Effect of surface conditioning methods on the microtensile bond strength of resin composite to composite after aging conditions.
OBJECTIVE
This study evaluated the effect of two different surface conditioning methods on the repair bond strength of a bis-GMA-adduct/bis-EMA/TEGDMA based resin composite after three aging conditions.


METHODS
Thirty-six composite resin blocks (Esthet X, Dentsply) were prepared (5 mm x 6 mm x 6 mm) and randomly assigned into three groups for aging process: (a) immersion in citric acid (pH 3.0 at 37 degrees C, 1 week) (CA); (b) boiling in water for 8h (BW) and (c) thermocycling (x5000, 5-55 degrees C, dwell time: 30s) (TC). After aging, the blocks were assigned to one of the following surface conditioning methods: (1) silica coating (30 microm SiO(x)) (CoJet, 3M ESPE)+silane (ESPE-Sil) (CJ), (2) phosphoric acid+adhesive resin (Single Bond, 3M ESPE) (PA). Resin composite (Esthet.X) was bonded to the conditioned substrates incrementally and light polymerized. The experimental groups formed were as follows: Gr1:CA+PA; Gr2:CA+CJ; Gr3:BW+PA; Gr4: BW+CJ; Gr5:TC+PA; Gr6: TC+CJ. The specimens were sectioned in two axes (x and y) with a diamond disc under coolant irrigation in order to obtain non-trimmed bar specimens (sticks, 10 mm x 1 mm x 1 mm) with 1 mm(2) of bonding area. The microtensile test was accomplished in a universal testing machine (crosshead speed: 0.5 mm min(-1)).


RESULTS
The means and standard deviations of bond strength (MPa+/-S.D.) per group were as follows: Gr1: 25.5+/-10.3; Gr2: 46.3+/-10.1; Gr3: 21.7+/-7.1; Gr4: 52.3+/-15.1; Gr5: 16.1+/-5.1; Gr6, 49.6+/-13.5. The silica coated groups showed significantly higher mean bond values after all three aging conditions (p<0.0001) (two-way ANOVA and Tukey tests, alpha=0.05). The interaction effect revealed significant influence of TC aging on both silica coated and acid etched groups compared to the other aging methods (p<0.032). Citric acid was the least aggressive aging medium.


CONCLUSIONS
Chairside silica coating and silanization provided higher resin-resin bond strength values compared to acid etching with phosphoric acid followed by adhesive resin applications. Thermocycling the composite substrates resulted in the lowest repair bond strength compared to citric acid challenge or boiling in water.
Ozcan
Mutlu
M
University Medical Center Groningen, University of Groningen, Department of Dentistry and Dental Hygiene, Clinical Dental Biomaterials, Antonius Deusinglaan 1, 9713 AV Groningen, The Netherlands. mutluozcan@hotmail.com
Barbosa
Silvia Helena
SH
Melo
Renata Marques
RM
Galhano
Graziela Avila Prado
GA
Bottino
Marco Antonio
MA
D000180:Acrylic Resins / Q000737:chemistry*; D003188:Composite Resins / Q000737:chemistry*; D001840:Dental Bonding / Q000379:methods*; D006358:Hot Temperature; D011140:Polyurethanes / Q000737:chemistry*; D012821:Silanes; D012822:Silicon Dioxide; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors
D000180:Acrylic Resins; C029012:Composite Dental Resin; D003188:Composite Resins; D011140:Polyurethanes; D012821:Silanes; D012822:Silicon Dioxide