The manuscript aimed to review the types of acrylate polymers used in dentistry, as well as their chemical, physical, mechanical, and biological properties. Regarding their consistency and purpose, dental acrylate polymers are divided into hard (brittle), which includes acrylates for the production of plate denture bases, obturator prostheses, epitheses and maxillofacial prostheses, their repairs and lining, and soft (flexible), which are used for lining denture bases in special indications. Concerning the composition and method of polymerization initiation, polymers for the production of denture bases are divided into four types: heat-, cold-, light-, and microwave-polymerized. CAD/CAM acrylate dentures are made from factory blocks of dental acrylates and show optimal mechanical and physical properties, undoubtedly better monomer polymerization and thus biocompatibility, and stability of the shape and colour of the base and dentures. Regardless of the number of advantages that these polymers have to offer, they also exhibit certain disadvantages. Technological development enables the enhancement of all acrylate properties to respond better to the demands of the profession. Special attention should be paid to improving the biological characteristics of acrylate polymers, due to reported adverse reactions of patients and dental staff to potentially toxic substances released during their preparation and use.

Background: Rotary endodontic instruments are increasingly used in root canal treatment and have replaced stainless steel manual files. Cyclic fatigue is the cyclic loading of stress to produce deformation or fracture. This study aimed to evaluate and compare the effects of autoclave sterilization on cyclic fatigue in 5 types of rotary endodontic instruments. Material/Methods: ProTaper Universal, BioRace, ProTaper Next, Twisted File, and HyFlex CM instruments were included in this study. Each type included 96 instruments, divided into 4 groups according to the number of sterilization cycles (0, 1, 3, 5). After sterilization, each group of instruments was divided into 2 subgroups and tested for cyclic fatigue in 2 simulated canals (45 degrees both and 2 radii, 2 mm and 5 mm). The number of cycles to failure (NCF) was calculated, and statistical analyses were carried out using the t test, Mann-Whitney U test, and ANOVA, followed by the Tukey post hoc test (p<0.05). Fracture surfaces were analyzed using scanning electron microscopy (SEM). Results: Within the group of non-sterilized instruments, ProTaper Universal showed significantly lower resistance to cyclic fatigue compared to the other types of instruments (p<0.001). After repeated sterilization, a significantly higher mean of NCF was observed for BioRace (p<0.001), ProTaper Next (p<0.001), Twisted File (p<0.001), and HyFlex CM (p<0.001) compared to ProTaper Universal. The resistance of HyFlex CM was significantly higher compared to the other types of instruments (p<0.001). Conclusions: The findings from this study showed that autoclave sterilization of newer rotary endodontic instruments could increase resistance to cyclic fatigue.

Morphological and anatomical characteristics of the tooth are of great importance for clinical dentistry. These aspects of the tooth can be better conceptualized from the perspective of external and internal morphology of dental crowns and roots. The aim of this study was to determine the average total length of the upper first and second premolars, the average length of crowns, the average length of roots and to determine the most common number of the roots and root canals of these teeth. We used 41 first and 48 second extracted upper premolars.The length of these teeth was measured by a digital micrometer. The number of roots was determined visually, and each tooth was longitudinally dissected across the vestibular-palatal plane for determining the number of root canals. The average total length of the upper first premolars was 22.5 mm, the average crown length was 8.8 mm, the mean root length was 13.7 mm. The upper first premolars usually have two roots in 53.7% and two root canals in 82.9%. The average total length of the upper second premolars was 22.5 mm. The average crown length was 8.4 mm and the mean root length was 14.1 mm. The upper second premolars usually have one root in 89.6% and one root canal in 79.2%. The determined average values of the length of these teeth and the length of their crowns and roots were similar to the values of the same population reported by other authors.

Beer, red and white wine are acidic drinks whose frequent consumption can increase the risk of dental erosion. To establish the effect of beer, red and white wine on the morphology and surface roughness (SR) of human enamel using different exposure times in a cyclic deand remineralization model in vitro. The experiment included 33 surgically extracted impacted human third molars from patients aged 18-25 years. Enamel samples obtained by cutting crowns (n = 132) were submitted to alternate cycles of demineralization in (1) beer, (2) red wine, (3) white wine, (PC) positive control (orange juice), and remineralization in artificial saliva, which also represented a medium for negative control (NC). The experiment included cycles with different exposure times in alcoholic beverages and orange juice of 15, 30 and 60 min. Thus, 12 groups were formed (for each drink and each exposure time) containing 10 samples each, while the NC group consisted of 12 samples. Experiments were repeated 3x/day for 10 days. Enamel surface alterations were determined by stylus profilometry (average surface roughness (Ra)) and scanning electron microscopy (SEM). The Shapiro-Wilk test, independent samples Kruskal-Wallis test and multiple comparisons (all pairwise) were performed. With increasing exposure time, there was a positive correlation with Ra for white wineand orange juice-immersed samples (60 min compared to 15 min), which was also observed using SEM. There was no significant difference in the Ra between the other experimental samples for the same exposure time. This study confirms a certain erosive potential of beer, red and white wine, and a significant relationship with pH, titratable acidity (TA) and SR, but not with the exposure time for all tested alcoholic beverages. Moreover, differences among the ultrastructural patterns caused by alcoholic beverages over the enamel surface were observed.

Effects of Herpesviruses on Proinflammatory Cytokines in Chronic Periapical Lesions - Article abstract #946843

Cemento-enamel junction (CEJ) is an important anatomical structure of the tooth, which is located in the cervical part of the tooth between the crown and root, or at the contact point between the enamel which overlaps the tooth crown and cementum overlapping the root dentin. There are four possible relationships between two tissues that make the CEJ such as: the cement overlaps the enamel; the enamel overlaps the cement; the enamel and cement abut each other with no overlap; the enamel and cement are not in contact. The aim of this study was to determine the relationship between the enamel and cement which make the CEJ in different types of permanent teeth. The material consisted of 30 permanent teeth with intact CEJ. Staining of CEJ was carried out using the methylene blue. After staining, the tooth was washed under the running water and drying at room temperature. Each tooth was longitudinally cut in the vestibular-oral direction. Observation of CEJ was done with Leica light microscope and images were obtained using a Nikon camera. The results indicated that the most common form of CEJ between the cement and enamel in the region of CEJ was that cement and enamel abutted without overlap (36.7%), followed by the cement overlapping the enamel (33.3%), and the cases when a gap between the cement and enamel (16.7%) was present, and when the enamel overlaped the cement (13.3%). Because of the morphological diversity of CEJ, careful performing of dental interventions in the region of tooth neck is necessary because they may change the morphology of this region, induce the pathological processes and hypersensitivity of teeth.