Purpose: to summarize the results of research related to the ferrule effect and published in peer-reviewed journals listed in PubMed
Ferrule effect is defined as a ‘‘360 metal collar of the crown surrounding the parallel walls of the dentine extending coronally to the shoulder of the preparation’’.
•A literature search was conducted in PubMed from 2000 to 2011.
• All articles were categorized into 3 main categories: laboratory studies, computer simulation (finite element analysis), and clinical trials. Finite element analysis (FEA) is the method that evaluates stress distribution within complex structures and provides results without variation
Most highlighted Results:
–Ferrule Height/Ferrule Design:
-Presence of ferrule has a positive effect on fracture resistance of RCT teeth
-More successful prognosis expected if healthy dentin extending 1.5 -2 mm coronal to the margin of the crown is provided circumferentially
-Teeth with a non-uniform ferrule length were still more fracture resistant then teeth without a ferrule
–Type of Post and Core System and Final Restoration:
-In the presence of a 2-mm-high dentine ferrule; Heydecke et al found no statistically significant differences in survival rates, fracture loads, and modes of failure among titanium post and composite core, zirconia post and ceramic core, zirconia post and composite core, and cast gold post and core system
-Providing an adequate ferrule lowers the impact of the post and core system, luting agents, and the final restoration on the performance of RCT teeth
-Including a ferrule in the preparation design could possibly lead to more favorable fracture patterns. Teeth with a ferrule underwent a mostly oblique fracture, whereas in teeth without a ferrule vertical root fracture
-In severely damaged teeth, in order to provide space for a ferrule, orthodontic extrusion should be considered rather than surgical crown lengthening