Assessment of the Cyclic Fatigue Performance of the Novel Protaper Ultimate File System Used in Different Kinematics: An In Vitro Study.

This in vitro study aims to assess the cyclic fatigue resistance of the Protaper Ultimate (PTU) files compared to the Protaper Gold (PTG) and the M3 UDG (M3) files using various motion kinematics in simulated canals. As far as the authors are aware, no study has previously compared the three file systems before this current investigation. Therefore, closing this information gap is the goal of the current research. Methods: A total of (60 new endodontic files were randomly divided into 6 groups (10 files per group); groups 1, 3, and 5 used continuous rotation (CR), while groups 2, 4, and 6 used forward reciprocating motion (FRM). A manufactured stainless-steel artificial canal was used to perform the cyclic fatigue testing. The results were analyzed using Student's t-test and two-way ANOVA. All pairwise comparisons revealed statistically significant differences in the time to failure (TTF) for every study group (p < 0.001), with the exception of the PTG and M3 files, which performed similarly using both CR and FRM. Conclusions: The PTU files performed better than the PTG and M3 files in terms of the TTF and number of cycles to failure (NCF) using both CR and FRM.

An In Vitro Study regarding the Wear of Composite Materials Following the Use of Dental Bleaching Protocols.

Composite materials used in dental restorations are considered resistant, long-lasting and aesthetic. As the wear of restorations is an important element in long-term use, the aim of this study was to evaluate the surface condition of nanohybrid and microfilled composite resins, after being subjected to the erosive action of dental bleaching protocols. This paper reflects a comparative study between one nanofilled composite and three microfilled composites used in restorations. For each composite, three sets of samples (under the form of composite discs) were created: a control group, an "office bleach" group with discs bleached with 40% hydrogen peroxide gel, and a "home bleach" group with discs bleached with 16% carbamide peroxide gel. Wear was numerically determined as the trace and the coefficients of friction obtained using a tribometer, the ball-on-disk test method, and two balls: alumina and sapphire. For all composite groups, there were statistically significant differences between the wear corresponding to the control and bleaching groups, for both testing balls. Regarding the composite type, the largest traces were recorded for GC Gradia direct anterior, for all groups, using the alumina ball. In contrast, for the sapphire ball, 3M ESPE Filtek Z550 was characterized by the largest traces. With respect to the friction coefficients, the "office bleach" group recorded the largest values, no matter the composite or the ball type used. The 3M ESPE Valux Plus composite recorded the largest friction coefficients for the alumina ball, and 3M ESPE Filtek Z550 for the sapphire ball. Overall, the "office bleach" group was characterized by higher composite wear, compared to the "home bleach" protocol or control group. Nanofilled composite resins showed superior wear resistance to microfilled resins after undergoing a bleaching protocol.

Effects of Dental Bleaching Agents on the Surface Roughness of Dental Restoration Materials.

Background and Objectives: This study aimed to evaluate the surface roughness evolution of several finished and polished composites when bleaching materials are applied. The research was conducted on four microhybrid or nanofilled composites that are used in dental restorations. Materials and Methods: For each composite type, 5 samples were selected for control, 5 samples were subjected to the bleaching protocol "office bleach" with 40% hydrogen peroxide, and 5 other samples were subjected to the "home bleach" protocol with 16% carbamide peroxide, resulting in a total number of 60 samples. The surfaces of all the samples were tested for roughness, and the values of the most relevant parameter (Ra), were collected. Comparisons between composites and samples were performed using one-way ANOVA (in Statistical Package for Social Sciences). Results: After the bleaching protocol with 40% hydrogen peroxide gel, it was found that the roughness of the group increased considerably compared to the control group, so the highest roughness was found at GC Gradia direct anterior group, and the lowest value was registered for the 3M ESPE Valux Plus group. Following the bleaching protocol with 16% carbamide peroxide (home bleach), it was noted that the sample surfaces were not as affected. In this case, the lowest roughness was found at 3M ESPE Valux Plus group, and the highest roughness was registered for the GC G-aenial anterior group. Following the interpretation of the results, all four types of dental composites tested showed significant surface roughness differences between the groups subjected to bleaching protocols and those kept as control (p < 0.05). Conclusions: The surfaces of the samples were affected by the bleaching protocols by increasing the roughness compared to the control samples.

Analysis of Temperatures Generated during Conventional Laser Irradiation of Root Canals-A Finite Element Study.

The success of endodontic treatment is dependent on the removal of bacteria. A modern strategy to reduce bacterial load is laser irradiation. During this procedure, there is a local increase in temperature with possible side effects. The aim of this study was to determine the thermal behavior of a maxillary first molar when performing the conventional irradiation technique using a diode laser. For this study, a 3D virtual model of a maxillary first molar was created. The preparation of the access cavity, the rotary instrumentation of the palatal root canal and the laser irradiation protocol were simulated. The model was exported in a finite element analysis program where the temperature and heat flux were studied. Temperature and heat flux maps were obtained, and the temperature increase on the internal wall of the root canal was analyzed. The maximum temperature value exceeded 400 °C and was maintained for less than 0.5 s. The obtained temperature maps support the bactericidal effect of diode laser and the limitation of damage to surrounding tissues. On internal root walls, the temperature reached several hundred degrees Celsius, but for very short durations. Conventional laser irradiation is an adjuvant method of decontamination of the endodontic system.

Post Placement and Restoration of Endodontically Treated Canines: A Finite Element Analysis Study.

The purpose of this study was to show the improved outcomes of restoring endodontically treated teeth with fiberglass posts compared to restorations using metal posts. In our study, we used the Finite Element Method (FEM), which is based on the principle that a physical model that supports a given load distributes the stress throughout its volume. We sought to assess what stress results in a tooth when it is restored using a fiberglass post compared to restoration using a metal post. The finite element analysis showed that a system consisting of a tooth with a fiberglass post is more stable in terms of the maximum stress than a system consisting of a tooth with a metal post. The maximum displacements and deformations were obtained in the case of a canine restored with a fiberglass post, which showed that this system had a high elasticity, therefore, higher strength than a canine restored with a metal post, which had high rigidity.

Diabetes mellitus: Plasticizers and nanomaterials acting as endocrine-disrupting chemicals (Review).

Various plasticizers and nanomaterials have been linked to endocrine disruptors or endocrine-disrupting chemicals (EDCs) which represent a large, heterogeneous, yet incompletely understood group of structures acting on normal and pathological body pathways such as hormonal production, secretion, transport and receptor binding. By contrast, various applications of nanoparticles are currently under investigation since the delivery of useful drugs, particularly insulin in diabetes mellitus, is essential in case of insulin deficiency. The aim of the present review was to introduce and examine different plasticizers and nanomaterials with potential applications for diabetic patients (such as selenium or gold-based nanoparticles that help the oral delivery of insulin) or plasticizers/nanomaterials acting similarly to EDCs in relation to the human and animal body, particularly glucose metabolism impairment such as diabetes mellitus (DM). Bisphenol A is a chemical used worldwide; however, the effect of exposure varies with regard to the source, environment, time of exposure and the age of the organism. Daily exposure is mostly related to food and drinks stored in polycarbonate plastics. However, exposure may also be through the skin or through the maternal placenta or breast milk which are risk factors for the fetus and for the newborn. It exerts an estrogen-like profile, but it also induces insulin resistance by impairing peripheral insulin receptors or it decreases insulin secretion by acting at the level of insulin-secreting pancreatic ß-cells. Phthalates, compounds of flexible plastics, act as EDCs via their human metabolites such as diethyl phthalate and derivative monoethyl phthalate. Their role in inducing gestational DM and weight gain/obesity during pregnancy has been showcased. The vast field of plasticizers and nanomolecules acting as endocrine disruptors is widely linked to clinical aspects of DM, a serious condition with a major population impact. The importance of understanding and using these agents and applications is reflected in saving numerous human lives.

Correlations between periodontal indices and osteoporosis.

In the pathogenesis of chronic periodontitis, there are general systemic factors which play a major role, such as osteoporosis, with menopause as the most common etiological factor, and other pathological determining conditions for osteoporosis as well (ovary, thyroid and malignant tumors). The aim of the present study was to assess the correlations between periodontal indices and osteoporosis. The study was performed on 35 patients with periodontal disease aged between 45 and 79 years. These patients were divided into two groups: a study group with osteoporosis and periodontal disease (n=25) and a control group with periodontal disease (n=10) only. The periodontal assessment included community periodontal index (CPI), gingival inflammation index (GI), plaque index (PI), body mass index (BMI), bone mineral density (BMD), tooth mobility and tooth loss. Osteoporosis was assessed by dual-energy X-ray absorptiometry. Results were statistically analyzed with Microsoft Excel software and XLSTAT. The results showed that patients in the study group had higher values of periodontal indices, and a highly significant inverse correlation was observed between the CPI and the tooth loss. Inverse correlations between BMI and tooth mobility, as well as BMI and CPI were determined for the study group. In conclusion, the positive association between BMD and GI shows that the gingival index can be a predictive factor in the occurrence of osteoporosis.