In these clinical scenarios, ZAGA Concept recommends to buccally displace the osteotomy with the aim of sinking the implant neck/body as much as possible into the alveolar and lateral maxillary wall bone while maintaining the sinus lining integrity with no membrane perforation at the crest level. This type of osteotomy, not capable of providing a complete covering of the implant mid-body and neck is known as “Canal Osteotomy''. It is a groove made on the coronal alveolar bone, and sometimes also in the lateral maxillary wall and zygomatic buttress. As a waterway or channel; it has a floor, lateral walls with different heights and no roof. When a “Canal Osteotomy” is performed, the maxillary bone is not covering the buccal zygomatic implant mid-part, nor its neck.
This approach belongs to the ZAGA Concept recommendation, and its rational is based on the fact that the implants with minimal crestal bone surrounding their entry point may present bone resorption under function and within time with a subsequent oral-antrum fistula. Indeed, deficient bone to implant contact (BIC) may be jeopardized by different circumstances i.e. periodontal disease history, inadequate oral hygiene, use of water pressure devices at the gingival junction, inadequate use of the dental probe, etc. Moreover, it has been speculated that the lack of crestal bone support would end up in a transversal mobility of the long coronal part of the zygomatic implant facilitating an oral-sinus communication.
Placing the zygoma implant platform partially or outside of the sinus, and with a lateral maxillary bone support/contact; would allow a better prosthetic positioning together with a more conservative approach regarding the sinus integrity preservation. In order to prevent soft tissue dehiscence when placing the implant laterally to the maxillary wall, it is recommended to groove the buccal bone to house the implant body with as much lateral submergence as possible into bone, in such a way that it does not protrude against the mucosal position and does not compress the soft tissue vascularity. The depth limit for the canal digging is the sinus membrane integrity at this level. The use of a channel section implant adapted to this osteotomy type i.e. the Straumann ZAGA Flat, would help the surgeon to prevent soft tissue complications.
The present case report is intended to demonstrate how a bony canal having section in the shape of an arc of circumference, would optimally be sealed by an implant showing a circumferential arc section as well. Each step of the procedure will be illustrated with figures showing the insertion of a flat zygomatic implant section that fits into a channel with a minimal buccal impact against the soft tissue.
Initial situation
A 75-year-old female patient presented to our office with the chief complaint of deficient chewing function and poor aesthetics. Regarding her medical condition, she reported not suffering systemic diseases and not taking any medication.
The clinical assessment in the upper jaw showed the presence of hopeless teeth on positions #13, #12, #11, #21, #22 and #23, with advanced chronic periodontitis and atrophic ridges on the posterior areas. On the other hand, in the lower jaw she presented an implant on position #43 supporting a failing partially removable prosthesis.
The radiographic assessment depicted an extreme bilateral bone loss on both premolar and molar regions at the upper and lower jaws. Furthermore, a horizontal bone loss in the anterior area on both upper and lower arches was presented.
The patient expectations were high, and she requested a short-lasting therapy avoiding large bone augmentations with an immediate fixed prosthesis at her upper and lower jaws.
The decision was done in favor of the extractions of all remaining teeth which were considered hopeless and immediately followed by the complete rehabilitation of the upper and lower jaws a with fixed prosthesis anchored on oral implants.
Treatment planning
The treatment decision-making process was based on impressions and casts from the upper and lower jaws using a SAM dental articulator, the radiographic assessment (X-rays & CBCT) and a digital planning software (Figs. 1- 4).
Following a careful evaluation; it was planned to perform in the upper jaw a Hybrid Zygoma approach (4 dental-implants and 2 zygoma-implants), that included a ZAGA surgery with two ZAGA flat implants of 40 mm length on the right side and 42.5 mm length on the left side (advanced), four conventional dental implants, a periodontal plastic surgery (pediculated connective scarf graft) and an immediate fixed restoration consisted on a screwed retained provisional bridge. Moreover, in the lower jaw five conventional implants with an immediate screw-retained fixed restoration were planned.
According to our standard protocol, the final restorations were delivered six months after surgery.