Effects of rhBMP-2 on Sandblasted and Acid Etched Titanium Implant Surfaces on Bone Regeneration and Osseointegration: Spilt-Mouth Designed Pilot Study

Abstract

This study was conducted to evaluate effects of rhBMP-2 applied at different concentrations to sandblasted and acid etched (SLA) implants on osseointegration and bone regeneration in a bone defect of beagle dogs as pilot study using split-mouth design. Methods. For experimental groups, SLA implants were coated with different concentrations of rhBMP-2 (0.1, 0.5, and 1 mg/mL). After assessment of surface characteristics and rhBMP-2 releasing profile, the experimental groups and untreated control groups (n = 6 in each group, two animals in each group) were placed in split-mouth designed animal models with buccal open defect. At 8 weeks after implant placement, implant stability quotients (ISQ) values were recorded and vertical bone height (VBH, mm), bone-to-implant contact ratio (BIC, %), and bone volume (BV, %) in the upper 3 mm defect areas were measured. Results. The ISQ values were highest in the 1.0 group. Mean values of VBH (mm), BIC (%), and BV (%) were greater in the 0.5 mg/mL and 1.0 mg/mL groups than those in 0.1 and control groups in buccal defect areas. Conclusion. In the open defect area surrounding the SLA implant, coating with 0.5 and 1.0 mg/mL concentrations of rhBMP-2 was more effective, compared with untreated group, in promoting bone regeneration and osseointegration.

Figure 1

Experimental implant design and schematic diagram of the buccal open defect and mesial, distal, and lingual 1 mm defect models. Twenty-four implants (7.0 mm long and 3.5 mm in diameter; Cowellmedi Co., Busan, Korea) were made of pure titanium and were designed with a straight section on their upper 3 mm and broad threads on their lower 4 mm. A 5.5 mm diameter cover screw mounted on the implant.

Figure 2

Surgical procedures. (a) Alveolar bone was flattened. (b) 5.5 mm width peri-implant defects were created using a trephine bur (Dentech, Tokyo). (c) The implant was placed within its prepared site, and peri-implant defect areas were covered using a 5.5 mm diameter cover screw.

Figure 3

SEM images of each group. (a, e) The control group, (b, f) the 0.1 group, (c, g) the 0.5 group, and (d, h) the 1.0 group. Asterisk: freeze dried rhBMP-2: (a, b, c, d) ×1000, (e, f, g, h) ×5000.

Figure 4

Release kinetics of rhBMP-2 in the three experimental groups. The 1.0 group showed a slower release tendency than the other groups, but all groups showed an initial burst release pattern.

Figure 5

Fluorescent images obtained using a confocal laser microscope. In the 0.5 and 1.0 groups, massive bone remodeling was also observed in the early stage, and this was maintained in the late stage.

Figure 6

Images of histological specimens of each group obtained at 8 weeks: control group (a, b, and c), 0.1 group (d, e, and f), 0.5 group (g, h, and i), and 1.0 group (j, k, and l). Buccal side (a, d, g, and j). Lingual side (c, f, i, and l). F: fibrous tissue; NB: newly formed bone; OB: old bone (central original magnification ×12.5, left and right sides: ×40 original magnification).

Figure 7

Parameters measured in histologic specimens: vertical bone height in the buccal open defect and lingual peri-implant defect areas (VBH, mm), bone-to-implant contact ratio for the upper 3 mm straight implant portions in buccal and lingual defect areas (BIC, red line, %), and bone volume in the buccal and lingual defect area (BV in yellow box, %).