Crestal endoscopic approach for evaluating sinus membrane elevation technique
© The Author(s). 2018
Received: 8 November 2017
Accepted: 20 March 2018
Published: 17 May 2018
Closed sinus lifting is a unique technique in being simple and less invasive (Summers, Compendium 15(6):698, 1994). However, it is blind to assess the safety of sinus lining during lifting without perforation. Previously, sinus membrane was assessed endoscopically in an invasive way. We aimed to judge clinically the sinus membrane integrity after crestal elevation by a direct simple less invasive endoscopic visual assessment through the crestal osteotomy site. To confirm undetected perforation, the sinus membrane was monitored dynamically by introducing the endoscope through a trephined opening in the lateral wall of the sinus (Nkenke et al., Int J Oral Maxillofac Implants 17(4):557–66, 2002).
Twelve patients suffering atrophic posterior maxillae ranging 3–5 mm bone height below the sinus membrane were included to perform closed sinus lifting with simultaneous immediate implant placement under direct endoscopic assessment.
The floor was lifted without perforation in 83.33% of cases. However, it varied according to its thickness. Minor perforations occurred in two cases (16.67%). Both perforations were detected from the crestal endoscopic view while one of them was detected from the lateral endoscopic approach.
Crestal endoscopic access gives better direct vision to the membrane than the induced opening in the lateral wall of the maxillary sinus. Moreover, it uses the same prepared osteotomy site without doing any extra procedures. Perforation depends on the thickness of sinus lining and its ability to stretch during elevation. Intact crestal sinus floor elevation can never be guaranteed under endoscopic monitoring especially with thin irregular membranes.
The evolution of closed sinus lift techniques since 1994  was proposed as a less invasive method for management of atrophic posterior maxillae . However, it is a blind technique that lacks the ability to confirm an intact sinus floor elevation without perforation and thus represented a real shortcoming . Various forms of osteotome lifters were designed to guarantee safe elevation of maxillary sinus membrane [4–8], but all failed to prove a non-perforated elevation during the actual lifting procedures. Previously, the endoscope was used to test the efficiency of the closed sinus lifting to detect the presence or absence of the perforation by doing a large window on the lateral sinus wall. The technique is considered an invasive surgery where another sinus surgery is required. Meanwhile, CBCT [9, 10] represented the most commonly used technique to evaluate the thickness of the membrane, but it is not sensitive enough to detect minor perforations. Thus, minor perforations can be escaped leading to implant failure. We used the crestal osteotomy to assess endoscopically directly the sinus membrane through the crestal osteotomy site of the implant.
Patients and methods
Twelve patients (4 males and 8 females) ranging in age from 25 to 60 years were included in the study. All patients have bone height ranging 3–5 mm below the sinus membrane. They all performed closed sinus lifting and simultaneous immediate implant insertion.
Group A (4 cases): includes membrane thickness less than 2 mm
Group B (8 cases): includes membrane thickness more than 2 mm
Descriptive statistics of membrane thickness and perforation rate
Mean ± SD (mm)
Percentage (%) (from total)
Perforation rate (%) (from total)
A (n = 4)
< 2 mm
1.30 ± 0.53
B (n = 8)
> 2 mm
5.87 ± 2.70
Flat: shallow thickening without well-defined outlines.
Semi-aspherical: thickening with well-defined outlines rising in angle of > 30° from the floor or the walls of the sinus.
Mucocele-like: complete opacification of the sinus.
Other mucosal thickening types or pathological findings.
All patients tolerated the procedure without major complications. Minor complications included postoperative swelling, edema, and pain that were managed by antibiotic and anti-inflammatory drugs. All implants were successfully osseo-integrated and loaded after about 6 months.
The floor was lifted without perforation in 83.33% of cases. The lifter was able to raise and stretch the sinus membrane safely. However, it varied according to the thickness of the membrane.
Chi square test showing perforation rate among different groups
X2 = 4.80
P (chi) = 0.03
Descriptive statistics, results of Kruskal-Wallis and Mann-Whitney U tests for comparison between membrane thicknesses of different morphologies
Mean ± SD (mm)
Perforation rate (%)
Flat (n = 4)
2.12 ± 1.45
Irregular (n = 4)
2.83 ± 1.64
Polyp (n = 4)
8.10 ± 1.64
Chi square test showing perforation rate by different morphologies
Flat (n = 4)
X2 = 4.80
P (chi) = 0.09
Irregular (n = 4)
Polyp (n = 4)
The membrane was successfully raised under direct endoscopic guidance. Regarding the elevation technique, the perforation was monitored in two cases (16.67%) under the extraordinary magnification of the endoscope. One case was early detected from the lateral approach, whereas both cases were detected from the crestal osteotomy site. Both cases were managed using PRF to seal the perforation. The implants were then immediately inserted without further complications.
There was a statistically significant relation between both groups in terms of their perforation liability, where the membrane thickness of less than 2 mm showed the highest rate of perforation (P = 0.008).
On the other hand, assessing the effect of membrane morphology pattern on the perforation risk revealed that the polyp type has the lowest risk of perforation, whereas the irregular type represents the most insecure pattern. There was a relation between different membrane morphology and perforation.
Crestal sinus lifting technique is a simple less invasive procedure. Nevertheless, it suffers a serious disadvantage of being a blind technique. Thus, perforation can easily occur without being detected which will lead to later implant failure especially when bone graft is added [1, 12–14]. We used endoscopic-assisted evaluation as a dependable method to assess the safety of the Schneiderian membrane elevation from the same crestal osteotomy site. Others used a more invasive technique by doing a window on the lateral sinus wall [15, 16].
Considering the relation between the membrane thickness and its perforation risk, our results showed a higher liability of perforation in membranes less than 2 mm thickness. Thus, we advocate that any membrane thickness less than 2 mm should not be elevated using a blind crestal osteotomy. Consequently, the membrane thickness should be precisely estimated using at least a preoperative CBCT prior to any anticipated blind elevation technique .
The use of lateral endoscopic approach [15, 17], despite being safe with minimal complications, can be substituted with the crestal one as in our study. The crestal endoscopic approach has some surpassed advantages. It saves the patient undue lateral bony osteotomy and membrane access perforation while using an already available access (crestal osteotomy site). An endoscope of 1.9 mm launched on 2.4 mm trocar can readily fit on the 3 mm crestal osteotomy width. Moreover, it gives direct magnification to the sinus membrane through the osteotomy site, and it is more precise in detecting almost microscopic perforations that may be even spared during lateral endoscopic examination. The raising of the sinus membrane in a closed approach proved to be a safe technique as long as there is appropriate membrane thickness more than 2 mm [5, 7]. The crestal elevation is not a technique and osteotome design dependent procedure, but it is rather a membrane structured dependent method. Endoscopic crestal evaluation represents a precise valuable and easy tool when routinely available as chair side equipment for detecting any perforations and hence modify decision making after lifting procedures.
We would like to express our gratitude to Ass. Prof. Hamed Gad for his clinical collaboration.
This research was carried out without funding.
Availability of data and materials
The data supporting our findings can be requested for free at any time.
SE carried out the surgical procedure and implant placement. KB did the endoscopy part. All authors read and approved the final manuscript.
Ethics approval and consent to participate
Faculty of Dentistry, Minia University ethics committee approved the study. All patients gave the consent to participate in the surgery.
Consent for publication
All patients approved for publications.
The authors Samy Elian and Khaled Barakat declare that they have no competing interests.
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