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.

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.

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.

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.

Using the Finite Element Method to Determine the Odonto-Periodontal Stress for a Patient with Angle Class II Division 1 Malocclusion

The finite element method (FEM) is a computational method that can solve all biomechanical problems, including the field of orthodontics. The purpose of this virtual experimental study is to determine the behavior of a real orthodontic system subjected to different systems of loads. To analyze the real orthodontic system, we studied the case of a 21-year-old female patient. We used the InVesalius program, which can transform a set of DICOM-type images taken from cone beam computed tomography (CBCT) into three-dimensional structures. These structures were edited, modified, completed, and analyzed from a geometric point of view with the help of the Geomagic software. The final result of these operations must be a three-dimensional model made up of perfectly closed surfaces so that they can be transformed into virtual solids. The model consisting of perfectly closed surfaces is loaded into computer-aided design (CAD) programs. Bracket and tube components, as well as orthodontic wires, can be added to these models, similar to the analyzed patient's tissues. When the model is complete and geometrically correct, it is exported to a program that uses FEM, such as Ansys Workbench. The simulation was performed for the forces of 0.5, 0.6, 0.7, 0.8, 0.9, and 1 N. The intention was to determine the behavior of the entire orthodontic system for these force values. After running the simulations, result maps were obtained that were composed of displacement, strain, and stress diagrams. It was also found that, in addition to the known rigidity, the orthodontic system has some elasticity due to the orthodontic wires, as well as the periodontal ligaments. Thus, a virtual analysis study can be carried out starting from a real patient with pre-treatment CBCT images and the virtual models of the bracket and tube elements and of the orthodontic wires.

Histological and immunohistochemical aspects of the atrophic dental pulp modifications of abutment teeth

BACKGROUND

Reducing the thickness of hard dental tissues through the preparation of teeth for fixed prosthodontics represents an aggression for the dentin-pulp complex and may cause changes in dental pulp tissues, by means of acute or chronic inflammation, or by asymptomatic, atrophic modifications.

AIM

The aim of the study was to histological and immunohistochemical evaluate samples of dental pulp selected from previously prepared teeth, which had been functioning as abutment teeth for some years.

PATIENTS, MATERIALS AND METHODS

The starting point of the study was a statistical study conducted on a batch of 276 patients, of which 64 needed to change the fixed prosthetic restorations. Some of the existing abutment teeth were extracted, others presented previously performed root canal treatments and others required endodontic treatment.

RESULTS

Of the 21 samples taken, 12 showed atrophic pulp modifications, represented by low cellularity, collagen fibrosis, vascular congestion, and pulpal calcifications.

CONCLUSIONS

Certain irreversible atrophic changes can be observed in abutment teeth's pulps, a fact that justifies the need of performing pre-prosthetic endodontic treatment.

The Use of Colour Codes in Ceramics Build-up for Achievement Esthetic Anterior Restorations

The ability to mimic the optical characteristics of enamel and dentin, the excellent biocompatibility and the chemical durability of dental ceramics are the reason reasons why this topic is considered of great importance in dentistry. The aim of this study was to highlight the differences during the process of manufacturing anterior esthetic restorations, i.e. the proper selection of color shades of dental ceramics and their correct deposition.Techniques for performing aesthetic ceramic restorations are influenced by the experience of the dental technician and their skills in realizing the restoration, which should be as little complicated, even if the dental ceramic powders has coded shades of color. Some dental technicians prefer their own color labels in order to facilitate their work and to modify or to highlight some effects of the powders, during the dental ceramics build-up. Naturalness of eight anterior restorations was obtained by alternating the opalescent base layer of the dental ceramic and the fluorescence of crystalline layers subsequently applied over opaque. Different translucent type of ceramic layers was used in order to create the true aspect of the incisal area, with a natural halo appearance. The increasing expectations of the patients in aesthetic restoration of anterior area of dental arches demand a complex build-up of the porcelain layers and this technique requires that the dental technician to possess special skills for obtaining a successful result.

Root fractures: epidemiological, clinical and radiographic aspects

Chronic root fractures are a relative frequent dental condition, occurring both in vital teeth and in teeth with root canal treatment, with a difficult and frustrating diagnosis. Two clinical forms are described: crown-root fractures with crown origin and vertical root fractures with root origin. The aim of the study was to determine the prevalence of the root fractured extracted teeth in two dental clinics with different profile [oral rehabilitation (OR) and endodontics (E)] and to present some particular aspects of the root fractures. A retrospective study over a period of five years was performed to determine the number of extracted teeth and the motives for extraction. For root fractured extracted teeth were noted: fracture type, tooth vitality, restoration type. Although the number of the patients with tooth extractions in the five years period was significantly higher in OR clinic than in E clinic, the number of tooth extractions was almost similar. Most of the teeth (70.6%) were extracted for caries complications. The prevalence of the root fractured extracted teeth was 17.93%. In OR clinic, women had more root fractured extracted teeth compared with E clinic, where the number of root fractured extracted teeth was higher in men. Most extracted teeth for root fracture were teeth with prosthetic restorations followed by teeth with root canal treatment and dental fillings. The most extracted teeth for root fracture were maxillary premolars, almost similar for both sexes, followed by mandibular molars. The teeth with least extractions for root fractures were mandibular incisors and mandibular canine.

Optical coherence tomography applications in tooth wear diagnosis

Dental wear represents an irreversible loss of dental hard tissue under the action of physical, chemical and mechanical factors, excluding dental caries and acute trauma. Four clinical forms of dental wear are described: erosion, attrition, abfraction, and abrasion. Most experts agree that in each clinical form multiple etiological factors are involved, one being predominant. Optical coherence tomography (OCT) is a non-invasive optical method characterized by a micronic resolution. The applications of this type of investigation are multiple in the medical field in recent years, and OCT is gaining a growing importance in dentistry. The study pointed out through OCT imaging for the erosive tooth wear lesion the existence of chemical aggression, with strong demineralization of enamel and dentin. For attrition lesion, OCT images showed the contribution of excessive force and friction movements specific to bruxism. In abfraction, OCT image revealed the importance of the mechanic factor in producing this form of tooth wear and abrasion damage studied may be considered physiological, according to patient age. OCT examination may reveal existing lesions in hard dental tissues for each clinical form and could bring evidence on the mechanisms involved.

Histological and immunohistochemical study on the dental pulp of patients with diabetes mellitus

Diabetes mellitus is a disease that brings numerous alterations in the human body, mainly on the blood vessels and nervous system, its complications being difficult to treat most of the time. Oral complications are largely known and studied. Changes that occur in the dental pulp are of importance for the dentists, considering regular procedures outcome. In early stages of the disease, new blood vessels appear especially under the odontoblasts layer as a reaction to stimuli. In later stages, the defense systems of the dental pulp are outnumbered, nervous branches will be destroyed and disorganized. When periodontal disease occurs as well the mortification of the dental pulp will be faster.

The prevalence of crown injuries to frontal teeth at schoolchildren aged 6 to 14 and their effects on the periodontal tissue

The research aims at emphasizing the interrelation between the social impact and the self-esteem of schoolchildren with dental crown fractures in the frontal group. Dental traumatic injuries are frequently met to schoolchildren, therefore, the prevention and interception of traumatic pathology within parents, teachers and children is more than necessary. Our statistical study intends to determine the prevalence of dental trauma to southwestern Romanian schoolchildren aged 6 to 14. The survey included a number of 1684 schoolchildren attending public schools, randomly chosen. Data were collected from October 2012 to December 2013. Clinical examination was conducted to assess the dental traumatic injuries. Age and gender distribution, etiological factors, risk factors and the cause of injuries were the parameters taken into consideration. The data collected was processed and analyzed using the SPSS (Statistical Package for the Social Sciences) statistical software. The overall prevalence of dental trauma was 4.63% amongst the subjects examined. The maxillary central incisor was the most commonly affected tooth (85.19% in boys and 97.87% in girls). We observed a significant statistical difference in the number of children with one, two or three fractured teeth from the urban and rural areas. The percentage of schoolchildren with crown fractures that we examined was of 3.09% in the urban area and 1.54% in the rural area. The traumatic injuries of the maxillary upper teeth were most prevalent. Since the dental trauma of incisors has a strong impact on the quality of life of children and their families, health preventive policies are needed in order to avoid psychological implications on the lifelong existence of children affected.

Local cause of gingival overgrowth. Clinical and histological study

The overgrowth, depending on its extension, has multiple effects on the stomatognathic apparatus: functional disorders (impaired speech), difficulty in chewing and aesthetic problems but can cause significant psychological problems. We proposed this study, motivated by the relative increased frequency of the gum outgrowth, its multifactorial etiopathogeny, but especially from the point of view of the specialist practitioner, by the problems that this pathology raises not only for the functionality of the stomatognathic apparatus but also for the facial esthetics, and especially for future therapeutic attitudes needed to solve the existing pathology at this level. We conducted a clinical study and a histological one. For the clinical study, we selected 74 patients who experienced different degrees of gingival outgrowing associated with fillings, dental caries, fixed prostheses, mobile prostheses, orthodontic apparatus. Thirty gingival fragments from patients with gingival outgrowing were processed by paraffin-embedding histological technique and stained with Hematoxylin-Eosin. The morphological results obtained provide the necessary support for understanding the possibility of developing a therapeutic strategy to prevent or minimize the gum outgrowth by administering antibiotic and anti-inflammatory medications associated with medications, which shall cause the apoptosis of the fibroblasts.

Masticatory tensile developed in upper anterior teeth with chronic apical periodontitis. A finite-element analysis study

Commonly is accepted that a non-vital tooth has a higher risk of root fracture but there is a relatively little knowledge about the specific biomechanical behavior of non-vital frontal teeth with chronic apical periodontitis. The aim of our study was to evaluate the deformation and tensile generated in these teeth while vertically loading them because it is crucial to assess the moment when the absorbed occlusal forces exceed the elasticity of root dentine. Using the method of finite-element analysis, we highlighted the distribution patterns of the compressive and tension tensile, as well as their concentration areas. The vertical forces of 100 N generate deformations of no clinical risk in teeth with chronic apical periodontitis. The tensile developed in these teeth are higher than those in the vital teeth are but do not exceed the value of the elastic modulus of the radicular dentin. By increasing the force to 300 N occur elastic deformations, which cannot be neglected anymore. Even so, the 300 N forces do not generate deformations of the alveolar bone. The highest tensile at loading with 300 N was generated in vertical direction but in the cervical area of the tooth also developed tensile in lingual and mesiodistal direction that must be taken into consideration because they are near the risk limit of the elasticity modulus. The crack lines or fractures can appear both in case of excessive or even usual but accumulative occlusal forces that gradually alter the mechanical resistance of the tooth.