title: Development of a nonrigid, durable calcium phosphate cement for use in periodontal bone repair.
abstract: BACKGROUND
  Calcium phosphate cement (CPC) hardens in situ to form hydroxyapatite and has been used in dental and craniofacial restorative applications. However, when CPC was used in periodontal osseous repair, tooth mobility resulted in the fracture and exfoliation of the brittle CPC implant. The objective of the authors' study was to develop a strong and nonrigid CPC to provide compliance for tooth mobility without fracturing the implant.
  
  
  METHODS
  The authors used tetracalcium phosphate, dicalcium phosphate anhydrous and biopolymer chitosan to develop a strong and nonrigid CPC. They used a powder:liquid ratio of 2:1, compared with the 1:1 ratio of a previously developed nonrigid CPC control. Specimens were characterized using a flexural test, scanning electron microscopy and powder X-ray diffraction.
  
  
  RESULTS
  After 28 days of immersion, the new cement had a flexural strength (mean +/- standard deviation; n = 6) of 5.2 +/- 1.0 megapascals, higher than 1.8 +/- 1.5 MPa for the control (P < .05) and overlapping the reported strengths of sintered hydroxyapatite implants and cancellous bone. This cement showed a high ductility with a strain at peak load of 6.5 +/- 1.3 percent, compared with 4.4 +/- 1.9 percent for the control; both were 20-fold higher than the 0.2 percent of the conventional CPC. Nanosized hydroxyapatite crystals, similar to those in teeth and bones, were formed in the cements.
  
  
  CONCLUSIONS
  The new nonrigid cement, containing nanohydroxyapatite crystals, possessed a high ductility and superior fracture resistance. This strong, tough and nonrigid CPC may be useful in periodontal repair to provide compliance for tooth mobility without fracture.
  
  
  CONCLUSIONS
  The results of this study may yield the first self-hardening and nonrigid hydroxyapatite composite with high strength and durability and large deformation capability to be useful in the regeneration of periodontal osseous defects.
authors.affiliation: Paffenbarger Researcher Center, American Dental Association Foundation, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
authors.forename: Hockin H K
authors.initials: HH
authors.lastname: Xu
authors.forename: Shozo
authors.initials: S
authors.lastname: Takagi
authors.forename: Limin
authors.initials: L
authors.lastname: Sun
authors.forename: Latiff
authors.initials: L
authors.lastname: Hussain
authors.forename: Laurence C
authors.initials: LC
authors.lastname: Chow
authors.forename: William F
authors.initials: WF
authors.lastname: Guthrie
authors.forename: James H
authors.initials: JH
authors.lastname: Yen
mesh_terms: D016301:Alveolar Bone Loss / Q000601:surgery; D001672:Biocompatible Materials / Q000737:chemistry; D001843:Bone Cements / Q000138:chemical synthesis* / Q000737:chemistry; D001861:Bone Regeneration; D018786:Bone Substitutes / Q000138:chemical synthesis* / Q000737:chemistry; D002130:Calcium Phosphates / Q000138:chemical synthesis* / Q000737:chemistry; D002626:Chemistry, Pharmaceutical; D048271:Chitosan / Q000737:chemistry; D003461:Crystallography; D017886:Durapatite / Q000737:chemistry; D004548:Elasticity; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D049329:Nanostructures; D018583:Pliability; D011208:Powders; D012996:Solutions; D013314:Stress, Mechanical; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D001843:Bone Cements; D018786:Bone Substitutes; D002130:Calcium Phosphates; D011208:Powders; D012996:Solutions; C485830:tetracalcium phosphate; D048271:Chitosan; D017886:Durapatite; C020243:calcium phosphate; C485829:calcium phosphate, dibasic, anhydrous