implant

Preliminary evaluation of local drug delivery of amphotericin B and in vivo degradation of chitosan and polyethylene glycol blended sponges

Authors

Ashley Cox Parker, Cheyenne Rhodes, Jessica Amber Jennings, Lauren Hittle, Mark Shirtliff, Joel D. Bumgardner and Warren O. Haggard

Abstract

This research investigated the combination of polyethylene glycol with chitosan in point-of-care loaded sponges made by one or two lyophilizations for adjunctive local antifungal delivery in musculoskeletal wounds. Blended and control chitosan sponges were evaluated in vitro for antifungal release and activity, degradation, cytocompatibility, and characterized for spectroscopic, crystallinity, thermal, and morphologic material properties. In vivo biocompatibility and degradation of sponges were also evaluated in a rat intramuscular pouch model 4 and 10 days after implantation. Blended sponges released amphotericin B active against Candida albicans (>0.25 µg/mL) over 72 h and did not elicit cytotoxicity response of fibroblasts. Blended sponges exhibited decreases in surface roughness, decreased thermal decomposition temperatures, as well as small Fourier transform infrared spectroscopy and crystallinity differences, compared with chitosan-only sponges. Three of the four blended sponge formulations exhibited 31%–94% increases in in vitro degradation from the chitosan sponges after 10 days, but did not demonstrate the same increase in in vivo degradation. Low inflammatory in vivo tissue response to blended and chitosan-only sponges was similar over 10 days. These results demonstrated that adding polyethylene glycol to chitosan sponges does improve local antifungal release, cytocompatibility, and in vitro degradation, but does not increase in vivo degradation.

Link To Article

http://dx.doi.org/10.1002/jbm.b.33356

Sensitivity and Specificity of Radiographic Methods for Predicting Insertion Torque of Dental Implants

Authors

Arthur Rodriguez Gonzalez Cortes, DDS, PhD, Hazem Eimar, DDS, MS, Jorge de Sá Barbosa, DDS, MS, Claudio Costa, DDS, PhD, Emiko Saito Arita, DDS, PhD, Faleh Tamimi, DDS, PhD

Abstract

Background: Subjective radiographic classifications of alveolar bone have been proposed and correlated with implant insertion torque (IT). The present diagnostic study aimed to identify quantitative bone features influencing IT, and to use these findings to develop an objective radiographic classification for predicting IT.

Methods: Demographics, panoramic radiographs (taken at the beginning of dental treatment) and cone beam computed tomographic scans (taken for implant surgical planning) of a total of 25 patients receiving 31 implants were analyzed. Bone samples retrieved from implant sites were assessed with dual x-ray absorptiometry, micro-computed tomography and histology. Odds ratio, sensitivity and specificity of all variables to predict high peak IT were assessed.

Results: A ridge cortical thickness greater than .75mm and a normal appearance of the inferior mandibular cortex were the most sensitive variables for predicting high peak IT (87.5% and 75%, respectively). A classification based on the combination of both variables presented high sensitivity (90.9%) and specificity (100%) for predicting IT.

Conclusion: Within the limitations of this study, the present results suggest that it is possible to predict IT accurately, based on radiographic findings of the patient. This could be useful in the treatment plan of immediate loading cases.

Link To Article

http://dx.doi.org/10.1902/jop.2015.140584

A BIODEGRADABLE GENTAMICIN-HYDROXYAPATITE-COATING FOR INFECTION PROPHYLAXIS IN CEMENTLESS HIP PROSTHESES

Authors

D. Neut, R.J.B. Dijkstra, J.I. Thompson, C. Kavanagh, H.C. van der Mei and H.J. Busscher

Abstract

A degradable, poly (lactic-co-glycolic acid) (PLGA), gentamicin-loaded prophylactic coating for hydroxyapatite (HA)-coated cementless hip prostheses is developed with similar antibacterial efficacy as offered by gentamicinloaded cements for fixing traditional, cemented prostheses in bone. We describe the development pathway, from in vitro investigation of antibiotic release and antibacterial properties of this PLGA-gentamicin-HA-coating in different in vitro models to an evaluation of its efficacy in preventing implant-related infection in rabbits. Bone in-growth in the absence and presence of the coating was investigated in a canine model. The PLGAgentamicin-HA-coating showed high-burst release, with antibacterial efficacy in agar-assays completely disappearing after 4 days, minimising risk of inducing antibiotic resistance. Gentamicin-sensitive and gentamicinresistant staphylococci were killed by the antibiotic-loaded

coating, in a simulated prosthesis-related interfacial gap. PLGA-gentamicin-HA-coatings prevented growth of bioluminescent staphylococci around a miniature-stem mounted in bacterially contaminated agar, as observed using bio-optical imaging. PLGA-gentamicin-HA-coated pins inserted in bacterially contaminated medullary canals in rabbits caused a statistically significant reduction in infection rates compared to HA-coated pins without gentamicin. Bone ingrowth to PLGA-gentamicin-HA coated pins, in condylar defects of Beagle dogs was not

impaired by the presence of the degradable, gentamicin loaded coating. In conclusion, the PLGA-gentamicin HA-coating constitutes an effective strategy for infection prophylaxis in cementless prostheses.

Link to Article

http://www.ecmjournal.org/journal/papers/vol029/pdf/v029a04.pdf

Microdamage generation by tapered and cylindrical mini-screw implants after pilot drilling

Authors

Emily Taing-Watson, Thomas R. Katona, Kelton T. Stewart, Ahmed Ghoneima, Gabriel T. M. Chu, Hee-Moon Kyung, and Sean S. Liu

Abstract

Objective: To investigate the relationship between mini-screw implant (MSI) diameter (1.6 vs 2.0 mm) and shape (tapered vs cylindrical) and the amount of microdamage generated during insertion.

Materials and Methods: Thirty-six cylindrical and 36 tapered MSIs, 6 mm long, were used in this study. Half of each shape was 1.6 mm in diameter, while the other half was 2.0 mm. After pilot drilling, four and five MSIs were inserted, respectively, into fresh cadaveric maxillae and mandibles of dogs. Bone blocks containing the MSIs were sectioned and ground parallel to the MSI axis. Epifluorescent microscopy was used to measure overall cortical thickness, crack length, and crack number adjacent to the MSI. Crack density and total microdamage burden per surface length were calculated. Three-way analysis of variance (ANOVA) was used to test the effects of jaw, and MSI shape and diameter. Pairwise comparisons were made to control the overall significance level at 5%.

Results: The larger (2.0 vs 1.6 mm) cylindrical MSIs increased the numbers, lengths, and densities of microcracks, and the total microdamage burden. The same diameter cylindrical and tapered MSIs generated a similar number of cracks and crack lengths. More total microdamage burden was created by the 2.0-mm cylindrical than the 2.0-mm tapered MSIs. Although higher crack densities were produced by the insertion of 1.6-mm tapered MSIs, there was no difference in total microdamage burden induced by 1.6-mm tapered and 1.6-mm cylindrical MSIs.

Conclusions: Pilot drilling is effective in reducing microdamage during insertion of tapered MSIs. To prevent excessive microdamage, large diameter and cylindrical MSIs should be avoided.

Link To Article

http://dx.doi.org/10.2319/062314-452.1

Intermittent PTH administration and mechanical loading are anabolic for periprosthetic cancellous bone

Authors

Matthew J. Grosso, Hayden-William Courtland, Xu Yang, James P. Sutherland, Kirsten Stoner, Joseph Nguyen, Anna Fahlgren, F. Patrick Ross, Marjolein C. H. van der Meulen, and Mathias P. Bostrom

Abstract

The purpose of this study was to determine the individual and combined effects on periprosthetic cancellous bone of intermittent parathyroid hormone administration (iPTH) and mechanical loading at the cellular, molecular, and tissue levels. Porous titanium implants were inserted bilaterally on the cancellous bone of adult rabbits beneath a loading device attached to the distal lateral femur. The left femur received a sham loading device. The right femur was loaded daily, and half of the rabbits received daily PTH. Periprosthetic bone was evaluated up to 28 days for gene expression, histology, and µCT analysis. Loading and iPTH increased bone mass by a combination of two mechanisms: (1) Altering cell populations in a pro-osteoblastic/anti-adipocytic direction, and (2) controlling bone turnover by modulating the RANKL-OPG ratio. At the tissue level, BV/TV increased with both loading (+53%, p < 0.05) and iPTH (+54%, p < 0.05). Combined treatment showed only small additional effects at the cellular and molecular levels that corresponded to a small additive effect on bone volume (+13% compared to iPTH alone, p > 0.05). This study suggests that iPTH and loading are potential therapies for enhancing periprosthetic bone formation. The elucidation of the cellular and molecular response may help further enhance the combined therapy and related targeted treatment strategies.

Link To Article

http://dx.doi.org/10.1002/jor.22748

Development of injectable citrate-based bioadhesive bone implants

Authors

Denghui Xie, Jinshan Guo, M. Reza Mehdizadeh, Richard T. Tran, Ruisong Chen, Dawei Sun, Guoying Qian, Dadi Jin, Xiaochun Bai and Jian Yang

Abstract

Injectable bone implants have been widely used in bone tissue repairs, including the treatment of comminuted bone fractures (CBF). However, most injectable bone implants are not suitable for the treatment of CBF because of their weak tissue adhesion strengths and minimal osteoinduction. Citrate has been recently reported to promote bone formation through enhanced bioceramic integration and osteoinductivity. Herein, a novel injectable citrate-based mussel-inspired bioadhesive hydroxyapatite (iCMBA/HA) bone substitute was developed for CBF treatment. Note that iCMBA/HA can be set within 2–4 minutes and the as-prepared (wet) iCMBA/HA possesses low swelling ratios, compressive mechanical strengths of up to 3.2 ± 0.27 MPa, complete degradation in 30 days, suitable biocompatibility, and osteoinductivity. This is also the first time that citrate supplementation in osteogenic medium and citrate released from iCMBA/HA degradation has been demonstrated to promote the mineralization of osteoblastic differentiated human mesenchymal stem cells (hMSCs). In vivo evaluation of iCMBA/HA in a rabbit comminuted radial fracture model showed significantly increased bone formation with markedly enhanced three-point bending strength compared to the negative control. Neovascularization and bone ingrowth, as well as highly organized bone formation, were also observed, showing the potential of iCMBA/HA in treating CBF.

Link To Article

http://dx.doi.org/10.1039/c4tb01498g