Comparison of the Flexural Strength of Four Core Built up Materials

The aim of this study is to compare the flexural strength of 4 commonly used core build up materials in clinics. Four core built up materials, a cermet cement (ketac silver), a light cure composite, conventional silver amalgam (control group) and zirconomer (zirconia reinforced GIC) were used and were divided into Group A, B and C and D respectively. The root canal of 90 extracted mandibular molars with similar anatomy and morphology were selected. Highest flexural strength was shown by Group A followed by group C, group B and then group D.

The effect of thermocycling on fracture toughness and hardness of different core build up materials.

Introduction: Core build up materials are routinely used to restore grossly decayed teeth and in the oral environment they are subjected to changes in the temperature due to consumption of hot and cold food. Aims: The purpose of this study was to determine the effect of thermocycling on the fracture toughness and hardness of 5 core build up materials. Materials and Methods: Fifteen specimens were prepared for each of the following materials: DPI alloy, Miracle‑mix, Vitremer, Fuji II LC and Photocore. American Standard for Testing Materials guidelines were used for the preparation of single‑edge notch, bar‑shaped specimens. Ten specimens of each material were thermocycled for 2000 cycles and the other 5 specimens were not thermocycled (non‑thermocycled group). All specimens were subjected to 3-point bending in a universal testing machine. The load at fracture was recorded and the fracture toughness (KIC) was calculated. Vickers hardness test was conducted on the thermocycled and non‑thermocycled group specimens. Results: Photocore had the highest mean KIC in both thermocycled and non‑thermocycled groups. Miracle‑mix demonstrated the lowest mean fracture toughness (KIC) for both thermocycled and non‑thermocycled groups. By applying Mann Whitney ‘U’ test the Vickers hardness value in all materials used in the study is highly superior in non‑thermocycled group as compared to thermocycled group (P < 0.01). Non‑thermocycled Photocore showed highest hardness values of 87.93. Vitremer had lowest hardness of 40.48 in thermocycled group. Conclusion: Thermocycling process negatively affected the fracture toughness and hardness of the core build‑up materials.

A study on the material properties of various composite resins for core build-up / 대한치과보존학회지

The purposes of this study were to estimate the material properties of the recently developed domestic composite resins for core filling material (Chemical, Dual A, Dual B; Vericom, Korea) and to compare them with other marketed foreign products (CorePaste, Den-Mat, USA; Ti-Core, Essential Dental Systems, USA; Support, SCI-Pharm, USA). Six assessments were made; working time, setting time, depth of polymerization, flexural strength, bonding strength, and marginal leakage. All items were compared to ISO standards. All domestic products satisfied the minimum requirements from ISO standards (working time: above 90 seconds, setting time: within 5 minutes), and showed significantly higher flexural strength than Core Paste. Dual A and B could, especially, reduce the setting time to 60 seconds when cured with 600 mW/cm2 light intensity. All experimental materials showed 6 mm depth of polymerization. Bond strengths of Ti-Core and Dual B materials were significantly higher than the other materials. Furthermore, three domestic products and Ti-Core could reduce the microleakage effectively.

A study on the material properties of various composite resins for core build-up / 대한치과보존학회지

The purposes of this study were to estimate the material properties of the recently developed domestic composite resins for core filling material (Chemical, Dual A, Dual B; Vericom, Korea) and to compare them with other marketed foreign products (CorePaste, Den-Mat, USA; Ti-Core, Essential Dental Systems, USA; Support, SCI-Pharm, USA). Six assessments were made; working time, setting time, depth of polymerization, flexural strength, bonding strength, and marginal leakage. All items were compared to ISO standards. All domestic products satisfied the minimum requirements from ISO standards (working time: above 90 seconds, setting time: within 5 minutes), and showed significantly higher flexural strength than Core Paste. Dual A and B could, especially, reduce the setting time to 60 seconds when cured with 600 mW/cm2 light intensity. All experimental materials showed 6 mm depth of polymerization. Bond strengths of Ti-Core and Dual B materials were significantly higher than the other materials. Furthermore, three domestic products and Ti-Core could reduce the microleakage effectively.

Evaluation of the fracture resistance of all-ceramic zirconia posts by 3 different methods / 대한치과보철학회지

STATEMENT OF THE PROBLEM: All-ceramic post-and-core restorations offer a number of advantages compared with systems that use metal build-ups. In certain clinical cases, however, fractures at the joint between the post and core build-up have been reported. PURPOSE: The objective, therefore, is to improve the joint between the post and the core build-up. MATERIAL AND METHODS: Three different methods were used to prepare all-ceramic post-andcore restorations; pressing IPS Empress core build-ups to CosmoPost zirconia posts, cementing IPS Empress core build-ups to CosmoPost zirconia posts and Celay-milling of zirconia blanks. A series of ten restorations was prepared for each of the three methods. The post-and-core complexes were tested to failure with the load applied perpendicular to the post axis. The load and deflection at fracture were recorded. RESULTS: The highest breaking load and highest deflection were recorded for the cementing technique with values of 25.3 N and 394 micrometer, respectively. The corresponding values for the pressed core build-ups and the milled zirconia core build-ups were 22 N and 301 micrometer, and 13 N and 160 micrometer, respectively. All the differences are statistically significant (p=0.05). Regarding the load-dependence of the deflection, the cemented core build-ups again demonstrated the highest value with 15.5 micrometer/N. The difference in the values of 13.6 micrometer/N and 13 micrometer/N recorded for the pressed-on and milled core build-ups, respectively, were statistically insignificant. CONCLUSION: In regard to the high fracture resistance of zirconia post, adhesive cementing the core build-up to the post offers a viable alternative to the conventional pressing technique. The elastic bond between the rigid high-strength zirconia post and the core build-up presents an additional advantage.