The Evolution of Dental Materials over the Past Century: Silver and Gold to Tooth Color and Beyond.

The field of dental materials has undergone more of a revolution than an evolution over the past 100 y. The development of new products, especially in the past half century, has occurred at a staggering pace, and their introduction to the market has been equally impressive. The movement has mostly come in the area of improved esthetics, marked by the gradual replacement of dental amalgam with dental composite and all-metal and porcelain-fused-to-metal indirect restorations with reinforced dental ceramics, all made possible by the rapid improvements in dental adhesive materials. This article covers the time course of dental materials development over the past century in which the Journal of Dental Research has been published. While there have been advances in nearly all materials used in the field, this article focuses on several areas, including dental amalgam, dental composites and light curing, dental adhesives and dental cements, ceramics, and new functional repair materials. A few short statements on future advances will be included at the end

Origin of micro-scale heterogeneity in polymerisation of photo-activated resin composites

Photo-activated resin composites are widely used in industry and medicine. Despite extensive chemical characterisation, the micro-scale pattern of resin matrix reactive group conversion between filler particles is not fully understood. Using an advanced synchrotron-based wide-field IR imaging system and state-of-the-art Mie scattering corrections, we observe how the presence of monodispersed silica filler particles in a methacrylate based resin reduces local conversion and chemical bond strain in the polymer phase. Here we show that heterogeneity originates from a lower converted and reduced bond strain boundary layer encapsulating each particle, whilst at larger inter-particulate distances light attenuation and monomer mobility predominantly influence conversion. Increased conversion corresponds to greater bond strain, however, strain generation appears sensitive to differences in conversion rate and implies subtle distinctions in the final polymer structure. We expect these findings to inform current predictive models of mechanical behaviour in polymer-composite materials, particularly at the resin-filler interface

Characterisation and microleakage of a new hydrophilic fissure sealant – UltraSeal XT® hydro™

Objectives: The new hydrophilic fissure sealant, UltraSeal XT® hydro™ (Ultradent Products, USA), was characterised and its in vitro resistance to microleakage after placement on conventionally acid etched and sequentially lased and acid etched molars was investigated. Materials and Methods: The sealant was characterised by Fourier transform infra-red spectroscopy, (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and Vickers indentation test. Occlusal surfaces of extracted human molars were either conventionally acid etched (n = 10), or sequentially acid etched and laser irradiated (n = 10). UltraSeal XT® hydro™ was applied to both groups of teeth which were then subjected to 2500 thermocycles between 5 and 55 °C prior to microleakage assessment by fuchsin dye penetration. Results: UltraSeal XT® hydro™ is an acrylate-based sealant which achieved a degree of conversion of 50.6 ± 2.2% and a Vickers microhardness of 24.2 ± 1.5 under standard light curing (1000 mWcm-2 for 20 s). Fluoride ion release was negligible within a 14-day period. SEM and EDX analyses indicated that the sealant comprises irregular sub-micron and nano-sized silicon-, barium- and aluminium-bearing filler phases embedded within a ductile matrix. Laser preconditioning was found to significantly reduce microleakage (Mann-Whitney U test, p < 0.001). The lased teeth presented enhanced surface roughness on a 50 to 100 μm scale which caused the segregation and concentration of the filler particles at the enamel-sealant interface. Conclusion: Laser preconditioning significantly decreased microleakage and increased enamel surface roughness which caused zoning of the filler particles at the enamel-sealant interface

Investigation on synthesis and properties of isosorbide based bis-GMA analogue

The aim of this work was to synthesize and investigate properties of a novel dimethacrylic monomer based on bioderived alicyclic diol—isosorbide. Its potential as a possible substitute of 2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy)phenyl]propane (BISGMA), widely used in dental restorative materials and suspected for toxicity was assessed. The novel monomer was obtained in a three-step synthesis. First, isosorbide was etherified by a Williamson nucleophilic substitution and subsequently oxidized to isosorbide diglycidyl ether (ISDGE). A triphenyl phosphine catalyzed addition of methacrylic acid to ISDGE resulted in 2,5-bis(2-hydroxy-3-methacryloyloxypropoxy)- 1,4:3,6-dianhydro-sorbitol (ISDGMA). The monomer obtained was photopolymerized using camphorquinone/2-(dimethylamino)ethyl methacrylate initiating system. Next, compositions with triethylene glycol dimethacrylate (TEGDMA) were prepared and polymerized. Double bond conversion, polymerization shrinkage and water sorption of resulting polymers were determined. Selected mechanical (flexular strength and modulus, Brinell hardness) and thermomechanical (DMA analysis) properties were also investigated. BISGMA based materials were prepared as reference for comparison of particular properties