a cotton pellet to remove the acid gel, and residues were rinsed off with copious water irrigation for 30 seconds. The surfaces were then thoroughly dried with a continuous stream of oil-free and water-free air. In fact, a single application of 15% HCl on enamel surfaces can dissolve and remove 37-58µm of superficial enamel, rendering the deeper fluorosis lesion more accessible by the infiltrant.
Icon-Dry (99% ethanol) (DMG America, Ridgefield Park NJ) was applied and left on the surface to slowly evaporate, facilitating the elimination of water molecules located within the enamel porosities. Shade improvement was observed, but the process was repeated to further enhance the result. After the second Icon-Dry application, a substantial shade enhancement was observed clinically, and the TEGDMA-based Icon-Infiltrant (TriEthylene Glycol DiMethAcrylate) (DMG America, Ridgefield Park NJ) was applied onto the etched and dried surfaces and periodically massaged to enhance penetration for 3 minutes. Excess material was removed with a cotton pellet and dental floss before light curing at a minimum intensity of 800mW/cm2 for 40 seconds. The infiltration process was then repeated with only 1 minute of application time. Finishing cups and polishing discs were utilized to smooth the surfaces. (Fig. 4B) The rubber dam was removed, and the patient asked to assess her outcome. She was happy with the result and the shade modification. (Fig. 5A) At the 14 months follow up appointment, the patient expressed her great satisfaction with the result and agreed that no further treatment was needed. (Fig. 5B)
A combination of home bleaching and resin infiltration were used in this case to successfully resolve anterior white spot fluorosis with a 14 month follow up indicating both color stability and patient satisfaction. Dental fluorosis is an increasingly prevalent phenomenon. According to a Centers for Disease Control and Prevention (CDC) website review paper,9 the prevalence of fluorosis in 2011-2012 has doubled from 30% in 2001-2002.8 This rapid increase in fluorosis cases, accompanied by growing public awareness and esthetic demands, requires dental care providers to be creative in offering the most conservative treatment modalities such as teeth bleaching and resin infiltration.
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About the Author
Ahmad Alkhazaleh is an Assistant Professor in the Oregon Health & Science University School of Dentistry. He obtained BDS from Jordan, and MS in Operative Dentistry and Certificate in Operative Dentistry from the University of Iowa College of Dentistry.
Akimasa Tsujimoto is an Associate Professor in the University of Iowa College of Dentistry. He obtained BDS from Japan, PhD and a Tenured Professorship in Operative Dentistry from Nihon University, and hold Visiting Professorships at Creighton University and University of Hong Kong.