Borate bioactive glasses are biocompatible and enhance new bone formation, but the effect of their microstructure on bone regeneration has received little attention. In this study scaffolds of borate bioactive glass (1393B3) with three different microstructures (trabecular, fibrous, and oriented) were compared for their capacity to regenerate bone in a rat calvarial defect model. 12 weeks post-implantation the amount of new bone, mineralization, and blood vessel area in the scaffolds were evaluated using histomorphometric analysis and scanning electron microscopy. The amount of new bone formed was 33%, 23%, and 15%, respectively, of the total defect area for the trabecular, oriented, and fibrous microstructures. In comparison, the percent new bone formed in implants composed of silicate 45S5 bioactive glass particles (250–300 μm) was 19%. Doping the borate glass with copper (0.4 wt.% CuO) had little effect on bone regeneration in the trabecular and oriented scaffolds, but significantly enhanced bone regeneration in the fibrous scaffolds (from 15 to 33%). The scaffolds were completely converted to hydroxyapatite within the 12 week implantation. The amount of hydroxyapatite formed, 22%, 35%, and 48%, respectively, for the trabecular, oriented, and fibrous scaffolds, increased with increasing volume fraction of glass in the as-fabricated scaffold. Blood vessels infiltrated into all the scaffolds, but the trabecular scaffolds had a higher average blood vessel area compared with the oriented and fibrous scaffolds. While all three scaffold microstructures were effective in supporting bone regeneration, the trabecular scaffolds supported more bone formation and may be more promising in bone repair.

While great strides have been made in the design of dental composites and orthopaedic implants, improvements are still needed. For instance the life span of dental polymer composites is known to be significantly shorter than traditional amalgam restorations [1]. Similarly, the early failure rate of orthopaedic implants often leads to an intentional delay in the treatment of painful, debilitating joints to ensure patients don’t outlive the functional life of their prosthetics [2]. Stress concentrations within biomaterials may be partially to blame for these premature failures.

Methyl methacrylate used in bone cements has drawbacks of toxicity, high exotherm, and considerable shrinkage. A new resin, based on silorane/oxirane chemistry, has been shown to have little toxicity, low exotherm, and low shrinkage. We hypothesized that silorane-based resins may also be useful as components of bone cements as well as other bone applications and began testing on bone cell function in vitro and in vivo. MLO-A5, late osteoblast cells, were exposed to polymerized silorane (SilMix) resin (and a standard polymerized bisGMA/TEGDMA methacrylate (BT) resin and compared to culture wells without resins as control. A significant cytotoxic effect was observed with the BT resin resulting in no cell growth, whereas in contrast, SilMix resin had no toxic effects on MLO-A5 cell proliferation, differentiation, nor mineralization. The cells cultured with SilMix produced increasing amounts of alkaline phosphatase (1.8-fold) compared to control cultures. Compared to control cultures, an actual enhancement of mineralization was observed in the silorane resin-containing cultures at days 10 and 11 as determined by von Kossa (1.8-2.0 fold increase) and Alizarin red staining (1.8-fold increase). A normal bone calcium/phosphate atomic ratio was observed by elemental analysis along with normal collagen formation. When used in vivo to stabilize osteotomies, no inflammatory response was observed, and the bone continued to heal. In conclusion, the silorane resin, SilMix, was shown to not only be non cytototoxic, but actually supported bone cell function. Therefore, this resin has significant potential for the development of a nontoxic bone cement or bone stabilizer.

Bioactive glasses are biocompatible materials that convert to hydroxyapatite in vivo, and potentially support bone formation, but have mainly been available in particulate and not scaffold form. In this study, borosilicate and borate bioactive glass scaffolds were evaluated in critical-sized rat calvarial defects. Twelve-week-old rats were implanted with 45S5 silicate glass particles and scaffolds of 1393 silicate, 1393B1 borosilicate, and 1393B3 borate glass. After 12 weeks, the defects were harvested, stained with hematoxylin and eosin to evaluate bone regeneration, Periodic Acid Schiff to quantitate blood vessel area, and von Kossa and backscatter SEM to estimate newly mineralized bone and hydroxyapatite conversion of bioactive glasses. The amount of new bone was 12.4% for 45S5, 8.5% for 1393, 9.7% for 1393B1, and 14.9% for 1393B3 (*p = 0.04; cf. 1393 and 1393B1). Blood vessel area was significantly higher (p = 0.009) with 45S5 (3.8%), with no differences among 1393 (2.0%), 1393B1 (2.4%), or 1393B3 (2.2%). Percent von Kossa-positive area was 18.7% for 45S5, 25.4% for 1393, 29.5% for 1393B1, and 30.1% for 1393B3, significantly higher (p = 0.014) in 1393B1 and 1393B3 glasses than in 45S5. 45S5 and 1393B3 converted completely to HA in vivo. The 1393B3 glass provided greater bone formation and may be more promising for bone defect repair due to its capacity to be molded into scaffolds. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A 100A:3267-3275, 2012.

A summary is not available for this content so a preview has been provided. Please use the Get access link above for information on how to access this content.

The aesthetic appeal of composite-resin restoratives promotes their use, however their functional life is significantly shorter when compared to their metal counterparts.1 One possible reason is the effect of polymerization stress on marginal integrity. Shrinkage of the composite, and its associated stress, has been found to cause gap formation and stress interactions between the restorative and the adhesive. These gaps offer an ideal niche for bacteria, and, when compounded by the mechanical strain of chewing, can lead to premature failure of the restorative.2,3 Additionally, it is well known that incomplete conversion of the double bonds occurs during methacrylate polymerizations.4–7 A high degree of conversion is needed to prevent the presence of potentially hazardous monomers.8

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.

Two series of silicate glasses were processed to micron-size, sub-micron size, and nanoparticles using three different milling systems: ball milling, attrition, and high-energy milling. The effect of milling time and media size on particle size and contamination were investigated in aqueous and isopropanol suspensions. The particle size was determined using a laser-diffraction particle size analyzer and scanning electron microscopy. The smallest glass particles with a median particle size of 0.3 µm were achieved by a two-step comminution process in a high energy mill.

There has been little change in the formulation of bone cements since Sir John Charnley first developed them in the 1970s. Bone cements are methacrylate based systems packaged in two components [1]. The powder component contains a mixture of polymethyl methacrylate (PMMA), methyl methacrylate-styrene-copolymer, and a radio opacifier (either barium sulfate or zirconium oxide) [2]. The second component is a liquid monomer typically containing methyl methacrylate, N, N-dimethyl-p-toluidine (activator), and hydroquinone. Flexural strength and flexural modulus of bone cements range between 60–75 MPa and 2.2–3.3 GPa, respectively [3, 4]. ISO 5833 requires bone cements to have a strength greater than 50 MPa and a modulus greater than 1.8 GPa [5].

We have synthesized a filler-reinforced silorane composite that has potential applications in orthopaedic surgery, such as for a bone stabilizer. The purpose of the present work was to develop a method for estimating four properties of this material; namely, maximum exotherm temperature, flexural strength, flexural modulus, and fracture toughness. The method involved the use of mixture design-of-experiments and regression analysis of results obtained using 23 formulations of the composite. We validated the estimation method by showing that, for each of four composite formulations that were not included in the method development, the value of each of the aforementioned properties was not significantly different from that obtained experimentally. Our estimation method has the potential for use in the development of a wide range of orthopaedic materials.

Background: Roughened tooth surface facilitates the accumulation of plaque which can be removed by mechanical and chemical methods. Mechanical methods like tooth brushing and conditions like fluorosis may bring about surface changes in teeth. The purpose of the present study was to evaluate the surface roughness changes induced by tooth brushing with different toothbrushes in fluorotic and nonfluorotic teeth and the effect of fluorosis on the surface roughness changes of teeth.

Improvements in body armor and battlefield medical care have resulted in an increase in survival rates but also an increase in survivable battlefield extremity injuries (Covey 2002; Covey 2006; Owens, Kragh et al. 2007). It is well known that these traumatic extremity injuries require adequate stabilization to achieve an optimal healing outcome. Extremity fractures also affect a large proportion of the civilian population. In 2005, 5.7 million Americans suffered an injury resulting in bone fracture (CDC/NCHS). Transport of these domestically injured individuals to medical facilities also requires stabilization to avoid further injury.