ABSTRACT
Objetivo: El objetivo de este estudio fue medir el cambio dimensional de una silicona por condensación a través de diferentes instrumentos de medición (calibrador digital, estereomicroscopio y máquina de medición por coordenadas tridimensional) en cuatro diferentes tiempos. Métodos: En el estudio experimental in vitro se realizaron cuatro impresiones con silicona por condensación (Speedex) con un dispositivo específico con cuatro distancias, con un total de 16 mediciones llevadas a cabo con cada instrumento. Los tiempos predeterminados de medición fueron: inmediatamente después de la im-presión (T0), después de 30 minutos (T1), 1 h (T2) y 7 días (T3) de la impresión. Las medias y desviaciones estándar de las mediciones se analizaron con prueba de varianza y la prueba de Tukey, con un nivel de significancia de 0,05. Resultados: La media (mm) para las muestras medidas con el calibrador digital (T0= 5,82; T1 y T2= 5,8; T3= 5,78) y la máquina de medición por coordenadas tridimensional (T0= 5,75; T1= 5,78; T2 y T3= 5,77), presentaron diferencia estadísticamente significativa de la dimensión de los valores iniciales para los valores después de 7 días (p = 0,037; p = 0,013, respectivamente), la misma no se dio para el uso del estereomicroscopio (T0, T1 y T3= 5,83; y T2 = 5,81), que presentó similitud estadística en todos los tiempos (p = 0,754). Conclusiones: El método de medición fue el factor relevante que influenció en los resultados de las di-mensiones de las impresiones, los cuatro tiempos no fueron relevantes en los cambios dimensionales de la silicona de condensación analizada. Palabras clave: Elastómeros de silicona; Materiales dentales; Precisión de la medición dimensional.
Objective: This study aims to calculate the dimensional change of a condensation sili-cone through different measuring instruments (digital paquimeter, stereomicroscope and 3D coordinate measuring machine); in four separate times. Methods: In the experimen-tal in vitro study four impressions of condensation silicone (Speedex) were performed with a specific device with four-time distances, resulting in sixteen measurements with each instrument. The pre-determinated times for measurement were: immediately after the impression (T0), after 30 min (T1), after 1 h (T2) and after 7 days (T3) of impres-sion. The averages and standard deviations of measurements were submitted to analysis of variance and Tukey's test, with significance level of 0.05. Results: The average (mm) for the samples measured with a digital paquimeter (T0= 5.82; T1 y T2= 5.80; T3= 5.78) and 3D coordinate measuring machine (T0= 5.75; T1=5.78; T2 y T3 = 5.77), there was a significant differ-ence of dimension for the initial values in relation of values after 7 days (p = 0.037; p = 0.013, respec-tively), the same did not happen for the use of the stereomicroscope (T0, T1 y T3= 5.83; y T2= 5.81), that presented statistic similarity for all evaluated times (p = 0.754). Conclusions: The measurement method was the relevant factor that influenced the results of the dimensions of the impressions, the four times were not relevant in the dimensional changes of the silicon of condensation analyzed. Keywords: Dental materials; Dimensional measurement accuracy; Silicone elastomers.
ABSTRACT
OBJECTIVE: To evaluate the position of the mandibular first permanent molar in the mandible relative to several factors. MATERIALS AND METHODS: A total of 185 untreated Class I and Class II patients were randomly selected from a sample of 350 patients from a single office. The palatal and mandibular planes were related to Frankfort horizontal to create the interjaw or "B" angle. Age and the mesial contact of the mandibular first molars were used. The landmarks were projected at right angles to the Frankfort horizontal for effective mandibular dimension lengths. Actual-length dimensions were projected at right angles to the mandibular plane. Pearson product moment correlation coefficients were computed to evaluate the effect of age, cranial length, and mandibular contribution to the molar's sagittal position in the mandible. Significance was reported only when P < .05 to determine a 95% confidence level. RESULTS: Statistically significant positive correlations indicated that the mandibular molar is located more forward with increasing age, longer mandibular body length, and increasing posterior facial height. In contrast, significant negative correlations to the interjaw, mandibular plane, ramal inclination angles, and the linear ramal contribution corresponded to a more posterior position of the molar with increasing angles. CONCLUSIONS: The mandibular first permanent molar is located more anteriorly with an older patient, a longer mandibular body, greater posterior facial height, and an acute interjaw angle. In contrast, an increase in the forward tip of the ramus places the molar in a more posterior location.
