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OBJECTIVE: To compare the influence of four systems for dental bleaching on the shear bond strength (SBS) of orthodontic brackets. MATERIALS AND METHODS: One-hundred and fifty freshly extracted bovine teeth were randomly divided into five groups. In group I the teeth were untreated (control). In the remaining groups the teeth were bleached, as follows: group II: 38% hydrogen peroxide; group III: 10% carbamide peroxide; group IV: resin-based coating material (RBCM), Beauty Coat; and group V: RBCM, White Coat. In all groups the enamel was conditioned with a self-etching primer and brackets were bonded with composite resin. Samples were stored (37°C, 24 hours), tested, and statistically analyzed, with significance predetermined at P ≤ .05. The adhesive remnant index (ARI) was also evaluated and analyzed. RESULTS: The SBS of group V (22.49 ± 5.34 MPa) was significantly higher than that of all other groups (I: 17.1 ± 5.11 MPa; II: 14.72 ± 5.42 MPa; III: 12.04 ± 5.29 MPa; and IV: 18.23 ± 5.58 MPa). In contrast, the SBS of group III was significantly lower than that of all groups (except group II). Significant differences in the ARI scores were present between groups. CONCLUSIONS: The use of RBCM for dental bleaching before bonding orthodontic brackets did not reduce the SBS. In contrast, hydrogen and carbamide peroxides negatively affected the SBS. The SBS yielded after bleaching with carbamide peroxide was significantly lower.

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The purpose of this study was to establish cephalometric norms by age and gender of Harvold´s analysis for people living in the central region of Mexico and compare them with other populations to found morphologic craniofacial differences. One hundred sixteen males and 125 females were studied. The participants were divided into age groups. The parents and grandparents of the participants were born in Mexico. All participants had class I occlusion with normal growth, facial symmetry, no crowding and no previous orthodontic, orthopedic or maxillofacial surgery treatment. Lateral skull x-rays were obtained; each radiograph was analyzed on with a Harvold-like analysis. For statistical evaluation, the Student t´ test was used to compare the age groups between males and females. Significant gender differences were found in the following measurements: maxillary position, mandible position, and the anterior lower facial height in all age groups. Differences were found in the cranial and dental positions with other races respect to facial growth. Because every gender and race have their own characteristics, it is appropriate to use correct cephalometric norms in daily orthodontic practice. It is suggested to use the analysis of Harvold in a complementary way when in diagnosing a patient there is doubt on the alterations in the maxillae.

El propósito de este estudio fue establecer normas cefalométricas por edad y sexo de acuerdo al análisis de Harvold, para población de la región central de México y comparar estos patrones con otras poblaciones para encontrar diferencias en las características morfológicas craneofaciales. 116 hombres y 125 mujeres conformaron el estudio, divididos por grupos de edad. Los padres y abuelos de los participantes eran originarios de México. Todos los sujetos tenían clase I molar con un desarrollo normal, simetría facial, sin apiñamiento y sin previo tratamiento ortodóntico, ortopédico o cirugía maxilofacial. Se obtuvieron las radiografías laterales de cráneo; cada una se examinó de acuerdo al análisis cefalométrico de Harvold. Para el análisis estadístico, se aplicó la prueba t’ de Student para hacer la comparación entre grupos de edad y sexo. Se encontraron diferencias significativas entre hombres y mujeres en los siguientes parámetros: posición maxilar, posición mandibular y altura facial anteroinferior en todos los grupos de edad. Se demostraron diferencias en la posición dental y craneal con otras razas, respecto al crecimiento facial. Cada género y raza presenta sus características propias, por lo que es apropiado utilizar normas cefalométricas adecuadas en la práctica ortodóntica diaria. Se sugiere utilizar el análisis de Harvold como auxiliar o complemento cuando existe duda en el diagnóstico del paciente debido a alteraciones de los maxilares.

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Aim: The aim of this study was to determine the morphologic characteristics of the dental arches in the ethnic group “Mazahua” and mestizo teenagers from central Mexico. Methods: A sample of 80 Mazahua and 80 mestizo teenagers with normal occlusion, divided into two age groups, were evaluated. A digital caliper was used to measure in cast models the intercanine width, intermolar width, length and perimeter of the arch, occlusal intermaxillary curve (of Spee), overjet, and overbite. A comparative analysis with Student’s t-test was applied between gender and population groups. Results: Comparison of the dental arches between Mazahua and mestizo teenagers revealed that statistically significant differences existed with respect to most of the measurements. In most cases, they were greater in males; the Mazahua teenagers had intercanine and intermolar widths greater than mestizo teenagers. Conclusions: Each group has a characteristic dental arch form. The ethnic group Mazahua has squared arches, whereas the mestizo teenagers have oval arches, which give them their particular facial characteristics. These findings indicate that population-specific standards are necessary for clinical assessments.

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