Resistencia a la tracción de coronas cementadas con lonomero de vidrio en dos preparaciones dentarias / Tensile strength of crowns glass ionomer cemented two dental preparations

El objetivo: del presente estudio fue evaluar el efecto del tipo de superficie de la preparación dentaria en relacion a la resistencia a la tracción de coronas metálicas completas cementadas con ionomero de vidrio sobre preparaciones dentarias con superficies pulidas y no pulidas. Material y métodos: Se realizaron 20 coronas metálicas en 20 piezas dentarias preparadas, las cuales se dividieron en dos grupos de 10 cada una, estas fueron sometidas a la prueba de tracción con la máquina de tracción Hounsfield, para determinar la fuerza de tracción necesaria para dislocarla. Resultados: mostraron que las preparaciones dentarias con superficies no pulidas (607.03N) mejoran la resistencia a la tracción en cornparación de las pulidas (359.90 N.

The purpose of the present study was to evaluate the effect of the type of surface of the dental preparation in the tensile strength of complete metal crowns cemented with glass ionomer as much in dental preparations with polished and not polished surfaces. 20 dental pieces were taken; teeth were divided in two groups of 10 teeth each. They were put under the test of traction with the Hounsfield traction machine. The results showed that the dental preparations with not polished surfaces (607.03 N) improve the tensile strenght in comparison of the polished ones (359.90 N).

Nonlinear and adiabatic control of high-Q photonic crystal nanocavities.

This article overviews our recent studies of ultrahigh-Q and ultrasmall photonic-crystal cavities, and their applications to nonlinear optical processing and novel adiabatic control of light. First, we show our latest achievements of ultrahigh-Q photonic-crystal nanocavities, and present extreme slow-light demonstration. Next, we show all-optical bistable switching and memory operations based on enhanced optical nonlinearity in these nanocavities with extremely low power, and discuss their applicability for realizing chip-scale all-optical logic, such as flip-flop. Finally, we introduce adiabatic tuning of high-Q nanocavities, which leads to novel wavelength conversion and another type of optical memories.

Waveguides, resonators and their coupled elements in photonic crystal slabs.

The design, fabrication, and measurement of photonic-band-gap (PBG) waveguides, resonators and their coupled elements in two-dimensional photonic crystal (PhC) slabs have been investigated. We have studied various loss mechanisms in PBG waveguides and have achieved a very low propagation loss (~1 dB/mm). For these waveguides, we have observed a large group delay (>100 ps) by time-domain measurement. As regards PBG resonators, we realize very high-Q and small volume resonators in PhC slabs by appropriate design. Finally, we demonstrate various forms of coupled elements of waveguides and resonators: 2-port resonant-tunneling transmission devices, 4-port channel-drop devices using the slow light mode, and 3-port channel-drop devices using the resonant-tunneling process.

Extremely large group-velocity dispersion of line-defect waveguides in photonic crystal slabs.

We reveal experimentally waveguiding characteristics and group-velocity dispersion of line defects in photonic crystal slabs as a function of defect widths. The defects have waveguiding modes with two types of cutoff within the photonic band gap. Interference measurements show that they exhibit extraordinarily large group dispersion, and we found waveguiding modes whose traveling speed is 2 orders of magnitude slower than that in air. These characteristics can be tuned by controlling the defect width, and the results agree well with theoretical calculations, indicating that we can design light paths with made-to-order dispersion.

Stimulation of the locus coeruleus suppresses trigeminal sensorimotor function in the rat.

The nucleus locus coeruleus (LC) has been implicated in the modulation of the spinal sensorimotor function. The aim of the present study was to examine the effect of electrical stimulation of the LC on sensorimotor function in the trigeminal system. The following two cases of sensorimotor behaviors mediated by the trigeminal brainstem sensory nuclear complex were examined: (1) the activity of the masseter muscle evoked by pressure on the region of the temporomandibular joint (TMJ); and (2) the activity of the digastric muscle evoked by electrical stimulation of the tooth pulp, resulting in the jaw-opening reflex. In the first case, LC stimulation at 10, 30 and 50 microA resulted in a 70%, 68% and 55% reduction in the magnitude of electromyogram (EMG) activity of the masseter muscle compared with the control (without LC stimulation), respectively. The threshold intensity for the onset of masseter EMG activity increaced to 106%, 111% and 121% of the control with 10, 30 and 50 microA LC stimulation, respectively. In the second case, EMG magnitude in response to the digastric muscle decreased to 42% of the control when 30 microA of LC stimulation was delivered. These results suggest that descending influences from the LC can act in suppression of the trigeminal sensorimotor function.

[Influence of firing times and temperature on color stability of low-fusing porcelains for high-functional gold alloys].

The purpose of this study was to investigate the effect of firing conditions on color stability. Three commercially available porcelains for high functional gold alloys, Carrara (CA), Deguceram Gold (DE) and Duceragold (DU) were used. In this study color stability was investigated under fire treatment of 1st, 3rd, 5th times and firing temperatures of 0, 20, and 40 degrees C higher than the manufactures standard temperature (CA: 845 degrees C, DE: 780 degrees C, DU: 780 degrees C). L* was degreased in CA 5 times, DE 3 times, DU by repeated firing. No difference was observed among L* of firing temperatures DE and DU, but L* was degreased in CA with firing temperatures of 40 degrees C higher. a* was degreased in CA, DU, DE with repeated firing, a* was degreased 5 times at firing temperatures of higher. b* was degreased in DU, but b* was increased in CA and DE with 5 firings. b* was increased with 5 findings at firing temperatures of 40 degrees C higher.

IgG4 deficiency with Rothmund-Thomson syndrome: a case report.

We describe a patient with Rothmund-Thomson syndrome and IgG4 deficiency. In vitro examination of his peripheral mononuclear cells revealed impaired IgG4 synthesis. Susceptibility to sinus and pulmonary infections was cured by monthly immunoglobulin infusions.

A case of Rothmund-Thomson syndrome with reduced DNA repair capacity.

BACKGROUND: Rothmund-Thomson syndrome is an autosomal recessively inherited disease with multiple skin disorders, and little has been known about the cause of the clinical features. We cultured the cells from a patient with Rothmund-Thomson syndrome and examined the ultraviolet repair characteristics. OBSERVATIONS: A 5-year-old boy with Rothmund-Thomson syndrome is presented. He has had reticular pigmentation and hypopigmentation on his cheeks, upper aspect of the trunk, palms, and soles since 6 months of age. Cells originating from the patient had reduced unscheduled DNA synthesis, 37% of normal, after exposure to ultraviolet C (predominantly at 254 nm), and they were slightly more sensitive to ultraviolet C than were normal cells in cell ultraviolet survival. CONCLUSION: Such repair deficiency might account for the mild sun sensitivity in early childhood. Heterogeneity in the repair mechanism as well as in clinical features in this syndrome was suggested.

Thalamic- and cerebellar-projecting interpolaris neuron responses to afferent inputs.

Thalamic- and cerebellar-projecting interpolaris neuron responses to afferent inputs from the temporomandibular joint (TMJ) and/or the masseter muscle (Mm) were examined in rats. Of 230 neurons tested, 24 could be antidromically stimulated from the contralateral ventral posteromedial thalamic nucleus (VPM), and 27 of 91 neurons tested were stimulated from the ipsilateral posteromedial part of crus II of the cerebellar cortex. None had dual projections. The thalamic-projecting neurons were recorded in the dorsomedial region of the interpolaris; most cerebellar-projecting neurons were at the medial border of the interpolaris. Ten of 24 thalamic- and 17 of 27 cerebellar-projecting neurons received nociceptive information. Afferent inputs from the TMJ and the Mm converged on 6 of 24 thalamic-projecting neurons and on 16 of 27 cerebellar-projecting neurons. In both the thalamic- and cerebellar-projecting neurons, there was no difference between the non-nociceptive and nociceptive neurons in mean antidromic latency. The results suggest that the interpolaris integrates and relays afferent inputs from deep oral structures.

Successful treatment of adult Henoch-Schönlein purpura with factor XIII concentrate.

We report the cases of three adult patients with severe abdominal complications of Henoch-Schönlein purpura who had low activity of factor XIII during the acute phase of the disease. In all three cases, abdominal symptoms and purpura immediately responded to heat-treated, placenta-derived factor XIII concentrate. No adverse effects were experienced. Factor XIII concentrate replacement should be considered as the initial treatment for severe abdominal symptoms in adult Henoch-Schönlein purpura associated with a decreased level of factor XIII activity.

[Effects of load and loading time on fracture toughness with indentation method].

For clinical application of ceramics such as porcelains that are frequently used as crown restoration materials, it is important to quantitatively evaluate and determine brittleness. This quality is expressed as a fracture toughness value, KIC, but no distinct method for its determination has yet been established. In order to standardize conditions for the determination of KIC by the indentation method, effects of indentation load and loading time on KIC of calcium phosphate crystalline ceramics (CP) were studied at various Vickers indentation loads and various loading times in CP plate-like segments. Furthermore, plate-like segments of each of CP, apatite (AP), mica-beta-spodumene (MIS) and mica (MIC) groups were subjected to experiment at various indentation loads at a fixed loading time to study the effects of indentation load on KIC in four kinds of Castable Ceramics. The results are summarized as follows: 1) The Vickers hardness degree of CP was decreased with an increase in indentation load and loading time, reaching the maximum value (499Hv) at 1kgf of indentation load and 5s of loading time. 2) The value of half of the crack length of CP was increased with an increase in indentation load and loading time, reaching a maximum (530 microns) at 20kgf of indentation load and 30s of loading time. 3) KIC of CP reached the maximum value (2.78MNm-3/2) at 5kgf of indentation load and 5s of loading time, and the minimum (1.52MNm-3/2) at 20kgf of indentation load and 30s of loading time. 4) Optimal experimental conditions for KIC of CP determined by indentation method were 5kgf or 10kgf of indentation load and 15s of loading time. 5) KIC values (MNm-3/2) determined at 5kgf of indentation load and 15s of loading time for CP, AP, MIS and MI were 2.27, 0.95, 1.82 and 1.81, respectively. 6) The course of cracks due to indentation force showed a linear pattern of intra-granular fracture. 7) The cracks were revealed to show median cracks by fractography.

[Fracture toughness of porcelain using indentation method].

Material resistance to brittle fracture was quantitatively evaluated in the commercial porcelains, CERA 8 (CE 8), VITA DUR (VITD), VITA VMK 68 (VIT), CERAMCO II (CE II), UNIBOND (UNB), NORITAKE SUPER PORCELAIN AAA (AAA), PENCRAFT (FEN), COSMOTECH (COM) and OPTEC HSP OPT) from values of fracture toughness (KIC) obtained in the crack on a mode I, determined upon insertion of Vickers indenter. The results are summarized as follows: 1) Mean maximum and minimum values of Vickers hardness degree of 9 kinds of commercial porcelains at 5kgf of load for 15s were 1348 (SD 98.1) for OPT abd 666 (SD 74.6) for CE 8, respectively. 2) The value of half of the diagonal of indentation (a) ranged from 42 (SD 1.5) to 58 (SD 3.3) microns, and that of half of the crack length (c) ranged from 101 (SD 4.0) to 175 (SD 17.2) microns. 3) The ratio of (c) to (a) (c/a ratio) was within the range of 2.3 to 3.3, and median cracks were present. 4) KIC in the commercial porcelains determined by the indentation method was within the range of 2.04 to 4.69MNm-3/2, showing a maximum for OPT and minimum for VITD. 5) KIC of OPT was significantly greater than that of any other material. 6) The porcelains were divided by fractography of the direction of crack course into 2 groups: a group of intra-granular fracture showing linear cracks (AAA, COM and OPT) and a group of Inter-granular fracture showing a range of non-linear cracks (CE 8, VITD, VIT, CE II, UNB ND PEN).

[Effects of additive oxide, repeating load on the fracture toughness of calcium phosphate crystalline ceramics (CPCC)].

This experimental study was performed to obtain fundamental data for the development of highly reinforced calcium phosphate crystalline ceramics (CPCC) by evaluation of fracture toughness by adding a single metal oxide such as B2O3, Na2O, Li2O, SiO2, MgO and Al2O3, which are thought to solidify and reinforce ceramics. In experiment I, values of fracture toughness for CPCC to which each oxide was added were determined by indentation method, and in experiment II dynamic test method by repeated loading was studied. The results are summarized as follows: 1) One half (a) of the diagonal of indentation was increased with an increase in indentation load, and the test fragment of CPCC with 4.7 mol% Na2O added at 10kgf of indentation load showed the maximum diagonal of indentation (145 microns), while the test fragment of CPCC containing 3.0mol% Al2O3 showed the minimum value (29 microns) at 1kgf. 2) One half (c) of the crack length was increased with an increase in indentation load, and the test fragment of CPCC containing 4.7mol% Li2O showed the maximum crack length (411 microns) at 10kgf, while the test fragment of CPCC with 4.7mol% B2O3 showed the minimum value (55 microns) at 1kgf. 3) The maximum value (2.98MNm-3/2) of fracture toughness (KIC) was observed in CPCC containing 4.7mol% B2O3 at 10kgf, while the minimum (1.02MNm-3/2) was observed in CPCC with 4.7mol% Li2O added, at 5kgf. 4) (a) was increased with an increase in the number of repetitions of loading, showing the maximum value (111 microns) for a test fragment at 10kgf with 100 repetitions and the minimum (31 microns) for a test fragment at 1kgf with just 1 repetition. 5) (c) was increased with an increase in the number of repetitions of loading, showing the maximum value (337 microns) for a test fragment at 10kgf with 100 repetitions and the minimum (64 microns) for a test fragment at 1kgf with 1 repetition. 6) KIC reached a maximum value (2.35MNm-3/2) at 5kgf and 1 of the repetition, and a minimum (1.54MNm-3/2) at 3kgf and 10 repetitions of loading.

[Effects of cross-linking agent on the bond strength of 4-META/MMA-TBB resin].

A cross-linking agent was added to increase the bonding strength of Superbond C & B by improving its cohesiveness. PMMA powder, which was copolymerized with 0.5% (w/w) neopentylglycol dimethacrylate as a cross-linking agent, was used for the preparation of Superbond C & B. The bonding of Superbond C & B to which the cross-linking agent had been added was then examined by the pull-out test using an alloy with different levels of surface roughness prepared by two surface-processing methods (polishing with #600 waterproof abrasive paper or 50 microns sandblast processing). The results were as follows: 1. Superbond C & B had a bonding strength of 205 kgf/cm2 after polish processing of the alloy with #600 waterproof abrasive paper and 199 kgf/cm2 after 50 microns sandblast processing. The t-test showed no significant difference between the two types of processing. 2. Superbond C & B to which the cross-linking agent had been added showed a bonding strength of 285 kgf/cm2 in the material processed with #600 waterproof abrasive paper and 347 kgf/cm2 in that processed with 50 microns sandblast processing. 3. Among various combinations of bonding agents and surface processing methods, the combination of Superbond C & B with the cross-linking agent and 50 microns sandblast processing showed the highest values under all conditions.

[Studies on thermal stimulation accompanying visible-light irradiation].

Visible-light-cured composite resin is one of the most frequently used materials in clinical practice. The use of this material inevitably involves dental pulp stimulation, i.e., thermal stimulation due to visible-light irradiation, during the restoration procedure. To determine the variations of temperature involved in visible-light irradiation, the author examines differences in temperature generated by various types of visible-light curing units. Changes in the temperature under varying conditions of irradiation were also examined. The results were as follows: 1) Among the visible-light curing units used in the present study, the highest temperature was obtained from Translux CL (a rise of 17 degrees C) whereas Hiliomat showed the lowest value (a rise of 7 degrees C). 2) The temperature increased with prolongation of irradiation time, reaching a maximum level (a rise of 15 degrees C) at 60s. 3) The temperature increased with shortening of irradiation distance, reaching a maximum level (a rise of 20 degrees C) at 3mm.

[Temporary restoration using light-cured resin].

In spite of various problems involved in chemically cured resin (self-curing resin), e.g., irritability, and heat and shrinkage at polymerization, it has traditionally been the material of choice in the production of temporary restorations. However, light-cured resin, which does not have the disadvantages of chemically cured resin, has recently been developed and applied to clinical treatment. The present study was conducted to examine the clinical application of light-cured resin to temporary crowns. Two types of light-cured resin and one type of chemically cured resin were examined for their mechanical properties. The properties involved in handling and setting, and the methods of producing crowns were also studied. The results were as follows: 1) In the tensile strength test, there was no significant difference between the two types of light-cured resin, i.e., Triad and Unifast LC. The tensile strength of Unifast, a chemically cured resin, was slightly greater than the others, the difference being significant. 2) The Vickers hardness test showed no significant differences between the three types of resin. 3) The mechanical properties of Triad were not influenced by differences in the curing unit (the unit for general oral use or exclusive use) used for polymerization. 4) The test of setting properties revealed that Unifast LC needed longer than Unifast from the 2nd through the 4th clinical stage. In particular, Unifast LC required about 2.5 times the duration needed by Unifast at the 2nd stage in the tray method. 5) The heat generation test showed that the exothermic temperature in Unifast was significantly higher than in the two types of light-cured resin. 6) Heat generation associated with light curing was noted during the use of a light-curing unit for oral use.

[Bonding strength of adhesive resin and calcium phosphate crystalline ceramics (CPCC)].

The bond strengths of two adhesives, Panavia EX (PE) and Superbond C & B (SB), and calcium phosphate crystalline ceramics (CPCC) were examined. Two square pieces of CPCC were joined to each other using PE, and another two pieces were joined using SB at adhesion loads of 0.2kgf and 15.0kgf. The adhered specimens were left at 37 degrees C and 60 degrees C in thermostatically controlled purified water baths for 24 hours. The bond strength was determined by means of an apparatus to measure compressive shear and bond strength. Stress distribution on the interfaces with compressive shear where the adhesive was applied was also studied by a two-dimensional photoelastic experiment. The results were as follows. 1) The test pieces joined with PE at 0.2kgf and left at 37 degrees C provided the maximum bond strength, 69 +/- 16.8kgf/cm2, while those joined at 15.0kgf and left at 60 degrees C provided the minimum bond strength, 10 +/- 5.6kgf/cm2. 2) The test pieces joined with SB at 15.0kgf and left at 60 degrees C and those joined at 0.2kgf and left at 37 degrees C provided the maximum and minimum bond strengths: 179 +/- 36.8kgf/cm2 and 70 +/- 10kgf/cm2, respectively. 3) When the adhesion load was increased from 0.2kgf to 15.0kgf, the coat thickness for PE and SB were decreased from 45 microns (SD = 11.7) to 20 microns (SD = 2.8) and from 68 microns (SD = 24.5) to 18 microns (SD = 2.9), respectively. 4) The bond strengths of PE and SB for CPCC were decreased and increased, respectively, by an increase in adhesion load, i.e., a decrease in the thickness of the coat, and an increase in the temperature of maintenance after adhesion. 6) The photoelastic experiment revealed no differences in stress distribution or shear stress between the combinations of PE and SB adhesives and adherends of SUS304 and CPCC. 7) Shear stress was distributed to the area ranging from the site of load to the base of load on the interfaces with compressive shear where adhesive was applied.