IADR Abstract Archives
Improving Universal Adhesive Performance through Hydrophobic-Monomer-Incorporation and Selective Dentin Etching
Objectives: To evaluate the effect of partial dentin demineralization using different etching agents on dentin morphology and on the flexural bond strength of a universal adhesive system associated with a second-step hydrophobic monomer incorporation.
Methods: Sound third molars were sectioned occluso-cervically into slabs and subsequently mesio-distally into mid-coronal dentin beams (0.8 mm2). The proximal surfaces were polished with 320 grit SiC and etched with ortho-phosphoric acid 35% (wt%) for 15s (OPA 15s) or 3s (OPA 3s), meta-phosphoric acid 20% for 10s (MPA 10s) or polyacrylic acid sodium salt 15% for 30s (PAAN 30s). Dentin-beams were prepared following the twin-bonded interface for 4-point flexural strength testing. A universal bonding agent (Scotchbond Universal, 3M ESPE) was applied for 20s, light cured for 10 sec, and restored with composite resin. Samples bonded in self-etch mode, without acid-etching, served as control. Hydrophobic groups consisted of an extra hydrophobic resin application (Adhesive, Scotchbond Multi-purpose, 3M ESPE). Specimens were tested after storage in 37°C water for 24h at a crosshead speed of 1mm/min. Etched dentin surfaces and fracture patterns were characterized by SEM. Bond strength data was analyzed by two-way ANOVA and Tukey test (α=0.05).
Results: MPA and PAAN presented lower demineralization compared to OPA. Etching protocol and hydrophobic-resin-application significantly affected dentin bond strengths (p<0.0001). OPA 3s, MPA 10s and PAAN 30s produced higher bond strengths compared to self-etch or OPA 15s groups. While the application of the hydrophobic resin had no impact on self-etch or OPA 15s groups, its association to OPA 3s and MPA 10s significantly increased bond strengths. Fracture patterns were predominately mixed.
Conclusions: Immediate dentin bonding performance of universal adhesives can be improved by etching agents with low demineralization capacity. Associating universal adhesives to a second-step hydrophobic resin application can further enhance immediate dentin bonding depending on the etching agent used.
Methods: Sound third molars were sectioned occluso-cervically into slabs and subsequently mesio-distally into mid-coronal dentin beams (0.8 mm2). The proximal surfaces were polished with 320 grit SiC and etched with ortho-phosphoric acid 35% (wt%) for 15s (OPA 15s) or 3s (OPA 3s), meta-phosphoric acid 20% for 10s (MPA 10s) or polyacrylic acid sodium salt 15% for 30s (PAAN 30s). Dentin-beams were prepared following the twin-bonded interface for 4-point flexural strength testing. A universal bonding agent (Scotchbond Universal, 3M ESPE) was applied for 20s, light cured for 10 sec, and restored with composite resin. Samples bonded in self-etch mode, without acid-etching, served as control. Hydrophobic groups consisted of an extra hydrophobic resin application (Adhesive, Scotchbond Multi-purpose, 3M ESPE). Specimens were tested after storage in 37°C water for 24h at a crosshead speed of 1mm/min. Etched dentin surfaces and fracture patterns were characterized by SEM. Bond strength data was analyzed by two-way ANOVA and Tukey test (α=0.05).
Results: MPA and PAAN presented lower demineralization compared to OPA. Etching protocol and hydrophobic-resin-application significantly affected dentin bond strengths (p<0.0001). OPA 3s, MPA 10s and PAAN 30s produced higher bond strengths compared to self-etch or OPA 15s groups. While the application of the hydrophobic resin had no impact on self-etch or OPA 15s groups, its association to OPA 3s and MPA 10s significantly increased bond strengths. Fracture patterns were predominately mixed.
Conclusions: Immediate dentin bonding performance of universal adhesives can be improved by etching agents with low demineralization capacity. Associating universal adhesives to a second-step hydrophobic resin application can further enhance immediate dentin bonding depending on the etching agent used.