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Bonding agent was developed to simplify the adhesion process and to eliminate the potential for postoperative sensitivity.
The quest for agents that would bond to tooth structure began nearly 50 years ago; unfortunately, it was not until much later that successful formulations were introduced to the dental profession.
Over time, each new generation of dentinal adhesives was marketed with the purpose of simplifying the application procedures. The first clinically successful bonding agent was characterized by numerous placement steps, including the application of an acid-etching agent and multiple applications of several layers of the primer. This was followed by placement of the adhesive. In addition to simplifying the application technique, the sixth- and seventh-generation bonding agents were designed to eliminate or dramatically reduce the likelihood of postoperative sensitivity. The success was so dramatic that a good share of the clinicians converted to the sixth generation.
However, one of the problems associated with the seventh-generation products is a reduced adherence to the enamel portions of the preparation. This has mandated that the operator must take special precautions. Pre-etching with phosphoric acid or surfacing with the bonding agent to the enamel for 30 seconds is commonly recommended. Failure to do so may result in thick brown lines at the composite-enamel interface. This, of course, suggests that microleakage is occurring between the resin and the enamel surface.
BeautiBond® (Figure 1) was developed to simplify the adhesion process and eliminate the potential for postoperative sensitivity. The mechanism associated with the elimination of postoperative sensitivity is related to the method of etching the dentinal surface and the deposition of the bonding agent. Because impregnation of the bonding agent occurs nearly simultaneously with the etching procedure, the odontoblastic processes are thereby sealed. This, in turn, prevents any fluid movement over the surfaces of the processes located within the dentin, providing freedom from pain and sensitivity (Figure 2).
The simple procedure for application of BeautiBond is application of the bonding agent for a 10-second period; air-dry for approximately 3 seconds with increasing air pressure/force; and photo-cure for 10 seconds (Figure 3 and Figure 4).
In addition to the uniquely straightforward and simple directions of bonding the restoration, BeautiBond is characterized by a number of excellent properties. One of these includes the film thickness, which is only 5 µm. This ensures a better adaptation of the composite resin restoration to the walls of the cavity preparation. Another is the uniqueness of the bonding agent. In essence, it contains two functional adhesive monomers. The first includes a phosphoric acid and the second contains carboxylic acid. The first is designed to adhere to enamel and the second is designed to adhere to dentin. Under such a condition, this dual-phased dentinal adhesive relates specifically to dentin as well as to enamel. This approach eliminates the potential for under-etching the enamel and elimination of the development of thick brown lines at the enamel-restoration interface. Another interesting characteristic of BeautiBond is that it is HEMA-free, which eliminates the possibility of gingival blanching and irritation and potentially reduced longevity of the bond.
The shear bond strength of BeautiBond to enamel and to dentin is similar to that of multiple-step bonding agents. When subjected to thermal cycling, the shear bond strengths remain constant regardless of the number of thermal cycles. Shear bond strengths to enamel and to dentin are 17 MPa and 18 MPa, respectively. The effective adhesion to enamel is attained without any pre-etching of the enamel or extended application of the bonding agent to the enamel surface.
Scanning electron microscopic studies have demonstrated excellent adaptation of the bonding agent to the surface of dentin as well as to enamel. Transmission electron microscopy has demonstrated the same excellent adaptation to dentin. Highly magnified images using transmission electron microscopy showed that collagen fibers within the dentin were tightly bonded to the dentinal adhesive.
The development of BeautiBond dentinal adhesive is a major advancement in dentin bonding agents. This new and innovative material not only is appreciably faster than most seventh-generation adhesive systems but it is simpler to use. The entire bonding procedure, including curing time, takes less than 30 seconds. SEM not only reveals excellent bonding and adaptation to the dentinal structures but also to the overlying composite resin system. Equal bond strength for dentin and enamel are made possible by the inclusion of separate monomers for the two different structures. Finally, worldwide clinical trials have demonstrated both efficacy and lack of patient sensitivity in Class I through V restorations.
This article was written by Karl Leinfelder, DDS.
For more information, contact:
Shofu Dental Corporation
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