RESUMO
(1) Background: The stability of implants plays a significant role in the success of osseointegration. The stability of the connection between the fixture and the abutment is one of the critical factors affecting osseointegration. When restoring multiple, non-parallel, and splinted implants, achieving a passive fit can be complicated and challenging. A new EZ post non-engaging abutment system of the BlueDiamond® (BD) implant allows a wide connection angle while achieving a passive prosthesis fit. This study aimed to confirm the new abutment system's clinical applicability by evaluating its biomechanical characteristics using finite element analysis (FEA). (2) Methods: The implant-supported fixed three-unit dental prostheses model was reproduced for two groups of AnyOne® (AO) and BD implants using FEA. The loading conditions were a preload of 200 N in the first step and loads of 100 N (axial), 100 N (15°), or 30 N (45°) in the second step. (3) Results: The peak Von Mises stress (PVMS) value of the fixture in the BD group was more than twice that in the AO group. In contrast, the PVMS values of the abutment and abutment screws were lower in the BD group than in the AO group. The AO group revealed higher maximal principal stress (MPS) values than that of the BD group in the cortical bone, cancellous bone, and crown. The average stress of the outer surface of the abutment was lower in the AO group than in the BD group. The stress distribution for the inner surface of the fixture confirmed that the BD group displayed a lower stress distribution than the AO group under axial and 15° loads; however, the average stress was 1.5 times higher at the 45° load. The stress values of the entire surface where the cortical and cancellous bone were in contact with the fixture were measured. The AO group showed a higher stress value than the BD group in both cortical and cancellous bone. (4) Conclusions: In the AO group, the PVMS value of the fixture and the stress distribution at the contact surface between the fixture and the abutment were lower than those of the BD group, suggesting that the stability of the fixture would be high. However, due to the high stress in the fastening area of the abutment and abutment screw, the risk of abutment fracture in the AO group is higher than that of the BD group. Therefore, the new EZ post non-engaging abutment of the BD implant can be used without any problems in clinics, similar to the non-engaging abutment of the AO implant, which has been widely used in clinical practice.
RESUMO
STATEMENT OF PROBLEM: Titanium is an alternative tooth restorative material because of a its biocompatibility and mechanical properties. However, there is little information on the marginal accuracy of a complete titanium crown with different margin configurations. PURPOSE: This study examined the effect of fabrication method and margin configuration on the marginal and internal fit of complete titanium crowns. MATERIAL AND METHODS: An acrylic resin maxillary first molar was prepared with shoulder (buccal), chamfer (palatal), and knife edge (proximal) margin configurations. Forty crowns were produced and then divided into 2 groups according to the manufacturing method (casting method or CAD/CAM technique) (n=20). Each crown was luted to the original stone die with zinc phosphate cement. The margin of the crown, center point of the axial wall, and occlusal area were measured with a 3-dimensional measuring microscope. An independent t-test (internal gap) and repeated measures 2-way ANOVA (marginal gap) were used for statistical analysis (α=.05). RESULTS: The mean marginal gap of the cast group was significantly smaller than that of the CAD/CAM group (P<.001). The margin configuration affected the measured marginal discrepancy (P<.001). In both groups, the mean marginal gap of the chamfer and shoulder margin was significantly smaller than that of the knife-edge margin (P<.001). CONCLUSIONS: Castings-produced titanium crowns with a better marginal fit than the CAD/CAM technique. The knife-edge margin exhibited the greatest marginal discrepancy.