title: Effects of calcium silicate-based materials on the flexural properties of dentin.
abstract: BACKGROUND
  Prolonged exposure of root dentin to calcium hydroxide alters the fracture resistance of dentin. Calcium silicate-based materials (CSMs) used in endodontics release calcium hydroxide on setting. This study examined whether prolonged contact of dentin with CSMs adversely affects its mechanical properties.
  
  
  METHODS
  Dentin beams prepared from extracted human molars (7 × 3 × 0.3 mm) were divided into 3 groups on the basis of the material to which dentin was exposed (Biodentine, MTA Plus, and untreated control beams). Three-point flexure to failure was performed for each beam at designated exposure times (24 hours, 1, 2, and 3 months; n = 10). Data were analyzed with 2-factor repeated-measures analyses of variance to determine the effects of material and aging time on flexural modulus, flexural strength, and modulus of toughness (α = 0.05).
  
  
  RESULTS
  For flexural modulus, there was no significant difference for material (P = .947) or aging time (P = .064) when compared with baseline control. For flexural strength, significant differences were associated with aging time (P < .001) but not with material (P = .349). Flexural strength of dentin exposed to Biodentine decreased significantly after 2 and 3 months, whereas that exposed to MTA Plus decreased significantly after 3 months of aging (P < .05). For modulus of toughness, significant declines were observed for both material (P < .004) and aging time (P < .001).
  
  
  CONCLUSIONS
  Both CSMs alter material toughness more than the strength and stiffness of dentin after aging in 100% relative humidity. Because dentin toughness is attributed to its collagen matrix, the amount of collagen extracted from mineralized dentin and changes in collagen ultrastructure should be further examined after exposure of dentin to CSMs.
authors.affiliation: Department of Endodontics, Georgia Health Sciences University, Augusta, Georgia 30912-1129, USA.
authors.forename: Allen N
authors.initials: AN
authors.lastname: Sawyer
authors.forename: Sergey Y
authors.initials: SY
authors.lastname: Nikonov
authors.forename: Alaina K
authors.initials: AK
authors.lastname: Pancio
authors.forename: Li-na
authors.initials: LN
authors.lastname: Niu
authors.forename: Kelli A
authors.initials: KA
authors.lastname: Agee
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Loushine
authors.forename: Roger N
authors.initials: RN
authors.lastname: Weller
authors.forename: David H
authors.initials: DH
authors.lastname: Pashley
authors.forename: Franklin R
authors.initials: FR
authors.lastname: Tay
mesh_terms: D000293:Adolescent; D000328:Adult; D017607:Aluminum Compounds / Q000494:pharmacology; D001696:Biomechanical Phenomena; D017610:Calcium Compounds / Q000494:pharmacology*; D002126:Calcium Hydroxide / Q000494:pharmacology; D003799:Dental Stress Analysis / Q000295:instrumentation; D003804:Dentin / Q000187:drug effects*; D004338:Drug Combinations; D055119:Elastic Modulus; D006801:Humans; D006813:Humidity; D008422:Materials Testing; D010087:Oxides / Q000494:pharmacology; D018583:Pliability; D012387:Root Canal Filling Materials / Q000494:pharmacology*; D017640:Silicates / Q000494:pharmacology*; D013314:Stress, Mechanical; D013997:Time Factors; D055815:Young Adult
chemical_list: D017607:Aluminum Compounds; D017610:Calcium Compounds; D004338:Drug Combinations; D010087:Oxides; D012387:Root Canal Filling Materials; D017640:Silicates; C086631:mineral trioxide aggregate; D002126:Calcium Hydroxide; C031293:calcium silicate