The effect of expiration date on mechanical properties of resin composites

Abstract

Objective:The aim of this in vitro study is to evaluate the effect of expiration date on some mechanical properties of resin composites after controlled storage of syringes and compules in a refrigerator at 4°C.Materials and Methods:Specimens were tested at 7 days after storage in distilled water at room temperature. The investigated properties are the static modulus of elasticity, the flexural strength, and the Vickers microhardness. Same batches of restorative materials were examined at baseline (at least 1 year before their expiration date) and 1 year after they expired.Results:Paired t-test is used to compare the results between the two groups using StatView software (version 5.0) SAS Campus Drive Cary, North Carolina, USA. Except for the flexural strength, no statistical differences were found between the mechanical properties of the expired and the unexpired group.Conclusion:The 1-year expiry date did not seem to affect the investigated mechanical properties.

Evaluation of Mechanical Properties of Expired and Non-Expired Resin Composite. A Comparative Study

“…In the present study, the results of the specimen's mean degree of conversion showed no significant difference between the three tested groups at P-value = 0.096 (E-0: 1.48 ± 0.14; E-6: 1.68 ± 0.20; E-12: 1.74 ± 0.18). These results were in agreement with Sabbagh et al who found that there is no significant difference on some mechanical properties between expired and non-expired resin composite [3] . However, these results was contradicted by Garcia et al [16] who evaluated the degree of conversion and other mechanical properties on resin composite past their expiration date by 180 days and found inferior properties than that of unexpired materials [5] .…”

“…Again, these results were in accordance with Sabbagh et al who studied the effect of expiration date of resin composite on microhardness and found no change in the mechanical properties of resin composite in terms of microhardness between unexpired and 1-year expired resin composite resin. The microhardness results that showed non-significant difference between expired and unexpired resin composite were explained on the basis that resin composite behavior may be greatly affected by the organic part rather than inorganic part that con- tains fillers beside coupling agent not affected [3] . On the contrary, the results was contradicted by that of Tirapelli et al who found a significant decrease in the microhardness of expired resin composites compared to non-expired ones [6] .…”

“…Other studies found a reduction in inorganic part in terms of filler particles of resin composite when kept in liquid medium or stored for long periods and so the mechanical properties of light cured resin composites are highly dependent on the concentration of the filler particles, degree of polymerization and also the concentration of the photo initiator and consequently if this concentrations reduced the composite material will suffer degradation after its labeled shelf life [6] . Sabbagh et al, gave another explanation regarding inferior properties of expired resin composite compared to non-expired ones that there is hydrolysis through ester group linkage within the molecules or siloxane links that are formed with inorganic filler particle of the coupling agent of the expired resin composite and this results in degradation of filler surface and stress transfer generated which cause tearing away of coupling agent from filler surface that finally results in complete debonding [3] . The chemical stability of restorative materials is influenced by the degree of conversion of monmers.…”

“…The degradation process of this polymeric material is complex and observed as intraoral degradation and extraoral degradation due to material storage and shelf life. A lot of materials in dentistry have specific requirements for storage to maintain their properties and their shelf life [3] .…”

“…The expiration date of the polymeric material is a crucial factor that should be taken into consideration, and theoretically if it has been used after its expiration date, the different properties of the material will be affected. Clinically, this may lead to a variety of consequences as discoloration, fracture, excessive wear and others [3] .…”