# Crystal Sinus Lift with the Hydrodynamic Technique: Prospective Clinical Study at 3 Years Follow-Up
## 2 Materials and Methods
### Clinical outcomes  
1. The Implant Survival Rate  
The implant survival rate was assessed based on the number of implants lost during the follow-up period due to mobility associated with progressive marginal bone loss, typically caused by peri-implantitis. Implant loss was classified by the period of occurrence: if it occurred within 6 months of fixture placement, it was termed early failure; if it occurred after 6 months, it was termed late failure. Early failures were usually identified at the reopening stage due to a lack of osseointegration. Late failures were characterized by signs of peri-implantitis, implant mobility, radiolucent areas around fixtures, mucosal supuration, and/or pain during the follow-up period. 2. Marginal Bone Loss (MBL)  
Marginal bone loss was assessed at 6 months, 1 year, 2 years, and 3 years post-surgery using digital phosphor intraoral radiography. To assess marginal bone trends, measurements were performed only after image calibration. Digora 2.5 software (Soredex, Tuusula, Finland) was utilized for analysis, employing a specific measurement tool. Calibrations (pixels/mm) were performed using the implant diameter as the known unit. Changes in the height of the peri-implant marginal bone relative to the most coronal part of the implant and the point of contact between the implant and the marginal ridge were measured. A line passing over the shoulder of the implant was used as a reference for measurement, from which a straight line was drawn parallel to the long axis of the implant to the most coronal point where the bone met the fixture both mesially and distally (Figure 6). The software tool we used automatically provided the distance between these points in millimeters. To minimize human error, three operators performed the measurements, and the average was considered. Mesial and distal measurements were taken, and the averages for each implant site (MBL) were calculated. 3. Surgical Complications  
Surgical complications were categorized based on the procedure performed. Potential complications included sinus membrane perforation, maxillary sinusitis, graft material displacement, excessive bleeding, infection, and insufficient lift of the sinus floor. Additionally, there could be complications such as pain, swelling, and hematoma formation at the surgical site. **Follow-up**  
Follow-up visits were conducted one-week post-surgery, then at 3 and 6 months, followed by annual check-ups for the next three years. Professional oral hygiene sessions were scheduled every four months after the surgical-prosthetic procedure [26; 27; 28]. **Statistical analysis**  
Figure 6: Mesial and distal measuring lines (orange) connect the peri-implant marginal bone and implant neck. The collected data were analyzed using SPSS software (Version 25.0, IBM Corp., Armonk, NY, USA) to evaluate the implant survival rates, MBL, and surgical complications. Kaplan-Meier survival analysis was performed to estimate the implant survival rate over the follow-up period. A repeated measures ANOVA was used to analyze changes in MBL over time. Pairwise comparisons were conducted to assess differences between specific time points. The incidence of surgical complications was summarized using descriptive statistics. Chi-square tests were employed to compare the complication rates between different time intervals. A \(p\)-value of \(<\)0.05 was considered statistically significant. _Null Hypothesis (H0)_: There are no significant differences in implant survival rates, marginal bone loss, or the incidence of surgical complications in patients with single dental implants placed in the atrophic posterior maxilla using the transcrestal sinus lift procedure with injectable graft materials. _Study size_: The sample size determination was based on a statistical power analysis using a \(t\)-test for two independent samples. We targeted a significance level (\(\alpha\)) of 0.05 and a power (\(1-\beta\)) of 0.80, reflecting a commonly accepted balance between Type I and Type II errors.