Four chemical methods of porcelain conditioning and their influence over bond strength and surface integrity.
OBJECTIVE
To assess four different chemical surface conditioning methods for ceramic material before bracket bonding, and their impact on shear bond strength and surface integrity at debonding.


METHODS
Four experimental groups (n = 13) were set up according to the ceramic conditioning method: G1 = 37% phosphoric acid etching followed by silane application; G2 = 37% liquid phosphoric acid etching, no rinsing, followed by silane application; G3 = 10% hydrofluoric acid etching alone; and G4 = 10% hydrofluoric acid etching followed by silane application. After surface conditioning, metal brackets were bonded to porcelain by means of the Transbond XP system (3M Unitek). Samples were submitted to shear bond strength tests in a universal testing machine and the surfaces were later assessed with a microscope under 8 X magnification. ANOVA/Tukey tests were performed to establish the difference between groups (α= 5%).


RESULTS
The highest shear bond strength values were found in groups G3 and G4 (22.01 ± 2.15 MPa and 22.83 ± 3.32 Mpa, respectively), followed by G1 (16.42 ± 3.61 MPa) and G2 (9.29 ± 1.95 MPa). As regards surface evaluation after bracket debonding, the use of liquid phosphoric acid followed by silane application (G2) produced the least damage to porcelain. When hydrofluoric acid and silane were applied, the risk of ceramic fracture increased.


CONCLUSIONS
Acceptable levels of bond strength for clinical use were reached by all methods tested; however, liquid phosphoric acid etching followed by silane application (G2) resulted in the least damage to the ceramic surface.
Centro de Estudos Odontológicos Meridional, Passo Fundo, Rio Grande do Sul, BR.
João Paulo Fragomeni
JP
Stella
Centro de Estudos Odontológicos Meridional, Passo Fundo, Rio Grande do Sul, BR.
Andrea Becker
AB
Oliveira
Department of Pediatric Dentistry and Orthodontics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, BR.
Lincoln Issamu
LI
Nojima
Department of Pediatric Dentistry and Orthodontics, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, BR.
Mariana
M
Marquezan
D000134:Acid Etching, Dental / Q000379:methods*; D000538:Aluminum Silicates / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry; D003722:Dental Alloys / Q000737:chemistry; D001840:Dental Bonding; D017005:Dental Debonding / Q000379:methods; D003776:Dental Porcelain / Q000737:chemistry*; D003799:Dental Stress Analysis / Q000295:instrumentation; D006858:Hydrofluoric Acid / Q000737:chemistry; D008422:Materials Testing; D008853:Microscopy; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D010756:Phosphoric Acids / Q000737:chemistry; D017680:Potassium Compounds / Q000737:chemistry; D019279:Resin Cements / Q000737:chemistry; D033081:Shear Strength; D012821:Silanes / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties
D000538:Aluminum Silicates; D003188:Composite Resins; D003722:Dental Alloys; D010756:Phosphoric Acids; D017680:Potassium Compounds; D019279:Resin Cements; D012821:Silanes; C516047:Transbond XT Light Cure Adhesive Primer; D003776:Dental Porcelain; C016447:feldspar; C030242:phosphoric acid; D006858:Hydrofluoric Acid