Assessment of compression and strength of divergent screws mounted on miniplates and dynamic compression plate in fixation of mandibular body fractures: an in vitro study.

Achieving compression in the fracture line gap by open reduction and internal fixation leads to more primary bone healing and therefore hastens the healing process and patient's rehabilitation. We aimed to evaluate the application of compression by a modification in screw insertion in miniplates to improve the efficiency of the previous relevant methods. In this in vitro experimental study 20 sheep hemimandibles were prepared. Following intentional fracturing of the hemimandibular bodies, the specimens were divided into two: the control and study groups (n=10 each). The control group was fixed with straight four-hole dynamic compression plate (DCP) without a bar and with parallel screws. The study group was fixed with a straight four-hole miniplate without a bar. Screws were divergently inserted into the bone with an angle of 45°. The differences in the fracture line gap were measured before and after fixation considering the indicators of compression. The strength of the fixation was also assessed with a universal testing machine. The control group provided more compression than the study group (p=0.4). There was no difference in the strength of fixation between the two groups. It is concluded that the application of the miniplates with divergent screws instead of DCP could encompass the advantages of both perspectives such as intraoral incisions and compressive force and prevent the disadvantages of compression plates such as hard adaptation.

Effect of fixation method on intergonial width stability after mandibular setback via bilateral sagittal split osteotomy.

Q4: Horizontal changes occur following bilateral sagittal split osteotomy (BSSO) in skeletal class III patients. The aim of this study was to assess the ostoperative changes in intergonial (IG) width and compare them between the positional screw and miniplate fixation methods in BSSO. This study evaluated patients who had mandibular prognathism and underwent BSSO for mandibular setback. Internal fixation was performed bilaterally, either with positional screws in the lateral ramus or with a miniplate. Postero-anterior cephalograms were obtained preoperatively (T1), at 1 month postoperative (T2), and at 6 months postoperative (T3). The IG widths and the alterations in IG width postoperative (T2-T1, T3-T2) were measured. No correlations were observed between the amount of setback and changes at T2 -T1 or T3-T2. The IG width values decreased after mandibular setback and internal fixation with both methods. Statistical analyses showed a significant difference between T3 and T1 in the miniplate group (P=0.045). No significant difference in the postoperative change in IG width (T2-T1 and T3-T2) was found between the two fixation groups. The magnitude of this change was smaller for positional screws when compared to miniplates for fixation. The amount of mandibular setback showed no correlation with postoperative changes in IG width..

Effects of black seed (Nigella sativa), ginger (Zingiber officinale) and cone flower (Echinacea angustifolia) on the immune system of rainbow trout, Oncorhynchus mykiss / Efeitos de semente preta (Nigella sativa), gengibre (Zingiber officinale) e Flor-de-cone (Echinacea angustifolia) no sistema imunológico de truta arco-íris, Oncorhynchus mykiss

This study was carried out to evaluate the effects of dietary essential oils of ginger (Zingiber officinale), black seed (Nigella sativa) and cone flower (Echinacea angustifolia) on the immune system of cultured rainbow trout, Oncorhynchus mykiss. A total of 360 fish were divided into 4 groups and 3 replicates each containing 30 fish. The fish were fed for 21 days with 1% of the herbal essential oils and with unsupplemented diet as the control group. Haematological and immune parameters including serum lysozyme, number of phagocytic bacteria, Hb, PCV, MCV, MCH, MCHC, number of RBC and WBC were studied. Treatments recorded enhancement in immune parameters compared to the control group. Significantly higher serum lysozyme level and phagocytic germs were detected in the groups fed black seed, ginger and cone flower (P<0.05). However, no significant difference was found in RBC, Hb, PCV, MCV, MCH and MCHC of fish fed the diets containing essential oils and the control group (P>0.05). The results of this study demonstrated that essential oils might strengthen the non-specific immunity of rainbow trout.(AU)

Avaliou-se a eficácia de uma dieta com semente preta (Nigella sativa), gengibre (Zingiber officinale) e Flor-de-cone (Echinacea angustifolia) sobre o sistema imunológico de truta arco-íris (Oncorhynchus mykiss) em cultivo. Um total de 360 peixes foram divididos em 4 grupos com 3 repetições cada, contendo 30 peixes. Os peixes foram alimentados por 21 dias com 1% de óleo essencial herbáceo e com dieta comercial não suplementada como controle. Parâmetros imunes e hematológicos incluindo soro lisozima, número de bactéria fagocítica, Hb, PCV, MCV, MCH, MCHC, número de RBC e WBC foram estudados. Os tratamentos registraram a melhoria em parâmetros imunes comparados ao grupo de controle. Foram detectadas concentrações de lisozima no soro e germes fagocíticos significativamente altos em grupos que receberam semente preta, gengibre e Flor-de-cone (P<0.05). Porém, não foi encontrada diferença significativa em RBC, Hb, PCV, MCV, MCH e MCHC nos peixes alimentados com dietas contendo óleos essenciais e no grupo de controle (P>0.05). Os resultados deste estudo demonstraram que óleos essenciais podem aumentar a imunidade não específica da truta arco-íris.(AU)

Assessment of compression and strength of divergent screws mounted on miniplates for fixation of mandibular fractures: an in vitro experimental study.

An efficient band of tension is critical for the adequate fixation of mandibular fractures, so fixation devices that compress are helpful. We aimed to evaluate the possibility of creating compression using screws inserted divergently into miniplates placed in the tension zone of mandibular fractures and record the effects on the strength of fixation. For this in vitro experimental study we prepared 20 sheep hemimandibles. After angle fractures had been created, the specimens were divided into standard and study groups (n=10 in each). In the standard group the tension zones were fixed in the standard manner with 4-hole miniplates and 4 parallel screws. Those in the study group were fixed as for the standard group but with 4×45° divergent screws. The differences in the gap in the fracture line before and after fixation were measured as indicators of compression. The strength of fixation was also assessed with a universal testing machine in vitro. The amount of compression was significant only in the study group (p<0.001), and there was no difference in the strength of fixation between the two groups (p=0.7). We conclude that divergent drilling and insertion of screws creates more horizontal force when miniplates are used, and results in reduction in the size of the probable gap in the fracture line. Insertion of divergent screws in miniplates may create compression between fractured segments without jeopardising the strength of fixation.

Cognitive impairments and neuronal injury in different brain regions of a genetic rat model of absence epilepsy.

Growing numbers of evidence indicate that cognitive impairments are part of clinical profile of childhood absence epilepsy. Little is known on neuropathological changes accompanied by cognitive deficits in absence epilepsy. The aim of the present study was to investigate age-dependent neuropathological changes accompanied by learning and memory impairments in Wistar Albino Glaxo from Rijswijk (WAG/Rij) rat model of absence epilepsy. Experimental groups were divided into four groups of six rats of both WAG/Rij and Wistar strains with 2 and 6 months of age. The learning and memory performances were assessed using passive avoidance paradigm and neuropathological alterations were investigated by the evaluation of the number of dark neurons and apoptotic cells as well as the expression of caspase-3 in the neocortex, the hippocampus, and different regions of the thalamus. Results revealed a decline in learning and spatial memory of 6-month-old WAG/Rij rats compared to age-matched Wistar rats as well as 2-month-old WAG/Rij and Wistar rats. The mean number of dark neurons was significantly higher in the hippocampal CA1 and CA3 areas as well as in the laterodorsal, centromedial, and reticular thalamic nuclei and the somatosensory cortex of 6-month-old WAG/Rij rats. In addition, a higher number of apoptotic cells as well as a higher expression of caspase-3 was observed in the hippocampal CA1 and CA3 regions, the laterodorsal thalamic nucleus, and the somatosensory cortex of 6-month-old WAG/Rij rats compared to other animal groups. These results indicate significant enhancement of neuronal damage and cell death accompanied by memory deficits after seizure attacks in a rat model of absence epilepsy. Seizure-induced neuronal injury and death may underlie cognitive impairments in absence epilepsy.

Reasons for extraction of permanent teeth in general dental practices in Tehran, Iran.

OBJECTIVES: The aim of this survey was to investigate the primary reason for extraction of permanent teeth, its correlations with age, gender and education level, as well as identify the important predictors for dental caries in general dental centers in Tehran, Iran. SUBJECTS AND METHODS: The study was conducted over a period of 6 months; its population consisted of 1,382 patients, aged 9-95 years, who underwent tooth extraction. There were 673 (47.8%) male and 709 (51.3%) female patients. The frequency distribution was calculated using the χ(2) test, ANOVA and t test for differences in mean number of extracted teeth and the logistic regression model to evaluate the variables associated with reasons for tooth extraction. RESULTS: A total of 2,620 teeth were extracted from the 1,382 patients. The highest rate (36.9%) of extraction occurred for those 41-60 years old. Males comprised 48.7% of patients but had more teeth (1,470, 55.3%) extracted than females (1,150, 43.9%). Nine hundred and thirty-six (67.7%) patients had incomplete secondary education or less. Tooth loss due to caries was 51%; periodontal disease was 14.4%; supernumerary and tooth impaction 13.9%. There was a significant association between patient characteristics (age, gender and education level) and number of teeth extracted. CONCLUSION: Dental caries and periodontal disease were the main reasons for tooth extraction in Tehran, Iran.

The effect of repetitive spreading depression on neuronal damage in juvenile rat brain.

Spreading depression (SD) is pronounced depolarization of neurons and glia that travels slowly across brain tissue followed by massive redistribution of ions between intra- and extracellular compartments. There is a relationship between SD and some neurological disorders. In the present study the effects of repetitive SD on neuronal damage in cortical and subcortical regions of juvenile rat brain were investigated. The animals were anesthetized and the electrodes as well as cannula were implanted over the brain. SD-like event was induced by KCl injection. The brains were removed after 2 or 4 weeks after induction of 2 or 4 SD-like waves (with interval of 1 week), respectively. Normal saline was injected instead of KCl in sham group. For stereological study, paraffin-embedded brains were cut in 5 microm sections. The sections were stained with Toluidine Blue to measure the volume-weighted mean volume of normal neurons and the numerical density of dark neurons. The volume-weighted mean volume of normal neurons in the granular layer of the dentate gyrus and layer V of the temporal cortex in SD group were significantly decreased after four repetitive SD. Furthermore, densities of dark neurons in the granular layer of the dentate gyrus (after 2 weeks), the caudate-putamen, and layer V of the temporal cortex (after 4 weeks) were significantly increased in SD group. Repetitive cortical SD in juvenile rats may cause neuronal damage in cortical and subcortical areas of the brain. This may important in pathophysiology of SD-related neurological disorders.

Study motives and career choices of Iranian dental students.

OBJECTIVES: To investigate the study motives and career choices of Iranian senior dental students in relation to their background factors. SUBJECTS AND METHODS: During the spring term 2005, a questionnaire survey was administered to 327 senior dental students in seven randomly selected state dental schools in Iran. The questionnaire requested information on age, gender, parents' employment in dentistry, previous education and employment in dental hygiene, study motives, and career choices. Statistical analyses were made using independent sample t test, factor analysis, and binary logistic regression model. RESULTS: Based on the factor analysis, which explained 73% of the total variance, five motive dimensions were identified: altruism and intellectual challenges, characteristics of the profession, social status and security, other person's recommendation, and failure to be admitted to other study programmes. The mean for the 'characteristics of the profession' dimension was lower among the students with at least one parent employed in dentistry (p = 0.03). The 'altruism and intellectual challenges' dimension was reported to be more influential by the students with background in dental hygiene (32 students) compared to the others (p < 0.001). Engaging in postgraduate studies was the first career preference of 189 (70%) of the respondents. Those with a background in dental hygiene were less inclined to enter postgraduate courses (p < 0.001), but more eager to be employed in either the public or the private sector (p < 0.001), and to enter the community oral health and research field (p < 0.001) than the others. CONCLUSION: Personal characteristics and motives of the students play a major role in shaping their career preferences.

Kinetic interpretation of a negative time constant impedance of glucose electrooxidation.

Nickel-copper alloy modified glassy carbon electrodes (GC/NiCu) prepared by galvanostatic deposition were used for the electrocatalytic oxidation of glucose in alkaline solutions. The electro-oxidation of glucose in a 1 M NaOH solution at different concentration of glucose was studied by the method of ac-impedance spectroscopy. The impedance behavior show different patterns, capacitive, and inductive loops and negative resistances, at different applied anodic potential. The influence of the electrode potential on the impedance pattern is studied and a quantitative explanation for the impedance behavior of glucose oxidation is put forward by a proposed mathematical model. At potentials higher than 0.5 V/Ag-AgCl, a pseudoinductive behavior is observed while at higher than 0.53 V/Ag-AgCl, impedance pattern is reversed to the second, third, and forth quadrants. The conditions required for the reversing of impedance pattern are delineated with the use of the impedance model. The previously proposed electrooxidation mechanism for glucose on GC/NiCu electrode was found to reproduce the experimental impedance plots.