Effect of ferrule placement on static load failure of teeth restored with different post-core systems

Objective:To study the effect of different post and cores systems on resistance to fracture ofthe remaining dental tissue of endodontically treated teeth and analyze the relationship of the combined effect of crown lengthening and placement of a ferrule and teeths’ failure resistance.Methods: Forty recently extracted human single rooted lower premolars were cut off from CEJ and randomly divided into group A(Ni-Cr posts and cores without ferrule),group B(Ni-Cr posts and cores with ferrule),group C(fiber glass posts and composite resin cores without ferrule) and group D(fiber glass posts and composite resin cores with ferrule).All teeth were restored with full crown casts.Each specimen was embedded in acrylic resin and secured in a universal material testing machine.A speed of 1mm/min was applied to them until fracture occurred.Results: Group A has the highest fracture resistance with the value of 3.0369±0.3388KN while group D has the lowest fracture resistance with the value of 2.0188 ±0.3864KN.The differences were statistically significant among A and C groups,A and B groups,and C and D groups.(P 0.05).Repairable fractures more often happened to group C and D;whereas un-repairable fractures were more happened to group A and B(P 0.05).Conclusion: When teeth are subjected to CEJ level,the combination of crown lengthening and placement of a ferrule can decrease the teeths’ failure resistance.Traditional cast post and core system is more suitable for the teeth without ferrule in this test.