Mandibular Torus : A Synthesis of New and Previously Reported Data and a Discusssion of its Cause

Usinig original data on 1,5000 mandibles, but mainly previously published data, I present a overview of the distribution characteristics of mandibular torus and a hypothesis concerning its cause. Pedigree studies have established that genetic factors influence torus development. Extrinsic factors are strongly implicated by other evidence: prevalence among Arctic peoples, effect of dietary change, age regression, preponderance in males and on the right side, effect of cranial deformation, concurrence with palatine torus and maxillary alveolar exostoses, and clinical evidence. I propose that the primary factor is masticatory stress. According to a mechanism suggested by orthodontic research, the horizontal component of bite force tips the lower canine, premolars and first molar so that their root apices exert pressure on the periodontal membrane, causing formation of new bone on the lingual cortical plate of the alveolar process. Thus formed, the hyperostosis is vulnerable to trauma and its periosteal covering becomes bruised causing additional deposition of bone. Genes influence torus indirectly through their effect on occlusion. A patern of increased expressivity with incidence suggests that a quasicontinuous model may provide a better fit to pedigree data than single locus models previously tested.

Molecular structure and function of the glycine receptor chloride channel

The glycine receptor chloride channel (GlyR) is a member of the nicotinic acetylcholine receptor family of ligand-gated ion channels. Functional receptors of this family comprise five subunits and are important targets for neuroactive drugs. The GlyR is best known for mediating inhibitory neurotransmission in the spinal cord and brain stem, although recent evidence suggests it may also have other physiological roles, including excitatory neurotransmission in embryonic neurons. To date, four alpha-subunits (alpha1 to alpha4) and one beta-subunit have been identified. The differential expression of subunits underlies a diversity in GlyR pharmacology. A developmental switch from alpha2 to alpha1beta is completed by around postnatal day 20 in the rat. The beta-subunit is responsible for anchoring GlyRs to the subsynaptic cytoskeleton via the cytoplasmic protein gephyrin. The last few years have seen a surge in interest in these receptors. Consequently, a wealth of information has recently emerged concerning Glyl? molecular structure and function. Most of the information has been obtained from homomeric alpha1 GlyRs, with the roles of the other subunits receiving relatively little attention. Heritable mutations to human GlyR genes give rise to a rare neurological disorder, hyperekplexia (or startle disease). Similar syndromes also occur in other species. A rapidly growing list of compounds has been shown to exert potent modulatory effects on this receptor. Since GlyRs are involved in motor reflex circuits of the spinal cord and provide inhibitory synapses onto pain sensory neurons, these agents may provide lead compounds for the development of muscle relaxant and peripheral analgesic drugs.

Visual feedback alters the variations in corticospinal excitability that arise from rhythmic movements of the opposite limb

Augmented visual feedback can have a profound bearing on the stability of bimanual coordination. Indeed, this has been used to render tractable the study of patterns of coordination that cannot otherwise be produced in a stable fashion. In previous investigations (Carson et al. 1999), we have shown that rhythmic movements, brought about by the contraction of muscles on one side of the body, lead to phase-locked changes in the excitability of homologous motor pathways of the opposite limb. The present study was conducted to assess whether these changes are influenced by the presence of visual feedback of the moving limb. Eight participants performed rhythmic flexion-extension movements of the left wrist to the beat of a metronome (1.5 Hz). In 50% of trials, visual feedback of wrist displacement was provided in relation to a target amplitude, defined by the mean movement amplitude generated during the immediately preceding no feedback trial. Motor potentials (MEPs) were evoked in the quiescent muscles of the right limb by magnetic stimulation of the left motor cortex. Consistent with our previous observations, MEP amplitudes were modulated during the movement cycle of the opposite limb. The extent of this modulation was, however, smaller in the presence of visual feedback of the moving limb (FCR omega(2) =0.41; ECR omega(2)=0.29) than in trials in which there was no visual feedback (FCR omega(2)=0.51; ECR omega(2)=0.48). In addition, the relationship between the level of FCR activation and the excitability of the homologous corticospinal pathway of the opposite limb was sensitive to the vision condition; the degree of correlation between the two variables was larger when there was no visual feedback of the moving limb. The results of the present study support the view that increases in the stability of bimanual coordination brought about by augmented feedback may be mediated by changes in the crossed modulation of excitability in homologous motor pathways.

Glycinergic and GABAergic synaptic activity differentially regulate motoneuron survival and skeletal muscle innervation

GABAergic and glycinergic synaptic transmission is proposed to promote the maturation and refinement of the developing CNS. Here we provide morphological and functional evidence that glycinergic and GABAergic synapses control motoneuron development in a region-specific manner during programmed cell death. In gephyrin-deficient mice that lack all postsynaptic glycine receptor and some GABA(A) receptor clusters, there was increased spontaneous respiratory motor activity, reduced respiratory motoneuron survival, and decreased innervation of the diaphragm. In contrast, limb-innervating motoneurons showed decreased spontaneous activity, increased survival, and increased innervation of their target muscles. Both GABA and glycine increased limb-innervating motoneuron activity and decreased respiratory motoneuron activity in wild-type mice, but only glycine responses were abolished in gephyrin-deficient mice. Our results provide genetic evidence that the development of glycinergic and GABAergic synaptic inputs onto motoneurons plays an important role in the survival, axonal branching, and spontaneous activity of motoneurons in developing mammalian embryos.

The role of group I metabotropic glutamate receptor's in neuronal excitotoxicity in Alzheimer's disease

Neurodegenerative diseases such as Huntington's disease, ischemia, and Alzheimer's disease (AD) are major causes of death. Recently, metabotropic glutamate receptors (mGluRs), a group of seven-transmembrane-domain proteins that couple to G-proteins, have become of interest for studies of pathogenesis. Group I mGluRs control the levels of second messengers such as inositol 1,4,5-triphosphate (IP3) Cal(2+) ions and cAMP. They elicit the release of arachidonic acid via intracellular Ca2+ mobilization from intracellular stores such as mitochondria and endoplasmic reticulum. This facilitates the release of glutamate and could trigger the formation of neurofibrillary tangles, a pathological hallmark of AD. mGluRs regulate neuronal injury and survival, possibly through a series of downstream protein kinase and cysteine protease signaling pathways that affect mitochondrially mediated programmed cell death. They may also play a role in glutamate-induced neuronal death by facilitating Cal(2+) mobilization. Hence, mGluRs have become a target for neuroprotective drug development. They represent a pharmacological path to a relatively subtle amelioration of neurotoxicity because they serve a modulatory rather than a direct role in excitatory glutamatergic transmission.

Distinct physiological mechanisms underlie altered glycinergic synaptic transmission in the murine mutants spastic, spasmodic, and oscillator

Spastic (spa), spasmodic (spd), and oscillator (ot) mice have naturally occurring glycine receptor ( GlyR) mutations, which manifest as motor deficits and an exaggerated startle response. Using whole-cell recording in hypoglossal motoneurons, we compared the physiological mechanisms by which each mutation alters GlyR function. Mean glycinergic miniature IPSC ( mIPSC) amplitude and frequency were dramatically reduced (> 50%) compared with controls for each mutant. mIPSC decay times were unchanged in spa/spa (4.5 +/- 0.3 vs 4.7 +/- 0.2 ms), reduced in spd/spd (2.7 +/- 0.2 vs 4.7 +/- 0.2 ms), and increased in ot/ot (12.3 +/- 1.2 vs 4.8 +/- 0.2 ms). Thus, in spastic, GlyRs are functionally normal but reduced in number, whereas in spasmodic, GlyR kinetics is faster. The oscillator mutation results in complete absence of alpha 1-containing GlyRs; however, some non-alpha 1-containing GlyRs persist at synapses. Fluctuation analysis of membrane current, induced by glycine application to outside-out patches, showed that mean single-channel conductance was increased in spa/spa (64.2 +/- 4.9 vs 36.1 +/- 1.4 pS), but unchanged in spd/spd (32.4 +/- 2.1 vs 35.3 +/- 2.1 pS). GlyR-mediated whole-cell currents in spa/spa exhibited increased picrotoxin sensitivity (27 vs 71% block for 100 mu M), indicating alpha 1 homomeric GlyR expression. The picrotoxin sensitivity of evoked glycinergic IPSCs and conductance of synaptic GlyRs, as determined by nonstationary variance analysis, were identical for spa/spa and controls. Together, these findings show the three mutations disrupt GlyR-mediated inhibition via different physiological mechanisms, and the spastic mutation results in compensatory alpha 1 homomeric GlyRs at extrasynaptic loci.

REABSORÇÃO CONDILAR INTERNA DA ARTICULAÇÃO TEMPOROMANDIBULAR NO PACIENTE ADOLESCENTE

A reabsorção condilar interna no adolescente (RCIA) é uma doença progressiva que afeta a articulação temporomandibular (ATM) e que pode resultar em maloclusão, deformidade facial, disfunção de ATM e dor. O aparecimento desta doença ocorre entre os 10 e os 15 anos, sendo mais freqüente em adolescentes do sexo feminino. Esses pacientes apresentam sinais clínicos característicos como: ângulo do plano oclusal e do plano mandibular aumentados, retrusão progressiva da mandíbula e maloclusão Classe II, com ou sem mordida aberta. Nos exames de imagem (tomografia computadorizada e ressonância magnética), observa-se reabsorção interna dos côndilos e deslocamento dos discos articulares da ATM. Tendo em vista a dificuldade em determinar a causa da RCIA e a importância em eliminar a dor e melhorar a função mastigatória, este estudo se propôs a avaliar as alterações promovidas no posicionamento mandibular, a sintomatologia dolorosa e a estabilidade do tratamento da RCIA, utilizando o protocolo de tratamento (Dr. Larry M. Wolford) em pacientes adolescentes submetidos a cirurgia de reposicionamento do disco articular e cirurgia ortognática, realizadas no mesmo ato cirúrgico. Neste estudo retrospectivo, foram avaliadas as telerradiografias laterais adquiridas na avaliação inicial (T1), pré-cirúrgica (T2), pós-cirúrgica imediata (T3) e de maior acompanhamento, com pelo menos um ano pós-cirurgia (T4) e questionários de dor e função mandibular de uma amostra de 24 pacientes com maloclusão de Classe II (20 do sexo feminino e 4 do sexo masculino) diagnosticados com RCIA, os quais foram submetidos ao protocolo de tratamento composto pela cirurgia de reposicionamento do disco articular da ATM concomitantemente à cirurgia ortognática. O protocolo de tratamento utilizado mostrou-se bastante positivo, uma vez que a estabilidade foi adquirida e uma melhora significativa nos níveis de dor e função mandibular foram atingidos. O tratamento dos pacientes diagnosticados com RCIA, através do protocolo de tratamento proposto, é um procedimento estável e atua diretamente em um ganho na redução da dor.

AVALIAÇÃO DA EFICIÊNCIA MASTIGATÓRIA NA MORDIDA ABERTA ANTERIOR POR MEIO DO DISPOSITIVO ME MASTIG

Este trabalho avaliou a eficiência mastigatória na maloclusão do tipo Mordida Aberta Anterior por meio do Me-mastig, dispositivo que pode ser utilizado no sentido de se mensurar a eficiência da mastigação, prometendo ser uma alternativa prática, rápida e eficiente para o exame da mastigação. O grupo experimental compôs-se de 106 crianças na faixa etária dos 07 aos 11 anos, divididos em 2 grupos, da seguinte forma: (A) Grupo de Mordida Aberta Anterior, contendo 51 crianças e (B) Grupo Controle, com trespasse vertical normal contendo 55 crianças. Procurou-se avaliar a eficiência mastigatória das crianças dos dois grupos e comparar os resultados, que mostraram que a mastigação do grupo mordida aberta anterior foi menos eficiente quando comparada à do grupo controle; fato que se pode explicar pelas características faciais dos indivíduos portadores da maloclusão estudada e também características da própria maloclusão de mordida aberta anterior. Conclusões, a mordida aberta anterior é responsável por uma diminuição significativa da a Eficiência Mastigatória e o dispositivo Me-mastig se mostrou um método eficaz, de fácil utilização e não dispendioso que pode ser usado na clínica diária para se medir ou avaliar a Eficiência Mastigatória.

Complete denture occlusion: an evidence-based approach

Purpose: This study involved an extensive search for randomized controlled clinical trials comparing bilateral balanced and canine-guided dentures, and questioned whether a bilateral balanced occlusion is imperative for successful denture treatment. Materials and Methods: Studies were identified by searching electronic databases (PubMed/MEDLINE, ISI Web of Science, LILACS, and BBD). The keywords “denture” and “occlusion” were used. The minimum inclusion requirements were (1) randomized controlled trials with patients of any age wearing both maxillary and mandibular conventional complete dentures (CDs), (2) comparison between bilateral balanced and canine-guided dentures, and (3) assessment of masticatory function and/or patients’ satisfaction. Results: The search resulted in the identification of 5166 articles. Subsequently, 5156 articles were excluded on the basis of title and abstract. By the end of the search phase, seven randomized controlled trials were considered eligible. Conclusions: Current scientific evidence suggests that bilateral balanced occlusion is not imperative for successful treatment with conventional CDs in average patients. More studies are necessary to identify if specific clinical conditions may benefit from a balanced occlusion.

Longitudinal Clinical Evaluation of Undercut Areas and Rest Seats of Abutment Teeth in Removable Partial Denture Treatment

PURPOSE: Adequate preparation of abutment teeth for removable partial denture (RPD) rest seats allows appropriate masticatory force transmission, retention, and stability of supporting structures. It follows that careful preparation will be important for the longevity of the rehabilitation. The present study aimed to clinically evaluate rest seats and undercut areas of abutment teeth in RPD wearers after 2 years of use. MATERIALS AND METHODS: A total of 193 occlusal, incisal, and cingulum rest seats were evaluated in terms of shape, rest adaptation, wear, caries, fractures, and surface type (enamel, composite resin, or amalgam). Two hundred and fourteen undercut areas were evaluated in terms of surface type (enamel or restoration) and integrity. This study was approved by the Research Ethics Committee of the Federal University of Rio Grande do Norte, resolution 196/1996, protocol number 11/05. RESULTS: Intact preparations accounted for 92.2% of the total. Application of the Pearson test (p= 0.289) found no statistically significant differences among the materials on which the rest seats were prepared. For the undercut areas, 20.7% of those obtained on restorative material were nonintact. In addition, Fisher's exact test showed a statistically significant difference (p= 0.001) in surface type; enamel surfaces were shown to be 14 times more stable than restored surfaces. CONCLUSIONS: The results of this study suggest that rest seats are stable, regardless of the material on which they are prepared. Retentive areas were shown to be more stable when they were located in enamel.

Longitudinal Clinical Evaluation of Undercut Areas and Rest Seats of Abutment Teeth in Removable Partial Denture Treatment

PURPOSE: Adequate preparation of abutment teeth for removable partial denture (RPD) rest seats allows appropriate masticatory force transmission, retention, and stability of supporting structures. It follows that careful preparation will be important for the longevity of the rehabilitation. The present study aimed to clinically evaluate rest seats and undercut areas of abutment teeth in RPD wearers after 2 years of use. MATERIALS AND METHODS: A total of 193 occlusal, incisal, and cingulum rest seats were evaluated in terms of shape, rest adaptation, wear, caries, fractures, and surface type (enamel, composite resin, or amalgam). Two hundred and fourteen undercut areas were evaluated in terms of surface type (enamel or restoration) and integrity. This study was approved by the Research Ethics Committee of the Federal University of Rio Grande do Norte, resolution 196/1996, protocol number 11/05. RESULTS: Intact preparations accounted for 92.2% of the total. Application of the Pearson test (p= 0.289) found no statistically significant differences among the materials on which the rest seats were prepared. For the undercut areas, 20.7% of those obtained on restorative material were nonintact. In addition, Fisher's exact test showed a statistically significant difference (p= 0.001) in surface type; enamel surfaces were shown to be 14 times more stable than restored surfaces. CONCLUSIONS: The results of this study suggest that rest seats are stable, regardless of the material on which they are prepared. Retentive areas were shown to be more stable when they were located in enamel.

Mastigatory efficiency in denture wears with bilateral balanced occlusion and canine guidance

The maintenance of masticatory function is especially important for patients wearing complete dentures due to their limitations. Thus, the bilateral balanced occlusal concept is used to achieve greater masticatory efficiency. However, a critical review of the literature reveals that there is not sufficient scientific evidence to support bilateral balanced occlusion as the most appropriate occlusal concept in complete dentures. Therefore, the aim of this study was to evaluate the masticatory efficiency in complete dentures wearers with bilateral balanced occlusion and canine guidance. A double-blinded controlled crossover clinical trial was conducted. The sample was composed by 24 edentulous patients who wore sets of complete dentures with both occlusal concepts during equal periods of 3 months. Objective data were collected through the masticatory efficiency test performed by the colorimetric method with the beads, in which capsules of a synthetic material enclosing fuchsine-containing granules were used. Subjective data were recorded by patient's ratings of their chewing function. No significant statistical difference was found for masticatory efficiency (p=0.095) between the two occlusal concepts studied. The results suggest that bilateral balanced occlusion does not improve the masticatory efficiency in complete denture wearers.

Mastigatory efficiency in denture wears with bilateral balanced occlusion and canine guidance

The maintenance of masticatory function is especially important for patients wearing complete dentures due to their limitations. Thus, the bilateral balanced occlusal concept is used to achieve greater masticatory efficiency. However, a critical review of the literature reveals that there is not sufficient scientific evidence to support bilateral balanced occlusion as the most appropriate occlusal concept in complete dentures. Therefore, the aim of this study was to evaluate the masticatory efficiency in complete dentures wearers with bilateral balanced occlusion and canine guidance. A double-blinded controlled crossover clinical trial was conducted. The sample was composed by 24 edentulous patients who wore sets of complete dentures with both occlusal concepts during equal periods of 3 months. Objective data were collected through the masticatory efficiency test performed by the colorimetric method with the beads, in which capsules of a synthetic material enclosing fuchsine-containing granules were used. Subjective data were recorded by patient's ratings of their chewing function. No significant statistical difference was found for masticatory efficiency (p=0.095) between the two occlusal concepts studied. The results suggest that bilateral balanced occlusion does not improve the masticatory efficiency in complete denture wearers.

Epítese gengival removível: alternativa estética e de rápida resolução para repor tecidos periodontais anteriores

The gingiva, part of the masticatory mucosa tissue that covers the alveolar process and surrounds the cervical portion of teeth, has a definitive shape and texture associated with the eruption of teeth. Therefore, it must be included in rehabilitative planning, as the absence of papillae induces problems with esthetics, phonetics and food-impaction. The purpose of the present study was to approach the indications, limitations and techniques for making a removable artificial gingiva made of acrylic resin, by reporting on a clinical case. The patient, a 29-year-old woman, with the sequelae of periodontal disease, presented loss of interdental papilla causing “black holes”. She was dissatisfied with the esthetic appearance of her teeth, and also complained of long teeth and air escaping when she spoke. As treatment, prosthetic reconstruction was proposed, by means of a removable artificial gingiva (gingival epithesis) to simulate the presence of interdental papillae, providing better esthetics and phonetics. Gingival epithesis is an easily made, inserted and hygienically cleaned appliance that provides a simple and safe alternative solution for cases in which surgical techniques are limited.

Epítese gengival removível: alternativa estética e de rápida resolução para repor tecidos periodontais anteriores

The gingiva, part of the masticatory mucosa tissue that covers the alveolar process and surrounds the cervical portion of teeth, has a definitive shape and texture associated with the eruption of teeth. Therefore, it must be included in rehabilitative planning, as the absence of papillae induces problems with esthetics, phonetics and food-impaction. The purpose of the present study was to approach the indications, limitations and techniques for making a removable artificial gingiva made of acrylic resin, by reporting on a clinical case. The patient, a 29-year-old woman, with the sequelae of periodontal disease, presented loss of interdental papilla causing “black holes”. She was dissatisfied with the esthetic appearance of her teeth, and also complained of long teeth and air escaping when she spoke. As treatment, prosthetic reconstruction was proposed, by means of a removable artificial gingiva (gingival epithesis) to simulate the presence of interdental papillae, providing better esthetics and phonetics. Gingival epithesis is an easily made, inserted and hygienically cleaned appliance that provides a simple and safe alternative solution for cases in which surgical techniques are limited.