Dental Adhesion or Dental Bonding Adhesion is a process of solid and/or liquid interaction of one material with another at a single interface.
Enamel bonding system Enamel bongding depends on resin tags becoming interlocked with the surface irregularities created by etching.
Macrotags: form between enamel rod peripheries. Microtags: smaller tags form across the end of each rod. Macrotags and microtags are the basis for micro-mechanical bonding.
Dentin bonding system The difficulties of dentin bonding: More water---wet bonding Lower calcification Richer organic---collagen network Smear layer
The bond strength is primarily related to micro-mechanical bonding to the intertubular dentin which occures between tubules along the cut dentin surface.
Dentin Bonding Agent, DBA Early DBA were hydrophobic, bonded directly to the dentin smear layer. Bond strengths ＜ 6MPa. Later DBA removed the smear layer but tended to over-etch dentin. Bond strengths≈10~12MPa.
DBA were chemically modified to be more hydrophilic. Bond Strengths≈18~20MPa. Careful dentin conditioning, Coupled with hydrophilic primer, Bond Strength≈22~35MPa.
The Development of DBA Enamel etch (1955) Dentine etch (1960) Treatment of smear layer (1980) Wet Bonding technique(1990)
First generation Second generation Third generation Fourth generation: Total etch technique Fifth generation: One bottle system Sixth generation: All in one,2000 Seventh generation
Cavity Preparation Three designs of cavity preparation: 1.Conventional 2.Beveled conventional 3.Modified
Beveled conventional cavity preparations are similar to conventional preparation, in that the outline form has external, “box-like” walls, but with beveled enamel margin.
Beveled conventional cavity designs for Class Ⅲ, Ⅳ and Ⅴ preparations
The advantages : The ends of enamel rods are more etched The increase in etched surface results in a stronger bond Increase the retention and reduce marginal leakage and discoloration. More esthtically
Modified cavity preparation Have neither specified cavity wall structure nor specified pulpal depth, and have enamel margins. Conserve more tooth structure.
Conservative Operative Dentistry Minimal intervention dentistry is regards as a main stream in caries treatment in the 21 st century.
Principles of Minimal Intervention dentistry Remineralization of early lesions Reduction in cariogenic bacteria, to elminate the risk of further demi- neralization and cavitation Minimum surgical intervention of ca- vitated lesions Repair rather than replacement of defective restorations
“The day is surely coming, and perhaps within the lifetime of you young men before me, when we will be engaged in practicing preventive, rather than reparative, dentistry. ” — GV Black in 1896