Evaluation of the effect of connector size and design on flexural strength of monolithic zirconia fixed dental prosthesis

Abstract

Objectives: Designing a high strength ceramic fixed partial denture with favorable esthetics can be a challenge for clinicians; this study aims to evaluate the effect of connector size and design on fracture resistance of monolithic zirconia fixed dental prosthesis. Materials and methods: Two groups of twenty 3-unit monolithic zirconia (Sirona inCoris TZI, Sirona Dental Systems GmbH) bridges extending from mandibular first premolar to first molar with different connector size (9mm2, 12mm2) were divided into two subgroups with different connector design (round and sharp). The specimens were subjected to 3-point bending test to obtain the fracture bearing load. The results reported using descriptive statistics (mean ± standard deviation). To compare the fracture load in two types of designs and two dimensions of the connectors simultaneously, two-way ANOVA analysis of variance was used. The significance level was considered as p <0.05. Results: The minimum failure load was related to group with 9mm2 connector dimension and sharp embrasure design 1054.4±133.89 N), and the highest mean value belongs to group with 12mm2 connector dimension and rounded embrasure design (1599.8±167.09N). Mann-Whitney U test indicated a significant difference between the mean failure load of the rounded and sharp embrasure designs in 9 mm2 connector dimension (p=0.007). However, the difference was insignificant in 12mm2 connector dimension (p=0.075). Conclusion: Sharp embrasure design is not recommended for high-stress areas with restricted occlusogingival height. Nine mm2 connector dimension for 3-unit monolithic zirconia FDP which is recommended from the manufacturer should be used more cautiously.