Changes in compressive strength on ageing in glass polyalkenoate (glass-ionomer) cements prepared from acrylic/maleic acid copolymers.
Previous studies have shown that glass-ionomers made from acrylic/maleic copolymers stored in water reach a maximum strength at about 1 week, and after 4 months have become significantly weaker. This finding, which contrasts with the behaviour of glass-ionomers based on poly(acrylic acid), was originally attributed to hydrolytic instability. This interpretation has been tested in the current work. Specimens of glass-ionomer prepared from acrylic/maleic acid copolymer have been stored for up to 4 months in different media, namely deionized water, dry air and vegetable oil, then tested for compressive strength. Specimens were in the form of cylinders of dimensions 6 mm high x 4 mm diameter, and storage temperature was 37 degrees C. Data were analysed using two-way analysis of variance (ANOVA) and in all three media specimens became weaker at 4 months than they had been at 1 week (P < 0.05). However, for the specimens stored in dry air and in water, the 1-week values were not the maximum. The fact that there was a loss of strength under all conditions led to the conclusion that it is not, after all, due to hydrolysis.
Nicholson
J W
JW
Dental Biomaterials Department, King's College, School of Medicine and Dentistry, London, UK.
Abiden
F
F
D000179:Acrylates / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D019245:Compressive Strength; D004355:Drug Stability; D005899:Glass Ionomer Cements / Q000737:chemistry*; D008298:Maleates / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry; D013997:Time Factors; D014867:Water / Q000737:chemistry
D000179:Acrylates; D005899:Glass Ionomer Cements; D008298:Maleates; D011108:Polymers; D014867:Water; C030272:maleic acid