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VOLUME 21 , ISSUE 9 ( September, 2020 ) > List of Articles


Surface Nanohardness of Normal and Fluorosed Enamel Adjacent to Restorative Materials: An In Vitro Study and Polarized Light Microscopy Analysis

Saumya Khurana, Paras Mull Gehlot

Keywords : Cention N, Elastic modulus, Equia forte, Fluorosis, Laboratory research, Nanohardness

Citation Information : Khurana S, Gehlot PM. Surface Nanohardness of Normal and Fluorosed Enamel Adjacent to Restorative Materials: An In Vitro Study and Polarized Light Microscopy Analysis. J Contemp Dent Pract 2020; 21 (9):1034-1041.

DOI: 10.5005/jp-journals-10024-2917

License: CC BY-NC 4.0

Published Online: 20-01-2021

Copyright Statement:  Copyright © 2020; The Author(s).


Aim and objective: To evaluate nanohardness of normal and fluorosed enamel in teeth restored with Cention N (CN), Equia forte (EF), glass ionomer cement (GIC), and resin composite using the nanoindentation test. Materials and methods: Eighty freshly extracted human premolars were selected. Standardized cavities were prepared on the buccal surface of normal (40) and fluorosed (40) teeth. Based on the type of the restorative material, the teeth were subgrouped into (n = 10): CN, EF, Type VIII GIC, and Tetric N-Ceram (TNC). The teeth were subjected to pH cycle (progressive caries test), which consisted of alternative demineralization (18 hours) and remineralization with artificial saliva (6 hours) for 3 consecutive days. Surface nanohardness was determined using a nanoindenter at distances of 100, 200, and 300 μm from the restoration-tooth margin. A polarized light Microscope was used to correlate the effect of remineralization on the enamel. Data were analyzed by one-way ANOVA with the Scheffe's post hoc and independent t-test. Results: Nanohardness values of the fluorosed/normal enamel adjacent to various materials in descending order were as follows: EF 3.67/2.95 GPa, GIC 3.33/3.15 GPa, CN 3.13/3.23 GPa, and TNC 1.17/1.82 GPa, respectively. Statistically significant differences were found among various materials in both types of the enamel (p < 0.05). Conclusion: Based on the nanohardness test, EF can be a better choice for restoration in fluorosed teeth, followed by CN and GIC; GIC was better in normal enamel; however, this was not significant compared to CN and EF. Tetric N-Ceram composite resin had least influence on increasing the nanohardness of the adjacent enamel. Clinical significance: The surface nanohardness of normal and fluorosed enamel can be influenced by the type of restorative material used. The results of present study deserve clinician's attention while selecting restorative materials especially in dental fluorosis.

  1. Kidd EA, Thylstrup A, Fejerskov O, et al. Histopathology of caries-like lesions created in vitro in fluorosed and sound enamel. Caries Res 1978;12(5):268–274. DOI: 10.1159/000260344.
  2. Wiegand A, Buchalla W, Attin T. Review on fluoride-releasing restorative materials — fluoride release and uptake characteristics, antibacterial activity and influence on caries formation. Dent Mater 2007;23(3):343–362. DOI: 10.1016/
  3. Angker L, Nockolds C, Swain MV, et al. Correlating the mechanical properties to the mineral content of carious dentine: A comparative study using an ultra-micro indentation system (UMIS) and SEM-BSE signals. Arch Oral Biol 2004;49(5):369–378. DOI: 10.1016/j.archoralbio.2003.12.005.
  4. Angker L, Swain MV. Nanoindentation: Application to dental hard tissue investigations. J Mater Res 2006;21(8):1893–1905. DOI: 10.1557/jmr.2006.0257.
  5. Mahoney E, Ismail FS, Kilpatrick N, et al. Mechanical properties across hypomineralized/hypoplastic enamel of first permanent molar teeth. Eur J Oral Sci 2004;112(6):497–502. DOI: 10.1111/j.1600-0722.2004.00162.x.
  6. Shetty S, Hegde MN, Bopanna TP. Enamel remineralization assessment after treatment with three different remineralizing agents using surface microhardness: an in vitro study. J Conserv Dent 2014;17(1):49–52. DOI: 10.4103/0972-0707.124136.
  7. Mann A, Dickinson M. Nanomechanics, chemistry and structure at the enamel surface. Monogr Oral Sci 2006;19:105–131. DOI: 10.1159/000090588.
  8. Zheng L, Zheng J, Weng LQ, et al. Effect of remineralization on the nanomechanical properties and microtribological behaviour of acid-eroded human tooth enamel. Wear 2011;271(9-10):2297–2304. DOI: 10.1016/j.wear.2010.11.025.
  9. Habelitz S, Marshall SJ, Marshall Jr, GW, et al. Mechanical properties of human dental enamel on the nanometre scale. Arch Oral Biol 2001;46(2):173–183. DOI: 10.1016/s0003-9969(00)00089-3.
  10. Min J, Yu P, Xu Z, et al. Investigation on the gradient nanomechanical behavior of dental fluorosis enamel. Nanoscale Res Lett 2018;13(1):347–356. DOI: 10.1186/s11671-018-2768-y.
  11. Fan H, Gao S, Liu Y, et al. The micromechanical and tribological feature of mild mottled enamel. J Mech Med Biol 2014;14(04):1–14. DOI: 10.1142/S021951941450050X.
  12. Scientific Documentation: Cention N. Available from (Accessed on December 2019).
  13. A comprehensive guide to Equia Forte. (Accessed on June 2019).
  14. Thylstrup A, Fejerskov O. Clinical appearance of dental fluorosis in permanent teeth in relation to histologic changes. Commun Dent Oral Epidemiol 1978;6(6):315–328. DOI: 10.1111/j.1600-0528.1978.tb01173.x.
  15. Hsu CY, Donly KJ, Drake DR, et al. Effects of aged fluoride-containing restorative materials on recurrent root caries. J Dent Res 1998;77(2):418–425. DOI: 10.1177/00220345980770021101.
  16. Gonzalez EH, Yap AU, Hsu SC. Demineralization inhibition of direct tooth colored restorative materials. Oper Dent 2004;29:578–585.
  17. Fischer-Cripps, Anthony C. Nanoindentation testing. Fischer-Cripps AC, ed. Nanoindentation, ch. 2 2nd ed., Springer; 2004. pp. 21–38.
  18. Hysitron, TriboIndenter User Manual.
  19. He LH, Swain MV. Influence of environment on the mechanical behaviour of mature human enamel. Biomaterials 2007;28(30):4512–4520. DOI: 10.1016/j.biomaterials.2007.06.020.
  20. Bell T, Bendeli J, Field J, et al. The determination of surface plastic and elastic properties by ultra micro indentation system. Metrologia 1992;28(6):463–469. DOI: 10.1088/0026-1394/28/6/004.
  21. Field JS, Swain MV. A simple predictive model for spherical indenter. J Mater Res 1993;8(2):297–306. DOI: 10.1557/JMR.1993.0297.
  22. Yu HY, Zheng J, Qian LM, ed. Dental Biotribology. Springer Science; 2013. pp. 75–115.
  23. Tarn LE, Chan GP, Yim D. In vitro caries inhibition effects by conventional and resinmodified glass-ionomer restorations. Oper Dent 1997;22:4–14.
  24. Glasspoole EA, Erickson RL, Davidson CL. Demineralization of enamel in relation to the fluoride release of materials. Am J Dent 2001;14(1):8–12.
  25. Dionysopoulos D. The effect of fluoride-releasing restorative materials on inhibition of secondary caries formation. Fluoride 2014;47:258–265.
  26. Alsayed EZ, Hariri I, Nakashima S, et al. Effects of coating materials on nanoindentation hardness of enamel and adjacent areas. Dent Mater 2016;32(6):807–816. DOI: 10.1016/ 03.023.
  27. Iijima M, Ito S, Nakagaki S, et al. Effects of immersion in solution of an experimental toothpaste containing S-PRG filler on like-remineralizing ability of etched enamel. Dent Mater 2014;33(3): 430–436. DOI: 10.4012/dmj.2013-224.
  28. Dasgupta S, Saraswathi MV, Somayaji K, et al. Comparative evaluation of fluoride release and recharge potential of novel and traditional fluoride-releasing restorative materials: an in vitro study. J Conserv Dent 2018;21(6):622–626. DOI: 10.4103/JCD.JCD_338_18.
  29. Gandolfi MG, Chersoni S, Acquaviva GL, et al. Fluoride release and absorption at different pH from glass-ionomer cements. Dent Mater 2006;22(5):441–449. DOI: 10.1016/
  30. Thuy TT, Nakagaki H, Kato K, et al. Effect of strontium in combination with fluoride on enamel remineralisation in vitro. Arch Oral Biol 2008;53(11):1017–1022. DOI: 10.1016/j.archoralbio.2008.06.005.
  31. Ito S, Iijima M, Hashimoto M, et al. Effects of surface pre-reacted glass-ionomer fillers on mineral induction by phosphoprotein. J Dent 2011;39(1):72–79. DOI: 10.1016/j.jdent.2010.10.011.
  32. Ten Cate JM, Buijs MJ, Damen JJM. The effects of GIC restorations on enamel and dentin demineralization and remineralization. Adv Dent Res 1995;9(4):384–388. DOI: 10.1177/08959374950090040701.
  33. Bobji MS, Biswas SK. Estimation of hardness by nanoindentation of rough surfaces. J Mater Res 1998;13(11):3227–3233. DOI: 10.1557/JMR.1998.0438.
  34. Zhou J, Hsiung LL. Biomolecular origin of the rate-dependent deformation of prismatic enamel. Appl Phys Lett 2006;89(5):1–3. DOI: 10.1063/1.2245439.
  35. Fejerskov O, Bakeum V, Richards A. Dose response and dental fluorosis Fejerskov O, Ekstand JA, Burt B, ed. Fluoride in Dentistry. Copenhagen: Munksgaard Publication; 1996. pp. 155–166.
  36. Arsecularatne JA, Hoffman M. An in vitro study of the microstructure, composition and nanoindentation mechanical properties of remineralizing human dental enamel. J Phys D: Appl Phys 2014;47(31):315–403. DOI: 10.1088/0022-3727/47/31/315403.
  37. Waidyasekera PG, Nikaido T, Weerasinghe DD, et al. Caries susceptibility of human fluorosed enamel and dentine. J Dent 2007;35(4):343–349. DOI: 10.1016/j.jdent.2006.10.008.
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