Tannic acid increases dentin matrix stability against enzymatic degradation

Increased amount of collagen cross-links may affect the stability of the dentin matrix. Objectives: To evaluate the effect of Tannic Acid, a collagen cross-linker, on the ultimate tensile strength (UTS) of demineralized dentin following enzymatic degradation. 

Methods: Ten sound human molars were sectioned into 0.5 mm thick slabs that were further trimmed to 1.0 mm. Specimens were demineralized with 10% phosphoric acid for 6 hours and divided into 4 groups: Control - no treatment (C); 1% Tannic Acid (1%TA), 10% Tannic Acid (10%TA), 20% Tannic Acid (20%TA).  Specimens were kept in their respective solutions for 1 hour, thoroughly rinsed and divided according to the storage media: 24 hours in 0.2 M ammonium bicarbonate buffer (no treatment) or 24 hours in collagenase/0.2 M ammonium bicarbonate buffer. After elapsed time, specimens were mounted and subjected to tensile forces at a crosshead speed of 1mm/min.  Statistical analysis was performed using two-way ANOVA and Fisher's PLSD test (p<0.05).

Results: UTS values expressed in MPa [Mean( SD)] are as follow:

Enzyme Treatment	Dentin Treatment
	C	1%TA	10%TA	20%TA	Pooled date
Buffer (no treatment)	8.94 (4.03)	13.87 (4.26)	14.87 (4.87)	16.93 (5.79)	13.65a (4.73)
Collagenase	0 (0)	10.85 (4.36)	14.26 (4.65)	15.64 (3.61)	10.19b (3.15)
Pooled data	4.47C (2.01)	12.36B (4.31)	14.56AB (4.76)	16.28A (4.70)

A statistically significant interaction was observed between the factors (p = 0.0131). Dentin treatment (p < 0.0001) and enzyme treatment (p = 0.0007) significantly affected the UTS. Collagenase digestion did not affect the UTS of 10%TA and 20%TA, while decreased values and complete digestion was observed respectively for 1%TA and C.

Conclusions: The application of Tannic acid inhibits the effect of collagenase digestion on dentin matrix, particularly for 10%TA and 20%TA and consequently did not affect the UTS values when compared to a control group. Supported by NIH-NIDCR # DE017740.