Use of Implant-Derived Minimally Invasive Sinus Floor Elevation: A Multicenter Clinical Observational Study With 12- to 65-Month Follow-Up

The posterior maxilla is a challenging site for implant placement owing to anatomical limitations and inherent poor bone quality.¹  Atrophy of the alveolar crest and pneumatization of the maxillary sinus limits the quality and quantity of the residual bone, therefore complicating the placement of implants in the posterior maxillary area.^2,3  Various classifications have been established to determine the most appropriate treatment based on the pattern of alveolar resorption: Misch⁴  established 4 groups in function of the bone height existing between the free margin of the alveolar process and the floor of the maxillary sinus. In 2009, Chiapasco and Zaniboni⁵  established another classification according to the height and width of the alveolar ridge and the intermaxillary relationship of the patient. The need to increase bone volume has led to the development of maxillary sinus augmentation procedures.⁶ 

The osteotome maxillary sinus floor elevation is generally employed when the residual bone height is equal to or greater than 6 mm;¹  in cases with higher resorption, the direct sinus elevation technique is usually used.^1,3  The indirect osteotome technique offers a number of advantages: the surgery is more conservative, sinus augmentation is localized, there is a low rate of postoperative morbidity, shorter time to implant loading is possible than with the direct technique, and high survival rates of around 90% were obtained in previous reports.^6,7 

Maxillary sinus floor elevation via a lateral approach, though a predictable technique to increase bone volume of the edentulous posterior maxilla and consequently for dental implants placement, have presented higher postoperative complications and morbidity as well as some challenges such as septa and the alveolar antral artery.^8–10 

The recently developed implant-derived minimally invasive sinus floor elevation system is a dental implant that enables the dental surgeon to perform a minimally invasive sinus floor elevation procedure. The key feature of this sinus lift implant is an internal channel that allows the clinician to introduce fluids into the maxillary sinus through the implant itself.

A recent pilot clinical study aimed to evaluate the patient's perception of immediate postoperative recovery after sinus augmentation, using the minimally invasive implant device, showed that pain, oral function, general activity, and other symptoms were mostly scored “not at all” or “very little” from postoperative day 1. The authors concluded that the results offer a preliminary indication that patients undergoing sinus augmentation using a minimally invasive implant device can expect to experience minimum discomfort and immediate return to everyday activity.¹¹ 

The aim of this multicenter study was to evaluate the performance of implant-derived minimally invasive sinus floor elevation in ossoeintegration as well as its ability to raise the sinus floor and create suitable bone for dental implant placement.

A multicenter retrospective study was performed in 5 dental clinics. Patients requiring single implant placement in the posterior maxilla with deficient bone height due to the presence of the maxillary sinus were recorded and followed up. Different surgeons performed the surgeries in this multicenter study and they calibrated for the surgical technique and the data recording and collection. The dental implant used in this trial was a self-tapping endosseous dental implant that contains an internal channel to allow the introduction of liquids through the implant body and into the maxillary sinus (iRaise, Maxillent Ltd, Herzliya, Israel; Figure 1). The device was approved for clinical testing by the ethical committees of the Israeli Ministry of Health and the Romanian Ministry of Health. Study participants were healthy volunteers who required a sinus floor augmentation. Participants were screened for inclusion/exclusion criteria at enrollment and signed an informed consent form according to the ethical committee approval.

Inclusion criteria included healthy participants at the age of 18 years or above, the need for sinus floor augmentation, residual bone height of between 2 and 7 mm, at least 3 months following tooth extraction, and healthy radiographic sinus appearance.

Exclusion criteria were poor oral hygiene, acute infection, acute or chronic sinus pathology, history of a sinus augmentation, and alcohol or drug abuse.

The distance from the maxillary crest to a point 1 to 2 mm below the sinus membrane was calculated, using the preoperative radiographic imaging (Figure 2). Surgery was performed under local anesthesia, and a crestal incision, without vertical extensions, was made along the maxillary ridge.

The implantation site was marked with a small round burr, and an osteotomy was initiated with a 2-mm twist drill to a depth of 3 mm. The osteotomy opening was widened to 3.2 mm with a countersink drill. The osteotomy was then extended to the superior maxillary cortex, adjacent to the sinus membrane, with a flat-tipped drill. To reach the cortex accurately, the depth to the cortex was measured on the preoperative radiograph. In addition, an intraoperative radiograph with a metallic gauge was used as necessary to verify both angulation and depth with respect to the cortex. Further safety was afforded by the tactile sensation provided by the flat tip of the drill as it reached the denser cortical bone, resulting in a palpable increase in the drilling resistance. Next, a diamond-tipped drill was used to penetrate into the cortex to a depth of 1.5 mm, either eliminating it or significantly weakening it. At this point the implant was slowly inserted into the prepared osteotomy, until the tip of the implant contacted the sinus membrane, penetrating any remaining portion of the cortical layer (Figure 3). A saline syringe (0.9% sterile saline solution) was connected to the implant via the tubing port. Saline solution was gently injected through the implant and into the sinus. Typically, 2 to 3 cc of saline was required, depending on the size of the sinus and the required elevation. The saline solution was retracted back into the syringe and the saline syringe was disconnected from the tubing port. A syringe filled with a flowable bone graft was then connected to the tubing port (MBCP Gel, Biomatlante, Vigneux-de-Bretagne, France). This flowable bone graft gel is an alloplastic bone graft material consisting of a mixture of 40% hydroxyapatite and 60% beta tricalcium phosphate granules in a hydrophilic polymer solution. Biphasic HA and TCP allow for a resorption rate similar to that of human bone. The consistency of the products allows for the injection of the material through the tubing and the implant into the sinus floor under the sinus membrane. The desired volume of bone graft material was then slowly injected through the implant into the sinus. The bone graft syringe was subsequently disconnected from the tubing port and the applicator and tubing were both disconnected from the implant (Figure 4). The implant was fully inserted through the osteotomy into the bone graft until the coronal aspect of the implant was aligned with the maxillary alveolar crest.

Follow-up visits were recorded and reported (Figure 5). Data from the 5 dental clinics were collected and analyzed using descriptive statistics.

Overall, 37 implants were installed in 37 patients (15 females and 22 males). The age range of the patients was 37–75 (mean: 51.2 years). Two patients reported smoking. The average residual bone height prior to the procedure was 5.24 ± 1 mm. Of all cases, 25 implants replaced the maxillary first molar and 12 replaced the maxillary second premolar. All surgeries were uneventful with no apparent perforation of the sinus membrane. When mentioning the possibility of membrane perforation, there were 3 parameters assessed—the clinical visual (Figure 6) and tactile feel, the negative Valsalva maneuver, as well as the radiographic appearance of the bone graft in the elevated portion of the sinus. Also, when injecting saline solution into the sinus while the patient is lying in a supine position, water or blood will come out from the nose if there is a perforation. Implant diameter was 4.2 mm in 25 patients and 5 mm in 12 patients. Implant length ranged between 13 and 16 mm and the amount of bone graft ranged from 1 to 3 mL (average bone graft volume was 2.61 ± 1 mL). All patients underwent second-stage implant surgery. All exposed implants achieved clinical stability and were reconstructed using single porcelain fused to metal crown (Figures 7–11).

The mean follow-up time was 24.81 ± 13 months ranging from 12 to 65 months. All implant integrated and showed stable marginal bone level on radiographic examination. No adverse events were recorded during the follow-up period.

Bone loss occurs in the maxilla for varying reasons¹²  necessitating bone augmentation procedure for the placement of dental implants in the posterior maxilla. The long-term success rate of sinus floor elevations was found to be superior to that of other bone grafts such as onlay bone augmentation in the maxilla.^13–17  Implants placed in conjunction with bone regenerative procedures presented a satisfying survival rate in the long term.¹⁸  A variety of different techniques for sinus augmentation were described in the literature, some are more or less time-consuming, and expensive surgical techniques are described both with a lateral approach^19–21  and with transcrestal augmentations.^22–24 

The lateral approach seems to provide better security and rupture control compared with the sinus lift procedure but is more invasive and leads to an interruption of bone nutrition on a large scale by dissecting the periosteum from the bone in large areas.²⁵  The minimally invasive transcrestal techniques provide little or no control over possible ruptures of the sinus membrane.^25,26  On the other hand the indirect osteotome technique offers a number of advantages: more conservative surgery, localized sinus augmentation, a low rate of postoperative morbidity, shorter time to implant loading is possible than with the direct technique, and high survival rates of around 90% are obtained in previous reports in the literature.^1,27  A recent report had shown that even in less than 3 mm thick crest, a transcrestal technique can predictably be used with a long-term clinical and radiological outcome, giving patients excellent stability of the grafted material and healthy clinical results.²⁸ 

The hydraulic sinus condensation method, a variant of the osteotome technique, was described by Chen and Cha.²⁹  An osteotomy is initially drilled into the crestal ridge, and fluid pressure from the drilling instrument is used to gently separate the sinus membrane from the sinus floor. After the sinus membrane is raised, it is filled with bone grafting material and implants are placed. The present technique of the minimally invasive implant device was previously described by Better et al^11,30  and is focused on a device designed as a transcrestal sinus augmentation procedure based on a dedicated dental implant. The sinus elevation, bone augmentation, and implant placement are all performed in the same procedure. Taking into account the successful clinical outcomes and lack of adverse events, this multicenter study supports a high benefit-to-risk ratio. However, due to the relatively short follow-up time and the limited number of patients reported here, long-term studies with a larger cohort are warranted to reaffirm the results of this study. All the cases described were performed in healthy patients so it is expected the technique will work with thin healthy membranes. The hydraulic technique is well established in the scientific literature,^11,29,30  and the system described in the manuscript utilizes the hydraulic technique in a more convenient way for the operator. As in any technique, there is always room for continuous follow-up and evaluation.

A meta-analysis of the osteotome technique for sinus elevation concluded that short-term clinical success of implants placed with an osteotome sinus floor elevation seems to be similar to that of implants conventionally placed in the partially edentulous maxilla.³¹  The authors implied that prospective clinical trials are required to evaluate the long-term outcome of the traditional osteotome technique similar to what will be required for this modified osteotome technique. The present report partially answers the request for additional information about the osteotome sinus floor elevation predictability.

The presented method for transcrestal sinus floor elevation procedure can be accomplished using the dedicated dental implant that allows for hydraulic elevation of the sinus membrane and placement of a flowable bone replacement graft and dental implant placement all at the same time with minimal patient discomfort. Further long-term studies are warranted to reaffirm the results of this study.

The authors report no conflicts of interest related to this study.