Although the lateral sinus floor elevation is a proven clinically successful technique [14], the indirect SFE approach is favorable among clinicians because it does not require a second surgery site and hence cause less trauma and discomfort for the patient [14,15,16]. However, this method has its drawbacks, such as a higher risk of membrane perforation, a decreased space for using surgical instruments, and limitation in elevation heights when using the conventional techniques [3, 16, 17].
The osteotome technique originally described by Tatum 1994 has been shown microscopically to elevate the sinus floor for 5 mm without causing perforations [18]. Thus, this technique should not be used when the intended elevation height is more than 5 mm [19]. Therefore, a need for transalveolar approach that can elevate the membrane safely and for elevation heights greater than 5 mm has risen, Tatum described a modified approach to his osteotome technique in which bone particles are pushed in the sinus. The addition of bone will prevent direct contact between the instruments and the membrane [20]. Recently, many methods for SFE have been described as an alternative for the osteotome technique. Most of this techniques fall under two categories: using an inflatable device such as a balloon or using hydraulic pressure, both of which have been shown to reduce the rate of membrane perforation [6, 7, 13, 21, 22]. Soltan and Smiler described the use of the balloon and concluded that it is a highly successful and easy to perform procedure [6]. Recently, many systems have been developed which rely on hydraulic pressure to lift the sinus mucosa including the Jeder-System (Jeder GmbH, Vienna, Austria) which consists of a drill with a chamber which is filled with saline solution. After the initial drilling is done, the drill is connected to a pump that produces high hydraulic pressure; the pressure is used to break the sinus floor and to lift the membrane [23]. Also, OSSTEM implants introduced the CAS kit as a method for preparing the osteotomy and elevating the membrane through hydraulic pressure.
Using a reamer instead of the osteotomes for breaking the sinus floor has the advantage of creating a thin bone shell that prevents direct contact between the drill and the Schneiderian membrane [24]. Moreover, using a reamer has been shown to cause less discomfort and nausea when compared to the osteotome technique as a result of the constant tapping of the osteotomes [25]. As a result, the CAS kit has the advantage over the BAOSFE and the balloon in preparing the osteotomy and breaking the sinus floor safely and with less complications. Moreover, it was noted during our study that using a drill gives better feedback to the surgeon when breaking the sinus floor compared to the osteotome.
However, in our study, the CAS-kit was able to lift the membrane for a maximum of 5 mm. We believe that the saline pressure injected through the hydraulic lifter from a syringe is small and decreases gradually after leaving the lifter, whereas a study on the Jeder system showed a height gain of (9.2 ± 1.7 mm). This could be attributed to the high hydraulic pressure from the Jeder pump which is a machine that control the hydraulic pressure [23]. On the other hand, in our study, the balloon was able to lift the membrane for 7 mm in all cases; therefore, the balloon was better in elevating the mucosa.
Our study compared between three techniques for SFE for elevation heights of 7 mm. The 7 mm elevation height was chosen as a previous study by Stelzle et al. 2011 showed that BAOSFE caused perforations in the mucosa in all samples for perforation heights of 10 mm [7]. Therefore, we tried to set a threshold that might be achieved with internal sinus lifting techniques and be feasible in clinical practice. Perforations were checked using the three different methods: the mesial window, using a depth gauge, and the injection of saline solution through the osteotomy, which allowed for accurate recording of perforations.
The BAOSFE technique caused perforations in the membrane in 7 out of 12 cases with a percentage of 58.4. This result is consistent with many previous studies which state that this technique has a high rate of perforations when the RBH is less than 5 mm [2, 7, 26]. Also, all the perforations happened during the elevation process; however, this percentage is different than that reported by Steltzle (100%) in a similar study as the intended elevation height was less by 3 mm in our study [7].
For the balloon technique, only one perforation happened during the elevation process and the balloon was able to lift the membrane for 7 mm in all successful cases. This result supports various studies that showed a high success rate for this technique [6, 7, 13]; however, the osteotomy should be enlarged to 5 mm before inserting the balloon and this might limit the indications for this technique in thin ridges.
The CAS kit caused perforation of the Schneiderian membrane in one of the 12 cases (8.3%) which happened during the osteotomy. This is the first study to our knowledge to assess the CAS kit form OSSTEM implants since we found one published article that was a questionnaire sent to dentists who used the system to assess their satisfaction with the CAS kit, The study reported a membrane perforation rate of 4.1%. This percentage is smaller than that reported in our study (8.3%); however, we believe that our method of checking perforations is more accurate. Also, the difference in sample size may have contributed to the outcome [5].
