Bacterial infiltration and detorque at the implant abutment morse taper interface after masticatory simulation

Abstract

This study evaluated the bacterial infiltration and the detorque of indexed and non-indexed abutments of Morse taper implants (MTI) after mechanical cycling (MC). 40 MTI were distributed into four groups: IIA (indexed implant abutments); NIIA (non-indexed implant abutments); IIAMC (indexed implant abutments submitted to MC); NIIAMC (non-indexed implant abutments submitted to MC), which were carried out under one million 5 Hz frequency and 3 Bar pressure. After mechanical cycling, all groups were immersed in a bacterial solution in Brain Heart Infusion Agar. After detorque, the bacteria infiltration was evaluated by counting the colony-forming units. For the bacterial infiltration, analysis was applied to the Kruskal–Wallis test (p = 0.0176) followed by Dunn’s test. For the detorque analysis, the two-way repeated-measures ANOVA was applied, followed by the Tukey’s test (p < 0.0001). Bacteria infiltration was highly observed in NIIA (p = 0.0027) and were absent in IIAMC and NIIAMC. The detorque values for IIA (19.96Ncm ± 0.19Ncm), NIIA (19.90Ncm ± 0.83Ncm), and NIIAMC (19.51Ncm ± 0,69Ncm) were similar and remained close to the initial value, while IIAMC (55.2Ncm ± 2.36Ncm) showed an extremely significant torque value increase (p < 0.0001). The mechanical cycling resulted in mechanical sealing of the implant-abutment interface, preventing bacterial infiltration in the indexed and non-indexed specimens, and increasing the detorque strength in the group of indexed abutments.

Does the index in Morse taper connection affect the abutment stability? An in vitro experimental study

“…After the preload during the installation of the abutments, which is done by applying a torque determined by the manufacturer, these sets should remain stable during the application of masticatory loads. However, as described in previous studies [8], in most systems (IA sets) there is accommodation of the parts during the application of loads that can change the initial torque applied and, consequently, change the stability of the sets. In addition, non-tapered IA sets (external and internal hexagon connections) may exhibit micromovements during the application of forces [9].…”

“…On the other hand, other studies evaluated whether the inclusion of the index could affect bacterial sealing and the resistance of the IA sets, since it results in a decrease in the contact area in the conical portion of the implant/abutment. Based on methodologies for evaluating bacterial microleakage and resistance to fracture, the authors observed that the presence of the index did not compromise the performance of MT implants [8,9,11].…”