Aim of the study: To establish the influence of various factors upon the loosening of abutment screw. \ud Material and Methods: The current study has analyzed the factors leading to loosening of the abutment screws implant-supported restorations. 116 patients have been examined with 234 setting implants for a period of 2 to 9 years. Factors related to the planning of implant prostheses such as area of implantation, available bone volume have been registered, as well as those related to the functional loading of dental implants. The impact of their effect has been calculated. \ud Results: Abutment screw loosening has been registered in 6.8% of the monitored cases. Regarding the type of connection between the implant and abutment a higher prevalence has been reported in connection with an internal octagon - 4.7% compared to the conical connection - 2.1%. It was found that the type of prosthesis, bruxism, cantilevers, non-balanced occlusion, crestal bone resorption and time of this complication setting in are factors of statistically significant influence.\ud Conclusion: It has been concluded that the optimal choice and number of implant positions, the design of prosthesis, achieving optimal occlusion as well as reporting cases of bruxism, leading to functional overload of dental implants are of particular importance in order to avoid bio-mechanical long-term complications

Background: To explore the relationship between the operative methods for sinus lifting and related intra-and postoperative complications. Methods: 47 cases of sinus lift were traced, with 118 implants placed. 83 of them after lateral sinus lifting and 35 with a crestal approach. Presence of bone septum, thickness of the sinus membrane, bone density, and the height of residual bone were tracked out preoperatively, as prerequisites of complications during and after implant placement in the distal parts of the maxilla. Results: In eight cases (17.02%), sinus membrane perforations occurred. The most common location of the tearing was close to the lower medial edge of the bone window. After fixing perforation, a total of 37 implants were placed under these conditions. In three of them (5.41%), poor osseointegration was found after six mounts. Statistically significant impact of the thickness of the sinus membrane in cases of membrane tearing was found. Conclusions: Increasing the height of the available bone in the distal areas of the maxilla by elevating the maxillary sinus floor is a safe and predictable procedure. Both the crestal and lateral approaches have a high success rate. All possible complications during the operation need to be analyzed in advance, and when they occur, it is mandatory to fix them adequately. Therefore, a careful consideration of the local and systemic conditions affecting implant survival is essential for successful implant treatment.

A clinical case of a horizontally displaced dental implant, which moved below the level of the mandibular canal during surgery is presented together with a brief review of the comparable published cases. The bone mineral density and the morphology of the alveolar ridge were analyzed at the site of osteotomy, and the low bone density of Hounsfield Units was found in the area. The factors related to implant displacement were: the anatomical features of bone structure, and the applied mechanical pressure during the implant insertion. The displacement of the dental implant below the level of the mandibular canal during implantation can be a severe complication. Its removal requires the safest surgical approach to avoid damaging the inferior alveolar nerve. The description of one clinical case does not provide grounds for drawing definite conclusions. To avoid similar incidents, detailed radiographic assessment before implantation is necessary; it is also important to follow the surgical protocols of implant placement into soft bone and to create conditions for a good visibility and sufficient control of bleeding during surgery.

The study comprised 20 lateral sinus floor elevation cases performed in 18 patients. During surgery, in four cases, a perforation of the Schneiderian membrane was detected. An attempt to suture the perforated membrane may increase the risk of enlarging the perforation. Therefore, we suggest a more conservative protocol be applied in all four cases where perforation occurred. The procedure consists of the 3-layer technique: an absorbable oxidized cellulose gauze moisturized with Dicynone was placed in this area. Under it, as a second layer, a PRF membrane is applied and then covered with a slow-resorbable collagen membrane. At that point, the surgery continues with the placement of the bone substitute material, and the sinus-lifting is finalized according to the selected protocol. The clinical studies demonstrate that the bone graft has a slower healing rate in areas with perforation, which is a proof of the osteogenic properties of the Schneiderian membrane. The cases described reveal that using this surgical protocol is risk-free and has a high success rate.