The effect of phosphoric acid pre-etching and thermocycling on self-etching adhesive enamel bonding.
BACKGROUND
When inserting a resin-bonded prosthesis, it is not known whether pumicing, rinsing, and using a self-etching primer (SE) on prepared surfaces is sufficient or whether the use of an additional conventional acid etchant is warranted due to the increased time and risk of contamination.


OBJECTIVE
The purpose of this study was to evaluate the effects of pre-etching with phosphoric acid (PA) and thermocycling (TC) on the enamel shear bond strength (SBS) of an autopolymerizing adhesive system on ground enamel.


METHODS
Human teeth were embedded in phenolic rings with methyl methacrylate resin, and their enamel surfaces were ground flat to a 600 grit surface. The teeth were then divided into 4 subsets (n=22): 1) PSN, PA pre-etch with SE, no TC; 2) PST, PA pre-etch with self-etching primer and TC; 3) SEN, self-etching primer alone, no TC; and 4) SET, self-etching primer and TC. A multifactorial study design was used to evaluate 2 factors (pre-etching with PA and TC) at 2 levels (presence or absence) by grouping different subsets. Pre-etch consisted of teeth being etched for 30 seconds with PA, rinsed, re-etched, and rinsed. Self-etching consisted of 60 seconds with ED Primer. Rods of Rexillium III, airborne-particle abraded with 50 μm aluminum oxide, were bonded to enamel surfaces with Panavia 21 OP under a 19.6 N load. Thermocycling consisted of alternating between water baths of 5 ± 2°C and 55 ± 2°C for 5000 cycles. Shear bond strength (SBS) was determined by loading the specimens to failure at a crosshead speed of 1 mm/min. Mean values were analyzed with a 2-way ANOVA (factors were surface treatment and TC) at α=.05.


RESULTS
Pre-etching with phosphoric acid showed greater SBS to enamel (P=.028) than the self-etching primer alone. Thermocycling did not have a significant effect (P=.424).


CONCLUSIONS
There was a significant difference in SBS between pre-etching enamel surfaces with phosphoric acid in addition to the self-etching primer and using the self-etching primer exclusively. Thermocycling did not significantly affect SBS.
Department of Prosthodontics, Creighton University School of Dentistry, Omaha, NE 68178, USA. jsheets@creighton.edu
James L
JL
Sheets
Charles W
CW
Wilcox
Wayne W
WW
Barkmeier
Martha E
ME
Nunn
D000134:Acid Etching, Dental / Q000379:methods*; D000268:Adhesiveness; D000537:Aluminum Oxide / Q000737:chemistry; D002858:Chromium Alloys / Q000737:chemistry; D001840:Dental Bonding / Q000379:methods*; D003743:Dental Enamel / Q000648:ultrastructure*; D045662:Dental Etching / Q000379:methods; D003799:Dental Stress Analysis / Q000295:instrumentation; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D010710:Phosphates / Q000737:chemistry; D010756:Phosphoric Acids / Q000737:chemistry*; D019279:Resin Cements / Q000737:chemistry*; D033081:Shear Strength; D013314:Stress, Mechanical; D013696:Temperature; D013997:Time Factors; D014867:Water / Q000737:chemistry
D002858:Chromium Alloys; C500742:ED Primer II; D008689:Methacrylates; C093719:Panavia TPN-S; D010710:Phosphates; D010756:Phosphoric Acids; D019279:Resin Cements; D014867:Water; C036884:Rexillium III; C030242:phosphoric acid; D000537:Aluminum Oxide