METHOD FOR THE CONSTRUCTION OF A HUMAN PROSTHESIS, AND DEVICE SUITABLE FOR THE APPLICATION IN THE METHOD

Abstract: Method for the construction of a human prosthesis to be used for partially or totally removing a physical disfunction through determination of the preferred value of a parameter serving the patient's optimum comfort being characteristic for the removal of the disfunction by drawing a judgment from the patient regarding the parameter characterizing values, which values in a number sufficient for statistical analysis, are presented to him as a series of increments randomly varying with about the perceptive precision, whereafter the preferred value is calculated and the prosthesis is constructed using the calculated preferred value, wherein the composition of the series of randomly varying values for the calculation of the preferred value is completely microprocessor-controlled and is chosen from a series of values spanning across the preferred value; the values relevant for the calculation of the preferred value are administrated and said preferred value is calculated.

Description: -i- METH00 FOR THE CONSTRUCTION OF A HUMAN PROSTHESIS, AND DEVICE SUITABLE FOR THE APPLICATION IN THE METHOD, The invention relates to a method for the construction of a human prosthesis to be used for partially or totally removing a physical dysfunction through determination Of the preferred value of a parameter serving the patient's optimum comfort and being characteristic for the removal of the dysfunction by - drawing a judgment from the pa . tient regarding the parameter characterizing values, Which values s .in a number s-ufficient for statistical analysis, are presented, to him as a series of increments randomly varying with about the perceptive precision, whereafter the preferred value is calculated and the prosthesis is constructed using the calculated preferred value. Such a process for edentulous patients is investigated by van Willigen, De Vos and Broe huysen and reported in J. Prosthet. Dent. 35 (1976) 259-266. Durinq this investigation it appeared that the so-called "forced choice" method was the most suitable one for said method. For the investigation of the preferred vertical dimension of occlusion as the characteristic parameter use was made of an assembly, comprising a lower baseplate and an upper baseplate made from a synthetic resin material, each of them formed according to the relevant mouth parts (upper jaw wall arid palate and lower jaw wall respectively) of the patient. At the front side a micrometer screw was mounted in the middle plane of the lower baseplate and abutting against a platform secured to the upper baseplate. In order to determine the preferred vertical dimentioπ - of occlusion (PVDO) the assembly comprising the upper and the lower baseplate were placed in position in the patient's mouth. The above-mentioned "forced choice" method comprises offering the patient a random choice of vertical dimensions of occlusion, measured in increments of 0,5 mm ranging from 0,5 to 6 mm by correspondingly adjusting the micrometer. The highest and the lowest value of the measuring range corresponded to the experience of respecively "too high" and "too low" as criterion for the desired occlusion for the prosthesis. Care has been taken that within the random series each presentation of vertical occlusion occurs five times so that a total of 60 measurements "■ was carried out. The patient was instructed to comment on each presentation of the vertical occlusion as either "too high" or "too low". In between two subsequent measurements the time interval was 10 seconds. Each experiment was repeated five times in the course of five weeks. The results of the measurements so obtained were subjected to a statistical analysis for the calculation of that value of the vertical occlusion to which the measuring, results were converging. This value corresponds to the PVDO wanted. With the "forced choice" method the accuracy of the PVDO to be determined appears to be in a range of 0,5 to 1,5 mm, with an average of 1 mm. Moveover with the experiment a relation could be determined in that the patients who were able to come to an accurate indication of their PVDO within a short measuring period also showed reproducable indications when measurements were carried out over longer periods. With the so obtained PVDO a dental prosthesis can be constructed in a normal way. Object of the invention is a method for the construction of human prosthesis " as decrϊbed in the above within the scope of which the step of determining the preferred value of a parameter being characteristic for the prosthesis is improved i.e. is more rapid and more accurate. The invention is characterized in that the composition of the series of randomly varying values for the calculation of the preferred value is completely microprocessor-controlled and is chosen from a series of values spanning across the preferred value; the values re evant for the calculation of the preferred value are administrated and said preferred value is calculated. By having the composition of the random series of the gauges to be presented to the patient for the determination of the wanted parameter being icroprocessor- controlled, there is offered the possibility to exclude the influence of other persons than the patient's, such as the physician, dental surgeon, or orthopaedist so that the number of sources of error is limited to a minimum. Moverover the method according to the invention provides the possibility to iπeorporate the microprocessor-controlled system based on which the random series of the relevant measuring values is composed, in a device the operation of which being so much simpl fied that it may even be left to not-university trained persons. The invention therefore also relates to a device to carry out the method according to the invention characterized by an assembly comprising a series of measuring gauges with a dimension relevant for the determination of the preferred value, the value of which in said series of measuring gauges is varying iπ*the order of the perceptive precision and said values being randomly distributed across the preferred value with sufficient width to compensate for the variability per patient; indicator means provided with a nummerical display system coupled to a microprocessor-controlled system for the composition of the series of random ' parameter values; and means for the operation of the indicator means. The perceptive -precision is dependent on the nature of the parameter to be measured; in case of, for example, the determination of the occlusion to construct a dental prosthesis, the perceptive precision is in the order of 0,5 mm; however if the manufacture of orthopaedic foot-wear is concerned then the perceptive precision for the relevant parameter, for example the vertical height of the heel, will be more in the order of 0,5 cm. The invention will now be elucidated with reference to the accompanying drawing - ϋ E which shows an example of the embodiment of a device to be used for determining the PVDO in connection with the manufacture of a dental prosthesis. In the drawing fig. l in perspective view shows a device the assembly of which comprising gaπges, indicator means and operating means being combined to an s apparative unit, and fig. 2 the flow sheet belonging to the device according to fig. 1. In fiq. 1, the device is shown at 1, the indicator means of which is housed in the cabinet 2 At the upper side of the cabinet 2 recessesarε provided in an amount equal to the amount of measuring gauges removably held in saidrecesses i-e. gauges 3. These gauges may be manufactured out of any material which is not detrimental to -the patient's- health and which furthermore communicate dimensional stability to the ga.-uges. Their crosssectional form is rec-tanguiar _ the width of which is the measure determining the vertical occlusion. Based on their width they are suitably assemblied in groups corresponding to width dimensions of about 0,5-9,5 mm, about 10-19,5 mm and about 20-24,5 mm, always varying with the same increment of about 0,5 mm. The number of gauges is thereby chosen so that, taking into account the variation occurring in practice regarding the PVDO value, there always is sufficient distribution across the PVDO-values possible as well as that " a sufficient number of .observations may be carried out so that by statistically anylising the measuring results the PVDO can be determined. The above-mentioned amount of 49 gauges, varying in their width dimension between 0,5 mm and 25 mm is a useful number for this purpose. At 4 a display is shown on which the gauge to be chosen and the PVDO which is finally determined, is nummerically shown; 5 shows the press switch to start the microprocessor; 6 represents the press switch "too high" and 7 the press switch "too low". Not shown is the switch for the device to be switched on or off. For the determination of the PVDO with the device according to -the invention the dental surgeon or dental assistant needs to construct the assembly of lower and upper baseplates for the patient to be examined, each of these baseplates being provided wi h a platform at the front and being so constructed that after placing the baseplates into the patient's mouth the platforms contact each other when the patient brings them into occlusion. Moreover both platforms are so constructed that when the patient brings them into occlusion he considers the position of his lower jaw relative to his skull to be "too low". After placing the upper and lower baseplates in the patient's mouth the diagnostician start the microprocessor by pressing the press swith 5. On the display 4 the chosen gauge is nummerically shown. The diagnostician selects the gauge of the chosen size and places it between the upper and lower platforms of the baseplates with its width dimension in vertical direction. The patient bites on the gauge and decides whether the position αf his jaw relative to his skull is experienced to be "too low" or "too high". The diagnostician then enters the answer into the device by pressing either the swith 6 ("too high") or the switch 7 ("too low"). If the patient is unable to decide he is invited to guess and the answer is also entered into the device via switchβ or 7. The num erical indication of the gauge on the display 4 is replaced " by another one by the microprocessor and the diagnostician repeates the procedure. This, process continues until the -microprocessor shows on the display that a sufficient number of observations have been taken whereafter the microprocessor will show on the display the width dimension of the ga ge which the patient during testing has not consistently considered as "too low" or "too high". This dimension corresponds to the PVDO and appears on the display with the decimal point flashing. If the diagnostician wishes to know the range of tolerance of the so indicated PVDO, this information is available on the display by pressing either of the switches 6 or 7. Fig. 2 shows a flow sheet of the device according to fig. 1. It will be clear for that matter that the apparatus described above and shown in the accompanying drawing can be modified without departing from the scope of the present invention. Moreover both the method and the device according to the invention may be used for every psychophys cal measurement for the manufacture of prosthesises or for diagnostic purposes; for example: by substituting ienses of increasing strength, for the gauges the device is made suitable for ophtalmic " examination. Also the invention is suitable to be used in the field of audiology or rehabilitation medicine. O ?I

Claims: CLAIMS .1. Method for the construction of a human prosthesis to be used for partially or totally removing a physical disfunction through determination of the preferred value of a parameter serving the patient's optimum comfort being characteristic for the removal of the dysfunction by drawing a judgment from the patient regarding the parameter characterizing values, which valuesin a number sufficient .for statistical anylysis, are presented to him as a series of increments randomly varying -with aϊout the perceptive precision, whereafter the preferred value, is calculated and the prosthesis is constructed using the calculated preferred value, characterized in that the composition of the series of randomly varying values for the calculation of the preferred value is completely microprocessor- controlled and is chosen from a series-of values spanning across the preferred value; the values relevant for the calculation of the preferred value are administrated and said preferred value is calculated. 2. Device, suitable for application in the method according to claim 1, characterized by an assembly comprising a series of measuring gauges with a dimension relevant for the determination of the preferred value, the value of which in said series of measuring gauges is varying in the order of the perceptive precision and said values being randomly distributed across the preferred value with sufficient width to compensate for the variability per patient; indicator means provided with a nummerical display system coupled to a microprocessor-controlled s stem for the composition of the series of random parameter values; and means for the operation of the indicator means. 3. Device according to claim . 2 characterized in that the measuring gauges and the indicator means are combined to an apparative unit. OMP

Inventors: VAN WILLIGEN JAN DOUWE, VAN WILLIGEN, JAN, DOUWE
Applicants: UNIV GRONINGEN, RIJKSUNIVERSITEIT TE GRONINGEN
Application year: 1983
Main classification: A61C19
IPC codes: A61B3, A61C13, A61C19, A61F2