Polyvinylpyrrolidone (PVP; poly(N-vinylpyrrolidone)) is a versatile water-soluble polymer widely used in pharmaceuticals, coatings, and nanocomposites due to its solubility, biocompatibility, and film-forming properties. Despite its extensive applications, systematic kinetic data describing its thermal degradation remain limited. In this study, non-isothermal thermogravimetric analysis (TGA) of PVP was performed under nitrogen and air atmospheres at heating rates of 5, 10, 20, and 40 °C min⁻¹. Thermal profiles revealed three degradation stages: moisture loss (30–150 °C), main-chain scission and depolymerization (150–450 °C), and carbonaceous residue formation (>450 °C), with the principal decomposition peak at 370–410 °C. Activation energies (Eₐ) determined using Kissinger, Flynn–Wall–Ozawa (FWO), and Kissinger–Akahira–Sunose (KAS) methods ranged from 179 to 186 kJ mol⁻¹ and were validated using the Coats–Redfern model-fitting approach. Reaction orders (n ≈ 1.1–1.3) indicate random chain scission as the dominant mechanism. The resulting kinetic dataset provides reliable insight into PVP thermal stability and supports optimization of processing, recycling, and composite fabrication.

Polyvinylpyrrolidone (PVP) is a widely utilized polymer in pharmaceutical formulations, nanocomposites, biomedical devices, and membrane fabrication. Despite numerous thermogravimetric studies, detailed mechanistic insight into its volatile degradation products remains limited. This study aims to investigate the thermal decomposition mechanism of PVP using thermogravimetric analysis coupled with Fourier-transform infrared spectroscopy (TG–FTIR) under inert and oxidative atmospheres. Degradation stages, evolved gaseous species, and structural transformations were systematically analyzed between 30–800 °C. Results are expected to reveal multi-step degradation involving dehydration, pyrrolidone ring opening, backbone scission, and carbonaceous residue formation. Identification of CO₂, CO, amide fragments, vinylpyrrolidone monomers, and nitrogen-containing volatiles will clarify the degradation pathway. The study provides mechanistic confirmation complementary to kinetic models and enhances predictive understanding of PVP behavior during sterilization, extrusion, pyrolysis, and composite processing.

Polyvinylpyrrolidone (PVP) is a widely used water-soluble polymer with applications in pharmaceuticals, cosmetics, adhesives, and medical devices. Despite its versatility, the thermal stability of PVP remains a concern during processing and high-temperature applications, where degradation can compromise performance and safety. This study aimed to investigate the kinetic parameters of PVP thermal degradation using isothermal thermogravimetric analysis (TGA) over a temperature range of 30–800 °C. PVP samples were analyzed under a nitrogen atmosphere, and weight loss was recorded over time. Kinetic parameters, including activation energy (Ea) and pre-exponential factor (A), were determined, and molecular weight changes were evaluated via gel permeation chromatography. Results indicated multi-stage degradation with increasing Ea at higher temperatures, consistent with backbone scission and pyrrolidone ring decomposition. Molecular weight decreased progressively, and polydispersity increased, reflecting chain fragmentation. The study provides accurate isothermal kinetic data, contributing to better prediction of PVP behavior under thermal stress and guiding the design of thermally stable formulations

This study compared the retention of polyamide clasps engaging porcelain-fused-to-metal and zirconia retainers with identical 0.50 mm undercuts in posterior free-end saddle maxillary removable partial dentures. Four standardized acrylic resin models simulating maxillary bilateral posterior edentulous with first premolar abutments were prepared to receive either porcelain-fused-to-metal or zirconia crowns incorporating mesial occlusal rest seats. Polyamide RPA clasps were fabricated using an injection molding technique and tested for retention using a universal testing machine at a crosshead speed of 5 mm/min. The mean retention force of polyamide clasps was 6.68 ± 2.59 N for zirconia crowns and 5.47 ± 2.27 N for porcelain-fused-to-metal crowns. The results demonstrated minimal loss of retention for polyamide clasps against both ceramic materials, with no significant difference in retention related to the type of ceramic retainer.

Abstract:

This study aimed to compare the amount of stress generated on two versus four implants with equator attachments in maxillary implant overdentures with palatal coverage and palateless designs. Four standardized educational edentulous maxillary models simulating bone type II were used. The models were divided into two main groups according to palatal design (palatal coverage and palateless), and each group was further subdivided based on the number of implants (two or four implants). In the two-implant subgroup, implants were placed bilaterally in the canine regions perpendicular to the residual ridge using a surgical stent, whereas in the four-implant subgroup, implants were installed bilaterally in the canine and second premolar regions. Equator attachments with appropriate cuff heights were selected, and framework patterns were constructed. Four strain gauges were cemented to each fixture using strain gauge cement. A LLOYD digital loading device was used to apply compressive loads to measure the resulting stresses around the implants for each attachment configuration. The results demonstrated a statistically significant difference between stresses on two implants with equator attachments (74.53 ± 35.9 N/m × 10²) and four implants with equator attachments (10.85 ± 10.81 N/m × 10²) within the same palatal coverage design. Similarly, a statistically significant difference was found between stresses on two implants with equator attachments (123.75 ± 44.60 N/m × 10²) and four implants with equator attachments (14.51 ± 14.60 N/m × 10²) within the same palateless design. It was concluded that stress on two implants with equator attachments was markedly greater in the palateless design compared with the palatal coverage design, whereas stress on four implants with equator attachments was slightly greater in the palateless design than in the palatal coverage design, with no statistically significant difference.

Abstract

The study aimed to determine the prevalence of vitamin D and calcium deficiency in a sample of residents in the city of Gharyan, located in the western regions of Libya, based on 300 cases visiting laboratories and clinics and medical clinics in the city for the year 2025 AD, divided into two groups for both sexes with a number of (150) cases, for different age groups from (5-85) years The study reached results showing that vitamin D and calcium deficiency is widespread among cases for both sexes, as the percentage of vitamin D deficiency in males reached 29.34%, and in females it reached 25.66%, calcium deficiency was recorded at 25.34% in males and 24.66% in females. The highest prevalence of vitamin deficiency was recorded in the age group of (46-65) years, at 20.66% in males, and 25.33% in females. Followed by the age group from (26-45) years, with 29% of the total cases, 14.33% in males, and 14.66% in females. This is consistent with many studies conducted in some areas of the entire country, which confirmed that most of the population and different age groups suffer from a deficiency in the level of vitamin D and calcium, despite the country's location in an environmental zone suitable for the availability of sufficient sunlight However, due to some reasons of lack of health awareness, daily lifestyle and some social and dietary habits that have further exacerbated the problem of the spread of vitamin D and calcium deficiency among the population, the study recommended conducting intensive research and studies in various regions and following up on the cases of the population, spreading health awareness through various available means and holding scientific seminars and conferences for specialists, to educate society about the dangers of vitamin D and calcium deficiency on public health Changing habits and daily life patterns, conducting routine examinations, and following a healthy diet to reduce the increasing shortage rates among different age groups of the population.