Introduction

Implant placement in the posterior maxillary region is often compromised owing to anatomic limitations. Despite its more traumatic implications and the common need for a two-stage procedure, let alone the potential risk of graft infection and graft loss resulting in inability of secondary implant placement, the lateral approach has been reported to be the most frequently used sinus floor augmentation procedure.¹ This may be partly attributable to the consensus statement of the international sinus elevation conference which recommends a lateral approach involving bone grafting and a two–stage implant placement technique when the residual bone height is ≤ 4 mm.² Notwithstanding the predictability of the lateral approach, the crestal approach is considered to be more conservative and less invasive than the lateral approach.³ In addition to being a widely recognised surgical technique for sinus floor elevation, the crestal approach has been reported to reduce operative time and postoperative discomfort.³

Aims:

To outline the modified crestal sinus floor elevation technique and evaluate the success of simultaneously placed dental implants, over a five-year period, when the described minimally invasive single-stage technique is used in the posterior maxilla with residual ridge height ≤ 4 mm (Fig. 1).

Materials and Methods:

A novel surgical technique (Figs. 2a-2e) for single-stage crestal elevation of the maxillary sinus floor membrane and alveolar ridge augmentation, based on the osteotome technique, using a vascularized pedicle bone graft was developed for clinical cases when maxillary alveolar crestal bone height is ≤ 4 mm. To date, 72 dental implants (Astra, Sweden) have been placed at the time of crestal elevation in 48 non-smoking patients (Table 1). At the one-year and five-year review visits (Fig. 3) the augmented crestal bone height was measured and implant survival have was evaluated. Table 1. Gender and age distribution of patients.

Table 1

Results:

At the three-month implant exposure stage two implants in different patients had failed to osseointegrate and were removed. The one-year and five-year survival rates were 97,3% and 97,3% respectively. The risk of implant failure increased proportionally with decreased residual bone height and with increasing patient age. Statistical analysis (Chi-square test) had found no significant difference in implant loading and resulting implant failure at the one-year and five-year review visits (p=0.1). The range of augmented bone height was 2 – 14 mm (mean=8.2 mm). There was no significant difference at crestal bone to implant shoulder and no significant difference in augmentation height at the one-year and five-year review visits [chi-square test (p=0.525) and Fisher test (p=0.400)].

Surgical technique

A step-by-step illustration of the surgical technique is shown in Fig. 2. and is performed as follows:

Step 1: Flap Design A full thickness flap is raised from the palate and reflected to the buccal aspect of the alveolar crest.

Step 2: Preparation of crestal window A rectangular window is outlined on the crestal bone with osteotomes (Fig. 2a). The width of the window should be 2 mm narrower than the width of the implant that will be placed in the site.

Step 3: Mobilization and elevation of pedicled bone graft The outlined bone block is mobilized by diverting taps into the cancellous bone of the sinus walls and elevated using blunt osteotomes (Figs. 2b and 2c). The sinus membrane is peeled from the lateral sinus walls without contacting it directly in order to preserve its integrity. The attachment of the bone graft to the sinus membrane is spared in order to maintain its osteogenic potential and the integrity of the blood supply.

Step 4: Implant placement The implants are placed (Figs. 2d and 2e) ensuring that the implant diameters are wider than the osteotomy site in order to attain bone compression and primary stability. With the implants firmly in place the cover screws are inserted.

Step 6: Suturing The flap is repositioned with resorbable sutures to achieve tension – free primary wound closure over the implants.

Step 7: Postoperative care Appropriate antimicrobial medication, analgesics and mouthwash are prescribed, as required.

Step 8: Exposure of implants Following 3 months of submerged healing, the implants are exposed. All incisions should be made on the palatal aspect of the ridge to preserve as much keratinized tissue as possible. Subsequent to implant exposure, prosthodontic procedures are performed in the usual manner.

Conclusion

The presented single-stage technique is a minimally invasive approach for achieving large augmentation volume and simultaneous implant placement when alveolar crestal bone height is ≤ 4 mm. The very high success rate of the simultaneously placed implants over a five-year period is encouraging and it is suggested that this technique offers a viable alternative to implant treatment in the extremely resorbed posterior maxilla.