Abstract
Purpose Secondary caries originate from a leakage pathway where oral acids can penetrate faster and demineralize the tooth substrate deeper which can be visualized by dye penetration. The ability to prevent secondary caries by contemporary adhesive systems was evaluated in this study. Dye penetration distance through leakage and into the tooth substrate adjacent to Class V restorations after artificial caries exposure was compared. Materials and Methods Previously frozen extracted human molars were used to prepare the Class V cavities at the CEJ on axial surfaces. All cavities were restored with either the resin-composite or amalgam with or without resin adhesives: dry bonding: Super-Bond D-Liner II Plus; moist bonding: All-Bond 2; and self-etch bonding: AQ Bond and Clearfil Protect Bond. Two subgroups of Super-Bond D-Liner II Plus were immersed for 14 days at 37°C either in artificial saliva (negative control) or the artificial caries solution. The other groups were soaked in the artificial caries solution. The distance of dye penetration into the adjacent enamel, cementum/dentin, and tooth-resin interfaces was measured after immersion in 0.5% basic fuchsin dye for 24 h. The tooth-resin interfacial layer was investigated using SEM. Results No dye penetration into the tooth-resin interface was found in Super-Bond D-Liner II Plus and AQ Bond groups which demonstrated a constant hybrid layer after a chemical challenge. The leakage distance at the cementum/dentin-resin interface of All-Bond 2, Clearfil Protect Bond, and non-adhesive amalgam (positive control) groups was significantly higher than the distance of dye penetration into the adjacent demineralized root surface (p < 0.05). Conclusion Caries associated with either amalgam or resin-composite restorations can be prevented using resin adhesives which can penetrate into the intact tooth substrate to form a stable hybrid layer. With caries-free restorations, tooth vitality may be conserved lifelong.
Highlights
Amalgam restorations have been used worldwide for more than 120 years because they are long lasting, low cost, and/or easy to manipulate
A leakage-free tooth-resin interface at the enamel and cementum/dentin margins was found in restorations coupled with Super-Bond D-Liner II Plus for both subgroups that were soaked in artificial saliva and a lactic acid buffer and AQ-Bond specimens (Figures 1 and 2)
No dye penetration into the adjacent enamel and cementum/dentin surfaces was found in all specimens soaked in artificial saliva (Sup, negative control), while specimens in all groups after artificial caries exposure showed dye penetration into the adjacent root surfaces with an average distance of 0.175 ± 0.039 mm (n 48)
Summary
Amalgam restorations have been used worldwide for more than 120 years because they are long lasting, low cost, and/or easy to manipulate. Hybridization of resin into the enamel or dentin creates a hybrid layer which provides the adhesion strength to the above cured resin adhesives [1]; with amalgam or resin-composite restorations coupled with this layer, it is not necessary to remove the sound tooth structure for mechanical retention or strength for long-term survival [2, 3]. Many dentin-bonding adhesives such as a totaletch with either dry or moist techniques and self-etch systems have been introduced into the worldwide market to promote better retention and bond strength between the tooth-colored filling materials and the dentin substrate. Impermeable hybridized dentin prepared by penetrating a polymer network using 4-methacryloyloxyethyl trimellitate anhydride in methyl methacrylate initiated by the tri-n-butyl
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