Search Results (162)

Background/Objectives: Dental practitioners widely use dental implants to treat traumatic cases. Titanium implants are currently the most popular choice among dental practitioners and surgeons. The discovery of newer polymeric materials is also influencing the interest of dental professionals in alternative options. A comparative study between existing titanium implants and newer polymeric materials can enhance professionals’ ability to select the most suitable implant for a patient’s treatment. This study aimed to investigate material property advantages of high-performance thermoplastic biopolymers such as PEEK and PEKK, as compared to the time-tested titanium implants, and to find the most suitable and economically fit implant material. Methods: Three distinct implant material properties were assigned—PEEK, PEKK, and commercially pure titanium (CP Ti-55)—to dental implants measuring 5.5 mm by 9 mm, along with two distinct titanium (TI6AL4V) abutments. Twelve three-dimensional (3D) models of bone blocks, representing the mandibular right molar area with Osseo-integrated implants were created. The implant, abutment, and screw were assumed to be linear; elastic, isotropic, and orthotropic properties were attributed to the cancellous and cortical bone. Twelve model sets underwent a three-dimensional finite element analysis to evaluate von Mises stress and total deformation under 250 N vertical and oblique (30 degree) loads on the top surface of each abutment. Results: The study revealed that the time-tested titanium implant outperforms PEEK and PEKK in terms of marginal bone preservation, while PEEK outperforms PEKK. Conclusions: This study will assist dental practitioners in selecting implants from a variety of available materials and will aid researchers in their future research. Full article

The attachment of the oral epithelium to the abutment surface is crucial for the long-term success of dental implants. This study aimed to evaluate the attachment of human epithelial cells to anodized titanium surfaces. Anodized titanium discs were used as the experimental group, while machined titanium discs served as the control. Surface roughness and wettability were first measured for each group. Next, human epithelial cells were seeded onto each disc at a density of 4.0 × 10⁴ cells/cm² and evaluated 3, 6, and 24 h later for cell proliferation, as well as mRNA expression and protein levels of laminin and integrin β₄. Surface roughness was comparable between the two groups; however, wettability was significantly higher in the experimental group. Cell proliferation increased over time in both groups and showed no significant difference. Notably, the expression levels of both laminin and integrin β₄ were significantly higher in the experimental group at 24 h. Furthermore, protein localization of laminin and integrin β₄ was observed along the cell margins on the anodized surface. These findings suggest that anodization enhances epithelial cell attachment by promoting the expression and peripheral organization of key adhesion molecules. Full article

Background and Objectives: Conventional methods for removing cemented fixed prosthetic restorations (FPRs) are unreliable and lead to unsatisfactory outcomes. At their best, they allow the tooth to be saved at the expense of a laborious process that also wears down rotating tools and handpieces and occasionally results in abutment fractures. Restorations are nearly never reusable in any of these situations. Erbium-doped yttrium-aluminum-garnet (Er:YAG) and erbium-chromium yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers casafely and effectively remove FPRs, according to scientific studiesre. This study sets out to examine the impact of Er:YAG laser radiation on the debonding of different ceramic restorations, comparing the behavior of various ceramic prosthetic restoration types under laser radiation action and evaluating the integrity of prosthetic restorations and dental surfaces exposed to laser radiation. Materials and Methods: The study included a total of 16 removed teeth, each prepared on opposite surfaces as abutments.y. Based on the previously defined groups, four types of ceramic restorations were included in the study: feldspathic (F), lithium disilicates (LD), layered zirconia (LZ), and monolithic zirconia (MZ). The thickness of the prosthetic restorations was measured at three points, and two different materials were used for cementation. The Er:YAG Fotona StarWalker MaQX laser was used to debond the ceramic FPR at a distance of 10 mm using an R14 sapphire tip with 275 mJ, 20 Hz, 5.5 W, with air cooling (setting 1 of 9) and water. After debonding, the debonded surface was visualized under electron microscopy. Results: A total of 23 ceramic FPRs were debonded, of which 12 were intact and the others fractured into two or three pieces. The electron microscopy images showed that debonding took place without causing any harm to the tooth structure. The various restoration types had the following success rates: 100% for the LZ and F groups, 87% for the LD group, and 0% for the MZ group. In terms of cement type, debonding ceramic FPRs cemented with RELYX was successful 75% of the time, compared to Variolink DC’s 69% success rate. Conclusions: In summary, the majority of ceramic prosthetic restorations can be successfully and conservatively debonded with Er:YAG radiation. Full article

The purpose of this study was to clarify the physical durability of a diamond-like carbon (DLC) thin film coated on pure titanium. The titanium surface of the abutment does not have sufficient toughness to prevent an increase in surface roughness or damage when the implant is scaled using a professional mechanical implement. The scaling process used for the removal of the dental plaque adhered to the abutment surface could increase the potential for the deposition of oral microorganisms and the accumulation of plaque, which increase the risk of peri-implantitis. A DLC thin film is biocompatible material that is known for its toughness, including extreme hardness, high abrasion resistance, chemical inertness, and high corrosion resistance. Protecting the abutment surface with the application of a DLC might prevent plaque adhesion due to its non-stick property. There was little change in the surface roughness of titanium samples to which DLC surface protection had been applied when the surface of the sample was scratched with a stainless steel scalar more than a thousand times. When cleaning the surface of pure titanium samples, the surface roughness significantly increased. DLC thin films are effective for the prevention the surface roughness of pure titanium implants from being increased when the conventional cleaning of the surface of the implant is performed. Full article

Background/Objectives: Dental implants represent a viable solution for replacing missing teeth; however, multiple disconnections and reconnections of intermediate abutments contribute to the apical displacement of the peri-implant connective tissue barrier, resulting in additional marginal bone loss. To the best of our knowledge, no definitive customized abutments currently exist that are specifically designed according to the morphology of the tooth to be replaced and its position within the dental arch, allowing for digital planning within the prosthetic implant design and insertion during the surgical procedure without subsequent disconnection. Methods: The First Biological Respect (FR) technique, described in this case report, enables the digital planning not only of the implant but also of the patented FR customized-shaped, definitive abutment and associated FR prosthetic components. The FR technique was applied to a case involving an immediate post-extraction implant in position 12. Results: With the limitations of a case report, the application of the FR protocol demonstrated stable crestal bone levels at the 1-year follow-up. Additionally, soft tissue volume was maintained at 6 months, reflecting the accuracy of the customized prosthetic components in supporting, guiding, and protecting peri-implant soft tissues. At the 1-year follow-up, an increase in soft tissue volume was observed, likely attributable to tissue maturation and the further customization of the definitive prosthetic elements. Conclusions: The FR technique represents a viable therapeutic alternative that, through its patented, fully customized components, allows for the digital planning of the implant, as well as the customized definitive abutment, coping, provisional, and final prosthetic framework. This facilitates a single-stage surgical and prosthetic approach. By eliminating the need for repeated abutment disconnections, this method supports the long-term stability of both hard and soft peri-implant tissues while also reducing overall treatment time for both clinician and patient. Further studies involving larger patient cohorts are necessary to validate this protocol. Full article

Clouds play a central role in regulating incoming solar radiation and outgoing terrestrial emission; hence, they must be internally constrained to prognose Earth’s temperature. At the same time, planetary fluids are inherently turbulent, so the climate state would tend toward maximum entropy production—a generalized second law of thermodynamics. Incorporating these requirements, I have previously formulated an aquaplanet model to demonstrate that intrinsic water properties may strongly lower the climate sensitivity to solar irradiance, thereby resolving the faint young Sun paradox (FYSP). In this paper, I extend the model to include other external forcings and show that sensitivity to the reduced outgoing longwave radiation by the elevated pCO₂ can be several times greater, but the global temperature remains capped at ~40 °C by the exponential increase in saturated vapor pressure. I further show that planetary albedo augmented by a tropical supercontinent may cool the climate sufficiently to cause tropical glaciation. And since the glacial edge is marked by above-freezing temperature, it abuts an open, co-zonal ocean, thereby obviating the “Snowball Earth” hypothesis. Our theory thus provides a unified framework for interpreting Earth’s diverse climates, including the FYSP, the warm extremes of the Cambrian and Cretaceous, and the tropical glaciations of the Precambrian. Full article

Background/Objectives: This in vitro study investigated the retention of three different geometrical designs of short titanium base (Ti-base) abutments used in implant-supported zirconia crowns. The advent of digital technology has facilitated the integration of Ti-base abutments into implant dentistry by improving time efficiency, precision, and patient comfort. Methods: Three types of short Ti-base abutments were evaluated: Geo SRN multibase^® (Group A), Herilink^® (Group B), and TS Link^® (Group C), each with a height of 4 mm and gingival height of 1 mm (n = 20 per group). Zirconia crowns (LUXEN^® Smile S2, DentalMax, Republic of Korea) were modified for the testing setup and fabricated using CAD/CAM technology, then bonded to the abutments with RelyX^® Luting 2 resin-modified glass ionomer cement. Pull-out tests were conducted at a crosshead speed of 1 mm/min to assess retention. Results: One-way ANOVA and post hoc Tukey tests revealed significant differences in retention values among the different abutment shapes (p < 0.05). The mean retention forces were 194.65 N for Group A, 241.33 N for Group C, and 360.20 N for Group B. Conclusions: The geometrical design of Ti-base short abutments significantly affects the retention of CAD/CAM zirconia crowns, with hexagonal shapes (Group B) demonstrating superior retention. Clinically, selecting an abutment design with enhanced mechanical retention may improve the long-term success of implant-supported restorations. Full article

The aim of this study was to compare the dimensional accuracy of vinyl polysiloxane impressions differing in terms of curing time (regular-setting (RS) or fast-setting (FS)) in combination with different tray materials (metal (M) and plastic (P)). A typodont reference model simulated a partially edentulous maxilla. Reference points were given by center points of either precision balls welded to specific teeth or finishing-line centers of prepared teeth. These reference points enabled the detection of dimensional deviations between the digitized reference and the scans of the models achieved from the study impressions. Twenty impressions were made for each of the following four test groups: RS-M, RS-P, FS-M and FS-P. Global scan data accuracy was measured by distance and tooth axis deviations from the reference, while local accuracy was determined based on the trueness and precision of the abutment tooth surfaces. Statistical analysis was conducted using ANOVA accompanied by pairwise Tukey post hoc tests (α = 0.05). Most of the distances tended to be underestimated. Global accuracy was favorable; even for long distances, the mean absolute distance deviations were < 100 µm. Local accuracy was excellent for all test groups, with trueness ≤ 11 µm and precision ≤ 9 µm. Within the limitations of this study, all impression and tray materials were suitable to fabricate models with clinically acceptable accuracy. Full article

This study compares various machine learning models to determine the method with the highest accuracy rate to predict the equilibrium scour depth of bridge abutments. Unlike in previous studies, hyperparameter optimization is focused on increasing model performance in small datasets, and feature importance ranking is analyzed. This study employs Multiple Linear Regression (MLR), Support Vector Regression (SVR), Decision Tree Regressor (DTR), Random Forest Regressor (RFR), XGBoost, and Artificial Neural Networks (ANNs) to predict the Dse. The dataset consists of 150 records with the following key hydraulic parameters: the flow depth (Y), abutment length (L), channel width (B), flow velocity (V), and median grain size ($d_{50}$). The results show that DTR achieved the highest accuracy (R² = 0.992, accuracy = 99.28%), followed by XGBoost (R² = 0.990, accuracy = 99.21%) and ANNs (R² = 0.981, accuracy = 98.77%). Traditional MLR exhibited lower accuracy (R² = 0.806, accuracy = 81.14%), confirming the superiority of AI-based models. These findings highlight the effectiveness of machine learning in scour prediction, providing a reliable alternative to conventional methods. This study underscores the potential of AI in hydraulic engineering, facilitating efficient bridge design and maintenance strategies. Future research should explore real-time data integration and hybrid AI models for improved interpretability and robustness. Full article

Background: Primary molars with deep carious lesions often require a treatment with pulpotomy and restoration with a crown. Aim: This study aims to compare the survival rates of stainless steel (SSC) and zirconium oxide (ZOC) crowns carried out on pulpotomized primary molars using the International Caries Detection and Assessment System (ICDAS) 4 to 6 lesions. Materials and Methods: The data of 100 patients (mean age 5.3 ± 2.1 years, mean decayed, missing or filled primary teeth (dmft) 7.1 ± 3.2) with 272 primary molars (40, 225, 7 with ICDAS 4, 5, 6, respectively) were collected retrospectively from a specialized private pediatric dental office after ethical approval was obtained and each participant agreed to participation in the study. Primary molars were treated between 2019 and 2021 with pulpotomy (15.5% ferrous sulfate solution for hemostasis and zinc oxide eugenol as a wound dressing) followed by a crown (203 SSC and 69 ZOC) with a minimum follow-up period of 6 months and a mean follow-up time of 28.2 (±11.0) months. Results: Failure occurred significantly less often in SSC (n = 13 out of 203) than in ZOC (n = 20 out of 69; p < 0.001). Major failure was attributed to swelling and abscess (n = 13, 39.4%) followed by the occurrence of fistula (n = 15, 45.4%) and fracture of the crown and abutment (n = 5, 15.2%). Minor failure due to cement dissolution occurred significantly less often in SSC than in ZOC (n = 10 out of 203 vs. n = 9 out of 69; p < 0.005. A Kaplan–Meier survival analysis showed an overall estimated survival time of 38.25 (Confidence interval (CI): 37.0–39.4) months for both types of crowns. A Log-Rank (Mantel–Cox) analysis showed a statistically significant difference (p < 0.05) in the estimated mean survival time of SSC (39.75; CI: 38.5–40.9 months) and ZOC (33.4; CI: 30.5–36.3 months). Survival probability drops just below 80% for ZOC and stays a little over 90% for SCC around the 20th month. Conclusions: SSC showed an advantage over its ZOC counterpart when placed after pulpotomy for the management of primary molars with deep carious lesions. A higher necessity for re-intervention in the more aesthetic ZOC should be considered in clinical decision taking. Full article

In spring, the river ice melts to a certain extent and cracks to form drift ice and impact force on the bridge abutments; the river ice, due to the impact of ablation, has an internal formation of different porosities, and the level of porosity affects the mechanical properties of the river ice, so that the impact force generated by the river ice is also different. In this paper, the Heihe–Blagoveshchensk Amur River Bridge abutment is the object of river ice impact, and the discrete element method (DEM) is employed to analyze the impact process and impact force on the abutment by numerical simulation of the melting river ice. The damage characteristics of the ice rows with different ice speeds, ice thicknesses, and porosity, and the time curve of the impact force are obtained. It is found that the maximum impact force of river ice on the abutment decreases nonlinearly with the increase in river ice porosity; the peak contact force occurs with a lag time, and the damage is gradually concentrated in the vicinity of the area in direct contact with the abutment. In this paper, according to the simulation results, the relationship between river ice porosity and the maximum impact force on the bridge abutment, as well as the time parameters, is obtained by fitting, and the power loading model of the bridge abutment impacted by the river ice is established, which provides a basis for the reasonable calculation of the impact force of the ablated river ice at bridge abutments. Full article

The main task of the operation of engineering structures is to ensure the stability of structures with aggressive external influences, which have a complex probabilistic nature. The reliable functioning of bridge structures requires the development and application of modern systems for inspection and assessment of the technical condition of the structure to take timely measures to ensure the safe operation of the structure in changing operating conditions. With the rapid development of AI, modern approaches are increasingly adopted, offering distinct advantages compared to classical methods. The article aims to develop an AI-based model for quantifying the technical condition of bridge structural components based on data obtained from the survey. To achieve this goal, the authors analyzed existing approaches to the inspection and assessment of bridges and studied the experience of using AI in bridge assessment. Based on the Polish Principles of Bridge Technical Condition Assessment, three datasets were formed to quantify the condition of the bridge components made from reinforced concrete: bridge deck, span structures, and piers and abutments. This study created and compared the performance of five AI-based models: XGBoost, Decision Trees, Random Forest, Support Vector Regression, and Artificial Neural Networks (ANNs). The initial comparison revealed relatively low performance across all models, with the ANN model showing a slight advantage. Subsequently, nine ANN models were optimized to achieve higher performance levels. The performance of models was conducted based on a comparison of mean absolute percentage error (MAPE) and R² metrics. The ANN model with ReLU activation functions for hidden layers and the RMSprop optimizer achieves optimal performance at 100 epochs (MAPE = 3.5%; R² = 0.994). The practical implementation of such a model can considerably reduce uncertainties stemming from subjective expert judgments and enhance the accuracy of assessments. Full article

Background/Objectives: The long-term success of dental implants can be influenced by the material properties of abutments and their interaction with peri-implant tissues. This study investigates the impact of three abutment materials—titanium (Ti), zirconium oxide (Zr), and polymethylmethacrylate (PMMA)—on the inflammatory response in peri-implant sulcular fluid (PISF), using active-matrix metalloproteinase-8 (aMMP-8) as a biomarker. Methods: In this prospective, randomized clinical trial, 30 patients were assigned to Ti, Zr, or PMMA abutment groups. PISF samples were collected at predefined intervals over 12 months and analyzed for aMMP-8 levels using enzyme-linked immunosorbent assays (ELISA). Clinical parameters (probing depth, bleeding on probing, and plaque index) and radiographic assessments of bone resorption were also evaluated. Results: Two weeks after implant uncovering, baseline aMMP-8 levels varied significantly among materials, with Zr demonstrating the highest levels. Over time (2, 3, 6 and 12 months after implant uncovering), aMMP-8 levels decreased across all groups, with no significant differences observed at 12 months. Radiographic assessments indicated no statistically significant differences in bone resorption, with clinical parameters remaining comparable across all groups. Conclusions: Initial inflammatory responses to abutment materials may vary; however, all tested materials—Ti, Zr, and PMMA—showed long-term biocompatibility and supported healthy peri-implant tissue integration. These findings indicate that selecting any of the tested abutment materials does not significantly affect long-term peri-implant health. Full article

Due to the poor stability of the roof and floor of the roadway in the 3-1 coal seam of Chahasu Coal Mine, traditional gob-side entry retaining (GER) methods fail to meet the production safety requirements. To address this, a GER technology using paste backfill was proposed. This study reveals the stability mechanism of the surrounding rock in GER with paste backfill through theoretical analysis, numerical simulation, and industrial experiments. First, theoretical analysis was conducted to determine the overburden movement characteristics under varying backfill ratios. Uniaxial compressive tests on the paste material demonstrated that its bearing capacity reaches a relatively stable state after 14–28 days of curing. Second, numerical simulations were performed to study the deformation patterns of the surrounding rock and mine pressure characteristics under backfill ratios of 65%, 75%, 85%, and 95%. The Strain-Softening model was used to calibrate the backfill material parameters. The results showed that as the backfill ratio increased, the support provided by the backfill material improved, leading to enhanced bearing capacity of the overlying strata, reduced mine pressure intensity, significantly decreased deformation of the roadway, and substantially improved stability of the surrounding rock. Third, under a backfill ratio of 95%, the evolution of the abutment stress during face advancement was investigated. It was found that as the working face advanced, the backfill material and the overlying strata gradually formed a stable composite structure, with the abutment stress in the mining area stabilizing over time. Finally, to address the issue of insufficient initial strength and limited support capacity of the paste backfill material, a comprehensive control system for surrounding rock stability was proposed. This system integrates a basic bolt-mesh-cable support structure with localized reinforcement using portal hydraulic supports. Field industrial practices demonstrated that after applying this comprehensive control technology, the convergence of roof and floor was approximately 190 mm and the convergence of two ribs was about 140 mm, effectively ensuring the stability of surrounding rock in GER with paste backfill working face. Full article

Precambrian tropical glaciation is an enigma of Earth’s climate. Overlooking fundamental difference of land/sea icelines, it was equated with a global frozen ocean, which is at odds with the sedimentary evidence of an active hydrological cycle, and its genesis via the runaway ice–albedo feedback conflicts with the mostly ice-free Proterozoic when its trigger threshold was well exceeded by the dimmer sun. In view of these shortfalls, I put forth two key hypotheses of the tropical glaciation: first, if seeded by mountain glaciers, the land ice would advance on sea level to be halted by above-freezing summer temperature, which thus abuts an open cozonal ocean; second, a tropical supercontinent would block the brighter tropical sun to cause the required cooling. To test these hypotheses, I formulate a minimal tropical/polar box model to examine the temperature response to a varying tropical land area and show that tropical glaciation is indeed plausible when the landmass is concentrated in the tropics despite uncertain model parameters. In addition, given the chronology of paleogeography, the model may explain the observed deep time climate to provide a unified account of the faint young Sun paradox, Precambrian tropical glaciations, and Phanerozoic glacio-epochs, reinforcing, therefore, the uniformitarian principle. Full article