Transforming Channel Shape Osteotomy Into Tunnel Shape Osteotomy for Zygomatic Implant. A Randomized Control Trial

The term "tunnel osteotomy" is used because the alveolar osseous entry point has a floor, lateral walls, and a more or less complete roof. When a tunnel osteotomy was chosen, the sinus membrane was perforated at the time of completion of the antrostomy. The objective was to achieve osseointegration at the neck level also to seal the sinus entrance in the long-term using: (1) a stable zygomatic implant with (2) a suitable threaded neck section (3) bordered by enough bone at the coronal entry, (4) stabilized by adequate apical zygomatic anchorage; and (5) connected to a rigid prosthesis that provides adequate masticatory load distribution. The "tunnel osteotomy" was also employed in ZAGA Type 3 cases when the alveolar bone adopts a triangular, buccally inclined, profile and the maxillary anterior wall was concave(23).

When inadequate residual bone architecture at the crestal level (less than 4 mm of thickness) was measured, the coronal osteotomy was buccally shifted to prevent future sinus or nasal-oral communication/fistula. Implant beds were designed to be carved as much as possible into both the buccal alveolar and maxillary wall bone with the limits of sinus lining integrity. This osteotomy type is known as a "channel osteotomy" and is noted when lateral walls and floor are present but with no roof(23).

On analyzing the evolution of the abovementioned technique (ZAGA), it is seen that the position of the neck of the zygomatic implants has been mobilized laterally from an intrasinus position to an extrasinus position. Different anterior techniques have thus sought to avoid maxillary sinus complications(19,24,25). However, hard and soft tissue infective and aesthetic complications (exposure of the implant threads) were detected(26-28).

Peri-implant hard and soft tissues are crucial for avoiding complications around conventional implants. Two aspects have been studied in this regard: buccal cortical bone and the thickness and width of the peri-implant keratinized mucosa. On the one hand, a recent systematic review has reported that a buccal cortical thickness of close to 2 mm was associated with less vertical bone resorption and less mucosal recession(29).

On the other hand, the presence of sufficient keratinized mucosa thickness exerts a protective effect against marginal bone loss(30,31). These abovementioned concepts to minimum necessary peri-implant tissues could be extrapolated to zygomatic implants. A number of techniques for bone and soft tissue enhancement around zygomatic implants have been described, with high success rates.