Mechanical properties and radiopacity of experimental glass-silica-metal hybrid composites.

OBJECTIVES: Experimental glass-silica-metal hybrid composites (polycomposites) were developed and tested mechanically and radiographically in this fundamental pilot study. To determine whether mechanical properties of a glass-silica filled two-paste dental composite based on a Bis-GMA/polyglycol dimethacrylate blend could be improved through the incorporation of titanium (Ti) particles (particle size ranging from 1 to 3 microm) or silver-tin-copper (Ag-Sn-Cu) particles (particle size ranging from 1 to 50 microm) we measured the diametral tensile strength, fracture toughness and radiopacity of five composites.METHODS: The five materials were: I, the original unmodified composite (control group); II, as group I but containing 5% (wt/wt) of Ti particles; III, as group II but with Ti particles treated with 4-methacryloyloxyethyl trimellitate anhydride (4-META) to promote Ti-resin bonding; IV, as group I but containing 5% (wt/wt) of Ag-Sn-Cu particles; and V, as group IV but with the metal particles treated with 4-META. Ten specimens of each group were tested in a standard diametral tensile strength test and a fracture toughness test using a single-edge notched sample design and five specimens of each group were tested using a radiopacity test.RESULTS: The diametral tensile strength increased statistically significantly after incorporation of Ti treated with 4-META, as tested by ANOVA (P=0.004) and Fisher's LSD test. A statistically significant increase of fracture toughness was observed between the control group and groups II, III and V as tested by ANOVA (P=0.003) and Fisher's LSD test. All other groups showed no statistically significant increase in diametral tensile strength and fracture toughness respectively when compared to their control groups. No statistically significant increase in radiopacity was found between the control group and the Ti filled composite, whereas a statistically significant increase in radiopacity was found between the control group and the Ag-Sn-Cu filled composite as tested by ANOVA (P=0.000) and Fisher's LSD procedure.SIGNIFICANCE: The introduction of titanium and silver-tin-copper fillers has potential as added components in composites to provide increased mechanical strength and radiopacity, for example for use in core materials.     

An investigation of some food-approved polymers as agents to inhibit hydroxyapatite dissolution

Dental erosion involves dissolution of the hydroxyapatite fraction of enamel and dentine, so agents that reduce the dissolution rate of hydroxyapatite could find application in food products aimed at reducing erosion. This study was performed to test some common food ingredients and additives for their effect on the dissolution rate of hydroxyapatite in a citric acid solution representative of soft drinks. Pyrophosphate, tripolyphosphate and a linear chain polyphosphate (average 25 phosphate units) significantly reduced the hydroxyapatite dissolution rate by 35, 46 and 64%, respectively. Xanthan gum and carboxymethylcellulose significantly reduced the hydroxyapatite dissolution rate by 29 and 16%, respectively. The protective effect may be ascribed to the binding of condensed phosphate or to the formation of an adsorbed layer of gum at the hydroxyapatite surface. Several other common food additives had no statistically significant effect on the hydroxyapatite dissolution rate. Polyphosphate exhibited a considerable persistence of action, causing a reduction in the dissolution rate for 3 h after treatment. Tripolyphosphate was slightly persistent, and pyrophosphate and xanthan gum did not exhibit a substantial persistence of action. A solution containing polyphosphate and xanthan gum reduced the hydroxyapatite dissolution rate by 70% and exhibited a similar persistence of action to the solution containing only polyphosphate. These compounds are suggested to have potential as erosion-reducing agents in soft drinks.     

Use of near infrared spectroscopy to detect impaired tissue oxygen saturation in patients with complex regional pain syndrome type 1

Purpose

Deep tissue hypoxia has been hypothesized in the pathogenesis of complex regional pain syndrome type 1 (CRPS 1) for some patients. The purpose of this study was to determine if near-infrared spectroscopy (NIRS) could detect differences in deep tissue oxygen saturation (StO₂) and microcirculatory function in the hands of patients with CRPS 1.

Methods

Tissue oxygen saturation was evaluated at baseline and during an ischemia reperfusion challenge using vascular occlusion testing (VOT) in affected vs unaffected hands of patients with unilateral upper limb CRPS 1. A non-randomized experimental study design was used with baseline StO₂ as the primary outcome measure. Secondary outcome measures were occlusion and reperfusion slopes from VOT. Values were compared with the unaffected, contralateral hand and with the dominant and non-dominant hands of sex and age-matched volunteers. Correlations between values derived from NIRS and measures of pain and function from the Brief Pain Inventory (BPI) and the Disability of the Arm, Shoulder and Hand (DASH) questionnaires were explored.

Results

Independent of handedness, the baseline StO₂ of the affected hands of ten CRPS 1 patients was significantly lower than that of their unaffected hands (?5.8%; 95% confidence interval [CI] ?10.6 to ?1.0; P = 0.02). The baseline StO₂ of affected CRPS 1 hands was also significantly lower than the non-dominant hands of ten volunteers (?7.3%; 95% CI ?12.4 to ?2.3; P = 0.007). Differences in VOT occlusion and reperfusion slopes did not reveal changes that could be uniquely attributed to CRPS 1. No significant correlations were detected between values derived from VOT and values for pain and function obtained from BPI and DASH questionnaires for patients with CRPS 1.

Conclusions

Hands of patients affected by CRPS 1 of the upper limb showed significantly lower StO₂ compared with their unaffected contralateral hand as well as the hands of control subjects. This trial was registered at: ClinicalTrials.gov: NCT01586377.     

Usability testing of multimodal feedback interface and simulated collision-avoidance power wheelchair for long-term-care home residents with cognitive impairments

Many older adults in long-term-care homes have complex physical and cognitive impairments and have difficulty propelling manual wheelchairs. Power wheelchair use is restricted owing to safety concerns. Power wheelchairs with collision-avoidance features are being developed to enable safe and independent mobility; however, a paucity of information exists on interface features to help users navigate away from obstacles. We developed a system combining an interface with auditory, visual, and haptic feedback and a simulated collision-avoidance power wheelchair. This device allowed the investigator to stop movement of the power wheelchair when users approached obstacles and to deliver feedback to help them navigate. Five long-term-care home residents with mild or moderate cognitive impairments evaluated device usability, which included effectiveness, efficiency, and user satisfaction. Each resident used the device for six 1 h sessions. Observations, feedback interviews, and outcome questionnaires were completed during and after the sessions. We found the device effective in enabling residents to achieve basic driving tasks and self-identified indoor mobility goals. Furthermore, residents perceived workload to be low and were satisfied with the device. Residents also felt that the feedback was useful to help them navigate away from obstacles.     

Short-Term Natural Course of Depressive Symptoms and Family-Related Stress in Adolescents After Separation From Father

Objective:

To determine if separation from a father is associated with short-term changes in mental health or substance use in adolescents.

Methods:

Every 3 months, during a 5-year period, we followed 1160 Grade 7 students participating in the Nicotine Dependence in Teens Study who were living with both parents. Participants who reported not living with their father for 6 or more consecutive months during follow-up were categorized as separated from father. Pooled regressions within the framework of generalized estimating equations were used to model the associations between separation from father and indicators of mental health (depressive symptoms, and worry and [or] stress about family relationships or the family situation) and substance use (alcohol use and cigarette smoking) 4 to 6 and 7 to 9 months postseparation, controlling for age, sex, and baseline level of the outcome variable.

Results:

Compared with adolescents living with both parents, adolescent offspring separated from their fathers were more likely to report depressive symptoms (β = 0.17, 95% CI 0.01 to 0.33) 4 to 6 months postseparation, as well as worry and (or) stress about their parents separating or divorcing (OR 2.39, 95% CI 1.29 to 4.43), a new family (OR 4.25, 95% CI 2.33 to 7.76), and the family financial situation (OR 2.35, 95% CI 1.53 to 3.60). Separation from father was also marginally significantly related to worry and (or) stress about their relationship with their father (OR 1.53; 95% CI 0.98 to 2.39). At 7 to 9 months postseparation, separation from father continued to be associated with worry and (or) stress about their parents separating or divorcing, a new family, and the family financial situation. Separation from father was no longer associated with worry and (or) stress about their relationship with their father, but it was associated with worry and (or) stress about their relationship with their mother. Separation from father was not related to use of alcohol or cigarettes.

Conclusion:

Adolescent offspring experienced family-related stress and transient depression symptoms in the 4- to 9-month period following separation from their fathers.     

Functional tricuspid regurgitation secondary to aortic annular abscess: An unusual presentation of infective endocarditis

An unusual case of aortic annular abscess is presented, in which the patient presented with features of gross tricuspid regurgitation. There was no direct involvement of the tricuspid valve. Tricuspid regurgitation disappeared following surgical repair of the annular abscess. The present case also illustrates the utility of trans-oesophageal echocardiography in establishing the diagnosis and planning surgical intervention.