Stimulation of bone formation by a swelling endosseous implant

Abstract

As previously reported,'q2 a polymer-ceramic composite designed for endosseous implant applications has been developed. The composites were prepared by the free-radical polymerization of an acrylic acid solution and a difunctional acrylate in the presence of 0.3 pm akunina powder. Mechanical testing indicated that the material had a compressive yield strength of 89-102 MPa (13-15 ksi) and an elastic modulus of 2055-2740 MPa (300-400 ksi). The average porosity of the composite was determined to be in the range of 50-55 ~0 1 % .A unique property of this material is its ability to gradually swell in aqueous media to a degree which can be precisely controlled via the extent of matrix cross-linking. The present material was designed to obtain an equilibrium swelling level of 15-25 vol % in Ringers solution a t 40OC. The advantages of such controlled swelling in an endosseous implant material are twofold. First, it allows for rapid adaptation of the prosthesis to the contour of the socket. Second, it induces a state of compressive stress around the implant site. It has been suggested that the presence of such a force field will result in the stimulation of bone f o r m a t i~n .~~ This paper reports the initial results obtained from a series of animal implantation experiments utilizing this swelling composite material. EXPERIMENTAL PROCEDURESix adult mongrel dogs were used in these experiments. Following standard aseptic procedures, four holes were made in each canine femoral shaft with a 3/16-in. (4.76 mm) Michelle 1aminect.omy trephine. Cylindrical implant specimens which had been machined to a diameter of 4.65-4.67 mm were placed in the right femur of each animal.Approximately 4 weeks later, additional specimens were inserted into the animal's left

Synthesis and characterization of a poly(methyl methacrylate-acrylic acid) copolymer for bioimplant applications

“…It has been reported that AMA is a fairly good cross-linker for PAA [1][2][3] and a relatively weak The fact that these clusters were unreacted monomers (not initiator) was ascertained from the cross-linker for PMMA. 10 It has also been reported 10 that DEGDMA is a better cross-linker smell of the liquid in these clusters and noting that the initiator used here is solid.…”

“…1 These swelling-type im-(this determines how long the patient has to be plants were proposed as means of enhancing the bedridden); low loss of mechanical properties fixation characteristics of implants in bone. The with swelling; elastic stiffness close to that of bone concept involved swelling of the implant by ab-(high stiffness of current metallic implants is sorption of body fluids and achieving fixation at known to cause bone resorption due to stress the implant-bone interface by an expansion-fit shielding); and excellent failure resistant propermechanism.…”

“…We have also conducted a detailed study of the swelling behavior animals, and favorable bone remodeling response was documented. 1 However, mechanical tests in of the cross-linked copolymer. An excess saline solution was used as the solvent in the swelling dry and saturated conditions revealed high losses in both strength and modulus with swelling, makstudies because it closely reproduces the environment in the human body.…”

“…AMA was chosen in the place of alumina particles. Mechanical tests on the three dimensionally braided graphbased on the previous studies of Kamel and coworkers, [1][2][3] which showed that AMA is an effecite -polyacrylic acid composite in dry and saturated conditions once again revealed high losses tive cross-linking agent for PAA polymer systems polymerized in bulk. DEGDMA, on the other in both strength and modulus with swelling.…”

“…The decomposite. 1 Polyacrylic acid (PAA) is known to be a hydrophilic biocompatible polymer with very high swelling strains. Cross-linking and nanoscale alumina particles were introduced to limit state.…”