RESUMO
BACKGROUND: Mandibular flexion (MF) is a complex biomechanical phenomenon, which involves a deformation of the mandible, due mainly to the contraction of the masticatory muscles, and it can have numerous clinical effects. The deformation of the lower jaw caused by mandibular flexion is generally very small, and it is often overlooked and considered irrelevant from a clinical point of view by many authors; however, it should be important to remember that median mandibular flexure (MMF) has a multifactorial aetiology. The main aim of the current systematic review is to highlight the different factors that can increase MF in order to help clinicians identify patients to whom they should pay more attention. As a secondary outcome, we wanted to analyse the preventive measures and suitable techniques to be adopted to minimise the negative effects of this phenomenon on oral fixed rehabilitations. METHODS: The review, which was carried out in accordance with the "Preferred Reporting Items for Systematic reviews and Meta-Analyses" (PRISMA) flowchart, was recorded in the "International Prospective Register of Systematic Reviews" (PROSPERO). As research questions, "Patient/Population, Intervention, Comparison and Outcomes" (PICO) questions were employed. Using the ROBINS-I technique, the risk of bias in non-randomised clinical studies was evaluated. RESULTS: The initial electronic search identified over 1300 potential articles, of which 54 studies were included in this systematic review. Information regarding the relationship between MF and individual factors, mandibular movements, impression taking, and fixed rehabilitations were obtained. CONCLUSIONS: The studies included in this systematic review showed that MF is greater during protrusive movements, in the posterior areas of the lower jaw, and in patients with brachial facial type, greater jaw length; small gonial angle; and less density, length, and bone surface of the symphysis. The biomechanical effects of mandibular flexion on fixed restorations are debated. Prospective clinical and radiological observational studies should be conducted to evaluate the potential short-, medium-, and long-term consequences of MF.
RESUMO
PURPOSE: The present study was performed to examine the mandibular deformation during mouth opening in edentulous patients, treated with an implant-supported fixed prosthesis using strain gauges, and identify factors affecting deformation. METHODS: Twenty patients with a fully edentulous mandible who received either 4 or ≥6 implants were included. The distal-most implants were placed mesial to the mental foramen (premolar region) in patients with 4 implants and distal to the mental foramen (molar region) in patients with ≥6 implants. Mandibular deformation during mouth opening was measured using strain gauges in two directions: anteroposterior direction and lateral direction between the distal-most implants on the left and right sides (arch width). The mandibular anatomy was evaluated using computed tomography. RESULTS: Arch width reduction between the left and right implants during mouth opening ranged from 47.38 to 512.80 µm; the range of deformation was 0.12 to 15.14 µm in the anteroposterior direction. Furthermore, a significant positive correlation was noted between arch width reduction in the premolar region and the ratio between the symphyseal bone height and width (P = 0.0003, r = 0.72). CONCLUSION: The reduction in arch width was higher in the molar region than in the premolar region during mouth opening. Moreover, the reduction could be high in the mandibular symphyseal bone because of its greater height and lesser width. The ratio between the symphyseal bone height and width is defined as the mandibular deformation index (MDI) and is used to predict the rate of mandibular bone deformation.
Assuntos
Implantes Dentários , Arcada Edêntula , Boca Edêntula , Implantação Dentária Endóssea/métodos , Implantes Dentários/efeitos adversos , Prótese Dentária Fixada por Implante/efeitos adversos , Humanos , Arcada Edêntula/cirurgia , Mandíbula/cirurgiaRESUMO
Mandibular deformity is a condition that affects the jaw bone of adult salmon and has been observed in Norway and Chile, causing weight loss, poor quality of farmed fish and increased mortality. The causes range from high temperatures of the state of eggs, to poor nutrition phosphorus or vitamin C. This work aims to analyze this deformity by histochemical and mineral analysis technique during an episode presented in centers of the Scotia Sea. Jaw and spinal segments of 21 Atlantic salmon in Scotland were used. These samples were classified into three groups: Group 1: Severely deformed. Group 2: Mildly affected. Group 3: Normal controls. Four jaws per group were fixed in 10 % formalin and embedded in Paraplast, sections of 5 microns were performed using a Microm® microtome histochemical technique Von Kossa was used for the detection of calcium deposits, which highlights the calcium osteoid black and red color. For proximate analysis, and in order to obtain and compare levels of calcium, phosphorus, zinc and magnesium in total 9 bone jaws (6 affected with DM and 3 controls) and 9 body sections the Mann-Whitney test was used to compare these values between misshapen salmon and controls. To correlate values, jaw and body segment a Spearman corrrelation was applied. Fish group 1 presented a ventral deviation of the alveolar bone body. In fish group 2 prominence of the visible joint on both sides or unilaterally was observed. Comparing the values of % Ca, % P, % Mg and Zn jaws with DM and healthy ones with Mann Witney method it was found that the values of these minerals vary between salmon and controls affected. There was a significant difference in the percentage of P, which indicates that there is less P in affected fish vertebrae. Spearman correlation noted that the percentages of the minerals studied in dental bone and vertebral segments are uncorrelated. Rather, Von Kossa distribution indicates that Ca/P is not homogeneous in the dental bone, as a result of mineral resorption from the skeleton including the operculum, articular bone and dental towards kype. This paper states that Von Kossa histochemical technique showed significant differences between deformed fish and controls and also showed differences between the various segments of the dental bone. The alveolar bone is a dynamic structure adapted to continuous histological changes may be involved in MD, phosphorus deficient diets, coupled with the initial formation of Kippe.
La deformación mandibular es una patología que afecta al hueso dentario de salmones adultos, se observó en Noruega y en Chile, ocasionando disminución de peso, baja calidad de peces cultivados y aumento de la mortalidad. Las causas varían desde temperaturas elevadas al estado de ovas, hasta alimentación deficitaria en fósforo o vitamina C. Este trabajo tiene como propósito analizar esta deformación mediante una técnica histoquímica y de análisis de minerales durante un episodio presentado en centros de mar de Escocia. Se utilizó la mandíbula y segmento vertebral de 21 salmones del Atlántico de Escocia. Estas muestras se clasificaron en tres grupos Grupo 1: Severamente deformes. Grupo 2: Levemente afectados. Grupo 3: Controles normales. Cuatro mandíbulas por grupo fueron fijadas en formalina al 10 % y se incluyeron en paraplast, se realizaron cortes de 5 µm utilizando un micrótomo Microm®. Se utilizó la técnica histoquímica de Von Kossa para la detección de depósitos de calcio la cual destaca al calcio de color negro y el osteoide de color rojo. Para el análisis químico proximal, y con el propósito de obtener y comparar niveles de calcio, fósforo, zinc y magnesio en los huesos se utilizó un total de 9 mandíbulas (6 afectadas con DM y 3 controles) y sus 9 secciones corporales. Para comparar estos valores entre salmones deformes y controles se utilizó la prueba de Mann-Whitney. Para correlacionar los valores de mandíbula y segmento corporal se hizo una correlación por jerarquías de Spearman. Los peces del grupo 1, presentaron una desviación ventral del cuerpo del hueso dentario. En los peces del grupo 2 se observó la prominencia de la articulación visible en ambos lados o unilateralmente. Al comparar los valores de % Ca, % P, % Mg y Zn de las mandíbulas con DM y sanas con el método de Mann Witney se encontró que los valores de estos minerales no varían entre salmones afectados y controles. Hubo una diferencia significativa en el porcentaje de P, lo cual indica que existe menos P en vértebras de peces afectados. La correlación de Spearman señaló que los porcentajes de los minerales estudiados en huesos dentarios y segmentos vertebrales no están correlacionados. Por el contrario, la técnica Von Kossa mostró que la distribución de Ca/ P no es homogénea en el hueso dental producto de la reabsorción mineral desde el esqueleto incluyendo el opérculo, hueso articular y dental hacia la kype. El presente trabajo establece que la técnica histoquímica de Von Kossa fue la que permitió observar diferencias importantes entre peces deformados y controles, además mostró diferencias entre los distintos segmentos del hueso dentario. El hueso dentario es una estructura dinámica adaptada a continuos cambios histológicos pudiendo estar involucrados en la DM, dietas deficientes de fósforo, sumado a la formación inicial del Kippe.
