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Vertical augmentation

The sandwich osteoplasty

06.04.2015
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The sandwich technique facilitates soft-tissue management and allows experienced surgeons to achieve good results in patients with greater vertical bone deficiencies.

Prof. Bilal Al-Nawas | Germany

When the ridge has to be augmented vertically to allow implant placement, sandwich osteoplasty offers important advantages over onlay techniques:

  • Due to the repositioning of the keratinized soft tissue, no further soft-tissue surgery is usually necessary.
  • Only native bone is located in the sensitive area crestally around the implant.
  • The grafted bone blocks are supported apically and coronally, thus facilitating bone in-growth and allowing considerable vertical gain.

As a general prerequisite for this technique, a residual bone height of 4 mm above the inferior alveolar nerve should be available. The horizontal ridge width should be large enough to allow the insertion of a dental implant. Otherwise, the surgeon should exercise alternative augmentation methods. Also, due to the rigid palatal mucosa, the technique is limited primarily to the lateral part of the mandible.

 

Short implants vs bone augmentation

In the situation of reduced vertical dimensions, a CBCT (Cone Bean Computer Tomography) image is often required to weigh the option of short implants versus a vertical bone augmentation. While short implants may also yield good long-term outcomes, a vertical augmentation will allow placement of implants with regular dimensions in an optimal three-dimensional position. This may facilitate the prosthetic treatment steps and improve the esthetic result. Nevertheless, the patient should be informed about possible complications such as graft failure or nerve lesions before surgery.

 

The key for success: flap preparation

A successful interpositional grafting procedure requires an adequate incision technique for the soft tissues that does not compromise blood supply. Under local nerve block anesthesia (buccal and inferior alveolar nerves), a subperiosteal poncho flap (repositioned perforated attached gingival flap) starting from the vestibulum is prepared and elevated. The critical step in this phase is the identification of the mental foramen. Afterwards the flap is raised close to the attached mucosa of the crest, while the crestal and lingual mucosa is left attached to the bone.

 

Osteotomy and interpositional grafting

The osteotomy above the nerve is performed using piezo surgery, since this technique allows higher precision and control than saws or burs in cutting just the bone. Palpating the tip of the piezo with a finger at the lingual sides can further help avoid damage to the soft tissue. Care is taken to keep the soft tissue attached to the cranial segment. After performing the osteotomy with a chisel, the mylohyoid muscle can easily be stretched.

The cranial segment can be elevated and stabilized by inserting a block of Geistlich Bio-Oss® – pre-shaped by piezo instruments – into the emerging gap.1,2 With interpositional grafting in a sandwich osteoplasty, vertical augmentations of up to 8 or 10 mm can usually be achieved without problems.

Following the graft placement, a mini plate with short, self-tapping screws is attached to fix the bone and to avoid nerve damage. The thick poncho flap can be closed with a double layer suture without further releasing incisions. The time until implant placement depends on the height of the vertical augmentation, but a healing phase of six months is sufficient in most cases. For implant placement, a crestal incision is performed, which allows the mini plate to be removed at the same time. 

Pitfalls

The sandwich technique provides good success rates if there is careful patient selection and planning, and adequate surgical techniques are used. However, complications may arise from some typical pitfalls. If the cranial segment is too thin, it might fracture during transposition. Additionally, a residual infection or osteomyelitis after extraction can lead to graft infection and failure. Soft tissue and osteotomy problems may occur at the distal tooth due to the close spatial relationship.

Prof. Bilal Al-Nawas

Prof. Bilal Al-Nawas | Germany

University Medical Center of the University of Mainz
Clinic for Oral and Maxillofacial Surgery
Mainz

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