Hygroscopic Expansion of Aesthetic Restorative Materials: One-Year Report

To measure the long-term linear hygroscopic expansion (LHE) of several materialsusing bulked and layered techniques.Materials and Methods: Seven materials were used; Fuji Cap II, Fuji II LC, Photac-FilAplicap, Vitremer, Dyract, Tetric and Z100. Ten specimens (6×4 mm) were made for eachmaterial using layered and bulked techniques (each group comprises five specimens). Thespecimens were stored in distilled water at 37°C. The length of each specimen was measuredimmediately after preparation, 24 hours, one week, one month, three months, sixmonths, nine months and one year. This was used to calculate the percentage change in thelength of materials. The mean LHE and standard deviation were calculated. Repeatedmeasure analysis and paired sample t-test were used.Results: The type of material and time had a significant effect on LHE. Fuji Cap II andFuji II LC exhibited no significant changes after one-year and one month, respectively.However, layered specimens of Photac-Fil Aplicap and Tetric showed constant expansionuntil six month, whereas bulked specimens reached the constant length at three months.Constant expansion was obtained for layered and bulked specimens of Dyract and Z100 atsix month. Layered specimens of Vitremer showed no significant differences except between24 hours and one year measurements. But in bulked specimens, the results at ninemonths and one year were significantly different from those obtained at three months andbefore.Conclusion: Fuji II showed no significant LHE and resin-modified glass ionomer cements(RMGICs) exhibited the highest LHE. Dyract maintained an intermediate LHE in comparisonwith RMGIC and composite resin.