Fracture Resistance of Tilted Premolars Restored with Different Post-Core Systems

Biomechanical Assessment of Tilted Mandibular Second Molars with Full-Crown Adjacent to Implant-Supported Restoration: 3D Finite Element Analysis

Purpose

Materials and Methods

Results

Conclusion

Fracture resistance and stress distribution of weakened teeth reinforced with a bundled glass fiber-reinforced resin post

OBJECTIVES

To make an in vitro assessment of fracture resistance of weakened and non-weakened teeth receiving intraradicular reinforcement using Rebilda bundled glass fiber-reinforced composite posts (GT), Rebilda conventional glass fiber posts (RP), or both systems combined (GT + RP).

MATERIALS AND METHODS

Eighty sound bovine incisors were prepared and divided randomly into eight groups as follows: (a) nWnR: without simulating weakness, and without intraradicular reinforcement; (b) WnR: simulating weakness, but without intraradicular reinforcement; (c) nWGT: without simulating weakness, but with GT; (d) WGT: simulating weakness, and with GT; (e) nWRP: without simulating weakness, but with RP; (f) WRP: simulating weakness, and with RP; (g) nWGTRP: without simulating weakness, but with GT + RP; (h) WGTRP: simulating weakness, and with GT + RP. The specimens were subjected to the load-to-fracture test using the DL-2000MF universal testing machine. The finite element method assessed the mechanical behavior and stress distribution in endodontically treated teeth.

RESULTS

The groups nWGTRP and WGTRP presented the best results in the load-to-fracture test, with the former being better than the latter, but with no statistically significant difference (P > 0.05). However, there was a significant difference between these and the other groups (P < 0.05), except for nWRP. Stress distribution inside the canal wall was different among the groups, with promising mechanical behavior for nWGTRP and nWRP.

CONCLUSIONS

The Rebilda conventional fiber post (RP), combined with the Rebilda bundled glass fiber-reinforced composite post (GT) improves the resistance and stress distribution of immature teeth.

CLINICAL RELEVANCE

Longitudinal fracture is less frequent in teeth restored with GT and RP posts.

Influence of Different Fibreglass Post Geometries on the Stress Distribution and Pull-Out Bond Strength Before and After Mechanical Cycling

OBJECTIVE

There are no reports in the literature on whether FGP geometry influences the bond strength of the endodontically restored tooth. This study aimed to determine the stress distribution and the pull-out bond strength of different FGP geometries, before and after chewing loads simulation.

METHODS

One hundred and twenty root analogues were prepared and randomly distributed in six groups according to the post geometry. Half of the specimens were aged in water at 37 °C using a mechanical fatigue machine (84 N, 2 bar, 45°, 106 cycles, 4 Hz); while the remaining specimens were immediately submitted to the pull-out bond strength test. The specimens were tested in a universal testing machine and the bond strength in MPa was calculated. To assess the stress concentration, the finite element method was used simulating the same post geometries that were used in the in vitro test.

RESULTS

Two-way ANOVA (95%) showed no influence of post geometry on the bond strength (P=0.055) while fatigue cycling was statistical significant to reduce the bond strength values (P=0.000). The factors interaction was significant (P=0.019); however, TUKEY test (5%) showed no significant difference between post geometries after mechanical cycling. The tensile stress result showed critical areas in the post's cervical region regardless of the design.

CONCLUSION

The FGP geometry does not affect the root stress distribution and the long-term bond strength. However, FGP that allow a reduced cement layer thickness can improve the immediate pull-out bond strength value.

Fracture strength of endodontically treated premolars restored with different post systems and metal-ceramic or monolithic zirconia crowns

The purpose of this study was to investigate the fracture strength of endodontically treated human maxillary premolars (ETP) restored with posts and metal ceramic (MC) or monolithic zirconia (MZ) crowns. Sixty ETP were randomly divided into 3 groups. Teeth in control group (C) received a resin filling. ETP in the MC group were restored with prefabricated metal posts, composite cores and MC crowns while in the MZ group with glass-fiber posts, composite cores and MZ crowns. Half of the specimens were loaded at a 135° angle and half under axial loading until fracture. The fracture modes were divided in repairable and irreparable using optical microscopy. Mean fracture strength was significantly higher for MC than for MZ crowns and control group only under axial loading. The distribution of repairable and irreparable failures presented no significant differences. Crown placement significantly improved the fracture strength of ETP irrespectively of post and crown type.

Root canal reconstruction using biological dentin posts: A 3D finite element analysis

Background. Several types of post have been developed for clinical use. A biological dentin post obtained from an extracted tooth eliminates the problems arising from material differences and reduces the fracture rate in teeth undergoing root canal treatment. This study used finite element analysis to compare a biological dentin post with posts made of two different materials. Methods. Three 3D models of the upper central incisor were created, and stainless-steel, glass fiber and biological dentin posts were applied to these models. The restoration of the models was completed by applying a composite as the core structure and a ceramic crown as the superstructure. Using finite element stress analysis in the restoration models, a 100-N force was applied in the vertical and horizontal directions and at a 45º angle, and the suitability of the biological dentin post was evaluated by comparing the data. Results. Under the applied forces, the greatest stress accumulation was seen in the models with the stainless steel post. Because the stainless steel post was more rigid, stress forces accumulated on the surface instead of being transmitted to the tooth tissue. In the models with the glass fiber and biological dentin posts, the post material responded to the stratification in tandem with the dental tissue and did not cause excessive stress accumulation on the tooth or post surfaces. Conclusion. The results showed that biological dentin posts prevent the accumulation of stresses that might cause fractures in teeth undergoing root canal treatment. In addition, the physical compatibility and biocompatibility of a biological dentin post with the tooth imply that it is a good alternative to the types of post currently used.

Bond Strength and Fracture Resistance of Flowable Bulk Fill Composite Posts and Cores in Endodontically Treated Teeth

OBJECTIVES

Smart dentin replacement (SDR) is a new flowable bulk fill composite with many useful characteristics such as low viscosity and higher depth of cure. This study aimed to evaluate the bond strength and fracture resistance of flowable bulk fill composite posts and cores versus that of fiber posts and cores.

MATERIALS AND METHODS

Forty intact, extracted human maxillary central incisor roots were endodontically treated. Group A (n = 20) was prepared for the composite space and group B (n = 20) was prepared for the fiber post space. Group A and B were divided into two subgroups A1 and A2 and B1 and B2, respectively (10 roots for each subgroup). Root canal spaces of group A1 were filled with SDR composite, X-Post fiber post with Core X Flow composite was inserted into the root canal spaces of group B1. Group A2 was restored using SDR and group B2 was restored using post and core composite. Five hundred thermocycles were applied for the sample. Bond strength values were measured for segments in A1 and B1. Fracture force values were measured for specimens of A2 and B2.

RESULTS

No significant difference was observed between the two paired groups (A1 and B1) and (A2 and B2) in bond strength and fracture force values.

CONCLUSION

SDR could be used for restoring endodontically treated teeth.