ORIGINAL ARTICLE Nano/micro fluorhydroxyapatite crystal pastes in the treatment of dentin hypersensitivity: an in vitro study Sahar T. Taha & Hua Han & Sywe-Ren Chang & Iva Sovadinova & Kenichi Kuroda & Richard M. Langford & Brian H. Clarkson Received: 23 December 2013 /Accepted: 3 February 2015 # Springer-Verlag Berlin Heidelberg 2015 Abstract Objectives Dentin hypersensitivity (DH) is a prevalent prob- lem. This study aimed to formulate a paste using fluorhydroxyapatite (FA) crystals dispersed in different car- riers to treat DH. The ability to occlude patent dentinal tubules and to release ions was investigated. Materials and methods Twenty percent FA/sodium alginate, 40 % FA/poly(hydroxyethyl methacylate(HEMA)), and 40 % FA/poly(DMA-co-MEA) were applied to etched dentin sam- ples and examined with scanning electron microscopy (SEM) to determine the degree of tubule occlusion. Fluoride elec- trode was used to measure F release and spectroscopy to eval- uate Ca and PO 4 release. The cytotoxicity of the synthesized poly(DMA-co-MEA) gel was tested. Kruskall-Wallis test was used to test the differences in ion release between the groups. Results FA/poly(DMA-co-MEA) paste obstructed up to 80 % of the dentinal tubules, while the coverage was up to 70 % for FA/poly(HEMA) and less than 50 % for FA/sodium alginate. Fluoride and Ca release was the highest for FA/P(HEMA), 7.2 ±0.7 and 139.8±32.5 ppm, respectively. The highest concentration of PO 4 was 46.2±16.4 ppm for FA/Sodium al- ginate. No statistical significance was found. Conclusions FA/Poly(DMA-co-MEA) and FA/poly(HEMA) pastes may offer immediate short-term relief of DH because of their ability to occlude the tubules and adhere to wet dentin surfaces. The release of the F, Ca, and PO 4 ions may offer long-term relief by forming a mineral barrier both within the dentinal tubules and on the dentin surface. Clinical significance The tested materials may offer a long- term treatment for DH. Keywords Dentin hypersensitivity . Treatment . Nano/micro . Fluorhydroxyapatite . Fluoride release . Dentin Introduction The Canadian Advisory Board on dentin hypersensitivity (DH) [1] defined it as Ba short, sharp pain arising from ex- posed dentin in response to stimuli typically thermal, evapo- rative, tactile, osmotic or chemical and which cannot be as- cribed to any other form of dental defect or disease.^ Dentin is an innervated tissue and usually covered by enamel or cemen- tum. Once these protective non-innervated layers are lost, pa- tients will start feeling sensitivity. For many people, this con- dition is severe. DH seems to be a common condition among adult population with prevalence values ranging from 1.34 to 98 % [2–7]. The diversity in the reported prevalence values is primarily attributed to the difference in the methods used to diagnose DH and the selected cohorts. Questionnaires and clinical examination were the methods most commonly used. Studies that relied on questionnaires only to diagnose DH yielded higher values of prevalence than those combined with clinical examination [8, 9]. S. T. Taha Department of Conservative Dentistry, The University of Jordan, Amman, Jordan H. Han : I. Sovadinova : K. Kuroda Biologic and Materials Sciences Department, University of Michigan, Ann Arbor, MI, USA S.<R. Chang : B. H. Clarkson Cariology, Restorative Sciences and Endodontics department (CRSE), University of Michigan, Ann Arbor, MI, USA R. M. Langford Cavendish Laboratories, University of Cambridge, Cambridge, UK S. T. Taha (*) 1000 Shady Creek Pl, Danville, CA 94526, USA e-mail: shr_taha@yahoo.com Clin Oral Invest DOI 10.1007/s00784-015-1427-2