A Combined Lateral-Crestal Approach of Sinus Floor Elevation: Three Case Reports

Sinus floor elevation was first introduced in the 1970s by Tatum¹  and has become one of the most reliable approaches for bone augmentation. Initially, sinus floor elevation is performed by creating a lateral window, which provides a good vision for dentists to elevate the Schneiderian membrane and guarantees the success of this technique.²  However, the large flap and the preparation of the lateral window in this approach causes more trauma to patients.

In 1994, a crestal approach termed as osteotome technique was proposed by Summers.³  Compared with the lateral approach, the crestal one is less harmful and less time-consuming as the lift process is carried out through the implant bed.⁴  However, the lift height is limited and once membrane perforation occurs, it is not easy to repair it.^5,6 

In this clinical report, we propose a modified lateral-crestal sinus floor elevation technique to combine the merits of the lateral and crestal approaches.

Three clinical situations with 6 missing teeth at the maxillary posterior area are presented. To replace these teeth, a combined lateral-crestal approach for sinus floor elevation was used, and the procedure of this technique is shown as follows:

1. Under local anesthesia, make a mid-crestal incision and raise a full-thickness mucoperiosteal flap.

2. Locate the sites of the planned implants and prepare the sites to a distance of less than 1.0 mm from the sinus floor.

3. Buccally enlarge the osteotomy to the lateral side of sinus floor and remove the remaining sinus floor using the diamond bur with caution (Figure 1a).

4. Elevate the sinus membrane with different curettes (Advanced Sinus Kit; Dentium) from various angles. Surgical curettes can contact the underlying bone because of enlarged osteotomy (Figure 1b).

5. Test the sinus membrane for perforations with the Valsalva maneuver.

6. Fill the preparation with the grafting material. Place implants and cover the exposed osteotomy site with a resorbable membrane (Figure 1c).

A 50-year-old man presented with the loss of the maxillary right second premolar, and the first and second molars (Figure 2a). A fixed prosthesis was removed due to failed root canal therapy of 2 abutment teeth 3 months ago. A cone beam computerized tomography (CBCT) scan showed a residual bone height (RBH) of 2.0–3.0 mm and alveolar bone width above 10.0 mm in the first molar region (Figure 2b and c).

After a midcrestal incision (Figure 3a) and a full-thickness mucoperiosteal flap (Figure 3b), a buccally enlarged osteotomy was made with a diamond bur at the first molar site (Advanced Sinus Kit, Dentium) (Figure 3c and d). The sinus membrane was elevated by different curettes from various angles (Advanced Sinus Kit, Dentium) (Figure 4). Sinus membrane at adjacent implant sites was elevated with traditional Summers technique. Without the perforation of sinus membrane, the preparation was filled with grafting material (Bio-Oss, Geistlich Biomaterials) (Figure 5a). Then, the implants were placed (4.5 × 8 mm, 5.0 × 10 mm, 5.0 × 8 mm, Dentium) (Figure 5b and c), and the osteotomy was again filled with grafting material (Figure 5c), followed by coverage of a resorbable membrane (Collegen Membrane, Dentium) (Figure 5e) and finally suture of the flaps (Figure 5f).

Postoperative panoramic X ray showed that sinus membrane was elevated for 8.0 mm (Figure 6a). After 6 months, healing of implants and bone grafts without abnormalities was demonstrated in CBCT scan (Figure 6b and c) and restorations were delivered later (Figure 6d and e). In the 1-year follow-up, the implants functioned very well (Figure 6f).

Transalveolar sinus elevation was performed in a 40-year-old woman with loss of the first right maxillary posterior molar that had resulted in about 3.0 mm of RBH (Figure 7). The modified approach to crestal sinus elevation was carried out as described already (Figure 8). The small lateral window provides a better view for practitioners and more convenient access of surgical curettes. An implant (5.0 × 10 mm; Osstem) was placed, followed by the filling of bone grafts (Bio-Oss, Geistlich Biomaterials) (Figure 9a through c), and a resorbable membrane (Bio-Gide; Geistlich Biomaterials) was used to cover the exposed osteotomy (Figure 9d). Postoperative CBCT showed that the sinus membrane was elevated for over 7.0 mm, and the implant was well positioned (Figure 9e and 9f).

A 42-year-old woman presented with the loss of 2 right maxillary molars with RBH of 2.0–3.0 mm (Figure 10). Two buccally enlarged osteotomies were made, and the sinus membrane was safely elevated with the modified transalveolar approach (Figure 11). To avoid perforation of sinus membrane during implant insertion, elevated height at 2 sites was measured with caution before 2 implants (5.0 × 8 mm; Dentium) were inserted. Postoperative panoramic radiography showed that the sinus membrane was elevated for approximately 6.0 mm (Figure 11h).

The success rate of sinus lift has been reported to be high.^7,8  However, complications such as swelling, membrane perforation, graft migration, and even implant failure still exist.⁷  Many factors can result in complications, such as decreased RBH, prolonged surgery time, wide alveolar ridge, and large size of the elevated area.^9,10 

In cases with RBH less than 3.0 mm, a lateral sinus floor elevation technique is usually recommended because of the good vision and sufficient operation space it can provide.¹¹  However, the traditional lateral sinus elevation technique can cause more damage to soft and hard tissues and usually means prolonged surgery time. To decrease complication rate after sinus lift, the present case reports a lateral-crestal sinus elevation approach for severely atrophic alveolar bone.

In this approach, an osteotomy from the crestal to the buccal side was prepared with a diamond bur, which is known to cut only the hard tissue. To avoid perforation of the sinus membrane, an accurate CBCT data was necessary for the choosing of drill stop with proper size. Except the preparation of the osteotome, the remaining procedures were similar to those of a conventional lateral approach, including membrane elevation, grafts placement, implant placement, and osteotome coverage with absorbable membrane.¹²  All patients in this study reported only mild swelling compared with the lateral approach because of the minimal flaps in the procedure.

This combined lateral-crestal approach is recommended in cases with RBH less than 3.0 mm and those with wide sinus floor at the lateral-medial direction. Moreover, primary stability should be a concern when choosing this technique.

To conclude, this technique is a combination of the lateral and crestal sinus lift approaches. Schneiderian membrane can be elevated safely to a higher level with hand curettes compared with the traditional Summers approach.

Abbreviations

CBCT:

cone-beam computerized tomography

RBH:

residual bone height

The authors acknowledge financial support from the Graduate Student's Research and Innovation Fund of Sichuan University (2018YJSY107).

The authors declare no conflict of interest.