Views: 287 Author: Kaylee Publish Time: 2023-10-11 Origin: Site
For the dental practitioner, providing an implant-supported restoration can be very difficult, particularly in the case of the atrophic maxilla. Numerous factors, including the slope of the implant axis, facial shape, and atrophy of the remaining ridge, are responsible for this. If the access channel is positioned too buccally or lingually, fabricating an implant restoration in this situation would often necessitate the use of extra components to achieve an angulation shift or the use of a cement-retained restoration. Because screw-retained restorations are easier to remove and have less retrievability than cement retention, they are recommended wherever possible. It has been discovered that clinical and radiographic indicators of peri-implant illness are connected with the presence of residual cement surrounding implant restorations. However, using extra prosthetic components to alter the angulation while preserving the screw-retained design will increase complexity at the implant-prosthetic interface and result in higher expenditures.
Under such conditions, an alternative method of maintaining a screw-retained prosthetic restoration was made possible by the recent creation of an angulated screw channel abutment.By using a screw-retained implant restoration instead of a cemented retained implant repair, we can prevent the biological effects of leftover cement and obtain more predictable retention and retrievability.
According to a study by Friberg and Ahmadzai on the restoration of parallel-walled implants with conical connections, the employment of an angulated screw channel system can result in a restoration survival rate of 100% after a year of function and an implant survival rate of up to 98%. In both the Pol et al. trial and the Friberg and Ahmadzai study, there was a little amount of peri-implant bone loss—0.16 mm in the former and 0.41 mm in the latter. These findings are consistent with previous research on comparable implant designs that did not employ angulated screw channels.
In addition, Pol et al.'s survey examined the overall, functional, and aesthetic satisfaction of patients with implants restored with angulated screw channels. According to their survey, implant restorations using angulated screw channel solutions resulted in an overall level of satisfaction that was comparable to other studies. Furthermore, it has not been discovered that angulated screw channel systems lead to more technical difficulties (Anitua et al. 2020), and the functional and aesthetic outcomes are similar to those of cement-retained crowns.
There are two primary components to the angulated screw channel concept:
1. Hexalobular-shaped screw head
2. A unique screwdriver with 360 degrees of rotational freedom that may contact the screw at any angle between 0 and 28 degrees
There are two options for the angulated screw channel system: a Ti-base and a castable abutment. The chimney pivots on the semi-spherical base of a castable abutment, which is made up of two sections joined by an elbow that functions as a joint. The fixation screw is special in that it may be tightened off-axis using a screwdriver. The final prosthetic restoration can be cemented onto a prefabricated Ti-base, which can support the screw head of an angulated screw channel Ti-base. In certain systems, the prosthetic restoration is friction-fitted onto a Ti-base, and the screw head is positioned on the interior surface of the restoration. The screw head can typically be engaged by the screwdriver at any angle up to 30 degrees. The screw's final torque is typically between 20 and 35 Ncm.
The manufacturer's advised degrees of variation for off-axis inclination are 25–30 degrees.
2. Proper planning of treatments
3. Helpful lab personnel
1. Off-axis correction larger than the guidelines provided by the manufacturer
2. Poor laboratory assistance
It is not appropriate to think of the angulated screw channel system as a one-size-fits-all fix for any implants positioned outside of the optimal range. The angle of degree change has a limit, thus in situations where it is not possible to place an implant in the best possible location, it should be used as a backup strategy.
Before the implants are placed, it is important to perform the necessary treatment planning and restoration-driven implant planning in order to ascertain the degree of angulation change and, if at all possible, make preparations for it. Because the design of the abutment allows for modifications to be made to the engagement of the screw, there may be circumstances in which the material at the place where the screwdriver and screw are engaged has insufficient thickness. It is possible that the thickness of the prosthetic material will need to be increased in order to prevent it from shattering. Because of this, the look of the prosthesis and its emergence profile may be altered as a result.
The aesthetic issues in the anterior area should also receive additional thought. When an implant is placed in a patient with a high smile line, the use of angulated screw channel systems may not always be able to make up for any aesthetic disadvantage. An uncorrectable show-through of the abutment junction as a greyish shadow through the buccal mucosa may result from implant placement that is too far forward in the face and too shallow in the face. In order to allow for the best planning of the emergency profile and restoration aesthetics, implants should ideally be positioned 3 mm below the cemento-enamel junction.
Another thing to think about is the height of the Ti-base abutments on some systems. The prosthesis may decement from the abutments under functional loads if the abutment height is shortened to provide for rotational mobility. This could also leave less space for the abutment to engage with the dental prosthesis.
It is possible to apply torque to the screw on a nonaxial axis due to the hexalobular screw design of the angulated screw channel solution. In comparison to systems where the torque is delivered in a straight screw axis, some research has been done on applying torque in a nonaxial direction and how cyclic loading affects the reverse torque values. According to a Goldberg et al. study, angulation had no bearing on RTVs. RTVs were considerably lower with increasing angulation change in certain investigations conducted on samples lacking cyclic loading. There has been conjecture that the asymmetric hexalobular driver head may lead to insufficient abutment screw contact at higher angulation changes, hence failing to apply the necessary torque.
The impact of cyclic loading on the RTVs was then investigated by Mulla et al. Following cyclic loading, the RTVs of hexalobular-designed, 25-degree angulated screw channel systems were compared to crowns cemented on 0-degree screw channel abutments. Their research revealed that, in terms of RTVs, angulated screw channel solution systems with higher starting recommended torque values (35 Ncm) might function comparably to traditional straight-access abutments. Comparable findings were obtained by Swamidass et al. when they examined the % torque loss. The maintenance of the screw torque should therefore be anticipated to be similar for angulated screw channel systems and standard screw channel abutments.
Both independent and implant manufacturers provide several angulated screw channel methods. Although the study by Frieberg and Ahmadzai did not find that using original components significantly improved aesthetics, they did note that doctors had noticed a wider palatal access hole when using non-original components. A smaller screw access channel diameter has reportedly been mentioned as an advantage of some systems, such as the Straumann Angled Solutions (Straumann AG, Basel, Switzeland), which lowers the chance of chipping.
Therefore, it might be worthwhile to take into account using an angulated screw access channel system with a lower screw access channel diameter where feasible and a higher recommended initial torque value (such as 35Ncm) when choosing an angulated screw channel system.
When employing such abutment systems, it's also critical to pay attention to appropriate case selection and take the indications and contraindications into account. Finally, for the final restoration to be successfully fabricated, it is imperative that the laboratory and you communicate about their capacity to enable the fabrication of prostheses compatible with angulated screw channel components.
