Factors Affecting Resin Tag Formation in Novel Dental Composites

Objectives: To assess the effect of Powder:Liquid ratio (PLR), 4META (acidic monomer) and PPGDMA (diluent-monomer) addition on the ability of novel composites to penetrate and promote apatite precipitation within demineralised human dentine.
Methods: UDMA was mixed either with (PPGDMA and 4META) or PPGDMA or 4META and camphorquinone (1%). These were combined with glass particles containing Monocalcium Phosphate Monohydrates (8%) and Polylysine (5%) at PLR 5:1 or 3:1 to make 6 composite pastes. The commercial composite Z250 (3M ESPE) was used as a control. 2mm thick discs of coronal dentine were demineralised by immersion in formic acid (4M) for 48hours. Complete demineralisation was confirmed using SEM/EDX and Raman. Pastes were applied to blot dried demineralised collagen and light cured for 40s. The collagen was subsequently dissolved by immersion in Sodium-Hypochlorite for 48hours. Composite resin tag lengths and densities were determined using SEM and ImageJ software.
Results: With Z250 no tags were detected. With experimental materials only PLR had a significant effect on the average length and density of tags. These increased by 310% and 215% respectively upon lowering the PLR (see Table 1). At the tips of the resin tags apatite precipitation was observed.
Conclusions: Creating caries-like dentine allows us to predict the way composite reacts with natural carious tissues. The new proposed experimental composites have the potential to seal carious dentine and promote remineralisation which allow less invasive technique in treating caries.