The effect of mixing time on the handling and compressive strength of an encapsulated glass-ionomer cement

Abstract

The effects of varying mixing times on the properties of glass-ionomer cements have been poorly investigated, and many clinicians are uninformed about the potential changes in handling achieved by this. This study aims to explore the effects of mixing time variation. An experimental glass-ionomer system was dosed into a capsule, activated, and triturated for varying lengths of time, from 2 to 14 s. Measurements were made of working time, initial setting time, compressive strength and compressive modulus, and a subjective assessment of handling conducted. The working time and initial setting time decreased as mixing time increased, while compressive strength and compressive modulus increased to a maximum at 12 s mixing time. The material essentially pre-gelled after 14 s of mixing, which resulted in breaking of the gel matrix and poorer properties. Clinicians should feel confident, within limits, of varying mixing times of glass ionomer cements to improve properties or to slow the reaction.