## 4 Apfr
### Regeneration of Soft Tissues and Bones  
When extracting an impacted tooth, it is often necessary to remove a significant amount of surrounding bone. Improper management of the post-extraction socket can lead to a significant loss of alveolar height after extraction, resulting in recession on the second molar in the distal/buccal region of the tooth. Therefore, in order to preserve the height of the ridge, the alveolus needs to be adequately protected, which is achieved with bone substitute materials, fibrin preparations derived from the patient's blood, or a combination of both.  
Three months after extraction, [PERSON] et al. [30] found no significant differences between the test side (with A-PRF augmentation) and the control side (without A-PRF augmentation). CAL (clinical attachment level) and GR (gingival recession) measurements yielded similar results. In conclusion, the authors of the aforementioned study did not discover any additional benefit of A-PRF over natural healing in terms of pocket shallowing, reconstruction of the connective tissue attachment and minimization of the recessions formed; a slight advantage in healing with A-PRF could be seen by analyzing data from different measurement points around the tooth at different times after extraction. Unfortunately, this benefit did not include improved bone healing.  
[PERSON] et al. [31] discovered a significant difference between alveolar healing using postoperative A-PRF and bone healing as gauged by measures of bone density using extraoral RVG imaging (performed on controls after 1, 3, and 6 months). The researchers found comparable improvements in soft tissue healing after A-PRF.  
The findings of the above in vivo studies do not seem to confirm the results of in vitro studies comparing L-PRF (low-speed centrifugation) and A-PRF+ (high-speed centrifugation) and L-PRF, A-PRF, and A-PRF+ in terms of content, including growth factors, which have been shown to have higher concentrations in A-PRF+ compared to L-PRF [20; 32].  
In 2019, [PERSON] et al. [33] confirmed the osteogenic effect of A-PRF+ in sockets after extraction. In a study on Beagle dogs with removed premolars, the researchers observed significantly faster bone recovery in A-PRF-dressed sockets compared to control sockets (without A-PRF), including post mortem histology and immunofluorescence of healing tissues after 14 and 30 days.  
Animal studies were also carried out in 2012 by [PERSON] et al. in the group of 36 New Zealand White (NZW) rabbits, in which a bone defect 5 mm in diameter and 10 mm deep was made in the femur under general anesthesia. Subsequently, in 12 rabbits (group I), the defect was filled with bone substitute material (xenograft Bio-Oss Collagen(r)) and covered with a collagen membrane (Bio-Gide Perio(r)); in 12 rabbits from group 2, a layer of platelet rich plasma (PRP) was placed to the defect after application of the biomaterial. Group 3 (also 12 rabbits) was the control group that was treated without the regenerative techniques. After the animals were sacrificed, a histological examination of the dissection preparations was performed, which showed the most intense osteogenesis 1 month after treatment in group 2 (with PRP application). At subsequent stages of healing (after 3, 6 and 12 months), more intense osteogenesis was shown in group 1 (xenogenic material and resorbable collagen membrane). The worst results were obtained in the control group, while the use of two regenerative methods influenced the speed, quality and overall healing of intraosseous defects [34].