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1.
J Oral Rehabil ; 48(8): 891-900, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-33983634

RESUMO

BACKGROUND: Passive mandibular advancement with functional appliances is commonly used to treat juvenile patients with mandibular retrognathism. OBJECTIVE: The aim of this study was to investigate whether active repetitive training of the mandible into an anterior position would result in a shift of the habitual mandibular position (HMP). METHODS: Twenty adult healthy subjects were randomly assigned to one of two groups: a training group receiving six supervised functional training sessions of 10 min each and a control group without training. Bonded lateral biteplates disengaged occlusion among both groups throughout the 15-day experiment. Customised registration-training appliances consisted of a maxillary component with an anterior plane and a mandibular component with an attached metal sphere. Training sessions consisted of repeated mouth-opening/closing cycles (frequency: 30/min) to hit an anteriorly positioned hemispherical target notch with this metal sphere. The HMP was registered at defined times during the experiment. RESULTS: The HMP in the training group showed a statistically significant anterior shift of 1.6 mm (interquartile range [IQR]: 1.2 mm), compared with a significant posterior shift of -0.8 mm (IQR: 2.8 mm) in the control group (p < .05). Although the anterior shift among the training group showed a partial relapse 4 days after the first training block, it then advanced slightly in the 4-day interval after the second training block, which might indicate neuroplasticity of the masticatory motor system. CONCLUSIONS: Motor learning by repetitive training of the mandible into an anterior position might help to improve the results of functional appliance therapy among patients with mandibular retrognathism.


Assuntos
Má Oclusão , Avanço Mandibular , Adulto , Cefalometria , Oclusão Dentária , Humanos , Mandíbula
2.
J Biomech ; 121: 110401, 2021 05 24.
Artigo em Inglês | MEDLINE | ID: mdl-33894471

RESUMO

So far, no practicable procedure exists to quantify the orthodontic loads applied to teeth in vivo. Dentists therefore rely on experience and simplified mechanical in-vitro experiments comprising deflection of orthodontic wires. Predicting the mechanical behaviour of orthodontic wires during clinical therapy requires understanding of the different contact states at multi-bracket-wire interfaces. This study experimentally investigates the effect of different bracket-wire contact configurations in a three-bracket setup and uses two numerical approaches to analyse and complement the experimental data. Commonly used round stainless-steel wires (diameter: 0.012″ and 0.016″) and titanium-molybdenum alloy wires (diameter: 0.016″ and 0.018″) were tested. All six force-moment components were measured separately for each of the three brackets. The results indicate that a specific sequence of distinct bracket-wire contact configurations occurs. Several transitions between configurations caused substantial changes of effective wire stiffness (EWS), which were consistent among experimental and numerical methods. The lowest EWS was observed for the configuration in which the wire touched only one wing of the lateral brackets. Taking this stiffness as 100%, the transition to a configuration in which the wire touched two opposing wings of the lateral brackets resulted in an increase of EWS of 300% ± 10%. This increase was independent of the wire type. Additional contacts resulted in further increases of stiffness beyond 400%. The results of this combined experimental and numerical study are important for providing a fundamental understanding of multi-bracket-wire contact configurations and have important implications for clinical therapy.


Assuntos
Braquetes Ortodônticos , Ligas Dentárias , Análise do Estresse Dentário , Fricção , Teste de Materiais , Fios Ortodônticos , Aço Inoxidável , Titânio
3.
J Oral Rehabil ; 48(4): 392-402, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33368502

RESUMO

BACKGROUND: Closing movements are among the jaw's basic physiological motor actions. During functional movements, the jaw changes position continually, which requires appropriate proprioception. However, the significance of the various proprioceptive receptors involved and how they interact is not yet fully clear. OBJECTIVES: This study's main objective was to test whether preventing intercuspation (IC) for 1 week would affect the precision of jaw-closing movements into IC and the functional space of habitual chewing movements (HCM). A secondary objective was to compare precision of jaw-closing movements into IC with the precision of movements into a target position (TP) far from IC. METHODS: Fourteen participants' HCM and jaw-closing movements into IC were recorded on two sessions (T1 and T2) 1 week apart. Between sessions, participants wore posterior bite plates to prevent IC. They also received a 10-minute training session at T1 to guide their jaw-closing movements into TP. The precision of the closing movements into IC and TP was analysed. For HCM, the vertical amplitude, lateral width and area of chewing cycles were evaluated. RESULTS: The precision of jaw movements into IC increased as the jaw gap decreased, but precision did not differ significantly between T1 and T2. For HCM, the vertical amplitude and area of chewing cycles increased significantly between T1 and T2. The precision of the closing trajectory into TP increased significantly during the training session. CONCLUSION: Our results confirm the excellent adaptability of the craniomandibular system, controlled by stringent motor programmes that are supported by continuous peripheral sensory input.


Assuntos
Mastigação , Movimento , Humanos , Arcada Osseodentária , Periodicidade
4.
J Orofac Orthop ; 80(5): 223-235, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31410493

RESUMO

OBJECTIVE: In vitro testing of archwires in a multibracket model may provide estimates of force-moment (F/M) systems applied to individual teeth in a realistic geometry. Such investigations have mostly been performed by continuous wire deflection, leading to frictional forces biasing the pure deflection forces. Aim of this study was to quantify this bias and the pure deflection forces for leveling archwires. MATERIALS AND METHODS: Three nickel-titanium (NiTi) and two multistranded wires were tested in a three-bracket model simulating vertical movement of an upper incisor with a typical interbracket distance of 8 mm (intercenter). To determine pure deflection forces, the middle bracket was first leveled incrementally from its vertical malposition to neutral position with repeated wire insertion at each step (so-called "static leveling mode"). For comparison, forces at the middle bracket were also determined during dynamic leveling with or without ligation of the wire at the lateral brackets by either elastic, tight or loose steel ligatures. RESULTS: The dynamic mode resulted in significantly lower mean leveling forces for all the tested wires (ANOVA [analysis of variance], p < 0.01) compared to the static mode. Expressed in numbers, dynamic wire unloading resulted in mean force underestimation of 53 ± 9% (loose steel ligatures), 56 ± 11% (elastic ligatures) or 91 ± 29% (tight steel ligatures). CONCLUSIONS: Orthodontic tooth movement is quasi-static. This concerns the initial hyalinization phase in particular. Thus, especially static testing of archwires provides valid reference data for the peak forces exerted directly after clinical insertion of a leveling wire. In dynamic wire testing, significant underestimation of actual forces exerted on individual teeth may occur due to experimental friction, which might considerably differ from that occurring during clinical therapy. This aspect has to be taken into account in the interpretation of published stiffness values for orthodontic wires, and in the selection of the appropriate archwire for leveling of the present tooth malposition, respectively.


Assuntos
Braquetes Ortodônticos , Análise do Estresse Dentário , Fricção , Teste de Materiais , Desenho de Aparelho Ortodôntico , Fios Ortodônticos , Titânio , Técnicas de Movimentação Dentária
5.
Am J Orthod Dentofacial Orthop ; 151(2): 407-415, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-28153171

RESUMO

INTRODUCTION: Recent studies have shown that therapeutic loads applied to individual teeth by aligners may substantially exceed recommended values. The primary purpose of this study was to quantify force and moment components during derotation of a maxillary central incisor when 0.3-mm-thick or 0.4-mm-thick polyethylene terephthalate glycol aligners were used instead of conventional polyethylene terephthalate glycol aligners with a minimum thickness of 0.5 mm. METHODS: The test setup consisted of an acrylic model of a maxilla with a separated right central incisor mounted on a 3-dimensional force and moment sensor. The force and moment components were recorded for aligners with thicknesses ranging from 0.3 to 0.75 mm during ±10° rotation and derotation of the separated incisor. RESULTS: Moments exerted by the thinnest aligner currently available, 0.5 mm, were 73.57 Nmm for the 10° mesiorotation. In comparison, the corresponding moments with the 0.4-mm and 0.3-mm aligners were 41.08 and 17.84 Nmm, respectively. Moment values for derotation of the maxillary right central incisor into neutral position showed nonlinear return curves indicating viscoelastic material behavior. CONCLUSIONS: A significant load reduction can be achieved with the new thinner aligners. Because of the form instability of the 0.3-mm aligner during handling, we suggest the novel sequence 0.4, 0.5, and 0.75 mm for aligner systems based on sequentially increased material thickness. This sequence combines sufficiently low initial aligner stiffness and steady load increases in single setup steps. The viscoelastic behavior of polyethylene terephthalate glycol aligners observed during incisor derotation should lead to a reduction of the high initial load exerted directly after intraoral aligner insertion.


Assuntos
Incisivo , Aparelhos Ortodônticos , Fenômenos Físicos , Humanos , Técnicas In Vitro , Maxila , Desenho de Aparelho Ortodôntico , Rotação
6.
Angle Orthod ; 86(6): 883-890, 2016 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27224904

RESUMO

OBJECTIVE: To evaluate whether overloading of teeth can be avoided by utilizing aligners with reduced thicknesses of 0.4 mm or 0.3 mm. MATERIALS AND METHODS: The experimental setup included an acrylic maxillary jaw model with tooth 11 separated and fixed via a 3-D force-moment transducer to a hexapod for experimental movement. Aligners tested were fabricated on duplicate stone models using commercially available polyethylene terephthalate glycol (PET-G) foils with thicknesses between 0.5 and 0.75 mm, and novel 0.4-mm- and 0.3-mm-thick foils. With the test aligner seated, 11 was bodily displaced in a labiopalatal direction in the range of ±0.25 mm while all six force-and-moment components exerted on this tooth were registered. RESULTS: With the thinnest commercially available 0.5-mm aligner, median forces of -7.89 N and 8.37 N were measured for the maximum 0.25-mm movement of 11 in a labial and palatal direction, respectively. In comparison, force values were 35% and 71% lower for the novel aligners with a thickness of 0.4 mm and 0.3 mm, respectively. CONCLUSIONS: Novel "leveling" aligners with reduced thickness may reduce overloading of individual teeth during aligner therapy. Due to form instability of 0.3-mm aligners, we suggest a novel sequence of 0.4-0.5-0.75 mm for aligner systems using several foil thicknesses for load graduation within single setup steps. This would combine low stiffness of the initial aligner and relatively constant load increases throughout the treatment.


Assuntos
Desenho de Aparelho Ortodôntico , Técnicas de Movimentação Dentária , Dente Canino , Humanos , Incisivo , Maxila
7.
J Orofac Orthop ; 76(6): 460-75, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26446503

RESUMO

OBJECTIVES: Aligners made of polyethylene terephthalate glycol (PET-G) were tested in an experimental study for labial and palatal translation of an upper central incisor to quantify the forces and moments thus delivered and to biomechanically evaluate the capability of bodily movement. MATERIALS AND METHODS: Using a resin model of the upper dentition, tooth 21 was separated and connected to a 3D force/moment (F/M) sensor to record the forces and moments delivered by aligners for labial and palatal displacement. An impression was taken with tooth 21 in its neutral position to obtain casts for standardized thermoplastic fabrication of aligners varying in make and foil thickness (Duran® 0.5/0.625/0.75 mm; Erkodur® 0.5/0.6/0.8 mm; Track-A® 0.5/0.63/0.8 mm). Upon placing each aligner over the teeth of the resin model, the separated tooth was subjected to 0.01 mm increments of labial and palatal translation by 0.25 mm in either direction. RESULTS: The mean forces delivered by the thinnest (0.5 mm) aligners for 0.25 mm of palatal displacement of tooth 21 were 3.01 ± 0.07 N (Duran®), 5.31 ± 0.89 N (Erkodur®), and 3.69 ± 0.81 N (Track-A®). The thickest (0.75 or 0.8 mm) aligners delivered 4.49 ± 0.16 N (Duran®), 7.22 ± 0.45 N (Erkodur®), and 5.20 ± 0.68 N (Track-A®). The mean forces for palatal as compared to labial displacement were higher by a mean of 48% with the Erkodur® and by 23% with the Track-A® aligners but were smaller by 37% with the Duran® aligners. The moment-to-force (M/F) ratios, calculated in relation to the center of resistance of the separated measurement tooth, ranged from -9.91 to -12.22 mm, thus, approaching the value of -8.80 mm for uncontrolled tipping of this tooth. CONCLUSION: Manufacturers of PET-G aligners have recommended setup increments of 0.5-1 mm, which appears excessive based on our results. PET-G aligners not featuring modifications (e.g., reinforcing ribs or composite attachments bonded to the teeth) are unsuitable for bodily movement of upper central incisors in labial or palatal directions.


Assuntos
Análise do Estresse Dentário/métodos , Incisivo/fisiopatologia , Má Oclusão/prevenção & controle , Má Oclusão/fisiopatologia , Aparelhos Ortodônticos Removíveis , Técnicas de Movimentação Dentária/instrumentação , Força de Mordida , Modelos Dentários , Humanos , Desenho de Aparelho Ortodôntico , Palato/fisiopatologia , Estresse Mecânico , Técnicas de Movimentação Dentária/métodos , Torque , Resultado do Tratamento
8.
J Orofac Orthop ; 76(6): 493-507, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26250455

RESUMO

OBJECTIVE: The purpose of this work was to evaluate the completeness of surface structure representation offered by full-arch impression scans in different situations of tooth (mal)alignment and whether this completeness could be improved by performing rescans on the same impressions reduced sequentially to different levels of gingival height and by adding extra single scans to the number of single scans recommended by the manufacturer. METHODS: Three pairs of full-arch resin models were used as reference, characterized either by normal occlusion, by anterior diastematic protrusion (and edentulous spaces in the lower posterior segments), or by anterior crowding. An alginate impression of each arch was taken and digitized with a structured-light scanner, followed by three rescans with the impression cut back to 10, 5, and 1 mm of gingival height. Both the initial scan and the rescans were performed both with 19 basic single scans and with 10 extra single scans. Each impression scan was analyzed for quantitative completeness relative to its homologous direct scan of the original resin model. In addition, the topography of voids in the resultant digital model was assessed by visual inspection. RESULTS: Compared to the homologous reference scans of the original resin models, completeness of the original impression scans--in the absence of both gingival cutback and extra single scans--was 97.23 ± 0.066% in the maxilla or 95.72 ± 0.070% in the mandible with normal occlusion, 91.11 ± 0.132% or 96.07 ± 0.109% in the arches with anterior diastematic protrusion, and 98.24 ± 0.085% or 93.39 ± 0.146% in those with anterior crowding. Gingival cutback and extra single scans were found to improve these values up to 100.35 ± 0.066% or 99.53 ± 0.070% in the arches with normal occlusion, 91.77 ± 0.132% or 97.95 ± 0.109% in those with anterior diastematic protrusion, and 98.59 ± 0.085% or 98.96 ± 0.146% in those with anterior crowding. CONCLUSION: In strictly quantitative terms, the impression scans did capture relatively large percentages of the total surface. However, the topographic examinations revealed that regions essential for orthodontic model analysis were missing. The malocclusion models were particularly affected. Thus, impression scans performed with structured-light scanners cannot replace scans of positive casts for diagnostic use in orthodontics.


Assuntos
Arco Dental/anatomia & histologia , Técnica de Moldagem Odontológica , Interpretação de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Má Oclusão/diagnóstico por imagem , Fotografia Dentária/métodos , Técnica de Fundição Odontológica , Humanos , Aumento da Imagem/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
9.
J Orofac Orthop ; 76(4): 351-65, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26123733

RESUMO

OBJECTIVES: Digital jaw models offer more extensive possibilities for analysis than casts and make it easier to share and archive relevant information. The aim of this study was to compare the dimensional accuracy of scans performed on alginate impressions and on stone models to reference scans performed on underlying resin models. METHODS: Precision spheres 5 mm in diameter were occlusally fitted to the sites of the first premolars and first molars on a pair of jaw models fabricated from resin. A structured-light scanner was used for digitization. Once the two reference models had been scanned, alginate impressions were taken and scanned after no later than 1 h. A third series of scans was performed on type III stone models derived from the impressions. All scans were analyzed by performing five repeated measurements to determine the distances between the various sphere centers. RESULTS: Compared to the reference scans, the stone-model scans were larger by a mean of 73.6 µm (maxilla) or 65.2 µm (mandible). The impression scans were only larger by 7.7 µm (maxilla) or smaller by 0.7 µm (mandible). Median standard deviations over the five repeated measurements of 1.0 µm for the reference scans, 2.35 µm for the impression scans, and 2.0 µm for the stone-model scans indicate that the values measured in this study were adequately reproducible. CONCLUSION: Alginate impressions can be suitably digitized by structured-light scanning and offer considerably better dimensional accuracy than stone models. Apparently, however, both impression scans and stone-model scans can offer adequate precision for orthodontic purposes. The main issue of impression scans (which is incomplete representation of model surfaces) is being systematically explored in a follow-up study.


Assuntos
Alginatos , Antropometria/métodos , Materiais para Moldagem Odontológica , Técnica de Moldagem Odontológica , Imageamento Tridimensional/métodos , Arcada Osseodentária/anatomia & histologia , Ácido Glucurônico , Ácidos Hexurônicos , Humanos , Interpretação de Imagem Assistida por Computador/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
10.
J Orofac Orthop ; 75(4): 264-74, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24996855

RESUMO

BACKGROUND AND OBJECTIVES: Over recent years, we have witnessed a growing trend in orthodontics toward the use of three-dimensional (3D) techniques for diagnostic purposes, treatment planning, and fabricating appliances. This study was undertaken to compare the traditional manual technique of using vernier calipers to take orthodontic measurements on plaster dental casts versus an all-digital measuring technique based on virtual 3D scans of casts. In this study, we focused on the quantitative agreement between and time requirements of both methods. MATERIALS AND METHODS: Plaster casts obtained from the jaws of 55 fully dentate patients who had not previously undergone orthodontic treatment underwent 3D scanning using a white-light scanner (d-Station (3D); Breuckmann, Meersburg, Germany). Once the casts had been blinded by an independent individual, three examiners with different degrees of expertise in dentistry and orthodontics measured the mesiodistal widths of teeth 6-6 in each jaw. A randomized sequence was used when taking the measurements three times using OnyxCeph(3TM) analysis software (Image Instruments, Chemnitz, Germany) and a dental vernier caliper. Bland-Altman plots were used to illustrate the level of agreement between the two methods, standard deviations of repeated measurements were calculated to assess their reproducibility, and the Wilcoxon's signed-rank test was employed to compare their time requirements. RESULTS: The Bland-Altman analysis of all single values revealed no statistically significant difference between the software-based and caliper-based measurements of mesiodistal tooth width. Assuming the presence of normal distribution, the limits of agreement disclosed a 95% probability for the software values to range between +0.499 and -0.545 mm of the same value measured with the caliper. The standard deviations of repeated measurements were 0.33 mm with the software and 0.21 mm with the caliper. The digital method required significantly less time (p<0.01); however, differences were observed to be associated with operator experience. CONCLUSION: Inexperienced examiners, in particular, take measurements of mesiodistal tooth dimensions faster using a software-based method than when using a dental vernier caliper. Similar values were obtained with both methods.


Assuntos
Cefalometria/métodos , Técnica de Fundição Odontológica , Modelos Dentários , Imageamento Tridimensional/métodos , Mandíbula/anatomia & histologia , Ortodontia/métodos , Dente/anatomia & histologia , Humanos , Interpretação de Imagem Assistida por Computador/métodos , Variações Dependentes do Observador , Reconhecimento Automatizado de Padrão/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
11.
Psychophysiology ; 47(2): 299-314, 2010 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-20003170

RESUMO

Locations of surface electromyography (sEMG) electrodes in the face are usually chosen on a macro-anatomical basis. In this study we describe optimal placement of bipolar electrodes based on a novel method and present results for lower facial muscles. We performed high-density sEMG recordings in 13 healthy participants. Raw sEMG signals were decomposed into motor unit action potentials (MUAPs). We positioned virtual electrode pairs in the interpolated monopolar MUAPs at different positions along muscle fiber direction and calculated the bipolar potentials. Electrode sites were determined where maximal bipolar amplitude was achieved and were validated. Objective guidelines for sEMG electrode placement improve the signal-to-noise ratio and may contribute to reduce cross talk, which is particularly important in the face. The method may be regarded as an important basis for improving the validity and reproducibility of sEMG in complex muscle areas.


Assuntos
Eletromiografia , Face/inervação , Face/fisiologia , Músculos Faciais/fisiologia , Neurônios Motores/fisiologia , Fibras Musculares Esqueléticas/fisiologia , Adulto , Interpretação Estatística de Dados , Eletrodos , Face/anatomia & histologia , Músculos Faciais/citologia , Feminino , Humanos , Lábio/inervação , Lábio/fisiologia , Masculino , Adulto Jovem
12.
Clin Neurophysiol ; 119(1): 33-42, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18037342

RESUMO

OBJECTIVE: To present a motor unit number estimation (MUNE) technique that resolves alternation by means of high-density surface EMG. METHODS: High-density surface EMG, using 120 EMG channels simultaneously, is combined with elements of the increment counting technique (ICT) and the multiple-point stimulation technique. Alternation is a major drawback in the ICT. The spatial and temporal information provided by high-density surface EMG support identification and elimination of the effects of alternation. We determined the MUNE and its reproducibility in 14 healthy subjects, using a grid of 8 x 15 small electrodes on the thenar muscles. RESULTS: Mean MUNE was 271+/-103 (retest: 290+/-109), with a coefficient of variation of 22% and an intra-class correlation of 0.88. On average, 22 motor unit potentials (MUPs) were collected per subject. The representativity of this MUP sample was quantitatively assessed using the spatiotemporal information provided by high-density recordings. CONCLUSIONS: MUNE values are relatively high, because we were able to detect many small MUPs. Reproducibility was similar to that of other MUNE techniques. SIGNIFICANCE: Our technique allows collection of a large MUP sample non-invasively by resolving alternation to a large extent and provides insight into the representativity of this sample. The large sample size is expected to increase MUNE accuracy.


Assuntos
Eletromiografia , Potencial Evocado Motor/fisiologia , Neurônios Motores/fisiologia , Músculo Esquelético/citologia , Adulto , Idoso , Análise por Conglomerados , Estimulação Elétrica/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
13.
J Orofac Orthop ; 68(5): 377-96, 2007 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-17882365

RESUMO

BACKGROUND AND AIM: Quantitative knowledge of the three-dimensional (3D) force-moment systems applied for therapeutic tooth movement is of utmost importance, with regard to the predictability of the course of tooth movement, as well as the reduction of traumatic side effects. The concept of a smart bracket with an integrated sensor system for 3D force and moment measurement has recently been published. The feasibility of this approach has been demonstrated using finite-element (FE) simulations and a 2.5 times enlarged real smart bracket model. The aim of this study was to develop and to mechanically characterize the first wire-mediated, true-scale smart bracket. MATERIALS AND METHODS: A true-scale smart bracket was built using a stress-sensor chip (having a surface area of 2 x 2.5 mm(2)) and a conventional bracket slot. This bracket was calibrated on a biomechanical system for 3D application and measurement of forces and moments, then its measurement accuracy was evaluated. RESULTS: With the exception of the bucco-lingually-oriented force component, the embedded sensor system was capable of reconstructing the applied force-moment components with sufficient accuracy. The standard deviations for the differences between applied and inferred values were 0.07 N, 0.07 N and 0.26 N for the components F(x), F(y) and F(z), and 0.76 Nmm, 1.09 Nmm and 0.22 Nmm for the components Mx, My and Mz. CONCLUSIONS: We were able to construct true-scale, wire-mediated smart brackets. Work on improving the sensor system's buccolingual sensitivity is still in progress. Improved smart brackets with wire-mediated energy transmission could be applied in the near future in orthodontic training as an objective feedback tool, as well as in biomechanical research. Broad clinical application of smart brackets requires integration of telemetric components for data and energy transmission. Such components are now being developed. Future clinical application of smart brackets may contribute in reducing the negative side effects of fixed appliance therapy such as root resorption, while enhancing therapeutic efficiency.


Assuntos
Fenômenos Biomecânicos , Pesquisa em Odontologia , Análise de Elementos Finitos , Má Oclusão/terapia , Microcomputadores , Braquetes Ortodônticos , Fios Ortodônticos , Técnicas de Movimentação Dentária , Processo Alveolar/fisiopatologia , Remodelação Óssea/fisiologia , Desenho de Equipamento , Humanos , Má Oclusão/fisiopatologia , Ligamento Periodontal/fisiopatologia , Terapia Assistida por Computador/instrumentação
14.
J Orofac Orthop ; 68(2): 109-23, 2007 Mar.
Artigo em Inglês, Alemão | MEDLINE | ID: mdl-17372709

RESUMO

BACKGROUND AND AIM: The interrelation between retroclination of the maxillary central incisors and dentofacial parameters is a controversial subject in the literature. In contrast to comparisons between malocclusion and control groups, the objective of the present study was to identify skeletal, dentoalveolar or perioral (soft-tissue) factors which primarily determine how severely retroclination is individually manifested. MATERIALS AND METHODS: For this purpose we evaluated the pretherapeutic lateral cephalograms of 83 patients with an inclination of the maxillary central incisors ranging from physiological values to very severe retroclination (inclination to anterior cranial base between 104 degrees and 64 degrees ). A detailed analysis of the skeletal, dentoalveolar, and soft-tissue morphology was performed using lateral cephalograms taken prior to therapy. The statistical analysis included the calculation of multiple regression models for maxillary central incisor inclination and different parameters describing the lip-to-incisor relationship as dependent variables. RESULTS: A regression model including 1) the lip-line level measured at the dorsal upper-lower lip contact point, 2) the sagittal intermaxillary relationship, and 3) the inclination of the mandibular central incisors explained 81% of the variability in maxillary central incisor inclination (p < 0.0001 for all three parameters). Statistical analysis of the morphologic base of a high dorsal lip-line level (i.e., the predominant characteristic in the retroclination cases) revealed the significance of soft-tissue, dentoalveolar, and skeletal variables (p < 0.001). CONCLUSIONS: Complementary to results of previous resting lippressure measurements, this cephalometric study suggests that a high lip-line level is the predominant causative factor for a cover- bite or Class II, Division 2 malocclusion. Therefore, we conclude that (1) lip-line measurements should be included in routine cephalometric diagnostics, and (2) that a high lip-line must be eliminated by therapeutic measures in these malocclusions to prevent a post-orthodontic relapse.


Assuntos
Antropometria/métodos , Cefalometria/métodos , Incisivo/anormalidades , Incisivo/patologia , Má Oclusão Classe II de Angle/diagnóstico , Medição de Risco/métodos , Adolescente , Adulto , Criança , Feminino , Humanos , Masculino , Reprodutibilidade dos Testes , Fatores de Risco , Sensibilidade e Especificidade , Estatística como Assunto
15.
J Electromyogr Kinesiol ; 17(5): 535-48, 2007 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16904342

RESUMO

Recently, high-density surface EMG electrode grids and multi-channel amplifiers became available for non-invasive recording of human motor units (MUs). We present a way to decompose surface EMG signals into MU firing patterns, whereby we concentrate on the importance of two-dimensional spatial differences between the MU action potentials (MUAPs). Our method is exemplified with high-density EMG data from the vastus lateralis muscle of a single subject. Bipolar and Laplacian spatial filtering was applied to the monopolar raw signals. From the single recording in this subject six different simultaneously active MUs could be distinguished using the spatial differences between MUAPs in the direction perpendicular to the muscle fiber direction. After spike-triggered averaging, 125-channel two-dimensional MUAP templates were obtained. Template-matching allowed tracking of all MU firings. The impact of spatial information was measured by using subsets of the MUAP templates, either in parallel or perpendicular to the muscle fiber direction. The use of one-dimensional spatial information perpendicular to the muscle fiber direction was superior to the use of a linear array electrode in the longitudinal direction. However, to detect the firing events of the MUs with a high accuracy, as needed for instance for estimation of firing synchrony, two-dimensional information from the complete grid electrode appears essential.


Assuntos
Potenciais de Ação/fisiologia , Algoritmos , Diagnóstico por Computador/métodos , Eletromiografia/métodos , Neurônios Motores/fisiologia , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Adulto , Humanos , Masculino
16.
Angle Orthod ; 76(6): 942-9, 2006 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-17090163

RESUMO

OBJECTIVE: To investigate the impact of a persisting high lip line and other potential relapse-inducing factors on long-term stability of orthodontic correction of retroinclined maxillary central incisors. MATERIALS AND METHODS: Thirty-one cover-bite ("Deckbiss") patients with retroinclined maxillary central incisors and a deep frontal overbite were evaluated. The maxillary central incisor inclination was determined odontometrically with study models made pretreatment, posttreatment, and at a follow-up examination (mean posttherapeutic interval: 9.0 years). The lip-to-incisor relationship, the interincisal angle, and the anteroposterior maxillary central incisor position were measured on lateral cephalograms taken after active treatment. RESULTS: The relapse tendency of the orthodontic correction of the retroinclined maxillary central incisors displayed great interindividual variability with a range of posttherapeutic inclination change of -6.75 degrees to +8.00 degrees. Multiple regression analysis revealed an increased tendency for relapse in patients with (1) a high posttherapeutic (dorsal) lip line level combined with the maxillary central incisor and lower lip contact only in the incisal crown area (P < .01) and (2) a marked therapeutically induced inclination change of the maxillary central incisors (P < .05). Interrelations between the relapse of the corrected maxillary central incisors and other evaluated parameters were not statistically significant. CONCLUSIONS: For maximum treatment stability, the elimination of an excessive overlap of the upper incisors by the lower lip should be regarded as one of the most important therapeutic objectives when treating this malocclusion.


Assuntos
Incisivo/fisiopatologia , Lábio/anatomia & histologia , Má Oclusão Classe II de Angle/terapia , Adolescente , Adulto , Cefalometria , Criança , Feminino , Humanos , Masculino , Má Oclusão Classe II de Angle/patologia , Odontometria , Recidiva , Análise de Regressão , Reprodutibilidade dos Testes , Estatísticas não Paramétricas
17.
J Neurophysiol ; 95(1): 342-54, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16000526

RESUMO

The objective of this study was to systematically characterize motor units (MUs) of the musculature of the lower face. MU endplate positions and principal muscle fiber orientations relative to facial landmarks were identified. This was done by the analysis of motor unit action potentials (MUAPs) in the surface electromyogram. Thirteen specially trained, healthy subjects performed selective contractions of the depressor anguli oris, depressor labii inferioris, mentalis, and orbicularis oris inferior muscles. Signals were recorded using recently developed, 0.3-mm thin and flexible high-density surface electromyography (sEMG) grids (120 channels). For each subject and each muscle and for different low contraction levels, representative MUAPs ("MU fingerprints") were extracted from the raw sEMG data according to their spatiotemporal amplitude characteristics. We then topographically characterized the lower facial MUs' endplate zones and main muscle fiber orientations on the individual faces of the subjects. These topographical MU parameters were spatially warped to correct for the different sizes and shapes of the faces of individual subjects. This electrophysiological study revealed a distribution of the lower facial MU endplates in more or less restricted, distinct clusters on the muscle often with eccentric locations. The results add substantially to the basic neurophysiologic and anatomical knowledge of the complex facial muscle system. They can also be used to establish objective guidelines for placement of conventional (surface or needle) EMG electrodes as well as for clinical investigations on neuromuscular diseases affecting the facial musculature. The localized endplate positions may also indicate optimal locations for botulinum toxin injection in the face.


Assuntos
Potenciais de Ação/fisiologia , Eletromiografia/métodos , Neurônios Motores/fisiologia , Neurônios Motores/ultraestrutura , Contração Muscular/fisiologia , Fibras Musculares Esqueléticas/citologia , Fibras Musculares Esqueléticas/fisiologia , Adulto , Algoritmos , Feminino , Humanos , Masculino , Músculo Esquelético/anatomia & histologia , Músculo Esquelético/fisiologia
18.
J Orofac Orthop ; 65(6): 475-88, 2004 Nov.
Artigo em Inglês, Alemão | MEDLINE | ID: mdl-15570406

RESUMO

BACKGROUND AND AIM: Cover-bite ("Deckbiss") is regarded as a highly relapse-prone malocclusion. In this context the great significance of a high lip line (LipL) as an etiologic factor for the retroclination of the upper central incisors was recently proven within the framework of lip pressure measurements. It therefore seemed likely that a persisting high LipL after correction of cover-bite might have an equally negative impact on the stability of the treatment outcome. MATERIALS AND METHODS: This issue was investigated in the present retrospective study by cephalometric analysis of the findings prior to therapy (T1), immediately after active mechanotherapy (T2), and after a mean follow-up period of 2 years (T3). The study group consisted of 40 former cover-bite patients with initial linguoversion of the upper central incisors (axial angle to anterior cranial base < 98 degrees ) and anterior deep bite (> or = 4 mm) from the records of the Department of Orthodontics, University of Freiburg i. Br., Germany. RESULTS AND CONCLUSIONS: The average relapse was ca. 20% of the total correction of the anterior linguoversion and deep bite, with the relapse tendency, however, displaying substantial interindividual variations. Multiple regression analysis revealed an increased relapse tendency in specific cases: patients with maxillary extractions, cases with a pronounced therapeutically induced change of upper central incisor inclination, and patients with a high post-therapeutic LipL or with poor compliance in the retention phase. In view of the relatively good opportunity to influence the level of the LipL therapeutically, one of the most important therapeutic objectives for cover-bite patients should be to reduce the amount by which the lower lip overlaps the upper incisors ( to a maximum value of 3 mm). This can be achieved by active mechanical intrusion of the upper incisors. If the orthodontist fails to take account of this aspect when planning or performing the treatment, he has to accept an increased risk of relapse.


Assuntos
Cefalometria/métodos , Má Oclusão/diagnóstico por imagem , Má Oclusão/prevenção & controle , Ortodontia Corretiva/métodos , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Medição de Risco/métodos , Falha de Tratamento , Adolescente , Adulto , Criança , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Risco , Prevenção Secundária , Índice de Gravidade de Doença , Resultado do Tratamento
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