摘要:

The feasibility of examining electro‐mechanical activity of the human masseter muscles using non‐invasive recording techniques was examined in six healthy dentate adults (aged 34‐57 years). Electrical activity of the muscle was examined by surface electro‐myography (EMG) and the mechanical activity, in the form of muscle sounds, was examined by acoustic myography (AMG).Bilateral recordings of EMG and AMG were made simultaneously using composite probes which were placed on the skin over the masseter muscles. A standardized pressure was applied to the probes via adjustable rods attached to a safety helmet. Pressures were monitored by strain gauges placed between the ends of the rods and the probes. With the subject seated, recordings of AMG and EMG were obtained during maximal jaw clenching for 4s and the raw signals were stored on a computer. Of three maximal contractions performed, the last two were used in the analysis. The raw amplified signals underwent frequency analysis by fast Fourier Transform. Total activity was also assessed after amplification, full‐wave rectification and integration, and repeatability of the results was assessed.The AMG frequency range was 6‐15 Hz and was similar to values for other human skeletal muscles. The integrated values for EMG and AMG were repeatable on both sides of the face (IEMG, right r = 0.99, left r = 0.99; IAMG right r = 0.70, left r = 0.71). Simultaneous recordings of AMG and EMG from the masseter muscles may be useful for assessing electro‐mechanical muscle function but further validation studies are required before the technique can be us

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01618.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The bases of occlusal rims and trial dentures should fit both the cast and the mouth accurately. The retention of shape and dimension of strips and sheets of grey and pink shellac, filled cold cure acrylic resin and wax were tested following moulding over stylised upper edentulous casts. The thermoplastic materials were softened over a flame or in a water bath. Specimens were prepared with and without folding along the long axes of the strips. The angles formed by the strips, the gap between the palate of the baseplates and casts and the linear dimension of the sheets were measured after moulding, after immersion in water at 37 and 45°C and after 24 h at room tmperature. The least angular change was shown by unfolded grey shellac, softened over a flame and moulded by finger pressure over an unwarmed cast, followed by folded specimens softened in water and moulded with the fingers over a prewarmed cast. The least gap developed beneath pink shellac softened in water and moulded by finger pressure over a warmed cast. The smallest dimensional change was shown by grey shellac softened in water and moulded by finger pressure over a warmed cast. Thus, optimally manipulated shellac materials exhibit less change after moulding than cold cure acrylic resin or modelling wax

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01619.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

This was an investigation to determine the feasibility of an autoregressive (AR) model for establishing characteristic parameters from recorded occlusal sounds and develop their classification. Thirty four normal subjects with intact natural dentitions were selected for the study. The subjects’ occlusal sounds from both sides of their faces respectively were sampled, and the gnathosonic classification (Class A, B and C) was established by observing the original recorded wave pattern and measuring the duration. Then, a 20 order AR model was calculated with the collected data, and the AR model coefficients were found to be similar to the indices of Bayes’ discriminatory analysis. The total conformation rates of the modelled left and right occlusal sounds to the classification, estimated by Bayes’ discriminant functions were 97.06% and 88.24% respectively. AR coefficients representing the characteristics of human occlusal sounds can be helpful in their classification and allow computer diagnosis of occlusal diso

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01620.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Three techniques have been used to assess the shear rate dependence of the viscosity of mixed alginate impression materials prior to setting. Two methods used a cone‐plate viscometer, and one method was a capillary extrusion technique. Data from the three sets of experiments have been critically compared. It has been shown that an unset alginate material exhibits Bingham behaviou

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01621.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The purpose of this study was to examine longitudinal changes of the occlusal force distribution in lower distal‐extension removable partial dentures with the conus crown telescopic system. Occlusal force applied to the denture and forces transmitted to the retainers were measured on several separate occasions from the insertion of new dentures to about 3 months after. The occlusal force distribution ratio to the retainers was calculated when a load of 20N was applied to the denture.The results are summarized as follows:(i) The more posterior the loading point of occlusal force, the smaller was the ratio. When the occlusal force was applied to the most anterior artificial tooth, the ratio was 65‐100% of the occlusal force.(ii) As the denture wearing time proceeded, the ratio was decreased. The smaller the ratio, the greater was the rate of its d

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01622.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

An historical review of the general uses of shellac is presented and the various manufacturing processes, properties and chemical composition are discussed. The applications, advantages and disadvantages of shellac and its uses in dentistry are outlined.

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01623.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Taurodontism and a reduced tooth length are reported to occur in patients with oligodontia. The aim of this study was to evaluate the occurrence of these factors in Dutch patients with oligodontia.Panoramic radiographs of 117 patients with oligodontia and 91 controls were collected. Taurodontism of the mandibular first molars was recorded and the length of cuspids, bicuspids and first molars of the mandible were measured. In patients with oligodontia 28.9% showed taurodontism of one or two mandibular first molars. The prevalence of taurodontism in normal Dutch subjects was 9.9%. No significant differences were found between the two sexes in both groups. Neither was there a significant difference in the unilateral and bilateral occurrence of taurodontism. The present findings supported the hypothesis that taurodontism may be the result of an ectodermal defect and a manifestation of developmental instability in patients with oligodontia. The length of mandibular cuspids and first molars in females were significantly reduced. In males only the lower right first molar was significantly reduced. The reduced length of the teeth may also be the result of a defect in ectodermal cells. Both taurodontism and a reduced length are of importance considering dental therapy.

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01624.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Cases demonstrating complications in osseointegrated implant supported prostheses are described. These complications occurred in the prostheses framework or veneer, in the fixation screw, in the abutment post or screw as well as in the implant body. The two main reasons for the complications were lack of passive fitting between the restoration and the abutment; and destructive occlusal contacts. The destructive occlusal contacts may develop during the time of wear of the prostheses material or by changes in the opposite restoration. Overloading or bending moments exerted on the prostheses via these occlusal contacts resulted in loosening or fracture in one of the implantprostheses components. The benefit of acrylic resin or composite material in reducing stresses in the light of the possible long‐term, harmful occlusal changes that might develop as a result of their wear should be considere

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01625.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The fracture toughness of five different resin‐based inlay/onlay materials was investigated by means of critical stress intensity factor (KIC) using the SEN three‐point bending test procedure (BS 5447: 1977). KICvalues were determined from specimens prepared by both the direct and indirect techniques. Tests were performed immediately, after 1 day, 1 month and 3 month time intervals. Also, fractured surfaces of specimens were observed using SEM photogra

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01626.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

The digastric motor responses in the unloading reflex were investigated in a sample of 10 younger and eight older dentate subjects. The occurrence of the pre‐collapse digastric activity (PDA) and the reflex events (burst of activity) following the mandibular unloading (DB) were studied separately. PDA was nearly consistent in half of the subjects of both groups. DB was clearly identified in 60% of the younger subjects, but in 54.2% of the older subjects. The mean latency of DB found in the younger subjects was 32.4 ± 9.5 ms but 34.5 ± 8.8 ms in the older subjects. For the latencies found we can infer that they are related to polysynaptic pathways. Also a slight tendency for decreased frequency of occurrence and increased latencies of DB is observed in the older age gr

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1993.tb01627.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY