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.

The objective of this study was to identify through quantum mechanical quantitative structure activity relationships (Q-QSARs) chemical structures in dental monomers that influence their mutagenicity. AMPAC, a semiempirical computer program that provides quantum mechanical information for chemical structures, was applied to three series of reference chemicals: a set of methacrylates, a set of aromatic and a set of aliphatic epoxy compounds. QSAR models were developed using this chemical information together with mutagenicity data (Salmonella TA 100, Ames Test). CODESSA, a QSAR program that calculates quantum chemical descriptors from information generated by AMPAC and statistically matches these descriptors with observed biological properties was used. QSARs were developed which had r2 values exceeding 0.90 for each study series. These QSARs were used to accurately predict the mutagenicity of BISGMA. a monomer commonly used in dentistry, and two epoxy monomers with developing use in dentistry, GY-281 and UVR-6105. The Q-QSAR quantum mechanical descriptors correctly predicted the level of mutagenicity for all three compounds. The descriptors in the correlation equation pointed to components of structure that may contribute to mutagenesis. The QSARs also provided 'dose windows' for testing mutagenicity, circumventing the need for extensive dose exploration in the laboratory. The Q-QSAR method promises an approach for biomaterials scientists to predict and avoid mutagenicity from the chemicals used in new biomaterial designs.

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For proper bonding of resin composite restorations dentin should be etched to remove the smear layer and to create a layer of etched dentin, which after the infiltration with adhesive resin is called the hybrid layer. The mechanical properties of the dentin-composite interface ( Fig. 1) are of immense importance to the durability of dental restorations, but it has been found that teeth restored under in-vivo conditions have lower microtensile bond strengths than teeth restored in the laboratory [1] because intrinsic fluid under positive pulpal pressure can permeate the dentin surface [2].In this study, human teeth (with IRB approval) were restored a) without pulpal pressure and b) with artificial positive pulpal pressure of 5.0 cm water pressure to simulate a tooth anesthetized with epinephrine. Five adhesive systems from different manufacturers were used for restorations (Clearfil-SE, OneStep Plus, Peak-SE, Prompt L Pop and PQ1.) Twenty four hours after the restoration, all teeth were sectioned to obtain rectangular beam-shaped specimens with a cross section of ~ 0.5 mm 2 with no notch at the adhesive junction. Microtensile tests showed that for all adhesives but Clearfil-SE, the application of positive pulpal pressure reduced the bond strength [3]. The fractographic features of specimens treated with Clearfil-SE were similar regardless of whether the specimens were prepared under positive pressure or not (Fig. 2). The most common feature of specimens with low mechanical properties, treated under pressure with OneStep Plus, Peak-SE and PQ1, was a smooth fracture along the hybrid layer-adhesive interface (Fig. 3a). This fractogram is very similar to the image of a wet specimen of etched dentin (without adhesive application) as seen in an environmental SEM (Fig. 3b), with the exception of the presence of fractured resin tags in dental tubules in Fig. 3a. That similarity suggested minimal differences between the sample that was acid etched and treated with an application of adhesive compared to the sample whose dentin was only acid etched. The smoothness of the fracture surface suggested a very weak adhesion of the adhesive layer to hybrid layer. To check the integrity of the hybrid layer, ultrathin sections for TEM imaging were cut from the specimen shown in Fig. 3a (along with a specimen prepared without pulpal pressure). No embedding was performed, because electron densities of embedding resin and adhesive resin are approximately the same, so these resins could be undistinguishable in TEM. While the specimen treated without pulpal pressure had a well infiltrated hybrid layer and resin tags in tubules (Fig. 4a), the specimen treated with positive pressure had resin only in tubules and no hybrid layer, which suggests that no real infiltration occurred and that adhesive resin formed only a thin layer on the top of etched dentin layer. This conclusion was confirmed by observation of the specimen which had very low tensile strengths (7.8 Mpa) and clearly demonstrated "smooth regions" formed by resin films detached f...

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