Comparison of titanium dowel retention using four different luting agents.
BACKGROUND
Luting material, surface properties, and loading conditions affect the retention of prefabricated dowels to varying degrees.


OBJECTIVE
The purpose of this study was to evaluate the effect of roughening of the dentinal walls and artificial aging on the retention of prefabricated tapered titanium dowels, using 4 different luting materials.


METHODS
One-hundred twenty-eight single-rooted teeth were selected, the coronal aspect of each tooth was removed, and the remaining root received endodontic therapy. All specimens were divided into 4 groups (n=32). Dowel spaces were prepared to a depth of 10 mm using ISO 90 rotary cutting instruments. Tapered titanium dowels were luted with the following luting materials: zinc-phosphate cement (Harvard cement), glass-ionomer cement (Ketac Cem EasyMix), resin composite luting agent (Panavia 21) with autopolymerizing dentin primer (ED-Primer), or a self-adhesive composite luting agent (RelyX Unicem). Both composite luting agents were used without acid etching of the canal dentin. Each luting agent was used under 2 conditions: in 1 subgroup (n=16) the dentinal walls were not roughened, and in the other subgroup (n=16), walls were roughened with a diamond rotary cutting instrument. Eight specimens from each subgroup were stored in water at 37 degrees C for 3 days; the other 8 specimens were stored for 150 days and subjected to simulated aging conditions using 37,500 thermal cycles (5 degrees C/55 degrees C) and 300,000 mechanical loading cycles with 30 N. Dowel retention (N) was measured using a universal testing machine with a crosshead speed of 2 mm/min. Data were analyzed using 2- and 3-way ANOVAs and the Tukey HSD test (alpha=.05).


RESULTS
The dislodged dowels were examined microscopically to evaluate mode of failure. The nonroughened dentinal walls showed no significant differences between the different luting agents. Roughening the dentinal walls increased the retention significantly for all groups. This increase was significantly higher for the resin composite groups (P=.0001). Storage for 150 days with thermal cycling and mechanical loading caused a significant decrease in dowel retention (P=.001). The failure mode was purely adhesive at the luting material-dentin interface for all dowels cemented in nonroughened root canals. A mixed failure mode, adhesive at the luting material-dentin interface and cohesive in the luting material, was observed for dowels cemented in roughened root canals.


CONCLUSIONS
Roughening the dentinal walls and the use of resin luting cements provided statistically significant increases in dowel retention values.
Balbosh
Ali
A
School of Dentistry, Department of Prosthodontics, Propaedeutics, and Dental Materials, Christian-Albrechts University at Kiel, Arnold-Heller Strasse 16, 24105 Kiel, Germany.
Ludwig
Klaus
K
Kern
Matthias
M
D000704:Analysis of Variance; D002484:Cementation / Q000379:methods*; D017268:Dental Prosthesis Retention; D003799:Dental Stress Analysis; D003804:Dentin; D005899:Glass Ionomer Cements; D006801:Humans; D008277:Magnesium Oxide; D008422:Materials Testing; D010710:Phosphates; D011076:Polycarboxylate Cement; D011176:Post and Core Technique; D019279:Resin Cements; D018915:Root Canal Preparation / Q000379:methods; D013499:Surface Properties; D013718:Tensile Strength; D013997:Time Factors; D014025:Titanium; D015034:Zinc Oxide; D015036:Zinc Phosphate Cement
D005899:Glass Ionomer Cements; C093719:Panavia TPN-S; D010710:Phosphates; D011076:Polycarboxylate Cement; C483701:Rely X Unicem; D019279:Resin Cements; D008277:Magnesium Oxide; D015036:Zinc Phosphate Cement; C074226:Harvard Cement; C040235:Ketac-cem; D014025:Titanium; D015034:Zinc Oxide