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- DMA (2)
- High pressure DSC (2)
- Phenolic resin (2)
- Post curing (2)
- Reaction kinetic (2)
- Bone regeneration (1)
- Calcium phosphat cement (1)
- Computed tomography (1)
- Hard object collisions (1)
- Large animal model sheep (1)
BACKGROUND CONTEXT:
Bioresorbable calcium phosphate cement (CPC) may be suitable for vertebroplasty/kyphoplasty of osteoporotic vertebral fractures. However, additional targeted de-
livery of osteoinductive bone morphogenetic Proteins (BMPs) in the CPC may be required to counteract the augmented local bone catabolism and support complete bone regeneration.
PURPOSE:
This study aimed at testing an injectable, poly (l-lactide-co-glycolide) acid (PLGA) fiber-reinforced, brushite-forming cement (CPC) containing low-dose bone morphogenetic Protein BMP-2 in a sheep lumbar osteopenia model.
STUDY DESIGN/ SETTING:
This is a prospective experimental animal study.
METHODS:
Bone defects (diameter 5 mm) were generated in aged, osteopenic female sheep and filled with fiber-reinforced CPC alone (L4; CPC+ fibers) or with CPC containing different dosages of BMP-2 (L5; CPC+ fibers + BMP-2; 1, 5, 100, and 500g BMP-2; n=5 or 6 each). The results were
compared with those of untouched controls (L1). Three and 9 months after the operation, structural and functional effects of the CPC (±BMP-2) were analyzed ex vivo by measuring
(1) bone Mineral density (BMD);
(2) bone structure, that is, bone volume/total volume (assessed by micro-computed tomography [micro-CT] and histomorphometry), trabecular thickness, and trabecular number;
(3) bone formation, that is, osteoid volume/bone volume, osteoid surface/bone surface, osteoid thickness, mineralizing surface/bone surface, mineral Apposition rate, and bone formation rate/bone surface;
(4) bone resorption, that is, eroded surface/bone surface; and
(5) compressive strength.
RESULTS:
Compared with untouched controls (L1), CPC+ fibers (L4) and/or CPC+ fibers + BMP-2(L5) significantly improved all parameters of bone formation, bone resorption, and bone structure.
These effects were observed at 3 and 9 months, but were less pronounced for some parameters at 9 months. Compared with CPC without BMP-2, additional significant effects of BMP-2 were demonstrated for bone structure (bone volume/total volume, trabecular thickness, trabecular number) and formation (osteoid surface/bone surface and mineralizing surface/bone surface), as well as for the compressive strength. The BMP-2 effects on bone Formation at 3 and 9 months were dose-dependent, with 5–100g as the optimal dosage.
CONCLUSIONS:
BMP-2 significantly enhanced the bone formation induced by a PLGA fiber-reinforced CPC in sheep lumbar osteopenia. A single local dose as low as ≤100g BMP-2 was sufficient
to augment middle to long-term bone formation. The novel CPC+ BMP-2 may thus represent an alternative to the bioinert, supraphysiologically stiff polymethylmethacrylate cement presently used to treat osteoporotic vertebral fractures by vertebroplasty/kyphoplasty.
In this in vitro study, the protective qualities of different mouthguard types were examined during small hard object collisions. The aim was to investigate inconclusive aspects of hard inserts, nylon nets, and air spaces as reinforcements in the anterior region and the protection qualities of ethylene vinyl acetate (EVA).
Five different mouthguards with a labial thickness between 2 mm and 11 mm made of materials of varying stiffness were investigated. As a negative control, the same experiments were performed without a mouthguard. Different combinations of EVA and labial inserts ((polyethylene terephthalate glycol-modified [PETG]), nylon mesh, air space) were tested. Using a stainless steel pendulum device, blows of different energy (0.07-2.85 joules) were applied to the center of the crown of a pivoted tooth in a custom-built jaw model. A laser Doppler vibrometer measured the tooth deflection, while an acceleration sensor attached to the pendulum measured the braking accelerations.
Tooth deflection was reduced up to 99.7% compared to no mouthguard, and the braking acceleration was reduced up to 72.2% by increasing the mouthguards' labial thickness in combination with labial inserts of different stiffness and a built-in air space between the front teeth and the mouthguard. The mouthguards made of soft materials (EVA with nylon mesh) showed slightly better protection qualities than the more rigid mouthguards of similar thickness (PETG; P<.05). However, with increasing impact energy, their protective capacities decreased to a greater extent than the stiffer mouthguards.
The combination of increased labial thickness and labial inserts of varying stiffness and eventually an air space offers the best protection capacities for hard, small object collisions.