Views: 286 Author: Kaylee Publish Time: 2023-11-29 Origin: Site
Before delving into the advantages and causes of the surge in popularity of multi-unit screw-retained prosthesis systems, it is imperative to comprehend the complexity of the patient's clinical picture and the reasons why attempting to accomplish the restoration in a different manner would be highly challenging. The patient came in for a zirconium bridge prosthesis, which was placed on the extracted portions of his own teeth. Plaque and darkening at the base of the crowns are visible in the figure below.
The experts already concluded that there probably wouldn't be anything to work with in the front tooth area based on this image. It will be necessary to extract the tooth remnants and place implants. Their fears were realised when the bridge was taken down; take a look at the photo below.
The posterior teeth were preserved since they could be treated and restored without needing to be extracted, while the anterior teeth were extracted. Implant installation was likewise a difficult process. It is frequently required to insert abutments at an angle in the upper jaw. This instance was not unique. After the placement of six implants, the patient was ready to have a digital scan of their jaws taken, which included a measurement of the angles at which the implants deviated from the occlusal plane and the location of the implants' remaining teeth. Remember that an intraoral scanner is used in CAD/CAM systems to create an electronic 3D file in place of a traditional impression. Use of unique caps known as scan markers allows for the precise location and angles of deviation of the implants to be indicated.
Six scan markers are fixed: five at the level of multi-unit abutments that have already been fitted, and one at the level of the implant. This is because selecting an abutment with an implant installation angle this great requires careful consideration.
We were uncertain about the type of abutment to select during the scanning phase. You will have a buccal bulge if you select a D-type angled abutment. Food debris and plaque will collect in the area of the large buccal bulge, and there's a good chance that the soft tissues surrounding it will become inflamed.
The second option involved creating a bridge using a straight abutment, but because of the extreme deviation, it was uncertain whether the bridge could be made correctly because the machine used to mill zirconia prostheses has a maximum deviation of 30°, which might not be sufficient to create a part that is one piece.
Utilising a 3D printer to create PFM metal pieces was an additional choice. Maybe this would be of assistance, however because we have made the decision to create a zirconia prosthesis, we must be certain of the correct abutment type before sending the part to be fabricated.
As a result, it was decided to place a single scanning marker at the implant level and send the data collected to the laboratory of the dental technician. There, the prosthesis can be modelled by choosing various abutments from the electronic library, and the software will instantly indicate if using the chosen abutment can lead to the prosthesis being manufactured. The angled abutment can be slightly moved to and fro by the dental technician to check its position and suitability for the bridge.
Then, why not place every scan marker at the implant level and choose abutments according to the findings?
There are six possible locations for each angled abutment in the implant. It is challenging to get the ideal relative position when dealing with two abutments. It is nearly impossible to decide which of the four angled abutments and one straight abutment is the best in this situation. It is comparable to selecting a combination lock code. The bridge that was created in the lab will not function if at least one abutment is installed improperly, and you are unable to identify which abutment is flawed.
The chosen multi-unit abutments' sleeves are visible in the picture below. Focus on the region to the left, which is where tooth number fourteen should be. The V-type multi-unit, which has a shorter sleeve and a considerably smaller taper than the D-type, was selected since there is not enough room.
At the multi-unit level, the doctor took an electronic impression and quickly positioned the appropriate MUA. As you can see, a straight multi-unit abutment was chosen at this point.
In this case, a straight multi-unit with a modest taper is ideal because it prevents buccal bulging and the screw shaft channel from protruding into the denture's anterior plane. Furthermore, since the prosthesis and the base of the abutment at the edge of the soft tissues are hidden, everything looks good.
A computer model of the envisioned prosthesis can be seen in the picture below. We observe how the screw shafts emerge to secure the prosthesis, which is a fantastic outcome.
We can now clearly see that the choice to use a scan abutment placed at the implant's level—where the implant has an excessive angle of deviation—was the right one. It was not necessary to create two prints with distinct settings. A dental technician can select the best solution because there is sufficient information available. Often, the doctor can handle difficult problems without having to go into great detail.
The most important thing is to give the dental technician adequate knowledge. Only in the CAD/CAM era of digital dentistry was this feasible.
The utilisation of three different kinds of multi-unit abutments in this clinical scenario makes it intriguing.
1. Angular MUA: This lets you make up for the implant's angle of deviation, which happens a lot when implants are positioned in the upper jaw. Additionally, there are straight multi-unit abutments that come with an accessory set with the same cone. They can be fitted with the same sleeves and fastening screws as the ones on the corners. When taking digital impressions, the same scanning abutments are utilised. This is MUA D-type if you want to utilise one set of accessories for both angled and straight abutments. Four angled multi-unit abutments were positioned in this instance.
2.Direct MUA D-type, which we described above. There are multiple types of sleeves for him. In this instance, we opted for a shorter sleeve to avoid creating a bulge on the cheek's side where the implant with the biggest deviation is positioned. All of the many kinds of sleeves used in this restoration are shown in the image below.
3. A slight taper was used to install a straight, multi-unit V-type abutment in the 14 tooth region. When there is limited room, these abutments are utilised because they make restoration work go more smoothly. The crown will not necessarily be linked to the abutment directly if the taper is smaller. There is a sleeve and screw fixation here as well, however because of the sleeve's significantly reduced height, the prosthesis's body will have more zirconium and less void while still providing adequate strength. The MUA V-type was selected for this reason.
Thus, we employed every multi-unit option available to us in a single clinical situation. We chose the final abutment to be placed by the dental technician after installing the majority of the abutments all at once and taking one digital impression. The programme makes it simple for the dental technician to move between D-type and V-type. A distinct publication regarding the CAD/CAM system will be produced by us.
In summary, a number of requirements need to be satisfied for a dentition restoration of the highest calibre:
1. Lack of sinuses, other openings, and buccal bulges, which could collect food particles.
2. Screw shafts shouldn't extend past the prosthesis's exterior.
3. The lower portion of the prosthesis and the edges of soft tissues shouldn't show any titanium components. especially while grinning at the bottom.
