Effects of long-term storage on properties of an alginate impression material.
BACKGROUND
Storage stability is a critical characteristic for perishable dental materials.


OBJECTIVE
The purpose of this shelf-life study was to document changes in the properties of an alginate impression material on exposure to various environmental conditions for more than 78 months.


METHODS
Properties measured included recovery from deformation, strain in compression, compressive strength, tear strength, working time, and creep compliance.


RESULTS
Results revealed increases in strength and working time and a decrease in recovery from deformation at 30 to 50 months: strength and recovery then remained constant past 6 years, whereas working time and creep compliance decreased. Only the most stressful environmental conditions (heat and humidity) caused spontaneous failure of the material to set.


CONCLUSIONS
We concluded that, under most storage conditions, properties of the alginate material tested remain within ADA specification limits well past manufacturer's designated shelf life. ADA specifications should require manufacturers to verify that the shelf life of each perishable material is based on valid data. An accelerated aging test was developed to simulate real time property changes and to assist in evaluating similar materials.
Hondrum
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SO
Walter Reed Army Institute of Research, Washington, D.C., USA.
Fernandez
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D000464:Alginates / Q000737:chemistry* / Q000592:standards; D000704:Analysis of Variance; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003187:Compliance; D019245:Compressive Strength; D003760:Dental Impression Materials / Q000737:chemistry* / Q000592:standards; D004355:Drug Stability; D004356:Drug Storage; D004781:Environmental Exposure; D006358:Hot Temperature; D006813:Humidity; D008422:Materials Testing; D008970:Molecular Weight; D015203:Reproducibility of Results; D013314:Stress, Mechanical; D013718:Tensile Strength; D013997:Time Factors
D000464:Alginates; D003760:Dental Impression Materials