摘要:

SummaryParameters of mastication, such as mandibular displacement, velocity and chewing cycle duration, were investigated in relation to age and rehabilitation with complete dentures. Two groups of elderly subjects (mean age 80 years), one with natural dentition and the other with complete dentures, and one group of young dentate adults (mean age 26 years) participated. Three‐dimensional records of masticatory mandibular movements were obtained using the Selspot movement analysis system.There were no differences in the duration of the total or individual components of a chewing cycle, except for the closing phase, which was significantly longer in the complete denture group. Mandibular closing velocity was significantly lower in the two groups of elderly subjects than in the group of young adults. There was a high degree of inter‐individual variation in mandibular displacement in all groups, but the mean vertical amplitude was smaller in the elderly groups compared to the group of young adults. For many of the parameters the variation was significantly greater in the groups of elderly subjects than in the younger group. Ageing thus appeared to have a more important effect than the state of the dentition on the parameters stud

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1991.tb00024.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryMarginal microleakage was measured around amalgam restorations lined with alloyglass ionomer cement and coated with a glass ionomer varnish. Preparations were made in 48 human extracted mandibular molar teeth. Alloy‐glass ionomer liners and varnishes were placed into selected preparations. Tytin amalgam was inserted into all of the teeth and left unburnished and unpolished. Half of the total samples were thermocycled for 5 days and the remainder were left in deionized water. The teeth were immersed in a 0.5% methylene blue dye and sectioned vertically with a diamond saw. Microleakage was scored visually at xl00 magnification, and the data were analysed using the Mann‐WhitneyU‐test (P≤0.05). Thermocycling did not have a significant effect on microleakage, except when both an alloy‐glass ionomer liner and varnish were used. Overall, the use of an alloy‐glass ionomer liner made the most significant difference in reducing m

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1991.tb00025.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryWithout artificial feedback control, maximum voluntary isometric contractions were performed for about 1 s by six subjects. Randomly selected surface electromyograms of the anterior temporalis and masseter muscles suggested that, in some cases, the motor control of the entire isometric contraction might have been preprogrammed through the phenomenon of anticipation. In the majority of cases, the control of the initial contraction phase might have been preprogrammed, followed by a phase of servo‐controlled motor activity. As a functional basis for the servo‐control of isometric force generation, it was suggested that compartmentalized ‘extrafusal and intrafusal motor units’ were recruited and decruited in an orderly manner, and periods of alphamotor inhibition were interpreted as signs of switching from one control scheme to another, possibly via a transcortic

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1991.tb00026.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryThe effect of acid etching on the surface appearance and flexural strength of four glass polyalkenoate cements was investigated. Specimens were etched for intervals of 10–60 s, both at the recommended time after mixing and after a 24‐h delay. The surface texture was examined microscopically. Further specimens were subjected to a 4‐point bend test following etching 1 h and 24 h after mixing. Deterioration of the surface appearance occurred as the etching time was increased beyond 10 s following immediate etching. Etching after 24 h reduced surface damage, but a 10‐s etch still gave the most favourable surface appearance without loss of particulate material.Etching beyond 10 s significantly reduces flexural s

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1991.tb00027.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryThe accuracy of two different techniques for locating casts in the intercuspal position (ICP) in a semi‐adjustable articulator was assessed. The techniques for establishing the ICP were a polyether interdental registration, or location of the casts in a position of maximum interdigitation using tactile and visual methods.Fifty‐three sets of study models were used in this investigation. Each set of study models was mounted on two occasions, once with each of the two techniques. The models were divided into two groups at random, and mounting and assessment procedures were performed using a single blind crossover design. The quality of the contacts between the mounted casts was compared with the results of an occlusal examination of the same subjects.Hand articulation of the casts prior to mounting the lower cast against the upper cast was a more accurate means of locating the ICP than the use of a low‐viscosity polyether interdental registration material, unless there were difficulties in establishing the ICP by visual and tactile me

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1991.tb00028.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryThe relationship between number, distribution and intensity of occlusal tooth contacts and the craniomandibular functional status was investigated in 56 subjects aged 16–17 years. The photocclusion technique was used for the qualitative and quantitative evaluation of occlusal contacts, and a clinical examination was performed to assess the function of the stomatognathic system. According to a matched‐pairs design two groups were formed, one consisting of individuals with signs of craniomandibular disorders, and the other consisting of functionally healthy adolescents. The pairs were matched according to morphological occlusal characteristics.The results of the present study emphasize the importance of occlusal contacts in relation to craniomandibular function. In particular the posterior occlusion appeared to be related to function, since statistically significant differences between the two groups were detected with regard to the number and load of contacts. Symmetry of intensity rather than symmetry of contact distribution per se seemed to be important in relation to craniomandibular funct

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1991.tb00029.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummarySilicone negative replicas of dentine islands exposed by occlusal attrition were examined on extracted human teeth using the scanning electron microscope. Because the details of the dentinal tubules were reproducible on the silicone impression, the replication technique was appliedin vivoto occlusal attrition to demonstrate patent dentinal tubules in cases with symptomatic exposed dentine islands.Using this replication technique, it should be possible to monitor the effect of the therapeutic management of symptomatic tooth attrition on dentinal tubule closure.

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1991.tb00030.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryMandibular reaction time was measured in young and elderly volunteers. Each subject was instructed to open the jaw from the closed position and to close the jaw from the open position as quickly as possible after perceiving an auditory or visual signal. The reaction time of the elderly subjects to both signals was significantly slower than that of the young subjects. This was due almost entirely to prolongation of the premotor time component. There was no difference in the maximum velocity of the jaw movement between the two groups of subjects.

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1991.tb00031.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryAn experimental psychological study was undertaken to assess the effect of a change in dietary habit upon behavioural development, using as a laboratory animal male Wistar rats maintained on natural foods and a processed food. Forty male Wistar rats were weaned at 21 days of age and divided into two equal groups. Group 1 was fed natural food (pressed wheat, dried fish, peanuts, cabbage and soybeans) and group 2 was fed powdered food. At 68 days of age, the rats were tested in a T‐maze. The results showed that Group 1 excelled with regard to T‐maze learn

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1991.tb00032.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

SummaryThe surface characteristics of the articulating surfaces of 11 human mandibular condyles removed post‐mortem were determined by the use of reflected light dark‐field microscopy. Good agreement was obtained between macroscopical grading of degenerative change and appearance as observed by microscopy. Microscopical appearances believed to correspond to normal surface, fibrillation and degenerative changes are descri

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1991.tb00033.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY