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Dent Mater. 2010 Nov;26(11):1113-8. doi: 10.1016/ Epub 2010 Aug 25.

Long-term degradation of enamel and dentin bonds: 6-year results in vitro vs. in vivo.

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University of Tennessee, Memphis, 38163, USA.



To evaluate marginal integrity of direct resin composite restorations before and after thermo-mechanical loading in vitro, and before and after 6 years of clinical service in a prospective clinical trial.


For the in vitro part, MO cavities with the proximal box beneath the cemento-enamel junction were prepared in 32 extracted human third molars. The specimens were randomly assigned to four groups (n=8) and received bonded resin composite restorations (two groups each Grandio bonded with Solobond M and Tetric Ceram bonded with Syntac). Specimens were subjected to three different aging protocols: 6-year water storage (WS), thermo-mechanical loading (TML; 100,000×50N; 2500×+5/+55°C), and 6-year water storage plus thermo-mechanical loading (WS+TML). Initially and after aging, marginal qualities in enamel and dentin were evaluated using replicas at 200× magnification (SEM). For the in vivo part, 30 patients received 68 direct resin composite restorations of the same materials in a prospective clinical trial. Replicas of 11 selected subjects per group were assessed for marginal quality under a SEM at 200×.


in vitro, all initial results showed nearly 100% gap-free margins. For TML, percentages of gap-free margins dropped to 87-90% in enamel and to 58-66% in dentin (p<0.05). For WS, enamel margins still were at 97-99% whereas dentin margins exhibited 67-75% gap-free margins, and for WS+TML, enamel margins were at 85-87% and dentin margins at 42-52% gap-free margins. In vivo, gap-free enamel margins were reduced from initially 86-90% to 74-80% after 6 years of clinical service (p<0.05). Proximally exposed dentin margins were not recordable by impressions, however, clinically no considerable problems like recurrent caries or discolorations were detected.


In vitro, hydrolytic degradation supports mechanical fatigue in dentin-composite bonds over time. In vivo, wear phenomena are superimposing marginal quality aspects. Gaps between enamel and resin composite did not play a major role.

[Indexed for MEDLINE]

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