An ORMOSIL-containing orthodontic acrylic resin with concomitant improvements in antimicrobial and fracture toughness properties

Global increase in patients seeking orthodontic treatment creates a demand for the use of acrylic resins in removable appliances and retainers. Orthodontic removable appliance wearers have a higher risk of oral infections that are caused by the formation of bacterial and fungal biofilms on the appliance surface. Here, we present the synthetic route for an antibacterial and antifungal organically-modified silicate (ORMOSIL) that has multiple methacryloloxy functionalities attached to a siloxane backbone (quaternary ammonium methacryloxy silicate, or QAMS). By dissolving the water-insoluble, rubbery ORMOSIL in methyl methacrylate, QAMS may be copolymerized with polymethyl methacrylate, and covalently incorporated in the pressure-processed acrylic resin. The latter demonstrated a predominantly contact-killing effect on Streptococcus mutans ATCC 36558 and Actinomyces naselundii ATCC 12104 biofilms, while inhibiting adhesion of Candida albicans ATCC 90028 on the acrylic surface. Apart from its favorable antimicrobial activities, QAMS-containing acrylic resins exhibited decreased water wettability and improved toughness, without adversely affecting the flexural strength and modulus, water sorption and solubility, when compared with QAMS-free acrylic resin. The covalently bound, antimicrobial orthodontic acrylic resin with improved toughness represents advancement over other experimental antimicrobial acrylic resin formulations, in its potential to simultaneously prevent oral infections during appliance wear, and improve the fracture resistance of those appliances.published_or_final_versio

Long-term antimicrobial activity of an ORMOSIL-containing orthodontic methacrylate resin: biomass

Poster Session - Dental Materials 9: Other Materials - Chemistry, Properties and Performance: abstract no. 662OBJECTIVES: To measure the aging effect on antimicrobial activity of a novel, ORMOSIL-containing dental resin using percent live microorganism count at the disk surface as the ass…link_to_OA_fulltex

Long-term antimicrobial activity of an ORMOSIL-containing orthodontic methacrylate resin: CFU

Poster Session - Dental Materials 9: Other Materials - Chemistry, Properties and Performance: abstract no. 663OBJECTIVES: To measure the effect of aging on antimicrobial activity of a novel, ORMOSIL-containing dental resin using measurement of colony forming units as the ass…link_to_OA_fulltex

Long-term antimicrobial activity of an ORMOSIL-containing orthodontic methacrylate resin: biomass

Poster Session - Dental Materials 9: Other Materials - Chemistry, Properties and Performance: abstract no. 662OBJECTIVES: To measure the aging effect on antimicrobial activity of a novel, ORMOSIL-containing dental resin using percent live microorganism count at the disk surface as the ass…link_to_OA_fulltex

Effect of water-aging on the antimicrobial activities of an ORMOSIL-containing orthodontic acrylic resin.

Quaternary ammonium methacryloxy silicate (QAMS), an organically modified silicate (ORMOSIL) functionalized with polymerizable methacrylate groups and an antimicrobial agent with a long lipophilic alkyl chain quaternary ammonium group, was synthesized through a silane-based sol–gel route. By dissolving QAMS in methyl methacrylate monomer, this ORMOSIL molecule was incorporated into an auto-polymerizing, powder/liquid orthodontic acrylic resin system, yielding QAMS-containing poly (methyl methacrylate). The QAMS-containing acrylic resin showed a predominant contact-killing effect on Streptococcus mutans (ATCC 35668) and Actinomyces naeslundii (ATCC 12104) biofilms, while inhibiting adhesion of Candida albicans (ATCC 90028) on the acrylic surface. The antimicrobial activities of QAMS-containing acrylic resin were maintained after a 3 month water-aging period. Bromophenol blue assay showed minimal leaching of quaternary ammonium species when an appropriate amount of QAMS (<4 wt.%) was incorporated into the acrylic resin. The results suggest that QAMS is predominantly co-polymerized with the poly(methyl methacrylate) network, and only a minuscule amount of free QAMS molecules is present within the polymer network after water-aging. Acrylic resin with persistent antimicrobial activities represents a promising method for preventing bacteria- and fungus-induced stomatitis, an infectious disease commonly associated with the wearing of removable orthodontic appliances

Synthesis of antimicrobial silsesquioxane-silica hybrids by hydrolytic co-condensation of alkoxysilanes

Organically modified silicates represent an excellent example of organic-inorganic hybrids in materials science. The routes to achieve incorporation of organic functionalities include grafting and co-condensation (one-pot synthesis). Compared with the grafting method, the advantage of one-pot synthesis manifests as the tunability of both mechanical and biological properties. Herein, we report a silsesquioxane-silica hybrid (SqSH) with dual functional groups (alkylammonium and methacrylate chains) synthesized by the hydrolytic co-condensation of one tetraethoxysilane and two alkoxysilanes. Successful co-condensation is validated by attenuated total reflection-Fourier transform infrared (ATR-FTIR), 29Si nuclear magnetic resonance ( 29Si NMR), and thermogravimetric analysis (TGA). 3-(Trimethoxysilyl) propyldimethyloctadecyl ammonium chloride (SiQAC), one of the three precursors, simultaneously serves as a structure-directing agent in the modified St\uf6ber reaction, resulting in SqSH particles with structural hierarchy of both ordered lamellar structure and spherical morphology, as revealed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The SqSH particles bear tunable mechanical properties and, when incorporated into bis-GMA/TEGDMA resin, antimicrobial activities against Streptococcus mutans, Actinomyces naeslundii, and Candida albicans

Comparison of the ICare (R) rebound tonometer with the Goldmann applanation tonometer by experienced and inexperienced tonometrists

© 2008 The Royal College of OphthalmologistsPurpose To assess the agreement between ICare® rebound tonometer and Goldmann applanation tonometer in the hands of experienced and inexperienced tonometrists. Patients and methods Two tonometrists, experienced with both Goldmann applanation tonometry (GAT) and ICare® Tonometry (ICT) measured intraocular pressure (IOP), in a masked fashion, in 100 patients. In another series of 58 patients, ICT was performed by an inexperienced tonometrist and GAT by an experienced tonometrist. Results In approximately 80% of patients, the difference in IOP between GAT and ICT was 2 mmHg in group 1 and 3 mmHg in group 2. The 95% limits of agreement were - 4.0–4.4 mmHg in group 1 and - 6.0–5.0 mmHg in group 2. Conclusion ICT compares reasonably with GAT, in both experienced and inexperienced hands. Its ease of use, portability, and sterility make it an attractive tonometer. Its degree of accuracy in inexperienced hands would make it a useful instrument for health care workers with limited ophthalmic experienceL M Abraham, N C R Epasinghe, D Selva and R Casso