Secondary dentin formation mechanism: The effect of attrition

Human dentin consists of a primary layer produced during tooth formation in early child-hood and a second layer which first forms upon tooth eruption and continues throughout life, termed secondary dentin (SD). The effect of attrition on SD formation was considered to be confined to the area subjacent to attrition facets. However, due to a lack of three‐dimensional methodologies to demonstrate the structure of the SD, this association could not be determined. Therefore, in the current study, we aimed to explore the thickening pattern of the SD in relation to the amount of occlusal and interproximal attrition. A total of 30 premolars (50–60 years of age) with varying attrition rates were evaluated using micro‐computerized tomography. The results revealed thickening of the SD below the cementoenamel junction (CEJ), mostly in the mesial and distal aspects of the root (p < 0.05). The pattern of thickening under the tooth cervix, rather than in proximity to attrition facets, was consistent regardless of the attrition level. The amount of SD thickening mildly corre-lated with occlusal attrition (r = 0.577, p < 0.05) and not with interproximal attrition. The thickening of the SD below the CEJ coincided with previous finite element models, suggesting that this area is mostly subjected to stress due to occlusal loadings. Therefore, we suggest that the SD formation might serve as a compensatory mechanism aimed to strengthen tooth structure against deflection caused by mechanical loading. Our study suggests that occlusal forces may play a significant role in SD formation

Health Care Service of Dental Specialists in Lithuania

Darbo tikslas – įvertinti, kokia dalis odontologų specialistų teikia nespecializuotas odontologinės sveikatos priežiūros paslaugas, nustatyti teikiamų paslaugų ir demografinių bei profesinių požymių ryšį. Visiems Lietuvoje praktikuojantiems gydytojams odontologams specialistams (N = 551) išsiųsta anketa. Gauti 345 atsakymai, kas sudarė 62,6% tyrimo atsako dažnį. 41,8% visų odontologų specialistų Lietuvoje teikia ne tik specializuotas odontologinės sveikatos priežiūros paslaugas, bet dirba ir kaip odontologai. Tikimybė, kad odontologinės sveikatos priežiūros klinikų vadovai ar patalpų nuomininkai dirbs ir kaip odontologai specialistai ir odontologai 2,49 karto didesnė lyginant su samdomais odontologais specialistais. Ryšys tarp odontologų specialistų teikiamų paslaugų ir amžiaus, specializacijos įgijimo būdo bei jaučiamo pacientų trūkumo nenustatytas. Dalis odontologų specialistų baigė studijas valstybės lėšomis, todėl situacija parodo neracionalų podiplominėms studijoms (rezidentų ruošimui) skiriamų valstybės lėšų panaudojimą.The aim of the present study was to explore the health care service of dental specialists in Lithuania, to investigate the relation between the service and dental specialists‘ demographic and professional factors. Census sampling was employed (n=551) and the data collected by means of a structured questionnaire. Response rate was 62.6%. 58.2% of all dental specialists provided only specialized care, while the rest 41.8% worked as a specialist and also as a general dentist. Possibility of providing only specialized care was 2.49 times higher for private practice owners or those who rented dental chair for dental practice when compared to associate dentists. No significant difference between the dentist’ age, organizational type of residency studies, perceived lack of patients and provided service was found. As part of dental specialists‘ postgraduate (residency) studies was government funded, the situation leads to an inefficient use of state finance and need to be addressed by policy makers and health care planners in Lithuania

Lactulose Biosynthesis with Enzymes of Lactose-Fermenting Micromycetes and Bacteria

Lactulose is a well-studied prebiotic popular in medicine and the food industry. β-Galactosidases offer an alternative to traditional chemical methods of lactulose production. The article describes lactulose biosynthesis with crude enzyme preparations of β-galactosidases obtained by separate and joint cultivation of lactose-fermenting yeasts and lactic acid bacteria in whey permeate. The research featured the following producers of β-galactosidases: lactose-fermenting yeasts of Kluyveromyces lactis VKM Y-1333 and Y-1339, Kluyveromyces marxianus VKM Y-459 and Y-1338, and viscous strains of lactic acid bacteria of Lactobacillus acidophilus and Streptococcus thermophilis. The β-galactosidase activity was measured using the method of o-nitrophenyl-β-D-galactopyranoside hydrolysis. The method of high-performance liquid chromatography made it possible to reveal the carbohydrate composition. The lactulose formation by yeast enzymes demonstrated the following pattern: its concentration increased rapidly during the first 30 min of reaction with subsequent decrease or stabilization. Some combined unpurified enzyme preparations of yeasts and lactic acid microorganisms were more active than β-galactosidases obtained by separate cultivation. The patterns of lactulose formation depended on both the yeast strain and the type of lactic acid bacteria. The highest yields of lactulose belonged to the samples that combined β-galactosidases of all yeast strains with Streptococcus thermophilis. Co-cultivation of yeast and lactic acid bacteria in some combinations produced combined crude enzyme preparations with higher activity and greater lactulose yields than separate yeast cultivation. These results can help to obtain purified enzyme preparations of β-galactosidases and lactulose-containing products from secondary dairy raw materials