WO1998001736A1

WO1998001736A1 - Method and device for measuring resilience

Info

Publication number: WO1998001736A1
Application number: PCT/SE1997/001213
Authority: WO
Inventors: Lars G. Petersson; Margien Luinge; Peter Borsboom
Original assignee: P.B. Sensortechnology & Consultancy
Priority date: 1996-07-04
Filing date: 1997-07-04
Publication date: 1998-01-15
Also published as: SE508338C2; SE9602642L; AU3638197A; SE9602642D0

Abstract

The invention concerns a device and a method for measuring the resilience in an area (16) of an object (30). The device comprises an oscillation source, a first transmission means (14) for transmission of an oscillation movement from the source of oscillation to the area (16), and a measuring means for measuring the oscillation movement damping caused by said area (16). The method comprises the steps of providing an oscillation movement of the area (16) and by measuring the oscillation movement damping caused by said area (16).

Description

METHOD AND DEVICE FOR MEASURING RESILIENCE

The subject invention concerns a device and a method for measuring resilience in an area of an object.

Within e.g. dental technology, diagnostic scanning of root caries is carried out according to prior-art technology with the aid of a sharp, narrow probe that the dentist manually presses against the area of the tooth suspected to be affected by root caries. Affected areas in teeth are demmeralized and consequently more porous and yielding than non-affected areas. At the instance of diagnosis the dentist subjectively assesses whether the tested area is soft, leathery or hard. An inherent disadvantage of this diagnosis method is that it is destructive, since it leaves the tooth permanently damaged by the probe tip, and that it is non-objective . In accordance with another prior-art diagnosis method for detecting root caries the tooth is subjected to an X-ray examination. However, the X-ray picture of the tooth has poor resolution and contrast and the method is limited to proximal tooth surfaces, i.e. contacting surfaces.

Recently, measurement of tooth conductivity has been used to diagnose root caries. However, this method suffers from several drawbacks, which are connected with desiccation of the surface to be checked. Hardness measurement has been suggested as one diagnosis method but is unsuitable for in vivo testing, since a root affected by caries is not flat and because the area of the root affected by caries yields under pressure, i.e. is resilient. In addition, also this diagnosis method is one that has a destructive effect on the checked area of the tooth.

Thus, it is easily understood that it is difficult, almost impossible, to make correct and objective assess- ments for root caries detecting purposes by means of prior-art technology.

Root caries may be "repaired" by means of so called remmeralization of the affected area, involving redeposition in and on the tissue of mineral which has been removed from the affected area by the caries process. Repaired root caries areas essentially resume the same mechanical-elastic properties as sound root dentm. It is a problem that prior-art technology does not provide a satisfactory objective method of evaluating the effects in course of time of root caries treatments, that is to say whether or not successful remmeralization of a tooth area affected by root caries has been achieved . It is particularly with the view to solve these problems within the field of oral diagnosis technology that the invention defined the appended claims has been conceived. However, it has been found that the invention could also be used for resilience measurement other applications than to measure root caries.

A primary object of the subject invention thus is to provide a device and a method for measuring the resilience in an area of an object, by means of which an objective measurement result may be obtained. Another purpose of the subject invention is to provide a device and a method for measuring the resilience in an area of an object, by means of which an objective measurement result may be obtained, also from several measurements that are carried out on different occasions.

The third purpose of the subject invention is to provide a device and a method of measuring the resilience in an area of an object that are essentially nondestructive to the area concerned. A fourth purpose of the subject invention is to provide a device and a method for measuring the resilience in an area of an object that are simple to use and could also be used for measurement in comparatively small and narrow spaces.

These and other purposes are achieved in accordance with the invention by means of a device and a method for measuring the resilience in an area of an object having the characteristics defined in the appended claims.

Various embodiments of the invention that are preferred at the moment will be described in detail in the following with reference to the accompanying drawings.

Essentially equivalent detail components shown the various drawing figures are identified by corresponding numeral references.

Fig. 1 illustrates in a schematic, partly cut perspective view, a first embodiment of a device in accordance with the invention.

Fig. 2 illustrates an area of Fig. 1 on an enlarged scale .

Fig. 3 illustrates in a partly broken, schematical sectional view seen from the side, a detail incorporated in the device in accordance with Fig. 1, on an enlarged scale .

Fig. 4 illustrates in a schematical, partly cut view, a second embodiment of a device in accordance with the invention.

Fig. 5 illustrates in a schematical exploded view components incorporated in the device in accordance w th Fig. 4.

Fig. 6 is a schematical block diagram of one embodi- ment of a driver and measuring device accordance with the invention.

Fig. 7 is a schematic view of a tooth used for in vitro measurements in accordance with the invention.

The device illustrated in Fig. 1 has a body, ldenti- fied generally by numeral reference 1 and fitted with a handle 2. The body 1 and the handle 2 preferably are manufactured from a non-conductive material, such as plastics. The device is equipped with an oscillation- generating source, comprising an oscillation-generacing element generally identified by numeral reference 3, and a driver means, generally identified by numeral reference 12 (see Fig. 6) .

The oscillation-generating element 3 illustrated Fig. 1 is mounted in a recess in the front part of the body 1. The oscillation-generating element 3 is also illustrated on an enlarged scale in Fig. 3 and in accordance with the embodiment shown it comprises a diaphragm component 4, e.g. in the form of an essentially circular metal plate.

The diaphragm component 4 supports on its inner side facing the body 1 a piezoelectric element, generally identified by reference 5. The piezoelectric element 5 comprises a piezoelectric plate 6 having one electrode 7 on the side turned towards the diaphragm component 4 and one electrode 8 on the side turned towards the interior of the body 1. In accordance w th the embodiment illustrated the diaphragm component 4 is attached, in the area of its peripheral border, to the recess formed the front part of the body 1, for instance by means of glueing. By means of wires 9 and 10, respectively, which in accordance with the embodiment shown extend through a channel formed the body interior, the electrodes 7 and 8 are connected to the driver means 12 (see Fig. 6) forming part of a driver and measuring device, generally identified by numeral reference 11 (see Fig. 1) . In accordance with the example shown the driver means 12 is an AC-source, which when m operation, produces oscillation of the piezoelectric element 5, said oscillation being directed laterally relatively to the diaphragm component 4 as indicated by arrow 13. In accordance with a preferred embodiment the amplitude and/or voltage frequence of the AC-source is variable. On the side of the diaphragm component 4 facing away from the body 1 a first transmission means 14 is attached in accordance with the embodiment illustrated, e.g. by means of glue, to a component such as a non-conductive plastic component 15 which in turn is attached to the diaphragm component 4. The first transmission means 14 is manufactured from e.g. stainless steel and the area of its end facing away from the body 1 the end portion is bent to an angle of 90° accordance with this embodiment.

The device also includes a measuring means comprising a vibration-detecting means, a second transmission means 17 and a display unit, generally referred to by reference 20. In accordance with a preferred embodiment the second transmission means 17 is manufactured from stainless steel. In accordance witn the embodiment illustrated said means makes contact with and preferably is securely attached to the first transmission means 14, e.g. through welding, in the area of the end facing away from the body 1. In accordance with the embodiment shown the second transmission means 17 is attached, in the area of its end turned towards the body 1 to a component 18, e.g. by means of glue, such as a non-conductive plastic component. In turn, component 18 is attached to a vibration-detecting means. The vibration-detecting means is arranged a recess formed in the same end of the body 1 as the above-mentioned piezoelectric element. In accordance with the embodiment illustrated it comprises a diaphragm component which is connected to a second piezo- electric element, generally identified by reference numeral 19 and preferably being of the same type as the above-mentioned piezoelectπcal element. By means of wires, which in accordance with the embodiment illustrated extend through a channel formed in the body interior, the electrodes of the second piezoelectrical element 19 are connected to the display unit 20 (see Fig. 6} . The display unit 20 is incorporated in the driver and measuring device 11 (see Fig. 1) and in accordance with the embodiment illustrated it comprises an amplifier 21, a rectifier 22 and a phase-shift detecting unit 23.

Fig. 1 schematically illustrates an object 30, in this case a tooth, the g giva of which is retracted in one area causing root carious lesion in an area 16. The device in accordance with the invention is inserted in the mouth of the patient in a manner allowing the firs_t transmission means 14 to make contact with an area to be diagnosed, such as the surface area 16. When the device is operative the oscillation movement of the piezo- electπcal element 5 is transmitted to the first transmission means 14 and to the area 16, the first transmission means 14 being manipulated to ensure that the oscillation movement thereof is directed essentially in parallel with the surface of area 16, i.e. in the direction of arrow 13' (see Figs. 1 and 2, arrows 13 and 13' being essentially parallel) . Since the volume (and depth) of the carious lesion of the root is comparatively small compared to the thickness of the root, the force affecting the measurement area of the tooth and directed essentially in parallel with the measurement area should be comparatively small, a condition which it is easy to achieve for instance by limiting the amplitude of the oscillations of the piezoelectrical element 5, thus limiting the oscillations in the tested measurement area.

In case the area 16 is affected by caries its resilience differs from that of the non-affected area of the tooth on account of demmeralization . In particularly, the resilience of an area 16 which is affected by caries is larger than that of the non- affected area of the tooth on account of demmeralization and consequently the area 16 produces less damping of the oscillation movement of the first transmission means 14 than is the case in a non-affected area of the tooth. The second transmission means 17 transmits the damped oscillation movement from the first transmission means 14 to the vibration-detecting means and in accordance with the embodiment shown the signal emitted from this means is amplified by the amplifier 21 and the signal is rectified by rectifier 22 which means the amplitude of the damped rectified signal may be read in a suitable manner.

The amplitude is smaller in the case of non-caries areas than caries-a fected areas since the oscillation movement of the first transmission means 14, as mentioned previously, is damped to a higher degree upon contact with a non-caries area than in the case of a caries- affected area. The damping of a caries-affected area also results in a phase-shift between an input-signal, such as an alternating-current, from the driver means 12 to the oscillation-generating element 3, and an output-signal, such as an alternating-current, from the vibration- detecting means. The difference in amplitudes and/or phase is sufficiently large to allow t to be read in a simple manner from the display unit 20. Consequently, an objective result of the diagnosis with respect to the tested area is obtained.

Fig. 4 illustrates a second embodiment of the invention. This embodiment utilizes only one piezoelectrical element designated generally by numeral reference 24. A first transmission means 14' is, in a manner similar to that described above in connection with the previous embodiment, attached e.g. by means of glue to a component such as a non-conductive plastic component 15' which in turn is attached to a diaphragm component connected to the piezoelectrical element 24. In accordance with this embodiment the first transmission means 14' serves also as the second transmission means 17', with the result that this means transmits also the damped signal from the tested measurement area. This is achieved owing to the configuration, known per se, of the piezoelectrical element, which is schematically illustrated in Fig. 5. At one side thereof, accordance with the embodiment shown the side turned towards the body 1', an electrode means is provided, designated generally by numeral reference 25 and comprising a electrode 26 which together with electrode 7' is connected to the driver part of the driver and measuring device 11', said driver part essentially having a function identical to that m accordance with the embodiment of Fig. 6. The second electrode 27 of electrode means 25, which electrode is insulated from electrode 26, is connected to a first pole of the display unit of the driver and measuring device

11' . At a second pole, the display unit is connected to a pole of the driver means, for instance by being connected to electrode 7' or electrode 26. Thus, a detection signal is supplied to the display unit with the aid of only one single piezoelectrical element. Otherwise, the display unit has essentially the same function as that illustrated in Fig. 6.

In accordance with one preferred embodiment the oscillation frequency of the oscillation-generating source is chosen, alternativly is adjustable to ensure generation of resonance frequency of tne oscillation movement of the first transmission means 14, 14'. Upon attainment of the resonance frequency, the measured amplitude increases considerably and the phase changes, which among other things may be read in any suitable manner n the phase-shift detecting unit 23. Depending on the configuration and design of the device, and above all in order to achieve good measurement results in the case of resonance frequency of the first transmission means 14, 14', it is advantageous to use oscillation frequencies ranging from 1 Hz till 100 kHz, and in particularly within the range from 1 kHz till 20 kHz.

The invention has been tested experimentally by measuring root caries in vitro as well as in vivo. The results of these measurements are outlined below. Any suitable unit of measurement showing the damping may be used for the measurements. For instance, the amplitude may be measured and be indicated in V or A. Test 1: In vitro In the in vitro tests the device in accordance with the embodiment of Figs. 1-3 and 6 was used. The transmission means 14 was made from stainless steel, had a diameter of 1.2 mm and its outer tip was bent at an angle of 90°. By means of a cyanoacrylate adhesive the transmission element was glued to a circular metallic diapnrag component 4 via a non-conductive plastics member 15. The peripheral edge of the diaphragm component 4 was secured to the front end of the body 1 by means of a cyanoacrylate glue. A piezoelectric element 5 was attached to the side of the diaphragm component 4 turned towards the interior of the body 1.

The second transmission element 17, of stainless steel, had a diameter of 0.6 mm and one of its ends welded to the transmission element 14. The opposite end of the second transmission element 17 was secured to a circular metallic diaphragm component by means of a cyanoacrylate glue via a non-conductive plastic element 18. The peripheral edge of the diaphragm component was attached to the front end of the body 1 by means of a cyanoacrylate glue. A second piezoelectric element 19 was attached to the side of this diaphram component turned towards the interior of the body 1.

The diaphragm components and the piezoelectric elements, 5 and 19 respectively, are commercially available as so called "piezoelectric sound components". In tne tests, two components of this kind, available from Hoechst CeramTec AG Lauf, Germany, of type "Sonox P51 35424", having a diameter of 12.5 mm, were used.

The hollow body 1 was manufactured from a non- conductive plastics material. The piezoelectric elements, 5 and 19 respectively, were connected to a driver and measuring device 11 in accordance with Fig. 6. The in vitro studies were performed on extracted human pre olars, removed for orthodontic reasons. The A.C. voltage supplied to the piezoelectric elements, 5 and 19 respectively, amounted to 9 V. By storing the test teeth in a 6% carboxymethyl cellulose gel mixed with 0.1 moles per litre of phosphoric acid, giving a final pH-value of 5.0, it is possible to induce artificial caries formation on various tooth faces through continuous demmeralization. As a reference, round zones were created on the teeth by application thereon of protective, glued-on circular bio- discs (having a diameter of 3 mm) which were covered by nail varnish to withstand the effects of the acid-gel treatment. When the bio-discs are removed they expose tooth surfaces in the form of circular fenestrations . This is illustrated in Fig. 7 wherein an acid-treated tooth is shown schematically. The tooth has an acid- treated root surface 50 and an acid-treated enamel surface 51. The bio-discs on the associated surfaces are designated by 52 and 53, respectively.

The results of the measurements appear from Table 1.

Table 1. Amplitude measurements in accordance with the invention on extracted teeth having been submitted to continuous demineralization by storage for 3 weeks in a 6% CMC gel having a pH-value of 5.0.

[Amplitude in suitable measurement unit]

Tooth No. Sound dentin "Carious " dentin

B P B P

1 163 166 188 215

2 152 140 500 200

3 170 165 400 120

4 225 175 520 600

5 150 74 400 300

6 168 200 650 640

7 80 200 200 170

8 140 220 300 230

9 220 113 450 520

10 165 220 680 720

11 143 170 700 550

12 145 168 600 520

13 170 150 500 500

14 188 182 490 534

15 128 134 510 420

Amplitude

Mean Value + 160+35 165±39 473+157 416±193

Standard

Deviation

B: Buccal P: Proximal

Conclusion

The mean amplitude measured in accordance with the invention amounted to 160+35 units of measurement on buccal faces of sound dentin and to 165+39 units for proximal faces in the example referred to. In the case of artificially induced carious dentin considerably higher amplitudes were found when measuring in accordance with the invention. On buccal faces, 473+157 units of measurement were found and on proximal faces 416+193, in accord- ance with this example.

Test 2: In vivo

In the in vivo tests the device in accordanace with the embodiment of Figs. 4-6 was used. The transmission means 14' was made from stainless steel, had a diameter of 1 mm, and it was bent to a radius of 10 mm. By means of a cyanoacrylate adhesive the transmission element 14' was glued to a circular metallic diaphragm component 4' via a non-conductive plastics member 15' . A piezoelectric element 24 was attached to the side of the diphragm component 4' turned towards the interior of the body 1'. The diaphragm component 4' and the piezoelectric element 24 are commercially available as so called "piezoelectric sound components". In the tests, a component of this kind, available from Hoechst CeramTec AG Lauf, Germany, of type "Sonox P51 35424 /selfdrive", having a diameter of 12.5 mm was used. The peripheral edge of the diaphragm component 4' was glued to the front end of the body 1' by means of a cyanoacrylate adhesive. The front end of the hollow body 1' having an inner diameter of 11.5 mm, and its handle part 2' were both made from a non-conductive plastics material. The piezoelectric element 24 was connected to a driver and measuring device 11' having the same function as that illustrated in Fig. 6. The inventive method has been tested on patients having clinically diagnosed root caries.

For instance, reproducibility measurements were carried out on a 25 year old patient exhibiting the following dental status. Teeth 24 and 13: Root caries having a "leathery" surface structure. As a reference, also the sound enamel on the same teeth was measured. The results appear from Table 2. Table 2. [Amplitude in suitable units of measurement]

Tooth 24 Tooth 24 Tooth 13 Tooth 13

Carious Sound Carious Sound root enamel root enamel surface surface

180 150 180 100

180 120 190 100

180 120 170 100

170 120 180 120

190 100 200 150

180 120 200 120

190 120 190 100

170 120

190 120

Amplitud

Mean Value

Standard 183+8 121±11 188+10 110+17

Deviation

An amplitude study was also carried out on four more patients, including 20 teeth exhibiting carious root surfaces, sound enamel on each individual tooth being used as a positive reference structure. The results of the measurements appear from Table 3. Table 3. [Amplitude in suitable units of measurement, N=number of teeth]

Carious Sound Sound

Root Surface Root Surface Enamel N=7 N=13 Surface

N^*=20

Amplitud Mean Value 146+6 105+8 115±10 Standard Deviation

Conclusion

From the in vivo study may be concluded that carious root surfaces have an approxia tely 40% higher average amplitude level and that the amplitude levels of sound root dentin and of fresh enamel do not differ significantly. In other words, both sound enamel and sound dentin may be used as references in measuring root surfaces having clinically defined caries. The ratio of carious root to enamel is about 1.4.

Other embodiments of the invention

In accordance with one embodiment of the invention the second transmission means 17 does not make contact with the first transmission means 14 but instead with the measurement area adjacent the contact area of the first transmission means 14 with the object to be measured. In accordance with this embodiment the oscillation movement is transmitted from the first transmission means to the second transmission means via the measurement area of the object .

The design and construction of the display unit may be varied within wide limits. For instance, it may not have a rectified voltage amplitude but could display any signal that gives an indication of the size of the damping.

The vibration-detecting means need not comprise a piezoelectric element in order to provide a signal corresponding to the damping. Instead, other kinds of vibration-sensitive detectors, such as capacitive, magnetic, electro-magnetic or acoustic detectors may be used.

For instance, the oscillation movement could also oe produced by means of a magnet-operated or electro- magnetically operated element. Likewise, it is possible to produce an oscillation movement the form of "shock- waves" in contrast to the example described above, according to which the sinus-configuration of the alter- nating current source results in continuous oscillation movements of the first transmission means 14, 14'.

Enamel caries sometimes lead to caries in the crown dentin mteriourly of the enamel. It is easily understood that the invention is equally applicable for measurement of this type of dentin caries. This type of tooth damage may be treated for instance by removing the damaged areas of the enamel and of the dentin and subsequently temporarily fill the hole in the enamel and the dentin. As the pulp is healing, it will retract from the damaged area and dentin will hopefully form up to the afflicted area. After some time, tne filling may be removed for examination of the effects of the treatment. For this purpose, the invention may be used to measure the resilience of the affected crown dentin before and after the treatment in order to achieve an objective measure of the effects of the treatment.

One has also found that the invention could advantageously be used for measurement of the resilience of objects in other fields of application than for measure- ment of root and dentin caries in teeth in the mouth of human beings or animals or on an extracted tooth. For instance, the invention is applicable primarily within the area of general medicine in order to measure tne softening of dentin, skeleton and nails, order to measure wound-healing processes wherein the healing process causes an increase or change of the elasticity of the wound area, or to measure horny sk n formations.

For instance, the invention may be used to measure the resilience of capsules of such materials as cellulose and the like, which capsules may be used e.g. to enclose pharmacological products and medicine. The invention may likewise be used to measure the resilience of other types of products of paper and cellulose.

Another field of application of the invention is to measure the progress of drying processes, for instance the drying progress of paint the resilience of which lessens m the course of the drying process.

Other examples of applications of the invention are for measurement of the coagulation of for instance blood and in connection with the production of gels within e.g. the food industry. It is also easily understood that the method and the device in accordance with the invention could be used to measure resilience within several other fields of application, such as for instance measurement carried out with respect to wooden materials, for instance for the purpose of checking rot, to rubber, for instance to measure the resilience of rubber gaskets the resilience of which decreases with age, and to resins, plastics, hide/leather within the processing industry and so on. In most of these applications it is preferable that measurement of the resilience is carried out in the surface area of the object but it goes without saying that it is quite possible, for instance m the case of coagulation and gel-formation applications, to measure for resilience also for instance in the middle of the object to be measured (e.g. in the centre of e.g. the gel) by introducing at least a first transmission means inside the object to be measured. The invention likewise concerns a method of measuring the resiliency in an area of an object, comprising the steps of generating an oscillation movement of the area and by measuring the damping of the oscillation movement caused by that area.

The invention provides a device and a method of measuring the resilience in an area of an object, resulting in objective measurement results, for instance in the form of a rectified amplitude of the damped oscillating movement. Owing to the invention, it thus becomes possible to obtain objective measurement results also when several measurements are carried out on different occasions, for instance to measure the progress of a remmeralization process in a caries-affected area in a tooth. According to a preferred embodiment the oscillation movement m the tested area is essentially parallel with the surface of the tested area and a comparatively small-amplitude oscillation movement is used, with the result that measurement carried out by means of the device in accordance with the invention and by performing the method m accordance with the invention are essentially non-destructive to the area of measurement of the object. Owing to the configuration of the device the latter is simple to use and could advantageously be used also for measurements that need to be carried out m comparatively narrow spaces, for instance to diagnose and detect root caries in the oral cavity.

The mam applications for the invention are in dentistry, as in: • Monitoring on (active) root caries represented by a soft/leathery apperance (for general dental control) ;

• Monitoring on active de- and remmeralization of root caries (for toothpaste-producers etc and associated caries research) ;

• Monitoring chemical and/or laser based removal of caries dentine, alternative methods for mechanical drilling, or monitoring reconstruction systems (process-control) . An other important application area is skm-research or dermatology, where the invention can be used in: • Monitoring the appearance of normal to horny skin in a diagnostic system or the like;

• Monitoring typical medical therapy or treatments of the skin, including burned skin;

• Monitoring typical skin-behavior due to treatment with so called cosmetic creams and related gels including sun protective materials. Finaly the invention is also very useful in material science related applications, as in:

• Examining outer layer properties of relative soft materials, where the outer surface or top-layer changes due to external or internal influences, for instance effects like hardening or softening of the outer layer due to wheather, light, radiation and other degradation influences. • Process monitoring of relative soft materials like rubber and plastics, where the bulk and surface conditions can differ between batches.

• Wood examination, where the hardness between annual or growth rings can differ or differences in a specified type of wood occur.

• Resiliences behavior of miniature systems positioned on top of a (rigid) structure.

It is easily understood that it is quite possible to deviate somewhat from the described embodiments. All varities and modifications that are encompassed by the basic inventive idea should, however, fall within the scope of the appended claims.

Claims

1. A device for measuring the resilience m an area (16) of an object (30), c h a r a c t e r i s e d in that the device comprises a source of oscillation, a first transmission means (14; 14') for transmission of the oscillation movement from the source of oscillation to the area (16), and a measuring ears for measuring the oscillation movement damping caused by the area (16), whereby the oscillation movement of the first transmisson means (14, 14') is essentially parallel with the area (16) .

2. A device as claimed in claim 1, c h a r a c t e r i s e d in that the object (30) is an essentially rigid structure, such as a tooth, that the measurement area (16) consists of the surface area of the object (30), and in that the first transmisson means (14, 14') makes non-destructive contact with said surface area without penetrating it.

3. A device as claimed m any one of the preceding claims, c h a r a c t e r i s e d in that the measuring means comprises a vibration-detectirg means for detection of the oscillation movement damping caused Dy said area (16) .

4. A device as claimed in claim 3, c h a r a c t e r i s e d in that the measuring means comprises a second transmission means (17; 17') for transmission of the damped oscillation movement from the area and/or from the first transmission means (14; 14') to tne vibration- detecting means.

5. A device as claimed in any one of claims 3 - 4, c h a r a c t e r i s e d m that the measuring means comprises a display unit (20) which is connected to the vibration-detecting means and which display un t direct- ly, or after having been submitted to some treatment, such as amplification, rectifying and the like, displays a damping-mdicatmg signal emitted by the vibration- detecting means, for instance in the form of the amplitude of a rectified alternating voltage from the vibration-detecting means, or in the form of the phase- shift between an input-signal to the source of oscillation and an output-signal from the vibration- detecting means, such signals for example being alternating-currents.

6. A device as claimed in any one of claims 3 - 5, c h a r a c t e r i s e d in that the vibration-detecting means comprises a piezoelectric element (19; 24) for detection cf the oscillation movement damping caused by said area (16) .

7. A αevice as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the source of oscillation comprises an oscillation-generatmg element (3) with a piezoelectric element (5, 24) for the generation of said oscillation movement.

8. A device as claimed m claim 6, c h a r a c t e r i s e d in that the source of oscillation comprises an oscillation-generating element (3) with a piezoelectric element (24) for the generation of the oscillation movement, and in that said piezoelectric element (24) is used for the source of oscillation as well as for the vibration-detecting means.

9. A device as claimed any one of claims 1 - 6, c h a r a c t e r i s e d in that the source of oscillation has an oscillation-generatmg element with a magnetically operated element for generating the oscillation movement.

10. A device as claimed in any one of claims 7 - 9, c h a r a c t e r i s e d in that the source of oscillation comprises a driver means (12), preferably in the form of an alternating-current source, which is connected to the element (5, 24) generating the oscillation movement.

11. A device as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the oscillation frequency of the source of oscillation is adapted and/or in that the oscillation frequency of the source of oscillation is adjustable for the generation of resonance frequency of the oscillation movement of the first transmission means (14; 14').

12. A device as claimed in any one of the preceding claims, c h a r a c t e r i s e d m that the oscillation frequency ranges from 1 Hz to 100 kHz, and preferably is within the range of from 1 kHz to 20 kHz.

13. A device as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that it comprises a body (1) with a hand piece (2) thereon, m that an oscillation-generatmg element (3) is arranged on the body (1), in that the first transmission means (14; 14') is connected to the oscillation-generating element (3), in that a vibration-detecting means of the measuring means is arranged on the body (1), and in that a second transmission means (17; 17') for transmission of the damped oscillation movement from the first transmission means (14; 14') to the vibration-detecting means is connected to the first transmission means (14; 14') and the vibration detecting means.

14. A method of measuring the resilience in an area (16) of an object (30), c h a r a c t e r i s e d by the steps of producing an oscillation movement of the area (16) and by measuring the oscillation movement damped caused by said area (16), whereby the oscillation movement is essentially parallel with the area (16).

15. A method as claimed in claim 14, c h a r a c t e r i s e d by the steps of producing, by means of a source of oscillation, an oscillation movement of a first transmission means (14, 14'), by establishing nondestructive contact between the transmission means (14, 14') and the area (16), and by measuring the oscillation movement damping caused by said area (16) by means of a measuring means.

16. A method as claimed in claim 15, wherein the object (30) is an essentially rigid structure, c h a r a c t e r i s e d by the steps of carrying out the measurement m a surface area of the object (30) and by providing an oscillation movement of the first transmission means (14, 14') which in said surface area s essentially parallel with the surface area.

17. A method as claimed in any one of claims 15 -

16, c h a r a c t e r i s e d by measuring, by means of the measuring means, the damped oscillation movement in the area (16) and/or measuring the damped oscillation movement of said first transmission means (14, 14') directly or via a second transmission means (17).

18. A method as claimed in any one of claims 14 -

17, c h a r a c t e r i s e d by displaying, in a display unit (20) directly or after treatment, such as ampl fica- tion, rectifying and the like, the damped oscillation movement, for instance m the form of the amplitude of a rectified alternating current voltage from the measuring means, or m the form of the phase-shift between an input-signal to the source of oscillation and an output- signal from the vibration-detecting means, such signals for example being alternating-currents.

19. A method as claimed in any one of claims 15 -

18, c h a r a c t e r i s e d by adjusting the oscillation frequency of the oscillation movement and/or adjusting the oscillation frequency of the oscillation movement in such a way that resonance frequency is generated for oscillation movement of the first transmission means (14, 14').

20. A method as claimed in any one of claims 14 - 19, c h a r a c t e r i s e d by generating an oscillation frequency ranging from 1 Hz to 100 kHz, and preferably ranging from 1 kHz to 20 kHz.