Abstract
In this study, a new pretreatment method which enhances the adhesion between dentin and restorations was examined. The new pretreatment method consisted of: (1) acid etching the dentin adherend surface: (2) removing an exposed dentin collagen with an organic substance dissolving agent; and (3) applying the adhesive directly on the irregularities made of exposed dentin apatite. As primary agents for treating the dentin adherend surface, three types of acid etching agents (40% phosphoric acid, 0.5 M EDTA and 10% citric acid) were used. As secondary agents, two types of organic substance dissolving agents, 10% sodium hypochlorite solution (NaOCl-Solution) and 10% sodium hypochlorite solution containing 8-18 wt% of alumina (NaOCl-Gel), were used. In addition, a commercial bonding agent and another bonding agent having an increased concentration reducing agent (sodium benzenesulfinate) were also used. After carrying out the primary treatment with the phosphoric acid solution and the secondary treatment with the NaOCl-Solution, Panavia EX was applied to dentin through a commercial bonding agent.
The tensile adhesive strength obtained was 11.0 MPa in the horizontal direction. Hypothesizing an extracoronal tooth, the adherend surface was the vertical side and the secondary treatment was carried out with the solution for the same length of time (60 seconds). The resultant adhesive strength was only 3.6 MPa in the vertical direction. When the NaOCl-Gel containing 14 wt% of bodying agent was used for 60 seconds in the secondary treatment process, the initial tensile adhesive strength was 10.6 MPa. SEM observation and FT-IR analysis revealed that the NaOCl-Gel could hold well to the vertical adherend surface and efficiently dissolve an exposed collagen layer. There was a close relationship between the dissolution and removal of the collagen layer and the degree of tensile adhesive strength. When a bonding agent containing 5 wt% of sodium benzenesulfinate was used, an tensile adhesive strength of 8.1 MPa was retained after 20, 000 thermal cyclings and there was also no decrease in adhesion due to broken adherend. Use of our surface treatment method for dentinal abutment teeth produced excellent marginal adaptation compared with no pretreatment and when only primary pretreatment was made. Marginal adaptation was improved by increasing the concentration of sodium benezenesulfinate.
Our pretreatment method is considered instrumental for providing greater tensile adhesive strength and improved marginal adaptation.
