No abstract

Injuries to the extremities often require resection of necrotic hard tissue. For large-bone defects, autogenous bone grafting is ideal but, similar to all grafting procedures, is subject to limitations. Synthetic biomaterial-driven engineered healing offers an alternative approach. This work focuses on three-dimensional (3D) printing technology of solid-free form fabrication, more specifically robocasting/direct write. The research hypothesizes that a bioactive calcium-phosphate scaffold may successfully regenerate extensive bony defects in vivo and that newly regenerated bone will demonstrate mechanical properties similar to native bone as healing time elapses. Robocasting technology was used in designing and printing customizable scaffolds, composed of 100% beta tri-calcium phosphate (β-TCP), which were used to repair critical sized long-bone defects. Following full thickness segmental defects (~11 mm × full thickness) in the radial diaphysis in New Zealand white rabbits, a custom 3D-printed, 100% β-TCP, scaffold was implanted or left empty (negative control) and allowed to heal over 8, 12, and 24 weeks. Scaffolds and bone, en bloc, were subjected to micro-CT and histological analysis for quantification of bone, scaffold and soft tissue expressed as a function of volume percentage. Additionally, biomechanical testing at two different regions, (a) bone in the scaffold and (b) in native radial bone (control), was conducted to assess the newly regenerated bone for reduced elastic modulus (E ) and hardness (H) using nanoindentation. Histological analysis showed no signs of any adverse immune response while revealing progressive remodelling of bone within the scaffold along with gradual decrease in 3D-scaffold volume over time. Micro-CT images indicated directional bone ingrowth, with an increase in bone formation over time. Reduced elastic modulus (E ) data for the newly regenerated bone presented statistically homogenous values analogous to native bone at the three time points, whereas hardness (H) values were equivalent to the native radial bone only at 24 weeks. The negative control samples showed limited healing at 8 weeks. Custom engineered β-TCP scaffolds are biocompatible, resorbable, and can directionally regenerate and remodel bone in a segmental long-bone defect in a rabbit model. Custom designs and fabrication of β-TCP scaffolds for use in other bone defect models warrant further investigation.

This study investigated the effects of osseodensification drilling on the stability and osseointegration of machine‐cut and acid‐etched endosteal implants in low‐density bone. Twelve sheep received six implants inserted into the ilium, bilaterally (n = 36 acid‐etched, and n = 36 as‐machined). Individual animals received three implants of each surface, placed via different surgical techniques: (1) subtractive regular‐drilling (R): 2.0 mm pilot, 3.2 and 3.8 mm twist drills); (2) osseodensification clockwise‐drilling (CW): Densah Bur (Versah, Jackson, MI) 2.0 mm pilot, 2.8, and 3.8 mm multifluted tapered burs; and (3) osseodensification counterclockwise‐drilling (CCW) Densah Bur 2.0 mm pilot, 2.8 mm, and 3.8 mm multifluted tapered burs. Insertion torque was higher in the CCW and CW‐drilling compared to the R‐drilling (p < 0.001). Bone‐to‐implant contact (BIC) was significantly higher for CW (p = 0.024) and CCW‐drilling (p = 0.006) compared to the R‐drilling technique. For CCW‐osseodensification‐drilling, no statistical difference between the acid‐etched and machine‐cut implants at both time points was observed for BIC and BAFO (bone‐area‐fraction‐occupancy). Resorbed bone and bone forming precursors, preosteoblasts, were observed at 3‐weeks. At 12‐weeks, new bone formation was observed in all groups extending to the trabecular region. In low‐density bone, endosteal implants inserted via osseodensification‐drilling presented higher stability and no osseointegration impairments compared to subtractive regular‐drilling technique, regardless of evaluation time or implant surface. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 615–623, 2019.

The present study hypothesized that different bone healing patterns through initial stages of osseointegration would be observed when three distinct commercially available implant systems (Nobel Groovy, Implacil, and Zimmer TSV) were used, leading to significant variations in histometric levels of total bone and new bone formation during the osseointegration process. Materials and Methods: A total of 48 implants were placed bilaterally on the tibias of eight beagle dogs and allowed to heal for 2 and 6 weeks. Following euthanasia, nondecalcified specimens were processed for morphologic and histometric evaluation. Bone-to-implant contact (BIC) and new bone area fraction occupancy (BAFO) analyses for native and new bone were performed along the whole perimeter of each implant and separately for the cortical and trabecular bone regions. Results: Morphologic evaluation of cortical bone presented different healing patterns and osseointegration levels for different implant systems as time elapsed in vivo. Interfacial remodeling was the chief healing pattern in Zimmer implants, while a combination of interfacial remodeling and healing chambers was observed in Nobel and Implacil implants. When trabecular bone was evaluated, similar bone healing patterns were observed between systems despite different levels of osseointegration observed as a function of implantation time, implant system, and native and/or new bone BIC and BAFO. Conclusion: Different implant systems led to different healing patterns during early stages of osseointegration. Such variation in pattern was more noticeable in the cortical regions compared to the trabecular regions. The variation in bone healing pattern did significantly influence overall indicators of native and new BIC and BAFO during the osseointegration process. The postulated hypothesis was accepted.

BackgroundThis study aimed to compare the histomorphometric and histological bone response to laser-sintered implants followed by resorbable-blasting media (RBM) process relative to standard machined/RBM surface treated implants.Material and MethodsSix male sheep (n=6) received 2 Ti-6Al-4V implants (1 per surface) in each side of the mandible for 6 weeks in vivo. The histomorphometric parameters bone-implant contact (BIC) and bone area fraction occupancy (BAFO) were evaluated.ResultsOptical interferometry revealed higher Sa and Sq values for the laser-sintered/RBM surface in relation to standard/RBM implants. No significant differences in BIC were observed between the two groups (p>0.2), but significantly higher BAFO was observed for standard/RBM implants (p<0.01).ConclusionsThe present study demonstrated that both surfaces were biocompatible and osseoconductive, and the combination of laser sintering and RBM has no advantage over the standard machined implants with subsequent RBM. Key words:Dental implants, osseointegration, resorbable- blasting media, sheep, in vivo.