Implant-abutment System Research Articles

Fatigue Reliability of 3 Single-Unit Implant-Abutment Designs

Because the mechanical behavior of the implant-abutment system is critical for the longevity of implant-supported reconstructions, this study evaluated the fatigue reliability of different implant-abutment systems used as single-unit crowns and their failure modes. Sixty-three Ti-6Al-4V implants were divided in 3 groups: Replace Select (RS); IC-IMP Osseotite; and Unitite were restored with their respective abutments. Anatomically correct central incisor metal crowns were cemented and subjected to separate single load to failure tests and step-stress accelerated life testing (n = 18). A master Weibull curve and reliability for a mission of 50,000 cycles at 200 N were calculated. Polarized-light and scanning electron microscopes were used for failure analyses. The load at failure mean values during step-stress accelerated life testing were 348.14 N for RS, 324.07 N for Osseotite, and 321.29 N for the Unitite systems. No differences in reliability levels were detected between systems, and only the RS system mechanical failures were shown to be accelerated by damage accumulation. Failure modes differed between systems. The 3 evaluated systems did not present significantly different reliability; however, failure modes were different.

Impact Fracture Resistance of Two Titanium‐Abutment Systems Versus a Single‐Piece Ceramic Implant

The number of patients with oral implants has increased significantly. However, the literature addressing the effect of impact force on titanium and/or ceramic implants is inconclusive. This study sought to determine the fracture resistance to impact load of titanium and ceramic endosseous oral implants. Endosseous oral implants were vertically positioned in two different mounting media: brass and a bone-simulation material. The implant configurations tested included an experimental one-piece Y-TZP implant and a commercially available titanium implant (external hex) with both titanium and zirconia abutments. The specimens were subjected to an impact load using a pendulum impact tester with tup weights varying from 0.9 to 4.5 kg delivered at a radius of 40.64 mm. Loads were delivered to the abutment at a point 4.27 mm above the implant fixture and block junction. Statistical differences (p < .05) were established using the F-test for variances and, when different, t-test assuming unequal variances. For implants clamped in brass, the titanium implant with titanium abutment required the greatest energy to fracture the implant-abutment system (only the abutment screw failed). The ceramic implant and ceramic abutment on titanium implant presented the lowest fracture energy (p < .01). No significant differences were observed when different systems were inserted into the foam blocks of the bone substitute (p > .25). This investigation showed that the fracture energy of two titanium-abutment systems versus a single-piece Y-TZP implant in foam blocks simulating bone elastic modulus was not different, and that differences occurred when the embedding material elastic modulus was increased an order of magnitude.

The influence of platform switching on the biomechanical aspects of the implant-abutment system. A three dimensional finite element study

To evaluate the biomechanical scenario of platform switching geometric implant-abutment configuration relative to standard configurations by means of finite element analysis. A 3D Finite Element Analysis (FEA) was performed on 3 different implant-abutment configurations: a 3.8 mm implant with a matching diameter abutment (Standard Control Design, SCD), a 5.5 mm implant with matching diameter abutment (Wider Control Design, WCD), and a 5.5mm implant with a 3.8 mm abutment (Experimental Design, ED). All the different experimental groups were discretized to over 60000 elements and 100000 nodes, and 130N vertical (axial) and 90N horizontal loads were applied on the coronal portion of the abutment. Von Mises stresses were evaluated and maximum and minimum values were acquired for each implant-abutment configuration. The load-induced Von Mises stress (maximum to minumum ranges) on the implant ranged from 150 MPa to 58 Pa (SCD); 45 MPa to 55 Pa (WCD); 190 MPa to 64 Pa (ED). The Von Mises stress on the abutment ranged from 150 MPa to 52 MPa (SCD); 70 MPa to 55 MPa (WCD), and 85 MPa to 42 MPa respectively (ED). The maximum stresses transmitted from the implant-abutment system to the cortical and trabecular bone were 67 Pa and 52 MPa (SCD); 54 Pa and 27 MPa (WCD); 64 Pa and 42 MPa (ED), respectively. When the implant body was evaluated for stresses, a substantial decrease in their levels were observed at the threaded implant region due to the diametral mismatch between implant and abutment for the ED configuration. The platform switching configuration led to not only to a relative decrease in stress levels compared to narrow and wide standard configurations, but also to a notable stress field shift from bone towards the implant system, potentially resulting in lower crestal bone overloading.

Fatigue Characteristics of Five Types of Implant-Abutment Joint Designs

This study evaluates the fatigue limits for five implant-abutment combinations. Each implant-abutment system was tightened with a closing torque of 32 N-cm. The test specimen was loaded at an inclination of 30 degrees with respect to the loading axis after fixing it 11 mm away from the fixed point. A cyclic compression load was applied at loading cycles of 10 Hz using a hydraulic dynamic testing machine (Model 8516, Instron, USA). The highest and lowest mean static strength was observed in the EXZRTS (1772.2 N) and INTIWS (893.8 N), respectively. The fatigue limits that guarantee a life of 5×106 cycles ranged from 300 N to 800 N. The mean static strength of the external hex type was higher than that of the internal type. However, the fatigue strength of the internal type was higher than that of the external hex type. The fatigue strength of the external hex type with a zirconia abutment was higher than that with the titanium abutment. Fatigue fracture of the zirconia abutment occurred after crack propagation by chipping in the contact position of the margin.

Simulation of Impact Test for Determining “Health” of Percutaneous Bone Anchored Implants

There is an ongoing requirement for a clinically relevant, noninvasive technique to monitor the integrity of percutaneous implants used for dental restorations, bone-anchored hearing aids, and to retain extra-oral prostheses (ear, eye, nose, etc). Because of the limitations of conventional diagnostic techniques (CT, MRI), mechanical techniques that measure the dynamic response of the implant-abutment system are being developed. This paper documents a finite element analysis that simulates a transient response to mechanical impact testing using contact elements. The detailed model allows for a specific interface between the implant and bone and characterizes potential clinical situations including loss of bone margin height, loss of osseointegration, and development of a soft connective tissue layer at the bone-implant interface. The results also show that the expected difference in interface stiffness between soft connective tissue and osseointegrated bone will cause easily measurable changes in the response of the implant/abutment system. With respect to the loss of bone margin height, changes in the order of 0.2 mm should be detectable, suggesting that this technique is at least as sensitive as radiography. A partial loss of osseointegration, while not being as readily evident as a bone margin loss, would still be detectable for losses as small as 0.5 mm.

Advantageous uses of new computerized custom milled abutments in restoring endosseous implants

Golden criteria of an implant abutment system would be that it is a machined milled, custom made, made of titanium, it accounts for poor angulation and limited interocclusal space. It also should provide ease of orientation during transfer in and out the patient's mouth, and it should have individualized resemblance of the prepared tooth form for the replaced tooth to provide optimal esthetics, healing, and emergence profile. Only one abutment system that has been introduced recently provides all of these criteria. This abutment system would be the computerized custom milled titanium abutment.