Methods of Processing Dental Chromium-Cobalt Alloys for Production of Metal Frameworks Faced with Ceramics to Obtain the Best Mechanical Properties.

BACKGROUND Modern prosthetic technologies make it possible to fabricate prosthetic restorations without material loss and to make prosthetic restorations with complex geometric shapes in a relatively simple way. One such technology is selective laser melting (SLM), or additive manufacturing of metal materials, better known as 3D printing from metal or selective laser melting, but currently the most commonly used method is casting. The present study investigated use of dental chromium-cobalt alloys for prosthetic bridges and compared methods of processing dental chromium-cobalt alloys to obtain the best mechanical properties. MATERIAL AND METHODS We used dental chromium-cobalt alloy (SCHEFTNER GMBH) for laser melting StarbondCoSEeasy Powder with grain size of 10-30 µm and StarbondCoS alloy casting, made in accordance with the European standard EN ISO 22674. SLM-made specimens and induction melted alloy castings were prepared for the study. A centrifugal casting system with induction current melting of the metal alloy was used to produce the samples. The melting and casting process is automatic and limits changes in chemical composition. RESULTS The results show that none of the samples changed their chemical composition, while the samples made by SLM had better mechanical properties. CONCLUSIONS The SLM technique makes it possible to produce restorations faster and cheaper without any loss of quality compared to restorations made with the casting technique. Casting technology reduces mechanical properties, but still provides good mechanical properties.

Standardization of the ultrasound examination of the masseter muscle with size-independent calculation of records.

BACKGROUND: As ultrasonography provides objective parameters and values, it is a reliable method of examining the structure and dimensions of the masseter muscle. Although the method is well known, there is no standardization in clinical examination and data analysis yet. OBJECTIVES: The study aimed to measure masseter muscle thickness in designated areas to establish the most repeatable and clinically applicable method of ultrasound examination, and to assess differences in measurements in designated areas for clinical purposes by devising the size-independent parameter. The size-independent parameter may potentially be more clinically applicable than distance records, which are affected by the size of the subject. MATERIAL AND METHODS: An ultrasound examination of 124 masseter muscles was performed. Axial examination in 3 horizontal regions (lower, middle and upper) and coronal examination in 2 vertical regions (proximal and distal) was carried out. Masseter muscle thickness was measured in every designated area when relaxed (muscle at rest (RMT)) and with clenched teeth (contracted muscle (CMT)). A morphological independent functional index of thickness difference (FITD) was calculated. RESULTS: The study revealed very high statistical differences between RMT and CMT (p < 0.0001) in all designated areas but with location variations. Masseter muscle thickness significantly differed depending on the examined area and transducer projection. CONCLUSIONS: The ultrasound study showed that masseter muscle thickness significantly differs depending on the examined area. The authors emphasize the necessity to examine the masseter muscle in specified areas with both coronal and axial projections to achieve objective and repeatable examination. Notable clinical value is assigned to FITD, which is independent from the morphological dimensions of the muscle.

Ultrasonography in the Diagnosis of Temporomandibular Disorders: A Meta-Analysis.

BACKGROUND The increased prevalence of temporomandibular disorders (TMDs) requires searching for new, easily accessible diagnostic methods. In addition to routine clinical examination, various methods of imaging temporomandibular joints are available, such as magnetic resonance imaging, computed tomography scans, or scintigraphy. Ultrasound imaging, due to short examination time, low cost, and non-invasiveness, should be recommended as a routine diagnostic procedure. The aim of the study was to investigate whether ultrasound imaging can be used in the diagnosis of temporomandibular joint disorders. MATERIAL AND METHODS Publications during the period 2006 to March 2017 from the US National Library of Medicine database were selected for analysis by entering the terms "ultrasonography", "ultrasound", "USG", "temporomandibular joint", "TMJ", "temporomandibular disorders", and "TMD". Papers were chosen if they met the required criteria relating to the sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of this diagnostic technique with regard to imaging articular disc displacement, joint effusion, and condylar abnormalities. RESULTS The search yielded 1883 publications, of which 8 were selected that met the criteria for inclusion in the analysis. For articular disc displacement examinations, the following results were obtained: sensitivity 75.6%; specificity 69.1%; accuracy 76.1%; positive predictive value 72.2%; negative predictive value 65.6%. When the examinations of joint effusion and condylar abnormalities were included, the results were respectively 66.9%; 70.8%; 69.9%; 75.8%; and 62.4%. CONCLUSIONS The use of ultrasonography in the diagnosis of temporomandibular disorders requires standardizing the method as well as further research to confirm its effectiveness.

Incidence of Otologic Symptoms and Evaluation of the Organ of Hearing in Patients with Temporomandibular Disorders (TDM).

BACKGROUND Numerous studies have discussed cases of concomitant temporomandibular disorders (TMD) and otologic symptoms (OS). However, attempts to determine the true origin of these symptoms combined with assessments of the condition of the organ of hearing are relatively rare. This study aimed to evaluate the frequency and type of OS in patients with TMD, and attempted to determine the origin of the OS in the studied group of patients. MATERIAL AND METHODS 246 patients, aged 40.08±11.12 years (F=147, M=99) with TMD, from the Department of Oral Rehabilitation of Poznan University of Medical Sciences. METHODS: dental history interviews and clinical examinations. There were 2 groups-G1 and G2-selected on the basis of the presence or absence of OS in the medical history stage. After audiological evaluation, 2 subgroups were identified: G1.1 and G1.2. RESULTS OS were observed in 36.18% (G1). In 48 patients (53.93%), the audiological evaluation found there was no impairment of the organ of hearing (G1.2). Audiological abnormalities were found in 46.07% (n=41) of the patients (G1.1). The OS which differentiated the 2 groups were a plugging sensation as well as otalgia (more frequent in group G1.2) and hearing impairment (more frequent in group G1.1). CONCLUSIONS 1. The OS which most frequently accompany with TMD were fullness and otalgia. 2. It is recommended that a subjective assessment of hearing loss in patients with TMD and concomitant OS should be included in the medical history stage. 3. Clicking and popping are significantly more frequent in patients without concomitant hearing impairment.