[Preclinical study of the effects of fluorinated porcine hydroxyapatite in repairing peri-implant bone defects in canine mandible].

Objective: To evaluate the effects of fluorinated porcine hydroxyapatite (FPHA) on guided bone regeneration of peri-implant buccal bone defects in canine mandible. Methods: Six male beagle dogs were randomly divided into two groups with different time points (4 weeks and 12 weeks after implants placement), with 3 dogs in each group. Bilateral mandibular second premolars, first molars, and second molars in each dog were extracted. The wounds were allowed to heal for 12 weeks. For each dog, four implant beds were prepared in each side and standardized peri-implant buccal bone defect was created at each implant site. After implants placement, the defect sites were randomly allocated in a split-mouth design to blank control group, deproteinized bovine bone mineral (DBBM), the porcine hydroxyapatite (PHA), FPHA and covered with collagen membranes. The animals were sacrificed 4 or 12 weeks after the surgery. Biopsies of the implant sites were obtained for micro-CT evaluation [bone volume fraction (BV/TV) and bone trabecular separation degree (Tb.Sp)] and histological analysis. Results: Micro-CT results showed that 4 weeks after implants placement, PHA, FPHA and DBBM successfully maintained the contour of alveolar ridge at the buccal aspect of the implants, while the contour of alveolar ridge collapsed in the blank control group. BV/TV in the FPHA group [(24.77±2.20) %] was significantly higher than that in the PHA group [(16.89±1.70)%] and DBBM group [(15.68±3.15)%] (P<0.05). Tb.Sp in the FPHA group (0.70±0.07) was significantly lower than that in the DBBM group (1.03±0.19) (P<0.05). Twelve weeks after implants placement, the alveolar ridge contour of the grafted sites in PHA, FPHA and DBBM group remained stable. The alveolar ridge of the blank control group was still collapsed. There was no significant difference in BV/TV and Tb.Sp between PHA group, FPHA group and DBBM group. The histomorphological analysis showed that 4 weeks after implants placement, in the central area of the defect, the amount and maturity of new bone (NB) around the material particles in FPHA group was higher than that in PHA group and DBBM group. Osseointegration could be observed between the NB and implant surface in all the four groups. Twelve weeks after implants placement, the material particles were surrounded by a large number of mature NB in PHA, FPHA and DBBM group. Conclusions: The incorporation of fluoride ion into PHA could effectively promote the repair of peri-implant bone defects in the early stage of guided bone regeneration.