The Law of Minimum Vertical Dimension: Evidence for Improvement of Dental Occlusion.

The law of minimum vertical dimension (MVD) states that "when the mandible moves to reach the maximum intercuspal position, this always involves bringing the mandible and maxilla as close together as possible." Therefore, after the first occlusal contact is made, the MIP will be reached through reduction of the vertical dimension. Our objective of this study, through an integrative review of the literature review, was to determine whether ignoring this law is a factor that contributes to malocclusion, temporomandibular joint dysfunction, and recurrences of functional orthodontic and orthopedic treatments.We conducted a search of the literature in five of the main electronic scientific databases. The following medical subject heading terms were used in our search: centric relation, dental occlusion, malocclusion, vertical dimension, and mastication. We cross-referenced the descriptors in the following four groups: centric relation and maximum intercuspation; occlusal plane and malocclusion; neuro-occlusal rehabilitation; and vertical dimension and unilateral chewing. From this, we selected 277 potentially eligible articles. Out of these, 209 were excluded in accordance with the exclusion criteria already described. Thus, 65 studies were included in the qualitative synthesis.The articles were also classified according to their impact factor and degree of recommendation, in conformity with the table of the Oxford Centre for Evidence-Based Medicine. The scientific interest in the scope of the articles was also assessed by using three charts developed according to year and country of publication and the percentage of publication. Unilateral chewing creates a vicious cycle of damage that leads to an ever-increasing masticatory deficiency. Most of the articles chosen for this review confirmed that noncompliance with law of MVD was a predisposing factor in cases of relapse, in functional orthodontic and orthopedic treatments, as well as a causal factor in malocclusion and in functional and morphological TMJ dysfunctions.

Home sleep apnea testing: an accuracy study.

AIM: There are no studies comparing tests performed at home with those carried out in the laboratory, using the same device. The only studies that have been performed have compared the device used at home with the standard polygraph used in the laboratory. The purpose of this study was therefore to verify the accuracy of the home diagnosis of obstructive sleep apnea syndrome (OSAS) via unassisted type 2 portable polysomnography, compared with polysomnography using the same equipment in a sleep laboratory. METHODS: To avoid any possible order effect on the apnea-hypopnea index (AHI), we randomly created two groups of 20-total 40 patients, according to the test sequence. One of the groups had the first test at home and the second test in the laboratory (H-L); the other group had the first test in the laboratory and the second at home (L-H). The second test always took place on the night immediately following the first test. All polysomnographic monitoring was undertaken with the same equipment, an Embletta X100 system (Embla, Natus Inc., Middleton, USA). The Embletta X100 is a portable polygraph that records eleven polygraph signs: (1) electroencephalogram C4/A; (2) electroencephalogram O2/M1; (3) submental EMG; (4) electrooculogram of the right side; (5) nasal cannula (air flow); (6) respiratory effort against a plethysmographic chest strap; (7) respiratory effort against an abdominal plethysmographic belt; (8) heart rate; (9) saturation of oxyhemoglobin; (10) snoring; and (11) body position. RESULTS: There was no difference in sleep efficiency between the group monitored in the laboratory and the group tested at home (p = 0.30). There was no difference in total sleep time (p = 0.11) or sleep latency (p = 0.52), or in the latency in phases N2 and N3 between the monitoring in the laboratory and at home (N2 p = 0.24; N3 p = 0.09). Some differences occurred regarding the PSG that took place at home, with longer duration of wake after sleep onset (WASO) and longer latency for REM sleep, due to failure of the patient to start the monitoring by pressing the "events" button on the device. In the distribution of sleep phases, there was no difference between the group monitored in the laboratory and the group tested at home. CONCLUSION: Results from home sleep monitoring correlate well with the laboratory "gold standard" and may be an option for diagnosing OSAS in selected patients.

The Effect of Fibroblast Growth Factors in Grafted Fascia into the Vocal Fold of Rabbits

Abstract Introduction The human larynx is a very important organ for communication. Many conditions lead to scarring of the vocal folds, decreasing voice quality. Objective We aimed to determine whether fibroblast growth factors (FGFs) may influence tissue integration of grafted fascia into the vocal folds of an animal model. Methods This is an experimental animal study with 12 adult rabbits that were submitted to a grafting fragment obtained from superficial cervical fascia into the vocal fold lamina propria, bilaterally. The right vocal fold was injected with FGFs. The animals were sacrificed after 1 month or 12 months, depending on the group they were assigned to, and a histological analysis of their vocal folds was performed.We analyzed the histological changes (such as the presence of fibrosis and neovascularization) induced by the acute or chronic inflammatory reactions. Results The FGFs induced acute inflammatory changes in all animals after 1 month of the initial experiment. The presence of FGFs triggered more fibrosis than the expected due to the surgical procedure itself when compared with the control side of all animals after 12 months of the initial experiment. Conclusions Fibroblast growth factors alone do not represent a good therapeutic option in phonosurgery, since we observed higher levels of fibrosis in the vocal fold lamina propria. Further studies combining more substances may be necessary to elucidate the best option to be used in this kind of surgery. (AU)

The Effect of Fibroblast Growth Factors in Grafted Fascia into the Vocal Fold of Rabbits.

Introduction The human larynx is a very important organ for communication. Many conditions lead to scarring of the vocal folds, decreasing voice quality. Objective We aimed to determine whether fibroblast growth factors (FGFs) may influence tissue integration of grafted fascia into the vocal folds of an animal model. Methods This is an experimental animal study with 12 adult rabbits that were submitted to a grafting fragment obtained from superficial cervical fascia into the vocal fold lamina propria, bilaterally. The right vocal fold was injected with FGFs. The animals were sacrificed after 1 month or 12 months, depending on the group they were assigned to, and a histological analysis of their vocal folds was performed. We analyzed the histological changes (such as the presence of fibrosis and neovascularization) induced by the acute or chronic inflammatory reactions. Results The FGFs induced acute inflammatory changes in all animals after 1 month of the initial experiment. The presence of FGFs triggered more fibrosis than the expected due to the surgical procedure itself when compared with the control side of all animals after 12 months of the initial experiment. Conclusions Fibroblast growth factors alone do not represent a good therapeutic option in phonosurgery, since we observed higher levels of fibrosis in the vocal fold lamina propria. Further studies combining more substances may be necessary to elucidate the best option to be used in this kind of surgery.

Cephalometric evaluation of the airway space and hyoid bone in children with atypical deglutition: correlations study / Evaluación cefalométrica del espacio de las vías respiratorias y hueso hioides en niños con deglución atípica: estudio correlacional

Although there is a close relationship between swallowing and breathing are no studies that relate to atypical swallowing radiographic anatomy of the airway space and its possible correlation with the radiographic position of the hyoid bone. The aim was to evaluate the possible correlation with the radiographic position of the hyoid bone and airway space in lateral radiographs of children with atypical deglutition. Using cephalometric analysis on lateral teleradiographs, the distances of H-MP (hyoid to mandibular plane) and H-T (hyoid to tuber) were Spearman's correlation analysis was performed with PAS (airway space) in two groups: the experimental group with atypical deglutition and the control group normal deglutition. Both groups included subjects in mixed dentition stage. Thevariable T-H had statistically significant correlation with PAS (0.0286) and the variable MP-H had significant correlation with variable PAS (0.0053). Ourresults show that advanced positive correlation of the radiographic position of the hyoid bone to the airway space only in the group of normal swallowing. The lower airway in patients with atypical swallowing, causing changes in tongue posture which leads to change in the position of the hyoid bone.

Aunque existe una estrecha relación entre la deglución y la respiración, no se dispone de estudios que relacionen la anatomía radiográfica atípica de deglución del espacio de la vía aérea y su posible correlación con la posición radiológica del hueso hioides. El objetivo fue evaluar la posible correlación de la posición radiológica del hueso hioides y las vías aéreas en radiografías laterales de niños con deglución atípica. Utilizando el análisis cefalométrico sobre telerradiografías laterales, fueron analizadas las correlaciones entre las distancias H-MP (hueso hioides al plano mandibular) y HT (hioides al tubérculo) y el PAS (espacio de la vía aérea) en dos grupos: el grupo experimental con la deglución atípica y el grupo control con deglución normal. Ambos grupos estaban en etapa de dentición mixta. Las variables HT y MP-H tuvieron una correlación estadísticamente significativa con la variable PAS, 0,0286 y 0,0053 respectivamente. Nuestros resultados muestran que la correlación positiva de la situación radiológica avanzada del hueso hioides al espacio de las vías respiratorias sólo se observa en el grupo de deglución normal. La vía respiratoria inferior en los pacientes con deglución atípica provoca cambios en la postura de la lengua, lo que conduce a un cambio en la posición del hueso hioides.

Radiographic position of the hyoid bone in children with atypical deglutition.

The persistence of childlike deglutition after the replacement of deciduous teeth is described as atypical deglutition. This condition has been attributed to sucking action without nutritive purposes, use of a feeding bottle, oral respiration, and anatomical abnormalities. Among the possible anatomical alterations, the hyoid bone, as a result of being the origin or the insertion of several muscles involved in swallowing, may have its position altered in cases of atypical deglutition. The aim of the present study was to evaluate the position of the hyoid bone using lateral teleradiographs, among patients with atypical deglutition during the stage of mixed dentition. Using cephalometric analysis on lateral teleradiographs, the distances of H-MP (hyoid to mandibular plane) and H-T (hyoid to tuber) were measured in two groups: the experimental group with atypical deglutition and the control group normal deglutition. Both groups included subjects in mixed dentition stage. Measurements from the groups were compared using Mann-Whitney U-test and a P-value <0.05 was considered as an indication of statistical significance. The average distance of the H-MP variable was 11.69 mm for the control group and 16.14 mm for the experimental group, with a statistically significant difference (P = 0.016). The average distance of the H-T variable was 2.26 mm for the control group and -5.89 mm for the experimental group, with significant difference (P < 0.001). There was no correlation among the variables studied. Cephalometric analysis of the H-MP distance revealed a mean difference of approximately 5 mm between the two groups, and the difference was more than 7 mm for H-T distance. Distances of H-MP and H-T based on radiographic measurements were greater in individuals with atypical deglutition than in control group and there was no correlation between these two parameters.