Showing papers on "Post and core published in 1999"

An in vitro study of the fracture resistance and the incidence of vertical root fracture of pulpless teeth restored with six post-and-core systems

Abstract: Statement of problem. Posts and cores are often required with pulpless teeth to provide retention and resistance form for complete crowns. Nevertheless, conventional posts may increase the potential for root fracture. Purpose. This study compared the resistance to vertical root fracture of extracted teeth treated with post-core systems that were modified with polyethylene woven fibers (Ribbond) with those treated with conventional post-and-core systems. Material and methods. Canal instrumentation was performed for 60 maxillary central incisors, and complete crown preparations were made. The coronal portion of each tooth was amputated, and 6 post-and-core systems were studied. Specimens were mounted in acrylic resin blocks with a layer of polyvinyl siloxane covering the roots. Loads were applied at an angle of 130 degrees and measured with a universal testing machine. Results were analyzed statistically with 1-way analysis of variance with Student-Newman-Keuls grouping and chi-square analysis. Results. Cast posts and cores resulted in significantly higher failure thresholds than all others, except for prefabricated, comparably sized, parallel-sided posts with composite cores. All failures in the group with cast posts involved fracture of the teeth, whereas 70% of the teeth with comparably sized parallel-sided posts and composite cores failed as a result of tooth fractures and 30% experienced core fractures. The woven fiber post-core system was significantly lower in strength than all others, and exhibited significantly fewer vertical root fractures. Conclusions. Polyethylene woven fiber and composite resin without a prefabricated post resulted in significantly fewer vertical root fractures, but mean failure load was the lowest. Smaller diameter prefabricated posts combined with the polyethylene woven fiber and composite cores improved resistance to failure. Traditional cast posts and cores were the strongest of the 6 post-core systems. (J Prosthet Dent 1999;81:262-9.)

Fatigue testing and microscopic evaluation of post and core restorations under artificial crowns

Abstract: Statement of problem. Coronoradicular reconstruction techniques of pulpless teeth include prefabricated post systems that retain a core material such as silver amalgam, composite, glass ionomer, or modified glass ionomer cement. Mechanical properties of these materials are critical to sustain masticatory forces. Purpose. This in vitro study compared the mechanical resistance of 3 core materials (silver amalgam, composite, and silver-reinforced glass ionomer) under masticatory conditions. Material and methods. Industrially fabricated teeth were used and a total of 75 specimens were divided into 3 groups of 25 specimens. Titanium canal posts were placed, followed by core buildups in amalgam, composite, or glass ionomer. Teeth were prepared for full cast crowns and the crowns were fabricated and cemented with glass ionomer cement. Twenty specimens from each group were placed in a mastication simulator cyclically loading the teeth with a 400 N force for 1.5 million cycles. The 5 remaining specimens were used as controls. Teeth were sectioned and observed macroscopically and microscopically to determine the rate of defects for each material. Observed defects were verified with the Kruskal-Wallis test. The 3 core materials were ranked with the Tukey multiple comparison test. Results. Significant differences of mechanical behavior were found for the 3 materials. At P Conclusion. Cores fabricated with amalgam had the lowest rate of defects when tested under artificial crowns. Glass ionomer, when used as a core material under artificial crowns, showed the highest rate of defects after an instantaneous load of 400 N for a 1,500,000 repetition cycle. (J Prosthet Dent 1999;82:341-7.)

Retention and shear bond strength of two post systems.

Abstract: The purpose of this study was to compare the retention and shear strength of teeth restored with the Para Plus post (P) and the C post (C1 and C2) systems. Twenty-four P, C1, and C2 posts each were placed 7 mm into recently extracted and endodontically treated maxillary anterior roots and luted with Ketac-Cem and Bis-Core respectively. In addition, 13 samples of each post type had a Bis-Core composite core placed. The tensile retention strength of the post and the shear strength of the post and core restorations when the core was loaded buccolingually at 45 degrees to the roots' long axis were determined at a strain rate of 1.3 mm/min. The C2 posts required significantly more tensile force (P < 0.0001) to remove them than the P or C1 posts. The shear strength of the post/core restorations was not significantly different (P < 0.04). The C1 restorations had 12 root fractures, the C2 restorations had 11 root fractures, and the P samples had six root fractures. It was concluded that the lack of stiffness of the C posts adversely affected the success of these restorations.

Effects of cyclic loading on selected post-and-core systems.

Abstract: OBJECTIVE The purpose of this study was to evaluate the resistance of selected post-and-core systems to fatigue testing. METHOD AND MATERIALS A fatigue-testing machine and data acquisition software were developed for this in vitro test. Pulpless mandibular second premolars were treated with three different types of post-and-core system: (1) two different prefabricated posts with amalgam cores, (2) the same two prefabricated posts with resin composite cores, and (3) cast post and cores, which served as the control group. The fatigue-testing machine applied alternating buccal and lingual forces to the core until lateral movement of 0.0025 inches (63.5 microns) was detected by a transducer contacting the surface of the core. This criterion represented initial cement failure. RESULTS Although groups using the resin composite core material exhibited a higher number of cycles prior to failure, there was no statistically significant difference between the different post-and-core systems. CONCLUSION All of the post-and-core systems that were tested may be acceptable for restoring endodontically treated teeth.

Deposition of calcified tissue around an overextended gutta-percha cone: case report.

Abstract: Khabbaz MG, Papadopoulos PD. Deposition of calcified tissue around an overextended gutta-percha cone: case report (Clinical article). International Endodontic Journal, 32, 232‐235, 1999. Case report Root canal treatment was performed in a mandibular right second premolar with a periapical lesion and apical resorption. The root canal was prepared with K-files using the step-back technique and 3% NaOCl as an irrigant; during obturation gross overfilling of gutta-percha occurred. The tooth was permanently restored with a post and core along with a crown. Although healing of the periapical lesion occurred and the patient reported that he was symptom-free, the tooth was extracted after 4 years because of a subgingival root fracture. Following extraction the tooth was examined with SEM. The examination revealed the presence of newly formed calcified tissue at resorption sites on the root apex. This newly formed tissue extended from the surface of the root around the apex to the extruded gutta-percha cone to which it was well adapted, forming a bridge between the cone and the root.

Zirconium oxide post and core system for the restoration of an endodontically treated incisor.

Abstract: Due to their enhanced optical properties (eg, translucency, value, chroma), ceramic systems can provide natural aesthetics for restorations placed in the anterior segment. In endodontically treated teeth with stained dentin, however, the use of translucent ceramic materials may be contraindicated unless the underlying discoloration can be masked. This article describes the use of a zirconium oxide post and core system with an all-ceramic crown for the restoration of an endodontically treated anterior tooth. This contemporary system allows optical and mechanical requisites to be resolved simultaneously.

Alteração da temperatura radicular externa durante o preparo para contenção intra-radicular

Abstract: The objective of the present study was to compare the change in temperature on the external surface of the root in vitro during post and core preparation using 4 different techniques. Forty lower single-root premolars instrumented and filled with gutta-percha and stored in 10% formalin were divided into 4 groups according to the technique of gutta-percha removal employed, using heated endodontic pluggers and Peeso, Largo and Gates-Glidden burs. The experiment was performed in a chamber with controlled temperature maintained at about 26°C. For gutta-percha removal from the canals, 2/3 of the root length was calculated and approximately 4 mm of apical filling was left. The temperature of the external surface of the root was measured with a thermo-couple connected to a multimeter and measurements were made in 3 regions: cervical (about 3 mm below the cementum-enamel junction), middle and apical regions of a predetermined measurent. Analysis of variance indicated significant differences (p < 0.01) between regions and techniques. The complementary Tukey test indicated that the heated endodontic pluggers produced the greatest increased in temperature among the three techniques, and the Peeso bur produced the greatest increase in temperature among the burs used. Among regions, the apical one presented the greatest change in temperature for all the techniques evaluated.

Restoration of endodontically treated teeth with posts and cores.

Abstract: This article is a review of the current technique and materials used in the restoration of endodontically treated teeth with post and core materials and procedures. It is intended to aid clinicians in making selections which are appropriate to their individual practices through the evaluation of relevant literature about the restoration of endodontically treated teeth.