The effect of thermocycling on the degree of conversion and mechanical properties of a microhybrid dental resin composite

OBJECTIVE: The purpose of this study was to investigate the degree of conversion (DC) and mechanical properties of a microhybrid Filtek Z250 (3M ESPE) resin composite after aging. METHOD: The specimens were fabricated using circular molds to investigate Vickers microhardness (Vickers hardness number [VHN]) and DC, and were prepared according to ISO 4049 for flexural strength testing. The initial DC (%) of discs was recorded using attenuated total reflectance-Fourier transforming infrared spectroscopy. The initial VHN of the specimens was measured using a microhardness tester under a load of 300 g for 15 seconds and the flexural strength test was carried out with a universal testing machine (crosshead speed, 0.5 mm/min). The specimens were then subjected to thermocycling in 5°C and 55°C water baths. Properties were assessed after 1,000–10,000 cycles of thermocycling. The surfaces were evaluated using scanning electron microscopy (SEM). Data were analyzed using 1-way analysis of variance followed by the Tukey honest significant difference post hoc test. RESULTS: Statistical analysis showed that DC tended to increase up to 4,000 cycles, with no significant changes. VHN and flexural strength values significantly decreased upon thermal cycling when compared to baseline (p < 0.05). However, there was no significant difference between initial and post-thermocycling VHN results at 1,000 cycles. SEM images after aging showed deteriorative changes in the resin composite surfaces. CONCLUSIONS: The Z250 microhybrid resin composite showed reduced surface microhardness and flexural strength and increased DC after thermocycling.

Effect of back belt on maximum displacement and center of pressure velocity in different lifting styles

Purpose: Mechanical loading is said to be an important factor in the development of low back pain [LBP]. One of the main concerns in manual material handling [MMH] tasks is lifting loads, as this activity is present in most jobs. Despite the controversy about their effectiveness, belts are used in industry as either protective or assistive devices in manual load handling. The present investigation aimed to determine whether a commonly used back belt could improve maximum center of pressure displacement [COPMD] and center of pressure velocity [COPV] as the balance parameters during each of three common styles of lifting [squat, semi-squat, stoop]

Methods: Twenty healthy female subjects participated in this study who were selected by non-probability convenience sampling. The participants stood barefoot on the force plate. They lifted a box, weighting 4.53 kg [10 pound]. The subjects were instructed to bend their knees [squat] or their lumbar [stoop] or both their knees and lumbar [semi-squat], to grasp the box handles, and to lift the load to the level of greater trochanter height. Half of the subjects performed the 3 trials with wearing belt at first try and the other half performed the trials without wearing the belt at first try

Results: The mean of maximum displacement and velocity showed that there was a trend of increase in these variables in all 3 styles of lifting [squat, semi-squat and stoop] after wearing belt. One-way ANOVA with repeated measures results for COPMD and COPV showed that 'Belt condition' significantly affected the dependent variables

Conclusion: Wearing belt may decrease stability caused by increased COPMD and COPV

[Comparison effect of artificial tooth type and cyclic loading on the bond strength to auto-polymerized acrylic denture base resins]

Failure of bonding between artificial teeth and denture base material is a considerable problem for patients who wear dentures. According to the different impact of artificial teeth and different information about resistance force of mastication and also with deficiency in researchs, this study was designed to compare the bond strength of composite and acrylic artificial teeth to auto-polymerized denture base resins with and without cyclic loading. In this experimental and in vitro study, an acrylic resin auto-polymerized [Rapid Repair, Dentsply] and four artificial teeth [Acrylic Marjan new, Composite Glamour teeth and Ivoclar acrylic and composite teeth] were used. Therefore, 8 groups of 10 specimens each were evaluated. All specimens were thermocycled for 5000 cycles, in water baths between 5 and 55[degree]C. Half the specimens in each group were treated with cyclic loading at 50N for 14, 400 cycles at 1.2 Hz. The shear bond strengths were measured using a Universal Testing Machine. Data were analyzed using Two-way ANOVA test. Statistical analysis demonstrated no significant effect of cyclic loading on the shear bond strength, but the type of artificial tooth affected the shear bond strength [P=0.006]. Also, the interaction between Cyclic loading and the type of artificial tooth showed no significant difference [P=0.98]. Tukey test showed that acrylic teeth [Ivoclar] had statistically higher bond strength values than that of other teeth [P[Glamour]=0.02], [P[Composite ivoclar]=0.01] and [P[Marjan new]=0.02]. Within the limitation of this study, the predominant type of fracture in all groups was cohesive, therefore the bond strength was adequate in all teeth and the type of artificial tooth may influence the bond strength of denture teeth to denture base resin. Cyclic loading had no significant effect on the bond strength of denture teeth to the auto-polymerized acrylic resin.

effects of wrist orthosis on Hmax to Mmax ratio, spasticity, Grip and pinch strength and wrist and elbow range of motion of spastic children

Upper limb dysfunction is a common and disabling consequence of cerebral palsy. Instrumental evaluations, based on electromyography or biomechanical techniques, may objectively quantify various clinical characteristics associated with spasticity and should be considered as an adjunct to clinical evaluation. The purpose of this study was to determine the effects of wrist orthosis on Hmax to Mmax ratio, spasticity, Grip and pinch strength and wrist and elbow range of motion of 7 to 12 years old spastic children. The design of this study was clinical trial and before after. Twenty four 7 to 12 spastic cerebral palsy children that have the inclusion criteria of study were selected from rehabilitation clinics of Tehran. The patients used a wrist orthosis [10 degree of wrist extension, full extension of fingers and abduction and opposition of thumb] for 2 mounts [2 hours during day and 4 to 6 hours at night]. In this study the H-reflex was recorded using an electromyography, by an experienced physiotherapist who was blind to the clinical examination results. Spasticity of the upper limb was clinically assessed using the Modified Ashworth Scale. MIE used to evaluate Grip and Pinch strength and Goniometric measurements of elbow and wrist extension were obtained in degrees to calculate the passive range of motion. The results of this study showed significant reduction in Hmax to Mmax ratio [P 0/002], wrist spasticity and elbow spasticity [P 0/001] and significant increase in Grip [P 0/002] and Pinch [P 0/001] strength and wrist range of motion [P 0/003]. The data did not show any significance in elbow range of motion [P 0/328]. Our findings suggested that 2 months using of wrist orthosis in children with spastic cerebral palsy can reduce Hmax to Mmax ratio and wrist spasticity and increase Grip and Pinch strength and wrist range of motion

Quality of life among coal miners

Health statues of workers is affected by work situation and kind of job severely very often. Meanwhile working in mines is one of health threatening occupations. This study was carried out to assess quality of life [QOL] among Shahrood coal miners in Iran. This was a descriptive-cross sectional study of quality of life among 99 workers from one of the Shahrood coal mines. Quality of life was measured by the Short Form [SF-36]. Data were analysed using tests Mann Whitney and Kruskal Wallis. The mean of age and duration of work of subjects were 36.5 +/- 6.8 and 10.9 +/- 6.4 years, respectively. The lowest and highest quality of life scores found for general health perceptions 10/2 +/- 14 and mental health 61/5 +/- 24/6. In addition, positive significant associations were found between education level, age and work duration and mean of quality of life scores. Coal miners had worse QOL score in all domains than Iranian healthy community. To improve the QOL of coal miners, control harmful factors, promote safety and health according to international standards of work environment, periodic medical examination and precise evaluation of workers health status are suggested

Effects of dorsal static splint on spasticity and range of motion of upper extremity of children with cerebral palsy in three time periods

Cerebral Palsy [CP] is a neurodevelopmental disorder caused by non-progressive lesions in single or multiple locations in the immature brain. Lesions of motor cortex and pyramidal tracts can lead to spasticity. Inhibition of spasticity is necessary to increase extremity mobilization, prevent postural abnormalities and provide independence in daily living activities. The purpose of this study was to determine the effects of volar static splint spasticity and range of motion of upper extremity in children with Cerebral palsy in three periods of time. The design of this study was experimental and repeated measurements. Ten children with Cerebral palsy aging 4-6 years old were non-randomly selected among children referred to occupational therapy Clinic of rehabilitation Faculty of Tehran University of Medical Sciences. Children used dorsal static splint for three months [2 hours at day and 4 hours at night]. In this study, Modified Ashworth Scale was used to evaluate spasticity and a Goniometre was used to measure passive range of motion. The results of this study showed significant reduction in the upper limb spasticity after 2 months [p

[ investigation on a new vacuum-based knee brace to produce patellofemoral joint distraction: a preliminary study]

Patellar bracing is a common component of treatment in patellofemoral pain syndrome [PFPS]. Most of the currently used braces act based on re-aligning the patella; however, a new brace was designed by the researchers, which acts via external vacuum system. This preliminary study aimed to determine whether the new vacuum brace is able to pull up the patella into the vacuumic cup and create a suitable patello-femoral joint distraction. Seventeen knees from ten patients with PFPS were undertaken for the computerized tomography scan study at 0° and 30° knee flexion immediately before and after the bracing. The outcome measurements included the patello-femoral joint area [PFJA], and the average patellofemoral joint space width [APFJSW]. The results of this study demonstrated a significant increase in PFJA and APFJSW parameters following the vacuum bracing [P<0.001] at both knee angles. The results showed that applying a vacuum brace can create an appropriate patellofemoral joint distraction

Effects of volar static splint on function and spasticity of upper extremity of hemiplegic adults

Stroke, despite recent advances in medical technology is a problem of public health systems. Stroke is a neurological dysfunction by vascular origin and its signs and symptoms corresponding to the damaged areas of the brain. Prevalence of spasticity after stroke has been reported in 39% of patients. The upper limb of 50% of patients with stroke remains without function due to spasticity. The purpose of this study was to determine the effects of volar static splint on function and spasticity of upper extremity in hemiplegic adults. The design of this study was experimental and repeated measurement. Fifteen patients with stroke aging 41-85 years old of both sexes were no randomly selected from rehabilitation clinics and hospitals of Tehran. The patients used a volar static splint [10 degree of wrist extension, full extension of fingers and abduction and opposition of thumb] two mounts [2 hours at day and 4 hours at night]. In this study Modified Ashworth Scale was used to evaluate spasticity. A Goniometre was used to measure passive range of motion. Upper extremity function was evaluated by Fugl-Meyer Test. The results of this study showed significant reduction in wrist and elbow spasticity [p<0.0001], significant increase in wrist and elbow passive range of motion [p<0.0001 and p<0.002, respectively] and upper limb function [p<0.0001]. This study shows that 2 months using of volar static splint in patients with chronic stroke has significant effects on reduction of wrist and elbow spasticity, increasing passive range of motion of these joints and upper limb function. It seems that application of this splint is useful for improvement of upper limb function in chronic hstroke patients

[Effect of vestibulo-proprioceptive stimulations in a child with agenesis of the corpus callosum]

The purpose of the present study was to investigate the effect of vestibulo-properioceptive stimulations of sensory integration theory on the development of gross and fine motor, language and personal-social functions in a child with agenesis of the corpus callosum. We report a 10.5 month old boy with agenesis of the corpus callosum. The intervention was administered based on sensory integration theory an hour a week for 10 weeks. The exercise intervention consisted of proprioceptive and linear, sustained and low frequency vestibular stimulations on suspension device and physio roll. A Denver Developmental Screening- II and milestones skill testing was completed pre-intervention and monthly. Post-intervention, age of gross motor, fine motor adaptive, language, and personal-social functions significantly improved. Based on milestones skills, maintenance of gross motor functions [e.eg. sitting and quadruped position] improved. The child could roll from side to side and released objects voluntarily. The reaction time to auditory stimulations became less than 2 seconds. Vestibulo-proprioceptive stimulations using the neuroplasticity ability of the central nervous system is effective for development of gross and fine motor, language, and personal-social functions. These exercises can be administered for a child with agenesis of the corpus callosum