A retrospective study of patients who underwent osteotome sinus floor elevation at Srinakharinwirot University or Theptharin Hospital between May 2017 and May 2018 was undertaken. The study was approved by the ethical committee for research in human subjects, Number DENTSWU-EC22/2560 the faculty of Dentistry, Srinakharinwirot University, Thailand. All patients signed an informed consent before being enrolled in the study.
The patient inclusion criteria for this study are as follows: OSFE procedure was performed without grafting material at posterior maxilla region 6 months prior to the start of the study; there was CBCT imaging for assessment of the bone level pre-operation; RBH was ≥ 5 mm at the planned implant site; no history of sinusitis before implant placement; either no underlying disease or the disease is well controlled by the personal doctor; non-smoking patient or smoking cessation at least 1 year; available and detailed implant records, including the implant brand, diameter, length, and the protrusion length; no alcohol addiction; and the use of prosthetic reconstruction using single-implant, single crown restorations that had been fitted within the 4- to 6-month period after implant placement.
The patient exclusion criteria for this study are as follows: patients with sinusitis symptoms and patients who had worn denture on the implant site during the healing period. Twenty-seven patients, with 31 implants, met the enrollment criteria of the study.
CBCT was used to assess bone height and morphology at all implant sites prior to surgery. CBCT was performed again 6 months after surgery. The images were obtained with the WhiteFox® (Acteon Group, Mérignac, France) with the field of view set at 200 × 170 cm and 0.3 mm3 voxel size. The preoperative CBCT images were used to determine the treatment protocols for OSFE without grating and simultaneous implant insertion.
Surgical procedure guidelines provided by each of the brand manufacturers (Astra Tech®, Straumann®, Osstem®) were performed under local anesthesia. Thirty-one implants were placed in the posterior region of maxilla using a submerged technique and with one stage surgical procedure. Following a 3–4-month undisturbed healing period, prosthetic treatment for each was undertaken in line with the implant manufacturer’s guidelines.
For pre-operative patient preparation, 1-h prior to surgery, all 27 patients had to orally take an antibiotic drug consisting of 1 g of amoxicillin. Immediately before surgery, all patients rinsed their mouth with 0.2% chlorhexidine solution for 30 s. Local anesthesia was administered in the buccal and palatal regions of the surgical site. Following a mid-crest incision without a releasing incision, a full-thickness mucoperiosteal flap was raised. A round-shaped bur was initially used to mark the implant position. Following a review of the preoperative CBCT scan, minimal pilot drilling (Ø2.2 mm) was performed to a depth approximately 1 mm from the sinus floor. The manufacturer’s guidelines were then followed, gradually increasing the drill diameter until the final diameter drill was used to a depth 1 mm from the sinus floor.
The elevation of the maxillary sinus was developed using the manufacturer’s osteotome instructions at the final drill diameter. Light malleating was performed to achieve the sinus elevation with osteotomies of gradually increasing length until the final depth was achieved. All implants were placed in sites using a submerged technique and using a single-stage procedure.
Standard aftercare treatment was provided following implant placement with the osteotome technique. Rinsing of the mouth with a 0.12% solution of chlorhexidine for 60 s, 2 times a day, for 7 days was prescribed. Anti-inflammatory drugs (ibuprofen 400 mg) 3 times per day were also prescribed with antibiotics (amoxicillin 1 g) to be taken twice daily for 5 days following surgery.
To establish if there was continued radiolucency around the implant body, a periapical radiograph for each patient was taken after a healing period of 3–4 months. Dental impressions were then taken and approximately 2 weeks later, prosthetic abutments were inserted and final restorations were completed. Each implant supported a single crown.
Six months after implant placement, patients were fully informed of the study and signed to confirm their consent to participate. In month 6, the oral examination was performed and CBCT measurements were taken. Any symptoms and complications following surgery regarding sinus infections were recorded
The success criteria proposed by Buser et al.  were used including (1) the absence of clinically detectable implant mobility, (2) absence of pain or any subjective sensation, (3) absence of recurrent peri-implant infection, and (4) absence of continuous radiolucency around the implant.
Analysis of the CBCT imaging
A comparison was made between the preoperative CBCT radiographs and the 6-month postoperative CBCT radiographs. CBCT image analysis was performed with the WhiteFox® imaging software version3.0. The “measure” tool in the software was used for the linear measurement of the bone height between the time intervals analyzed. The radiographic parameters were analyzed by a single dentist on two occasions 1 week apart. The intra-examiner agreement was compared and shown to be good, and the intraclass correlation coefficient (ICC) was 0.94 (p ≤ 0.05). All measurements were expressed in millimeters.
In the CBCT images at 6 months after surgery, the center of the measurement tool was positioned at the center of the implant site (Additional file 1: Figure S1). This location in the maxilla was recorded and used as the reference location for the preoperative CBCT images. The maxillary anatomical structures surrounding the implant were referenced when aligning the coronal, sagittal, and axial planes to ensure consistent measurement positions (Additional file 2: Figure S2). Measurements were performed in the coronal and sagittal views of CBCT images. Key radiographic parameters (residual bone height and new bone level) were recorded as previously described .
Briefly, the residual bone height (RBH), measured from the preoperative CBCT images showed the vertical distance from the cortex bone under the floor of the maxillary sinus to the alveolar bone crest. The new bone level from the 6-month postoperative CBCT images was measured vertically from the most coronal to most apical of the bone-implant contact area. The vertical bone level at the buccal and palatal sites was measured from the coronal views while those at the mesial and distal sites were determined from the sagittal views of the CBCT images. The mean new bone levels were assessed from the coronal (buccal-palatal) and sagittal (mesial-distal) views of the 31 implant sites at 6 months after the OSFE. The endo-sinus bone gain was then calculated by subtracting the preoperative RBH distance from the postoperative new bone level. A positive outcome would demonstrate a gain of new bone in the sinus.
SPSS software version 20.0 (SPSS Inc., Chicago, IL, USA) was used to analyze all data. Descriptive statistics included the mean and standard deviations (SD) to assess the RBH, new bone level, implant protrusion length, and endo-sinus bone gain. The paired t test was used to compare the RBH and new bone level between preoperative and 6 months postoperative CBCT imaging. The Pearson linear correlation coefficient between two independent parameters was calculated for the protruding implant length and the endo-sinus bone gain. One-way ANOVA and post hoc test (Turkey HSD test) were used to compare the differences in endo-sinus bone gain and implant protrusion length between the 3 dental implant systems. The p values < 0.05 were considered to be statistically significant.