Develop a reproducible method of assessing composite sealing / bonding of a dentine cavity. Use the method to compare effectiveness of etchant and bonding agent use. Compare benefits of adhesive monomer versus reactive filler addition to a composite on strength versus bonding capability.
Method:
Base monomer UDMA and diluent monomer TEGDMA in 3:1 mass ratio were mixed with 5 wt % HEMA, or 4-META. These were combined with silane treated glass particles. In the reactive filler composite, chlorhexidine diacetate (5 wt %), reactive mono and tri calcium phosphate (10 wt %), and fibres (5 wt %) were included in the glass. Powder to liquid ratio was 4:1. Commercial materials tested included Z250, Gradia and Ecusphere.
The biaxial flexural strength of discs light cured both sides for 40s (10 mm diameter, 1 mm thick) were determined after 24 hours in distilled water. Bonding was determined using ivory dentine blocks. Cylindrical holes (3mm diameter, 5 mm deep) were drilled. These were filled by composite after acid etching with 37 % H3PO4 for 0 or 20 s and addition of ibond for 0 or 20 s.
Result:
Experimental composites with HEMA and 4-META had strengths comparable with Z250 and Ecusphere (170MPa), but much higher than Gradia (70MPa). Addition of reactive fillers decreased strength from 170 to 125MPa
With Z250, debonding force increased from 100 to 450 to 950 N with no treatment, acid treatment or acid and ibond respectively. Gradia and Ecusphere gave similar results. The HEMA composite had debonding values of 100, 800 and 1300 N respectively. 4META and reactive filler composites both had debonding forces of ~700 and 850 N with no treatment or acid treatment but no bonding agent.
Conclusion:
Composites have been produced with strength comparable to commercial materials and improved dentine bonding.