The flexural strength of repaired glass-ionomer cements

The flexural strength of three glass-ionomer-type cements was measured by means of a four-point bend test. Specimens were tested at one hour and seven days after being mixed. The maleic copolymer materials showed similar strengths at one hour and seven days, while the water-based polyacrylic acid material showed a reduction in strength over the seven-day period. For assessment of the capacity of fresh glass ionomer to bond with old material, further half-length specimens of all materials were prepared and additions made at one hour and seven days. These specimens were tested at one hour and seven days after the addition. There was a considerable reduction in the strength of all specimens where additions had been made. The degree of reduction varied with the type of material. All fractures on the addition specimens occurred at the junction between the two sections.