Trans-Sinus Implants

Overview:

Trans-sinus implants may be used when the insertion of conventional tilted implants is not possible before considering the use of pterygoid and zygomatic implants or bone grafting procedures.

What Are Trans-Sinus Implants?

For the rehabilitation of atrophic posterior maxilla, that is, the edentulous and resorbed maxillary (upper jaw region at the level of premolars and molars), an alternative technique is adopted by the implantologist to achieve prosthetic success and prevent biologic failure of the implants, especially in severely resorbed bone morphologies.

Placement of implant via the trans-alveolar maxillary sinus floor lift is a positively tested method that is also minimally invasive in comparison with endosteal implants (most commonly used dental implants). Trans-sinus implants thus can offer maximum benefit via this route or approach mainly for bicortical anchorage (nasal cortical bone can also be used) or stabilization. The outcome measures studied as per conventional implant research show less esthetic and functional complaints from the patients and a reduction in postoperative complications compared to traditional endosteal implantation (is evidential). Success rates of the prosthetic part of the implant and the peri implant-bone marginal levels have also been considerably improved by adopting this minimally invasive technique of the trans-sinus approach.

What Are the Indications for a Trans-Sinus Implant?

Maxillary edentulous patients or patients with a terminal dentition who presented a maxillary sinus pneumatization can be selected to receive an immediately loaded fixed restoration supported with four or six implants.

However, in a few cases, the maxilla may have a particular anterior sinus wall anatomy that does not allow insertion of a tilted implant fully inside the bone in the premolar and molar regions, at least in one side, so the case should be studied thoroughly by the dental implantologist before proceeding with this trans-sinus implant.

The fixed rehabilitation of a totally edentulous maxilla is often associated with anatomical limitations, generally due to a decreased bone volume in the posterior area, especially when an immediate function is implemented. Bone atrophy or resorption evolves rapidly during the first year after tooth extraction and then progresses in an unpredictable manner. The other factors that can affect the quality of available bone are mainly the progressive maxillary sinus pneumatization and the use of removable prostheses.

When bone volumes are not sufficient for implant placement, bone augmentation procedures can be performed. However, alternative treatments should be considered, in particular tilted implants, pterygoid and zygomatic implants. These alternative treatments, such as the trans-sinus implants, could be indicated in patients who cannot undergo bone graft procedures for different financial, psychological, or clinical reasons. Posterior implants are angled forward, passing trans-sinus to fixate in the nasal cortical bone. The trans-sinus implants can be inserted without sinus bone grafting or simultaneously with bone grafting and placed into immediate function achieving good success rates upto three years.

What Are the Inclusion and Exclusion Criteria?

Inclusion Criterion:

• Presence of a residual bone height measured in computed tomography (CT) scans of minimum 4 mm and maximum 6 mm available under the sinus floor to anchor the implant head.

• Anterior sinus wall curvatures and/or the inferior corner of the anterior wall of the sinus positioned anterior to the first premolar.

Exclusion Criterion:

The following exclusion criteria were used,

• Sinusitis diagnosed preoperatively.

• The presence of uncontrolled systemic diseases could represent a general contraindication to implant dentistry.

• Emotional instability.

• Undergoing maxillary radiation therapy.

• Undergoing active chemotherapy or amino bisphosphonates.

• Substance abusers.

• Patients who underwent bone grafting procedures at the planned implant sites.

• Patients with sufficient bone height bilaterally in the posterior maxilla allow the insertion of tilted implants through the standard protocol.

What Are the Advantages of Trans-Sinus Implants?

The advantage of placing trans-sinus implants mainly is that they can be placed without a bone graft, reducing the surgery time and decreasing the treatment cost. Trans-sinus implants are indicated in the presence of a residual bone height of a minimum of 4mm and a maximum of 6 mm available under the sinus floor to anchor the implant’s head.

Alternative less invasive treatments should be considered, in particular short implants or crestal sinus elevation procedures. On the other hand, such alternative procedures could reduce the possibility of reaching good primary stability of the implant in most cases. Implants can be tilted through the sinus and can still be immediately loaded provided that the implants are inserted with good primary stability, and a cross-arch-stabilized prosthesis is made. All the implants are inserted with torque superior to 45 N cm to be immediately loaded as previously described for single implants. The primary stability required is easily reached in all the patients because implants can be inserted in three layers of cortical bone. Even the nasal cortical bone is used, if necessary, to increase stability in the case of soft bone. Operators can choose to graft or not the sinus simultaneously to trans-sinus implant placement supporting cross arch immediately loaded fixed prostheses. If these results are confirmed by longer follow-ups, it should be better to avoid any graft in order to reduce the morbidity and the cost of the treatment and to simplify and reduce the time of the procedure.

What Is the Trans-Sinus Implant Procedure?

1. All patients undergo at least one session of oral hygiene instructions and professionally-delivered debridement when required prior to the intervention.

2. Antimicrobial prophylaxis is obtained with 1 gram of Amoxicillin + Clavulanic acid (or Clarithromycin 500 mg if allergic to Penicillin) starting the night before the intervention, twice a day, for seven days.

3. On the day of surgery, patients are treated under local anesthesia using Articaine with Adrenaline 1:100,000.

4. Tooth extractions, when needed, are performed as atraumatic as possible, attempting to preserve the buccal alveolar bone.

5. Extraction sockets are then carefully cleaned to remove any granulation tissue.

6. The incision is made along the crest with vertical releasing incisions to obtain access to the mesial wall of the sinus.

7. Once a full-thickness flap is elevated, the operator is informed whether the trans-sinus implant must be placed without simultaneous bone grafting or sinus elevation procedures.

Conclusion:

Trans-sinus implants are a good alternative approach to conventional endosteal implants in case of bone atrophy in maxillary posterior regions. A detailed assessment by the dental implantologist and bone grafting as required will prevent prosthetic failures.