In the recent decades, great advances in implantology have been achieved by allowing implant therapy to become a therapeutic solution today not only for total or partial edentulism but also for monoedentulias.
The external hexagon was the first connection system used in implantology, and it was born with Branemark to facilitate the insertion of the abutment, then expanded its functions to become an anti‑rotation mechanism.
It was used later by various implant companies that represented
and interpreted it in various ways, causing various changes either with the height or with the diameter of the hexagon connection.
Furthermore, the tightening screw changed a lot from the point of view of the material, of the diameter, of the number of the turns, of the dimension of the length, and torque application.
In the literature, there are several studies that document the incidence of technical complications of systems equipped with the external hexagon connection with percentages that varies from 6% to 45%.
However, we must not forget the importance of perfect adaptation between implant and hexagon of the abutment.
To try to overcome the biomechanical complications, such as loosening of the connecting screw or the fracture of the abutment or the clamping screw, the major implant companies with external hexagon connection have introduced the use of keys dynamometers that gave to the screw a calculated torque.
This is the subject however; it did not completely eliminate the problem, although it led to a reduction in incidence.
The internal connections showed immediately greater mechanical stability and better stability than external ones.
Dibart et al. tested in vitro three single tooth implant systems with drawings of different connections for anti‑rotational stability, resistance to cyclic fatigue, and torque.
They discovered that the internal hexagon system offered the highest stability of the abutment and a higher resistance to cyclic fatigue than the external hexagon system.
It can generally be said that the internal connection offers more advantages in terms of stability and with prolonged application of lateral forces.
A separate argument between the internal connections deserves the pure conometric connection, which it does not require the presence of screws and where the interface provides a direct joint between the surfaces of the abutment and implant.
In this case, the tolerances of the coupling must be very precise because the transmission of the couple happens by friction, by effectiveness of the system that is closely linked to the material used, to the nature of the surfaces, and to the geometric shape.
Considering that the surfaces are never perfectly smooth, there is microscopic asperity that, thanks to the contact, a cold welding is obtained.
The mechanical stability of this system is ensured by the total elimination of all micromovements at the interface between the components.
Numerous studies have demonstrated the effectiveness and reliability of this system by highlighting a low incidence of clinical complications.
It was noted, thanks to some microscopic examinations, that the discrepancies present in the interface of the components in a conical connection amount to no more than 3 µ, compared with 20–30 µ of average distance between abutment and implant connected with screwed systems and even 70–120 µ of average discrepancy between screw thread and implant.
It seems that this type of system is also very effective in countering the phenomenon of the pumping effect that is present in screwed systems.
This conometric connection and the monophasic implants constitute an excellent barrier to bacterial penetration.
Whereas the size of a bacterium can range from 1 to 6 µ and that, as mentioned above, the gap interfacing of this system ranges from 1 to 3 µ, bacterial percolation through the coupling of the implant components becomes a very difficult phenomenon to be realized.
Some studies have shown that the conometric connection prevents the passage of fluids, and therefore also the bacterial colonization.
All this, translated into clinical terms, would effectively contribute to the reduction of implant failures due to infectious causes.
The aim of this study is to present a series of cases of implants of the frontal area (mostly lateral incisors) rehabilitated with monophasic implants and with implants with the conometric connection.
