## 4 Discussion
The results indicated initially prolonged period of acquiring secondary stability of the implants in the first weeks after implantation. However, at 12 weeks post-surgery, the differences between smokers and non-smokers were not significant, which is consistent with our observations [11]. Sayardoust on the other hand showed that the stability of implants in smokers was significantly higher than in non-smokers on the day of implantation, and 1 day, 7 days, and 14 days after surgery. However, 28 days post-surgery the difference between these two groups of patients was not significant [14]. Smoking has a negative effect on bone metabolism, it impedes normal function and proliferation of the alveolar bone marrow mesenchymal stem cells. A study by [PERSON] et al. revealed that these changes were also correlated with disturbances in osseointegration and lower stability of the implants among smokers from the 3 rd to the 6 th week after surgery [12]. Due to the different surgical techniques (closed healing) used in our study, the implants were unavailable for examination due to the ongoing healing process during the first few weeks after surgery. Upon measuring the implant stability 6 months post-implantation,we found no significant differences in implant stability growth dynamics, which is in line with the abovementioned research. One of the limitations of the current study involves the use of indirect methods of stability assessment. ISQ index, despite a strong correlation to the magnitude of implant micro-mobility, is not in complete agreement with it [35]. Measurement of the absolute micro-mobility value may have provided more precise information regarding the quality of the bone-implant interface and might have given a broader image of the osseointegration process in smokers. To date there are no devices available that could be used in a clinical setting to assess actual micro-mobility. Implant stability is affected by a multitude of factors of biological, mechanical, and technical nature. In our study, parameters including age, implant diameter, implant length, angulation of implant in mesio-distal and bucco-palatal dimensions, torque and marginal bone loss were recorded. In the aesthetic area, the depth of the alveolar socket, drilling depth, and level of implant embedment in the bone were additionally assessed. Each of the parameters was separately evaluated for correlation to results of stability measurements to control for potential confounding of the research outcome. The study by [PERSON] et al. proved that implant stability measurement by means of resonance frequency analysis is suitable for predicting the risk of implantoprosthetic treatment--the survival rate was correlated with ISQ measurements. Additionally, all of the failures that were recorded occurred when ISQ was less than 67 at the time of implant loading [36]. In our study, the mean implant stability in smokers on the day of implant loading was below that level in both the posterior and anterior regions. Although a survival rate of 100% was achieved over a 2-year observation period, the significantly lower implant stability observed in smokers may be viewed as a factor affecting the long-term prognosis of the implants in that group of patients, thus procedures with a higher failure risk, such as immediate or early implant loading should be used with caution, especially in the presence of other risk factors [36; 37]. Implant stability measurements performed before implant loading may help avoid this condition, where the threshold implant stability level, necessary for a proper osseointegration process, would be exceeded. Many of implants were inserted in angulation forced by alveolar native bone presence. This is why in lots of cases the technological hole for screwing on superstructure projected onto the labial wall of the crown. It was unacceptable especially in aesthetic region. This is why cemented superstructures were administered to all patients to avoid variation in results.