Objectives This work measured the amount of bound versus unbound water in completely-demineralized dentin. Methods Dentin beams prepared from extracted human teeth were completely demineralized, rinsed and dried to constant mass. They were rehydrated in 41% relative humidity (RH), while gravimetrically measuring their mass increase until the first plateau was reached at 0.064 (vacuum) or 0.116 g H2O/g dry mass (Drierite). The specimens were then exposed to 60% RH until attaining the second plateau at 0.220 (vacuum) or 0.191 g H2O/g dry mass (Drierite), and subsequently exposed to 99% RH until attaining the third plateau at 0.493 (vacuum) or 0.401 g H2O/g dry mass (Drierite). Results Exposure of the first layer of bound water to 0% RH for 5 min produced a −0.3% loss of bound water; in the second layer of bound water it caused a −3.3% loss of bound water; in the third layer it caused a −6% loss of bound water. Immersion in 100% ethanol or acetone for 5 min produced a 2.8 and 1.9% loss of bound water from the first layer, respectively; it caused a −4 and −7% loss of bound water in the second layer, respectively; and a −17 and −23% loss of bound water in the third layer.. Bound water represented 21–25% of total dentin water. Chemical dehydration of water-saturated dentin with ethanol/acetone for 1 min only removed between 25 to 35% of unbound water, respectively. Significance Attempts to remove bound water by evaporation were not very successful. Chemical dehydration with 100% acetone was more successful than 100% ethanol especially the third layer of bound water. Since unbound water represents between 75–79% of total matrix water, the more such water can be removed, the more resin can be infiltrated.

Objective To determine if acid-etched, cross-linked dentin can be dehydrated without lowering bond strength below that of cross-linked wet-bonded dentin in vitro. Methods Using extracted human third molars, control acid-etched dentin was bonded with Single Bond Plus, using either the wet- or dry-bonding technique. Experimental acid-etched dentin was treated with 5 mass% grape seed extract (GSE) in different solvents for 1 min before undergoing wet vs. dry resin-dentin bonding with Single Bond Plus. Completely demineralized dentin beams were treated with 5% GSE for 0, 1 or 10 min, before measuring stiffness by 3-point flexure. Other completely demineralized beams were treated similarly and then incubated in buffer for 1 week to measure the collagen solubilization by endogenous dentin proteases. Results 24 hr microtensile bond strengths (μTBS) in wet and dry controls were 53.5 ± 3.6 and 9.4 ± 1.8 MPa, respectively (p < 0.05). 5% GSE in water gave μTBS of 53.7 ± 3.4 and 39.1 ± 9.7 MPa (p < 0.05), respectively, while 5% GSE in ethanol gave μTBS of 51.2 ± 2.3 and 35.3 ± 2.0 MPa (p < 0.05). 5% GSE in 5% EtOH/95% water gave wet and dry μTBS of 53.0 ± 2.3 and 55.7 ± 5.1 MPa (p > 0.05). Cross-linking demineralized dentin with 5% GSE increased stiffness of dentin and decreased collagen degradation (p<0.05). Significance 5% GSE pretreatment of acid-etched dentin for 1 min permits the dentin to be completely air-dried without lowering bond strength.

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Many reports have indicated that resin bond strengths to noncarious sclerotic cervical dentin are lower than bonds made to normal dentin. This is thought to be due to tubule occlusion by acid-resistant mineral salts, preventing resin tag formation following acid etching. The purpose of this review was to critically examine what is known about the structure of this type of dentin. Recent transmission electron microscopy revealed that in addition to occlusion of the tubules by mineral crystals, many parts of wedge-shaped cervical lesions contain a hypermineralized surface that resists the etching action of both self-etching primers and phosphoric acid. This layer prevents hybridization of the underlying sclerotic dentin. In addition, bacteria are often detected on top of the hypermineralized layer. Sometimes the bacteria were embedded in a partially mineralized matrix. Acidic conditioners and resins penetrate variable distances into these multilayered structures. Examination of both sides of the failed bonds revealed a wide variation in fracture patterns that involved all of these structures. Microtensile bond strengths to the occlusal, gingival, and deepest portions of these wedge-shaped lesions are signifi cantly lower than similar areas artifi cially prepared in normal teeth. When resin bonds to sclerotic dentin are extended to include peripheral sound dentin, their bond strengths are probably high enough to permit retention of class V restorations by adhesion, without additional retention.