To evaluate grape seed extract (GSE)-incorporated phosphoric acid solutions’ ability to simultaneously demineralize and stabilize dentin collagen.
Method:
Superficial dentin of seven non-carious human molars was exposed after crown removal. A uniform smear layer was created, and sections were made occlusal-apically, followed by one cut below the abraded dentin surface, resulting in slabs for SEM (1-mm-thick) and TEM (0.5-mm-thick) observations. Three GSE-containing and three glutaraldehyde (GA)-containing etchant solutions were prepared by mixing GSE-powder or 25% GA with 85% phosphoric acid, ethanol and deionized water (see table). Using these etchants, the abraded surfaces of dentin slabs were etched for 30s, rinsed for 15s, and subject to 1h of digestion with 0.1% collagenase solution. The digested slabs were rinsed, fixed, and subsequently the demineralized dentin layer was visualized by SEM and TEM.
Phosphoric acid |
EtOH |
Additive |
pH |
||
GSE-containing |
GSE20 |
20% |
20% |
2% GSE |
0.41 |
GSE10 |
10% |
0.85 |
|||
GSE5 |
5% |
1.14 |
|||
GA-containing |
GA20 |
20% |
2.5% GA |
0.44 |
|
GA10 |
10% |
0.86 |
|||
GA5 |
5% |
1.17 |
Result:
Thirty seconds of etching with GSE- and GA-containing phosphoric acid both resulted in a thin (3-5 µm) layer of demineralized dentin collagen characterized by intact banding pattern. However, after digestion, this layer completely disappeared in samples etched with GA-containing etchants. In contrast, demineralized collagen with intact banding structure remained evident for specimens etched with GSE-containing etchants after digestion. Among the GSE-containing etchants, etching with GSE20 rendered demineralized collagen at the demineralization front (close to un-demineralized dentin) susceptible to collagenase degradation while the rest of it inert. This phenomenon was not observed in GSE10- and GSE5-etched specimens, where demineralized dentin collagen was invariably inert to digestion.
Conclusion:
Phosphoric acid with GSE additive could etch and stabilize dentin collagen simultaneously. A low phosphoric acid concentration (< 20 wt%) is necessary to synchronize the penetration of acid etchant and GSE cross-linker.