Dental implants are a potential modality for prosthetic replacement due to their high success rates and functional effectiveness in sites with adequate bone volume and density for implant biointegration.^[1] The residual ridge resorbs most quickly in the first 6 months.^[2] Due to the loss of alveolar bone, reduced bone density, and pneumatization of the maxillary sinus, restoring the posterior maxilla remains challenging.^[3,4] To prepare the region for implant placement with pneumatized sinus in the posterior maxilla and resorbed alveolar ridge an increase in the bone volume by sinus elevation is required.^[4,5] Transcrestal indirect sinus elevation (TISE) technique is effective when residual bone height (RBH) is >5 mm. In contrast, RBH <5 mm typically recommends a lateral approach for sinus floor elevation (SFE).^[6] Osteotome-mediated SFE, a TISE technique first described by Summer in 1994, has proven to be a less invasive, less time-consuming procedure. It can increase the ridge height by 3–5 mm, enabling simultaneous placement of implants.^[6,7] However, this method has some shortcomings, i.e., the use of explosive force that is challenging, leading to membrane perforation, inadvertent displacement of fractured fragments, and benign paroxysmal vertigo.^[8] The intralift, hydraulic sinus lift, autologous core lift, and indirect sinus lift utilizing calciumphosphosilicate putty were eventually developed for safely elevating the sinus membrane.^[2,9,10]

The Crestal Approach Sinus kit (CAS-KIT) was created specifically to elevate the maxillary sinus membrane transcrestally safely. The CAS-Drill is a vital part of the CAS-KIT because it improves the simplicity and safety of maxillary sinus surgery by raising the membrane using a special stopper system to stop over-drilling into the sinus cavity.^[11]

A relatively new method for biomechanically preparing bone is osseodensification (OD). With a fluted densifying bur during the operation, rolling and sliding contact generates modest plastic deformation of bone, densifying the bone without heat elevation developed by Huwais et al.^[12] It is carried out using burs (DensahTM) that have been specially constructed for the purpose. By compacting autografting, the OD burs aid in the preservation and condensation of the bone during osteotomy site preparation, enhancing its mechanical stability and thus accelerating the transition to the restorative phase.^[13,14]

Evidence supporting the use of OD in TISE is extremely scant. In order to assess and compare the clinical and radiological outcomes of TISE and simultaneous implant placement using OD and CAS instrumentation, the current randomized, prospective, and clinical trial was designed. The null hypothesis of the study was “there will be no significant difference in clinical and radiological outcomes between the two methods (OD and CAS) for transcrestal sinus elevation and implant placement.”

All participants were selected from the outpatient pool of the Department of Periodontics and Implantology at Vishnu Dental College, Bhimavaram. The study was approved and ethical clearance was obtained from the Institutional ethical committee with Ref No: IEC VDC/2021/PG01/PI/IVV/14 and approved under Clinical Trials Registry-India (CTRI/2021/07/034791). The study was conducted following the Helsinki Declaration as revised in 2013. Written informed consent was obtained from all the participants. The entire study period was from March 2021 to December 2022.

The TISE in both CAS and OD groups was uneventful with no peri-operative or postoperative complications reported. After 1 year of follow-up, both groups showed good survival rates. In TISE without augmentation, the important determinant of implant success is achieving good primary stability. On intergroup comparison, the mean ISQ values are greater for the OD group immediately after implant placement than CAS group. The significantly better primary stability in the OD group is in accordance with the studies done by Elghobashy et al.^[16] and Arafat and Elbaz^[13] where the authors compared TISE using OD with osteotome sinus elevation. The mean ISQ values obtained by Elghobashy et al.^[16] and Arafat and Elbaz^[13] were 66.17, and 65.15, respectively, which were lesser than the present study. In the current study, implants of the standard dimension of 4.2 mm × 10 mm were used, whereas Elghobashy et al. used implants of varying lengths, i.e., 8–10 mm, based on the available RBH.^[16,17] Furthermore, in our study, PRF was used as a grafting material before the insertion of implants in contrast to the other two studies, which were done without any graft material. The use of PRF in the current study could have contributed to the higher ISQ values in both groups, as stated by Öncü and Alaaddinoğlu.^[18] Conventional osteotomy or other sinus elevation instruments use subtractive techniques to remove the autologous bone from the implant site. In contrast, OD results in bone compaction and, an increase in the implant-bone interface leading to improved primary stability and reduced micromovements, thus reducing the chances of implant failure.^[19-21]

At 3 months postoperatively, in both groups, mean ISQ values increased indicating an improvement in the bone-to-implant contact. The mean secondary stability values were considerably greater for the OD group. The results are in accordance with Arafat and Elbaz, (75.92 ± 2.94) and Hamdi and Hemd (71.8 ± 5.5), who have reported greater secondary stability in the OD group.^[13,22] Along with the intact, well-organized trabecular pattern surrounding the implant, the spring-back effect and elastic recoil of the bone on the implant and bone surface increased its initial stability and improved secondary stability.^[23] The bone particles in the walls of the osteotomy and in between the threads of the implant body could act as a bone growth initiator, which enhances secondary stability.^[24] However, the intragroup comparison showed no significant improvement in the OD group in the present study which is similar to the values of Hamdi and Hemd, who showed no statistical improvement in the OD group from baseline.^[22]

Rawat et al. reported a mean CBL of 0.43 mm at 3 months which increased to 0.60 mm at the end of 6 months, where they performed indirect sinus elevation using the osteotome technique and densahburs.^[1] However, the results of the present study suggest comparatively less CBL in both groups; it might be because of the simplified surgical technique with subcrestal implant placement and the use of specialized drills in both groups. In a similar study by Mamidi et al., an indirect sinus lift procedure was performed using a CAS kit, and PIEZO drills stated a mean CBL of 0.52, 0.57, and 0.72 mm on the mesial side and 0.38, 0.44 and 0.78 mm on the distal side at 3, 6, 12 months respectively.^[25] The results of the present study suggest that with the specialized drills, the amount of CBL could be reduced, favouring the OD group. Arafat and Elbaz, in a study, observed marginal bone loss after sinus elevation using osteotome and OD and observed greater CBL in the OD group (0.98 mm) compared to the osteotome group (0.93) with no statistical significance.^[13] The present study showed a lesser bone loss in the OD group which could be due to the preservation of the bone bulk, compaction of cancellous bone caused by viscoelastic and plastic deformation as well as the autografting of bone fragments along the osteotomy.^[23]

The present study showed the most significant ABG in the OD group which is in accordance with a study by Arafat and Elbaz, where he reported an ABG of 2.79 mm in the osteotome group and 3.33 mm in the OD group.^[13] The rationale for using graft substitutes in conjunction with sinus elevation is to keep the sinus membrane as high as possible, improve IS, and act as a space maintainer. Endo-sinus bone formation was seen in both groups due to the inherent osteogenic potential of the sinus membrane and surrounding bony walls. The increased bone formation without using bone grafts can be attributed to the osteogenic potential of the sinus membrane, which has innate osteogenic cells and the apex of the implant acting as a tenting screw to hold the membrane in its elevated position.^[5] The presence of collagen and bone bulk, along with autografted bone chips in the osteotomy walls and apical regions, act as nuclei for increased quantity and dense bone formation.^[23] In sinus elevation procedures, the sinus membrane has inherent osteogenic potential and makes a significant contribution to bone regeneration.^[5] The implant survival rate and new bone formation in nongrafted sinuses are comparable to grafted sinuses.^[26] In TISE, more implant protrusion into the sinus raises the probability of sinus membrane perforation, especially in procedures without grafting materials. In the current study, though no bone grafts were used A-PRF was used as a membrane to cover and protect the sinus membrane simply and efficiently which also acts as a space maintainer and provides an adequate scaffold for bone regeneration.

Surgical time was less for the OD group (69.00 ± 20.24) compared to the CAS group (87.00 ± 15.49), which is statistically significant. A study by Ibrahim et al., reported a similar reduction in surgical time for the implants placed using Densah burs which is in accordance with the present study.^[27] A study by Elsaid et al., showed lesser surgical time in the OD group.^[28]

The mean patient comfort (VAS) scores obtained in the present study were 8.6, and 8.5 in the CAS and OD groups, respectively. In a study by Ibrahim et al., a considerable difference in patient comfort was seen in favor of the densah group.^[27] In the present study, similar levels of patient comfort were observed in both groups, as both procedures were minimally invasive.

The current study showed that TISE and simultaneous implant placement using both the CAS and OD techniques are reliable, with good survival rates and can be used for implant placement in the atrophic posterior maxilla. However, the OD group showed slightly improved clinical and radiographic outcomes, which need to be assessed further with long-term trials to evaluate the success of implants placed.

Both CAS kit and OD burs are effective in the safe elevation of the sinus membrane transcrestally with minimal or no complications. The results of the present study favor the OD group in terms of greater implant primary, secondary stability, and minimal CBL. ABG with reduced operating time compared to the CAS group. However, in both groups, patients were comfortable during the entire procedure.