Comparison of clinical and electromyographic rest vertical dimensions in dolichofacial and brachyfacial young adults: A cross-sectional study.

STATEMENT OF PROBLEM: Therapeutic procedures that increase occlusal vertical dimension (OVD) may have different responses in patients with different craniofacial vertical patterns. The effect on these patients of increasing their OVD is not well understood. PURPOSE: The purpose of this clinical study was to compare measurements of vertical jaw separation (VJS) in patients with brachyfacial and dolichofacial craniofacial patterns in 2 vertical dimensions: the clinical rest/postural vertical dimension (CR/PVD) and electromyographic rest vertical dimension (EMGRVD). MATERIAL AND METHODS: Sixty healthy dental students were selected at random after a lateral skull radiograph was made. The Ricketts (VERT index) analysis was used to determine 30 brachyfacial (G1) and 30 dolichofacial (G2) types. The VJS was measured for G1 and G2 types in the 2 rest vertical dimensions specified. CR/PVD was recorded using 2 methods: swallowing (CR/PVD-P1) and the phonetic breathing method (CR/PVD-P2). The Shapiro-Wilk test was used for data distribution, and the Mann-Whitney U test was used to accept or reject the null hypothesis (α=.05). RESULTS: Mean VJS in CR/PVD-P1 was 1.92 ±1.14 mm for the brachyfacial and 1.36 ±0.58 mm for the dolichofacial facial group (P=.05). The mean VJS in CR/PVD-P2 was 1.89 ±1.17 mm for the brachyfacial and 1.31 ±0.58 mm for the dolichofacial group (P=.03). The mean VJS in EMGRVD was 8.23 ±2.21 mm for the brachyfacial and 16.55 ±4.29 mm the dolichofacial group (P<.001). CONCLUSIONS: CR/PVD measurements in dolichofacial individuals were lower than those in brachyfacial individuals. EMGRVD measurements were higher in dolichofacial individuals than those in brachyfacial individuals. Biomechanical, physiological, and behavioral reasons might explain such diversity.

Comparative study of molar and incisor bite forces regarding deciduous, mixed, and definitive dentition.

Objective: To compare maximum incisor (MBFinc) and molar (MBFmol) bite forces regarding the type of dentition and sex and to establish a relationship between them.Methods: One hundred-five individuals were divided into 3 groups: G1 - 22 females/13 males (4-5 years); G2 - 15 females/20 males (11-12 years); and G3 - 16 females/19 males (17- 18 years). The maximum bite force was recorded with an extraoral measuring device. Three measurements were recorded: right and left molar level (MBFmol) and incisor level (MBFinc). The ratio %MBFinc/MBFmol was determined.Results: MBFmol and MBFinc values increased with age (p < 0.05). MBFmol showed statistically higher values than MBFinc (p < 0.05), when compared within the same group.Conclusion: MBFinc and MBFmol increased with age. For all groups, MBFmol showed higher values than MBFinc, and %MBFinc/MBFmol ratio was 1:2. No differences were found in maximum bite force between sexes.

Deslizamiento en céntrica y la prevalencia de ruido y/o sintomatología mioarticular de las ATM. Estudio descriptivo

Introducción. El deslizamiento en céntrica (DC) y su incidencia en la sintomatología mioarticular ha sido un tema ampliamente estudiado, sin embargo, aún no está clara la relación entre ambos fenómenos. Objetivo. Evaluar la relación entre el DC y la prevalencia de ruido y/o sintomatología mioarticular de las articulaciones temporomandibulares en una muestra de pacientes. Material y Método. Se analizó una muestra de 183 modelos de estudio con dentición permanente completa excluyendo terceros molares. Se midió el DC en sentido sagital, vertical y transversal. Se recopilaron los datos del examen funcional de cada paciente para registrar las variables ruido y sintomatología mioarticular. Resultados. La magnitud del DC en los sentidos sagital, vertical y transversal está relacionada significativamente (p<0,05) con la presencia de ruido articular. El DC como variable dicotómica está relacionado significativamente, en sentido vertical, con la presencia de sintomatología mioarticular de las articulaciones temporomandibulares. El DC como magnitud y como variable dicotómica, en los sentidos sagital y transversal, están relacionados significativamente con la presencia de ruido y sintomatología mioarticular. Conclusión. Los pacientes que presentan DC con valores superiores a los normales presentan algún tipo de ruido y/o sintomatología mioarticular.

Introduction. Centric slide (CS) and its incidence in myoarticular symptoms have been widely studied: However, the relationship between both phenomena is still unclear. Objective. To evaluate the relationship between CS and the prevalence of noise and/or myoarticular symptoms of the temporomandibular joints in a sample of patients. Material and method. A sample of 183 study models with complete permanent dentition, excluding third molars, was analyzed. CS was measured in the sagittal, vertical, and transverse directions. Data from the functional examination of each patient were collected to record the "noise" and "myoarticular symptoms" variables. Results. The magnitude of CS in the sagittal, vertical, and transverse directions is significantly (p<0.05) related to the presence of joint noise. CS as a dichotomous variable is significantly related, vertically, to the presence of myoarticular symptoms of the temporomandibular joints. As a magnitude and as a dichotomous variable in the sagittal and transverse directions, CS is significantly related to the presence of noise and myoarticular symptoms. Conclusion. Patients with CS values ​​higher than normal present some type of noise and/or myoarticular symptoms.

Efecto del entrenamiento muscular masticatorio en el desarrollo del patrón vertical facial en niños: revisión narrativa / Training effect of the masticatory muscles in the development of the vertical facial pattern in children: narrative review

RESUMEN: Introducción: El patrón de crecimiento facial se establece antes de la aparición del primer molar permanente. Un exceso de crecimiento vertical facial, corresponde a individuos de cara larga, con ángulos goniacos abiertos, alturas faciales inferiores aumentadas y músculos masticatorios de menor área transversal. Esto se asocia a presentar mordida abierta anterior, mordida cruzada, clase II esquelético, entre otros. El entrenamiento muscular masticatorio podría controlar el excesivo crecimiento vertical, generando fuerzas opuestas que favorezcan un crecimiento horizontal. Objetivo: Describir el efecto del entrenamiento muscular masticatorio en el desarrollo del patrón vertical facial en niños. Método: Se realizó una revisión narrativa mediante búsqueda electrónica en las bases de datos PubMed, EBSCO, Scopus, Cochrane, Trip Database y Epistemonikos. Se utilizaron las palabras clave: "músculos masticatorios", "maseteros", "temporales", "masticación", "ejercicio", "entrenamiento", "crecimiento vertical", "patrón vertical", "dolicofacial", "control vertical". Los términos MeSH: "músculos masticatorios", "ejercicio". Resultados: Se seleccionaron 15 artículos de los cuales 9 son ensayos clínicos, 4 son reportes de caso y 2 son estudios observacionales transversales. Conclusiones: El entrenamiento muscular masticatorio tiene efectos positivos, favoreciendo un mayor crecimiento horizontal en niños con patrón vertical. No obstante, faltan estudios y ensayos clínicos para establecer y cuantificar los cambios morfológicos generados por el entrenamiento muscular.

ABSTRACT: Background: The pattern of facial growth is established before the eruption of the first permanent molar. An excess of vertical facial growth corresponds to individuals with long faces, open gonial angles, higher inferior facial heights and smaller masticatory muscles associated with different dental anomalies like anterior open bite, Brodie bite, skeletal class II and others. The masticatory muscle training could control the excessive growth in the vertical dimension, making opposing forces that will favor the horizontal growth in the patient. Objective: Describe the effect of the masticatory muscle training in the development of the vertical pattern in children. Method: A narrative review was done by an electronic research in PubMed, EBSCO, Scopus, Cochrane, Trip Database y Epistemonikos. The following key words were used: "masticatory muscles", "masseter", "temporalis", "mastication", "chewing", "exercise", "training", "vertical growth", "vertical pattern", "dolichofacial", "vertical control". The MeSH terms: "masticatory muscles", "exercise". Results: Fifteen articles were selected, 9 of them were clinical trials, 4 were case reports and 2 were observational studies. Conclusions: The literature review shows that the masticatory muscle training has positive effects, favoring the horizontal growth in children with vertical facial pattern. Nevertheless, there is a lack of studies and clinical trials, that could help us to establish and quantify the morphological changes made by the masticatory muscle training.

Vertical dimension. Part 2: the changes in electrical activity of the cervical muscles upon varying the vertical dimension.

This study was conducted in order to determine the effect of vertical dimension variation on the electromyographic (EMG) activity of the sternocleidomastoid and trapezius muscles. The study was performed on 15 healthy subjects. Basal tonic electromyographic (BT-EMG) recordings were performed by placing surface electrodes on the left sternocleidomastoid and trapezius muscles. BT EMG activity was recorded upon varying the vertical dimension every five millimeters from vertical dimension of occlusion to 45 millimeters of jaw opening (series 1), following the habitual opening path. Afterward, BT-EMG activity was recorded every millimeter from vertical dimension of occlusion to 4 mm, and then every two millimeters from four to ten millimeters (series 2). In series 1, a significant increase of BT-EMG activity was observed in both muscles (simple logarithmic regression analysis). In series 2, a significant increase was observed in the sternocleidomastoid muscle whereas trapezius muscle did not present a significant change. BT-EMG behavior of the sternocleidomastoid muscle in series 2 could be relevant when dentists increase vertical dimension by means of intermaxillary appliances during a short-term period. Moreover, these results add further information to the concept of the interrelatedness between the different components of the cranio cervical-mandibular system.