Optical Microscopy Evaluation of the Abutment–Implant Interface in a Morse Taper Connection After Insertion Torque: An In Vitro Study

Abstract

Dental implant rehabilitations have been widely investigated, with initial stability being a determining factor for the success of osseointegration and the longevity of treatment. In this context, Morse taper connections stand out due to their prosthetic stability, ability to minimize micromovements, high mechanical resistance, and preservation of peri-implant bone levels. In addition, this type of connection provides effective sealing of the abutment–implant interface. Thus, the application of different insertion torque values is directly related to the structural integrity of the system, making it essential to investigate their influence on the mechanical aspects of the implant, especially when high torque values are used. This experimental study, with a quantitative approach, evaluated the presence of gaps at the abutment–implant interface of Morse taper connections after the application of a maximum insertion torque of 80 N/cm by means of optical microscopy. In a controlled laboratory environment, twenty Grade IV titanium implants (3.5 mm × 10 mm) were divided into two groups: Group 1 (n = 20), in which implants were mechanically fixed in a vise-type device at 5 mm from the apex, stabilized, and fitted with universal abutments installed with a torque of 20 N/cm; and Group 2 (n = 20), fixed under the same conditions but previously subjected to a maximum insertion torque of 80 N/cm. Subsequently, the corresponding abutments were manually installed with a torque of 20 N/cm. The samples were embedded in epoxy resin, vertically sectioned, and analyzed by optical microscopy to identify gaps and deformities at the abutment–implant interface in six distinct regions (A, B, C, D, E, and F). Measurements were performed using ImageJ software, and the data were statistically analyzed using SPSS software, version 29. The results demonstrated that implants subjected to a prior insertion torque of 80 N/cm before abutment installation showed higher mean deformation values compared to Group 1, with a higher incidence in regions A and D. Statistical analysis confirmed significant differences between the groups, indicating that high torque values negatively impact the abutment–implant interface, increasing the risk of mechanical failures.