Self-etch vs etch-and-rinse adhesives: effect of thermo-mechanical fatigue loading on marginal quality of bonded resin composite restorations.
OBJECTIVE
This study evaluated the marginal integrity of dentine adhesives bonded to enamel and dentine, before and after thermo-mechanical loading (TML).


METHODS
MO cavities with proximal boxes beneath the CEJ were prepared in extracted human third molars. Direct resin composite restorations (Tetric Ceram) were bonded with 3-step etch-and-rinse (Syntac Classic, Solobond Plus, OptiBond FL), 2-step etch-and-rinse (Admira Bond, Single Bond), 2-step self-etch (AdheSE, Clearfil SE Bond), and 1-step self-etch (all-in-one) adhesives (Adper Prompt, Xeno III, iBond). Marginal gaps were analyzed using SEM of epoxy resin replicas. Bonded interfaces before TML were examined with TEM to identify pre-existing attributes for subsequent marginal disintegration.


RESULTS
In enamel, high percentages of gap-free margins were initially identified for all adhesives. After TML, etch-and-rinse adhesives exhibited significantly higher percentages of gap-free margins (approximately 90%) compared with two-step self-etch (approximately 75%) and all-in-one (approximately 55%) adhesives (p<0.05). iBond did not completely etch through the enamel smear layer. In dentine, 89-100% gap-free margins were initially observed. After TML, there were no statistical differences among etch-and-rinse (62-70%) and two-step self-etch (62-63%) adhesives (p>0.05). The all-in-one adhesives exhibited significantly less gap-free margins (<40%) in dentine (p<0.05), with iBond showing the worst marginal integrity (15%). The presence of pre-existing water channels within the adhesives probably expedited water sorption when restorations were under functional stresses.


CONCLUSIONS
Enamel bonding was more effective with phosphoric acid-etching. Etch-and-rinse and 2-step self-etch adhesives showed promising marginal adaptation to dentine and may have a better clinical prognosis than the all-in-one bonding approach.
Frankenberger
Roland
R
Dental Clinic I Operative Dentistry and Periodontology, University of Erlangen-Nuremberg, Glückstrasse 11, D-91054 Erlangen, Germany. frankbg@dent.uni-erlangen.de
Tay
Franklin R
FR
D000134:Acid Etching, Dental / Q000379:methods*; D000180:Acrylic Resins; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins; D001840:Dental Bonding; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D017220:Dentin-Bonding Agents; D006358:Hot Temperature; D006801:Humans; D008689:Methacrylates; D010755:Organophosphates; D011897:Random Allocation; D019279:Resin Cements; D018709:Statistics, Nonparametric
D000180:Acrylic Resins; C489662:AdheSE cement; C489661:Adper Prompt Self-Etch; C438313:Clearfil SE Bond; D003188:Composite Resins; D017220:Dentin-Bonding Agents; D008689:Methacrylates; C469607:OptiBond FL; D010755:Organophosphates; D019279:Resin Cements; C488002:Solobond Plus adhesive; C078484:Syntac dentine adhesive; C121818:Tetric ceram; C487957:Xeno III; C479085:admira bond; C477386:iBond; C115612:single bond; D017438:Bisphenol A-Glycidyl Methacrylate