摘要:

SummaryThis study was prompted by the hypothesis that the contractile power of the masseter and medial pterygoid muscles influences not only the shape of the gonial angle of the mandible into which these muscles insert, but also that they play a major part in determining the amount of free‐way space present in any individual.Tracings were made from the lateral cephalograms of 130 dentate subjects and the gonial angle measured in each case. Free‐way space was also measured, using a dakometer, and the paired values subjected to statistical analysis. A strong inverse correlation was found to exist, indicating that throughout the sample a decrease (or sharpening) of the gonial angle is accompanied by a predictable increase in the free‐way space. By applying the processes of linear regression to the paired results, a formula was obtained which may be used to predict the best value of one variable for any given value of the other. Thus, in an edentulous case, where the value of the free‐way space measurement is unknown, a method is provided for predicting its best value by the determination of the patient's gonial angle through cephalometric a

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1983.tb00123.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryA mathematical simulation of the Denar D4A articulator and a simulated complement of graphically represented teeth were programmed in a Prime 4000 minicomputer. The computer program could be manipulated to quantitatively evaluate the theoretical effects of changes in articulator and control factors on the anatomy of selected teeth or tooth groups. The effects of these changes could be assessed graphically and numerically and data could be manipulated statistically.

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1983.tb00124.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryThree laboratory studies were carried out with the aim of improving or streamlining enamel surface treatment procedures in fissure sealing.In Study 1, the effect of reducing acid etch time from 60 s to 10 s was assessed by SEM and tensile bond strength measurements. Reduction in etch time produced a finer etch pattern, gave a reduced but still high, bond‐strength, albeit with slightly poorer long‐term adhesion.Study 2 showed that a conventional acid etch treatment could completely remove acquired pellicle, without prior prophylaxis. SEM studies and bond‐strength measurements corroborated this view.In Study 3, compressed air and chemical drying agents were compared for drying speed and efficiency. Compressed air gave more rapid, thorough drying, and greater resultant bond stre

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1983.tb00125.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryLight reflectivity, scattering coefficient, absorption coefficient, infinite optical thickness, and contrast ratio were determined in white light, for seven shades of a conventional composite and five shades of a microfilled composite, from reflection spectrophotometric data using Kubelka's equations. Significant differences among shades were observed for each property. Values of infinite optical thickness ranged from 2–97 to 5–90 mm among the shades stud

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1983.tb00126.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryThe long‐term dimensional stability of three non‐aqueous elastomeric impression materials, a silicone, a polyether and a polysiloxane, were investigated. The testing apparatus was an A.D.A. specification No. 19 test block and mould. The impressions were measured by the use of a travelling stage reflecting microscope and a Quantimet 720 Image Analyzing computer at time zero and again at 4, 24 and 48 h, and at 1, 2, 3 and 4 weeks.Impressions poured immediately had the greatest accuracy for all the materials. The polysiloxane (0.025 mm) and polyether (0.033 mm) showed very little change in dimension after 4 weeks when compared to the test block. However, the silicone showed significant change at 4 h (0–14 mm) and 0–2 mm after 4 weeks. After 4 weeks the polysiloxane maintained the best surface detail, the polyether was adequate but the silicone lost much of its detail in as little as 24 h. The reasons for these findings are di

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1983.tb00127.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryThe interdental dimension discrimination (IDD) ability was tested at seven different degrees of mouth opening: 40 mm, 30 mm, 20 mm and 10 mm openings for the dentate subjects, and 10 mm opening, intercuspal position (ICP) and the ICP minus 5 mm for the edentulous subjects. The subjects were asked to discriminate between pairs of sticks held alternately between the upper and lower incisors. The IDD ability, evaluated in terms of the 50% difference limen (DL), did not differ significantly between any two of the tests conducted at seven different openings, although the number of misjudgments of the dentate subjects tended to increase with the degree of mouth opening. On the other hand, the directional specificity of the IDD, which is a tendency to overestimate the dimension of the first stick of each pair, developed almost linearly with a decrease in the opening degree. These findings indicate that the behaviour of the receptors concerned varies with the intermaxillary distance. Some edentulous subjects could not perceive the presence of a small test stick at the overclosed position (ICP ‐ 5 mm), but vibration applied to the mandible enabled the subjects to detect the stick at the same opening. These results support the assumption that the muscle spindles of the jaw‐closing muscles are the receptors responsible for the

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1983.tb00128.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryEarlier work revealed that creep of a particular dental amalgam can be described by the modelF(t)=F0exp (t/t0)m. HereF(t) is the creep compliance at timet, whereasF0,t0andmare constants of the model. In the previous study only three alloys were used. It was the aim of this study to investigate the factor alloy more thoroughly. After specimen preparation, the nineteen different amalgams were aged at 37°C for either one day or one week. Then creep was determined at a temperature of 22.5°C and a compressive stress of 117 MN/m2.F0turns out to depend upon both the ageing time as well as on the choice of the alloy. As expected,t0shows up substantial differences between the respective amalgams, whereas the differences between the two ageing are absent or relatively small. The factor alloy significantly influencesm. However, the ageing time exerts no significant influence upon

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1983.tb00129.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryThis paper explores seven different factors which should be considered when prescribing the lower anterior prosthesis: alignment as seen from the incisal; height of the incisal edges; degree of irregularity of the teeth; character of the incisal edge; height of the cuspid; mesio‐incisal angle of the cuspid; and ridge coverage. The weights and variations of these different factors are discussed and suggestions made for a complete work authorizatio

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1983.tb00130.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryThe final composition of the size of particles of food or the swallowable composition (SC) has been investigated in subjects with different types of dentition. A convenient mouthful of hard‐baked soya beans was masticated and thereafter the bolus was dried, sieved and weighed. Full denture wearers prepared a SC with a mode value around 4000 μm whereas subjects with mixed dentition prepared a SC with a mode value around 2000 μm. Subjects with partial dentition produced wide variations in the SC. To produce a SC which is usually swallowed by a particular subject the quantity of masticated food should bear an optimum ratio to the area of the healthy oral tiss

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1983.tb00131.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

SummaryThe cytotoxic effects of zinc phosphate and silicate cements, Concise composite and zinc oxide/eugenol were evaluated after 24 h in anin vitrosystem which simulates the clinical usage of the material, and the results compared with those using phenol. Data of gross changes affecting cell viability placed these materials in ranking order of increasing severity: Concise

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1983.tb00132.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY