Amorphous Calcium Phosphate Sealants
Remineralization of carious lesions in the enamel can be achieved with use of pit-and-fissure sealants containing amorphous calcium phosphate.
New pit-and-fissure sealants with the capacity to release calcium and phosphate because of the presence of ACP have been introduced into the dental marketplace. With the continuous introduction of new dental materials, it is important not only to research and confirm their properties, but also to propose modifications or associations that may contribute to their improvement.
Current Research
A study performed at UNESP reported the remineralization capabilities of pit-and-fissure sealants.1 Ten volunteers who wore acrylic palatal devices were enrolled in this triple-blind study with a duration of 5 days for each group: Group I—demineralized enamel slab + sealant with fluoride; Group II—demineralized enamel slab plus Aegis® (sealant with ACP, Harry J. Bosworth Company, https://www.bosworth.com); Group III—demineralized enamel slab plus experimental sealant with fluoride (ESF); Group IV—demineralized enamel slab plus experimental sealant with fluoride/ACP (ACP-F); and Group V—demineralized enamel slab (control). After the experimental period, the percentage of surface microhardness recovery (%SMHR) and the integrated mineral recovery area (ΔZ) were evaluated. The concentration of fluoride (F), calcium (Ca) and phosphorous (P) in enamel µg/mm3 ) was also determined. %SMHR and ΔZ data were analyzed statistically by analysis of variance and Tukey’s multiple-comparison test. Data referring to F, Ca and P concentration were submitted to the Kruskal-Wallis test. Significance level was set at 5%. The sealants containing ACP and/or fluoride presented a higher remineralizing capacity (%SMHR and ΔZ) than that of the control group. Aegis showed a better or similar result compared to the other sealants. For all sealants, the closer to the border in contact with the material, the higher the %SMHR value. F, Ca, and P concentrations in enamel varied according to the group. Therefore, the pit-and-fissure sealants containing ACP and/or fluoride were able to promote remineralization of artificially induced carious lesions on smooth enamel surfaces.
The margins and adjacent areas of a sealant are always critical to the sealing technique because biofilm accumulation may occur and make these regions more acidic than more distant areas, which may interfere with the remineralizing capacity of saliva.2 The results of the previously mentioned study indicate that greater enamel remineralization occurred in the regions closer to the border of the enamel slab that remained in contact with the material. These findings may be attributed to the greater ion concentration in this region and consequent incorporation of ions by the enamel,3-6 although a distant effect of the material may also promote carious lesion remineralization.5 The UNESP study showed that both fluoride and ACP were effective in providing a remineralizing capacity to the tested materials in the oral environment, even presenting different forms of apatite deposition.
The application technique of remineralizing pit-and-fissure sealant materials is easily adapted to clinical dental practice. The technique is the same as with non-therapeutic sealants and can be generally accepted by dental care providers.
Clinical Technique
In the case presented, the maxillary molar exhibited a deep pit-and-fissure anatomy (Figure 1).
The enamel surface had a patchy diffuse opaqueness often associated with molar incisor hypomineralization. This potential association would imply the need for remineralization and, therefore, the application of a therapeutic sealant material. Pumice prophylaxis was completed before acid-etching with 32% phosphoric semi-gel solution (Figure 2 and Figure 3). Proper removal of plaque is necessary for complete etching of the enamel surface. Debris removal is never complete without mechanical instrumentation. A 32% semi-gel phosphoric acid solution was applied before placement of the ACP-containing pit-and-fissure sealant material. The brush tip applicator may be used to agitate the etchant semi-gel without scrubbing the enamel surface. The sealant material may be teased into the pits and fissures with a microbrush (Figure 4). The etched enamel must be contacted carefully to prevent damage to its delicate surface.
The sealant is then light-cured for 40 seconds at a minimum of 500 mW/cm2 power (Figure 5). The output of light-curing units should be checked regularly to prevent inadequate curing of resin-based materials. Note the smooth surface and marginal integrity of the light-cured and finished sealant (Figure 6). Unlike “runny” sealants, the material did not pool into the distal pits of the maxillary molars.
Discussion
The proper application of preventive techniques demonstrates dramatic results in reducing the rate of dental caries.7 However, because the prevalence of occlusal caries is still relatively high,8,9 pit-and-fissure sealants are recommended by organized dental organizations and have been widely used in clinical practice.10 But not all practicioners regularly use pit-and-fissure sealants as often as they should11 A commonly stated reason for this is the fear of sealing over carious lesions.12,13 However, carious lesions with an intact dental matrix may be reversed and the tooth structure re-mineralized14 Research at Northwestern University in collaboration with Sao Paulista State university (UNESP, Araçatuba, São Paulo, Brazil) at the Argonne National Laboratory, Argonne, IL, tested pit-and-fissure sealants to determine their effect on remineralization15 These research studies used bovine teeth with artificially produced carious lesions. The bovine enamel samples were coated with the sealant materials and then exposed to remineralization and demineralization cycles. This technique has been validated by previous studies where the samples were exposed to four cycles a day, every 6 hours, of remineralization and demineralization solutions, and then sectioned for analysis.16,17 The synchotronic testing was performed at the Argonne National Laboratories and the microCT analysis correlated very well with the Knoop microhardness results for mineral content.18 These research studies demonstrated that certain sealant materials may actually remineralize the surface of the tooth.
Calcium and phosphate ions from saliva or other sources (eg, dentifrices, chewing gums, beverages, remineralizing solutions, and restorative materials) and fluoride from topical or systemic sources have the potential to remineralize carious lesions or minimize caries development.19 The calcium phosphate naturally present in saliva is a primary defense against mineral tooth loss.20,21 However, if only salivary calcium and phosphate were available, this remineralization would occur only in the most superficial part of the lesion, and the remainder would only remain arrested.22 The fluoride present in the oral environment plays an important role in the dental structure, as an additional method of caries control, reducing demineralization and potentiating remineralization.23 However, the effect of the fluoride ion may be limited by the availability of calcium and phosphate at the site of lesion22 or in saliva.24
Amorphous calcium phosphate (ACP) has been identified as a possible precursor in the biological formation of hydroxyapatite.25-27 Dental applications based on the unique characteristics of ACP have been introduced, as well as the improvement of its properties and associations with similar products that have anti-demineralizing/remineralizing potential.28-34 If a supplementary concentration of calcium and phosphate ions could be supplied without making fluoride insoluble, its efficiency would be increased.35,36 Therefore, the properties of calcium, phosphate, and/or fluoride ions should be evaluated in dental materials, such as pit-and-fissure sealants.
References
1. Silva KG, Pedrini D, Delbem ACB, et al. Sealants containing ACP and/or fluoride: In situ remineralization. IADR/AADR/CADR 87th General Session, Miami USA, 2009.
2. Kielbassa AM, Schulte-Monting J, Garcia-Godoy F, Meyer-Lueckel H. Initial in situ secondary caries formation: effect of various fluoride-containing restorative materials. Oper Dent. 2003;28(6):765-772.
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34. Regnault WF, Icenogle TB, Antonucci JM, Skrtic D. Amorphous calcium phosphate/urethane methacrylate resin composites. I. Physicochemical characterization. J Mater Sci. 2008;19(2):507-515.
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About the Authors
Mark Cannon, DDS, MS
Children’s Memorial Hospital
Northwestern University
Chicago, Illinois
Kélio Garcia Silva, DDS, MS, PhD
Postgraduate Student, Pediatric Dentistry
UNESP—São Paulo State University Araçatuba Dental School
São Paulo, Brazil
Denise Pedrini, DDS, MS, PhD
Professor, Department of Surgery and Integrated Clinic
UNESP—São Paulo State University Araçatuba Dental School
São Paulo, Brazil
Alberto Carlos Botazzo Delbem, DDS, MS, PhD
Professor, Department of Child and Social Dentistry
UNESP—São Paulo State University Araçatuba Dental School
São Paulo, Brazil
Lilian Ferreira, DDS
Postgraduate Student, Pediatric Dentistry
UNESP—São Paulo State University Araçatuba Dental School
São Paulo, Brazil
