Objective: The purpose of this study was to test the hypothesis that noncollagenous components (e.g. proteoglycans, phosphoproteins, and others) present in dentin matrix may contribute to dentin bonding.  In order to test this hypothesis, demineralized bovine dentin samples were treated with various enzymes to remove those components and subjected to bond strength test. Methods: Bovine incisors were ground with 600 grit SiC to expose dentin, etched with 32% phosphoric acid gel (Bisco) for 60 s, and thoroughly rinsed. The samples were then treated with chondroitinase ABC (C-ABC), endo-β-galactosidase (Endoβ), alkaline phosphatase (ALP) or TPCK-trypsin. Controls were prepared in the same manner and incubated in the respective digestion buffers without the enzymes. After the treatments, all specimens were thoroughly rinsed and they were kept moist, or dried and re-wet with distilled water, and then bonded with One Step (Bisco).  Results:

	Control wet	Digested wet	Control Rewet	Digested Rewet
C-ABC	43.8 ± 9.8a	39.6 ± 8.3	41.4 ± 9.9 a	30.6 ± 6.8
Endoβ	41.3±12.5 b	40.1 ± 10.2 b	43.7±10.9 b	40.19 ± 5.6 b
Trypsin	42.8 ± 9.2 c	35.5 ± 8.7 e	44.1 ± 7.9 c	32.41± 7.7 e
ALP	44.1 ± 11.9 d	42.0 ± 11.1 d	48.7 ± 10.5 d	39.9 ± 10.7

Same superscripts equal no statistical significant difference (p>0.5). Conclusions: The results indicate that chondroitin sulphate glycosaminoglycans and some of the noncollagenous proteins susceptible to trypsin play roles in maintaining collagen matrix which is essential for dentin bonding. Supported by NIH grant DE10489.