摘要:

It is generally thought that during symmetrical jaw opening the mandible rotates about an axis passing through the centres of the two mandibular condyles, and translates down the articular eminence. The author argues that there are no data to support this assumption. The true combination of movements can only be understood by understanding the constraints that operate during jaw opening and these are the articular eminence and the temporomandibular (TM) ligament. The TM ligament is pulled taut during jaw opening, and so acts like the chains of a swing: the mandible rotates about the lowest attachment of the TM ligament to the condyle and swings about the most posterior attachment to the articular tubercle. The effects of combining the swing and rotation are demonstrated by a simple mechanical model. The functional advantage of the TM ligament is that it keeps the condyle close to the temporal bone during jaw opening, until the condyle passes under the articular eminence. The constraints described in this paper may have important implications related to the diagnosis and treatment of some disorders of the TM joint (to be described in a later paper).

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1989.tb01348.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Bond strengths for the retention of ceramic bonded to metal alloys to the tooth structure involve cavity preparation variables, cement variables and ceramic bonded to metal alloy variables. The aim of this work was to evaluate the retentive strength differences between alloy surfaces, unfired and fired, for porcelain alloys retained with different dental cement compositions. The clinical situation was simulated by using standardized tooth preparations, extracted teeth and castings cemented with zinc phosphate and polycarboxylate cements, which were debonded on an Instron. Jelenko O, Cameo, Jelstar and Genesis II alloys were compared unfired and fired to simulate porcelain application. Fired Jelenko O casting alloy cemented with polycar‐boxylate cement produced the greatest bond strength (6.0±1.0 MPa). Polycarboxylate cemented castings had greater bond strengths for all alloys whether fired or not. The only effect of firing was an improvement with Jelenko O alloys produced with, both cements. All of these differences were statistically significant at the P<0.01 level using Tukey's post hoc evaluation. The improvements observed were related to the oxide formation on the internal surfaces of the casting and the ability of polycarboxylate cement to adhere chemically to those laye

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1989.tb01349.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In ninety‐six patients with oro‐facial and general complaints, which the patients assumed were caused by galvanic currents and/or metallic restorations, the recording and analysis of dietary pattern, energy and nutrient intake were performed. The records, in household measures, of the intake of food and beverages during 7 consecutive days according to a written instruction were collected. Sixty‐eight out of the ninety‐six records were sufficiently complete for calculation of nutrient intake. The remaining twenty‐eight could only be used partially in the analyses.Most of the patients had a varied food intake of all the food groups during the 7‐day period. The range was wide, however, and a few patients had relatively low intake of essential nutrients. It was not possible to find any correlation between oro‐facial discomfort complaints and intake of any single nutrient that could indicate a cause‐effect relationship. No correlation between diet pattern, energy and essential nutrients, and the measured electrode potentials of the fillings and constructions could be proved. Nor could the hypothesis that beverage intake might influence the electrode potentials and increase or aggravate the oro‐facial compl

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1989.tb01350.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

This paper describes the development of an instrument for determining consistency, working time and setting time of elastomeric impression materials. The operating principle involves the application of a fixed compressive strain and the resulting stress is measured. This instrument has been called a Comprheometer. Temperature control is achieved by water circulation so that simulated room or open‐mouth temperatures can be used. Values of consistency and working time are presented for a range of elastomeric materials at room temperature. Also, setting times determined under oral conditions are recorde

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1989.tb01351.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Two hundred and twenty‐two patients who had been examined and treated for craniomandibular disorders were re‐evaluated using a screening protocol. This protocol was developed from previous studies which had elucidated the most reliable signs and symptoms of craniomandibular disorders. Unilateral signs and symptoms were found to be more common than bilateral signs and symptoms. Dynamic and static pain tests were shown to be decisive in determining the preliminary diagnosis. There was a significant difference in vertical condylar height asymmetry between those patients diagnosed as having a myogenous and an arthrogenous origin of p

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1989.tb01352.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

A new method has been devised to measure masticatory ability. Pigment‐coated granules were prepared, and 730 mg (730–740 granules) were sealed in a rubber capsule. This capsule was used as a test material and was chewed by the subject under standardized conditions. The masticatory ability, defined as the joules of work performed, was calculated based on the concentration of pigment leaked from the crushed granules during the process of mastication. The procedure is rapid, simple and reliable, and can be used for a large number of clinical samples and studies. The measurement error, defined as the coefficient of variation, was 2.1%. The intraindividual variation of measurements of twenty volunteers ranged from 3.6 to 16.9%. A series of tests in each subject was necessary to obtain a reliable value of masticatory abil

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1989.tb01353.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Based on data from patient records from a random sample of Dutch general practices, a study was made of the bridge distribution pattern in different patient groups. Patient variables such as age, sex and insurance type were analysed. More women had a bridge inserted than men. However, there appeared to be no difference in the average quantity of bridges in men or women. The abutment teeth most frequently used were the cuspids in the maxilla and the second premolars and second molars in the mandible. Fourteen per cent of the bridges consisted of five or more units, 14% were free‐end bridges, 13% did not meet Ante's law and 16% had one or more non‐vital abutment te

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1989.tb01354.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The longevity of dental restorations is an important health concern for the patient, the dentist, and the various forms of insurance systems. In this article several methods of evaluating survival time are described and the different ways of presenting the findings of survival studies are discussed. It is stated that only longitudinal studies are appropriate to give an exact insight in the longevity of restorations. A large amount of information is available in dental records and the way these data can be analysed is presented in this paper. It appears that Cox's proportional hazard model is the appropriate way of demonstrating the influence of several factors on the survival rate. An example is provided of the results from a recent survival study of crowns in The Netherlands.

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1989.tb01355.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Mandibular movement that occurred after initial tooth contact in a rhythmical tooth‐tapping task was investigated using a closed‐circuit television movement detector. Tooth contact was monitored by the placement of a small microphone on the subjects' foreheads. Movement was traced on ultraviolet‐sensitive chart and a statistical method of analysis was developed to determine movement patterns at the commencement and cessation of each cycle. Results showed that a regular pattern of movement could be observed as a cycle of movement commenced, but that this was not so apparent on cess

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1989.tb01356.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In the comparison of radiographical findings (flattening, irregular surface and osteophyte formation) between lateral tomography and Orthopantomography(r) in thirty‐one female patients with craniomandibular disorders, a 76% similarity was found. A trend in the findings was seen: with an increase in radiographical findings visible in the tomograms there is a decrease in the amount of condylar asymmetry visible in the Orthopantomograms(r) and a decrease in the age of the patient

ISSN:0305-182X    

DOI:10.1111/j.1365-2842.1989.tb01357.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY