Analytical Modeling of the Interaction of a Four Implant-Supported Overdenture with Bone Tissue

The study of the base resin impact on planktonic growth of microorganisms of oral origin

OBJECTIVE

Aim: To study the main differences in the intensity of growth of microbial strains of oral origin when they are cultivated in the presence of base resins that are widely used in the clinic of prosthetic dentistry.

PATIENTS AND METHODS

Materials and Methods: 3 types of base resin samples were used to evaluate the impact on the growth of microorganisms. Strains of opportunistic pathogens representing the facultative anaerobic transient microflora of the oral cavity were used for the research. Microbial cultures were isolated from the oral mucosa of the patients with removable dentures. The optical density of the culture was determined using a multi-mode photometer. Control growth of the cultures was evaluated under similar cultivation conditions in test tubes with a nutrient medium without resin samples.

RESULTS

Results: All resins reduced the intensity of polyantibiotic-resistant S. aureus MRSA growth compared to control samples. The impact on S. epedermidis growth was different. Thus, Vertex and Вreflex reduced the growth intensity insignificantly, and Villacryl increased it to the level of 1.104 ±0.026 CU in comparison with glass constituting 1.178 ±0.033 CU. All studied resins inhibited the growth of polyantibiotic-resistant S. aureus MRSA. Villacryl resin had the least impact on the growth of S. epedermidis. Villacryl resin inhibited C. albicans growth only by 13.70%, and the other two resins inhibited it by 25% on average.

CONCLUSION

Conclusions: The conducted microbiological studies showed the diverse influence of base materials on such important indicators as the optical density of cultures grown in the presence of base resins and the growth inhibition index of cultures.

A Biomechanical Evaluation of Distal Tilting Implants in All-on-Four Rehabilitation with Mild Mandibular Resorption: A Finite Element Analysis Study

The geometry of implants plays a crucial role in the success of All-on-Four treatments for the lower jaw. This study builds upon prior research by evaluating the biomechanical performance of implant-supported prostheses in full-arch fixed dental restorations, specifically focusing on different implant lengths and connection types in cases of mild atrophic resorption of the mandible. Four groups were analyzed using finite element analysis (FEA): We utilized 13 or 18 mm posterior 17-degree tilting implants, each paired with two kinds of abutment connections. The external hexagon connection (EHC) group utilized 4 mm diameter implants, while the internal hexagon connection (IHC) group employed 4.3 mm diameter implants. A vertical force was applied to the cantilever region located at the distal side of the posterior implant. The maximum stress regions were observed in prosthetic screws and multi-unit abutments (MUAs) across all groups, with the lowest von Mises stress values noted in the bone. Stress peaks for implant screws and fixtures in the 13 mm group were 19.98% and 11.42% lower, respectively, compared to the IHC group. Similarly, in the 18 mm group, stress peaks were reduced by 33.16% and 39.70% for the EHC group compared to the IHC group. The stress levels on all components remained below the ultimate strength of the titanium alloy. For the same implant lengths, the stress in the prosthetic screw, MUAs, implant screw, and implant fixture positions was lower in the EHC group. When implant length was increased, a decrease in stress levels was observed in the implant screw and fixture of the EHC group and only in the implant screw of the IHC group. However, an increase in stress was noted in the prosthetic screw and MUAs for both groups.

Mechanism of Casing String Curvature Due to Displacement of Surface Strata

One of the main problems of well operation is the risk of uncontrolled leakage of hydrocarbons into the environment. This problem is especially relevant for the long-term operation of wells. The idea for this study was inspired by a real industrial problem that the authors of the article were involved in solving. At several operating gas wells, an abnormal slope of the production tree occurred, which raised the question of the safety of their further operation. An analysis of known studies and current regulatory documents did not allow us to assess the safety of using a gas well based on the measured kinematic parameters of production tree deviations. A mathematical model for the deformation of a package of casing strings when the surface layer of the rock is displaced is developed in the article. A boundary value problem is formulated for differential equations of pipe bending on an elastic foundation. Based on the results of solving this problem, an unambiguous relationship was established between the maximum bending stress in the surface pipe and the angle of inclination of the production tree. The quantitative characteristics of the connection depend on the geometric and mechanical properties of the pipes and on the thickness and mechanical parameters of the formations. It was established that the existing inclination of the production tree can be achieved due to the beginning of the plastic bending of the surface pipe under the slickenside, which does not exclude the exhaustion of the safety margin of the surface pipe and indicates the possible operation of the casing string in a pre-emergency state. In general, the obtained results develop analytical approaches to assessing the behavior of underground structures of a production well in unstable soil bodies.

Determining the Tightrope Tightening Force for Effective Fixation of the Tibiofibular Syndesmosis during Osteomeatal Synthesis of Fibula Injuries

The issue of choosing the method for optimal surgical treatment of a broken fibula has been debatable for many years. At the same time, concomitant repair of tibiofibular syndesmosis injuries does not have a unified approach. It has been determined that osteosynthesis of broken shin bones with syndesmosis injury should combine stable fixation of the broken bone and should not limit the elastic properties of the syndesmosis. In case of a broken fibula, it is recommended to use a stable extracortical fixator and an elastic connection of the syndesmosis injury using a tightrope. An analytical model of the broken fibula, which is blocked with an extracortical fixator metal plate and elastically fixed with a tightrope, has been developed. The research object is the stress–strain state of the “broken fibula–extracortical titanium plate” composition under the action of tightrope tightening fixation. The main research result is an analytical dependence, which makes it possible to determine the permissible value of the tightrope tightening force for elastic fixation of the tibiofibular syndesmosis. The research results have been tested numerically, and the influence of the parameters of plate, bone and damage localization on the permissible value of the tightrope tightening force has been analyzed. By using the rational tightrope tightening force with stable–elastic fixation of the broken shin, it is possible to reduce the time before the start of loading on the injured extremity and accelerate the functional recovery of the patient.