A comparison of stress relaxation in temporary and permanent luting cements

PurposeThe stress relaxation and compressive strength of resin, resin-modified glass ionomer, glass ionomer, polycarboxylate, and zinc oxide eugenol cements were measured to determine the characteristics of these materials after setting.MethodsA total of 19 luting cements including 12 permanent cements and 7 temporary cements were used. Cylindrical cement specimens (10 mm long and 6 mm in diameter) were obtained by chemical setting or light curing. The specimens were stored for 24–36 h in water at 37 °C and were then used for the stress relaxation and compression tests. The stress relaxation test was carried out using three constant cross-head speeds of 5, 50, and 100 mm/min. Upon reaching the preset dislocation of 0.5 mm, the cross-head movement was stopped, and the load was recorded for 60 s. Fractional stress loss at 1 s was calculated from the relaxation curves. The compressive strength and modulus were measured at a cross-head speed of 1 mm/min. Data were analyzed with the Kruskal–Wallis test and Holm's test.ResultsA zinc oxide eugenol cement [TempBOND NX] exhibited the largest fractional stress loss. A resin cement [ResiCem] showed the largest compressive strength, while a glass ionomer cement [HY-BOND GLASIONOMER CX] showed the largest compressive modulus among all tested cements (p < 0.05).ConclusionThe fractional stress loss could not be classified by the cement type. Two implant cements [Multilink Implant and IP Temp Cement] showed similar properties with permanent resin cements and temporary glass ionomer cements, respectively. Careful consideration of the choice of cement is necessary.     

ASO Visual Abstract: Influence of Damaged Stomach on Anastomotic Leakage After Cervical Esophagogastrostomy for Patients with Esophageal Cancer

Annals of Surgical Oncology -     

Congenital radio-ulnar synostosis

Thirty-three patients with congenital radio-ulnar synostosis were examined. There was one familial predisposition. Chromosomal patterns were examined in seventeen patients and were normal. Bone maturation appeared normal. The radial deviation angle, in the patients whose distal radial epiphysis had closed, was elevated (Madelung's deformity). However, in the patients whose distal epiphysis maturation score was 8, it was not elevated. On the other hand, elongation of the ulna (plus variant) and/or dorsal dislocation of the distal end of the ulna was seen in early life. In terms of treatment, all attempts to divide the two bones failed. It was found that derotation of the nonwriting hand by an osteotomy through the proximal fusion mass was a useful procedure.     

Down's syndrome and esophageal achalasia: a rare but important clinical entity

We report a case of esophageal achalasia (EA) in Downȁ9s syndrome. A six-year-old girl with DS was referred from another hospital for further management of dysphagia and growth retardation (weight 16.3 kg, height 105.4 cm: both below −1.5 SD). Dysphagia commenced when she was one year old and gastroesophageal reflux (GER) was diagnosed when she was four. Routine investigations suggested EA or esophageal stenosis secondary to GER. While dissecting the esophago-gastric junction in preparation for a Heller-Dor esophagocardiomyotomy (HD-ECM), the crus of the diaphragm was noted to be narrowed, severely fibrosed and attached to the lower esophagus which was covered by dense scar tissue suggestive of an old esophageal perforation secondary to GER esophagitis. A Nissen fundoplication was performed, but dysphagia persisted postoperatively, and a narrowing 2 cm above the fundoplication wrap with proximal dilatation was found on repeated barium studies. At re-laparotomy, the fundoplication was unwrapped and HD-ECM performed. Eight months postoperatively, she is well with no recurrence. EA must be considered in any DS patient presenting with dysphagia.     

Involvement of reticular neurons located dorsal to the facial nucleus in activation of the jaw-closing muscle in rats

The location of excitatory premotor neurons for jaw-closing motoneurons was examined by the use of electrical and chemical stimulation and extracellular single-unit recording techniques in the anesthetized rat. Single-pulse electrical stimulation of the supratrigeminal region (SupV) and the reticular formation dorsal to the facial nucleus (RdVII) elicited masseter EMG response at mean (+/-SD) latencies of 2.22 +/- 0.59 ms and 3.10 +/- 1.14 ms, respectively. Microinjection (0.1-0.3 microl) of glutamate (50 mM) or kainate (0.5-100 microM) into RdVII increased masseter nerve activity in artificially ventilated and immobilized rats by 30.2 +/- 40.5% and 50.7 +/- 46.8% compared to baseline values, respectively. Forty reticular neurons were antidromically activated by stimulation of the ipsilateral trigeminal motor nucleus (MoV). Twenty neurons were found in RdVII, and the remaining 20 neurons were located in SupV, or areas adjacent to SupV or RdVII. Eleven neurons in RdVII responded to at least either passive jaw opening or light pressure applied to the teeth or tongue. Nine neurons responded to passive jaw opening. Five of the nine neurons responded to multiple stimulus categories. A monosynaptic excitatory projection from one neuron in RdVII was detected by spike-triggered averaging of the rectified masseter nerve activity. We suggest that reticular neurons in RdVII are involved in increasing masseter muscle activity and that excitatory premotor neurons for masseter motoneurons are likely located in this area. RdVII could be an important candidate for controlling activity of jaw-closing muscles via peripheral inputs.     

Endothelin-1-induced impairment of endothelium-dependent relaxation in aortas isolated from controls and diabetic rats

An accumulating body of evidence indicates that an increased endothelin-1 level is related to endothelial dysfunction in cardiovascular diseases. In this study, we tested whether prolonged treatment of aortas with endothelin-1 induces endothelial dysfunction. When isolated aortas from control rats were cultured with endothelin-1, at levels above the plasma concentration, the acetylcholine-induced endothelium-dependent relaxation was significantly decreased (as compared with endothelin-1-nontreatment). This endothelin-1-induced endothelial dysfunction was more marked in aortas obtained from rats with streptozotocin-induced diabetes than in those from the controls. The endothelin-1- induced attenuation was very strongly suppressed by co-incubation with J-104132, endothelin receptor A/B antagonist, or polyethylene-glycolated superoxide dismutase, a cell-permeant superoxide anion scavenger or LY294002, phosphoinositide 3-kinase inhibitor. These results indicate that endothelin-1 can induce endothelial dysfunction, and that this may be related to superoxide generation and to PI3-kinase activity.     

Relaxation modulus of denture base resin reinforced with woven glass fibers

This study examined the reinforcing effect of woven glass fibers on the relaxation modulus by three-point loading of denture base resin. Three sandwich-type flexure test specimens polymerized by heating were used, all 3 mm thick: glass fibers in compression (U type); glass fibers in the center (C type); and glass fibers in tension (L type). Unreinforced specimens (ACR) were produced as a control. The relaxation modulus after 8 sec from the start of stress (Er(8)) was calculated from stress relaxation curves. In the glassy state, the Er(8)s of the U and L types were greater than those of the ACR and C types. In the rubbery state (plateau region), the Er(8)s of the U and L types were greater than those of the ACR and C types. The woven glass fibers added to the U and L type specimens increased the relaxation modulus of PMMA near the oral temperature; moreover, they inhibited stress relaxation when the temperature increased.     

Mechanical properties of light-cured composite resins cured through filters that simulate enamel

The light-attenuating effects of enamel on the mechanical properties of light-cured composite resins were evaluated using simple experimental filters. Three filters were designed to simulate the light transmittance characteristics of 0.5, 1.0, and 1.5 mm thick human enamel. The Knoop hardness numbers (KHN) and the elastic modulus in transverse tests for twelve shades of three light-cured composite resins were examined. These resins were cured either using direct irradiation with a light source, or indirect irradiation through one of the filters. The attenuations of light by 0.5, 1.0, and 1.5 mm thick enamel filter were 45%, 67% and 81% in the 430 nm-550 nm wavelength region, respectively. For all materials, KHN and the elastic modulus of specimens irradiated through filters were significantly lower than those irradiated directly. The results suggest that the light-attenuating effect of enamel reduces the mechanical properties of light-cured resin, and may cause poor clinical longevity of restorations.     

Coeruleotrigeminal suppression of nociceptive sensorimotor function during inflammation in the craniofacial region of the rat

Descending action from the locus coeruleus (LC) on the trigeminal sensorimotor function was evaluated in a rat model of oral-facial inflammation. For the induction of oral-facial inflammation, mustard oil (20% solution in 20microl mineral oil) was injected into the region of the temporomandibular joint (TMJ). One week before testing, rats received bilateral lesions of the LC using a cathodal current. The electromyogram (EMG) threshold, which is the threshold intensity for the onset of EMG activity of the masseter muscle evoked by pressure on the TMJ region, was used in the present study as an indicator of the trigeminal sensorimotor function. Following mustard oil injection, in the LC-lesioned rats, EMG thresholds significantly decreased at 30min, which lasted up to 240min. In contrast, EMG thresholds in the LC-intact rats returned to the level before injection after 180min. Systemic naloxone (1.3mg/kg, i.v.) produced a further decrease of EMG thresholds in both the LC-intact and LC-lesioned rats. Under the existence of naloxone, EMG thresholds in the LC-lesioned rats were significantly lower than those of the LC-intact rats. These results suggest that oral-facial inflammation activates the coeruleotrigeminal modulating system and that an action of this system is independent of the opioid depressive mechanism.