Transcrestal Sinus Augmentation With Simultaneous Implant Placement in 1 to 2 mm Residual Alveolar Bone: A Case Report

In the edentulous posterior maxilla, progressive sinus pneumatization and residual alveolar bone resorption due to various causes may lead to bone volume deficiency. Therefore, alveolar bone augmentation surgery is often a prerequisite to dental implant placement. In complex or advanced cases where the residual alveolar bone height is compromised (<5 mm) and sinus elevation is expected, the traditional surgical approach is an external maxillary sinus lift procedure (lateral window approach) that involves the application of bone graft materials. This grafting procedure is performed to create an appropriate osteogenic space for eventual implant placement.^1,2  However, the lateral window approach has several drawbacks, including (i) complicated procedures, (ii) relatively high costs, and (iii) postoperative complications such as pain, swelling, and hematoma.³  In contrast, the transcrestal approach, also known as an osteotome sinus floor elevation, brings many advantages. This approach is minimally invasive, easier to perform, and thus results in less postoperative discomfort. However, the conservative osteotome sinus floor elevation with its improved surgical techniques⁴  can only achieve a limited elevation height. The transcrestal approach with osteotomes may also lead to perforation of maxillary sinus mucosa and implant failure or complications such as headache and vertigo.⁵ 

To minimize or mitigate risks, various instruments designed for sinus membrane lifting have been proposed. In addition, the use of hydraulic pressure for sinus membrane elevation has been reported.^6–8  A newly designed device for the sinus lift procedure features a specialized drilling system that can drill down via the crestal approach to reach the sinus floor without damaging the sinus mucosa. A hydraulic lifter, which is connected to a syringe filled with saline, is used to raise the sinus membrane. This procedure and device allow the dentist to elevate the sinus membrane safely and place the implant immediately, thus avoiding unnecessary discomfort caused by a second surgery.

In this paper, a case is reported using hydraulic pressure for sinus membrane elevation via the transcrestal approach with simultaneous implant placement in a patient with less than 2 mm residual alveolar bone. The definitive prosthesis was placed 9 months after surgery. After 6 years of clinical follow-up, the treatment appears to be successful and, thus, a promising option.

A 61-year-old female presented with a missing upper left first molar (tooth #14). The tooth was extracted several years ago due to failed endodontic treatment and infection. No prosthesis had been placed. The patient was in good health, with negative history to tobacco use, hypertension, or other cardiovascular diseases. She also denied parafunctional habits. The patient was not taking any routine medications. A preoperative cone-beam computerized tomography (CBCT) showed no mucosa thickening or lesions in the left maxillary sinus. The sinus floor was flat with no stenosis of the sinus dehiscence. A residual bone with a height of approximately 1 to 2 mm and a width of 7 to 8 mm was found in the upper left first molar site/area (Figure 1). No periapical or periodontal lesions were found on the proximal teeth.

The patient was treatment-planned for sinus elevation surgery to increase the alveolar bone height through the transcrestal approach. A sinus elevation surgery to increase alveolar bone height through the transcrestal approach was treatment-planned. The hydraulic pressure technique with simultaneous implant placement would be used. After providing informed consent, the patient was given 1 g amoxicillin 1 hour prior to initiating surgery, and a 0.2% chlorhexidine digluconate solution rinse 5 minutes before surgery was performed. Articaine with adrenaline 1:100,000 was used as a local anesthetic. An incision was made along the palatal side of the alveolar crest at the site of the missing tooth. The incision was extended intrasulcularly at the cervical margins of the adjacent teeth. A full-thickness flap was reflected and carefully extended to fully expose the alveolar ridge.

Following the manufacturer's instructions, the twist drill with a stopper from the CAS kit (Osstem Implant Co., Busan, Korea) was used to safely drill through the alveolar crest (Figure 2a) until the pale blue sinus floor mucosa was observed at the appropriate depth. The size of the osteotomy was enlarged to match the intended implant width by using drills of consecutively increasing diameter. The hydraulic lifter was inserted into the osteotomy at the alveolar crest, and then saline was slowly injected and retrieved with a 1.0 mL syringe. This step was repeated to separate and lift the maxillary sinus membrane (Figure 2b). Mucosal integrity was probed and confirmed with a depth gauge. The elevated height of the sinus membrane was confirmed, and 2.5 mL of saline was injected to further elevate the sinus membrane. Meticulous care was observed to prevent the perforation of the sinus floor membrane.

Advanced platelet-rich fibrin (A-PRF) was prepared as described in what follows. During surgery, 2 glass-coated plastic tubes of the patient's peripheral blood were drawn (10 mL/tube) and the blood was immediately centrifuged at 1500 rpm for 14 minutes using the specific A-PRF centrifuge. The yellow clot, which was rich in platelet fibrin, was extracted (Figure 3a) and cut into pieces to obtain the autologous A-PRF.

Deproteinized bovine bone mineral (DBBM; Bio-Oss; Geistlich Pharma, Wolhusen, Switzerland) was mixed with the autologous A-PRF (Figure 3b). Next, the bone graft was delivered into the maxillary sinus through the transcrestal window and further condensed. An implant (4.8 × 8 mm; Dentis Implant Co., Daegu, Korea) was placed into the upper left first molar site using the DENTIS surgical tools, and primary stability was measured at 35 N. After the cover screw installation, the flap was closed with 4-0 resorbable sutures.

Postoperative instructions were given to the patient, who was also prescribed antibiotics and analgesics. The patient took 2 g amoxicillin (or 600 mg clindamycin if allergic to amoxicillin) every 8 hours (or clindamycin every 6 hours) in the first 7 days postoperatively. In addition, the patient received 600 mg ibuprofen twice a day for 3 days for pain management. Chlorhexidine gluconate (0.12%) was used daily as mouth rinse until 14 days postoperatively to prevent infection. Postoperative CBCT indicated sufficient bone graft surrounding the implant, which achieved an alveolar bone height of approximately 14.0 mm. Proximal to the apical point of the implant, the bone height was approximately 6.0 mm (Figure 4).

After 9-month healing time prior to the second surgery, the sagittal view of the CBCT scans revealed that the bone height was approximately 10.8 mm around the implant, and 2.8 mm at the apical point of the implant (Figure 5). The osseointegration of the implant appeared to be favorable. Then, the implants were submerged, and the healing abutment was placed. Two weeks after placement of the healing abutment, the implant stability quotient (ISQ) value was measured at 75. A final impression was taken and prosthetic treatment was initiated.

Nine months after sinus augmentation surgery and implant placement, the patient was satisfied with no implant mobility or signs of peri-implant soft tissue inflammation.

Radiographic evaluation at this time demonstrated adequate augmentation of the alveolar bone. No bone resorption was detected in the area surrounding the implant, and final implant stability was sufficient to support the definitive prosthesis. At the 3-year follow-up, the CBCT images indicated that the implant was surrounded by bone, without noticeable cervical bone resorption (Figure 6). At the 6-year follow-up, the patient presented with good oral hygiene with no complaint of discomfort. The CBCT images showed the implant was surrounded by bone. Moreover, the maxillary sinus membrane level was flush with the implant tip (Figure 7).

The success of implant placement in the resorbed posterior maxilla is typically dependent on the presented bone height and bone quality. In cases with severe bone height deficiency (the height from the ridge crest to the sinus floor is <3 mm), a sinus elevation procedure by lateral window approach may be required to increase the bone height during initial-stage surgery, which is followed by implant placement in second-stage surgery. However, the sinus elevation by lateral window approach is dependent on the skills of the surgeon and cost-intensive, and has a prolonged treatment period. It could also lead to more postoperative discomfort.

Controlled hydrostatic sinus elevation has been introduced and reported in numerous studies. Kim et al⁶  conducted a survey on 28 dentists who had experience in using the CAS kit for sinus lift procedures. Among them, 26 dentists (92.9%) were satisfied or very satisfied with the kit, particularly with its advantages of safety, cutting performance, and user-friendliness. The sinus membrane perforation rate was reported to be only 4.1% among the 924 implant cases included in their study. In addition, a study evaluating the clinical outcomes of 19 patients undergoing hydrostatic sinus membrane elevation by the crestal approach using a novel drilling system (Neobiotech, Seoul, Korea) found no sinus perforations or osseointegration failures.⁷  The implant survival rate was 100%, while the average augmented volume of the alveolar height was 5.81 ± 2.06 mm. Thus, this procedure may be considered advantageous because of the reduced risk of perforation and lesser time to perform the treatment. Wang et al⁸  presented a sinus lift procedure through the transcrestal window approach with delayed implant placement in a patient with 1 to 2 mm of residual alveolar bone. The 1-year follow-up showed that the treatment was successful with minimal postoperative discomfort.

Nevertheless, this novel procedure is also technique-sensitive and requires strict adherence to the treatment indications. An assessment of the sinus floor shape and sinus mucosa status is needed. In fact, Berengo et al⁹  pointed out that the anatomy of the maxillary sinus and the elastic properties of the sinus membrane are closely related to the maxillary sinus elevation height. In this present case, the sinus floor was flat, and the mucosa indicted no signs of thickening or inflammation. These pretreatment findings offer favorable conditions for use of the hydrostatic sinus elevation technique to achieve the ideal augmentation height. Whether the implant can be placed simultaneously or not is dependent upon the comprehensive consideration of the residual alveolar bone height and the intraoperative assessment of the initial implant stability.

A-PRF is the third generation of platelet concentrates developed after platelet-rich plasma (PRP) and platelet-rich fibrin (PRF). A-PRF offers several advantages: increased biological safety as it is extracted completely from the blood without use of anticoagulants or thrombin products; it involves a simple preparation process; it has a 3-dimensional structure that provides the precursor osteoblasts and fibroblasts with an ideal proliferation and differentiation environment; and it is rich in growth factors, which facilitate the healing of soft and hard tissues.¹⁰ 

At present, there is a trend in the clinical application of platelet concentrates in maxillary sinus elevation and periapical surgeries.¹¹  Khouly et al¹²  studied 100 cases of sinus augmentation through lateral wall approach using a combination of plasma rich in growth factors (PRGFs) and xenograft materials. The mean follow-up time of their study was 7.2 years and the cumulative implant survival rate was 90%. They concluded that the use of PRGFs in maxillary sinus grafts may be an effective and safe treatment option. Remarkably, platelet concentrates may also promote soft tissue healing^13,14  and reduction of postoperative complications such as pain, swelling, and hematoma.¹⁵  The successful use of platelet concentrates as the sole grafting material in maxillary sinus floor elevation without the use of other bone grafts has been reported.¹⁶  Meanwhile, PRF has been used in the treatment of cases with extremely limited residual bone height.¹⁷  Twenty-seven patients with 2 to 3 mm residual bone height underwent sinus floor elevation by the crestal approach, in which PRF was used as the only grafting material. Thirty-nine implants (19 hydroxyapatite and 20 sandblasted acid-etched implants) were placed. At 1-year follow-up, there were 4 to 5 mm mean average bone gains in both groups.

This article describes a sinus lift procedure through the transcrestal approach in a 61-year-old female patient presenting with 1 to 2 mm residual bone height. A specifically-designed bone drill was used to prevent the perforation of the sinus floor membrane. Then, the maxillary sinus mucosa was elevated by hydraulic pressure with the injection of sterile saline. The implant was placed simultaneously to prevent the possible discomfort of a second surgery. To obtain sufficient growth factors, the bone graft material was used in combination with platelet concentrate A-PRF to promote adequate new bone formation and long-term stability. Long-term follow-up affirms that the maxillary bone stabilizes at the apex of the implant, which indicates that the excessive use of bone grafting material may not make a difference in the final result. However, additional cases and long-term follow-ups are still needed to confirm this phenomenon.

Featuring a special drilling system and the use of hydraulic pressure, maxillary sinus elevation through the transcrestal approach with simultaneous implant placement can be successfully applied in selected cases with 1- to 2-mm residual bone height. Additional cases are necessary to further assess and confirm this beneficial and promising procedure.

Abbreviations

A-PRF:

advanced platelet-rich fibrin

CAS:

crestal approach sinus

ISQ:

implant stability quotient

No potential conflict of interest relevant to this article was reported.