RESUMEN
Light emitting diode (LED) light-curing units have recently been used to polymerize resin-based orthodontic adhesives, and preliminary studies indicate their use has been successful. The purpose of this study was to evaluate the relationship between the shear bond strength of orthodontic brackets bonded to enamel and the duration of photopolymerization with LEDs and conventional quartz-tungsten-halogen light-curing units. Three LED light-curing units (GC e-light, GC America, Alsip, Ill; Elipar FreeLight, 3M ESPE Dental Products, St Paul, Minn; and UltraLume LED 2, Ultradent Products, South Jordan, Utah) and 1 halogen-based light-curing unit (Ortholux XT, 3M Unitek, Monrovia, Calif) were evaluated. Two hundred forty metal orthodontic brackets were bonded to extracted molars. Specimens were divided into 12 groups of 20 teeth each. Each group was cured with a different light-curing unit for 40, 20, or 10 seconds. The specimens were stored in water at 37 degrees C for 24 hours and then subjected to a shear force with a universal testing machine until bracket failure. Two-way ANOVA detected significantly weaker mean shear bond strength with the GC e-light at 10 and 40 seconds (P<.001) and higher mean shear bond strength for the UltraLume LED 2 at 40 seconds (P<.001). All experimental groups had laboratory mean shear bond strengths greater than 8 MPa, even with a 10-second cure.
Asunto(s)
Recubrimiento Dental Adhesivo/instrumentación , Iluminación/instrumentación , Soportes Ortodóncicos , Análisis de Varianza , Aleaciones Dentales/química , Esmalte Dental/ultraestructura , Análisis del Estrés Dental/instrumentación , Electrónica/instrumentación , Diseño de Equipo , Falla de Equipo , Humanos , Ensayo de Materiales , Polímeros/química , Cementos de Resina/química , Resistencia al Corte , Temperatura , Factores de Tiempo , Agua/químicaRESUMEN
To reduce the number of steps involved with bonding procedures, manufacturers have simplified adhesive systems by combining the hydrophilic primer and the adhesive, or by combining the etchant, the primer, and the adhesive into 1 bottle and application. The purpose of this study was to investigate the relationship between the shear bond strength of orthodontic brackets to enamel, with or without fluoride varnish, by using either conventional or self-etching primer systems. Forty-eight extracted teeth were divided into 4 groups of 12 teeth each: group 1, fluoride varnish, conventional adhesive; group 2, fluoride varnish, self-etching primer system; group 3, no fluoride varnish, conventional adhesive; and group 4, no fluoride varnish, self-etching primer system. The bonding procedure followed the manufacturers' recommendations for the materials. Precoated adhesive orthodontic brackets were light-cured to the facial surfaces of the teeth and stored in whole human saliva at 37 degrees C for 24 hours. The specimens were subjected to a shear force in a testing machine until failure. The adhesive remnant index was used to score the teeth. Data were analyzed with a 2-way analysis of variance to test for differences in shear bond strength with respect to fluoride varnish and type of adhesive system used. The results showed no difference in bond strength among any of the experimental groups. Similarly, chi-square analysis determined that adhesive remnant index scores were not statistically different. The application of fluoride varnish does not affect the bond strength of orthodontic brackets to enamel with conventional or self-etching primer systems.
Asunto(s)
Cariostáticos/química , Recubrimiento Dental Adhesivo , Fluoruros/química , Soportes Ortodóncicos , Cementos de Resina/química , Análisis de Varianza , Distribución de Chi-Cuadrado , Esmalte Dental/ultraestructura , Falla de Equipo , Humanos , Ensayo de Materiales , Saliva/química , Resistencia al Corte , Temperatura , Factores de TiempoRESUMEN
The purpose of this study was to compare the shear bond strength of orthodontic brackets bonded to teeth with either an indirect bonding technique and a new adhesive resin or a direct bonding technique and a light-activated adhesive. Fifty-four extracted premolars were mounted in acrylic blocks and randomly divided into 2 groups (n = 27). In one group, orthodontic brackets were bonded to premolars with an indirect bonding adhesive system; in the other, brackets were bonded with the direct method. Seventy-two hours later, the brackets were placed in a testing machine and subjected to a shear force with a crosshead speed of 1 mm/minute. The mean shear bond strengths for the indirect and direct groups were 11.2 and 10.9 MPa, respectively, both exceeding the minimum shear bond strength range of 5.9 to 7.8 MPa often cited in the literature for clinical success. Data were analyzed with Student t tests. No significant difference in shear bond strength between the 2 groups was detected (P =.76). Resin remnants on orthodontic bracket pads were observed with a dissecting microscope at 30x magnification and scored with a modified adhesive remnant index. There was no significant difference between groups (P >.05). There was also no correlation between shear bond strength and the percentage of adhesive resin remnants left on the orthodontic bracket. Under the conditions of this study, no evidence suggests a difference in shear bond strength of orthodontic brackets bonded to tooth enamel, whether they are bonded with the direct or indirect technique.
Asunto(s)
Recubrimiento Dental Adhesivo/métodos , Soportes Ortodóncicos , Cementos de Resina , Análisis del Estrés Dental , Humanos , Ensayo de Materiales , Resistencia al CorteRESUMEN
When bonding orthodontic brackets to enamel, most orthodontists use a conventional technique of etching tooth enamel with phosphoric acid, placing a hydrophilic primer on the etched, rinsed, and dried surface, then bonding the bracket with an adhesive resin composite. New systems simultaneously etch and prime the tooth surface in preparation for bonding. The purpose of this study was to compare the shear bond strength of orthodontic brackets bonded to enamel with a conventional, multistep adhesive system and a self-etching primer adhesive system. In addition, a third group was included in which the air dispersion step in the self-etching primer system was omitted. Brackets were bonded to 108 extracted human molars according to 1 of 3 experimental protocols--group 1: conventional multistep adhesive (n = 36); group 2: self-etching primer system (n = 36); group 3: self-etching primer system without air dispersion (n = 36). Specimens were loaded to failure in a universal testing machine (Instron, Canton, Mass). Mean shear bond strengths in megapascals (standard deviation) were 11.3 (2.2), 11.9 (3.2), and 8.2 (2.8) for groups 1, 2, and 3, respectively. Data were subjected to 1-way analysis of variance at alpha =.05. The mean shear bond strength of the self-etching primer group in which the air dispersion step was omitted was significantly less than in the other 2 groups (P <.001). However, there was no difference in mean shear bond strength between the conventional, multistep adhesive system and the self-etching primer system when the primer was dispersed correctly (P =.34).
Asunto(s)
Recubrimiento Dental Adhesivo/métodos , Soportes Ortodóncicos , Cementos de Resina , Grabado Ácido Dental , Aire , Análisis de Varianza , Análisis del Estrés Dental , Humanos , Diente Molar , Ácidos Fosfóricos , Resistencia al CorteRESUMEN
Commercially available light-emitting diode (LED) light-curing units recently have been introduced to the dental products market. No published studies have evaluated the adequacy of cure of commercially available LEDs. The purpose of this study was to compare the shear bond strength of orthodontic brackets bonded to teeth with conventional halogen-based light-curing units and commercially available LED curing units. Two LED light-curing units (LumaCure and VersaLux) and 2 halogen-based light-curing units (Optilux 501 and ProLite) were tested. One hundred standard metal orthodontic brackets were bonded to extracted human third molars with a light-cured adhesive system. The specimens were divided into 4 groups of 25 teeth each. In each group, the brackets were cured for 40 seconds with a different light-curing unit. The specimens were stored in water at 37 degrees C for 24 hours and then tested in shear with an Instron universal testing machine at a crosshead speed of 1 mm/min until the brackets debonded. One-way analysis of variance detected no differences in bond strength between the 4 groups (P =.78). Chi-square analysis detected no difference in the adhesive remnant index scores of the 4 groups (P =.89). Under the conditions of this study, the LED light-curing units bonded brackets to etched tooth enamel as well as the halogen-based light-curing units. Additional clinical studies are necessary before routine use of commercial LED light-curing units can be recommended.
Asunto(s)
Iluminación/instrumentación , Cementos de Resina/química , Grabado Ácido Dental , Resinas Acrílicas/química , Análisis de Varianza , Bisfenol A Glicidil Metacrilato/química , Distribución de Chi-Cuadrado , Aleaciones Dentales/química , Recubrimiento Dental Adhesivo , Esmalte Dental/ultraestructura , Análisis del Estrés Dental/instrumentación , Electrónica/instrumentación , Diseño de Equipo , Halógenos , Humanos , Soportes Ortodóncicos , Polímeros/química , Estadística como Asunto , Estrés Mecánico , Propiedades de Superficie , Temperatura , Factores de Tiempo , Agua/químicaRESUMEN
The purpose of this study was to compare the wear of orthodontic ligature-cutting pliers after multiple cycles of cutting stainless steel ligature wire (.025 mm) and sterilizing with dry heat or steam autoclave. Fifty ligature-cutting pliers with stainless steel inserts were randomly divided into 2 equal groups to be sterilized in either dry heat or steam autoclave. Each plier was subjected to a series of ligature wire cuts followed by the assigned sterilization method. The amount of wear at the tip of each plier in both groups was measured with a stereo microscope system and digital photomicrography. Wear was defined as the difference in initial length from a marked reference line to the tip of the plier minus the length after 6 and 12 cycles of use and sterilization. There was no significant difference in the mean wear at the tip of the pliers between the 2 groups. It appears that there is no need to maintain both sterilization systems, dry heat and steam autoclave, in the orthodontic office. Steam autoclave sterilization can be used with no deleterious effects on the pliers if they are manufactured with stainless steel inserts.