Mechanical Assessment of Denture Polymers Processing Technologies.

BACKGROUND: Removable prostheses have seen a fundamental change recently because of advances in polymer materials, allowing improved durability and performance. Despite these advancements, notable differences still occur amongst various polymer materials and processing technologies, requiring a thorough grasp of their mechanical, physical, and therapeutic implications. The compressive strength of dentures manufactured using various technologies will be investigated. METHODS: Traditional, injection molding, and additive and subtractive CAD/CAM processing techniques, all utilizing Polymethyl methacrylate (PMMA) as the main material, were used to construct complete dentures. The specimens underwent a compressive mechanical test, which reveals the differences in compressive strength. RESULTS: All the specimens broke under the influence of a certain force, rather than yielding through flow, as is characteristic for plastic materials. For each specimen, the maximum force (N) was recorded, as well as the breaking energy. The mean force required to break the dentures for each processing technology is as follows: 4.54 kN for traditional packing-press technique, 17.92 kN for the injection molding technique, 1.51 kN for the additive CAD/CAM dentures, and 5.9 kN for the subtractive CAD/CAM dentures. CONCLUSIONS: The best results were obtained in the case of the thermoplastic injection system and the worst results were recorded in the case of 3D printed samples. Another important aspect depicted is the standard deviation for each group, which reveal a relatively unstable property for the thermoplastic injected dentures. Good results here in terms of absolute property and stability of the property can be conferred to CAD/CAM milled group.

Conventional Dental Impressions vs. Impressions Reinforced with Rigid Mouthguards.

The impression materials utilized today in dental medicine offer a good reproducibility and are easily accepted by patients. However, because they are polymer-based, they have issues regarding their dimensional stability. In this respect, the present work proposes a new type of dental impression, which is reinforced with rigid mouthguards. The aim of the study is to test the performances of such new impressions by comparing them to conventional ones-from this critical point of view, of the dimensional stability. Three types of polymeric materials were considered for both types of impressions: alginate, condensation silicone, and addition silicone. In order to obtain the new type of impressions, a manufacturing technique was developed, comprising the following phases: (i) conventional impressions were made; (ii) a plaster model was duplicated, and 15 rigid mouthguards were obtained; (iii) they were inserted in the impression technique, with each mouthguard positioned on the cast before the high-consistency material was inserted in the tray and the practitioner took the impression; (iv) the mouthguard remained in the tray and the low-viscosity material was inserted over the mouthguard; (v) the impression was positioned on the model, and after the material hardened, the mouthguard-reinforced impression was analyzed. In the evaluation of the dimensional stability, rigorous statistical analysis was essential to discern the performance differences between conventional and mouthguard-reinforced dental impressions. Statistical analyses employed non-parametric Mann-Whitney U tests because of the non-normal distribution of the data. They indicated a statistically significant improvement in the dimensional stability of addition silicone impressions when reinforced with mouthguards (p < 0.05), showcasing superior performance over conventional methods. Conversely, alginate and condensation silicone reinforced impressions did not exhibit the same level of stability improvement, suggesting the need for further optimization of these materials. In conclusion, from the three considered elastomers, addition silicone was found to be the prime candidate for high-precision dental impressions, with the potential to improve their quality from conventional impressions by utilizing the proposed reinforcing technique.

Micro-CT and optical microscopy imagistic investigations of root canal morphology.

Protecting the root's internal morphology is the first key toward the success of the endodontic treatment. Due to the vast diversity of endodontic space, it is difficult to visualize and to establish the shape and limits of the root canal, especially the morphology of apical area and lateral root canals. Optical microscopy is a classical imagistic investigation method, widely used along classical methods like radiographs that also offer limited information about root morphology and extension of decay. Micro-computed tomography (micro-CT), a modern imagistic investigation method can provide detailed three-dimensional reconstructions of root canal. Micro-CT is a non-invasive method that has the possibility to offer cross-sectional and axial images of the endodontic space. The success of root canal treatment is based on cleaning and shaping. Beyond these two procedures, sealing the endodontic space by respecting its limits is another prerequisite for long-term success of endodontic therapy. Micro-CT can perform three-dimensional reconstruction of the root canal, root canal filling and can provide accurate images of the endodontic space. The assessment of root morphology can be obtained through imagistic invasive optical microscopy and already mentioned non-invasive methods (micro-CT). The aim of this study is to illustrate and analyze the endodontic space, according to its diversity by using micro-CT, a non-invasive imagistic investigation method an also optical microscopy. The two techniques can also provide the extension of carries or demineralized substance on different levels of the root.