Deflexión de agujas dentales 30G: comparación de cinco marcas comerciales / Deflection of dental needles 30G: comparison of five trademarks

Abstract Introducción: El grado o nivel de deflexión de la aguja dental, en la mayoría de los casos, puede determinar el éxito o fracaso en la técnica de anestesia dental. Objetivo: Medir el grado de deflexión de la aguja dental, comparando 5 diferentes marcas disponibles en la ciudad de Hermosillo, Sonora, México. Métodos: Se realizó un estudio experimental, en el que con ayuda de un modelo creado con un nivel profesional y una jeringa tipo cárpul, se realizaron diversas punciones en un trozo de carne de res, simulando la realización de una técnica lineal de anestesia bucodental. Se tomaron radiografías periapicales de cada una de las punciones, y con ayuda de una malla milimetrada, se realizaron las mediciones. Dentro de cada grupo de agujas, se presentaron diferentes medidas de deflexión, y se obtuvo un promedio de cada marca. El rango abarcó desde los .65 mm hasta 2.1 mm de deflexión, tomando como referencia un plano recto. Conclusiones: Se demostró que la de la marca Septodont®, fue la que presentó menor deflexión a la punción. Es recomendable verificar y examinar el estado de las agujas antes de ser utilizadas para realizar procesos quirúrgicos, y así disminuir riesgos y/o complicaciones postoperatorias.

Resumen Introduction: The degree or level of deflection of the dental needle, in most cases, can determine the success or failure of the dental anesthesia technique. Objective: Measure the degree of deflection of the dental needle, comparing 5 different brands available in the city of Hermosillo, Sonora, Mexico. Method: An experimental study was carried out, with a model created with a professional level and a carpul syringe, various punctures were made in a piece of beef, simulating the performance of a linear technique of oral anesthesia. Periapical radiographs of each of the punctures were taken, and with the help of a millimeter mesh, measurements were made. Within each group of needles, different deflection measures were presented, and an average of each brand was obtained. The range ranged from .65 mm to 2.1 mm of deflection, taking as reference a straight plane. Conclusions: It was shown that the Septodont® brand was the one that presented the lowest puncture deflection. It is advisable to verify and examine the condition of the needles before being used to perform surgical procedures, and thus reduce risks and / or postoperative complications.

Effect of the restorative technique on load-bearing capacity, cusp deflection, and stress distribution of endodontically-treated premolars with MOD restoration

OBJECTIVES: To evaluate the influence of the restorative technique on the mechanical response of endodontically-treated upper premolars with mesio-occluso-distal (MOD) cavity. MATERIALS AND METHODS: Forty-eight premolars received MOD preparation (4 groups, n = 12) with different restorative techniques: glass ionomer cement + composite resin (the GIC group), a metallic post + composite resin (the MP group), a fiberglass post + composite resin (the FGP group), or no endodontic treatment + restoration with composite resin (the CR group). Cusp strain and load-bearing capacity were evaluated. One-way analysis of variance and the Tukey test were used with α = 5%. Finite element analysis (FEA) was used to calculate displacement and tensile stress for the teeth and restorations. RESULTS: MP showed the highest cusp (p = 0.027) deflection (24.28 ± 5.09 µm/µm), followed by FGP (20.61 ± 5.05 µm/µm), CR (17.72 ± 6.32 µm/µm), and GIC (17.62 ± 7.00 µm/µm). For load-bearing, CR (38.89 ± 3.24 N) showed the highest, followed by GIC (37.51 ± 6.69 N), FGP (29.80 ± 10.03 N), and MP (18.41 ± 4.15 N) (p = 0.001) value. FEA showed similar behavior in the restorations in all groups, while MP showed the highest stress concentration in the tooth and post. CONCLUSIONS: There is no mechanical advantage in using intraradicular posts for endodontically-treated premolars requiring MOD restoration. Filling the pulp chamber with GIC and restoring the tooth with only CR showed the most promising results for cusp deflection, failure load, and stress distribution.

Heart rate deflection point as an alternative to determining the anaerobic threshold in dyslipidaemic patients

Aim: The aim of the present study was to verify the agreement between the ventilatory method (VT) and the alternative method of heart rate deflection point (HRDP) in determining the anaerobic threshold (AT) during incremental treadmill test in dyslipidaemic patients. Methods: Twenty-seven dyslipidaemic patients (61.50 ± 10.46 years) performed an incremental treadmill test, in which the AT was determined using both methods. Bland-Altman statistics was adopted in order to verify the agreement between the methods. Results: Agreement in AT determination between the VT and HRDP methods was observed (p < 0.05) for heart rate (138.00 ± 23.80 and 136.26 ± 22.18 bpm, respectively), oxygen uptake (31.00 ± 10.33 and 31.00 ± 11.17 ml.kg−1.min−1), and treadmill velocity (7.67 ± 1.71 km.h-1and 8.00 ± 1.75 km.h-1). Conclusion: Our results suggest that the HRDP method can be adopted for the determination of the AT in dyslipidaemic patients, showing agreement with the VT method.(AU)

Clinical study of prenatal ultrasonographic diagnosis for the fetal facial malformations by cerebral coro-nary view of nose tip deflection in the first and second trimester / 实用医学杂志

Objective To analyze the value of cerebral coronary view of nose tip deflection in screening fetal facial deformity in the first and second trimester. Methods All cases were divided into the 11～12+6 weeks, the 13 ～ 14+6 weeks and the 15 ～ 16+6 weeks undergone ultrasonographic examination on coronal view of nose tip deflection. The display of fetal facial structure and the detection rate of fetal facial malformation were analyzed. Results The fetal facial anatomic structures were clearly displayed. The median sagittal section ,eyes level coronal section ,retronasal triangle section ,or other sections were satisfactory in 4855 cases (97.10％). There was no Statistical difference in the display of fetal facial structures among the three groups. 69 fetus were found with facial malformations,including 31 fetus with facial malformations only,and 38 fetus combined with other abnormal struc-tures. The sensitivity,specificity,positive predictive value and negative predictive value were 93.24％,100％, 100％ and 99.90％ respectively. Conclusion The cerebral coronary view of nose tip deflection method has high detection rate and sensitivity,and is a reliable method for detecting fetal facial abnormalities in the first and second trimester.

Clinical study of prenatal ultrasonographic diagnosis for the fetal facial malformations by cerebral coro-nary view of nose tip deflection in the first and second trimester / 实用医学杂志

Objective To analyze the value of cerebral coronary view of nose tip deflection in screening fetal facial deformity in the first and second trimester. Methods All cases were divided into the 11～12+6 weeks, the 13 ～ 14+6 weeks and the 15 ～ 16+6 weeks undergone ultrasonographic examination on coronal view of nose tip deflection. The display of fetal facial structure and the detection rate of fetal facial malformation were analyzed. Results The fetal facial anatomic structures were clearly displayed. The median sagittal section ,eyes level coronal section ,retronasal triangle section ,or other sections were satisfactory in 4855 cases (97.10％). There was no Statistical difference in the display of fetal facial structures among the three groups. 69 fetus were found with facial malformations,including 31 fetus with facial malformations only,and 38 fetus combined with other abnormal struc-tures. The sensitivity,specificity,positive predictive value and negative predictive value were 93.24％,100％, 100％ and 99.90％ respectively. Conclusion The cerebral coronary view of nose tip deflection method has high detection rate and sensitivity,and is a reliable method for detecting fetal facial abnormalities in the first and second trimester.

Deflexión de agujas dentales 30G: comparación de cinco marcas comerciales

Introducción: El grado o nivel de deflexión de la aguja dental, en la mayoría de los casos, puede determinar el éxito o fracaso en la técnica de anestesia dental. Objetivo: Medir el grado de deflexión de la aguja dental, comparando 5 diferentes marcas disponibles en la ciudad de Hermosillo, Sonora, México. Métodos: Se realizó un estudio experimental, en el que con ayuda de un modelo creado con un nivel profesional y una jeringa tipo cárpul, se realizaron diversas punciones en un trozo de carne de res, simulando la realización de una técnica lineal de anestesia bucodental. Se tomaron radiografías periapicales de cada una de las punciones, y con ayuda de una malla milimetrada, se realizaron las mediciones. Dentro de cada grupo de agujas, se presentaron diferentes medidas de deflexión, y se obtuvo un promedio de cada marca. El rango abarcó desde los .65 mm hasta 2.1 mm de deflexión, tomando como referencia un plano recto. Conclusiones: Se demostró que la de la marca Septodont®, fue la que presentó menor deflexión a la punción. Es recomendable verificar y examinar el estado de las agujas antes de ser utilizadas para realizar procesos quirúrgicos, y así disminuir riesgos y/o complicaciones postoperatorias.

Introduction: The degree or level of deflection of the dental needle, in most cases, can determine the success or failure of the dental anesthesia technique. Objective: Measure the degree of deflection of the dental needle, comparing 5 different brands available in the city of Hermosillo, Sonora, Mexico. Method: An experimental study was carried out, with a model created with a professional level and a carpul syringe, various punctures were made in a piece of beef, simulating the performance of a linear technique of oral anesthesia. Periapical radiographs of each of the punctures were taken, and with the help of a millimeter mesh, measurements were made. Within each group of needles, different deflection measures were presented, and an average of each brand was obtained. The range ranged from .65 mm to 2.1 mm of deflection, taking as reference a straight plane. Conclusions: It was shown that the Septodont® brand was the one that presented the lowest puncture deflection. It is advisable to verify and examine the condition of the needles before being used to perform surgical procedures, and thus reduce risks and / or postoperative complications.

Needle deflection prediction based on projecting beam model / 医用生物力学

Objective To analyze deflection and forces of needle insertion and improve the inserting accuracy. Methods The measuring equipment was constructed with industrial camera, stepping motor and light source. The experiment of needle insertion into soft tissues was conducted with puncture needles having different diameters (1.3, 0.9, 0.6 mm), and the inserting forces at different puncture speeds (5, 10 and 15 mm/s) were measured by the force sensor. The needle deflection was obtained by digital image processing method. Based on the analysis of needle inserting forces, a projecting beam model was structured to predict the needle deflection. Results The deflections of puncture needles with diameters of 1.3 and 0.6 mm at puncture speed of 5 mm/s were predicted by using the projecting beam model. The absolute error was less than 0.5 mm, and the relative error was less than 10%. Conclusions The proposed model can predict the needle deflection effectively, which will provide references for the robot-assisted needle insertion.

Influencia de los cambios térmicos en la deflexión transversa de acrílicos para la base de dentaduras con y sin insertos metálicos / Influence exerted by thermal changes in the transverse deflection of acrylic materials used for denture bases, with and without metallic inserts

El propósito de este estudio in vitro fue determinar si los cambios térmicos influyen en la deflexión transversa de dos diferentes marcas de acrílico para la base de dentaduras con y sin insertos metálicos, después de ser sometidos a un periodo de termociclado con cambios de temperatura. Se elaboraron 40 muestras de acrílico de acuerdo con la especificación no. 12 de la ADA; y se conformaron cuatro grupos, dos de Lucitone 199 y dos de ProBase Hot. Los resultados se sometieron al análisis estadístico ANOVA de una vía y comparación de grupos Tukey con un valor de p < .001. Conclusión: Ambos acrílicos para la base de dentadura cumplen con las especificaciones de la norma no. 12 de la ADA. Los insertos metálicos permiten disminuir la deflexión de los acrílicos y los cambios térmicos afectan de manera considerable las propiedades físicas.

The aim of the present in vitro study was to determine whether thermal changes influence the transverse deflection of two different brands of acrylic used for denture bases, with and without metallic inserts, after having been subjected to a thermo-cycling period with temperature changes. 40 acrylic samples were processed according to ADA's specification number 12. Four groups were made up, two with Lucitone 199 and two with ProBase Hot. Results were subjected to one-way ANOVA statistical analysis and comparison of Turkey groups with a value of (p > .001). Conclusion: Both acrylic materials used for denture bases fulfill specifications of ADA's norm number 12. Metallic inserts allowed the decrease of the acrylic deflection and thermal changes considerably affected physical characteristics.

Deflexión transversa de materiales alternativos a base de polímeros para fabricación de base de dentadura / Transverse deflection of polymer-based alternative materials for the manufacturing of a denture base

En la actualidad se están desarrollando técnicas alternativas para la fabricación en tiempos cortos de prótesis totales en relación con la utilización de diferentes materiales para la base de dentadura. El propósito de este estudio fue comparar la deflexión transversa entre materiales a base de polímeros, propuestos como una alternativa a los materiales comúnmente utilizados para realizar una prótesis total en forma convencional. Se probaron resina acrílica termocurable, resina acrílica autocurable, láminas de acetato calibre 60 y 80 recubiertas con resina acrílica autocurable, resina acrílica fluida y resina fotopolimerizable para base de dentadura. Se fabricaron diez muestras de 65 x 10 x 2.5 mm de cada material. Las muestras se colocaron en agua a 37°C por 50 horas, se midió la deflexión transversa y se analizaron los resultados por análisis de varianza (ANOVA) de una vía. Los resultados mostraron que hubo diferencia estadísticamente significativa entre los grupos. Las láminas de acetato recubiertas con acrílico autocurable pueden ser una alternativa para la rápida fabricación de bases de dentadura de uso temporal.

Nowadays, alternative techniques are being developed for short-time manufacturing of full prostheses, entailing different materials for the denture base. The purpose of the present study was to compare transverse deflection among polymer-based materials currently proposed as an alternative to materials commonly used to conventionally manufacture a full prosthesis. For the denture base the following materials were tested: thermo-cured (setting) acrylic resin, self-cured acrylic resin, 60 and 80 gauge acetate sheets coated with self-cured acrylic resin, liquid (fluid) acrylic resin as well as light-cured resin. Ten 65 x 10 x 2.5 mm samples of each material were manufactured. The samples were placed in water at 37°C for 50 hours. Transverse deflection was measured and results were analyzed with the help of one-way analysis of variance (ANOVA). Results exhibited statistically significant differences among groups. Acetate sheets coated with self-cured acrylic could represent an alternative for the rapid manufacturing of temporary denture basis.

Transformation Behaviour, Bending Properties and Surface Quality of 22 Commercial Nickel- Titanium Wires: A Batch-to-Batch Evaluation.

Aims: The aims of this study were to investigate batch-to-batch differences in mechanical and thermal properties of 22 commercial nickel-titanium wires and evaluate the surface quality. Secondly the percentages of superelasticity at mouth temperature were measured. Study Design: In vitro laboratory study. Place and Duration of Study: Sample: Department of Oral Health Sciences – Orthodontics and Metallurgy and Materials Engineering KU Leuven, between January 2010 and May 2011. Methodology: The sample comprised 22 NiTi wires of the upper jaw from 7 different manufacturers. For each brand two different batches were investigated (LOT A, LOT B). Three different investigations were carried out. First transformation behaviour and transition temperatures were determined by differential scanning calorimetry, second a three point bending test was done to evaluate the mechanical properties and third scanning electron microscopy was performed on all samples to evaluate surface quality. Results: Absolute batch-to-batch differences in the investigated properties were all deviating from zero, although most differences were clinically acceptable. Significant interbatch differences in thermal properties were found in 4 wires. Mechanical interbatch differences were found remarkable for 5 wires. Percentage of elasticity showed a non- superelastic curve below a deflection of 1500 μm, which represents clinical small deflections. Surface topography showed also interbatch differences for 4 wires. Conclusion: This study shows that batch-to-batch differences are obvious in each sample. One has to be careful in the selection of archwires. Therefore more standardized consument information should be provided.

Effect of fluoride mouth rinses on various orthodontic archwire alloys tested by modified bending test: An in vitro study.

Objective: Fluorides can cause corrosion and degradation in mechanical properties of commonly used archwires by forming hydrofluoric acid HF and causing disruption of protective titanium oxide layer. Hence, the aim of this study was to assess the change in load deflection characteristics of Ni-Ti, Cu Ni-Ti, S.S, and β-Ti wires on immersing in fluoride mouth rinses of two types- Phosflur and neutral NaF mouth rinse utilizing a modified bending test and comparing it to control. Materials and Methods: Round preformed wires were immersed in 10 ml of control and test solution (Phosflur and S-Flo mouth rinse) for 1.5 hours and incubated at 37°C. Modified bending test was carried out to evaluate load-deflection characteristics of different wires using Instron. Analysis of variance (ANOVA) was applied to determine if statistically significant difference exist among the mean load values obtained at various deflections in control and test solutions. Results: There was no statistically significant reduction in load deflection characteristics of Ni-Ti, copper Ni-Ti, β-Ti, and S.S wires on immersing in Phosflur mouth rinse and neutral sodium fluoride mouth rinses as compared to control at 2.5 and 1 mm of deflection in unloading phase. Conclusion: Phosflur and a neutral sodium fluoride mouth rinse did not affect the mechanical bending properties of Ni-Ti, copper Ni-Ti, B-Ti, and SS wires in in vitro conditions.

A Comparative Evaluation of Effects of Different Kinds of Sterilizations On Load Deflection Characteristics, Tensile Properties of Copper NITI Wire- AN Invitro Study.

Copper NiTi wires were introduced by Sachdeva R and Miyasaki S in 1994. This latest innovation in the evolutionary scale gives us the opportunity of choosing the force level by choosing the temperature at which the wires will deliver its optimum force level. With so many advantages and their ability to return to their original form coupled with the high cost of copper NiTi many clinicians started reusing the wire. This raises concern about disinfecting/sterilizing the wire before using in another patient for prevention of cross infection. Hence, various sterilization procedures like cold sterilization using 2% acidic glutaraldehyde, dry heat sterilization and autoclaving were used to prevent this cross infection..Aim: The main aim of this study is used to evaluate the effects of different kinds of sterilization on load characteristics and tensile properties of copper Ni Ti wire. Materials and Methods: In the present study, selected mechanical properties like load deflection characteristics, ultimate tensile strength of the 0.016 copper NiTi wires were studied before and after sterilization procedure. Three point bending test was performed to evaluate the load deflection characteristics and tensile test were evaluated to determine other mechanical properties. Pretreatment and post treatment values were statistically analyzed by one way ANOVA test. Results: On the load deflection characteristics, even though there was an increase in the loading and unloading forces, statistically significant changes in the forces are seen only when the wires were subjected to two cycles of sterilization with autoclave and dry heat. No detrimental changes were detected in tensile properties of copper NiTi were after single cycle of sterilization with any of the stated sterilants. Very minimal non significant changes occurred during the second cycle of sterilization procedure. Conclusion: Pronounced changes in load deflection characteristics have been found in the wires which have undergone two cycles of sterilization with either dry heat or autoclave implying that there was loss in pseudoplastic and pseudoelastic properties of wires and increase in stiffness of wires.

Mechanical properties of denture base resins: An evaluation.

Background: Acrylic resin dentures are susceptible to fracture after clinical use, which is a problem of concern in prosthodontics. Impact failure outside the mouth and flexure fatigue failure in the mouth are two most important causes of fracture of denture base. Aim: This study evaluated the transverse deflection and transverse strength of four commercial brands of heat cure acrylic resin (Stellon, Acrylin-H, Trevalon and Trevalon-HI). Materials and Methods: An experimental design was adapted. Twenty-four rectangular strip specimens, six for each group, were prepared. Strips were finished on the edges and equally from the both the molded surfaces to make strips of specific dimensions. The tests were conducted mainly in accordance with the American Dental Association Specification no. 12/ISO: 1567-1981 (ISO: 6887-1986) for denture base polymer. The transverse deflection and transverse strength were measured by Instron testing machine. Intergroup differences were assessed using student "t" test. Results: The heat cure denture base material D (Trevalon "HI") had the minimum mean value of transverse deflection under different loads. Trevalon "HI" also had minimum value of mean transverse strength among different brands of acrylic resins. There was no statistically significant variation between Stellon, Acrylin-H and Trevalon, but variation was significantly higher with D (Trevalon "HI") vs. Stellon, Acrylin-H and Trevalon. Conclusion: The heat cure denture base material D (Trevalon "HI") was the strongest and C (Trevalon) was the weakest among all materials used in this study. The study showed that the deflection of various denture base resins (A to D) increases proportionately with the increase in load.

EFFECT OF EXERCISE TRAINING ON THE HEART RATE PERFORMANCE CURVE IN PATIENTS WITH CARDIOVASCULAR DISEASE / 体力科学

Left-ventricular dysfunction is diagnosed when the heart rate performance curve (HRPC) of patients deflects upwards during incremental exercise. The aim of this study was to investigate the effect of exercise training on the upward deflection of the HRPC in patients with cardiovascular disease.This study comprised 11 patients who had cardiovascular disease and showed an upward deflection of the HRPC. The patients underwent exercise training (aerobic training, AT intensity: 30-40 minutes, 2-3 sessions/week, and 3-month follow-up). The HRPC of the patients was measured before and after exercise training. We used a method described by Pokan for evaluating the HRPC; the performance curve (PC) index ([PC1 - PC2] × [1 + PC1 × PC2]^-1) was calculated from PC1 and PC2. PC1 and PC2 refer to the heart rate response before and after the O₂ pulse deflection point, respectively. The PC index indicates the following: PC > 0.1, downward deflection; -0.1 ≤ PC ≤ 0.1, linear time course; PC < -0.1, upward deflection.The PC index significantly increased after exercise training (from -0.22 ± 0.09 to -0.14 ± 0.07; p < 0.05). In addition, the HRPC of 4 patients (37%) changed in linear time course.These results suggest that an upward deflection of the HRPC in patients with cardiovascular disease may shift to a linear time course after exercise training.

Load-deflection characteristics and plastic deformation of NiTi closed coil springs / 대한치과교정학회지

OBJECTIVE: NiTi closed coil springs were reported to have relatively constant unloading forces. However, the characteristics of NiTi closed coil springs from various manufacturers have not been elucidated. The purpose of this study was to compare load-deflection characteristics of various NiTi closed coil springs and to find out the optimal range of extension. METHODS: Seven kinds of NiTi closed coil springs from five manufacturers were tested. Load deflection curves were obtained at extension ranges from 2 mm to 30 mm. Also, springs were kept extended during a 4 week period, and then load deflection curves were obtained again. RESULTS: Sentalloy (Tomy) and Jinsung blue (Jinsung) showed superelasticity in every extension ranges tested and showed plastic deformation of less than 1 mm. Ni-Ti (Ormco) showed superelasticity only after the springs were extended at or more than 10 mm, thereby meaning that clinicians should extend these springs at or more than 10 mm to utilize the superelasticity. Orthonol (RMO) and Nitanium (Ortho Organizers) did not show superelasticity. After 4 weeks of extension, all springs showed plastic deformation less than 1 mm when the extension was at or under 25 mm. CONCLUSIONS: The superelastic behavior of NiTi closed springs were different among various NiTi spring products, and some NiTi closed springs failed to show superelasticity.

Effect of intermittent polymerization on the rate of polymerization shrinkage and cuspal deflection in composite resin / 대한치과보존학회지

This study investigated the effect of intermittent polymerization on the rate of polymerization shrinkage and cuspal deflection in composite resins. The linear polymerization shrinkage of each composite was measured using the custom-made linometer along with the light shutter specially devised to block the light at the previously determined interval. Samples were divided into 4 groups by light curing method; Group 1) continuous light (60s with light on); Group 2) intermittent light (cycles of 3s with 2s light on & 1s with light off for 90s); Group 3) intermittent light (cycles of 2s with 1s light on & 1s with light off for 120s); Group 4) intermittent light (cycles of 3s with 1s light on & 2s with light off for 180s). The amount of linear polymerization shrinkage was measured and its maximum rate (Rmax) and peak time (PT) in the first 15 seconds were calculated. For the measurement of cuspal deflection of teeth, MOD cavities were prepared in 10 extracted maxillary premolars. Reduction in the intercuspal distance was measured by the custom-made cuspal deflection measuring machine. ANOVA analysis was used for the comparison of the light curing groups and t-test was used to determine significant difference between the composite resins. Pyramid showed the greater amount of polymerization shrinkage than Heliomolar (p < 0.05). There was no significant difference in the linear polymerization shrinkage among the groups. The Rmax was group 4 < 3, 2 < 1 in Heliomolar and group 3 < 4 < 2, 1 in Pyramid (p < 0.05). Pyramid demonstrated greater cuspal deflection than Heliomolar. The cuspal deflection in Heliomolar was group 4 < 3 < 2, 1 and group 4, 3 < 2, 1 in Pyramid (p < 0.05). It was concluded that the reduced rate of polymerization shrinkage by intermittent polymerization can help to decrease the cuspal deflection.

Cuspal deflection in class V cavities restored with composite resins / 대한치과보존학회지

The purpose of this study was to evaluate the effect of the polymerization shrinkage and modulus of elasticity of composites on the cusp deflection of class V restoration in premolars. The sixteen extracted upper premolars were divided into 2 groups with similar size. The amounts of cuspal deflection were measured in Class V cavities restored with a flowable composite (Filtek flow) or a universal hybrid composite (Z-250). The bonded interfaces of the sectioned specimens were observed using a scanning electron microscopy (SEM). The polymerization shrinkage and modulus of elasticity of the composites were measured to find out the effect of physical properties of composite resins on the cuspal deflection. The results were as follows. 1. The amounts of cuspal deflection restored with Filtek flow or Z-250 were 2.18 +/- 0.92 microm and 2.95 +/- 1.13 microm, respectively. Filtek flow showed less cuspal deflection but there was no statistically significant difference (p > 0.05). 2. The two specimens in each group showed gap at the inner portion of the cavity. 3. The polymerization shrinkages of Filtek flow and Z-250 were 4.41% and 2.23% respectively, and the flexural modulus of elasticity of cured Filtek flow (7.77 GPa) was much lower than that of Z-250 (17.43 GPa). 4. The cuspal deflection depends not only on the polymerization shrinkage but also on the modulus of elasticity of composites.

Effects of heat treatment on the load-deflection properties of nickel-titanium wire / 대한치과교정학회지

OBJECTIVE: Nickel-titanium alloy wire possesses excellent spring-back properties, shape memory and super-elasticity. In order to adapt this wire to clinical use, it is necessary to bend as well as to control its super-elastic force. The purpose of this study is to evaluate the effects of heat treatment on the load-deflection properties and transitional temperature range (TTR) of nickel-titanium wires. METHODS: Nickel-titanium wires of different diameters (0.016" x 0.022", 0.018" x 0.025" and 0.0215" x 0.028") were used. The samples were divided into 4 groups as follows: group 1 , posterior segment of archwire (24 mm) without heat treatment; group 2, posterior segment of archwire (24 mm) with heat treatment only; group 3, anterior segment with bending and heat treatment; group 4, anterior segment with bending and 1 sec over heat treatment. Three point bending test was used to evaluate the change in load-deflection curve and obtained DSC (different scanning calorimetry) to check changes in Af temperature. RESULTS: In the three point bending test, nickel-titanium wires with heat treatment only had higher load-deflection curve and loading and unloading plateau than nickel-titanium wires without heat treatment. Nickel-titanium wires with heat treatment had lower Af temperature than nickel-titanium wires without heat treatment. Nickel-titanium wires with heat treatment and bending had higher load-deflection curve than nickel-titanium wires with heat treatment and nickel-titanium wires without heat treatment. Nickel-titanium with heat treatment of over 1 sec and bending had the highest load-deflection curve. Nickel-titanium wires with heat treatment and bending had lower Af temperature, Nickel-titanium wires with heat treatment of over 1 sec and bending had the lowest Af temperature. CONCLUSION: From the results of this study, it can be stated that heat treatment for bending of Nickel-titanium wires does not deprive the superelastic property but can cause increased force magnitude due to a higher load-deflection curve.

Correlation between Linear polymerization shrinkage & tooth cuspal deflection / 대한치과보존학회지

The purpose of the present study was to evaluate the relationship between the amount of cuspal deflection and linear polymerization shrinkage in resin composite and polyacid modified resin composite. For cuspal defelction and shrinkage measurement, Dyract AP, Compoglass F, Z100, Surefil, Pyramid, Synergy Compact, Heliomolar and Heliomolar HB were used. For measuring polymerization shrinkage, a custom made linometer (R&B, Daejon, Korea) was used. The amount of shrinkage among materials was compared using One-way ANOVA analysis and Tukey's test at the 95% of confidence level. For measuring cuspal deflection of teeth, standardized MOD cavities were prepared in extracted maxillary premolars. After a self-etching adhesive was applied, cavities were bulk filled with one of the filling materials.Fifteen teeth were used for each material. Cuspal deflection was measured by a custom made cuspal-deflection measuring device. One-way ANOVA analysis and Tukey's test were used to determine differences between the materials at the 95% of confidence level. Correlation of polymerization shrinkage and cuspal deflection were analyzed by regression analysis. The amount of polymerization shrinkage from least to greatest was Heliomolar, Surefil < Heliomolar HB < Z100, Synergy Compact < Dyract AP < Pyramid, Compoglass F (p < 0.05). The amount of cuspal deflection from least to greatest was Z100, Heliomolar, Heliomolar HB, Synergy Compact Surefil < Compoglass F < Pyramid, Dyract AP (p < 0.05). The amount of polymerization shrinkage and cuspal deflection showed a correlation (p < 0.001).

Measurements of shrinkage stress and reduction of inter-cuspal distance in maxillary premolars resulting from polymerization of composites and compomers / 대한치과보존학회지

The purpose of present study was to evaluate the polymerization shrinkage stress and cuspal deflection in maxillary premolars resulting from polymerization shrinkage of composites and compomers. Composites and compomers which were used in this study were as follows: Dyract AP, Z100, Surefil, Pyramid, Synergy Compact, Heliomolar, Heliomolar HB, and Compoglass F. For measuring of polymerization shrinkage stress, Stress measuring machine (R&B, Daejon, Korea) was used. One-way ANOVA analysis with Duncan's multiple comparison test were used to determine significant differences between the materials. For measuring of cuspal deflection of tooth, MOD cavities were prepared in 10 extracted maxillary premolars. And reduction of intercuspal distance was measured by strain measuring machine (R&B, Daejon, Korea) One-way ANOVA analysis with Turkey test were used to determine significant differences between the materials. Polymerization shrinkage stress is [Heliomolar, Z100, Pyramid 0.05).