The effect of load cycling on nanoleakage of deproteinized resin/dentin interfaces as a function of time.
OBJECTIVE
To evaluate the effects of cyclic loading on nanoleakage as a function of time at resin-dentin interfaces with and without removal of collagen.


METHODS
Bovine flat mid-coronal dentin received one of the following surface treatments: (1) acid-etch or (2) acid etched+5% NaOCl for 2m. The teeth were then bonded with Single Bond (3M ESPE), Scotchbond Multi-Purpose (3M ESPE), One-Step Plus (Bisco) or All-Bond 2 (Bisco) adhesive systems and restored with Z250 composite. Half of the bonded teeth were randomly assigned to receive 200,000 cycles of loading at 50 N. Teeth were sectioned into 1 mm x 1 mm thick slices and stored in distilled water for 24h and 6 months. After water storage, beams were prepared for nanoleakage evaluation and observed under the SEM. Data were statistically analyzed using three-way ANOVA and Fisher's PLSD test (p<0.05).


RESULTS
Use of NaOCl did not affect nanoleakage at the interface of all adhesive systems (p>0.05) when compared to their respective controls. After 6 months of immersion in water, except for One Step Plus, collagen-depleted groups and control groups presented similar leakage values. After cyclic loading, the deproteinized group revealed a higher degree of silver nitrate deposits when compared to the control group (p<0.05). All four adhesive systems presented a high degree of silver nitrate deposits after 6 months of water storage.


CONCLUSIONS
The hybrid layer is important as a stress-absorbing layer and it may not represent the weak link for initiation of the nanoleakage phenomenon.
Yamazaki
Paula C V
PC
Department of Operative Dentistry, School of Dentistry, University of North Carolina, Chapel Hill, NC, USA. paulayamazaki@hotmail.com <paulayamazaki@hotmail.com>
Bedran-Russo
Ana Karina B
AK
Pereira
Patricia N R
PN
D000134:Acid Etching, Dental / Q000379:methods; D000818:Animals; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D002417:Cattle; D003094:Collagen / Q000648:ultrastructure*; D003188:Composite Resins / Q000737:chemistry*; D003763:Dental Leakage / Q000145:classification*; D003804:Dentin / Q000648:ultrastructure*; D017220:Dentin-Bonding Agents / Q000737:chemistry; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D016877:Oxidants / Q000737:chemistry; D011897:Random Allocation; D019279:Resin Cements / Q000737:chemistry; D016622:Silver Staining; D012973:Sodium Hypochlorite / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
D003188:Composite Resins; D017220:Dentin-Bonding Agents; C444701:Filtek Z250; D008689:Methacrylates; D016877:Oxidants; D019279:Resin Cements; C084018:Scotchbond Multi-Purpose; C115612:single bond; D014867:Water; C100742:All-Bond 2; D017438:Bisphenol A-Glycidyl Methacrylate; D003094:Collagen; D012973:Sodium Hypochlorite