BackgroundPlatelet‐rich fibrin (PRF) can be used in the alveolar socket preservation (ARP). However, the hard tissue‐regeneration property of PRF in alveolar socket preservation is still unclear.PurposeTo compare the new bone formation ratio between using PRF as a socket preservation material and normal wound healing, by means of histomorphometric analysis.Materials and MethodsThirty‐three healthy volunteers were recruited and randomized into PRF and control group. Minimally traumatic extractions were performed. Eighteen patients were treated with ARP using PRF, while the rest were left to heal naturally. Bone specimens were harvested using trephine bur 2 months after the extraction process. Histomorphometric analysis of new bone formation area compared with total socket area was performed using the software Fiji Is Just Image J (version 2, GNU General Public License).ResultsThirty‐three volunteers were participated. Twenty‐eight bone specimens were collected. The new bone formation ratio was higher in PRF group than in control group (31.33 ± 18% and 26.33 ± 19.63%, respectively). However, there was no statistically significant difference in the ratio between the PRF and control groups (P = .431).ConclusionsIt may be concluded that the use of PRF in ARP does not statistically significant enhance new bone formation after tooth extraction compared to normal wound healing (P > .05).

SUMMARY Introduction.Although many previous studies have reported on the high success rate of short dental implants, prosthetic design still plays an important role in the long-term implant treatment results. This study aims to evaluate stress distribution characteristics involved with various prosthetic designs on standard implants or short implants in the posterior maxilla. Materials and methods. Six finite element models were simulated representing the missing first and second maxillary molars. A standard implant (PW+ implant: 5.0x10 mm) and a short implant (PW+ implant: 5.0x6.0 mm) were applied under the various prosthetic conditions. The peri-implant maximum bone stress (V on mises stress) was evaluated when 200 N 30° oblique load was applied. A type III bone was approximated and complete osseous integration was assumed. Results. Maximum Von mises stress was numerically located at the cortical bone around the implant neck in all models.In every standard implant model shows better stress distribution. Stress values and concentration area decreased in the cortical and cancellous bone when implants were splinted in both the standard and short implant models. With regard to the non-replacing second molar models found that the area of stress at the cortical bone around the first molar implant to be more intensive. Moreover, in the non-replacing second molar models, the stress also spread to the second pre-molar in both the standard and short implant models. Conclusions. The length of the implant and prosthetics designs both affect the stress value and distribution of stress to the cortical and cancellous bones around the implant.

Avulsion, following traumatic injuries, is relatively infrequent. The treatment of avulsed teeth is by replantation of the avulsed tooth into its own socket. However, sometimes the avulsed tooth cannot be found at the accident site. We report a case in which the avulsed maxillary central incisor is replaced by an embedded lower premolar. A 2-year follow-up shows complete periodontal healing and a very satisfactory clinical result.