Magnetic resonance elastography with guided pressure waves

Magnetic resonance elastography aims to non-invasively and remotely characterize the mechanical properties of living tissues. To quantitatively and regionally map the shear viscoelastic moduli in vivo, the technique must achieve proper mechanical excitation throughout the targeted tissues. Although it is straightforward, ante manibus, in close organs such as the liver or the breast, which practitioners clinically palpate already, it is somewhat fortunately highly challenging to trick the natural protective barriers of remote organs such as the brain. So far, mechanical waves have been induced in the latter by shaking the surrounding cranial bones. Here, the skull was circumvented by guiding pressure waves inside the subject's buccal cavity so mechanical waves could propagate from within through the brainstem up to the brain. Repeatable, reproducible and robust displacement fields were recorded in phantoms and in vivo by magnetic resonance elastography with guided pressure waves such that quantitative mechanical outcomes were extracted in the human brain.     

Correlates of Concurrent Khat and Tobacco Use in Yemen

Background: Habitual substance use poses public health threat. This is a growing concern in countries where one or more substances are commonly used. Many individuals in Middle Eastern and East African countries use khat (Catha edulis), a stimulant often accompanied by smoking. However, few systematic attempts have been made to characterize patterns of concurrent khat and tobacco use. Objectives: To examine correlates such as gender and patterns of khat and tobacco use in concurrent users and khat-only users. Methods: This study used a cross-sectional design with a face-to-face interview method including 151 (74 women) concurrent users of khat and tobacco and 141 (76 women) khat-only users in Yemen. Data collection was completed in 2012. Analysis of variance (ANOVA) and logistic regressions were conducted to examine gender and khat use group differences in use patterns. Results: Reported frequency and intensity of khat use were greater in men than in women. Men and women khat users used different tobacco products and beverages while using khat. Khat use was more frequent in concurrent users relative to khat-only users. Earlier age of onset of khat use was associated with greater number of cigarettes smoked during a typical khat session. Approximately 70% of concurrent users reported initiating khat use prior to tobacco use. Conclusions/Importance: The results provide support for gender differences in khat and tobacco use, differences in khat use pattern between concurrent users of khat and tobacco and khat-only users, and positive associations between khat and tobacco use.     

Fracture resistance and failure patterns of endodontically treated mandibular molars restored using resin composite with or without translucent glass fiber posts

The elastic modulus of the restorative material is important in restoring endodontically treated teeth. This study aimed to compare the fracture resistance and failure patterns of 90 mandibular molars restored using resin composites with or without fiber posts, with respect to the number of residual cavity walls. Five restoration types were performed corresponding to different wall defects (groups 1-5). Groups were divided in two subgroups corresponding to the use or absence of fiber posts. Teeth were loaded and resistance of specimens was measured as the axial compressive load to cause fracture and macroscopic fracture patterns were observed. One way ANOVA revealed a significant difference in fracture resistance (p < 0.001). Tukey post hoc test also revealed significant differences between groups as samples restored with fiber posts exhibited mostly restorable fractures. It was concluded that the resistance of endodontically treated mandibular molars restored with composite resins is mainly affected by the number of residual walls. Using fiber-reinforced posts optimized fracture patterns.     

Periodontal health and its relationship with salivary factors among different age groups in a Saudi population

PURPOSE: This study aimed to describe the periodontal condition of children, adolescents and young Saudi adults and to investigate its relationship with salivary variables and oral hygiene status. MATERIALS AND METHODS: A sample of 114 children, 99 adolescents and 99 young adults were randomly selected from patients attending dental clinics at the school of dentistry. Clinical examination of oral health status included using WHO Community Periodontal Index and Green and Vermillion oral hygiene index. In addition, salivary flow rate, pH, buffering capacity and microbial flora were measured. RESULTS: A healthy periodontal condition was found in 6.7% of the sample. Calculus was the most frequently encountered periodontal disease. Children had better periodontal condition than adolescents and adults. Males had higher plaque and gingival scores than females. The salivary flow rate and pH were significantly higher in individuals with good periodontal condition. The salivary level of fluoride and buffering capacity was not related to the periodontal condition. Yeast was the only microorganism related to periodontal condition. The relationship between poor periodontal condition and high plaque score was highly significant. CONCLUSIONS: Periodontal disease increased with age and was strongly related to salivary flow rate, pH value and yeast level, as well as plaque accumulation. Preventive efforts must be increased in order to achieve the WHO goal for the year 2010 of no more than one sextant showing bleeding or calculus at the age of 15.     

A clinical and radiographic evaluation of stainless steel crowns for primary molars

AIM: This study was performed to evaluate clinically and radiographically the effect of stainless steel crowns placed on primary molars on gingival and bone structures. SAMPLE: 254 crowns were evaluated in a sample of 177 children aged 3.5-12 years old with a mean age of 7 years. METHOD: The clinical parameters that were evaluated were, crown marginal extension, crown marginal adaptation, intact proximal contact, gingival index and the duration of presence of the crowns, together with the oral hygiene index of the child. Bitewing radiographs were viewed for extension and adaptation of crown margins and for evaluating the interproximal bone level. RESULTS: The results of the study showed that interproximal bone resorption was not significantly affected by either crown marginal extension or adaptation, preserving tight proximal contact between molars, oral hygiene level or duration of presence of the crown. On the other hand, there was significant bone resorption when the crown was judged radiographically as non-satisfactory. While oral hygiene level had a significant effect on the gingival index, presence or absence of proper proximal contact did not have an effect on the gingival index. CONCLUSION: It was concluded from this study that stainless steel crowns are still a valuable procedure that has no harmful effect on the gingiva and bone provided that good oral hygiene level was maintained.