title: In vitro effects of nano-hydroxyapatite paste on initial enamel carious lesions.
abstract: OBJECTIVE
  The purpose of this study was to analyze the protective effect of remineralizing agents on enamel caries lesions using surface Knoop microhardness testing (KHN) and atomic force microscopy (AFM).
  
  
  METHODS
  Forty-eight human enamel blocks were assigned to four groups (N=12): (1) control (without agent); (2) fluoride varnish (Duraphat); (3) nano-HAP paste (Desensibilize Nano P); and (4) casein phosphopeptide-amorphous calcium phosphate (CPP-ACP) paste (MI Paste Plus). Incipient caries-like lesions were artificially developed. Cariogenic challenge (pH-cycling) was performed for seven days. The pastes were applied before each immersion in demineralization solution, and the varnish was applied only once. KHN values were obtained at baseline, after incipient enamel lesion, and after challenge. The percentage of surface hardness recovery (%SMHR) was performed, and the surface morphology was evaluated by atomic force microscopy (AFM). ANOVA, Tukey's, and student paired t tests were applied at P<.05.
  
  
  RESULTS
  After the cariogenic challenge, the nano-HAP group showed significantly higher KHN and %SMHR values than varnish. The CPP-ACP group showed no increase in KHN. The nano-HAP group showed, via AFM, a protective layer formation with globular deposits on the surface.
  
  
  CONCLUSIONS
  SMHR and AFM morphology revealed that nano-hydroxyapatite paste showed a protective effect against in vitro enamel caries development.
authors: Department of Clinical and Social Dentistry, at Federal University of Paraíba, João Pessoa, Paraíba, Brazil.
authors: Fabíola Galbiatti
authors: FG
authors: de Carvalho
authors: Department of Dentistry, Federal University of Campina Grande, Campina Grande, Paraíba, Brazil.
authors: Basílio Rodrigues
authors: BR
authors: Vieira
authors: Department of Dentistry, Federal University of Campina Grande, Campina Grande, Paraíba, Brazil.
authors: Rogério Lacerda Dos
authors: RL
authors: Santos
authors: Department of Operative Dentistry, at Federal University of Paraíba, João Pessoa, Paraíba, Brazil. fabigalbi@yahoo.com.br.
authors: Hugo Lemes
authors: HL
authors: Carlo
authors: Department of Pharmaceutical Sciences, at Federal University of Paraíba, João Pessoa, Paraíba, Brazil.
authors: Pablo Queiroz
authors: PQ
authors: Lopes
authors: Department of Materials Engineering, at Federal University of Paraíba, João Pessoa, Paraíba, Brazil.
authors: Bruno Alessandro Silva Guedes
authors: BA
authors: de Lima
mesh_terms: D002327:Cariostatic Agents / Q000737:chemistry / Q000627:therapeutic use*; D002364:Caseins / Q000627:therapeutic use; D003731:Dental Caries / Q000517:prevention & control; D003743:Dental Enamel / Q000187:drug effects* / Q000648:ultrastructure; D017886:Durapatite / Q000737:chemistry / Q000627:therapeutic use*; D005460:Fluorides, Topical / Q000627:therapeutic use; D006244:Hardness; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D049329:Nanostructures / Q000737:chemistry / Q000627:therapeutic use*; D009824:Ointments; D020011:Protective Agents / Q000627:therapeutic use; D012969:Sodium Fluoride / Q000627:therapeutic use; D013997:Time Factors; D017001:Tooth Demineralization / Q000517:prevention & control*; D014089:Tooth Remineralization / Q000379:methods
chemical_list: D002327:Cariostatic Agents; D002364:Caseins; D005460:Fluorides, Topical; D009824:Ointments; D020011:Protective Agents; C447032:casein phosphopeptide-amorphous calcium phosphate nanocomplex; C023807:sodium fluoride topical preparation; D012969:Sodium Fluoride; D017886:Durapatite