Histometric evaluation of bone regeneration around immediate implants partially in contact with bone: a pilot study in dogs

Bone regeneration was evaluated around immediate implants partially in contact with bone, with or without the concurrent application of a combination of platelet-derived growth factor (PDGF) and insulin-like growth factor (IGF-1). Mandibular premolars were removed, and the implant osteotomies were prepared; a uniform circumferential gap was prepared 1.25 mm beyond the width of the implant bed in the coronal half. Twelve implants (8.5 x 3.75 mm) were inserted in six dogs. Before insertion, an implant received a single application of 5 micrograms/mL of PDGF and IGF-1 delivered in 0.10 mL of 4% methylcellulose gel or 0.10 mL of 4% methylcellulose gel only as a control. To label regenerated bone, a 2% calcein green solution was administered by intramuscular injection at 0, 7, 15, 30, and 45 days after implant insertion Three and 8 weeks after implant insertion undecalcified sections were obtained, and the degree of bone to implant contact, the bone area, and the intensity of bone labeling were measured into the limits of the eight most coronal threads of the implant (four threads on each side of each implant). The results showed a greater extension of bone-to-implant contact, a larger percentage of bone area, and greater intensity of bone labeling for test versus control implants (P < .01). Within the limits of the present study, it was concluded that the combination of PDGF/IGF-1 might be an alternative for enhancing bone healing around implants partially in contact with bone.