A Further Finite Element Stress Analysis of Angled Abutments for an Implant Placed in the Anterior Maxilla

To systematically measure and compare the stress distribution on the bone around an implant in the anterior maxilla using angled abutments by means of finite element analysis, three-dimensional finite element simplified patient-specific models and simplified models were created and analyzed. Systematically varied angled abutments were simulated, with angulation ranging from 0° to 60°. The materials in the current study were assumed to be homogenous, linearly elastic, and isotropic. Force of 100 N was applied to the central node on the top surface of the abutments to simulate the occlusal force. To simulate axial and oblique loading, the angle of loading was 0°, 15°, and 20° to the long axis of implant, respectively. There was the strong resemblance between the response curves for simplified patient-specific models and simplified models. Response curves under oblique loading were similar in both models. With abutments angulation increased, maximum von Mises stress firstly decreased to minimum point and then gradually increased to higher level. From a biomechanical point of view, favorable peri-implant stress levels could be induced by angled abutments under oblique loading if suitable angulation of abutments was selected

Evaluation and Comparison of Different Abutment Level Impression Techniques using All-On-Four Implant Treatment Protocol: An In Vitro study

STATEMENT OF PROBLEM: Passive fit of the prosthesis in the All-On-Four technique is a key factor for its success. To achieve a precise passive fit of an implant supported prosthesis, it is important to reproduce three dimensional relationship of implants and abutments in the cast by using an accurate impression procedure. Splinting or non-splinting, direct or indirect impression techniques and the angulation of inserted implants play an important role in the angular and positional accuracy of the definitive impression. However, limited information is available regarding the accuracy of different abutment level impression techniques using All-On-Four implant treatment protocol. AIM OF THE STUDY: The aim of this study was to compare the accuracy of closed tray and non-splinted open tray abutment level impression techniques for the All-On-Four implant protocol. MATERIALS AND METHODOLOGY: An acrylic edentulous maxillary reference model was fabricated with four implants placed according to the All-On-Four protocol. For two straight anterior implants, two straight transmucosal abutments and for two distally placed posterior implants, 30˚ angled transmucosal abutments were used. A total of 20 impression were made with closed tray (n=10) and non-splinted open tray (n=10) using polyether impression material. A Coordinate Measuring Machine was used to measure the linear (x and y axes) and angular (z axis) measurements for the reference acrylic model and the casts obtained from closed tray and non-splinted open tray groups. The linear and angular displacement values of the casts were compared with the values obtained from the reference acrylic model and were subjected to statistical analyses (p=0.05). RESULTS: There was no significant difference in the linear and rotational discrepancies between the closed tray and the reference acrylic model. There was no significant difference in the linear and rotational discrepancies between the non-splinted open tray and the reference acrylic model. There was statistically significant difference (p=0.019) between the closed tray and non-splinted open tray on comparison of the distance between the reference point and the abutment 4 in y axis. CONCLUSION: Within the limitations of this study, there was no significant difference in the accuracy of the casts obtained from the closed tray and non-splinted open tray abutment level impression techniques with that of the reference acrylic model using All-On-Four protoco