Biochemical modification to the dentin collagen improves bond strength

Type I collagen is a major component of the hybrid layer, and improvement of its mechanical properties may be advantageous during bonding procedures.  Objectives: To investigate the effect of three different cross-linking agents (Glutaraldehyde [GD], Grape seed extract [GSE], and Genipin [GE]) on the dentin tensile bond strength (TBS). Methods: 64 sound human molars had their occlusal surfaces ground flat to expose dentin. Dentin surfaces were etched using a phosphoric acid gel, rinsed, and the teeth were randomly divided according to the dentin treatment: Control group, 5% GD, 6.5% GSE and 0.5% GE.  Teeth were kept in their specific solutions for 1 hour and later restored either with One Step Plus (Bisco) or Adper Single Bond (3M ESPE) adhesive systems. Composite resin was used to build-up a crown incrementally. After 24 hours, teeth were sectioned into 0.7±0.2 mm thick slabs and then trimmed at the interface to produce a cross-sectional surface area of 1.0 mm². Samples were tested in tensile (EZ Graph) at a crosshead speed of 1mm/min. Data were statistically analyzed using ANOVA and Fisher's PLSD tests (p< 0.05).  Results: TBS values [MPa (SD)] are:

Adhesive systems	Treatment
	Control	GD	GSE	GE	Pooled data
SB	33.38 (6.79)	68.96 (3.91)	71.06 (14.59)	43.70 (8.23)	54.27a (8.38)
OS	44.13 (8.23)	65.46 (8.06)	74.40 (10.08)	34.80 (4.09)	54.70a (7.61)
Pooled data	38.75C (7.51)	67.21B (5.98)	72.73A (12.33)	39.25C (6.16)
Different letters indicate statistically significant differences.

There was a significant interaction between treatments vs. adhesive system (p< 0.001). Treatments affected TBS (p< 0.0001) while no differences were observed between the adhesive systems (p = 0.6961). Conclusions: The use of GSE and GD increased the TBS, regardless of the adhesive system. This in vitro study demonstrates that modification to the dentin matrix improves the bonded interfaces properties. Supported by NIH-NIDCR# DE017740.