Views: 285 Author: Kaylee Publish Time: 2023-12-25 Origin: Site
When an abutment screw fractures, it usually happens to the head rather than the shank or body.Without a doubt, getting rid of the leftover piece is essential to using the implant fixture in the future. Kreissl et al. evaluated implant-supported fixed-bridge restorations over a five-year period and reported a 3.9 percent incidence of abutment screw fracture and a 6.7 percent incidence of screw loosening.The reason for using a fixed-bridge, fixed-hybrid, or fixed-detachable restoration is that a loose abutment screw at a single abutment may not be clinically noticeable for a long time.
What then is the most typical cause of screw fractures? Undetected screw loosening is the solution.With today's dental implants, screw loosening might result from the following causes:
1. Contact between the neighboring alveolar bone and the abutment when a torque wrench is used to apply a predetermined force.
2. The torque wrench could be unreliable, causing torque readings that are either below or over the suggested ranges.
3. Not having a torque wrench on hand for the abutment screw tightening.
4. A substructure that joins two or more implants but doesn't have a "passive fit."
With an externally hexed platform design, it is assumed that abutment screw fractures are more prevalent and that it will be simpler to remove the remaining fragment. Where the abutment may have broken inside the implant fixture itself, several of the internal connections have significantly more surface area available for close contact.
The methods are presented in ascending order of difficulty. Consider the methods in terms of how they rely on the depth at which the shattered end or residual piece of the abutment screw is situated within the dental implant fixture.
In order to tease the remnant of the screw in a direction that is counterclockwise according to the measurements, the sharp and pointed end of the abutment screw is typically utilized. When it comes to getting things started, using a scaler is a terrific method to get things moving, and it is frequently all that is required to get things working. Because of the typical fracture pattern of abutment screws, it is conceivable for a metal shard or an uneven edge to become stuck between the threads of the implant fixture. This might lead to the remaining section becoming clogged, which would be a problem. Following this, the remaining abutment screw component will be vibrated using an ultrasonic scaler, which is the next step in the process. One of the methods that has been described in the literature is the utilization of a handpiece to create a few indents with a round bur. This serves the purpose of providing a visible reference point as well as a "edge" that can be grabbed with the scaler. Among the many approaches that have been discussed, this one is one of them.
According to the research of Dr. Gordon J. Christensen, it is feasible for a ½ round bur that is rotating in a handpiece to come into touch with the outer edge of the remaining abutment screw. This is a possibility that can occur. A spin in the opposite direction of the clock would be produced as a consequence of this interaction, which would lead to the remaining fragment becoming more free. When one looks down the shank of the bur to the terminal working end of the round bur, this is something that can be seen.There is an alternative strategy that entails making a horizontal cut in the shank of the remaining abutment screw, and then removing the fragment using a small straight blade driver. This is the backup plan. When working with a handpiece in an area that is extremely limited, there is a possibility of causing damage to the structural components of the dental implant fixture that are located on the inside. Just one illustration of the various dangers that could arise is presented below.
The fractured abutment screw can be mechanically removed using this mechanism, which is provided in the form of a kit and can be used in conjunction with a handpiece. This mechanism offers an extra method for removing the screw. There is no question that the various kits are distinct from one another in terms of the manner in which the broken component of the abutment screw is retrieved and the manner in which the dental implant connection for the abutment is protected. Because of this, the abutment connection can be either exterior (usually in the shape of a hexagon) or internal (it can be conical, hexed, or hybrid). Both of these configurations are possibilities. To center the reverse-tapping bur over the center of the abutment screw, it is feasible to adjust the internal aspect of an impression abutment by employing a novel technique that was published by Yoon et al. This technique allows for the modification of the internal aspect of the impression abutment. It is possible to achieve this while simultaneously safeguarding the dental implant fixture's internal retentive and anti-rotational properties.
Determine the kind of dental implant to assist determine the expected outcome. According to a study by Kim et al., as long as the internal threads of the dental implant fixture are engaged by three and a half threads, short abutment screws offer sufficient resistance to occlusal stresses.4Take a look at Figure 1's many thread designs.
It might be simpler to remove a fragment with fewer threads when an abutment screw fractures following what is probably a period of deformation (screw loosening before screw fracture). Another subtlety that might provide a problem has to do with the abutment screw's thread pattern. As an illustration, consider the Ankylos implant system with a laser-welded interface, in which the abutment screw's shank is expanded with threads after it is put into the abutment. The issue of extracting the threads that have broken free of the abutment screw is unique.
Examine the state of the adjacent teeth or adjacent dental implants in addition to the alveolar bone directly around the dental implant. To assist you decide how much time you are willing to spend removing the abutment screw fragment, consider the abutment screw's design features as well as the state of the dental implant.