Iraq – Carrier-based obturation of root canals was first described by Ben Johnson in 1978, and Thermafil (Dentsply Tulsa Dental, Tulsa, OK) was introduced as a carrier based obturation material with a solid core during the 1990s. Obturators have been designed to correspond to the ISO standardised file sizes and to the tapered nickel titanium rotary files.
Plastic carriers of current Thermafil obturators are made of different materials depending on their size. Smaller sizes (up to size #40) use Vectra (Ticona GmbH, Sulzbach, Germany), which is a liquid crystal polymer insoluble in solvents, and larger sizes use polysulfone, which is soluble in chloroform. Common problems reported by clinicians using core-based obturation systems include the lack of apical control, the inability to fill oval-shaped canals, and the difficult removal of the carrier in case of retreatment.
Contemporary carriers include grooves to facilitate the removal of the carriers; however, retrievability remains a problem. Hydroxyapatite-reinforced polyethylene (PE) composites have been successfully used as bone analogue materials and are currently used as middle ear implants. These composites can be rendered flexible, can be tailored to exhibit desirable flow properties, and are biocompatible; thus, they can be excellent candidates for designing carriers for carrier-based obturation systems to fill the root canal space in three dimensions.
Hydroxyapatite (HA) is used in conjunction with strontium oxide (SrO) to achieve adequate radiopacity as required for a carrier material, and the quantity of the ceramic filler assists in the ability to tailor the flexibility of the carriers.
Recently, hydroxyapatite-reinforced polyethylene composites have been developed by Iraqi scientist Dr Raghad Al-Hashimi from College of Dentistry, University of Baghdad in collaboration with researchers from Kings College London, using silanated hydroxyapatite, which enhances the interfacial bonding between the filler and matrix, thus enhancing the properties of the composite. HA low-density PE composites show good potential as carrier materials, and they also show a good adhesion between Gutta Percha (GP) and the composite. The novel Hydroxyapatite (HA)-reinforced polyethylene (PE) composites were found to be suitable as core materials for carrier-based root canal fillings.