Effect of Framework Design on Fracture Resistance in Zirconia 4-unit All-ceramic Fixed Partial Dentures

Abstract

The purpose of this study was to conduct static load-bearing tests on 4-unit Y-TZP all-ceramic fixed partial denture (FPD) frameworks with different cross-sectional areas and forms to evaluate the influence of connector design on fracture load. Each of the central, mesial and distal connectors was prepared with one of 2 different cross-sectional areas and one of 3 different forms (one circular and two oval forms) to give a total of 18 designs. Five frameworks were then prepared for each design, making a total of 90. Each framework was cemented to the test model with glass ionomer cement. Fracture load was measured with a universal testing machine at a cross-head speed of 1.0 mm/min. A three-way ANOVA revealed significant differences in fracture load depending on cross-sectional area, central connector cross-sectional form, or mesial/distal connector cross-sectional form (p<0.01). No interaction was observed, however, between any two connector design elements. The results of a Tukey analysis revealed a significant difference between the two connector cross-sectional areas investigated, with an increase in connector cross-sectional area resulting in an increase in fracture load. Fracture load decreased as the height of the mesial or distal connector decreased. Fracture load was significantly higher in frameworks in which the height of the central connector was greater than that of the distal or mesial connector. In conclusion, these results suggest that sufficient height needs to be maintained in the mesial/distal connector to secure a high fracture load in zirconia 4-unit all-ceramic FPDs. Moreover, even when this is not possible, a high fracture load may still be obtained by making the height of the central connector as great as possible. Furthermore, extending the connector cross-sectional area is effective in increasing fracture load.

Effect of Connector Design on Fracture Resistance in Zirconia-based Fixed Partial Dentures for Upper Anterior Region

“…The physical properties of zirconia frames have been investigated using various types of destruction test 1,15,16,21,32) and finite-element analysis 17,36) . Some studies using the former employed a thermal cycle to simulate aging 1,15) .…”

“…One such ceramic, 5 mass% yttria-stabilized tetragonal zirconia polycrystal (Y-TZP), offers a number of favorable properties, such as greater bending strength and a higher fracture load than conventional ceramics with cores containing aluminum oxide 4) . These properties make Y-TZP a popular choice in the fabrication of fixed partial dentures (FPDs) for the molar region 32) . The superior bending strength and fracture resistance of Y-TZP, in particular, have been responsible for its clinical success, with its application to the fabrication of single crowns and FPDs, for example 25,28,29,34) .…”

“…The larger, the connector, however, the greater its strength 13,16) . Many manufacturers 16,21,32) recommend a cross-sectional area of 7.0 to 9.0 mm 2 for connectors in zirconia FPD frameworks for the upper anterior region designed using the CAD/CAM system. With a narrow FPD connector, mechanical stress is distributed vertically in the lower anterior region.…”

Effect of Three Veneering Techniques on Marginal Accuracy and Fracture Resistance of Zirconia Base Fixed Restoration (In-Vitro Study).

“…Actually high quality, all-ceramic restorations are not easily distinguished from adjacent natural teeth. 13 Among the many ceramic systems that have been developed, Yttria-stabilized polycrystalline tetragonal zirconia has become a common form of dental restoration; mostly because of having good characteristics including esthetics, excellent biocompatibility, low plaque accumulation, and high strength 14 . In addition to esthetics, marginal fit and fracture strength are essential criteria for clinical success.…”

Op kronen en bruggen uitgeoefende krachten en het weerstaan daarvan 2. Mechanische belastbaarheid

“…De vorm van de dwarsdoorsnede, rond of ovaal, had geen invloed. Daarom lijkt het verstandig de hoogte van de dwarsdoorsnede zo groot mogelijk te maken (Takuma et al, 2013). Het belang van de grootte van het oppervlak van de dwarsdoorsnede van de basisstructuur werd bevestigd in een Zweeds laboratoriumonderzoek.…”