Is encapsulation of posterior glass-ionomer restoratives the solution to clinically induced variability introduced on mixing?
OBJECTIVE
Three GI restorative systems were evaluated to determine if encapsulated GI restoratives performed more favorably than the hand-mixed equivalents prepared with powder contents progressively decreased from that recommended by manufacturers in 10% increments for a constant weight of liquid which are routinely employed in clinical practice.


METHODS
Mean compressive fracture strengths, associated Weibull moduli and mean elastic moduli were determined for series of 30 nominally identical cylindrical specimens for three hand-mixed GI restoratives prepared with 100-50% of the recommended powder content for a constant weight of liquid and the equivalent encapsulated GI restoratives mechanically mixed in the Capmix or Rotomix machines.


RESULTS
Decreasing the powder content of the three hand-mixed GI restoratives for a constant weight of liquid from that recommended by the manufacturers resulted in a progressive deterioration of the mean compressive fracture strengths and the mean elastic modulus. The elastic modulus was more sensitive than the compressive fracture strength to highlighting the impact of mixing ratio variations in the GI restoratives. There were no significant differences between mean compressive fracture strengths of mechanically mixed encapsulated GI restoratives, however, variations in mean elastic modulus were dependent upon the mixing time employed.


CONCLUSIONS
The employment of an intrinsic material property was more sensitive than a non-intrinsic material property to highlight the impact of mixing ratio variations in hand-mixed restoratives and the effect that the method of mechanical mixing has on encapsulated GI restoratives. Encapsulated GI restoratives are a potential solution to the operator induced variability associated with hand-mixed GI restoratives.
Dowling
Adam H
AH
Materials Science Unit, Division of Oral Biosciences, Dublin Dental School & Hospital, Trinity College Dublin, Dublin 2, Ireland. adam.dowling@dental.tcd.ie <adam.dowling@dental.tcd.ie>
Fleming
Garry J P
GJ
D002214:Capsules; D019245:Compressive Strength; D004548:Elasticity; D005899:Glass Ionomer Cements / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing; D011208:Powders; D012996:Solutions; D013314:Stress, Mechanical; D013499:Surface Properties
D002214:Capsules; C410563:ChemFlex; C439808:Fuji IX GP Fast; D005899:Glass Ionomer Cements; C515713:Ketac Molar Easymix; C424245:Ketac-Molar Aplicap; D011208:Powders; D012996:Solutions; C110713:fuji IX