Microtensile bond strength of a total-etch 3-step, total-etch 2-step, self-etch 2-step, and a self-etch 1-step dentin bonding system through 15-month water storage.
OBJECTIVE
To evaluate dentin bond durability using current dentin adhesive resin bonding approaches over a 15-month period of water storage.


METHODS
Forty-four extracted human molars were polished with 600-grit SiC papers exposing occlusal dentin, and randomly distributed into four adhesive groups: total-etch 3-step (TE3) (Scotchbond Multi-Purpose, 3M ESPE), total-etch 2-step (TE2) (Single Bond, 3M ESPE), self-etch 2-step (SE2) (Clearfil SE Bond, Kuraray), and a self-etch 1-step (SE1) (Prompt L-Pop, 3M ESPE). A resin composite crown was incrementally formed and light cured to approximately 6 mm in height. Microtensile specimens were fabricated and stored in distilled water containing 0.5% chloramine T and tensile tested at 1 mm/min after 1, 6, and 15 months. The debond pathway was recorded as either involving the substrate or joint using scanning electron microscopy. SAS software was used to compute Weibull parameters and distributions, Log-rank and Wilcoxon tests were used for comparison of survival curves over time for each adhesive system and between adhesive systems.


RESULTS
The TE2 was significantly weaker than TE3 and SE2 after 1 and 6 months of storage, but all three systems were equivalent after 15 months of storage. The SE1 system could not be tested due to 58 of 65 specimens failing during specimen preparation. Failure modes were observed to be dependent upon adhesive system, with only the total-etch 2-step system demonstrating an increasing involvement in the adhesive joint over time.


CONCLUSIONS
Although differences in bond strength were observed across adhesive systems up to 6 months of storage, no differences were noted at 15 months. This may represent common degradative mechanisms.
Department of Operative Dentistry, The University of Iowa, Iowa City, Iowa, USA. steven-armstrong@uiowa.edu
Steven R
SR
Armstrong
Marcos A
MA
Vargas
Qian
Q
Fang
John E
JE
Laffoon
D000134:Acid Etching, Dental; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins; D003442:Crowns; D001840:Dental Bonding; D017220:Dentin-Bonding Agents / Q000737:chemistry*; D006801:Humans; D016014:Linear Models; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D019279:Resin Cements / Q000737:chemistry; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013499:Surface Properties; D016019:Survival Analysis; D013718:Tensile Strength; D013997:Time Factors; D014867:Water / Q000737:chemistry
C438313:Clearfil SE Bond; D003188:Composite Resins; D017220:Dentin-Bonding Agents; C408584:Prompt L-Pop; D019279:Resin Cements; C425844:Scotchbond Multi-Purpose Plus; C115612:single bond; D014867:Water; D017438:Bisphenol A-Glycidyl Methacrylate