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.

Dear Editor, With regard to the published article “ arthroscopic curettage of intraosseous ganglions of lunate bone” in the last journal edition, it is time to review ulnar ABUTMENT syndrome with similar clinical and radiologic findings (1).

Background and Aims: Removable partial denture (RPDs) is a common therapy for rehabilitation of partialy edentulous patients while RPD causes a lot of periodontal problems. The purpose of this study was to investigate the effect of RPDs made in Babol dental school on the periodontal health of ABUTMENT and non-ABUTMENT teeth. Materials and Methods: In this cross sectional study, 70 patients who were candidates for RPDs divided into four groups according to Kennedy classification. The following periodontal parameters were evaluated for ABUTMENT and non-ABUTMENT teeth, plaque index (PI), calculus index (CI), width of keratinized gingiva, bleeding on probing (BOP), periodontal pocket depth (PPD), tooth mobility (TM) and gingival recession. This clinical measurement was taken immediately before insertion of the RPD, then one, three, and six months later. These parameters were then analyzed using Mann-Whitney, Independent sample ttest, Covariance, Chi-square statistical tests. Results: In Class I; the mean score for the width of keratnized gingiva (P<0. 001), PPD (P=0. 002), and BOP (P<0. 001) of the ABUTMENT and non-ABUTMENT teeth were significantly different after 1 month. After 3 months there were significant differences with regard to the PI (P=0. 01), width of keratnized gingiva (P<0. 001), BOP (P<0. 001) and PPD (P<0. 001). After 6 months, only the PI, CI, and TM parameters were not statistically significant. In Class II; the mean score for width of keratnized gingiva (P<0. 001) and PI (P=0. 002) after 1 month, width of keratnized gingiva (P<0. 001), BOP (P=0. 02), PPD (P=0. 05) and TM (P=0. 03) after 3 months and width of keratnized gingiva (P<0. 001), PI (P=0. 04), BOP (P<0. 001) and TM (P=0. 03) after six months were statistically significant. In Class III; only gingival recession did not show any significant difference at 1 and 3 months later. The width of keratnized gingiva (P<0. 001), PI (P=0. 001), BOP (P<0. 001) and TM (P=0. 03) after 6 months were statistically significant. Conclusion: This study showed that RPDs affect the periodontal condition of both ABUTMENT and non-ABUTMENT teeth, which can be reduced by more precise design of the prosthesis, periodontal follow ups and good oral hygiene.

Statement of Problem: A removable partial denture (RPD) is a common treatment modality for restoration of partially edentulous ridges. However this type of treatment may produce serious periodontal problems for remaining teeth.Purpose: The aim of this study was to determine the effects of RPDs with RPI design on the periodontal indices of ABUTMENT and non ABUTMENT teeth.Materials and Method: For this interventional and prospective study, 22 patients (30-68 years old; mean age of 48 years) were selected. All patients has Kennedy class I partial edentulous areas and were supposed to use removable partial dentures. Forty eight ABUTMENT and 48 non ABUTMENT teeth were assigned for this study. Clinical parameters including clinical probing depth (CPD), clinical attachment level (CAL), keratinized gingival width (KG), gingival index (GI) were measured in ABUTMENT and non-ABUTMENT teeth at baseline,1,4 and 12 months after delivery of RPDs. Data were analyzed using wilcoxon test.Results: All clinical indices with the exception of gingival index, at the time of baseline to 12 months, showed significant differences between ABUTMENT and non-ABUTMENT teeth (p<0.001).Significant differences were also noted for all indices between ABUTMENT and non-ABUTMENT teeth after 12 months. Conclusion: The results of this study indicated that removable partial denture with RPI design plays an important role in producing and intensifying the periodontal diseases in both ABUTMENT and non ABUTMENT teeth. It seems that this effect is due to the accumulation of more bacterial plaque. So, use of appropriate design and recommendation of good oral hygiene may decrease the severity of side effects.

Most previous laboratory studies of local scour at bridge ABUTMENTs were performed in rectangular channels in which the distributions of flow velocity and bed shear stress were considered uniform in the transverse direction. In reality however, bridge ABUTMENTs are usually located in the floodplain zone of rivers where velocity and shear stress distributions are directly affected by the lateral momentum transfer. The influence of channel geometry and lateral momentum transfer in compound flow field on scouring phenomenon, however, has not been fully investigated and understood as yet. This paper presents the results of an experimental study performed to investigate the impact of both sediment size and lateral momentum transfer on local scour at ABUTMENTs terminating in the floodplain of a compound channel. It is shown that, by accounting for lateral momentum transfer at small floodplain/main channel depth ratios (ya/H<0.3), estimates of maximum local scour depth are increased by up to 30%. In relation to the sediment size, earlier studies of scouring around circular bridge piers proposed a limit for the relative size of sediment (pier diameter/median size of bed material) beyond which the sediment size has no effect on the equilibrium sconr depth (Ettema, 1980; Chiew, 1984). The results of the current laboratory studies, however, indicated that the limit established for circular bridge piers might not be appropriate for the ABUTMENT case installed in the floodplain zones; further studies are required to draw a more general conclusion regarding the effects of relative grain size in the ABUTMENT case.

This Bridges are vital part of the transportation network Department of Civil Engineering. Their destruction caused by occurrence of a strong earthquake can cause irreparable damages to the regional economy. One of the effective factors on seismic response of a bridge is ABUTMENT and it's modelling. In most cases, analysis of seismic behavior and modelling of bridges is done using simplifying assumptions. This simplification may cause major changes in prediction of seismic behavior of bridges. Using simplified, roller and full models for ABUTMENT is very important in design and evaluation of seismic behavior of bridges. Backfill is a vital factor in modelling ABUTMENTs. In this study, ABUTMENTs were analyzed in three scenarios under records related to three stations of Imperial Valley earthquake (1979) and responses compare in two state with and without backfill. The results showed that minimum response (for deck, pier column and ABUTMENT) were related to the first modelling scenario (roller ABUTMENT) and maximum response were related to the fifth modelling scenario (simplified ABUTMENT as suggested by Shamsabadi for cohesive soil). Modelling of backfill was effective on displacement and rotation of pier column and displacement of deck and moment of ABUTMENT. For all records of earthquake, wall pier ABUTMENT (sixth scenario) was considerably consistent with modelling based on Caltrans guideline for sandy soil (second scenario). In the height ranging from 5 to 9 meters, the suggested modelling (wall pier ABUTMENT) can be used instead of Caltrans method. In this height range, the results (maximum ABUTMENT displacement and ABUTMENT pressure) vary from 11to 23%.

Background and Aim: ABUTMENT selection is an important decision to make in the dental implant treatments. The prohibitive cost and unavailability of original ABUTMENTs have driven many practitioners to opt for choosing compatible ABUTMENTs alternatively. However, the use of non-original and low-quality ABUTMENTs may lead to a myriad of complications for the patients. The current research was conducted with the aim of comparing original and non-original ABUTMENTs in dental implant treatments. Materials and Methods: A total of 46 review articles were selected and evaluated from articles published between 2001 and 2022. The search was performed in various electronic databases including PubMed, Science Direct, and Google Scholar. The search utilized keywords such as “ABUTMENT, ” “original ABUTMENT, ” “non-original ABUTMENT, ” “main ABUTMENT, ” “non-main ABUTMENT, ” and “compatible ABUTMENT. ” Data were meticulously collected on several parameters, including fit accuracy, microleakage, bacterial leakage, micromotion, rotational misalignment, screw loosening, fracture resistance, fatigue resistance, tensile strength, marginal accuracy, and other mechanical outcomes. Results: The results showed that, the original ABUTMENTs had more appropriate accuracy, more micro-movement, and fatigue resistance compared to non-original ABUTMENTs, and they were more durable. In addition, original ABUTMENTs provided a lower percentage of torque reduction and lower values for screw loosening than non-original examples. The mean micro-gap at the implant-ABUTMENT interface, bacterial leakage, and rotational misalignment were higher in non-original ABUTMENTs. The findings showed that the incidence of mechanical failure was lower for original ABUTMENTs and its marginal accuracy was higher. Conclusion: Although non-original ABUTMENTs may visually resemble original ones, significant differences exist in their physical and mechanical properties. These discrepancies can be identified through advanced testing methods.

Background. The most common problem associated with dental implants is the ABUTMENT screw loosening. This research aimed to investigate the effect of the type of connection on screw loosening, using a finite element method (FEM). Methods. Periosave system and different types of the implant– ABUTMENT connection were used for modeling. After being measured, CAD files were modeled using CATIA software and imported to the ANSYS analysis software, and the model was loaded. Results. A force of 100 N was applied at 0. 1 second, and no force was applied at 0. 42 second. The screw head deformation at 0. 1 and 0. 42 seconds was 8 and 3. 8 μ m, and 7. 6 and 2. 8 μ m at morse taper and octagon dental implant connections, respec-tively. The displacement rate of the internal surface of the ABUTMENT at 0. 1 and 0. 42 seconds was 10. 7 and 8. 4 μ m, and 5. 7 and 5. 6 μ m in the octagon and morse taper dental implant connections, respectively. The displacement of the implant suprastruc-ture– ABUTMENT interface from the screw head at 0. 1 and 0. 42 seconds was 9 and 7 μ m, and 7 and 6 μ m in the morse taper and octagon dental implant connections, respectively. At intervals of 0 to 0. 1 seconds and 0. 6 to 0. 8 seconds, the octagon connec-tion was separated at the maximum screw head displacement and the internal part of the ABUTMENT, but the morse taper con-nection did not exhibit any separation. In the above time intervals, the results were similar to the maximum state in case of the minimum displacement of the screw head and the internal part of the ABUTMENT. Conclusion. Screw loosening is less likely to occur in the morse hex connection compared to the octagon connection due to the lack of separation of the screw from the internal surface of the ABUTMENT.