Effect of self-etching adhesives on dentin permeability in a fluid flow model

STATEMENT OF PROBLEM: Numerous self-etching bonding systems exist, with composition differing from one product to another. It is important for the clinician to know if they are all equally effective, and whether they provide an effective seal between dentin and restorative materials. PURPOSE: This study was designed to measure the hydraulic conductance of physiologic saline across dentin after application of various self-etching bonding systems or of a 1-bottle adhesive system preceded by a phosphoric acid etch. MATERIAL AND METHODS: One hundred extracted noncarious human third molars from patients 18-25 years old were used for this study. Dentin disks were cut from crown segments parallel to the occlusal surface at the top of the pulp cavity. The 100 disks, each 1 mm thick, were divided into 10 groups (n=10 per group), each of which was treated with 1 of 9 self-etching systems-AdheSE, Adper Prompt L-Pop, Clearfil SE Bond, Etch & Prime 3.0, Prime & Bond NRC Nt, One-Up Bond F, optiBond solo Plus Self Etch, Prompt L-Pop, or Xeno III-or a control bonding system (Prime & Bond NT) preceded by a phosphoric acid etch. Hydraulic conductance, the volume of fluid transported across a known area of surface (0.28 cm2) per unit time under a unit pressure gradient (200 cm H2O), was analyzed for the adhesive systems using a fluid flow apparatus (Flodec). First, both sides of each specimen were etched with 36% phosphoric acid for 30 seconds, and the hydraulic conductance was measured every 30 seconds for 15 minutes. The initial set of measurements served as the reference value for each specimen. The measurements were repeated when a smear layer had been formed and, finally, after 1 of the 10 bonding systems had been applied. The data were analyzed using a 1-way ANOVA and Duncan's multiple range test (alpha=.05). RESULTS: The control 1-bottle adhesive used with a phosphoric acid pre-etch did not provide the largest reduction in penetration (42.3%). The greatest mean reduction (68.9%, P<.05) was observed with the self-etching product Xeno III. The mean reduction for the other materials tested were: One-Up Bond F, 60.5%; AdheSE, 58.2%; Etch & Prime 3.0, 56.8%; Adper Prompt L-Pop, 51%; optiBond solo Plus Self Etch, 45%; Clearfil SE Bond, 35.5%, Prime & Bond NRC Nt, 16.4%; and Prompt L-Pop, 16.3%. CONCLUSION: Within the limitations of this study, the self-etching systems tested produced different reductions in dentin permeability. For some, the reduction was much greater than the decrease in dentin permeability provided by the bonding system with a phosphoric acid pre-etch; for others, the reduction was small.