A Finite Element Method Study on a Simulation of the Thermal Behaviour of Four Methods for the Restoration of Class II Cavities.

The possibility of dental pulp damage during dental procedures is well known. According to studies, during finishing and polishing without cooling, temperatures of up to 140 °C or more can be generated. There are many studies that have analysed the influence of the finishing and polishing of fillings on the mechanical parameters, but the analysis of thermal parameters has led to uncertain results due to the difficulty of performing this in vivo. Background: We set out to conduct a study, using the finite element method, to determine the extent to which the type of class II cavity and the volume of the composite filling influence the duration of heat transfer to the pulp during finishing and polishing without cooling. Materials and Methods: A virtual model of an upper primary molar was used, with a caries process located on the distal aspect, in which four types of cavities were digitally prepared: direct access, horizontal slot, vertical slot and occlusal-proximal. All four cavity types were filled using a Filtek Supreme XT nanocomposite. Results: The study showed that the filling volume almost inversely proportionally influences the time at which the dental pulp reaches the critical temperature of irreversible damage. The lowest duration occurred in occlusal-distal restorations and the highest in direct access restorations. Conclusions: based on the results of the study, a working protocol can be issued so that finishing and polishing restorations without cooling are safe for pulpal health.

Study on the Restoration of Class II Carious Cavities by Virtual Methods: Simulation of Mechanical Behavior.

The restoration of class II cavities is predominantly carried out with composite materials. Due to the high failure rate in restoring this type of cavity, composite materials with much-improved properties and new application techniques have been promoted. The study aimed to analyze the mechanical behavior of several topical composite materials (nanocomposites, nanohybrids and ormocer) using different application techniques. In a lower second molar, a class II occlusal cavity was prepared. As filling materials, we used the following combinations: Admira Fusion and Admira Fusion Flow, Grandio and Grandio Flow, Filtek Supreme XT and Filtek Supreme Flow. These were applied using a snow plow, injection molded and Bichacho techniques. Three-dimensional scanning of the molar with the prepared cavity was performed, and then scanning of each layer of added composite material was performed, obtaining three-dimensional models. The virtual molar models were analyzed with software specific to the finite element analysis method, where their physical-mechanical properties were entered and assigned to the components of the virtual molar. Simulations at high forces specific to bruxism were then carried out and analyzed, and compared. The values of displacements and strain, for all six analyzed situations, are relatively small (range from 5.25 × 10-6-3.21 × 10-5 for displacement, 6.22 × 10-3-4.34 × 10-3 for strain), which validates all three methods and the materials used. As far as the stress values are concerned, they are similar for all methods (250-300 MPa), except for the snow plow and injection-molded techniques using Grandio and Grandio Flow composites, where the maximum von Mises stress value was more than double (approximately 700 MPa). When using the combination of Grandio and Grandio Flow materials, the 1 mm thickness of the fluid composite layer was found to have a major influence on occlusal forces damping as opposed to 0.5 mm. Therefore, the Bichacho technique is indicated at the expense of the snow plow and injection-molded techniques. The composite materials used by us in this study are state-of-the-art, with clear indications for restoring cavities resulting from the treatment of carious lesions. However, their association and application technique in the case of Class II cavities is of clinical importance for resistance to masticatory forces.

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.

Importance of radiological examination in the evaluation of canal fillings performed with bioceramic sealers.

Bioceramic-based fillers have been evaluated in several in vitro studies but in vivo studies are still limited. The present study examined 36 postoperative radiographic analyses that were divided into four groups, of which three used bioceramic-based fillers, namely Total Fill, BioRoot RCS and Biodentine, while the fourth group was used as control and implemented the resin-based AH Plus Jet sealer. The present results did not indicate significant differences in radiopacity between sealers at a certain level of obturation. Biodentine-based fillers have a radiodensity close to that of dentin, which makes it difficult for the physician to radiologically assess the correctness of the canal filling.

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.

Clinical, histopathological and immunohistochemical changes of the superficial marginal periodontium caused by orthodontic treatment with fixed metallic orthodontic appliances.

Malocclusions negatively influence dental function, physical well-being, and quality of life. According to data provided by the World Health Organization (WHO), malocclusions represent the third most widespread oral health problem, after dental caries and periodontal diseases. In recent years, more and more people call for orthodontic treatment with fixed braces that aim at establishing a dental, aesthetic, and functional balance, compatible with a normal life. Our study assessed the histopathological and immunohistochemical changes that occurred in superficial marginal periodontal components, in a number of 23 patients diagnosed with malocclusions, as a result of orthodontic treatment with fixed metal braces. The purpose of the study was to evaluate the remodeling of the tissues in the superficial periodontium during orthodontic migration, microscopic aspects that are essential to evaluate the effectiveness of the orthodontic treatment.

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.

A rare case of osteoma in the frontal sinus: anatomical and histological description.

PURPOSE: The purpose of this paper is to present a rare case of osteoma localized in the left frontal sinus. A 22-year-old woman who arrived at the Department of Neurosurgery of the University Emergency Hospital, Bucharest, Romania, presented a vertical asymmetry of the eyeballs but displayed no clinical signs like pain or diplopia. The computer tomography exam was used for preoperatory diagnostic. Histopathology was performed after surgery using Hematoxylin and Eosin staining. The Nikon Eclipse microscope was used to examine the slides. RESULTS: The histopathology exam shows a compact osteoma with dense and non-Haversian bone tissue and parallel bony trabeculae. A few spaces for the marrow were also found. The osteocytes were small and no fibrous cells were discovered. CONCLUSIONS: The computer tomography and histopathology exam were the investigations that lead us to a true diagnostic of dense osteoma. This tumor was the first case of frontal sinus osteoma histologically described in the Romanian population.