Fracture strength between different connector designs of zirconia core for posterior fixed partial dentures manufactured with CAD/CAM system / 대한치과보철학회지

Statements of problem: Zirconia core is used for posterior fixed partial dentures because it's good mechanical properties. Stress is concentrated on connectors in fixed partial dentures, so the proper design of connector areas is needed for adequate mechanical long-term properties of any prosthesis. The area of connector is critical, but tooth size and surrounding soft tissue limit the connector design. PURPOSE: The purpose of this study is to compare fracture strengths between different connector designs of zirconia core for posterior fixed partial dentures manufactured with CAD/CAM system and determining the optimal connector design satisfying strength and hygiene. MATERIAL AND METHOD: The following four groups of 40 posterior fixed partial denture specimens(each group 10) were fabricated as followed; group 1, vertical height of connector is 3mm(control group, all groups have the same condition); group 2, lingual vertical 1mm reinforcement on connector; group 3, lingual vertical 2mm reinforcing on connector and group 4, lingual vertical 3mm reinforcing on connector. Specimens were subjected to compressive loading on the central fossa of pontic by instron. SEM was used to identify the initial crack and characterize the fracture mode. RESULTS: The results were as follows: 1. The mean fracture load of the non-lingual reinforcing group was 1212N and the lingual vertical 1mm reinforcing group was 1510N, the lingual vertical 2mm reinforcing group was 1882N, the lingual vertical 3mm reinforcing group was 1980N. 2. The reinforcing groups were statistically significant compared to non-reinforcing groups(P0.05) 4. Fractures were initiated in gingival embrasures of connectors and processed to the loading site. CONCLUSION: In this study, lingual reinforcement of connector for improved strength of zirconia based fixed partial denture is nessasary. And long-term study for clinical application is required.

Fracture strength between different connector designs of zirconia core for posterior fixed partial dentures manufactured with CAD/CAM system / 대한치과보철학회지

Statements of problem: Zirconia core is used for posterior fixed partial dentures because it's good mechanical properties. Stress is concentrated on connectors in fixed partial dentures, so the proper design of connector areas is needed for adequate mechanical long-term properties of any prosthesis. The area of connector is critical, but tooth size and surrounding soft tissue limit the connector design. PURPOSE: The purpose of this study is to compare fracture strengths between different connector designs of zirconia core for posterior fixed partial dentures manufactured with CAD/CAM system and determining the optimal connector design satisfying strength and hygiene. MATERIAL AND METHOD: The following four groups of 40 posterior fixed partial denture specimens(each group 10) were fabricated as followed; group 1, vertical height of connector is 3mm(control group, all groups have the same condition); group 2, lingual vertical 1mm reinforcement on connector; group 3, lingual vertical 2mm reinforcing on connector and group 4, lingual vertical 3mm reinforcing on connector. Specimens were subjected to compressive loading on the central fossa of pontic by instron. SEM was used to identify the initial crack and characterize the fracture mode. RESULTS: The results were as follows: 1. The mean fracture load of the non-lingual reinforcing group was 1212N and the lingual vertical 1mm reinforcing group was 1510N, the lingual vertical 2mm reinforcing group was 1882N, the lingual vertical 3mm reinforcing group was 1980N. 2. The reinforcing groups were statistically significant compared to non-reinforcing groups(P0.05) 4. Fractures were initiated in gingival embrasures of connectors and processed to the loading site. CONCLUSION: In this study, lingual reinforcement of connector for improved strength of zirconia based fixed partial denture is nessasary. And long-term study for clinical application is required.

A study on the stress distribution of posterior fixed partial denture with various all-ceramic systems / 대한치과보철학회지

PURPOSE: The purpose of this study was to analyze stress distribution of all ceramic posterior fixed partial denture using a three dimensional finite element method. MATERIAL AND METHOD: A three dimensional finite element model was created to demonstrate all-ceramic posterior fixed partial denture and then this computer model measured the stress distribution of the all ceramic bridges which has a ceramic core materials such as Zirconia, IPS Empress 2, In-Ceram zirconia, Metal-Ceramic. Also the stress distribution was examined according to loading sites when force was applied to sites such as the central area of second premolar, the mesial connector of pontic, the central fossa of pontic, the distal connector of pontic, and the central fossa of second molar. RESULTS: 1. In all the materials of the core in this study, von Mises stress indicated that the stress increased as force was applied to loaded sites, just at those points, on the connector, and the margin in the area adjacent to the connectors. 2. The maximum principal stress was much higher in the lower part of the connectors than in any other region. 3. As the load was applied to the different locations, the research showed a consistent increase of stress in the lower connectors. The maximum value of the von Mises stress was two or three times greater when the load was applied directly to the connectors rather than indirectly through another stressed region. 4. In the case of In-Ceram zirconia, the stress in lower connectors was the highest of all the reference points, the stress showed 75% of all the maximum stress. Ziconia showed 72%, Metal-Ceramic 67% and IPS Empress 2 50%. 5. In the case of Ziconia, the stress was well dispersed in each reference point that the stress differences were smaller when compared to In-Cream ziconia.