Wear and mechanical properties of composite resins consisting of different filler particles.

To investigate the effects of different fillers and their contents on the wear of composite resins, four composites (CS: non-porous spherical silica, AS: porous spherical silica, AZ: porous spherical zirconium silicate, and IS: non-porous irregular-shaped silica) were experimentally prepared using different fillers (CS, AZ, AS and IS). Simulated occlusal wear and toothbrush wear were evaluated for these composites and their worn surfaces were observed. The mechanical properties (flexural strength, elastic modulus and hardness) of these composites were determined to examine the relationships between wear and these mechanical properties. CS showed the highest occlusal wear, but the lowest toothbrush wear among four composites. AS and AZ had lower occlusal wear than CS and IS, while their toothbrush wear was higher than CS and close to that of IS. All composites showed increase in the occlusal wear as filler content increased. CS and IS showed decrease in the toothbrush wear as the filler content increased, whereas AS and AZ did not. The occlusal wear surfaces of CS and IS had concavities, while those of AZ and AS were relatively smooth with flattened filler. The toothbrush wear surfaces of CS and IS revealed the extrusion of filler from resin matrix, whereas those of AZ and AS were smooth with flattened filler. The toothbrush wear of CS and IS decreased as the mechanical properties increased, whereas those of AS and AZ did not. The occlusal wear of all composites increased as the mechanical properties increased, which would not reflect effects of these mechanical properties.

The use of complementary and alternative medicine by pediatric food-allergic patients in Japan.

BACKGROUND: In developed countries, increasing food allergy prevalence and concern regarding food allergies have been reported. Although the use of complementary and alternative medicine (CAM) for the treatment of allergic diseases has increased in some Western countries, the actual proportion and patterns of CAM use for pediatric food allergies in Japan are still unknown. METHODS: Fourteen allergy centers in Japan participated in the study using a questionnaire survey regarding the use of CAM by pediatric patients. A diagnosis of food allergy was made at each hospital by pediatric allergists. RESULTS: Surveys were completed by parents/guardians, and data were collected for a total of 962 pediatric food-allergic patients. Overall, 8.4% of the participants used CAM to treat a food allergy. The major CAM therapies used were herbal teas (22.2%), including several Japanese herbal teas, Chinese herbal medicine (18.5%) and lactic acid bacteria (16%). Among the participants using CAM to treat food allergy, 13.6% thought that the CAM being used was very effective, while 11.1% of participants thought that CAM caused some type of side effect. CONCLUSIONS: Our study is the first large-scale national survey regarding the use of CAM in pediatric patients with food allergies in Japan. Unlike in the USA, which has a higher rate of CAM use (17%), approximately 8.4% of food-allergic patients used CAM in Japan. Interestingly, the major types of CAM used in Japan differed from those used in the USA. Cultural differences and food customs may affect the use of CAM.

Casting of MOD inlay using rings with holes on both sides: 12∼18 wt%Au-20∼26Pd-14.48∼26.48Cu-40Ag-1.5Zn-0.02Ir alloys.

Using a casting ring with openings on both sides and a water-absorbent polymer, heterogeneity is maintained in a single casting and a precise MOD inlay can be produced. We produced 9 different kinds of gold-silver-palladium (Au-Ag-Pd) alloys by changing the ratio of palladium, gold, and copper and investing them, and changing parameters such as the angulation of the casting ring openings and the water:powder ratios to produce MOD inlay castings. We measured the expansion and shrinkage percentage of the castings in both the buccolingual and mesiodistal directions. From this experiment, we learned that precise MOD inlay castings can be produced using rings with 240° openings when invested in a thick mix having a standard water:powder ratio or using rings with 200° openings when invested in a thick mix having a water:powder ratio for a 12 wt%Au-20∼26Pd-20.48∼26.48Cu-40Ag-1.5Zn-0.02Ir alloyes.

[Fatal esophageal hemorrhage in patients with severe motor and intellectual disabilities complicated with severe scoliosis, during catheter placement in esophagus].

In patients with severe motor and intellectual disabilities (SMID), fatal esophageal hemorrhage including penetration of the descending aorta, has often been reported. We experienced 2 patients with severe scoliosis who developed esophageal hemorrhage during catheter placement in the esophagus. We compared chest CT images of these cases with those of 38 SMID patients in our hospital. As a result, a few patients showed esophagus bending to the left of the descending aorta while the vertebral body curved to the right and the mediastinum shifted to the left. It is suggested that there is a risk of esophageal hemorrhage caused by catheter stimulation, when a catheter is placed in the esophagus in such patients. It is therefore necessary to use the thinnest and softest catheter possible and to consider the indications for gastrostomy.

Effect of particle diameter on air polishing of dentin surfaces.

We examined the abrasiveness of glycine powders with particle diameters of 63 and 100 mum by measuring the depth and volume of defects produced during air polishing of human dentin. A total of 36 extracted human teeth were embedded in acrylic resin. The resin blocks were polished until the dentin surfaces were exposed. The nozzle of an air polisher was mounted 4 mm from the dentin surface, and the dentin surface was treated for 5 s at one of two angles of incidence (45 degrees or 90 degrees). Three materials were used in the polishing process: NaHCO(3) powder with a mean particle diameter of 100 microm (Handy Jet Powder), glycine powder with a mean particle diameter of 63 microm (Handy Jet Powder PMTC), and glycine powder with a mean particle diameter of 100 microm (Handy Jet Powder Recall). The defect depth at both angles was significantly deeper after treatment with Handy Jet Powder or Handy Jet Powder PMTC. The defect volume was the greatest with Handy Jet Powder, followed by Handy Jet Powder PMTC, and Handy Jet Powder Recall. The larger diameter glycine powder resulted in less damage to the dentin.

Effects of abrasive and fiber components in medium on wear of composite resins.

Effects of abrasive and fiber components in a medium on the wear behavior of composite resins were evaluated. Calcium diphosphate and methyl cellulose were included in the medium as abrasive and fiber components respectively. A range of 0, 4, or 8% abrasive- or fiber-containing media were applied on a composite resin specimen during a simulated occlusal wear test. Four composite resins, Clearfil AP-X, Z100 Restorative, SOLARE P, and SOLIDEX F, were tested to evaluate the effects of these components in the medium. Presence of abrasive material in the medium increased the wear of composite resins significantly, but its effect differed among the composite resins. Presence of fiber material in the medium significantly decreased the wear of two composite resins, whereas the other two composites showed no significant differences. Nonetheless, presence of fiber in the medium generally tended to prevent the wear of composite resins.

Effects of occlusal and brushing cycles on wear of composite resins in combined wear test.

The effects of occlusal cycles and brushing cycles on wear of composite resins were investigated using a combined wear test, which carried out occlusal and toothbrush wear tests alternately. Worn volume and maximum worn depth were measured to evaluate wear under four combinations of two different cycles (occlusal cycles: 50 and 150 cycles; brushing cycles: 20 and 50 cycles). With composite resin APX, which consisted of relatively large and irregular-shaped filler particles, its worn volume and worn depth significantly increased with the number of occlusal cycles. With composite resin Z100, which consisted of relatively small and irregular-shaped filler particles, its wear values significantly increased with both brushing and occlusal cycles. With composite resin SRE, which consisted of small, irregular-shaped, inorganic filler particles and large organic filler particles, its worn volume significantly increased with the occlusal cycle when under a lower brushing cycle. With composite resin SDX, which consisted of spherical inorganic filler particles and large organic filler particles, its wear was not influenced by increases in both brushing and occlusal cycles.

Effect of additive metals, Sn, Ga, and In in Ag-Pd-Au-Cu alloys on initial bond strength of 4-META adhesive cement to these alloys.

The purpose of this study was to investigate the effects of three additives, Sn, Ga, and In, as well as the main constituents, Pd and Cu, of Ag-Pd-Au-Cu alloys on the initial bond strength of 4-META adhesive cement to these alloys. The Ag-Pd-Au-Cu alloys consisted of 20%, 30% or 40% Pd, and 10%, 15% or 20% Cu, 20% Au, and Ag as balance. Besides, additive metals (Sn, Ga, and In) of 2% and 4% were added to these compositions. The addition of three additives, in general, increased the initial bond strength of the cement in comparison to the mother compositions (0% additives), although the degrees of effectiveness of the three additives were different and varied with their contents. Among these additives, a remarkable increase in bond strength was observed with the addition of In. The increase in Cu content, in many cases, resulted in an increase in bond strength at high Pd contents (30% and 40%), but a decrease at low Pd content (20%) in some cases. The positive effects of the three additives and Cu could be due to the formation of a suitable oxide layer for strong bonding with 4-META.

Survey on changes in subjective symptoms, onset/trigger factors, allergic diseases, and chemical exposures in the past decade of Japanese patients with multiple chemical sensitivity.

BACKGROUND: Recently, with rapid changes in the Japanese lifestyle, the clinical condition of patients with multiple chemical sensitivity (MCS) may also have undergone change. Thus, we conducted a new survey for subjective symptoms, ongoing chemical exposures, the prevalence of allergic diseases, and presumed onset/trigger factors in patients with MCS and compared results with those of an old survey from ten years ago. METHODS: The new survey was conducted from 2012 to 2015 and the old survey was independently conducted from 1999 to 2003, meaning it was not a follow-up study. Patients were initially diagnosed by physicians at five medical institutions with MCS specialty outpatient services, with 111 and 103 patients participating in the new and old surveys, respectively. The controls were a general population living in Japan, with 1313 and 2382 participants in the new and old surveys, respectively. Subjective symptoms and ongoing chemical exposure were evaluated using a quick environmental exposure sensitivity inventory. Additionally, from clinical findings recorded by an attending physician, the prevalence of allergic diseases and presumed onset/trigger factors were evaluated. Differences between new and old surveys were analyzed using logistic regression analyses and significance tests. RESULTS: Compared with ten years ago: (1) Regarding factors affecting patients with ongoing chemical exposures, the proportion of patients affected decreased significantly for two items only (insecticides and second-hand smoke). The proportion of controls showing ongoing exposure to 8 out of 10 items changed significantly. (2) In patients, scores for chemical intolerances, other intolerances, and life impacts increased significantly. (3) In terms of the prevalence of allergic diseases among patients with MCS, bronchial asthma (adjusted odds ratio [AOR]: 5.19), atopic dermatitis (AOR: 3.77), allergic rhinitis (AOR: 5.34), and food allergies (AOR: 2.63) increased significantly, while hay fever (AOR: 0.38) and drug allergies (AOR: 0.40) decreased significantly. (4) With regard to construction and renovation, which was the presumed predominant onset/trigger factor for MCS 10 years ago, this decreased from 68.9% to 35.1%; in contrast, electromagnetic fields (0.0%-26.1%), perfume (0.0%-20.7%), and medical treatment (1.9%-7.2%) increased significantly, confirming the diversification of onset/trigger factors. CONCLUSION: Compared to ten years ago, for patients with MCS, an increase in avoidance behavior toward chemical substance exposures, which were presumed to be aggravating factors for symptoms, was confirmed. It has been suggested that the ongoing chemical exposure of the general population in Japan has largely changed. In addition, for patients with MCS, chemical intolerances and life impacts have become severe, the prevalence of the main allergic diseases has increased, and onset/trigger factors have become diversified.

Development of casting investment preventing blackening of noble metal alloys. Part 4: effect of Mg(OH)2 and Ca(OH)2 as additives.

The objective of this study was to develop a casting investment that prevents the blackening of the cast surface of noble metal alloys. Experimental investments were prepared using a gypsum-bonded investment in which a hydroxide, namely Mg(OH)2 or Ca(OH)2, was added. An Ag-Pd-Cu-Au alloy was cast into the mold made of the prepared investment. The addition of both hydroxides showed a significant effect on the color of as-cast surfaces, which was improved with increase in additive content. When Mg(OH)2 or Ca(OH)2 was added at more than 4.0 mass% to the investment, it was useful in preventing the blackening of the as-cast surfaces of an Ag-Pd-Cu-Au alloy. As for differences in the effects between Mg(OH)2 and Ca(OH)2, they were not found.

Effects of occlusal and brushing forces on wear of composite resins.

Effects of occlusal and brushing forces on the wear of composite resins were investigated using three different wear tests: simulated occlusal wear test, toothbrush wear test, and combined wear test which carried out toothbrush wear test and occlusal wear test alternately. Test specimens were prepared from four commercial composite resins. Worn volume and maximum worn depth were measured under different occlusal forces (40 N and 80 N) and brushing forces (1.5 N and 3 N) in the three wear tests. Worn surfaces were observed using a SEM. In all the three wear tests, both higher occlusal and brushing forces resulted in significantly greater worn volume and higher maximum worn depth. The effects of occlusal force on worn volume and maximum worn depth varied with different composites, indicating that the four tested composites showed different wear behaviors under different occlusal forces and brushing forces. It was suggested that their different wear behaviors most probably stemmed from the differences in their filler systems.

[Trial of isolation of sick house syndrome and unclassified multiple chemical sensitivities--Definition of sick house syndrome, and symptoms].

PURPOSE: This study was designed to clarify the definition of sick house syndrome (SHS). METHODS: SHS was defined based on the disease related to habitation as follows. 1. The cause of the onset of a disease relates to house. 2. Symptoms appear within house. 3. Symptoms will be less serious or disappear if patient away from house. 4. If patient goes into house, symptoms will appear repeatedly. When it corresponded to all above, it was defined to SHS, and it classified as MCS (multiple chemical sensitivities) without above conditions. Even if SHS is isolated from similar disease completely, characteristic symptoms of MCS are hard to be detected because MCS are combination of two or more diseases. Based on this working hypothesis, the logistic regression by setting MCS as reference was performed so that characteristic symptoms of SHS show odds ratios with exceeding one. RESULTS: The odds ratios with more than two of characteristic symptoms in SHS were "nausea or vomiting" "Troublesome in everything" and the causative substances to which symptoms get worse was "The smell of a perfume and cosmetics". Characteristic symptoms of an allergy disease were detected by comparison with the allergic conjunctivitis, allergic rhinitis, and bronchial asthma, respectively. CONCLUSION: These results showed that the classification method was appropriate. This definition is not fundamentally differed from the definition of the sick-building syndrome of WHO.

Effect of material and configuration of antagonist on combined wear.

The aim of this study was to investigate the effect of antagonist material and configuration on combined wear, which was produced by alternating toothbrush wear and simulated occlusal wear on one specimen. Worn volume and maximum worn depth comparisons were done using two antagonist materials (steel and ceramic) and two antagonist configurations (flat and round). For the material factor, worn volume by the ceramic antagonist was greater than that by steel antagonist in the combined wear test. For the configuration factor, the round ceramic antagonist induced a greater volume loss of the resin composite. As for maximum worn depth, both the material and configuration of antagonist were influencing factors in the combined wear test--where the round ceramic antagonist induced a deeper wear of the resin composite. Based on the results of this study, we concluded that a round ceramic antagonist is suitable to be used for evaluating the wear behavior of resin composites.

Durability of diamond burs for the fabrication of ceramic crowns using dental CAD/CAM.

The diamond burs of two dental CAD/CAM systems (GN and CD) were examined if they could be used to fabricate up to 21 ceramic full crowns without fracture. After one, 11, and 21 machining times, the surfaces of the diamond burs were observed and the number of particles captured on SEM pictures was counted. The average surface roughness of the crowns was also measured. All diamond burs could be used to fabricate 21 ceramic crowns without fracture. A significant decrease in the number of diamond particles was found on the surfaces of GN burs after 11 and 21 machining times, but not on those of CD burs. The average surface roughness of GN crowns significantly increased with increase in the number of machining times. A significant positive correlation was found between the average surface roughness and the number of diamond particles.

Machining accuracy of CAD/CAM ceramic crowns fabricated with repeated machining using the same diamond bur.

The purpose of this study was to investigate the effect of repeated machining up to 51 times using the same diamond bur on machining accuracy of inner and outer surfaces of CAD/CAM (computer-aided designing and computer-aided manufacturing) machined ceramic crowns. The surface topography of machined crowns was examined using photographs. It was found that machining accuracy was not affected by the number of machining times. In all measuring points, the inner surface was machined to a dimension larger than the die model (i.e., increased gap), whereas the outer surface was machined to a dimension smaller than the crown model (i.e., smaller crown). Photo observation showed that cervical contour was machined in a clear, rounded form from 1st to 11th crowns.

[Complications of tracheostomy in patients with severe motor and intellectual disabilities and their management].

Some patient with severe motor and intellectual disabilities have a narrow mediastinum due to severe scoliosis or thoracic deformity. Complication of tracheostomy in these patients, such as granulation of the lower end of the cannula and tracheo-innominate artery fistulae, are difficult to treat. The causes of recurrent respiratory distress after tracheostomy in four patients with severe motor and intellectual disabilities were investigated, and its management was evaluated based on chest CT and bronchoscopy. In all patients, the lower end of the cannula was in contact with the site of tracheal stenosis, accompanied by granulation with arterial pulsation. In three patients, tracheomalacia as a complication of tracheostomy was also noted. In three patients, changing the cannula to fix its lower end proximally to the lesion, combined with stent placement in one patient with tracheomalacia, resulted in regression of the granulation and respiratory distress. However, one patient with severe tracheomalacia, who had been treated by stent placement alone, died of tracheo-innominate artery fistula. To prevent complications of tracheostomy in patients with severe motor and intellectual disabilities, it is important to select cannulas with a suitable length and angle. In the absence of severe tracheomalacia, use of custom-made short cannulas that can be fixed proximally to the site of stenosis and to the proximity of arteries are appropriate for this purpose.

Development of casting investment preventing blackening of noble metal alloys part 3. Effect of reducing agent addition on the strength and expansion of the investments.

Different reducing agents (B, Al, Si and Ti) were individually added to two gypsum-bonded investments to prepare investments preventing surface blackening of some noble cast alloys. The effect of different additive contents on green-body and burnout compressive strength, setting and thermal expansion of the investments were evaluated. The strength and expansion of the investments were changed by the additives. The compressive strength of Al-, Si- and Ti-added investments decreased with the increase of additive contents. The burnout strength of B-added investments significantly increased while green-body strength remained unchanged. The setting expansion of the B-added investments increased while those of the Al-, Si- and Ti-added investments decreased with the increase of additive contents. The thermal expansion of the Si- and Ti-added investments decreased, and that of the Al- and B-added investments remained unchanged. Further study is necessary to evaluate the effects of these additives on the accuracy of dental castings.

Development of metal-resin composite restorative material. Part 5: Evaluation of the bonding between Ag-Sn particle and 4-META coupling agent of the metal-resin composite.

This study evaluated the oxide characteristics on a Ag-Sn particle surface modified by acid and heat in order to understand the bonding mechanism. Nine different Ag-Sn particles including standard Sn, SnO and SnO2 were evaluated by X-ray Photoelectron Spectroscopy (XPS). The particles were also used for preparing the composite to test the flexural properties following the ISO 4049. A high correlation between flexural strength of the composites and Sn3d binding energy of their filler particles was found. Different oxide forms (SnO and SnO2) showed different adhesive abilities to bond with 4-META, regarding the difference in flexural strength of the composite. The highest flexural strength composite showed Sn3d binding energy of its filler at 486.4 eV, which was the SnO binding area. This implies that SnO was responsible for a good bond between particle surface and 4-META coupling agent.

Setting and flexural properties of metal-resin composite using Ag-Cu particles as filler and chemical accelerator.

A metal-resin composite material was experimentally prepared by mixing a powder consisting of Ag-Cu particles and BPO with a paste consisting of UDMA-based monomer and 4-META in the absence of tertiary amine. The working time and setting time were mainly affected by the amounts of 4-META, BPO and metal particles, most of them fulfilling the requirements for working time and setting time specified in ISO 4049:2000 in the present experimental conditions. The flexural strength ranged from 49.6 MPa to 77.8 MPa, and the highest value was obtained when the 4-META concentration was high and metal particle content was low. The flexural modulus of elasticity, ranging from 6.7 GPa to 11.9 GPa, significantly increased as the 4-META concentration and metal particle content increased. Based on its mechanical properties, this metal-resin composite in which metal particles are involved in the polymerization initiation system has the potential to be used as a dental restorative material.

Wear test combining simulated occlusal wear and toothbrush wear.

A new wear testing system, which carries out toothbrush wear and simulated occlusal wear tests alternately, was developed. Differences in wear behavior among three modes of wears, combined wear, toothbrush wear and simulated occlusal wear, were investigated using polymethylmethacrylate (PMMA) and two commercial resin composites (Z100, APX). The area of the material loss after each test was measured on the worn surfaces to evaluate the different modes of wears. On PMMA and Z100, the toothbrush wear corresponded to the combined wear, suggesting that toothbrush wear was dominant in the combined wear for these materials. On the other hand, the occlusal wear was dominant corresponding to the combined wear on APX. Both the simulated occlusal wear and toothbrush wear tests are essential to evaluate the wear behavior of restorative materials, and the combined wear test is effective to analyze the wear behavior of restorative materials under different wear processes which consist of toothbrush wear and simulated occlusal wear.