Modelo lineal vs. vectorial: estimación del movimiento mandibular y trabajo mecánico / Linear vs. vector model: estimation of mandible motion and mechanical work

Objetivo: Determinar los momentos de fuerza del haz superficial del masetero (SMH) obtenidos por modelos lineal y vectorial. Métodos: Investigación comparati-va in silico. Se obtuvo la fuerza del SMH con dinamó-metro en 12 pacientes varones adultos jóvenes para calcular el momento de la fuerza y trabajo mecánico a través de simulaciones en JAVA+ con NetBeans8.2. La descomposición de la fuerza fue F.cos α(x,y) y F.cos α(x,y,z) en el modelo lineal y vectorial respectivamen-te. Los momentos de fuerza fueron comparados por ANOVA (p<0,05). Resultados: La fuerza del SMH unila-teral obtenida con dinamómetro (2,5±0,1N) no difirió significativamente del modelo lineal (2,6±0,05N), pero difirió (p<0,001) del vectorial: 1,7, 2,2, 4,2N en x,y,z (general 2,7±0,02N). El momento medio de la fuerza en el modelo vectorial fue -17,9, -15,5, +14,3N.m-2, apuntando a la inclinación mandibular en el eje lateral en dirección caudal anterior, movimiento de inclina-ción en el eje lateral en la dirección cráneo-medial, e inclinación en el eje craneal en la dirección lateral-an-terior. El modelo lineal mostró momento de fuerza de 13,5N.m-2 apuntando un movimiento traslacional en dirección caudal-craneal en el eje anterior-posterior y menor trabajo mecánico del SMH (p=0,012). Con-clusión: Los modelos vectoriales son más eficientes proporcionando datos detallados para estimar los momentos de fuerza y el trabajo mecánico del SMH, y deben incluirse en los algoritmos de cálculo utilizados por dinamómetros (AU)

Objective: to determine the moments of force exerted by the superficial masseter head (SMH) obtained through linear models and vector ones. Methods: comparative in silico research. Data of SMH force obtained with dynamometer in 12 young adult male patients was used to calculate the moment of the force and mechanical work through simulations in JAVA+ performed with NetBeans8.2. Force decomposition was F.cos α(x,y) and F.cos α(x,y,z) in the linear and vector model respectively. The moments of force were compared by ANOVA (p<0.05). Results: Dynamometrical unilateral SMH force (2.5±0.1N) did not differ significantly from the linear model (2.6±0.05N), but differed (p<0.001) from the vector model: 1.7, 2.2, 4.2N on x,y,z (overall 2.7±0.02N). The mean moment of the force in the vector model was -17.9, -15.5, +14.3N.m-2, pointing to mandible's inclination on the lateral axis in anterior-caudal direction, inclination movement on the lateral axis in the cranio-medial direction and inclination on the cranial axis in the lateral-anterior direction. The linear model showed a moment of force of 13.5N.m-2 pointing to translational motion on caudal-cranial direction on the anterior-posterior axis and lower SMH mechanical work (p=0,012). Conclusion: Vector models are more efficient to provide detailed data to estimate the moments of force and mechanical work of SMH and should be included in the calculation algorithms used by dynamometers (AU)

Characterization of third molar morphometric variables.

The third molar is a tooth of anatomical, surgical, prosthetic and forensic dental interest. However, there is currently a lack of updated data regarding its morphology. The aim of this study was to determine the morphometric features of third molars and their predictive capability as regards dental arch and side. Two calibrated operators (ƙ = 0.83) determined the cervicalocclusalvestibular (COV), cervicalocclusalpalatal (COP) and occlusalapical (OA) distances, mesiodistal (MD), and vestibularpalatal (VP) diameters, number of roots (R) and number of cusps (C) of 961 cadaveric third molars, both upper (n = 462) and lower (n = 499), using a CONCOR 050 thin mandible caliper (resolution 0.01 mm). Median and range for each variable were calculated and compared using Mann Whitney nonparametric test (p < 0.05). Multivariate cluster analysis was used to determine the predictive capability of each variable for dental arch and side. For upper molars (UM), 50.6% were from the right side (RS) and 49.4% from the left side (LS), while for lower molars (LM), 60.9% were from the RS and 39.1% from the LS. No significant difference was found in the study variables in LM according to side. For UM, MD diameter (10.90 mm), COP(7.42 mm) distance and number of R (3) were significantly higher (p < 0.05) forRS, and number of C (3) was higher (p < 0.0001) for LS. They were also significant predictive grouping factors for side. For dental arch, OA (17.84 mm) and COV (7.60 mm) distances, MD (11.26 mm) diameter and the number of C (5) were significantly higher (p < 0.0001) for LM, while VP (10.84 mm) and COP (7.34 mm) distances, and the number of R (3) were significantly higher (p < 0.0001) for UM. These variables were significant predictive factors for dental arch. Despite the morphometric heterogeneity of third molars, there are intrinsic parameters with predictive capability for dental arch and side, but it would be advisable to supplement this study with data from topographic occlusal variables in order to validate their predictive capability.

El tercer molar es una pieza dentaria de interés odontológico anatómico, quirúrgico, endodóntico, protético y forense. Sin embargo, no hay disponibles hoy en día datos morfométricos actualizados del molar. El objetivo del trabajo fue determinar las características morfométricas de terceros molares y establecer el carácter predictivo de las mismas en cuanto a arco dental y lado. Dos operadores calibrados (ƙ = 0.83) determinaron la longitud oclusocervical vestibular (OCV) y palatina (OCP), oclusoapical (OA), diámetro mesiodistal (MD), diámetro vestíbulopalatino (VP), número de raíces (R) y número de cúspides (C), de 961 terceros molares cadavéricos, superiores (n = 462) e inferiores (n = 499), mediante el uso de un calibre de mandíbula fina CONCOR 050 (resolución 0.01 mm). Calculamos mediana y rango para cada variable y las comparamos haciendo uso de la prueba de Mann Whitney (p < 0.05). Utilizamos el análisis de cluster para determinar el valor predictivo de cada variable en cuanto a arco y lado. De los molares superiores (MS), 50.6% correspondió al lado derecho (LD) y 49.4% al lado izquierdo (LI). De los inferiores (MI), 60.9% correspondió al LD y 39.1% al LI. No hallamos diferencias significativas para las variables en estudio para los MI según su lado. Para los MS, el MD (10.90 mm), la OCP (7.42 mm) y el R (3) resultaron significativamente mayores (p < 0.05) para el LD, y el C (3), mayor (p < 0.0001) para el LI; y, además evidenciaron significancia como factores predictivos de agrupamiento para la predicción del lado. En relación al arco, la OA (17.84 mm), la OCV (7.60 mm), el MD (11.26 mm) y el C (5), resultaron significativamente mayores (p < 0.0001) en los MI, mientras que el VP (10.84 mm), la OCP (7.34 mm) y el R (3) fueron significativamente mayores (p < 0.0001) en MS. Dichas variables evidenciaron significan cia como factores predictivos para el arco. Pese a la heteroge neidad morfométrica del tercer molar, existen parámetros característicos con valor predictivo para el arco y lado, aunque sería recomendable complementar el estudio con variables topográficas oclusales a fin de validar la capacidad predictiva de los mismos.

Characterization of third molar morphometric variables

The third molar is a tooth of anatomical, surgical, prosthetic and forensic dental interest. However, there is currently a lack of updated data regarding its morphology. The aim of this study was to determine the morphometric features of third molars and their predictive capability as regards dental arch and side. Two calibrated operators (ƙ = 0.83) determined the cervicalocclusalvestibular (COV), cervicalocclusalpalatal (COP) and occlusalapical (OA) distances, mesiodistal (MD), and vestibularpalatal (VP) diameters, number of roots (R) and number of cusps (C) of 961 cadaveric third molars, both upper (n = 462) and lower (n = 499), using a CONCOR 050 thin mandible caliper (resolution 0.01 mm)...

El tercer molar es una pieza dentaria de interés odontológico anatómico, quirúrgico, endodóntico, protético y forense. Sin embargo, no hay disponibles hoy en día datos morfométricos actualizados del molar. El objetivo del trabajo fue determinar las características morfométricas de terceros molares y establecer el carácter predictivo de las mismas en cuanto a arco dental y lado. Dos operadores calibrados (ƙ = 0.83) determinaron la longitud oclusocervical vestibular (OCV) y palatina (OCP), oclusoapical (OA), diámetro mesiodistal (MD), diámetro vestíbulopalatino (VP), número de raíces (R) y número de cúspides (C), de 961 terceros molares cadavéricos, superiores (n = 462) e inferiores (n = 499), mediante el uso de un calibre de mandíbula fina CONCOR 050 (resolución 0.01 mm)...

Expression of sarcoplasmic-endoplasmic reticulum Ca-ATPase isoforms in masticatory muscles.

The aim of this study was to characterize the sarcoplasmic-endoplasmic reticulum Ca-ATPase (SERCA) isoforms in rabbit masticatory muscles compared with those in fast-twitch muscle. It was hypothesized that combined expression of the SERCA isoforms in fast- and slow-twitch muscles accounts for lower Ca-ATPase activity. SERCA was isolated by differential centrifugation, the isoforms were determined by ELISA, and the activity of each isoform was measured using a colorimetric method. Activity was tested for significance by anova, and the distribution of isoforms was assessed using the chi-square test (P < 0.05) and correlated to SERCA activity using Spearman's rank correlation. SERCA1 was predominant (90.5%) in fast-twitch muscle, whereas a mixture of SERCA isoforms was found in masticatory muscles: 62-78% was SERCA2, 20-37% was SERCA1, and the SERCA3 content was negligible. Depressor muscles showed a significantly higher content (77.8%) of SERCA2, and elevator muscles showed a higher content (35.4%) of SERCA1. Elevator muscles showed higher expression of SERCA2a (58%), and depressor muscles showed higher expression of SERCA2b (20%). The SERCA1 content was mainly SERCA1a and significantly higher for elevator muscles (33%), whereas depressor muscles showed a higher content of SERCA1b (4%). The SERCA1 content of fast-twitch muscle was mainly SERCA1a (88.5%). It is concluded that the mixture of different SERCA isoforms, along with a substantial content of SERCA2b, in masticatory muscles would support lower Ca-ATPase activity and calcium transport.