title: Dehydration and the dynamic dimensional changes within dentin and enamel.
abstract: OBJECTIVE
  The objectives of this study were to quantify the dimensional changes in dentin and enamel during dehydration, and to determine if there are differences between the responses of these tissues from young and old patients.
  
  
  METHODS
  Microscopic digital image correlation (DIC) was used to evaluate deformation of dentin and enamel as a function of water loss resulting from free convection in air. Dimensional changes within both tissues were quantified for two patient age groups (i.e. young 18< or =age< or =30 and old 50< or =age) and in two orthogonal directions (i.e. parallel and perpendicular to the prevailing structural feature (dentin tubules or enamel prisms)). The deformation histories were used to estimate effective dehydration coefficients that can be used in quantifying the strains induced by dehydration.
  
  
  RESULTS
  Both dentin and enamel underwent contraction with water loss, regardless of the patient age. There was no significant difference between responses of the two age groups or the two orthogonal directions. Over 1h of free convection, the average water loss in dentin was 6% and resulted in approximately 0.5% shrinkage. In the same time period the average water loss in the enamel was approximately 1% and resulted in 0.03% shrinkage. The estimated effective dehydration coefficients were -810microm/m/(% weight loss) and -50microm/m/(% weight loss) for dentin and enamel, respectively.
  
  
  CONCLUSIONS
  The degree of deformation shrinkage resulting from dehydration is over a factor of magnitude larger in dentin than enamel.
authors.affiliation: Department of Mechanics, Shanghai University, Shanghai 200444, PR China.
authors.forename: D
authors.initials: D
authors.lastname: Zhang
authors.forename: S
authors.initials: S
authors.lastname: Mao
authors.forename: C
authors.initials: C
authors.lastname: Lu
authors.forename: E
authors.initials: E
authors.lastname: Romberg
authors.forename: D
authors.initials: D
authors.lastname: Arola
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D001834:Body Water / Q000737:chemistry; D003743:Dental Enamel / Q000473:pathology* / Q000648:ultrastructure; D003804:Dentin / Q000473:pathology* / Q000648:ultrastructure; D003890:Desiccation; D006801:Humans; D008838:Microcomputers; D008853:Microscopy; D008875:Middle Aged; D013314:Stress, Mechanical; D013997:Time Factors; D055815:Young Adult