The cross‐pin retained implant supported restoration: a study of gasket placement and leakage

Abstract

Background: Advantages of cross-pin retained implant supported restorations (ISRs) include predictable retrieval and predictable retention. Unlike direct to fixture (DTF) or cement retained restorations, the prosthetic design of a cross-pinned restoration retains gaps at the interfaces between the crown, abutment and cross-pin screw. These spaces permit leakage into the suprastructure and gasket placement has been recommended to prevent this leakage. Methods: Five different gaskets were assessed for their ability to prevent leakage into a cross-pinned ISR. The gaskets tested were: cement admixture on the cross-pin screw; cement admixture on the inner surface of the coping and the cross-pin screw; cement admixture on the inner surface of the coping only; cement admixture placed 1 mm from the margin of the coping and a filler placed in the abutment chimney. Results: Only gaskets which sealed both the cross-pin screw interface and the abutment-crown interface prevented leakage. A filler placed in the abutment chimney prevented leakage into this space but did not prevent fluid accumulating between the coping and abutment. Conservative placement of cement at the margin of the coping failed to prevent leakage. Conclusions: Cement gaskets may effectively prevent leakage into a cross-pinned ISR. However, the use of a cement as a gasket has to be weighed against the issue of predictable retrieval, cement extrusion and incomplete seating.

Does the transversal screw design increase the risk of mechanical complications in dental implants? A finite elements analysis

“…The location of the stress in the neck of the prosthetic screw of the transocclusal screw model and in its head coincides with the area most prone to the loosening/fracturing described in other studies, while in the transversal screw, the stress is primarily located in the area connecting to the abutment, indicating that this screw can bring the retainer closer towards the margin of the implant. This leads to a reduction in misfit, which in turn clinically hinders the filtration and colonization of bacteria . In accordance with what has been stated here, the clinical application of this is that the practitioner may choose a transversal screw model with a view to achieving fewer mechanical complications in the prosthetic screw model—including with oblique loads—compared with those encountered with the transocclusal screw model.…”

“…Different biomechanics studies show that the stress on the prosthetic components (abutment and screws) of a single‐unit prosthesis is mainly found in the conical connection between the abutment and the implant and in the neck and first threads of the abutment screw or along the threads of the transocclusal screw . However, no data is available for the stress on the implant‐retained prosthesis of a transversal screw model; the information available shows only the description and method results of clinical cases . Furthermore, determining the distribution and the location of the highest concentration of stress in the prosthetic components has clinical interest inasmuch as it can provide data to help implement designs that offer greater resistance and optimum stress distribution in order to avoid or prevent mechanical and technical risks.…”

Effect of crown retention systems and loading direction on the stress magnitude of posterior implant-supported restorations: A 3D-FEA

“…Several implant systems have been evaluated aiming to combine optimal mechanical, biological, and aesthetics of the prosthesis, reducing the above-mentioned disadvantages [ 11 ]. One of the previous purposed retention types was the lateral-screw-retained implant prosthesis in which an extra lateral screw is used to retain the crown instead of the conventional screw accessed through the occlusal surface [ 12 ]. This technique has been first purposed in 1995 [ 13 ], named as lingual locking screw.…”

3D-based buccal augmentation for ideal prosthetic implant alignment—an optimized method and report on 7 cases with pronounced buccal concavities

“…Limiting the system is the additional space requirement, which increases the risk of soft tissue complications, and the need for a more voluminous screw channel that enables the screwdriver to be inserted correctly, which can lead to a thinning of the veneering materials and possibly to technical or esthetic problems [30]. Similar problems arise for horizontal screw connections and cross-pin retained restorations [31].…”