Effect of smear layer thickness and acidity of self-etching solutions on early and long-term bond strength to dentin.
OBJECTIVE
To evaluate the effect of smear layer thickness (SL) on early and 6-month bond strength (BS) of self-etching adhesives to dentin and to measure the ultimate microtensile strength (UTS) of the adhesives.


METHODS
Clearfil SE Bond; Optibond Solo Plus Self-Etch Primer; Tyrian Self Priming Etchant (TY) and as controls, Single Bond (SB) and Scotchbond Multi-Purpose Plus (SBMP) were applied on flat superficial dentin surface with thick and thin SL thicknesses. After adhesive's application (n=6) a resin build-up was made. After 24h, resin-dentin beams (0.8mm(2)) were prepared to be tested immediately and after 6-month (6M) at 0.5mm/min. For the UTS measurement, hour-glass specimens were prepared with the bonding resin alone or after mixing (1:1). BS values were analyzed by three-way repeated measures ANOVA and Tukey's multiple comparison tests. Two-way ANOVA (bonding resin and bonding resin+self-etching primer) and Tukey's test were used for the UTS values. The bonding resins were re-evaluated separately by a one-way ANOVA and Tukey's test, since Single Bond is a one-bottle adhesive (alpha=0.05).


RESULTS
The SL thickness was not significant (p=0.64). BS values were reduced after 6M, except for the SBMP. TY provided the lowest BS mean while SB and SBMP the highest BS. The UTS of the SBMP was the highest. TY yielded the lowest UTS. Regression analysis revealed a linear and significant relationship between the UTS of self-etch systems and the mean BS (R=0.95, p=0.02).


CONCLUSIONS
The performance of a self-etching system does not seem to be dependent on the SL thickness. The total-etch, three-step system provided the highest BS to dentin and maintained the BS stable over 6 months. The performance of the self-etching systems can be envisaged by their UTS.
Reis
Alessandra
A
Department of Dental Materials and Operative Dentistry, Universidade do Oeste de Santa Catarina, Campus Joaçaba, R. Getúlio Vargas, 2125, Bairro Flor da Serra, CEP: 89600-000 Joaçaba/SC, Brazil. reis_ale@hotmail.com
Grandi
Viviane
V
Carlotto
Larissa
L
Bortoli
Giana
G
Patzlaff
Rafael
R
Rodrigues Accorinte
Maria de Lourdes
Mde L
Dourado Loguercio
Alessandro
A
D000134:Acid Etching, Dental / Q000379:methods*; D000704:Analysis of Variance; D001840:Dental Bonding; D003799:Dental Stress Analysis; D003804:Dentin; D017220:Dentin-Bonding Agents; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008422:Materials Testing; D008689:Methacrylates; D008963:Molar; D019279:Resin Cements; D016369:Smear Layer; D018709:Statistics, Nonparametric; D013718:Tensile Strength
C438313:Clearfil SE Bond; D017220:Dentin-Bonding Agents; D008689:Methacrylates; C451600:OptiBond Solo Plus; C500960:OptiBond Solo Plus Self-Etch; D019279:Resin Cements; C481138:Tyrian SPE