Study of Proanthocyanidin-Primers on Tissue Water, Resin, and Dentin Bonding

Objectives: Proanthocyanidins are flavonoids explored as multi-functional biomaterials for dental therapies. This study compared the effects of ligand-Proanthocyanidins (PAC) primers on the hydric state of the dentin matrix, the degree of conversion (DC) of model adhesive, and dentin-resin micro tensile-bond strength (TBS).
Methods: Four PAC-primers [A-type trimers (DESIGNER-AA), AB-type trimers (DESIGNER-AB), A-type tetramers (DESIGNER-AAA), and AB-Type tetramers (DESIGNER-ABA)] were produced using a DESIGNER approach and chemical conversion procedures. Dentin matrix water distribution was determined using 1 wt. % PAC-primers treatment on demineralized dentin (1x3x1.5mm, n= 6). Thermograms obtained through a 3-phase cooling/heating cycle determined the fractions of freezable (unbound) and un-freezable (tightly bound) water using differential scanning calorimetry (DSC). The effects of 2.5 wt. % PAC addition on the DC of a model adhesive (BisGMA/TEGDMA/HEMA with 40wt% etOH, n=6) was determined using a FTIR-ATR method. The dentin-resin TBS was studied on polished dentin surfaces (n=8) and etch-and-rinse bonding procedures (surface etching, 10% PAC priming for 1 min, rinsing, adhesive application, and resin composite build-up). After 24 hs, specimens were sectioned, and TBS measured using a universal testing machine. Data were statistically analyzed using one-way ANOVA, Games-Howell post hoc tests, α= 0.05.
Results: Dentin matrix presented 9.4% bound and 46.1% unbound water. Treatment with PAC-DESIGNER primers did not significantly affect the distribution of bound and unbound water (p > 0.05). FTIR analysis revealed no significant differences in DC between control and PAC containing adhesives (p > 0.05). PAC primers significantly increase the TBS (means 45-55 MPa) when compared to control (19 MPa, p < 0.05), with no statistically significant differences among PAC primers (p > 0.05).
Conclusions: PAC-primers did not affect the hydric state of dentin matrix and did not interfere with degree of conversion of model adhesive. PAC DESIGNERs yield high dentin-resin TBS, with no apparent difference among the formulations.