Minimally invasive maxillary sinus elevation using balloon system: A case series.

The posterior maxillary segment frequently exhibits insufficient bone mass to support dental implants. Sinus floor augmentation enables implant placement in the posterior maxilla. This case series included ten sites, in which sinus floor elevation was done using sinus lift balloon system followed by augmentation utilizing irradiated cancellous bone allograft. Postoperative radiographic assessment of vertical bone gain was done at 3 and 6 months follow-up period. The mean initial and final bone height were 6.16 and 10.50 mm, respectively, with a mean increase of 4.34 mm at 6 months being observed with nil complication. The presented technique might represent a viable alternative for sinus elevation in posterior atrophied maxilla. Irradiated cancellous bone allograft can be advocated as an ideal bone graft material for sinus augmentation procedures.

INTRODUCTION

Implant success and primary stability are greatly affected by bone volume in situ. Reduced vertical bone height in the posterior edentulous maxilla may be attributed to the postextraction ridge atrophy and pneumatization of the maxillary sinus, thus limiting the placement of dental implants. Maxillary sinus augmentation has emerged as the most common surgical intervention which involves the detachment of schneiderian membrane from the maxillary sinus floor, creating a space filled with bone graft, to promote vertical bone augmentation into the maxillary sinus cavity, enabling restoration with dental implants in future.

Boyne and James in 1980 proposed the conventional sinus augmentation procedure which involves the direct visualization and manipulation of the schneiderian membrane, through the lateral window osteotomy.[1] In addition to being an invasive surgical procedure, it also presents with postoperative morbidities such as bleeding, swelling, and membrane perforation. Later, in 1994, osteotome sinus floor elevation was introduced by Summers, which is a minimally invasive technique that allows for localized maxillary sinus elevation through the alveolar crest. However, this technique has been proved to be effective only when the crestal bone height is more than 6 mm.[2]

Although shorter implants were considered as an alternative to sinus lift procedures, high failure rates were reported when compared to longer implants.[3] Many authors have developed minimally invasive sinus lift techniques over the past decade to surmount the postoperative morbidity associated with the conventional sinus lift procedures.

Minimally invasive antral membrane balloon elevation is a surgical technique developed as a less invasive alternative to lateral window approach, which involves a crestal approach similar to standard implant placement after which sinus elevation is done using the sinus balloon system. Studies reported that the system offers predictable results, safe and effective, and also eliminated the complications associated with conventional lateral window technique.[4] This procedure can be performed with simultaneous implant placement or to develop a site for future implant placement depending on the presence of bone height beneath the sinus floor.

Earlier studies utilized autogenous bone for maxillary sinus augmentation, but with a high rate of resorption and postsurgical morbidity, it has been replaced with other bone substitutes such as allograft, xenograft, and alloplasts.[5] Cancellous bone allograft has been tested for its osteoconductivity and regenerative potential in periodontal defects and also in sinus lift procedures. Histomorphometric analysis after maxillary sinus floor augmentation using cancellous bone allograft revealed 26.1% of newly formed bone and 94.7% of clinically osseointegrated implants.[6] Allografts are capable of osteoinductivity with the liberation of bone morphogenetic protein (BMPs) entrapped in the bone matrix. The role of BMP in the differentiation of osteoblasts and thereby increasing osteoid matrix formation and mineralization has been well documented.

The purpose of this study is to present data on the clinical and radiological outcomes of indirect sinus floor elevation using sinus lift balloon system, followed by bone augmentation utilizing irradiated cancellous bone allograft.

CASE REPORT

A total of nine patients (ten sites), aged between 25 and 60 years with unilateral/bilateral edentulous and atrophied posterior maxilla, who required sinus augmentation before implant placement, were included in the study. Informed written consent was obtained from all the patients explaining the possible procedural side effects. Ethical clearance was obtained from the Institutional Review Board, Ragas Dental College, Chennai.

Inclusion criteria

The primary inclusion criterion was the presence of residual bone height more than 5 mm (from the sinus floor to the bone crest as detected radiographically).

Patients who fell into class B division V according to ABC sinus classification[7] were included in the study, where the location of the sinus floor from the crest was 6–9 mm, width ≥5 mm, and the distance from bone crest to adjacent cementoenamel junction >3 mm.

Exclusion criteria

The exclusion criteria included any systemic condition which would interfere physiological wound healing, orofacial cancers, radiotherapy/chemotherapy in the head and neck region, untreated active periodontal disease, any sinus pathology, previous history of sinus surgery, smoking, and pregnant and lactating women.

Presurgical evaluation

At the initial visit, all patients underwent a clinical and occlusal examination, oral hygiene assessment, and oral prophylaxis.

The ridge width and mesiodistal diameter of the edentulous site were measured. Patients who had an adequate ridge width were further evaluated radiographically, for the availability of residual bone height.

Panoramic radiographs and intraoral periapical radiographs were taken to assess the initial bone height preoperatively, and at 3 and 6 months postoperatively. Initial bone height was measured from the alveolar crest to the floor of the sinus determined by radiovisiography and orthopantomogram.

Case description

Patients were initiated with prophylactic antibiotic coverage 24 h before surgery. Patients were instructed to do preprocedural rinsing with 0.2% chlorhexidine gluconate. After administration of local anesthesia, an alveolar mid-crestal incision was placed in the edentulous ridge followed by sulcular incision around the adjacent tooth; full thickness flap was raised. No vertical releasing incisions were employed [Figure 1].

Figure 1

(a) Mid-crestal incision and flap elevation; (b) Sequential expansion of the osteotomy site with osteotome

Cortical perforation was done using a round bur followed by pilot drill of 2 mm reaching about 1 mm short of the sinus floor. After radiographic verification of the sinus floor with RVG, sequential expansion of the osteotomy site was achieved using a series of osteotomes (from 3.8 to 5 mm) in graduated diameters to laterally condense the low-density maxillary bone [Figure 2a]. The sinus floor was gently infractured to allow the entry of the balloon system.

Figure 2

(a) Sinus lift balloon anchored into the osteotomy site following which inflation done using saline; (b) Pictorial representation of the inflated balloon elevating the sinus membrane

The sinus lift balloon (Zimmer, India) was inflated with air and then deflated to achieve preliminary stretching before insertion into the osteotomy site, after which the sinus lift balloon was anchored and secured into the osteotomy site. Then, the balloon was slowly inflated with normal saline (1 cc of saline solution corresponds to 6 mm of membrane elevation) till the desired elevation was obtained (usually ≥10 mm) [Figure 2b]. The balloon was then slowly deflated and retrieved from the osteotomy site.

Digital periapical radiographs were taken as required to assess the extent of sinus floor elevation at the surgical site during the procedure. Irradiated allogeneic cancellous bone and marrow particulate graft (Rocky mountain tissue bank irradiated allogeneic cancellous bone and marrow particulate) was filled under the elevated sinus membrane using bone condensers after which flap was repositioned and sutured using 3-0 silk sutures [Figure 3]. Patients were advised to refrain from wearing removable prosthesis and follow postoperative instructions diligently.

Figure 3

(a) Grafted sinus; (b) Sutures placed after approximation of the flap

Follow-up

All patients were evaluated radiographically at 3rd and 6th month. Implant placement was initiated 6 months postoperatively [Figures 4 and 5] and reviewed at frequent intervals.

Figure 4

(a) Intraoral periapical radiograph showing osteotome in the osteotomy site; (b) Sinus lift balloon system elevating the sinus membrane; (c) Implants placed in the grafted sinus

Figure 5

Clinical view of implant placed in the augmented sinus

RESULTS

The technique was performed successfully in 10 sites, with no complications. The mean initial and final bone height were 6.16 and 10.50 mm, respectively, with a mean increase of 4.34 mm at 6 months being observed [Table 1], enabling placement of 10 mm implant in the augmented site.

Table 1

Comparison of pre- and post-operative vertical bone height (mm)

DISCUSSION

Sinus augmentation procedure aims at increasing the vertical bone height of the atrophied maxillary posterior region, thereby facilitating implant placement. Systematic review by Wallace and Froum in 2003 demonstrated 91.8% of implant survival with lateral window technique, 93.5% and 98.3% of implant survival with osteotome technique and crestal core elevation, respectively.[8] Various minimally invasive indirect sinus lift techniques have come into stay to overcome the surgical morbidity associated with the conventional lateral window technique.

The present study was undertaken to assess the safety and efficacy of a minimally invasive technique for maxillary sinus elevation using the sinus lift balloon system followed by augmentation of the sinus with irradiated cancellous bone allograft. No complications have been reported in the current study as opposed to the previous studies which have reported on membrane perforation using a sinus lift balloon.[9] A mean increase of 4.34 mm in the vertical bone height has been achieved. Thus, the minimally invasive sinus lift balloon technique proves to be a promising technique in achieving desirable vertical bone height enabling implant placement in atrophied posterior maxilla.

Irradiated cancellous bone allograft (Rocky mountain tissue bank irradiated allogeneic cancellous bone and marrow particulate) exhibits ideal pore size and porosity, permitting cell migration, tissue in-growth, fluid exchange, and vascularization. Hence, it was utilized in the study to ensure volume maintenance and permit new bone formation to achieve osseointegration after implant placement.

Sinus lift with simultaneous implant placement has been reported with higher failure rates.[10] Osseointegration of implants is achieved better in implants placed with good primary stability. Primary stability on the other hand is influenced by the available quality and quantity of bone in the osteotomy site. Delayed implant was deemed successful as it allows adequate graft maturation, thereby providing more bone to implant contact and reduces the risk of failure.[11] Hence, in our study, delayed implant placement was executed due to inadequate initial bone height and also to allow enough graft maturation.

CONCLUSION

The presented technique might represent a viable alternative to conventional sinus lift in atrophied edentulous posterior maxilla, and irradiated cancellous bone allograft serves a suitable graft for sinus augmentation procedures.

However, the results of the study need to be validated with a larger sample size as the outcome of the treatment may get influenced by various anatomical-, prosthetic-, surgical-, and patient-related factors.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.