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Inside Dentistry

February 2010, Volume 6, Issue 2
Published by AEGIS Communications


Enamel remineralization behavior under coating materials via polarized light microscopy.

Rusin RP, Konly KJ, Pfarrer AM. Caries Res. 2009;43(abstract no. 41):193.

Howard E. Strassler, DMD

Abstract

The aim was to characterize remineralization behavior of enamel lesions after a toothbrushing regimen when treated with either a rosin-based fluoride varnish or an experimental resin-modified glass ionomer, where each was applied as a coating over the lesion. Extracted human molars with artificial caries-like lesions were cut longitudinally into 100 micrometer sections, photographed in the polarizing microscope (PM) first immersed in water to (nD 1.33, showing > 5% porosity) then in Thoulet's solution (nD 1.41, showing >10% porosity). Acid-resistant varnish was applied to all surfaces, leaving only the external tooth surface with lesion exposed. Three treatments were applied: untreated control group (UNTR); lesion coated with Duraphat fluoride varnish (Colgate)( DUR); lesion coated with experimental resin-modified glass ionomer EXM-713 (EXM-OVR). The sections were stored 30 days in artificial saliva (20mM NaHCO3, 3 mM NaH2PO4, 1mM CaCl2, pH 6.7), brushed with water once daily, the acid resistant varnish removed, sections imaged in PM again. The lesion body area was quantified via computerized imaging and percent remineralization calculated from the lesion area before and after treatment. Data were analyzed by one-way ANOVA and compared with t-test (= 0.05). Mean percent remineralization (SD, n) with water imbibitions was UNTR 10.1 (7.1,9)a, DUR 2.4 (2.3,10)b, EXM-OVR 6.9 (10.1,9)a,b, with Thouldet's imbibitions, UNTR 1.5 (4.8,10)b, DUR 2.9 (2.7,10)b, EXM-OVR 30.3 (21.8,10)a. With each imbibitions set, superscript letters denote groups that are not statistically different. In conclusion, a resin-modified glass ionomer coating applied over an enamel lesion resulted in significantly enhanced remineralization versus untreated control. A conventional rosin-based fluoride varnish applied over the lesion did not change the remineralization behavior versus the control. Ion diffusion through the coating, and ion release from the coating, are proposed as ion sources for the remineralization observed under the RMGI.

Commentary

Gingival recession is a predisposing factor to dentin hypersensitivity rather than a direct cause. The prevalence of dentinal hypersensitivity has been reported between 4% and 57% in the general population. Among periodontal patients, the frequency of tooth hypersensitivity is considerably higher (60% to 98%). Dentin hypersensitivity can be an early symptom for root caries. There are many different treatments for root sensitivity, including over-the-counter toothpastes and professional application paint-on products. This research study evaluated a novel material based on light-cured, resin-modified glass ionomer for application to sensitive root surfaces with an additional benefit of fluoride release to reduce the potential of root caries in that region. This site-specific, durable protective coating has the benefits of a light-cured glass-ionomer- sustained fluoride and calcium release that is superior to fluoride varnishes. This experimental product was introduced as Varnish XT (3M ESPE).

About the Author

Howard E. Strassler, DMD
Professor and Director of Operative Dentistry
Department of Endodontics, Prosthodontics and Operative Dentistry
University of Maryland Dental School,
Baltimore, Maryland


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