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1.
J Contemp Dent Pract ; 22(6): 605-609, 2021 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-34393114

RESUMO

AIM AND OBJECTIVE: The present study compared the frictional forces of three types of self-ligating lingual appliances. MATERIALS AND METHODS: The lingual appliances (2D, Forestadent; Alias, Ormco; and Clippy L, Tomy International) consisted of a self-ligating bracket (second premolar) and two self-ligating tubes (first and second molars) bonded to a stainless steel jig and attached to a "drawing-friction tester." Full-size and non-full-size stainless steel archwires were tested, and the static and kinetic friction acting on six lingual appliance/wire combinations was estimated (n = 5). Three-dimensional micro-computed tomography (micro-CT) analysis of each premolar bracket was performed. The frictional forces were compared between the bracket/wire combinations using the Kruskal-Wallis and Mann-Whitney U tests. RESULTS: The Alias and Clippy L bracket/wire combinations had greater contact between the wire surfaces and bracket slots compared to the 2D bracket/wire combination. For all lingual appliances, the static and kinetic frictional forces were significantly higher for the full-size than non-full-size archwire. The 2D bracket, which had a wider outer wing, had less frictional force than the other appliances. The Alias, which had a narrower outer wing, had a significantly lower frictional force than the Clippy L. CONCLUSIONS: Frictional force was significantly higher for heavier full-size bracket/archwire combinations than for non-full-size archwires. The 2D bracket had lower frictional force due to its archwire-holding mechanism. The outer wing width may influence the frictional resistance. CLINICAL SIGNIFICANCE: The frictional forces of self-ligating lingual appliances vary, and bracket design and archwire size may influence the frictional performance.


Assuntos
Braquetes Ortodônticos , Fios Ortodônticos , Ligas Dentárias , Análise do Estresse Dentário , Fricção , Humanos , Teste de Materiais , Desenho de Aparelho Ortodôntico , Aço Inoxidável , Titânio , Microtomografia por Raio-X
2.
Dent Mater J ; 39(4): 593-600, 2020 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-32092724

RESUMO

We investigated the surface modification of orthodontic stainless steel wire using electrophoretic deposition (EPD) of bioactive glass (BG). BG coatings were characterized by spectrophotometry, three-dimensional (3D) focal laser scanning microscopy and scanning electron microscopy. The mechanical properties of the BG-coated wires were estimated nanoindentation, three-point bending and drawing friction tests. BG-coated specimens prepared at higher voltage showed higher values for both reflectance and L* compared to those prepared at lower voltage. Specimens coated at higher voltage had significantly lower surface roughness than those coated at lower voltage, and their BG layers had higher hardness and elastic modulus values. In the three-point bending test, BG-coated wires produced significantly lower elastic modulus than non-coated wires. Most BG-coated specimens produced similar frictional forces to those produced by non-coated specimens. The surface modification technique applying EPD and BG coating to orthodontic stainless steel wire could be used to develop new esthetical orthodontic wire.


Assuntos
Braquetes Ortodônticos , Fios Ortodônticos , Ligas Dentárias , Fricção , Vidro , Teste de Materiais , Aço Inoxidável , Propriedades de Superfície , Titânio
3.
Eur J Oral Sci ; 125(2): 160-167, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28145593

RESUMO

In this study, wear and inhibition of enamel demineralization by resin-based coating materials were investigated. Seven commercially available coating materials, with and without fillers, were used. A mechanical wear test was performed, and the specimens were then examined with a scanning electron microscope. Hardness and elastic modulus measurements for each material were obtained by nanoindentation testing. Thin layers of each material were applied on human enamel surfaces, which were subjected to alternating immersion in demineralizing and remineralizing solutions. The inhibition ability of enamel demineralization adjacent to the coating was estimated with depth-dependent mechanical properties using the nanoindentation test. The non-filled coating material showed significantly lower hardness, lower elastic modulus, and higher weight loss. There were no significant differences in weight loss among the six filled coating materials. After the alternating immersion protocol, the enamel specimens having application of coating materials with ion-releasing ability were harder than those in the other groups in some locations 1-11 µm from the enamel surface and within 300 µm from the edge of the coating materials. In conclusion, clinical use of the resin-based coating materials with ion-releasing ability may prevent demineralization of exposed enamel adjacent to the coating during treatment.


Assuntos
Esmalte Dentário/efeitos dos fármacos , Adesivos Dentinários/química , Cimentos de Resina/química , Desmineralização do Dente/prevenção & controle , Dente Pré-Molar , Módulo de Elasticidade , Dureza , Humanos , Técnicas In Vitro , Teste de Materiais , Microscopia Eletrônica de Varredura
4.
J Biomed Mater Res B Appl Biomater ; 105(5): 1151-1156, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-27029842

RESUMO

We investigated the effects of the addition of chitosan fiber (biomass nanofiber made by Sugino (BiNFi-s)) to polyether-based thermoplastic polyurethane (TPU) on material properties. BiNFi-s (2 and 5 wt %)/TPU composite materials were prepared via compression molding, and glass fiber (2 and 5 wt %)/TPU composite materials and plain TPU were also prepared for comparison. The glass transition temperature was analyzed using differential scanning calorimetry, and the crystal structure was investigated using X-ray diffraction. 20-mm-long test specimens with cross-sectional dimensions of 1 mm × 1 mm were cut from sheets of the composite materials, and three-point bending tests were carried out using a universal testing machine to investigate their mechanical properties and shape memory. The addition of BiNFi-s or glass fiber to TPU did not influence the glass transition temperature, although the crystal structure changed from semi-crystalline to amorphous. The elastic modulus increased 40% by the addition of 5 wt % BiNFi-s (2.31 MPa) compared with plain TPU (1.65 MPa), and these composites exhibited shape recovery with clinically relevant changes in temperature. The addition of 5 wt % BiNFi-s into TPU resulted in an improvement in the elastic modulus without any decrease in the shape memory effect. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1151-1156, 2017.


Assuntos
Quitosana/química , Módulo de Elasticidade , Temperatura Alta , Poliuretanos/química
5.
Angle Orthod ; 87(4): 610-617, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27731649

RESUMO

OBJECTIVE: To analyze the coatings covering esthetic orthodontic wires and the influence of such coatings on bending and frictional properties. MATERIALS AND METHODS: Four commercially available, coated esthetic archwires were evaluated for their cross-sectional dimensions, surface roughness (Ra), nanomechanical properties (nanohardness, nanoelastic modulus), three-point bending, and static frictional force. Matched, noncoated control wires were also assessed. RESULTS: One of the coated wires had a similar inner core dimension and elasticity compared to the noncoated control wire, and no significant differences between their static frictional forces were observed. The other coated wires had significantly smaller inner cores and lower elasticity compared to the noncoated wires, and one of them showed less static frictional force than the noncoated wire, while the other two coated wires had greater static frictional force compared to their noncoated controls. The dimension and elastic modulus of the inner cores were positively correlated (r = 0.640), as were frictional force and total cross-sectional (r = 0.761) or inner core (r = 0.709) dimension, elastic modulus (r = 0.777), nanohardness (r = 0.802), and nanoelastic modulus (r = 0.926). The external surfaces of the coated wires were rougher than those of their matched controls, and the Ra and frictional force were negatively correlated (r = -0.333). CONCLUSIONS: Orthodontic coated wires with small inner alloy cores withstand less force than expected and may be unsuitable for establishing sufficient tooth movement. The frictional force of coated wires is influenced by total cross-section diameter, inner core diameter, nanohardness, nanoelastic modulus, and elastic modulus.


Assuntos
Materiais Revestidos Biocompatíveis , Teste de Materiais , Fricção em Ortodontia , Fios Ortodônticos , Ligas Dentárias , Análise do Estresse Dentário , Módulo de Elasticidade , Humanos , Desenho de Aparelho Ortodôntico
6.
Eur J Oral Sci ; 123(3): 202-7, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25903115

RESUMO

We investigated the enamel demineralization-prevention ability and shear bond strength (SBS) properties of 4-methacryloxyethyl trimellitic anhydride/methyl methacrylate-tri-n-butyl borane (4-META/MMA-TBB)-based resin containing various amounts (0-50%) of bioactive glass (BG). Disk-shaped specimens were immersed in distilled water and ions released were analysed by inductively coupled plasma atomic-emission spectroscopy. Samples were also immersed in lactic acid solution (pH 4.6) to estimate acid-neutralizing ability. Brackets were bonded to human premolars with BG-containing resins and the bonded teeth were alternately immersed in demineralizing (pH 4.55) and remineralizing (pH 6.8) solutions for 14 d. The enamel hardness was determined by nanoindentation testing at twenty equidistant distances from the external surface. The SBS for each sample was examined. The amounts of ions released [calcium (Ca), sodium (Na), silicon (Si), and boron (B)] and the acid-neutralizing ability increased with increasing BG content. After alternating immersion, the specimens bonded with the BG-containing resin with high BG content were harder than those in the other groups in some locations 1-18.5 µm from the enamel surface. Bioactive glass-containing (10-40%) resin had bond strength equivalent to the control specimen. Thus, the SBS obtained for BG-containing resin (6.5-9.2 MPa) was clinically acceptable, suggesting that this material has the ability to prevent enamel demineralization.


Assuntos
Compostos de Boro/uso terapêutico , Cerâmica/uso terapêutico , Colagem Dentária , Esmalte Dentário/efeitos dos fármacos , Metacrilatos/uso terapêutico , Metilmetacrilatos/uso terapêutico , Cimentos de Resina/uso terapêutico , Desmineralização do Dente/prevenção & controle , Boro/química , Compostos de Boro/química , Tampões (Química) , Cálcio/química , Cerâmica/química , Esmalte Dentário/ultraestrutura , Vidro/química , Dureza , Humanos , Concentração de Íons de Hidrogênio , Imersão , Ácido Láctico/química , Teste de Materiais , Metacrilatos/química , Metilmetacrilatos/química , Braquetes Ortodônticos , Cimentos de Resina/química , Resistência ao Cisalhamento , Silício/química , Sódio/química , Espectrofotometria Atômica , Estresse Mecânico , Fatores de Tempo , Remineralização Dentária
7.
Dent Mater J ; 34(2): 189-95, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25740165

RESUMO

This study investigated high-cycle fatigue behavior in three ß-Ti wires (TMA, Resolve, Gummetal). Fatigue was evaluated using a static three-point bending test and a high-cycle fatigue test with a three-point bending mode. The surfaces of fractured wires were observed with scanning electron microscopy, and the post-fatigue crystal structures were determined by micro-X-ray diffraction. The Gummetal wire exhibited the lowest elastic modulus, bending strength and fatigue limit, and exhibited the highest resilience of the three types of wire studied. However, no difference in the number of cycles to failure was observed among the three types of wire. The fatigue crack propagation and rapid propagation regions of all wires contained single-phase ß-Ti. The elastic modulus and bending strength influenced the fatigue limit, although these properties did not affect the number of cycles to fracture. The three types of ß-Ti wires exhibited similar risks of wire fracture.


Assuntos
Titânio/química , Ligas Dentárias/química , Análise do Estresse Dentário , Elasticidade , Falha de Equipamento , Humanos , Teste de Materiais , Microscopia Eletrônica de Varredura , Fios Ortodônticos , Estresse Mecânico , Propriedades de Superfície
8.
Eur J Orthod ; 37(6): 665-70, 2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-25788333

RESUMO

BACKGROUND/OBJECTIVE: To investigate the effects of temperature changes and stress loading on the mechanical and shape memory properties of thermoplastic materials with different glass transition behaviours and crystal structures. MATERIALS/METHODS: Five thermoplastic materials, polyethylene terephthalate glycol (Duran®, Scheu Dental), polypropylene (Hardcast®, Scheu Dental), and polyurethane (SMP MM®, SMP Technologies) with three different glass transition temperatures (T g) were selected. The T g and crystal structure were assessed using differential scanning calorimetry and X-ray diffraction. The deterioration of mechanical properties by thermal cycling and the orthodontic forces during stepwise temperature changes were investigated using nanoindentation testing and custom-made force-measuring system. The mechanical properties were also evaluated by three-point bending tests; shape recovery with heating was then investigated. RESULTS: The mechanical properties for each material were decreased significantly by 2500 cycles and great decrease was observed for Hardcast (crystal plastic) with higher T g (155.5°C) and PU 1 (crystalline or semi-crystalline plastic) with lower T g (29.6°C). The Duran, PU 2, and PU 3 with intermediate T g (75.3°C for Duran, 56.5°C for PU 2, and 80.7°C for PU 3) showed relatively stable mechanical properties with thermal cycling. The polyurethane polymers showed perfect shape memory effect within the range of intraoral temperature changes. The orthodontic force produced by thermoplastic appliances decreased with the stepwise temperature change for all materials. CONCLUSIONS/IMPLICATIONS: Orthodontic forces delivered by thermoplastic appliances may influence by the T g of the materials, but not the crystal structure. Polyurethane is attractive thermoplastic materials due to their unique shape memory phenomenon, but stress relaxation with temperature changes is expected.


Assuntos
Vidro/química , Plásticos/química , Varredura Diferencial de Calorimetria , Cristalografia , Módulo de Elasticidade , Dureza , Humanos , Teste de Materiais , Transição de Fase , Maleabilidade , Polietilenoglicóis/química , Polietilenotereftalatos/química , Polímeros/química , Polipropilenos/química , Poliuretanos/química , Estresse Mecânico , Propriedades de Superfície , Temperatura , Temperatura de Transição , Difração de Raios X
9.
J Mater Sci Mater Med ; 26(2): 71, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25631268

RESUMO

This study investigated in vivo degradation of Ti-6Al-4V alloy miniscrew implants. Miniscrew implants were placed in patients, and the surfaces were studied upon retrieval by scanning electron microscopy, microscale X-ray photoelectron spectroscopy, elastic recoil detection analysis and nanoindentation testing. Bone-like structures were formed on the retrieved specimens. The hardness and elastic modulus of the surfaces of the retrieved specimens were significantly lower than the as-received specimens, although no statistically significant differences were observed for the hardness and elastic modulus in the bulk region. Thick organic over-layer containing carbon, oxygen, and nitrogen, with the thickness greater than 50 nm, covered the retrieved specimens, and higher concentrations of hydrogen were detected in the retrieved specimens compared with the as-received specimens. Minimal degradation of the bulk mechanical properties of miniscrew implants was observed after clinical use, although precipitation of bone-like structures, formation of a carbonaceous contamination layer, and hydrogen absorption were observed on the surfaces of miniscrew implants.


Assuntos
Parafusos Ósseos , Implantes Dentários para Um Único Dente , Materiais Dentários/química , Prótese Dentária Fixada por Implante , Procedimentos de Ancoragem Ortodôntica/instrumentação , Titânio/química , Corrosão , Planejamento de Prótese Dentária , Falha de Restauração Dentária , Remoção de Dispositivo , Módulo de Elasticidade , Contaminação de Equipamentos , Análise de Falha de Equipamento , Dureza , Miniaturização , Propriedades de Superfície
10.
Dent Mater J ; 33(3): 430-6, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24882113

RESUMO

This study investigated the like-remineralizing ability of experimental toothpaste containing surface reaction-type pre-reacted glassionomer (S-PRG) filler on etched enamel. Human enamel blocks were etched with 35% phosphoric acid and immersed in 5-mL distilled water, fourfold diluted solution of NaF-containing toothpaste, or S-PRG filler-containing experimental toothpaste. Nanoindentation testing was carried out during immersion and the enamel surfaces were observed by scanning electron microscopy. Elemental analysis of the ions in each solution was performed using inductively coupled plasma atomic emission spectroscopy and fluoride electrode. After 1 month of immersion, the hardness and elastic modulus of the specimen immersed in S-PRG filler-containing toothpaste showed significantly greater values than those of the specimen immersed in NaF-containing toothpaste. Considerable amounts of Al, B, Na, Si, Sr, F ions were detected in the solution of S-PRG filler-containing toothpaste. Experimental S-PRG filler-containing toothpaste may enhance the like-remineralizing ability of etched enamel surfaces due to its ion-releasing ability.


Assuntos
Condicionamento Ácido do Dente , Esmalte Dentário , Remineralização Dentária , Cremes Dentais , Soluções
11.
Angle Orthod ; 84(6): 1054-61, 2014 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-24738791

RESUMO

OBJECTIVE: To investigate the effects of third-order torque on frictional properties of self-ligating brackets (SLBs). MATERIALS AND METHODS: Three SLBs (two passive and one active) and three archwires (0.016 × 0.022-inch nickel-titanium, and 0.017 × 0.025-inch and 0.019 × 0.025-inch stainless steel) were used. Static friction was measured by drawing archwires though bracket slots with four torque levels (0°, 10°, 20°, 30°), using a mechanical testing machine (n  =  10). A conventional stainless-steel bracket was used for comparison. RESULTS were subjected to Kruskal-Wallis and Mann-Whitney U-tests. Contact between the bracket and wire was studied using a scanning electron microscope. RESULTS: In most bracket-wire combinations, increasing the torque produced a significant increase in static friction. Most SLB-wire combinations at all torques produced less friction than that from the conventional bracket. Active-type SLB-wire combinations showed higher friction than that from passive-type SLB-wire combinations in most conditions. When increasing the torque, more contact between the wall of a bracket slot and the edge of a wire was observed for all bracket types. CONCLUSIONS: Increasing torque when using SLBs causes an increase in friction, since contact between the bracket slot wall and the wire edge becomes greater; the design of brackets influences static friction.


Assuntos
Desenho de Aparelho Ortodôntico , Braquetes Ortodônticos , Fios Ortodônticos , Ligas/química , Ligas Dentárias/química , Análise do Estresse Dentário/instrumentação , Fricção , Humanos , Teste de Materiais , Microscopia Eletrônica de Varredura , Níquel/química , Aço Inoxidável/química , Estresse Mecânico , Propriedades de Superfície , Titânio/química , Torque
12.
Dent Mater J ; 32(5): 775-80, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-24088833

RESUMO

In this work, a bioactive glass was deposited on the alumina disk specimens by radio-frequency magnetron sputtering to study crystal formation ability in artificial saliva. Bioactive glass-coated specimens were immersed in artificial saliva for 1 week and 6 months. The specimens were observed with a scanning electron microscope (SEM) and the composition was determined by energy dispersive spectroscopy (EDS). The crystals that formed on the specimens were analyzed by Raman spectroscopic analysis and Micro-X-ray diffraction. SEM photomicrographs showed the formation of needle-like structures after immersion for 1 week, and tabular structures formed on the surface of the specimen for 6 months. EDS showed that both the needle-like and tabular structures were enriched with Ca and P. Raman and Micro-XRD spectra for the tabular structure showed peaks that may correspond to calcium phosphate. Thus, when immersed in artificial saliva, bioactive glass-coated alumina produced a crystal which might be calcium phosphate.


Assuntos
Óxido de Alumínio , Materiais Biocompatíveis , Cristalização , Vidro , Saliva , Cristalografia por Raios X , Microscopia Eletrônica de Varredura , Análise Espectral Raman
13.
Dent Mater J ; 32(1): 156-64, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23370885

RESUMO

This study investigated fluoride release, acid resistance and shear bond strength (SBS) of new 4-META/MMA-TBB-based fluoride-containing resin adhesive (Super-Bond/F3). Super-Bond, Transbond Plus and Fuji Ortho LC were selected for comparison. Fluoride release into distilled water during 6-month period was measured using disk-shaped specimens. Brackets were bonded to human premolars with each material and then the specimens for the nanoindentation test were subjected to alternating immersion (demineralizing and remineralizing solutions); the hardness and elastic modulus of the enamel around bracket were determined. Rest of the specimens was subjected to examine the SBS. Super-Bond/F3 and Fuji Ortho LC showed significantly greater fluoride release compared with the other materials. The reductions in hardness and the elastic modulus for Super-Bond/F3 and Fuji Ortho LC were lower than those for the other materilas. Super-Bond and Super-Bond/F3 showed significantly greater SBS than Fuji Ortho FC. In conclusion, Super-Bond/F3 showed high fluoride-release, cariostatic potential and equivalent SBS.


Assuntos
Esmalte Dentário/química , Fluoretos , Cimentos de Resina/química , Desmineralização do Dente/prevenção & controle , Análise de Variância , Análise do Estresse Dentário , Módulo de Elasticidade , Fluoretos/química , Fluoretos/farmacologia , Dureza , Humanos , Resistência ao Cisalhamento , Estatísticas não Paramétricas , Desmineralização do Dente/induzido quimicamente
14.
Eur J Orthod ; 35(2): 216-22, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-21934113

RESUMO

This study investigated the effects of a diamond-like carbon (DLC) coating on frictional and mechanical properties of orthodontic brackets. DLC films were deposited on stainless steel brackets using the plasma-based ion implantation/deposition (PBIID) method under two different atmospheric conditions. As-received metal brackets served as the control. Two sizes of stainless steel archwires, 0.018 inch diameter and 0.017 × 0.025 inch cross-section dimensions, were used for measuring static and kinetic friction by drawing the archwires through the bracket slots, using a mechanical testing machine (n = 10). The DLC-coated brackets were observed with a scanning electron microscope (SEM). Values of hardness and elastic modulus were obtained by nanoindentation testing (n = 10). Friction forces were compared by one-way analysis of variance and the Scheffé test. The hardness and elastic modulus of the brackets were compared using Kruskal-Wallis and Mann-Whitney U-tests. SEM photomicrographs showed DLC layers on the bracket surfaces with thickness of approximately 5-7 µm. DLC-coated brackets deposited under condition 2 showed significantly less static frictional force for the stainless steel wire with 0.017 × 0.025 inch cross-section dimensions than as-received brackets and DLC-coated brackets deposited under condition 1, although both DLC-coated brackets showed significantly less kinetic frictional force than as-received brackets. The hardness of the DLC layers was much higher than that of the as-received bracket surfaces. In conclusion, the surfaces of metal brackets can be successfully modified by the PBIID method to create a DLC layer, and the DLC-coating process significantly reduces frictional forces.


Assuntos
Carbono , Diamante , Fricção , Braquetes Ortodônticos , Fios Ortodônticos , Análise do Estresse Dentário , Elasticidade , Testes de Dureza , Humanos , Cinética , Masculino , Desenho de Aparelho Ortodôntico , Análise Espectral Raman/métodos , Aço Inoxidável
15.
Mech Dev ; 130(2-3): 169-80, 2013 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23041176

RESUMO

Animals often show left-right (LR) asymmetry in their body structures. In some vertebrates, the mechanisms underlying LR symmetry breaking and the subsequent signals responsible for LR asymmetric development are well understood. However, in invertebrates, the molecular bases of these processes are largely unknown. Therefore, we have been studying the genetic pathway of LR asymmetric development in Drosophila. The embryonic gut is the first organ that shows directional LR asymmetry during Drosophila development. We performed a genetic screen to identify mutations affecting LR asymmetric development of the embryonic gut. From this screen, we isolated pebble (pbl), which encodes a homolog of a mammalian RhoGEF, Ect2. The laterality of the hindgut was randomized in embryos homozygous for a null mutant of pbl. Pbl is a multi-functional protein required for cytokinesis and the epithelial-to-mesenchymal transition in Drosophila. Consistent with Pbl's role in cytokinesis, we found reduced numbers of cells in the hindgut epithelium in pbl homozygous embryos. The specific expression of pbl in the hindgut epithelium, but not in other tissues, rescued the LR defects and reduced cell number in embryonic pbl homozygotes. Embryos homozygous for string (stg), a mutant that reduces cell number through a different mechanism, also showed LR defects of the hindgut. However, the reduction in cell number in the pbl mutants was not accompanied by defects in the specification of hindgut epithelial tissues or their integrity. Based on these results, we speculate that the reduction in cell number may be one reason for the LR asymmetry defect of the pbl hindgut, although we cannot exclude contributions from other functions of Pbl, including regulation of the actin cytoskeleton through its RhoGEF activity.


Assuntos
Proteínas de Drosophila/genética , Drosophila melanogaster/embriologia , Trato Gastrointestinal/embriologia , Fatores de Troca do Nucleotídeo Guanina/genética , Alelos , Animais , Padronização Corporal/genética , Contagem de Células , Polaridade Celular , Citocinese , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/citologia , Drosophila melanogaster/genética , Células Epiteliais/fisiologia , Epitélio/embriologia , Epitélio/metabolismo , Trato Gastrointestinal/citologia , Deleção de Genes , Expressão Gênica , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Homozigoto , Especificidade de Órgãos , Mutação Puntual , Sítios de Splice de RNA , Análise de Sequência de DNA
16.
Angle Orthod ; 83(3): 476-83, 2013 May.
Artigo em Inglês | MEDLINE | ID: mdl-23035832

RESUMO

OBJECTIVE: To measure the forces delivered by thermoplastic appliances made from three materials and investigate effects of mechanical properties, material thickness, and amount of activation on orthodontic forces. MATERIALS AND METHODS: Three thermoplastic materials, Duran (Scheu Dental), Erkodur (Erkodent Erich Kopp GmbH), and Hardcast (Scheu Dental), with two different thicknesses were selected. Values of elastic modulus and hardness were obtained from nanoindentation measurements at 28°C. A custom-fabricated system with a force sensor was employed to obtain measurements of in vitro force delivered by the thermoplastic appliances for 0.5-mm and 1.0-mm activation for bodily tooth movement. Experimental results were subjected to several statistical analyses. RESULTS: Hardcast had significantly lower elastic modulus and hardness than Duran and Erkodur, whose properties were not significantly different. Appliances fabricated from thicker material (0.75 mm or 0.8 mm) always produced significantly greater force than those fabricated from thinner material (0.4 mm or 0.5 mm). Appliances with 1.0-mm activation produced significantly lower force than those with 0.5-mm activation, except for 0.4-mm thick Hardcast appliances. A strong correlation was found between mechanical properties of the thermoplastic materials and force produced by the appliances. CONCLUSIONS: Orthodontic forces delivered by thermoplastic appliances depend on the material, thickness, and amount of activation. Mechanical properties of the polymers obtained by nanoindentation testing are predictive of force delivery by these appliances.


Assuntos
Análise do Estresse Dentário , Desenho de Aparelho Ortodôntico/métodos , Plásticos/química , Técnicas de Movimentação Dentária/instrumentação , Análise de Variância , Modelos Dentários , Módulo de Elasticidade , Dureza , Teste de Materiais
17.
Eur J Orthod ; 35(5): 577-82, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22952154

RESUMO

The aim of this study was to investigate the effect of immediate loading on the biomechanical properties of bone surrounding a miniscrew implant. Forty titanium alloy miniscrew implants were placed on the buccal side of the maxillae and mandibles in four beagle dogs. Twelve pairs of miniscrew implants were immediately loaded with approximately 150 g of continuous force using nickel-titanium coil springs and the remaining 16 implants were left unloaded for 8 weeks. Nanoindentation testing was performed (peak load 10 mN) and the hardness and elastic modulus were calculated. Two series of indentations (in cortical and trabecular bone) for both the compression and tension sides were made. For each site, five indentations were placed approximately 25 µm from the implant-bone interface and 250 µm from the screw thread. The mean hardness and elastic modulus were generally higher in mandibles than maxillae and were higher in cortical bone than in trabecular bone. The trabecular bone near the implant-bone interface on the compression side was significantly harder than that at other locations in trabecular bone. In conclusion, this is the first study that has investigated the biomechanical properties of bone surrounding a miniscrew implant under immediate loading using nanoindentation testing. The mechanical properties of bone surrounding a miniscrew implant may be influenced by immediate loading.


Assuntos
Parafusos Ósseos , Osso e Ossos/fisiologia , Implantes Dentários , Carga Imediata em Implante Dentário , Animais , Fenômenos Biomecânicos , Cães , Módulo de Elasticidade , Masculino , Mandíbula/cirurgia , Maxila/cirurgia , Níquel , Titânio
18.
Eur J Orthod ; 35(5): 583-9, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-23041933

RESUMO

This study examined the influence of the quantity and quality of cortical bone on the failure force of miniscrew implants. Twenty-six titanium alloy miniscrew implants (AbsoAnchor) 1.4mm in diameter and 5 or 7 mm long were placed in cross-sectioned maxillae (n = 6) and mandibles (n = 20) of human cadavers. Computed tomography imaging was used to estimate the cortical bone thickness and bone mineral density [total bone mineral density (TBMD, values obtained from cortical bone plus trabecular bone); cortical bone mineral density (CBMD, values obtained from only cortical bone)]. Maximum force at failure was measured in a shear test. Nanoindentation tests were performed to measure the hardness and elastic modulus of cortical bone around the miniscrew implants. The mean failure force of miniscrew implants placed in mandibles was significantly greater than that for implants in maxillae, and the bone hardness of mandibles was significantly greater than that of maxillae. The length of miniscrew implants did not influence the mean failure force in monocortical placement in the mandible. Cortical bone thickness, TBMD, CBMD, and bone hardness were significantly related to the mean failure force. CBMD was related to the mechanical properties of cortical bone. In conclusion, the quantity and quality of cortical bone greatly influenced the failure force of miniscrew implants.


Assuntos
Densidade Óssea , Parafusos Ósseos , Implantes Dentários , Falha de Restauração Dentária , Procedimentos de Ancoragem Ortodôntica , Ligas , Cadáver , Humanos , Mandíbula/diagnóstico por imagem , Mandíbula/fisiologia , Maxila/diagnóstico por imagem , Maxila/fisiologia , Titânio , Tomografia Computadorizada por Raios X
19.
Angle Orthod ; 82(5): 900-6, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22229824

RESUMO

OBJECTIVE: To determine if a new experimental resin-based material containing Portland cement (PC) can help prevent enamel caries while providing adequate shear bond strength (SBS). MATERIALS AND METHODS: Brackets were bonded to human premolars with experimental resin-based adhesive pastes composed of three weight rations of resin and PC powder (PC 30, 7:3; PC 50, 5:5; PC 70, 3:7; n  =  7). Self-etching primer (SEP) adhesive (Transbond Plus) and resin-modified glass ionomer cement (RMGIC) adhesive (Fuji Ortho FC Automix) were used for comparison. All of the bonded teeth were subjected to alternating immersion in demineralizing (pH 4.55) and remineralizing (pH 6.8) solutions for 14 days. The SBS for each sample was examined, and the Adhesive Remnant Index (ARI) score was calculated. The hardness and elastic modulus of the enamel were determined by a nanoindenter at 20 equidistant depths from the external surface at 100 µm from the bracket edge. Data were compared by one-way analysis of variance and a chi-square test. RESULTS: PC 50 and PC 70 showed significantly greater SBS than Fuji Ortho FC Automix, although Transbond Plus showed significantly greater SBS than other bonding systems. No significant difference in the ARI category was observed among the five groups. For specimens bonded with PC 50 and PC 70, the hardness and elastic modulus values in most locations were equivalent to those of Fuji Ortho FC Automix. CONCLUSIONS: Experimental resin-based bonding material containing PC provides adequate SBS and a caries-preventive effect equivalent to that of the RMGIC adhesive system.


Assuntos
Cariostáticos/administração & dosagem , Colagem Dentária/métodos , Esmalte Dentário/química , Cimentos de Resina/química , Resistência ao Cisalhamento , Análise de Variância , Cariostáticos/química , Cimentos Dentários/química , Análise do Estresse Dentário , Módulo de Elasticidade , Dureza , Humanos , Braquetes Ortodônticos/efeitos adversos , Propriedades de Superfície
20.
Angle Orthod ; 82(2): 187-95, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21827232

RESUMO

OBJECTIVE: To determine if the enamel around orthodontic brackets is significantly altered after demineralization followed by application of adhesives with and without fluoride-releasing ability. MATERIALS AND METHODS: One hundred eight noncarious human premolars were divided into six groups of 18 each and exposed to a demineralization solution. Stainless steel brackets were bonded using two conventional composite resin etch-and-rinse systems, three self-etching primer (SEP) composite resin systems, and one resin-modified glass ionomer cement (RMGIC) system. One conventional and one SEP composite resin adhesive did not have fluoride-releasing ability, which was claimed for the other four adhesives. The elastic modulus and hardness of the enamel were determined with a nanoindenter at 10 equidistant depths ranging from 1-46 µm and at four regions: control (not exposed) enamel surface, under the adhesive, and at 50 µm and 100 µm from the bracket edges. Using the Kruskal-Wallis and Mann-Whitney U-tests (P < .0125 for statistical significance), these properties were compared at different regions. RESULTS: The same behavior was observed for values of elastic modulus and hardness. Significant differences were found within approximately 21 µm of the enamel surface for etching with 35% phosphoric acid or priming with SEP, but only minimal changes occurred for the SEP adhesive. Increases in near-surface elastic modulus and hardness of enamel were found with the SEP adhesive and RMGIC with fluoride-releasing ability. CONCLUSIONS: Clinical use of the fluoride-releasing adhesives investigated may prevent demineralization of enamel around brackets during orthodontic treatment.


Assuntos
Colagem Dentária , Cimentos Dentários/química , Esmalte Dentário/patologia , Braquetes Ortodônticos , Condicionamento Ácido do Dente/métodos , Resinas Acrílicas/química , Silicatos de Alumínio/química , Fenômenos Biomecânicos , Cariostáticos/química , Resinas Compostas/química , Ligas Dentárias/química , Difusão , Módulo de Elasticidade , Fluoretos/química , Cimentos de Ionômeros de Vidro/química , Dureza , Humanos , Teste de Materiais , Ácidos Fosfóricos/química , Cimentos de Resina/química , Aço Inoxidável/química , Desmineralização do Dente/patologia
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