Novel Dental CementsBased On Cyanoacrylates

Susannah TomlinsonMarch 2007

Bill Hooper, Ken Evans, Oana Ghita

Aim/OverviewAim: to study the setting characteristicsof 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 2386121)

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=C2H5)

n-butyl cyanoacrylate (R=C4H9) Polymerisation initiated by water

ideal in oral environments CN

CO2R

CC

H

H

CN

C

CO2R

CHO

H

H

+ y H2O

nxy

H

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)

Tim

e

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 1002-05 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!