Search Results (6)

A screw-fixed superstructure is predominantly selected for implant prostheses because of the concern regarding developing peri-implantitis, although its infection route remains unclear. Focusing on microleakage from access holes, the present study clinically investigated the bacterial flora in access holes with different sealing materials. We examined 38 sites in 19 patients with two adjacent screw-fixed superstructures. Composite resin was used in the control group, and zinc-containing glass ionomer cement was used in the test group. Bacteria were collected from the access holes 28 days after superstructure placement and were subjected to DNA hybridization analysis. The same patient comparisons of the bacterial counts showed a significant decrease in 14 bacterial species for the red, yellow, and purple complexes in the test group (p < 0.05). In addition, the same patient comparisons of the bacterial ratios showed a significant decrease in six bacterial species for the orange, green, yellow, and purple complexes in the test group (p < 0.05). Furthermore, the same patient comparisons of the implant positivity rates showed a significant decrease in the six bacterial species for the orange, yellow, and purple complexes in the test group. The results of this study indicate that zinc-containing glass ionomer cement is effective as a sealing material for access holes. Full article

Patients undergoing implant treatment are at risk of peri-implant bone loss, which is most often caused by the adverse effects of microorganisms, but there are few proven procedures for their reduction. The aim of the research was to identify the microorganisms inhabiting the composites used to close the screw access hole (SAH), compare them numerically with those present on the surface of crowns and teeth, and optimize the doses of the diode laser, which will reduce microorganisms and will not deteriorate the roughness of polished composites. Patients were swabbed from the surface of SAH composites, from porcelain and zirconium restorations, and from teeth, and then the number of microorganisms was determined by using a culture technique. Microorganisms were identified by MALDI–TOF MS and NGS sequencing. The effectiveness of diode laser irradiation was achieved by using four variants of exposure. After polishing and laser irradiation, the surface roughness of the composites was studied by using optical profilometry. On the surface of SAH, 10⁶ to 10⁸ microorganisms were identified at 0.4 cm², including many pathogenic species. Among the materials used for the reconstruction of dental implants, the greatest microbiological contamination was found on the composites used to close the SAH. The diode laser with a wavelength of 810 nm with an average power of 3.84 W, during 60 s and 2 × 30 s, has a biocidal effect and does not significantly change the surface roughness of composites. The best reduction of microorganisms was achieved on a composite polished with a polishing rubber and then with a Sof-Lex™ Pre-Polishing Spiral beige (3M ESPE, Ave. St. Paul., MN, USA). Studies have shown that using the optimal laser dose can help treat periimplantitis. These studies provide important information on the possibility of the effective elimination of microorganisms by using a diode laser in the treatment of peri-implant bone loss. Full article

Background and Objectives: Oral implant restorations are an excellent treatment option for edentulous patients; however, periodontopathogenic bacteria have been found in the microgaps between implant−abutment junctions. Implant designs to limit the microgaps have been extensively studied. However, studies have shown microgaps continue to exist, allowing for the leakage of bacteria into the implant system. Screw access hole materials are used to fill the access hole void. The use of materials with beneficial properties could provide bacterial leakage prevention. The aim of this study was to examine the surface free energy, cytotoxicity, and bacterial adhesion of selected screw access hole materials such as cotton, polytetrafluoroethylene (PTFE) tape, paraffin wax−polyolefin thermoplastic (PF), paraffin wax (Wax), gutta-percha (GP), and caviton EX (CE). Materials and Methods: A sessile drop test was performed to observe the contact angle and calculate the surface free energy of each material in order to determine the level of hydrophobicity. Cytotoxicity was examined in a mouse gingival epithelial cell line for day 1 and day 3. Bacterial adhesion was tested with Porphyromonas gingivalis, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans. Results: PTFE, PF, and wax presented low surface free energies of 19.34, 23.041, and 24.883 mN.m-1, respectively. No cytotoxicity was observed, except for GP and CE. Concurrently, the bacterial adhesion was also the lowest in PTFE and PF. Conclusions: Within the limits of this study, PTFE and PF showed an excellent biocompatibility with few bacterial adhesions. These materials could be potential screw access hole materials in clinical settings. Full article

The versatility of steel, its high resistance in relation to its low mass, as well as the easily accessible technology in the context of using recyclable materials and the low negative impact on the environment represent important arguments in using thin-walled steel profiles to make structures for buildings with a low height regime. This paper presents the results of an experimental program that investigated the behavior of three types of joints in a T-shape form made of thin-walled steel profiles to make shear wall panels or truss beam floors. Due to the small dimensions of the C-profiles of 89 × 41 × 12 × 1 mm, and of the technology of their joining, manufacturers prefer the hinged connections of elements with self-drilling screws. The purpose of the research presented in this paper is to assess the maximum capacity of the joints, the elastic and post-elastic behavior until failure, and also the mechanisms failure. The types of joints analyzed are commonly used in the production of structural systems for houses. The experimental program, which consisted of testing 5 specimens for each type of joint in tension (shear on screws), showed different behavior in terms of load-displacement. The experimental, tested models were analyzed by finite element simulations in an ANSYS nonlinear static structure with 3D solid models. The materials were defined by a bilinear true stress–strain curve obtained after some experimental tensile tests of the steel. The results of the experimental tests showed that the main failure mechanism is a yielding of the holes where the screws were mounted and a shearing of the profile walls. Adding an additional screw on each side increases the capacity of the joints, but not until a yield loss is obtained. In conclusion, it is shown that the solution is suitable for a low level of loading in a static manner; however, additional studies are necessary in order to develop and verify other solutions, thus improving the strength of the connection. Full article

Introduction: Fixing fractures of the base and neck of mandibular condyles is demanding due to the difficulties in surgical access and the various shapes of bone fragments. Classic fixation techniques assume the use of straight mini-plates, utilized for other craniofacial bone fractures. Three dimensional mini-plates may provide a reasonable alternative due to their ease of use and steadily improved mechanical properties. The multitude of different shapes of 3D mini-plates proves the need for their evaluation. Aim: This paper aims to summarize the clinical trials regarding the use of various types of 3D condylar mini-plates in terms of need for reoperation and the incidence of loosening and damage to the osteosynthetic material. Materials and Methods: A systematic review was conducted in accordance with PICOS criteria and PRISMA protocol. The risk of bias was assessed using ROBINS-I and RoB 2 Cochrane protocols. The obtained data series was analyzed for correlations (Pearson’s r) respecting statistical significance (Student’s t-test p > 0.05) and visualized using OriginLab. Results: 13 clinical trials with low overall risk of bias regarding 6 shapes of 3D mini-plates were included in the synthesis. The number of reoperations correlates with the number of fixations (r = 0.53; p = 0.015) and the total number of screw holes in the mini-plate (r = −0.45; p = 0.006). There is a strong correlation between the number of loosened osteosynthetic screws and the total number of fractures treated with 3D mini-plates (r = 0.79; p = 0.001 for each study and r = 0.99; p = 0.015 for each mini-plate shape). A correlation between the percentage of lost screws and the number of distal screw holes is weak regarding individual studies (r = −0.27; p = 0.000) and strong regarding individual mini-plate shape (r = −0.82; p = 0.001). Three cases of 3D mini-plate fractures are noted, which account for 0.7% of all analyzed fixation cases. Discussion: The reasons for reoperations indicated by the authors of the analyzed articles were: mispositioning of the bone fragments, lack of bone fragment union, secondary dislocation, and hematoma. The known screw loosening factors were poor bone quality, bilateral condylar fractures, difficulties in the correct positioning of the osteosynthetic material due to the limitations of the surgical approach, fracture line pattern, including the presence of intermediate fragments, and mechanical overload. Fractures of the straight mini-plates fixing the mandibular condyles amounts for up to 16% of cases in the reference articles. Conclusions: There is no convincing data that the number of reoperations depends on the type of 3D mini-plate used. The frequency of osteosynthetic screw loosening does not seem to depend on the 3D mini-plate’s shape. Clinical fractures of 3D mini-plates are extremely rare. Full article