The effect of water immersion on the shear bond strength between chairside reline and denture base acrylic resins.
OBJECTIVE
The effect of water immersion on the shear bond strength (SBS) between 1 heat-polymerizing acrylic resin (Lucitone 550-L) and 4 autopolymerizing reline resins (Kooliner-K, New Truliner-N, Tokuso Rebase Fast-T, Ufi Gel Hard-U) was investigated. Specimens relined with resin L were also evaluated.


METHODS
One hundred sixty cylinders (20 x 20 mm) of L denture base resin were processed, and the reline resins were packed on the prepared bonding surfaces using a split-mold (3.5 x 5.0 mm). Shear tests (0.5 mm/min) were performed on the specimens (n = 8) after polymerization (control), and after immersion in water at 37 degrees C for 7, 90, and 180 days. All fractured surfaces were examined by scanning electron microscopy (SEM) to calculate the percentage of cohesive fracture (PCF). Shear data were analyzed with 2-way ANOVA and Tukey's test; Kruskall-Wallis test was used to analyze PCF data (alpha= 0.05).


RESULTS
After 90 days water immersion, an increase in the mean SBS was observed for U (11.13 to 16.53 MPa; p < 0.001) and T (9.08 to 13.24 MPa, p= 0.035), whereas resin L showed a decrease (21.74 MPa to 14.96 MPa; p < 0.001). The SBS of resins K (8.44 MPa) and N (7.98 MPa) remained unaffected. The mean PCF was lower than 32.6% for K, N, and T, and higher than 65.6% for U and L.


CONCLUSIONS
Long-term water immersion did not adversely affect the bond of materials K, N, T, and U and decreased the values of resin L. Materials L and U failed cohesively, and K, N, and T failed adhesively.
Azevedo
Andrea
A
Department of Dental Materials and Prosthodontics, Araquara Dental School, UNESP - São Paulo State University, Araraquara, São Paulo, Brazil.
Machado
Ana Lucia
AL
Giampaolo
Eunice Teresinha
ET
Pavarina
Ana Claudia
AC
Vergani
Carlos Eduardo
CE
D000180:Acrylic Resins / Q000737:chemistry*; D000268:Adhesiveness; D001840:Dental Bonding; D003819:Denture Bases; D003822:Denture Liners; D003823:Denture Rebasing; D006801:Humans; D007101:Immersion; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D011108:Polymers / Q000737:chemistry; D033081:Shear Strength; D012826:Silicone Elastomers / Q000737:chemistry; D013314:Stress, Mechanical; D013997:Time Factors; D014867:Water / Q000737:chemistry
D000180:Acrylic Resins; D008689:Methacrylates; D011108:Polymers; D012826:Silicone Elastomers; C503430:Tokuso Rebase Fast; C483158:Ufi gel; D014867:Water; C103363:kooliner; C071514:truliner; C040291:Lucitone