Heat and radiofrequency plasma glow discharge pretreatment of a titanium alloy promote bone formation and osseointegration

Authors

Daniel E. MacDonald, Bruce E. Rapuano, Parth Vyas, Joseph M. Lane, Kathleen Meyers, Timothy Wright

Abstract

Orthopedic and dental implants manifest increased failure rates when inserted into low density bone. We determined whether chemical pretreatments of a titanium alloy implant material stimulated new bone formation to increase osseointegration in vivo in trabecular bone using a rat model. Titanium alloy rods were untreated or pretreated with heat (600 °C) or radiofrequency plasma glow discharge (RFGD). The rods were then coated with the extracellular matrix protein fibronectin (1 nM) or left uncoated and surgically implanted into the rat femoral medullary cavity. Animals were euthanized 3 or 6 weeks later, and femurs were removed for analysis. The number of trabeculae in contact with the implant surface, surface contact between trabeculae and the implant, and the length and area of bone attached to the implant were measured by histomorphometry. Implant shear strength was measured by a pull-out test. Both pretreatments and fibronectin enhanced the number of trabeculae bonding with the implant and trabeculae-to-implant surface contact, with greater effects of fibronectin observed with pretreated compared to untreated implants. RFGD pretreatment modestly increased implant shear strength, which was highly correlated (r2 = 0.87 − 0.99) with measures of trabecular bonding for untreated and RFGD-pretreated implants. In contrast, heat pretreatment increased shear strength 3 to 5-fold for both uncoated and fibronectin-coated implants at 3 and 6 weeks, suggesting a more rapid increase in implant-femur bonding compared to the other groups. In summary, our findings suggest that the heat and RFGD pretreatments can promote the osseointegration of a titanium alloy implant material.

Link to Article

http://dx.doi.org/10.1002/jcb.24585

Immediately Placed Implants in Periodontally Compromised Patients: A Prospective Clinical Study

Authors

Rehab Elsharkawy and Hala El-Menoufy

Abstract

Purpose: This study was done to compare the outcome of implants placed immediately in partially edentulous periodontally compromised to periodontally healthy patients clinically and radiographically. Material and methods: Twenty immediately placed implants were followed up one year after loading clinically and radiographically. Patients were divided into 2 groups: 10 implants in group H (healthy, n=9) and 10 implants in group PD (moderate to severe chronic periodontitis, n=7). Clinical (modified bleeding index mBI, modified plaque index mPI, probing pocket depth PPD and degree of mobility using Periotest device) and radiographic parameters (Bone implant contact ratio BICR and vertical bone resorption) were assessed. Results: There were no significant differences in implant success rate between the 2 groups. Since the time of loading till the end of follow up period all implants were immobile, there was no pain or suppuration around the implants and there were no evidence of peri-implant radiolucency in the x-rays. Through all periods; there was no statistically significant difference between the two groups in the mPI or PPD, at any time point. At loading and 3 months post-loading; PD group showed statistically significantly higher mean mBI than healthy group. PD group showed statistically significantly lower mean PTVs (more stability) at time of loading (-1±2.1) and at 3 months PL (-1 ±1.8) than the H group at loading (0.5±0.7) and 3 ms PL (0.6±2) where P was 0.022 and 0.031for L and 3 ms PL respectively. Regarding the radiographic measures, there were no statistically significant differences between the two groups in the BICR and the VBL at any time point, through all the follow up periods P value ≤ 0.05. Conclusion: Immediate implants may be successful treatment modality in partially edentulous patients suffering from moderate to severe chronic periodontitis, provided that careful debridement of the extraction sockets is done and a good maintenance protocol is followed.

Link to Article

http://www.jofamericanscience.org/journals/am-sci/am0903/067_16822am0903_426_434.pdf

Preclinical Evaluation of a Novel Implant for Treatment of a Full-Thickness Distal Femoral Focal Cartilage Defect

Authors

Erik I. Waldorff, PhD, Blake J. Roessler, MD, Terri A. Zachos, DVM, PhD, Bruce S. Miller, MD, MS, Jonathan McHugh, MD, Steven A. Goldstein, PhD

Abstract

A novel, nonresorbable, monolithic composite structure ceramic, developed using a partially stabilized zirconia ceramic common to implantable devices, was used in a cementless weight-bearing articular implant to test the feasibility of replacing a region of degenerated or damaged articular cartilage in the knee as part of a preclinical study using male mongrel dogs lasting up to 24 weeks. Gross/histological cartilage observations showed no differences among control, 12-week and 24-week groups, while pull-out tests showed an increase in maximum pull-out load over time relative to controls. Hence, the use of a novel ceramic implant as a replacement for a focal cartilage defect leads to effective implant fixation within 12 weeks and does not cause significant degradation in opposing articular cartilage in the time frame evaluated.

Link to Article

http://dx.doi.org/10.1016/j.arth.2012.11.020

Delayed Versus Immediate Reconstruction of Mandibular Segmental Defects Using Recombinant Human Bone Morphogenetic Protein 2/Absorbable Collagen Sponge

Authors

Khaled A. Hussein, Ibrahim E. Zakhary, Dana Hailat, Rami Elrefai, Mohamed Sharawy, Mohammed E. Elsalanty

Abstract

We randomized 11 dogs into 2 groups: immediate reconstruction (group 1, n = 6) and delayed reconstruction (group 2, n = 5). A 35-mm osteoperiosteal segmental defect was created on the left side of the mandible. Reconstruction with rhBMP2/ACS was carried out in the same setting in group 1 or at 4 weeks postoperatively in group 2. The contralateral side acted as an internal control. Animals were monitored both clinically and radiographically throughout the experiment. Twelve weeks after the application of rhBMP2/ACS, the quantity of bone formation was evaluated using regenerate mapping and histomorphometric analysis. Qualitative evaluation was performed based on bone mineral density and Vickers microhardness (μHV) testing. Postoperative seromas were observed in 83.3% of group 1 dogs only. Group 1 showed significantly larger physical dimensions than group 2 in most regenerate zones. Successful regeneration was achieved in 83.3% of group 1 dogs (discontinuity defect was seen in 1 of 6 dogs in group 1). Meanwhile, none of the 5 dogs in group 2 could be considered to have undergone successful regeneration (3 dogs had discontinuity defects, bony union occurred only in the basal third in the fourth dog, and the last dog showed union with only a shell of bone). The percent bone area and percent defect filling were significantly higher in group 1 than in group 2 (percent bone area, 52.4% ± 5.6% in group 1 and 36.6% ± 11.2% in group 2 [P = .02]; percent defect filling, 56.3% ± 5.5% in group 1 and 38.5% ± 10.8% in group 2 [P = .01]). Group 1 showed higher bone mineral density (0.7 ± 0.3 mg/cm3 in group 1 and 0.4 ± 0.1 mg/cm3 in group 2, P = .1). Finally, μHV was significantly higher in group 1 (20.3 ± 2.6 μHV) than in group 2 (13.2 ± 2.4 μHV) (P = .01). Delaying the application of rhBMP2/ACS for 4 weeks attenuated the quantity and quality of regenerated bone in mandibular segmental defects.

Link to Article

http://dx.doi.org/10.1016/j.joms.2012.12.018

Trabecular bone adaptation to loading in a rabbit model is not magnitude-dependent

Authors

Xu Yang, Bettina M. Willie1, Jocelyn M. Beach1, Timothy M. Wright, Marjolein C. H. van der Meulen, Mathias P. G. Bostrom

Abstract

Although mechanical loading is known to influence trabecular bone adaptation, the role of specific loading parameters requires further investigation. Previous studies demonstrated that the number of loading cycles and loading duration modulate the adaptive response of trabecular bone in a rabbit model of applied loading. In the current study, we investigated the influence of load magnitude on the adaptive response of trabecular bone using the rabbit model. Cyclic compressive loads, producing peak pressures of either 0.5 or 1.0 MPa, were applied daily (5 days/week) at 1 Hz and 50 cycles/day for 4 weeks post-operatively to the trabecular bone on the lateral side of the distal right femur, while the left side served as an nonloaded control. The adaptive response was characterized by microcomputed tomography and histomorphometry. Bone volume fraction, bone mineral content, tissue mineral density, and mineral apposition rate (MAR) increased in loaded limbs compared to the contralateral control limbs. No load magnitude dependent difference was observed, which may reflect the critical role of loading compared to the operated, nonloaded contralateral limb. The increased MAR suggests that loading stimulated new bone formation rather than just maintaining bone volume. The absence of a dose-dependent response of trabecular bone observed in this study suggests that a range of load magnitudes should be examined for biophysical therapies aimed at augmenting current treatments to enhance long-term fixation of orthopedic devices.

Link to Article

http://dx.doi.org/10.1002/jor.22316

Bone response to biomimetic implants delivering BMP-2 and VEGF: An immunohistochemical study

Authors

Mustafa Ramazanoglua, Rainer Lutzb, Philipp Ruscheb, Levent Trabzonc, Gamze Torun Kosed, Christopher Prechtlb, Karl Andreas Schlegelb

Abstract

This animal study evaluated bone healing around titanium implant surfaces biomimetically coated with bone morphogenic protein-2 (BMP-2) and/or vascular endothelial growth factor (VEGF) by examining bone matrix proteins and mineralisation. Five different implant surfaces were established: acid-etched surface (AE), biomimetic calcium phosphate surface (CAP), BMP-2 loaded CAP surface, VEGF loaded CAP surface and dual BMP-2 + VEGF loaded CAP surface. The implants were inserted into calvariae of adult domestic pigs. For the comparison of osteoconductive capacity of each surface, bone mineral density and expression of bone matrix proteins (collagen I, BMP-2/4, osteocalcin and osteopontin) inside defined chambers around the implant were assessed using light microscopy and microradiography and immunohistochemical analysis at 1, 2 and 4 weeks. In the both groups delivering BMP-2, the bone mineral density was significantly enhanced after 2 weeks and the highest value was measured for the group BMP + VEGF. In the group VEGF, collagen I and BMP-2/4 expressions were significantly up-regulated at the first and second weeks. The percentage of BMP-2/4 positive cells in the group BMP + VEGF was significantly enhanced compared with the groups AE and CAP at the second week. Although the highest osteocalcin and osteopontin expression values were observed for the group BMP + VEGF after 2 weeks, no statistically significant difference in osteocalcin and osteopontin expressions was found between all groups at any time. It was concluded that combined delivery of BMP-2 and VEGF favoured bone mineralisation and expression of important bone matrix proteins that might explain synergistic interaction between both growth factors.

Link to Article

http://dx.doi.org/10.1016/j.jcms.2013.01.037