Bond strength between root dentin and three glass-fiber post systems

Laboratory assessment of the retentive potential of adhesive posts: a review

OBJECTIVES

This review aimed at summarizing the laboratory evidence collected on the retentive ability of adhesive posts since their introduction in dentistry.

DATA

Data were searched in articles published or in press in peer-review journals listed in MEDLINE.

SOURCES

Papers were retrieved through PubMed.

STUDY SELECTION

To collect the evidence of interest, the following search terms were used: bond* AND fiber post AND in vitro; lut* AND fiber post AND in vitro; push-out AND fiber post; pull-out AND fiber post; microtensile AND fiber post. "Related Links" were also considered and articles cited in the initially retrieved papers were included if relevant. No time limit was given to the query.

CONCLUSIONS

Seventy relevant papers were reviewed. The retentive ability of adhesive posts has been tested with the microtensile technique, post-pull-out and push-out tests. If small-sized specimens are obtained, such as in microtensile and thin-slice push-out, stress uniformity is favoured, local differences in bonding conditions can be discerned, and the number of teeth needed for the test can be reduced. Although adhesion to intraradicular dentin is more challenging to achieve than bonding to crown tissues, the post-retention achieved with current luting systems and techniques is adequate to ensure the clinical success of adhesive post-retained restorations. To enhance the bond at the post-core and post-cement interfaces, several chemical pre-treatments of the post-surface have been tested with positive results. Self-adhesive resin cements, recently proposed to simplify the post-luting procedure, should be investigated further with regard to durability.

The effect of resin cement film thickness on the pullout strength of a fiber-reinforced post system

STATEMENT OF PROBLEM

Debonding is a common cause of failure encountered with fiber posts and usually occurs along the post space-dentin adhesive interface. The ideal thickness of the resin cement needed to improve retentive bond strength is unknown.

PURPOSE

The purpose of this study was to evaluate the effect of 4 different post-space diameters and related resin cement film thicknesses on the bond strength between fiber posts and root dentin.

MATERIAL AND METHODS

Eighty human maxillary central incisors with similar root lengths were selected, sectioned at the cemento-enamel junction, and the roots were treated endodontically. The roots were divided into 4 groups (n=20), and the post spaces were prepared to a depth of 8 mm using 1 of 4 different drills with a different diameter: Torpan drill ISO 90 for the control group (D90); and Torpan Drill ISO 100 (D100), Torpan Drill ISO 120 (D120), or Enapost Drill ISO 140 (D140) for the 3 test groups. Quartz fiber posts (Endo Lightpost), 0.9 mm in apical diameter, were luted (Panavia 21) in each specimen after dentin bonding procedures. The specimens were then subjected to a pullout test using a universal testing machine at a crosshead speed of 1.0 mm/min, and the maximum force required to dislodge each post was recorded (N). Data were analyzed using 1-way ANOVA and Tukey multiple comparisons tests (a=.05).

RESULTS

The mean bond strength values (SD) in N for the experimental groups D100 (181.7 (55.3)) and D120 (210.7 (55.0)) were higher (P=.036 and <.001, respectively) than that obtained for the D90 control group (138.5 (49.2)). The lowest mean value was recorded for the D140 group (91.1 (36.0)). All experimental groups showed significantly different results, when compared to the control group. A multiple comparison between experimental groups showed significant differences (P<.001). Only the comparison between D100 versus D120 was not significant.

CONCLUSIONS

Data suggest that the resin cement film thickness influences the pullout strengths of fiber-reinforced posts. For the selected quartz fiber-reinforced post and resin luting cement, the highest bond strength values were not obtained when the thinnest cement layer was tested (D90) but when oversized post spaces were used (D100-D120). However, when the cement film thickness was too great (D140), the dislocation resistance of fiber-reinforced posts was significantly decreased.