Dental Resin-Based Luting Materials-Review.

As cementation represents the last stage of the work involved in making various indirect restorations (metal ceramic crowns and bridges, full ceramic crowns and bridges, inlays, onlays, and fiber posts), its quality significantly contributes to the clinical success of the therapy performed. In the last two decades, the demand for ceramic indirect restorations in everyday dental practice has considerably increased primarily due to the growing significance of esthetics among patients, but also as a result of hypersensitivity reactions to dental alloys in some individuals. In this context, it is essential to ensure a permanent and reliable adhesive bond between the indirect restoration and the tooth structure, as this is the key to the success of aesthetic restorations. Resin-based luting materials benefit from excellent optical (aesthetic) and mechanical properties, as well as from providing a strong and durable adhesive bond between the restoration and the tooth. For this reason, resin cements are a reliable choice of material for cementing polycrystalline ceramic restorations. The current dental material market offers a wide range of resin cement with diverse and continually advancing properties. In response, we wish to note that the interest in the properties of resin-based cements among clinicians has existed for many years. Yet, despite extensive research on the subject and the resulting continued improvements in the quality of these materials, there is still no ideal resin-based cement on the market. The manuscript authors were guided by this fact when writing the article content, as the aim was to provide a concise overview of the composition, properties, and current trends, as well as some future guidelines for research in this field that would be beneficial for dental practitioners as well as the scientific community. It is extremely important to provide reliable and succinct information and guidelines for resin luting materials for dental dental practitioners.

A New Mechanical Mouth Opener for Dynamic Magnetic Resonance Imaging of the Temporomandibular Joint.

(1) Background: During the magnetic resonance imaging (MRI) of the temporomandibular joint (TMJ), it is necessary to scan the joints in the closed- and open-jaw position, as well as in the maximally open-jaw position. In order to examine both joints in these positions, an MRI compatible mouth opener is required, which allows the articular surfaces to maintain their position stably. (2) Methods: In this study, we included 200 patients aged 18 to 65, with various levels of clinical severity. The mouth opener is made of polymethyl methacrylate and used for dynamic imaging of TMJ. It is in the form of an arrow, with incisures on upper and lower surfaces 1 mm apart and these match possible variations in jaw opening. All the patients were scanned with mouth opener and, immediately after this scanning, with syringe (20 ccm) as a standard device used for mouth opening in clinical setting. (3) Results: A total of 200 MR examinations of TMJs were performed and the mechanical mouth opener was successfully applied without artifacts in all patients. The mouth opener device proved to be adequate in case of MRI of the TMJ for different ranges of mouth opening with the proper protocol for provoked imaging, because the incisures are located at a distance of 1 mm and no objective artifacts were observed in any examination that degraded the diagnostic quality of the examination. (4) Conclusions: The design of the acrylate mouth opener is precisely defined, and it has a purpose in the MRI diagnosis of TMJ disorders.

High-Field Magnetic Resonance Imaging of the Temporomandibular Joint Low Agreement with Clinical Diagnosis in Asymptomatic Females.

(1) Background: The aim of this study was to investigate the agreement between a clinical diagnosis based on research diagnostic criteria/temporomandibular disorders (RDC/TMD) and high-field magnetic resonance imaging (MRI) findings of temporomandibular joints (TMJs) in asymptomatic females. (2) Methods: A prospective study on 100 females (200 TMJs) was performed, using clinical examinations (RDC/TMD) and same-day MRIs of TMJs on a 3T MR unit. The inclusion criteria were as follows: females, age > 18, the presence of upper and lower incisors, and an understanding of the Serbian language. Descriptive statistics (means and standard deviations) and ANOVA with a post hoc Tukey test for differences among the patient subgroups was performed. The agreement between the clinical and MRI findings was determined using Cohen's kappa coefficient (k < 0.21 slight, 0.21-0.4 fair, 0.41-0.6 moderate, 0.61-0.8 substantial, and 0.81-1 almost perfect). The statistical significance was set at p ≤ 0.05. (3) Results: Normal findings were observed in 86.7%, disc dislocation (DD) was observed in 9.2%, and arthralgia/osteoarthritis/osteoarthrosis was observed in 2.6% of TMJs using RDC/TMD. On the MRI, normal findings were observed in 50.5%, disc dislocation was observed in 16.3%, and arthralgia/osteoarthritis/osteoarthrosis was observed in 23.5% of TMJs. The anterior DD with reduction showed fair agreement of the clinical and MRI findings (k = 0.240, p < 0.001) compared with the DD without reduction (k = 0.355, p < 0.001). Both showed high specificity (94.9% and 99.4%) but low sensitivity (24.2% and 25.0%). The sensitivity in osteoarthritic changes was low (4.8%), but the specificity remained high (96.2%). (4) Conclusions: The sensitivity of the clinical examination remains low compared with 3T MRI, especially in osteoarthritic changes and anterior DD with reduction. However, the number of false positive diagnoses using RDC/TMD is low in asymptomatic patients. RDC/TMD remains a sensible method for establishing a clinical diagnosis and avoiding the overtreatment of asymptomatic patients.

Development of Light-Polymerized Dental Composite Resin Reinforced with Electrospun Polyamide Layers.

As the mechanical properties of resin-based dental composite materials are highly relevant in clinical practice, diverse strategies for their potential enhancement have been proposed in the extant literature, aiming to facilitate their reliable use in dental medicine. In this context, the focus is primarily given to the mechanical properties with the greatest influence on clinical success, i.e., the longevity of the filling in the patient's mouth and its ability to withstand very strong masticatory forces. Guided by these objectives, the goal of the present study was to ascertain whether the reinforcement of dental composite resins with electrospun polyamide (PA) nanofibers would improve the mechanical strength of dental restoration materials. For this purpose, light-cure dental composite resins were interspersed with one and two layers comprising PA nanofibers in order to investigate the influence of such reinforcement on the mechanical properties of the resulting hybrid resins. One set of the obtained samples was investigated as prepared, while another set was immersed in artificial saliva for 14 days and was subsequently subjected to the same set of analyses, namely Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). Findings yielded by the FTIR analysis confirmed the structure of the produced dental composite resin material. They also provided evidence that, while the presence of PA nanofibers did not influence the curing process, it strengthened the dental composite resin. Moreover, flexural strength measurements revealed that the inclusion of a 16 µm-thick PA nanolayer enabled the dental composite resin to withstand a load of 3.2 MPa. These findings were supported by the SEM results, which further indicated that immersing the resin in saline solution resulted in a more compact composite material structure. Finally, DSC results indicated that as-prepared as well as saline-treated reinforced samples had a lower glass transition temperature (Tg) compared to pure resin. Specifically, while pure resin had a Tg of 61.6 °C, each additional PA nanolayer decreased the Tg by about 2 °C, while the further reduction was obtained when samples were immersed in saline for 14 days. These results show that electrospinning is a facile method for producing different nanofibers that can be incorporated into resin-based dental composite materials to modify their mechanical properties. Moreover, while their inclusion strengthens the resin-based dental composite materials, it does not affect the course and outcome of the polymerization reaction, which is an important factor for their use in clinical practice.

Influence of Implant Impression Methods, Polymer Materials, and Implant Angulation on the Accuracy of Dental Models.

The paper presents the influence of impression methods, polymer materials, and implant angulation on the accuracy of the definitive working model for the production of implant-supported dental restorations, based on the analysis of results obtained using different impression methods, materials, and parallel and angulated implants. The study findings indicate that all aforementioned factors impact the accuracy of the definitive working model. Specifically, 20° implant angulation in relation to the vertical plane has a greater impact on the impression accuracy compared to parallel implants. The open and splint method in combination with addition silicone, as well as the splint method and polyether combination yielded more accurate results when using implants under 20° angulation compared to other method and material combinations. The splint method in combination with addition silicone resulted in the smallest mean deviations from the center of the parallel implant base compared to other combinations of methods and materials. Analysis results further revealed statistically significant differences in the measured indicators across impression methods, implants, and polymer materials.

Influence of Dimethacrylate Monomer on the Polymerization Efficacy of Resin-Based Dental Cements-FTIR Analysis.

The degree of polymerization for dimethacrylate resin-based materials (BisGMA, TEGDMA, UDMA, HEMA) ranges from 55 to 75%. Literature data indicate that polymerization efficacy depends, among other factors, on the type of methacrylate resin comprising the material. The aim of this study was to evaluate the polymerization efficacy of four dental cement materials characterized by different polymerization mechanisms using FTIR analysis. In the present study, the FTIR method was adopted to analyze the degree of polymerization efficacy of four resin-based dental cement materials, two of which were self-cured and two were dual-cured cements. The IR spectral analysis was performed 24 h after the polymerization of the cementitious material. RelyX ARC cement exhibits the lowest polymerization efficacy (61.3%), while that of Variolink II (85.8%) and Maxcem Elite is the highest (90.1%). Although the efficacy of self-cured cements appears to be superior, the difference is not statistically significant (p = 0.280). Polymerization efficacy largely depends on the chemical structure of the material in terms of the presence of a particular methacrylate resin and less on the polymerization mechanism itself, i.e., whether it is a self-cured or dually cured dental cement. Thus, in clinical practice, cementitious materials with a higher proportion of TEGDMA compared with BisGMA are recommended.

Measurement of the accuracy of dental working casts using a coordinate measuring machine.

Background/Aim: Dental impressions present a negative imprint of intraoral tissues of a patient which is, by pouring in gypsum, transferred extraorally on the working cast. Casting an accurate and precise working cast presents the first and very important step, since each of the following stages contributes to the overall error of the production process, which can lead to inadequately fitting dental restorations. The aim of this study was to promote and test a new model and technique for in vitro evaluation of the dental impression accuracy, as well as to asses the dimensional stability of impression material depending on the material bulk, and its effect on the accuracy of working casts. Methods: Impressions were made by the monophasic technique using the experimental master model. Custom trays with spacing of 1, 2 and 3 mm were constructed by rapid prototyping. The overall of 10 impressions were made with each custom tray. Working casts were made with gypsum type IV. Measurement of working casts was done 24 h later using a co-ordinate measuring machine. Results: The obtained results show that the working casts of all the three custom trays were in most cases significantly different in the transversal and sagittal planes in relation to the master model. The height of abutments was mainly unaffected. The degree of convergence showed certain significance in all the three custom trays, most pronounced in the tray with 3 mm spacing. Conclusion: The impression material bulk of 1­3 mm could provide accurate working casts when using the monophasic impression technique. The increase of the distance between abutment teeth influences the accuracy of working casts depending on the material bulk. [Projekat Ministarstva nauke Republike Srbije, br. TR 35020: Research and development of modelling methods and approaches in manufacturing of dental recoveries with the application of modern technologies and computer aided systems]

Application of modern computer-aided technologies in the production of individual bone graft: A case report.

INTRODUCTION: An autologous bone (bone derived from the patient himself) is considered to be a "golden standard" in the treatment of bone defects and partial atrophic alveolar ridge. However, large defects and bone losses are difficult to restore in this manner, because extraction of large amounts of autologous tissue can cause donor-site problems. Alternatively, data from computed tomographic (CT) scan can be used to shape a precise 3D homologous bone block using a computer-aided design-computer-aided manufacturing (CAD-CAM) system. CASE REPORT: A 63-year old male patient referred to the Clinic of Dentistry of Vojvodina in Novi Sad, because of teeth loss in the right lateral region of the lower jaw. Clinical examination revealed a pronounced resorption of the residual ridge of the lower jaw in the aforementioned region, both horizontal and vertical. After clinical examination, the patient was referred for 3D cone beam (CB)CT scan that enables visualization of bony structures and accurate measurement of dimensions of the residual alveolar ridge. Considering the large extent of bone resorption, the required ridge augmentation was more than 3 mm in height and 2 mm in width along the length of some 2 cm, thus the use of granular material was excluded. After consulting prosthodontists and engineers from the Faculty of Technical Sciences in Novi Sad we decided to fabricate an individual (custom) bovine-derived bone graft designed according to the obtained-3D CBCT scan. CONCLUSION: Application of 3D CBCT images, computer-aided systems and software in manufacturing custom bone grafts represents the most recent method of guided bone regeneration. This method substantially reduces time of recovery and carries minimum risk of postoperative complications, yet the results fully satisfy the requirements of both the patient and the therapist.

Application of fibrin rich blocks with concentrated growth factors in pre-implant augmentation procedures.

INTRODUCTION: Growth factors are mediators regulating the key processes of tissue regeneration, including cell proliferation and differentiation, extracellular matrix synthesis, chemotaxis and angiogenesis. In addition to the role they play in haemostasis and inflammatory processes, thrombocytes are of major importance in the reparation of mineralized and soft tissues. Application of fibrin rich blocks with concentrated growth factors is one of the latest approaches to guided bone regeneration and augmentation of lost bony structures of the alveolar ridge. CASE REPORT: This paper presents a case of a female patient who underwent reconstruction of the defect of residual alveolar ridge of the upper jaw by applying fibrin rich blocks with concentrated growth factors and subsequent placement of two titanium endosteal implants five months after wound healing. CONCLUSION: The loss of a single tooth or several teeth sometimes entails the augmentation of lost bony structures in order to provide optimal conditions for dental implant placement and subsequent prosthetic rehabilitation. A range of contemporary surgical procedures and a variety of dental materials for reconstruction of bony defects of the upper and lower jaws are available nowadays. The method described in this paper, i.e. the application of concentrated growth factors is one of the latest approaches which poses no risk of transmissible and allergic diseases and is at the same time cost effective.

A Comparative Analysis of the Corrosive Effect of Artificial Saliva of Variable pH on DMLS and Cast Co-Cr-Mo Dental Alloy.

Dental alloys for direct metal laser sintering (DMLS) are available on the market today, but there is little scientific evidence reported on their characteristics. One of them is the release of ions, as an indicator of the corrosion characteristics of a dental alloy. Within this research, the difference in the elution of metals from DMLS and cast (CM) samples of Co-Cr-Mo dental alloy in saliva-like medium of three different pH was examined by inductively-coupled plasma mass spectrometry (ICP-MS). The obtained results show that the metal elution in artificial saliva from the DMLS alloy was lower than the elution from the CM alloy. The release of all investigated metal ions was influenced by the acidity, both from the DMLS and CM alloy, throughout the investigated period of 30 days. The change in acidity from a pH of 6.8 to a pH of 2.3 for the cast alloy led to a higher increase of the elution of Co, Cr and Mo from CM than from the DMLS alloy. The greatest release out of Co, Cr and Mo was for Co for both tested alloys. Further, the greatest release of all ions was measured at pH 2.3. In saliva of pH 2.3 and pH 4.5, the longer the investigated period, the higher the difference between the total metal ion release from the CM and DMLS alloys. Both alloys showed a safe level of elution according to the ISO definition in all investigated acidic environments.

[Three dimensional mathematical model of tooth for finite element analysis].

INTRODUCTION: The mathematical model of the abutment tooth is the starting point of the finite element analysis of stress and deformation of dental structures. The simplest and easiest way is to form a model according to the literature data of dimensions and morphological characteristics of teeth. Our method is based on forming 3D models using standard geometrical forms (objects) in programmes for solid modeling. OBJECTIVE: Forming the mathematical model of abutment of the second upper premolar for finite element analysis of stress and deformation of dental structures. METHODS: The abutment tooth has a form of a complex geometric object. It is suitable for modeling in programs for solid modeling SolidWorks. After analysing the literature data about the morphological characteristics of teeth, we started the modeling dividing the tooth (complex geometric body) into simple geometric bodies (cylinder, cone, pyramid,...). Connecting simple geometric bodies together or substricting bodies from the basic body, we formed complex geometric body, tooth. The model is then transferred into Abaqus, a computational programme for finite element analysis. Transferring the data was done by standard file format for transferring 3D models ACIS SAT. RESULTS: Using the programme for solid modeling SolidWorks, we developed three models of abutment of the second maxillary premolar: the model of the intact abutment, the model of the endodontically treated tooth with two remaining cavity walls and the model of the endodontically treated tooth with two remaining walls and inserted post. CONCLUSION: Mathematical models of the abutment made according to the literature data are very similar with the real abutment and the simplifications are minimal. These models enable calculations of stress and deformation of the dental structures. The finite element analysis provides useful information in understanding biomechanical problems and gives guidance for clinical research.