Functional Monomers With Different Carbon Chains on Self-etching Enamel Bonding

Objectives: This study evaluated functional monomers with different space length and hydrophilicity on carbon chains on self-etching enamel bonding.
Methods: 15% primers solutions for 2-step self-etching adhesives were prepared using 10-methacryloyloxy-decyl-dihydrogen phosphate (MDP), methacryloyloxy-tetraethylene-glycol-dihydrogen phosphate (MTEP) and methacryloyloxy-caprolactone-dihydrogen phosphate (CAP-P), the commercial systems were used as control Clearfil SE (CSE) and AdheSE (ADS). Thirty human molars had flated the enamel surfaces and were sectioned in 4 parts (buccal, lingual, proximals) and divided into 5 groups, according the experimental groups (MDP, CAP-P, MTEP, CSE and ADS) (n=24, 12 specimes to microshear bond strength, 8 specimens to etching pattern [4 for scanning electronic microscopy-SEM and 4 to confocal laser scanning microscopy-CLSM] and 4 specimens to contact angle). For each group, the specimens were bonded (primer 20 s and one bond coat), for the experimental primers, Adper Scotchbond adhesive was used. Twelve specimens for each group were mounted in PVC rings and filled with acrylic resin and microshear testing preparation, after tested by microshear bond strength (1 mm/min). Four specimens after the bonding procedure, were rinsed with acetone and ethanol solutions (100%) and evaluated by SEM and other 4 specimens were evaluated by CLSM, for etching pattern evaluation. Other 4 specimens were submitted to contact angle for wettability evaluation. Data were statistically analyzed (ANOVA, Tukey’s test alpha = 0.05).
Results: The MDP exhibited the highest microshear bond strength results (26.8±4.1) followed for CAP-P (20.0±2.8), the CSE group exhibited intermediate values (15.5±3.6), while the MTEP (10.3±2.8) and ADS (11.5±1.05) exhibited the lowest results, (p<0.05). While the MDP, CAP-P and CSE exhibited the lowest contact angle (p<0.05) and higher etching pattern comparing to MTEP and ADS groups.
Conclusions: Functional monomers with longer and more hydrophobic carbon chains increase the interaction and the wettability on enamel substrate consequently, improve the enamel bond strength on self-etching strategy.