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Background. The widespread use of dental implants as a predictable treatment choice has drawn attention to their complications as a major challenge despite their high clinical success rates. In this context, loosening of the abutment screw in posterior single crowns is the most common problem; the use of adequate preload and proper anti-rotational features at implant?abutment interface appear to be two main solutions to such a problem. The present study evaluated the effect of implant?abutment connections in four different implant systems before and after cyclic loading. Methods. Intra-Lock, Dentis, Xive, and Dio implant systems were used in this study. Each system underwent one million cycles of dynamic forces eight times with a magnitude of 110 N. For each specimen after tightening the screw with a torque of 32 Ncm, the detorque values were measured and recorded by a digital torquemeter after and before cyclic loading. Data were analyzed by Kolmogorov-Smirnov, Levene's, one-way ANOVA, and post hoc Tukey tests. Results. Initial detorque values between the study groups showed significant differences (P < 0.0001). Pairwise comparisons showed significantly lower primary detorque values in the Dentis system compared to the three other systems (P < 0.0001). After cyclic loading, significant differences were observed between the study groups (P < 0.0001). Pairwise comparisons of the groups showed significant differences between all the systems after loading. Conclusion. The type of implant?abutment connection is an essential factor influencing the amount of abutment screw loosening. [ABSTRACT FROM AUTHOR]

Background: One of the most important fundamental issues in mental health is patients' satisfaction with the beauty of their teeth and their compatibility with complete dentures. Therefore, this study investigated the role of early maladaptive schemas and body image in the level of satisfaction with complete dentures among patients referred to the dental clinic of Islamic Azad University of Tabriz, Iran, in 2021-2022. Methods: The research was a descriptive correlational study. This study's statistical population included all candidates for complete dentures referring to the dental clinic of Islamic Azad University of Tabriz in 2021-22, from among which, 168 people were selected through convenience sampling method. The research tools included the Young Schema Questionnaire-Short Form (YSQ-SF) (1988), Body Image Concern Inventory (BICI) Littleton et al. (2005), and Dental Satisfaction Questionnaire (DSQ) by Davies and Ware (1982). The collected data were analyzed using multiple regression tests in SPSS software. Results: The results showed a relationship between the components of early maladaptive schemas [failure (B = -0.225), defectiveness/shame (B = -0.279), social isolation/alienation (B = 0.278), abandonment/instability (B = 0.331), subjugation (B = -0.264), and dependence/incompetence (B = 0.246)] and the level of satisfaction with complete dentures among the patients (P < 0.05). The results also showed a significant relationship between the components of body image and the level of satisfaction with complete dentures (P < 0.05). Conclusion: It can be concluded that early maladaptive schemas and body image playa role in the satisfaction level of patients referred to the dental clinic of Islamic Azad University of Tabriz. [ABSTRACT FROM AUTHOR]

Statement of the Problem: Various default values in each software can eventually lead to different crown thicknesses and affect their compressive strength. Purpose: This study aimed to compare the compressive strength of temporary crowns made with the milling machine, designed in Exocad and 3Shape Dental System software. Materials and Method: In this in vitro study, 90 temporary crowns were made and evaluated based on each software settings. For this purpose, a sound premolar was first scanned as a pre-operative model by 3Shape laboratory scanner. The standard tooth preparation and scanning were performed, and then the temporary crown files (designed by each software) were transferred to the Imes-icore 350i milling machine. A total of 90 temporary crowns (45 based on the file of each software) were made using poly methyl methacrylate (PMMA) vita cad-temp block. The value of compressive force displayed on the monitor was recorded at the first crack and the ultimate failure of the crown. Results: The first crack and the ultimate strength of crowns designed with the Exocad software was 903.5±96N and 1490±139.3N and for crowns designed with 3Shape Dental System software was 1060.4±160.2N and 1691.1±73.9N, respectively. The amount of compressive strength of temporary crowns made with 3Shape Dental System was significantly higher than those made with Exocad software and this difference was statistically significant(p= 0.000). Conclusion: The compressive strength of temporary dental crowns made by both softwares is in a clinically acceptable range, but considering that the average compressive strength in the 3Shape Dental System group was slightly higher than of the other group, it is preferable to design and fabricate with 3Shape Dental System software to increase the compressive strength of these crowns. [ABSTRACT FROM AUTHOR]

Background. Tightening and loosening of the prosthetic components of the implant are carried out with various screw designs. This study compared the rate of deformation of the abutment screw in two hexagonal and star screw head designs after consecutive tightening and loosening. Methods. In this study, two fixtures were mounted vertically in die stone blocks using a surveyor. Then the corresponding abutment (with a diameter of 4.5 mm and a gingival height of 2 mm; Dio-SM and Dio-UF system) was mounted on each fixture. In each fixture, six abutment screws from each manufacturer were used (12 abutment screws in total). The abutment screw head of the Dio-UF system is hexagonal, and the abutment screw head of the Dio-SM system is star-shaped. The samples were examined under a stereomicroscope (Nikon C-DS) at a magnification of × 50. The image of each abutment screw head (6 abutment screws in each group) was prepared before the procedural steps and after 5, 10, and 15 times of tightening and loosening with 25-Ncm torque using a stereomicroscope. Then the differences in the surface areas of consecutive specimens (0, 5, 10, and 15 consecutive tightening and loosening rounds) between hexagonal and star-shaped abutment screws were calculated. The study results were reported via descriptive statistical methods (mean ± standard deviation). Statistical analysis was performed using SPSS 24, and the significance level was defined at P < 0.05. Results. Increasing the number of tightening and loosening rounds increased the screw head surface area in both hexagonal and star shapes. At all stages, the changes in the star-shaped screw head were greater than in the hexagonal screw. These changes were statistically significant at all stages (P < 0.05). In addition, there was a statistically significant difference between the area values and the number of tightening and loosening rounds separately in both screw types (P < 0.001). Also, the surface areas of the head of both screws in all tightening and loosening rounds were significantly different (P < 0.001). Conclusion. Increasing the number of tightening and loosening rounds increased the screw head surface area in both hexagonal and star-shaped geometrical forms. Also, the extent of area changes at all stages in star-shaped screw heads was greater than in hexagonal screws. [ABSTRACT FROM AUTHOR]