Durability of the bond between resin composite cores and prefabricated posts

Evaluation of the Bond Strength and Fracture Resistance of Different Post Systems

AIM

To compare the bond strength and the fracture resistance of different post systems.

MATERIALS AND METHODS

Endodontically treated 60 mandibular incisor and 60 mandibular premolar teeth were used for the bond strength and fracture resistance test respectively. For each test, three groups (n = 20) were formed according to the posts used zirconia posts (ZR post), individually formed glass fiber reinforced composite posts with an (Interpenetrating Polymer Network-IPN post) and cast metal posts. Then groups were randomly assigned into two subgroups according to the post design: 1-parallel sided and 2-tapered (n = 10/group). All posts were luted with a self-adhesive luting agent. For push-out test two 1 mm thick horizontal root sections were obtained and subjected to push-out test. For fracture resistance test, the specimens were loaded vertically at 1 mm/min crosshead speed. The push out test data were analyzed with Kruskal-Wallis and Dunn's test. Analysis of variance (ANOVA) and Tukey significant difference tests were used to compare the fracture resistance.

RESULTS

Cast metal posts showed the highest retention (p < 0.05); however, IPN and zirconia posts showed similar results. No significant difference was found between parallel sided or tapered designs of post groups in terms of bond strength (p > 0.05). In terms of fracture resistance, IPN post groups showed lowest fracture resistance (p < 0.05). No significant difference was found between parallel sided or tapered posts in terms of fracture resistance, except zirconia post (p > 0.05). There was no relationship between the bond strength and fracture resistance of the post systems (r = - 0.015, p > 0.700).

CONCLUSION

Post type had effect both on the fracture resistance and retention of the posts used. However, post design had effect only on the fracture resistance of the post systems.

CLINICAL SIGNIFICANCE

Superficial treatment of the post used can improve the retention of post systems.

Effect of components and surface treatments of fiber-reinforced composite posts on bond strength to composite resin

The aim of this study was to clarify the effect of the components and surface treatments of fiber-reinforced composite (FRC) posts on the durable bonding to core build-up resin evaluated using the pull-out and microtensile tests. Four types of experimental FRC posts, combinations of two types of matrix resins (polymethyl methacrylate and urethane dimethacrylate) and two types of fiberglass (E-glass and zirconia-containing glass) were examined. The FRC posts were subjected to one of three surface treatments (cleaned with ethanol, dichloromethane, or sandblasting). The bond strength between the FRC posts and core build-up resin were measured using the pull-out and microtensile tests before and after thermal cycling. The bond strengths obtained by each test before and after thermal cycling were statistically analyzed by three-way ANOVA and Tukey's multiple comparisons test (p<0.05). The bond strengths except for UDMA by the pull-out test decreased after thermal cycling. Regardless the test method and thermal cycling, matrix resins, the surface treatment and their interaction were statistically significant, but fiberglass did not. Dichloromethane treatment was effective for the PMMA-based FRC posts by the pull-out test, but not by the microtensile test. Sandblasting was effective for both PMMA- and UDMA-based FRC posts, regardless of the test method. The bond strengths were influenced by the matrix resin of the FRC post and the surface treatment. The bond strengths of the pull-out test showed a similar tendency of those of the microtensile test, but the value obtained by these test were different.

Comparative evaluation of effects of different surface treatment methods on bond strength between fiber post and composite core

PURPOSE

Debonding of a composite resin core of the fiber post often occurs at the interface between these two materials. The aim of this study was to evaluate the effects of different surface treatment methods on bond strength between fiber posts and composite core.

MATERIALS AND METHODS

Sixty-four fiber posts were picked in two groups (Hetco and Exacto). Each group was further divided into four subgroups using different surface treatments: 1) silanization; 2) sandblasting; 3) Treatment with 24% H₂O₂, and 4) no treatment (control group). A cylindrical plexiglass matrix was placed around the post and filled with the core resin composite. Specimens were stored in 5000 thermal cycles between 5℃ and 55℃. Tensile bond strength (TBS) test and evaluation using stereomicroscope were performed on the specimen and the data were analyzed using two-way ANOVA, Post Hoc Scheffe tests and Fisher's Exact Test (α=.05).

RESULTS

There was a significant difference between the effect of different surface treatments on TBS (P<.001) but different brands of post (P=.743) and interaction between the brand of post and surface treatment (P=.922) had no significant effect on TBS. Both silanization and sandblasting improved the bonding strength of fiber posts to composite resin core, but there were not any significant differences between these groups and control group.

CONCLUSION

There was not any significant difference between two brands of fiber posts that had been used in this study. Although silanization and sandblasting can improve the TBS, there was not any significant differences between surface treatments used.

Multiple bonded restorations in a patient with severe mental disability: a case report

Dental treatment for patients with special needs may require general anesthesia, if these patients are unable or unwilling to cooperate. To administer a restorative treatment in a limited timeframe requires an interdisciplinary approach adapted to the individual. This case report describes a comprehensive restorative procedure in a patient with severe mental disability who has serious dental caries. Direct resin composites were used to reconstruct most of the damaged dentition. In the 22-month follow-up conducted by the authors, they found one restoration failure, several primary caries lesions and one secondary-caries lesion. Every other restoration remained stable, despite limited postoperative care.