Minimally Invasive Subnasal Elevation and Antral Membrane Balloon Elevation Along With Bone Augmentation and Implants Placement Open Access

Reconstruction and rehabilitation of the atrophic edentulous anterior maxilla present a considerable challenge to dental implant therapy. Anterior maxillary osteoplasty has emerged over the years as the best strategy to address this problem. Implants were traditionally placed in a second procedure.¹  Recently, minimally invasive antral membrane balloon elevation (MIAMBE)²  was successfully introduced to perform posterior maxilla bone augmentation even in the most challenging subset of patients³  (eg, those in which there are multiple septa or extremely atrophic “eggshell” maxilla). However, the subnasal maxilla remained a condition in which open surgery was the only therapeutic option. We present 2 cases in which subnasal elevation and MIAMBE were simultaneously performed and followed by bone grafting and implant placement.

A 57-year-old man was referred for rehabilitation edentulous left anterior maxillary segment (missing teeth 12, 13, and 14). Tooth 12 was previously extracted because of vertical fracture, and tooth 14 was extracted because of periodontal disease. The patient's medical history was insignificant (including absence of sinusitis or allergies), and he has never smoked.

The treatment plan was implant placement in sites of teeth 12, 13, and 14. The preoperative computed tomography (CT) analysis (Figure 1) demonstrated that the bone height/width measurements in these sites were 8.8/4.18 mm, 5.57/2.53 mm, and 5.0/5.0 mm in teeth 12, 13, and 14, respectively. A polypoid mass was incidentally noted in the posterior compartment of the septated maxillary sinus.

Initially, 3 mm posterior to an existing implant (tooth 11), a full-thickness incision was made from the palatal to the buccal border of the alveolar ridge. A horizontal full-thickness incision was then performed in the middle of the alveolar crest to expose it. On the buccal aspect of the flap, a partial-thickness flap was performed beyond the mucogingival junction (by doing so the periost is still attached to the bone, and its blood supply is preserved).

After alveolar crest exposure at sites 12 and 13, a horizontal bone incision was made at the center of the alveolar ridge with a diamond disc (0.25 mm thick, 8 mm diameter, Microsaw, Dentsply Friadent, Mannheim, Germany). The initial bone split incision was deepened using Piezosurgery with an OT7S tip (Mectron, Carasco, Italy) to a depth of 1 mm below the nasal floor (based on CT measurements). A D-shaped SplitMax chisel (Meta, Italy, reference number 06-0301) was used to further widen the space between 2 plates (palatal and buccal). The ridge was carefully split while ensuring that the buccal and palatal cortical plates did not detach. Drilling with a pilot drill (2 mm diameter) at the future implant site up to 1 mm underneath the nasal floor (as measured by CT) was followed by osteotomy widening (Figure 2) from 2 to 3.3 mm with the SplitMax 3.3 mm diameter chisel (Meta, Italy, reference number 06-0306) up to the nasal floor.

Bone graft material (0.25 mL Mineross, BioHorizons, Birmingham, Ala) was injected with a dedicated MIAMBE bone graft injector (MIAMBE, Natanyah, Israel), and the nasal floor was subsequently fractured with a SplitMax 3.3 mm chisel (Figure 3).

Bone graft material was injected again (an additional 0.25 mL Mineross, BioHorizons) into the osteotomy with subsequent placement of 3.3/13 mm and 3.3/11 mm implants (NTI Implants Hi-Tech, Herzlia, Israel) at sites 12 and 13, respectively (Figures 4 and 5).

At site 14, sinus floor elevation was accomplished using the MIAMBE technique,^2,3  initially drilling (2 mm in diameter) at the center of the alveolar crest up to 1 mm underneath the sinus floor and, subsequently, widening the osteotomy from 2 mm to 2.9 mm with the MIAMBE osteotom. Bone substitute material (0.1 mL Mineross, BioHorizons) was injected with the MIAMBE bone graft injector, and the sinus floor was subsequently fractured with the MIAMBE osteotom (Figure 6). The antral membrane integrity was assessed by the Valsalva maneuver. The MIAMBE screw-tap working length was adjusted according to sinus floor depth (sinus floor depth + 1 mm) and tapped into the osteotomy. The antral membrane integrity was reassessed. Subsequently, the metal sleeve of the MIAMBE balloon-harboring device was advanced 1 mm beyond the sinus floor. The MIAMBE balloon was inflated with contrast material with the dedicated MIAMBE indeflator. Balloon inflation and antral membrane elevation were assessed by serial periapical radiographs (Figure 7). Once the desired elevation was obtained the balloon was removed, membrane integrity was reassessed (by direct visualization using the dedicated suction syringe and the inward and outward movement of blood within the osteotomy during inspiration-expiration). Bone substitute (1 mL Mineross, BioHorizons) was injected through the osteotomy into the sinus underneath the antral membrane, and implant placement was performed (4.2/13 mm TFR, Hi-Tech Implants).

The gap between the implants was filled with bone graft material (Mineross, BioHorizons). The alveolar ridge was covered with a platelet-rich fibrin membrane (obtained by centrifugation of 10 mL autologous venous blood at 2700 rpm for 10 minutes) followed by coronally positioned flap and primary closure by sutures (Vycril 4/0 and Silk 4/0). Periapical radiographs obtained at 3 months (Figure 8) and CT scans obtained at 8 months (Figures 9 through 11) confirmed that a new nasal floor had been created with considerable gains in bone height. Of note, the polypoid mass had not changed in size through the entire follow-up period.

A 51-year-old woman was referred for esthetic and functional reconstruction of an edentulous maxilla. Her medical history was insignificant except for a history of cigarette smoking (1 pack per day for 30 years). The treatment plan was to restore the maxilla with a fixed complete denture from sites 2 through 15 (5 implants on the right side starting from tooth 6 distally and 5 implants on the left side starting from tooth 11 and progressing posteriorly). The implants were placed in 2 separate surgical sessions starting with the left side. The maxilla reconstruction included minimally invasive subnasal elevation, bone augmentation, and placement of implants using the osteotom technique in the subnasal segment and the MIAMBE method more posteriorly.

Anatomic-morphologic evaluation and measurements were obtained from a panoramic view radiograph (Figure 12) and CT (coronal plane shown in Figure 13 and sagittal plane shown in Figure 14). The radiologic analysis revealed 3 septa and 4 compartments in the left maxillary sinus. In the anterior maxilla, the residual ridge was narrow and shallow and not amenable for implant fixation.

A full-thickness buccopalatal incision posterior to the incisive papilla was followed by a horizontal full thickness incision in the middle of the alveolar crest. On the buccal aspect of the flap a partial thickness flap was performed beyond the mucogingival junction.

At sites 11 and 12, the Microsaw disc was used for initial cutting and then the Piezosurgery with an OT7S tip was used to deepen the osteotomy. This was followed by widening the space between the plates using the D-shaped SplitMax chisel, drilling with a 2 mm drill up to 1 mm underneath the nasal floor and fracturing the nasal floor (Figure 15) using the SplitMax chisel (3.3 mm, reference 06-0301).

After nasal floor fracturing, bone substitute (0.25 mL Mineross, BioHazard) was injected into the osteotomy, and the first 3.3/13 mm NTI implant was inserted at site 11. A similar protocol was used for the 3.3/13 mm NTI implant at site 12 (Figure 16).

In sites 13 and 14, subsequent to bone augmentation of the maxillary sinus floor by the MIAMBE technique, two TFR 4.2/13 mm implants were placed (Figures 17 through 20). The 12-month CT follow-up is shown in Figures 21 through 23.

The approach to the atrophic anterior edentulous maxilla has evolved over the past 20 years. Surgical reconstruction for bone mass restoration has been rendered highly effective, resulting in good procedural success and excellent implant survival rates (of 80%–95%).^4,5  However, these surgical procedures, which usually involve autologous bone harvesting (from the iliac crest, calvarium, tibia, mandible symphysis, maxillary tuberosity), were associated with donor-site–related morbidity. Moreover, these procedures mandated general anesthesia, hospitalization, and high costs and required exceptional cognitive and surgical skills. These surgical procedures are associated with considerable disability, discomfort, and serious complications (eg, hemorrhage, graft resorption, graft exposure, wound dehiscence, fistula, infection, sinus membrane perforation [26%⁶ ], and acute sinusitis).

Surgical reconstruction of the edentulous maxilla may carry some other considerable benefits beyond enhancing the support and integration of dental implants.⁷  These additional benefits include restoring facial morphology and soft tissue support and improving impaired phonetics, esthetics, and airway function. However, only a minority of edentulous patients require these incremental attributes and benefits.

Because surgery creates a more radical alteration in the relationship between the mandible and the maxilla, it is logical (although not universally acceptable^8,9 ) to plan implant placement only after the morphologic changes associated with surgery have settled and not during the reconstructive surgery.^10,11  This recommendation for deferred implant placement appears to be applicable even to less extensive surgical reconstructions, such as “sandwich osteotomies.”¹² 

There is a need for a minimally invasive method that will allow bone augmentation of the subnasal (anterior) maxilla. Such a procedure can result in higher patient acceptance and may overcome the treatment barriers associated with current open surgical methods.

After introducing the osteotom method and subsequently MIAMBE¹³  for noninvasive bone augmentation of the atrophic posterior maxilla, the subnasal segment of the maxilla remained the only maxillary segment in which minimally invasive bone augmentation and implant placement was not feasible.¹⁴ 

We describe 2 of 11 cases in which subnasal elevation and MIAMBE were performed side by side at our clinic. The procedure is done during a single sitting under local anesthesia, with basic periodontal instrumentation and without any short- or long-term discomfort.

MIAMBE has formerly demonstrated wider applicability (no exclusions), similar efficacy, and superior safety compared with open sinus lift. The MIAMBE procedure resulted in fewer infections (0.8% versus 5%) and membrane tears (5% versus 20%–55%); absence of vascular, nerve, or bone injuries (occasionally reported with open sinus lift); and absence of prolonged swelling, hematoma, sinus dysfunction or pain²  (which are seen very frequently in open sinus lift and result in low patient acceptance rates).

It should be noted that the nasal cavity floor is considerably different from the floor of the maxillary sinus. The nasal floor lining is much thicker and more amenable to mild osteotom elevation without tearing than the antral membrane lining of the maxillary sinus. Based on our initial experience, the nasal floor lining can be raised only 2–3 mm by using the osteotom alone. However with hydraulic pressure exerted by bone graft material injection, a 5 mm elevation underneath the inferior turbinate can potentially be accomplished.

One of the major issues in planning nasal floor elevation is the decision regarding the optimal or desirable elevation. Essentially, any penetration of the nasal floor considerably enhances implant support in view of the exceptional density and quality of the nasal floor bone. The desired elevation should be individualized based on the depth of the impression behind the piriform rim. Although the desired elevation could ideally be 2–5 mm, the elevation should not encroach or come in close vicinity (<1–3 mm) to the inferior turbinate (inferior concha) as that may compromise nasal air flow. If excessive elevation encroaches on the inferior turbinate, resulting in functional impairment of the nasal flow, the inferior turbinate (concha) may have to be modified or removed surgically to secure nasal air flow. Although in theory more than modest elevation of the nasal floor can result in nasal airway modification and even obstruction, this did not present as a clinical problem in any of our patients to date.

Although the procedure is in its infancy, the authors are confident that with experience and evolution of dedicated instrumentation this procedure can be streamlined and become a more commonly used technique applicable to most patient types.

On the patient end this procedure is associated with less pain and discomfort, brief recovery, and a shorter time to implant loading. From the doctors' standpoint it is a shorter procedure, which can be accomplished in an outpatient settings; requires less surgical skills, time, and equipment; and is free from any meaningful complications. The authors are convinced that once this procedure is refined it will likely generate a higher patient and practitioner acceptance rate than current open procedures.

We have described just 2 cases representing an evolving method that will require confirmation regarding procedural success and failure rates, the quality and volume of bone augmentation, and implant survival.

Minimally invasive subnasal floor elevation accompanied by bone augmentation and implant placement appears feasible. Dedicated instrumentation and method refinement are likely to further enhance the efficacy and safety of this procedure first reported here.