title: Biocompatibility and bone formation with porous modified PMMA in normal and irradiated mandibular tissue.
abstract: A cemented mandibular endoprosthesis is a potentially viable option for mandibular reconstruction after ablative surgery. The commonly used PMMA cement has the inherent weakness of a lack of bioactivity. Improvement by the addition of porosities and bioactive compounds like calcium phosphates may resolve this issue.
  
  
  OBJECTIVE
  The objective of this study was to assess the bone and tissue response to two modified PMMA cements with post-operative radiation as an additional influencing factor.
  
  
  METHODS
  An in vivo animal study was performed using a mandibular rabbit model. A porous PMMA cement (A) and a porous cement incorporated with Beta-tricalcium phosphate particles (b-TCP) (B) were placed in bilateral mandibular defects with exposed roots and mandibular nerve of 20 animals. Half of the animals underwent additional post-operative radiation.
  
  
  RESULTS
  The animals were healthy with only a minor complication in one rabbit. Temperature analysis showed no significant risk of thermal necrosis with the maximal in vivo cement temperature at 37.8°C. Histology demonstrated: (1) good bone ingrowth around the defect as well as within the pores of the cement and defect bridging was achieved in 70% of the specimens after 12-15 weeks of implantation, (2) no pulpal injury with minor secondary cementum response, (3) an intact mandibular nerve with no inflammation, (4) extensive degradation and resorption of the b-TCP particles by 12-15 weeks, and (5) presence of an intervening thin fibrous tissue at the bone-to-cement interface. Histomorphometrical analysis revealed that there was no difference between the different cements and the presence or absence of post-operative radiation. The 12-15 weeks specimens showed significantly more bone ingrowth and bone maturity than the 4-7 weeks specimens.
  
  
  CONCLUSIONS
  Both modified PMMA cements have good biocompatibility, bioactivity and support bone ingrowth and additional post-operative radiation did not show any negative effects.
authors.affiliation: Department of Oral & Maxillofacial Surgery, National Dental Centre of Singapore, Singapore. kokwenglye@yahoo.com
authors.forename: Kok Weng
authors.initials: KW
authors.lastname: Lye
authors.forename: Henk
authors.initials: H
authors.lastname: Tideman
authors.forename: Joop C G
authors.initials: JC
authors.lastname: Wolke
authors.forename: Matthias A W
authors.initials: MA
authors.lastname: Merkx
authors.forename: Francis K C
authors.initials: FK
authors.lastname: Chin
authors.forename: John A
authors.initials: JA
authors.lastname: Jansen
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000494:pharmacology*; D001843:Bone Cements / Q000494:pharmacology*; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging / Q000187:drug effects* / Q000528:radiation effects* / Q000601:surgery*; D008422:Materials Testing; D010012:Osteogenesis / Q000187:drug effects* / Q000528:radiation effects*; D019904:Polymethyl Methacrylate / Q000494:pharmacology*; D016062:Porosity; D011817:Rabbits; D055114:X-Ray Microtomography
chemical_list: D001672:Biocompatible Materials; D001843:Bone Cements; D019904:Polymethyl Methacrylate