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BACKGROUND: In the treatment with dental implant prosthesis, the stress distribution of marginal bone and implant-bone interface Is affected by the factors of restoration and occlusion. The Internal structure and the stress distribution of Implant-bone Interface determine the long-term life of the implant and the stability of the marginal bone. OBJECTIVE: To analyze the effects of zirconia-based all-ceramic crown and Co-Cr alloy porcelain ceramic crown on the stress distribution of implant-bone interface, implant, prosthesis abutment, retention screw, and the inner structure in three occlusal relationships. METHODS: Using Mimics 17.0 software, the implant model of maxillary central incisor was established based on the cone beam CT of a patient undergoing prosthesis implantation Into the maxillary central incisor. Two kinds of three-dimensional finite element models of zirconia-based all-ceramic crown and Co-Cr alloy porcelain ceramic crown were constructed. The edge to edge occlusion, normal occlusion and deep overbite were simulated to analyze the stress distribution of Implant structure and the Implant-bone Interface in the three occlusal relationships. RESULTS AND CONCLUSION: (1) In the Co-Cr alloy porcelain ceramic crown group, when the occlusal relationship changed from the edge-to-edge occlusion to the normal occlusion and deep overbite relationships, the stress at the occlusal point of the prosthesis increased correspondingly, and the stress at the abutment, Implant and the Implant-bone Interface decreased. In the normal occlusal relationship, the stress at the retention screw was more concentrated than that in the other two occlusal relationships, and its peak value of the equivalent stress was higher. (2) In the zirconia-based all-ceramic crown group, when the occlusal relationship changed from edge-to-edge occlusion to the normal and deep overbite relationships, the stress peaks of the abutment, implant and implant-bone interface decreased gradually. In the normal occlusal relationship, the stress peaks of the occlusal point and the retention screw were higher than those in the other two occlusal relationships. (3) In the edge-to-edge occlusion relationship, the peak of equivalent stress at the occlusal point of the implant prosthesis in the Co-Cr alloy porcelain ceramic crown group was slightly higher than that in the zirconia-based all-ceramic crown group. The peaks of equivalent stress of the abutment, retention screw, Implant, and Implant-bone Interface in the Co-Cr alloy porcelain ceramic crown group were slightly lower than those in the zirconia-based all-ceramic crown group. In the normal occlusal relationship, the peak of equivalent stress at the neck of the implant in the Co-Cr alloy porcelain ceramic crown group was slightly higher than that in the zirconia-based all-ceramic crown group. In the deep overbite relationship, the peaks of the equivalent stress at the occlusal site of the implant prosthesis and the neck of the implant in the Co-Cr alloy porcelain ceramic crown group were higher than those in the zirconia-based all-ceramic crown group. The peaks of equivalent stress of the abutment, retention screw, and implant-bone interface In the Co-Cr alloy porcelain ceramic crown group were slightly lower than those in the zirconia-based all-ceramic crown group. (4) These results showed that different occlusal relationships and different upper structures of the implant prosthesis affected the stress distribution in each part of the implant and at the implant-bone interface. This finding may provide a reference for the prediction of long-term complications of implant prosthesis.
ABSTRACT
Objective: To explore the establishment of the incisor extraction wound models in aesthetic area of the rats and the application effect of modified minimally invasive tooth extraction surgery, and to provide the basis for establishment of the incisor extraction wound models in aesthetic area and improvement of the healing of alveolar bone and soft tissue. Methods: Twenty-four SD rats were randomly divided into control group and experiment group («=12). The crowns of right lower incisors of the rats were removed along with the top of gingival tissue on the 9th, 6th and 3rd days before the incisors extraction, and then the incisor were extracted on the 10th day of experimental modeling. In experiment group, the incisors of rats were extracted by the modified minimally invasive incisor extraction, while in control group the conventional extraction was used to extract the incisor of the rats. The survival rates and body weights of the rats in two groups were observed before and after the incisor extraction. The complete degrees of incisor extraction of the rats in two groups were detected, and the rates of complete incisor extraction were calculated; the healing condition of soft tissue around the incisor extraction of the rats in two groups 1 week after incisor extraction and the recovery condition of mandibular alveolar bone of the rats 4 weeks after incisor extraction were compared. Results: The survival rate of the rats in experiment group was higher than that in control group ( P<0. 05). The body weights of the rats in experiment group at different time points after extraction were higher than those in control group ( P<0. 05). Compared with control group, the rate of complete incisor extration of the rats in experiment group was increased ( P<0. 01). The soft tissue around the incisor extraction wound of the rats in experiment group was completely healed within one week after incisor extraction, and new bone was found at the top of alveolar ridge four weeks after incisor extraction; meanwhile, the soft tissue around the incisor extraction wound of the rats in control group was still red and swollen one week after incisor extraction, and the trabecular structure of bone at the top of alveolar ridge was disordered found weeks after incisor extracion. and the new bone structure was poor. Conclusion: The modified minimally invasive tooth extraction surgery can significantly improve the complete extraction effect of incisors in the rats, and the soft tissue around the incisor extraction wound and the alveolar bone are healed well after minimally invasive tooth extractioa.
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Objective @# To investigate the application of digital immediate implant and angle screw channel abutment in the aesthetic area and the related influencing factors by reviewing the data of one case of immediate implant repair of the upper anterior teeth and related literature. @*Methods@#One case of refractory chronic apicitis of the upper anterior teeth involved immediate implantation after extraction. The digital information of the patient was obtained by CBCT and intraoral scanning. According to the information from the patients, a preoperative evaluation was performed; a treatment scheme was formulated; a minimally invasive extraction was performed; implants were placed under a digital guide plate; and temporary restoration was immediately performed. Six months after the operation, the patients underwent individualized mold removal, and angle screw channel fixation was completed. We observed the cosmetic effects and soft and hard tissue and gingival contour maintenance effects after restoration and reexamined the patients 6 months after restoration. In addition, the relevant literature was reviewed. @*Results @#The height of the gingival margin and gingival papilla and gingival contour of this patient were well maintained. The red and white aesthetic effect was good. There was no redness or swelling of the gingiva nor obvious changes in the soft and hard tissues around the implant 6 months after restoration, and the patient was satisfied. The results in the literature review show that a preoperative design based on CBCT and intraoral scanning data combined with digital software and a whole digital guide plate make the procedure more accurate and safer. These factors can not only avoid important anatomical structures and serious surgical complications but can also result in implantation in the best three-dimensional position. In addition, the application of digital impression technology and CAD/CAM increases the efficiency, speed, accuracy, simplicity, and comfort of oral impressions and the construction of temporary and final prostheses more precise and faster, greatly improving clinical efficiency. @*Conclusion@#Digital immediate implant and angle screw channel abutment is a good method to restore the aesthetics and function of missing teeth and to avoid the complications caused by adhesive residue.
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OBJECTIVE@#This study aimed to evaluate the clinical effect of the socket-shield technique in the maxillary anterior region at one year after implant placement.@*METHODS@#Ten patients with maxillary anterior teeth that cannot be reserved were enrolled. Implants were installed following the socket-shield technique and restored six months after the surgery. The thickness of the labial maxillary bone of the implant was compared before and one year after the surgery. At one year follow-up, the reten-tion rate of the implants, Jemt classification, and pink and white aesthetic scores were evaluated. Postoperative complications and patient satisfaction were also analyzed.@*RESULTS@#One year after installation, the retention rate of the implant was 100%. The thickness of the maxillary bone at the neck, central, and root section of the implant reduced to (0.27±0.21), (0.19±0.20), and (0.28±0.29) mm, respectively, compared with the values immediately after the operation. The thickness of the labial maxillary bone at the three measurement points immediately after and one year after the operation was statistically significant (P0.05) of the difference thickness between immediate and one year after operation at the three measurement points. The pink esthetic scores of the implant prosthesis was 9.10±0.54, and the white esthetic scores was 9.00±0.63. No complications were observed, and the patients had a high degree of satisfaction.@*CONCLUSIONS@#The socket-shield technique could provide acceptable treatment results but cannot completely avoid the reconstruction of the labial maxillary bone of the implants. The technique exhibits favo-rable short-term aesthetic result, but its long-term clinical effect and aesthetic problems need to be further studied.