Novel Dental Cements Based On Cyanoacrylates Susannah Tomlinson March 2007 Bill Hooper, Ken Evans, Oana Ghita

Aim/Overview Aim: to study the setting characteristics of new cements using various techniques Cement compositions Applications Oscillating rheometry Mid- and near-IR spectroscopy Vickers hardness Shear bond strength

Cement Compositions (A.J. Bennetts, C.G. Wilde, and A.D. Wilson, UK patent GB ) Hybrids Cyanoacrylate + GIC (acid solution + basic glass) Set by:(1) cyanoacrylate polymerisation (2) GIC acid-base reaction Similar to resin-modified GICs Composites Cyanoacrylate adhesive + acid-coated fillers (e.g. GIC (glass), hydroxyapatite, or wollastonite powders, etc., coated with tartaric acid and poly(acrylic acid)) Set by cyanoacrylate polymerisation

Cyanoacrylates Ethyl cyanoacrylate (R=C 2 H 5 ) n-butyl cyanoacrylate (R=C 4 H 9 ) Polymerisation initiated by water ideal in oral environments Incorporation of cyanoacrylate is expected to improve adhesion

Applications General adhesive Pre-fabricated surgical implants or prostheses Dental adhesives, restorative materials, luting agents, liners, and as endodontic cements

Oscillating Rheometry Wilson rheometer Cement placed between one stationary plate and one oscillating Plates coated with GIC to prevent irreversible bonding Working time: when oscillation amplitude is 95% of original Setting time: when oscillation amplitude is 5% of original Ideal setting characteristics: high working:setting time ratio (close to 1) Time Oscillation amplitude

Rheometry results All new cement formulations have similar or higher working-time:setting-time ratios than GIC

Near-IR (transflectance set-up): clear peaks related to cyanoacrylate Mid-IR (diamond ATR): clear peaks related to GIC Mid-IR and near-IR spectroscopy

Typical mid-IR spectra of hybrid cement Shows that the cyanoacrylate polymerisation is rapid Slow GIC reaction, continuing after cyanoacrylate polymerisation complete

Extent of cyanoacrylate cure from near-IR Cyanoacrylate polymerisation rapid in hybrid, in agreement with mid-IR For the composite, shape of cyanoacrylate polymerisation profile possibly due to the limited amount of water adsorbed on the powder surface

Ethyl cyanoacrylate/GIC hybrid Cyanoacrylate component 100% cured in ~10 min, which suggests that the increasing hardness is due to the continuing GIC acid-base reaction

Hardness of composite correlated with cyanoacrylate extent of cure Ethyl cyanoacrylate/hydroxyapatite composite

Shear bond strength to Al* *ASTM D using a single-lap-joint design

Summary New cements show favourable handling characteristics (high W:S time ratio) In hybrid: cyanoacrylate polymerisation is rapid, while GIC reactions are slower, and continue after polymerisation is complete Hybrid shows improved bond strength to metal next experiments will study bonding to teeth

Thanks for your attention!