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