title: The use of light/chemically hardened polymethylmethacrylate, polyhydroxyethylmethacrylate, and calcium hydroxide graft material in combination with polyanhydride around implants in minipigs: part I: immediate stability and function.
abstract: BACKGROUND
  The present study is designed as a proof-of-concept study to evaluate light/chemical hardening technology and a newly formulated polymethylmethacrylate, polyhydroxyethylmethacrylate, and calcium hydroxide (PPCH) plus polyanhydride (PA) (PPCH-PA) composite graft material as a bone substitute compared to positive and negative controls in a minipig model.
  
  
  METHODS
  PPCH-PA (composite graft); PPCH alone (positive control), PA alone (positive control), and no graft (negative control) were compared. Four mandibular premolar teeth per quadrant were extracted; a total of 48 implants were placed into sockets in three minipigs. Abutments were placed protruding into the oral cavity 4 mm in height for immediate loading. Crestal areas and intrabony spaces were filled with PPCH-PA, PPCH, or PA using a three-phase delivery system in which all graft materials were hardened by a light cure. In the negative control group, implant sites were left untreated. At 12 weeks, block sections containing implants were obtained. Evaluations included periodontal probing, pullout-force load, and stability measurements to determine implant stability, radiographs to examine bone levels, and scanning electron microscopy (SEM)-energy-dispersed spectroscopy to determine bone-to-implant contact.
  
  
  RESULTS
  Probing measurements did not reveal any pathologic pocket formation or bone loss. Radiographs revealed that immediate implant placement and loading resulted in bone at or slightly apical to the first thread of the implant in all groups at 12 weeks. Stability test values showed a relative clinical stability for all implants (range: -7 to +1); however, implants augmented with PPCH-PA exhibited a statistically significantly greater stability compared to all other groups (P <0.05). The newly formed bone in PPCH-PA-treated sites was well organized with less marrow spaces and well-distributed osteocytes. SEM revealed a tighter implant-socket interface in the PPCH-PA group compared to other groups with reduced microfissures and implant-bone interface fractures during pullout testing, whereas implants treated with PA or no graft showed ≈ 10-μm microfissures between the implant and bone with fractures of the intrathread bone.
  
  
  CONCLUSIONS
  The newly formulated chemically hardened graft material PPCH-PA was useful in immediate implant placement after tooth extraction and resulted in greater stability and a well-organized implant-bone interface with immediate loading, especially in those areas where cancellous bone was present. The results of this proof-of-concept study warranted further research investigating different healing times and longer durations.
authors.affiliation: Department of Periodontology, The Forsyth Institute, Cambridge, MA 02142, USA.
authors.forename: Hatice
authors.initials: H
authors.lastname: Hasturk
authors.forename: Alpdogan
authors.initials: A
authors.lastname: Kantarci
authors.forename: Mazen
authors.initials: M
authors.lastname: Ghattas
authors.forename: Marcella
authors.initials: M
authors.lastname: Schmidt
authors.forename: Russell A
authors.initials: RA
authors.lastname: Giordano
authors.forename: Arthur
authors.initials: A
authors.lastname: Ashman
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Diekwisch
authors.forename: Thomas
authors.initials: T
authors.lastname: Van Dyke
mesh_terms: D000539:Alveolar Process / Q000000981:diagnostic imaging; D000540:Alveolar Ridge Augmentation / Q000379:methods; D000818:Animals; D018786:Bone Substitutes / Q000528:radiation effects / Q000627:therapeutic use*; D002126:Calcium Hydroxide / Q000737:chemistry* / Q000528:radiation effects; D015921:Dental Implants; D017268:Dental Prosthesis Retention; D057893:Immediate Dental Implant Loading; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging / Q000601:surgery; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D023421:Models, Animal; D016348:Osseointegration / Q000502:physiology; D010012:Osteogenesis / Q000502:physiology; D010514:Periodontal Pocket / Q000145:classification; D049388:Polyanhydrides / Q000737:chemistry* / Q000528:radiation effects; D011102:Polyhydroxyethyl Methacrylate / Q000737:chemistry / Q000528:radiation effects; D011108:Polymers / Q000737:chemistry / Q000528:radiation effects; D019904:Polymethyl Methacrylate / Q000737:chemistry* / Q000528:radiation effects; D011897:Random Allocation; D013052:Spectrometry, X-Ray Emission; D013314:Stress, Mechanical; D013552:Swine; D013556:Swine, Miniature; D013997:Time Factors; D020390:Tooth Socket / Q000601:surgery; D055114:X-Ray Microtomography
chemical_list: D018786:Bone Substitutes; D015921:Dental Implants; C407025:HTR bioplant; D049388:Polyanhydrides; D011108:Polymers; D011102:Polyhydroxyethyl Methacrylate; D019904:Polymethyl Methacrylate; D002126:Calcium Hydroxide