The Effects of Acetone, Ethanol, HEMA, and Air on the Stiffness of Human Decalcified Dentin Matrix

Abstract

During resin-bonding procedures, dentin surfaces are treated with acidic conditioners to remove the smear layer and decalcify the surface to expose the collagen fibrils of the underlying matrix. These decalcified surfaces are then either air-dried or treated with dehydrating solvents, procedures which may modify the physical properties of the dentin matrix. The purpose of this study was to evaluate the effects of dehydration on the stiffness of the decalcified dentin matrix. Small (8 x 1.7 x 0.9 mm) beams of dentin were prepared from mid-coronal dentin of extracted human molars. The ends were covered with varnish for protection, and the specimens were placed in 0.5 M EDTA for 5 days to decalcify. The stiffness was measured by both the cantilever technique and by conventional stress-strain testing. Specimens tested by the cantilever technique were sequentially exposed to water, acetone, alcohol, HEMA, and glutaraldehyde. Specimens tested by conventional stress-strain testing were exposed either to water, acetone, or HEMA, or were allowed to air-dry. The results indicate that the stiffness of decalcified human dentin matrix is very low (ca. 7 MPa), if the specimens are wet with water. As they are dehydrated, either chemically in water-miscible organic solvents or physically in air, the stiffness increases 20- to 38-fold at low strains or three- to six-fold at high strains. These increases in modulus were rapidly reversed by rehydration in water. Exposure to glutaraldehyde also produced an increase in stiffness that was not reversible when the specimens were placed back in water.

Effect of Adhesives and Thermocycling on the Shear Bond Strength of a Nano-Composite to Coronal and Root Dentin

“…[11][12] Slow water absorption by bonded constituents can lead to the degradation of bond strengths, because of hydrolysis of the adhesive resin [13][14] and possibly the plasticizing effects of water on resin and collagen. 12 Thermocycling is the in vitro process of subjecting a restoration and tooth to temperature limits similar to those experienced in the oral cavity, which can produce potential negative effects due to dissimilar coefficients of thermal expansion between the tooth and the restorative material. 15 Thermocyling stresses the bond between resin and the tooth, and it may affect bond strength, depending on the adhesive system.…”

Impact of Adhesive Application and Moisture on the Mechanical Properties of the Adhesive Interface Determined by the Nano-indentation Technique

“…The collagen fibrils form weak interpeptide bonds that render the matrix shrunk, stiff [19][20] and practically impermeable to resin adhesives, reducing the infiltration rate of the bonding resin within the hybrid layer to approximately 50% when applied to dry instead of wet dentin. [3][4]21 Previous studies have reported that the adverse effect of over-drying could be reversed by vigorously rubbing the adhesive on the dentin substrate.…”

A New Level of Knowledge in the Field of Adhesive Systems – A Real Success in Practical Dentistry

“…Этанол, как и вода, полярный протонный растворитель, но из-за своей низкой диэлектрической константы он более подходит к менее полярным растворенным веществам [4,23,24]. Этанол образует водородные связи с водой и улучшает ее испарение с поверхности зуба, именно поэтому спирт и вода используются как ко-растворители.…”

“…Этанол образует водородные связи с водой и улучшает ее испарение с поверхности зуба, именно поэтому спирт и вода используются как ко-растворители. Maciel et al обнаружили, что этанол также укрепляет волокна коллагена, тем самым уменьшая их коллапсирование при испарении растворителя [23][24][25]. Ацетон -растворитель с высоким дипольным моментом и низкой диэлектрической константой [4,23,25].…”

“…Он хорошо подходит как растворитель к адгезивам с комбинацией гидрофобных и гидрофильных компонентов. Ацетон испаряется в четыре раза легче, чем этанол, это улучшает полимеризацию адгезива, но может уменьшать срок годности материала [22,24]. За счет меньшего образования водородных связей ацетон расправляет коллапсированные волокна коллагена хуже, чем вода или спирт [23].…”