title: Effect of replacement of mandibular defects with a modular endoprosthesis on bone mineral density in a monkey model.
abstract: The effect of mandibular modular endoprostheses on bone mineral density (BMD) in the stem regions was studied. Modular endoprostheses were inserted into standardized mandibular condyle or body defects in 16 Macaca fascicularis. Each group of eight monkeys was divided into two groups, one killed at 3 months, the other at 6 months post-surgery. The mandibles were harvested, sectioned and scanned with a micro-computed tomography scanner. The reconstructed slices, made at a right angles to the long axis of the prosthesis, were analysed using software to calculate BMD in regions of interest buccal, lingual and inferior to the stems of the endoprosthesis. Measurements of the contralateral sides of three monkeys that underwent a similar procedure were used as control/baseline BMD. BMD for the condyle replacement group did not differ significantly from the control group. At 6 months, BMD decreased slightly; significant only at the inferior region. BMD for the body replacement group was significantly lower in all regions compared with control and condyle replacement groups probably because of connection screw loosening and infection. Loss of BMD in the peri-implant region of a modular endoprosthesis for mandibular replacement is minimal up to 6 months postoperatively, provided the device remains stable and well-fixed.
authors.affiliation: Department of Oral and Maxillofacial Surgery, National Dental Centre, Singapore. raginwcw@yahoo.com
authors.forename: R C W
authors.initials: RC
authors.lastname: Wong
authors.forename: S
authors.initials: S
authors.lastname: Lee
authors.forename: H
authors.initials: H
authors.lastname: Tideman
authors.forename: M A W
authors.initials: MA
authors.lastname: Merkx
authors.forename: J
authors.initials: J
authors.lastname: Jansen
authors.forename: K
authors.initials: K
authors.lastname: Liao
mesh_terms: D000818:Animals; D019643:Arthroplasty, Replacement; D001696:Biomechanical Phenomena; D001843:Bone Cements / Q000627:therapeutic use; D015519:Bone Density / Q000502:physiology*; D001863:Bone Screws; D004195:Disease Models, Animal; D007091:Image Processing, Computer-Assisted / Q000379:methods; D021621:Imaging, Three-Dimensional / Q000379:methods; D007595:Joint Prosthesis; D008252:Macaca fascicularis; D008297:Male; D008334:Mandible / Q000503:physiopathology / Q000601:surgery; D008335:Mandibular Condyle / Q000503:physiopathology / Q000601:surgery; D008336:Mandibular Diseases / Q000601:surgery*; D008341:Mandibular Prosthesis; D010012:Osteogenesis / Q000502:physiology; D019904:Polymethyl Methacrylate; D011474:Prosthesis Design; D011475:Prosthesis Failure; D016059:Range of Motion, Articular / Q000502:physiology; D013997:Time Factors; D055114:X-Ray Microtomography / Q000295:instrumentation / Q000379:methods
chemical_list: D001843:Bone Cements; D019904:Polymethyl Methacrylate