Microtensile bond strength at the gingival-wall under 15.0 cm/H2O pressure

Resin composite restorations are bonded to teeth using total-etch or self-etch adhesive systems.  Under in-vivo conditions, adhesives are affected by a positive pulpal pressure of 5-15 cm/H₂O.  Objectives:  The purpose of this study was to compare two self-etch and two total-etch adhesive systems bonded to the gingival floor of class II resin composites placed on teeth under a simulated positive pulpal pressure of 15 cm/H₂0 with the pulp intact.  Methods:  After IRB approval, eleven pairs of extracted human third molars were collected. Each pair of teeth received proximal box preparations on the mesial and distal before mounting the teeth on plexiglas with a metal tube extending into the pulp canal.  Each tooth was placed under a positive pulpal pressure of 15 cm/H2O with the pulp intact.   Each tooth was randomly restored with one of the adhesive systems; A-PQ1- TE-(Total etch) (Ultradent); B-Peak-LC -TE(Ultradent); C-Clearfil-SE (self-etch) (Kuraray); D-Optibond XTR-SE(Kerr).  Filtek Z-250 was used to restore the teeth.  24 hours later, restorations were sectioned into beams of approximately 0.5mm² and tested for microtensile bond strength using a Bisco microtensile tester at a crosshead speed of 2.0mm/min.  A light microscope (50x) was used to characterize the modes of failure as either adhesive or cohesive.

Results:  

Adhesive	N	Mean MPa (Std)	Cohesive Failures	Debonds
Peak LC	11	37.2 (15.1)A	0	0
PQ1	11	25.0 (10.0)AB	0	2
Clearfil SE	11	36.3 (14.5)AB	0	0
Optibond XTR	11	48.7 (14.1)B	1	0

 

A one way ANOVA found a statistical difference between the adhesives (p<0.01).  A post-hoc Ryan-Einot-Gabriel-Welsch-F test found Optibond XTR stronger than PQ1.  Conclusions:  Under a positive pulpal pressure of 15.0cm with pulp intact a self etch ethanol based Optibond XTR performed better than a total etch ethanol based adhesive PQ1.  Supported in part by USPHS-Grant K23-DE016324 and UMKC Summer Scholars Program.   purkj@umkc.edu