## 4 Discussion  
The long-term survival of implant-supported restorations depends on bone quality and quantity as well as implant dimensions [29; 30]. High-stress concentration areas in addition to high strain values owing to excessive implant loading are related to bone resorption [31; 30; 32; 33; 34]. Bone homeostasis is achieved, according to [PERSON]'s \"mechanostat theory\", when bone tissue responds favorably to the forces transferred through the implant and strain values fall between 1000 \(\mu\epsilon\) and 1500 \(\mu\epsilon\)[25; 26]. Bone remodeling occurs when strain values are in the 1500 \(\mu\epsilon\)-3000 \(\mu\epsilon\) interval, but above these values, the risk of bone resorption or even fracture rises significantly [25; 26]. The results of our study showed that, by virtually increasing bone mass and allowing for larger implants to be used, strain values decreased in both quadrants. Although strain values for both resorbed and bone augmented mandible were far under the lower limit of the bone homeostasis interval, the variability of muscle forces in current literature, as well as an additional effect of other masticatory muscles, must be taken into account [35]. Studies that have reported values above the lower limit of the homeostasis interval have used sections of the mandible bone and applied a set value of force directly on the abutment or, in some cases, on the ceramic upper restoration [36; 37; 38; 39]. This is considered an oversimplification in the analysis and, although it may show a trend of the strain values in the bone tissue, it may also lead to artifacts or unreliable results [35; 36; 37; 38; 39; 40]. Moreover, there is currently a high variability regarding the magnitude of forces applied directly on implant-supported restorations having a large influence of the strains exerted on the bone tissue [40]. In a study on the importance of input variables in mandible biomechanics analysis, where a complete mandible was modeled with a full dental arch, strain values reported were similar to those obtained in our study [35]. Our results also show that, after the simulated bone augmentation, there is a uniformization of the strain values between the two implant sites in each of the mandible quadrants. Figure 5: Maximum principal stress values and distribution in mandibular bone in the resorbed model for the third (**a**) and fourth (**b**) quadrant and the virtually bone augmented model for the third (**c**) and fourth (**d**) quadrant. Stress values in the bone augmented model exhibited the same pattern. This is because of the increase of implant diameter and length, as well as an increase in bone volume. Besides the dimensional factor of the implants, attention needs to be given to the virtually augmented bone dimensions. The increase of bone volume seems to minimize the position effect of the teeth on the strain values recorded in the bone tissue. The small differences that do exist in strain between each of the implant sites may be because of the position that leads to a specific physiological load [41; 42; 43]. This may suggest that, in the absence of bone augmentation, further consideration needs to be given to the placement of the implant in atrophic ridges. In the resorbed mandible model, higher stress values were obtained compared with the simulated bone augmented mandible model. Increasing the implant diameter from 3.3 mm/3.75 mm to 4.2 mm and the length from 8 mm/10 mm to 11.5 mm led to a considerable decrease in stress, as well as a favorable distribution at the crestal level. This is in accordance with several studies that suggest that increasing the diameter and length of the implant leads to lower stress values in the mandibular bone [35; 43; 44]. In our study, the distribution of stress was found to be similar in the resorbed and bone augmented ridge, as stress was concentrated at the crestal level. This is because of the difference between the elastic modulus of the cortical and cancellous bone.