Implant-supported full-arch restorations using an external spherical implant connection. A case series

OBJECTIVES: Full-arch rehabilitation has always represented the most challenging work both from the surgical and from the prosthetic aspect. One of the challenges in the treatment of full-arch implant supported rehabilitation is the implant alignment and therefore the prosthetic framework passivation.

MATERIALS AND METHODS: Two cases of atrophic edentulous mandible and maxilla has been treated with implant-supported full-arch rehabilitation. A novel implant design (Bionica Orbit®), characterized by a spherical external connection that allow a 360° abutment rotation with an axial correction of 30° has been used. Bionica Orbit® implant has been
selected because they are born to facilitate the prosthetic framework passivation and the correction of implants disparallelism. Intramucosal spherical connection allows to place a single abutment, named LEM, from 0° to 30° axial inclination on 360° of revolution combined with mini, narrow and traditional body.

RESULTS: Two full-arch mandible and maxillary rehabilitation has been successfully treated with only one unscrew event on the provisional framework over the follow up.

DISCUSSION: This case series reports two cases of complete edentulism treatment in medically compromised patients presenting resorbed jaws. Such patients present a notable challenge for the clinician and atraumatic measures should be implied to reduce post-operative discomfort. Procedures such as maxillary sinus lifting, and guided bone regeneration often become necessary for achieving the implant rehabilitation of edentulous patients. The number of visits, the duration and the complexity of the surgeries significantly increase when bone graft procedures are adopted.
In these two full-arch rehabilitation cases of atrophic mandible and maxilla the main goal was to rehabilitate patients with fixed prosthodontics avoiding complex regenerative procedures.
For the two clinical scenarios reported in this article, the upper arch and lower arch rehabilitations were approached in different ways. The choice of inserting six instead of four implants for the upper removable rehabilitation was driven by the reduced horizontal dimension of the alveolar ridge that forced the clinician to opt for smaller implant diameters, avoiding bone graft surgery. The premaxilla region was intentionally avoided since the available amount of bone was considered insufficient. To reduce the risk of mechanical complications in narrow diameter implants, the thickness of the material in the implant neck area is a determining factor.
The implant system implied in this case presented an external spherical connection where the abutment screw did not engage the implant body, but it was mostly confined to the spherical head of the fixture, thus allowing greater titanium thickness in the implant neck. Moving the implant-abutment connection the farther away from the crestal bone as a safety
measure is often achieved by either implying tissue-level implants or by the interposition of a mesostructure between the implant and the prosthetic framework.
The implant system used for the rehabilitations described in this paper shared both advantages of a tissue-level connection and an adjustable abutment acting as mesostructure.

CONCLUSIONS: Within the limitations of this clinical report, using rotational abutments over external spherical implant connections seems a valuable solution for complete-arch fixed and removable rehabilitations. The system simplifies the prosthetic workflow and allows intraoral alignment of the abutment reducing the incidence of prosthetic framework misfit. The surgical protocol could benefit from the use of narrow implant diameters, possible due to such implant connection.

CLINICAL SIGNIFICANCE: This eternal spherical connection implant system can improve the full-arch rehabilitation allowing to minimize the surgical trauma avoiding regenerative procedures when possible and correcting in a second stage the prosthetic axis thanks to a very flexible connection and to an intraoral parallelizing device.