Self-adhesive resin cements: pH-neutralization, hydrophilicity, and hygroscopic expansion stress.
OBJECTIVE
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.


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).


RESULTS
After 24 h, RX2 (pH24h4.68) had a significantly higher (p < 0.05) pH-value than MCE (pH24h4.2) and iCEM (pH24h3.23). iCEM showed the significantly highest hydrophilicity (p < 0.05) after 24 h (θ24h85.02°), while MCE resulted lower (θ24h113.01°) in comparison with RX2 (θ24h108.11°). 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).


CONCLUSIONS
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.


CONCLUSIONS
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.
Dental Clinic 1-Operative Dentistry and Periodontology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Glückstr. 11, 91054, Erlangen, Germany.
Lena
L
Roedel
Dental Clinic 1-Operative Dentistry and Periodontology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Glückstr. 11, 91054, Erlangen, Germany.
Vera
V
Bednarzig
Dental Clinic 1-Operative Dentistry and Periodontology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Glückstr. 11, 91054, Erlangen, Germany.
Renan
R
Belli
Dental Clinic 1-Operative Dentistry and Periodontology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Glückstr. 11, 91054, Erlangen, Germany.
Anselm
A
Petschelt
Dental Clinic 1-Operative Dentistry and Periodontology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Glückstr. 11, 91054, Erlangen, Germany.
Ulrich
U
Lohbauer
Dental Clinic 1-Operative Dentistry and Periodontology, Friedrich-Alexander University Erlangen-Nürnberg, Erlangen, Glückstr. 11, 91054, Erlangen, Germany. zorzin@dent.uni-erlangen.de.
José
http://orcid.org/0000-0003-3850-6165
J
Zorzin
D003738:Dental Cements / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008422:Materials Testing; D019279:Resin Cements / Q000737:chemistry*; D012464:Saliva, Artificial; D017155:Wettability
D003738:Dental Cements; C515955:Maxcem; C483701:Rely X Unicem; D019279:Resin Cements; D012464:Saliva, Artificial
Expansion stress; Hydrophilicity; Hygroscopicity; Self-adhesive resin cements; pH
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