Self-adhesive resin cements: pH-neutralization, hydrophilicity, and hygroscopic expansion stress
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The objective of the study was to investigate the relationship between pH-neutralization, hydrophilicity, and free hygroscopic expansion stress of self-adhesive resin cements (SARCs) after storage in artificial saliva.
Materials and methods
The SARCs RelyX Unicem Automix 2 (RX2, 3 M ESPE), iCEM (iCEM, Heraeus) and Maxcem Elite (MCE, Kerr) were under investigation in this study. Cylinders (height × diameter, 6 × 4mm) were prepared from each material and stored in artificial saliva (7d at 37 °C). Cylinder height was measured at baseline and after 7 days. After storage, the compression modulus was measured to calculate the free hygroscopic expansion stress. For pH-neutralization and hydrophilicity assessment, disks (height × diameter, 1 × 1.5 mm) were prepared, covered with electrolyte, and monitored over 24 h at 37 °C. Hydrophilicity was assessed using the static sessile drop technique at baseline and at different time intervals up to 24 h. Data were analyzed using one-way ANOVA and post hoc Student-Newman-Keuls test (S-N-K, α = 0.05).
After 24 h, RX2 (pH24h 4.68) had a significantly higher (p < 0.05) pH-value than MCE (pH24h 4.2) and iCEM (pH24h 3.23). iCEM showed the significantly highest hydrophilicity (p < 0.05) after 24 h (θ24h 85.02°), while MCE resulted lower (θ24h 113.01°) in comparison with RX2 (θ24h 108.11°). The resulting hygroscopic expansion stress of iCEM (29.15 MPa) was significantly higher (p < 0.05) compared to RX2 (14.5 MPa) and MCE (21.02 MPa).
The material with lowest pH-neutralization capacity displayed higher hydrophilicity after 24 h and higher hygroscopic expansion stress after 7 days compared to those with high pH-neutralization.
Remnant hydrophilicity due to low pH-neutralization of SARCs could lead to cement interface stress build-up and long-term failure of silicate ceramic restorations.
KeywordsSelf-adhesive resin cements pH Hydrophilicity Hygroscopicity Expansion stress
The present work was performed by Ms. Lena Rödel in fulfillment of the requirements for obtaining the degree “Dr. med. dent..”
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
The work was supported by Dental Clinic 1—Operative Dentistry and Periodontology of the Friedrich-Alexander University Erlangen-Nürnberg.
This article does not contain any studies with human participants or animals performed by any of the authors.
For this type of study, formal consent is not required.
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