DE19614670A1 - Simulator for thermal and mechanical loadings on teeth - Google Patents

Abstract

A simulator which can imitate the true intraoral situation in respect to the thermal and mechanical loading on teeth and jaws consists of a test chamber (9) within which holders (7,11) can hold teeth or samples of dental materials (8). Air pressure can be applied to the upper sample to move it in relation to the lower one. The angle of the lower sample can be altered. The sample chamber can be heated or cooled by water fed in (9a) or let out (9b) at temperatures between 5 and 55 deg C. Forces and temperatures equivalent to those in the natural mouth can thus be applied to the teeth or samples to mimic chewing and the movement of the teeth against each other. This can be used to test materials, e.g. dental fillings, or dental techniques.

Description

Different methods are used to try to influence natural mouth situations Simulate dental materials and restorations. Ivo Krejci et al (Switzerland Monthly Bulletin Zahnmed. Vol. 100 8/1990 pages 953 to 960) and Ralp DeLong / William Douglas (IEEE Transactions on Biomedical Engineering Vol 38. No. 4 April 1991 Pages 339 to 345) similar machines have been described.

It is important the natural conditions of the oral situation, such. B. one larger section of a dental arch, the relationship of the teeth to each other, the natural Mobility of the teeth and the movement of the teeth to each other in the simulation with to involve. In addition, the device and various options for variation the process approximates the simulation to natural conditions will. Extreme conditions also allow the time to be shortened Simulation duration compared to the real load time. The machine is suitable for this Predictions about the behavior of different materials and constructions compared to To allow wearing time in the mouth.

The individual parameters and the approaches used are those in the patent described below.

2.1. force

Criteria: amount, duration, type of load freely adjustable, load speed.
To represent a chewing movement, a defined force is applied by an attached force unit (here pneumatic cylinder ( 1 ) standing vertically, possible: electrical, hydraulic, etc.). The control of this force is ensured in this case via a pressure valve. The force is limited depending on the type of pneumatic cylinder, but can be freely adjusted (here: variable in the range from 0 to 200 N). With the help of a pneumatic valve, the speed at which the test stamp hits the test specimen can also be set. A suitable system ( 2 ) (e.g. mechanical (spring), pneumatic) can be used to quickly reset the cylinders. The duration of the exposure and the frequency of the exposure per unit of time can be variably set by means of an appropriate control.

2.2. Slip way

Criteria: free inclination, simulation of a horizontal force component, abrasion, free amount of force and free amount of displacement, cusp-fossa relationship.
The sliding process is made possible by the flexible mounting of the lower sample holder ( 11 ). This is done in a special case by sliding storage on an inclined plane with a sliding or ball bearing system ( 12 ) (here 30 degrees), but can also be done via corresponding other systems such. B. rubber bearings and different angles. If the samples fixed in the upper ( 7 ) and lower sample holder ( 11 ) are offset from one another by a certain amount, the impact of the two samples on one another creates a horizontally acting force component. The result of this is that the lower sample holder ( 11 ) is laterally deflected via the ball bearing system on the inclined plane. This simulates a lateral sliding movement of the teeth in relation to one another, as occurs when grinding and grinding the food. This deflection is limited by a side-mounted system ( 12 a) (e.g. spring) and its amount and force can be freely adjusted. Monitoring of the deflection path is ensured by dial indicators (e.g. mechanical, electrical).

2.3. Sample chamber and medium

Criteria: saliva, temperature change load.
The sample chambers ( 9 ), like all liquid lines, are designed to be transparent in order to permit visual monitoring of the flow medium (other materials are possible). The liquid (e.g. distilled water, NaCl solution, artificial saliva) flows into the sample chamber through a hole ( 9 a) at the top. The chamber is emptied via a corresponding hole at the lower end of the sample chamber ( 9 b). An overflow ( 9 c) is introduced at a defined distance above the inflow hole, which prevents the chambers from being filled too strongly or from overflowing. In this way, the maximum rise height of the medium in the sample chamber can be defined (here about 3 cm). All connections of the media system are guaranteed by quick connections, so that the system can be completely disassembled or the test specimens can be replaced. The connections can also be made using rigid connections (e.g. screws, weld seam).

The system is filled by at least two pumps. These pumps can be switched on and off, but can also be operated continuously. The special circuit (here pneumatic) fills the sample chamber ( 9 ) via a pump system with a variably adjustable delivery rate within a freely selectable time, whereby the fill level (rise height) is also freely selectable. The flow (inflow and outflow open at the same time, test medium circulates evenly through the sample chambers) can be set variably in time. This means that the duration of the flushing process but also the amount of the flushing medium can be controlled. The discharge time can also be freely set. The emptying of the sample chambers can e.g. B. by pumping or simply by the action of gravity. The outflow of the system can also be precisely adapted to the system via fine valves. The different temperature-controlled medium is returned to the corresponding temperature baths via an appropriately designed system of lines and valves. The liquid temperature can be set freely depending on the cooling or heating units used and the corresponding media (here in the range between approx. 5 ° C and 55 ° C). This guarantees the possibility of simulating extreme temperature changes in the mouth (comparative coffee, ice cream). An expansion to other temperatures is conceivable and easily possible.

The system sample holder ( 7 , 11 ) sample chamber ( 9 ) has a modular structure. The lower sample holder ( 11 ) and the sample chamber ( 9 ) are sealed by punctures and rubber rings ( 16 ). With this system, the lower sample holder can be separated from the sample chamber by simply squeezing it out and replaced with a sample holder of a different size. As a result, various sample holders can be installed in the chewing simulator quickly and without effort. Additional sealing of the medium to the environment is not necessary.

The housing of the entire device is of different heights due to its variable design Samples adaptable (variation of the height through holes in (4)).

2.4. Sample holder and counter tooth

Criteria: Multifunctional, for different numbers and sizes of samples and teeth (also samples of corresponding national and international standards e.g. DIN, ISO), different counter teeth and stamps, natural. Teeth, various materials of the opposite teeth, various shapes of the opposite teeth and stamp.
The sample holders ( 7 , 11 ) are designed in such a way that several teeth can be held on both the upper and the lower sample holder. Depending on the requirements, geometrically defined stamps (including artificial teeth) made of different materials (steel, Teflon, etc.), a natural antagonist or a section of a complete row of teeth can be used as a "counter tooth" [possibility of holding different test specimens as well as more complex ones Dental constructions (e.g. inlays, crowns, bridges, prostheses for dynamic material testing) - Possibility of inserting extracted natural teeth as pillars and / or antagonists at any point on the dental arch test specimen, which can then be further examined according to the relevant national or international test regulations will]. The test specimens can be installed and loaded in both the lower and the upper part of the system.

All sample holders ( 7 , 11 ) are equipped with a system (2 grooves in 2 pins ( 6 )) which ensures that the sample holders are placed precisely and reproducibly both in the articulator and in the simulation device. The connection of the sample holder to the two devices is flexible and was created in a special case by screw connections, but can also be guaranteed by other systems (quick connections, clips, etc.).

The arrangement of the sample holder / sample chamber system can be in both the upper and also rotated at different angles (here 45 ° steps) for the lower sample chamber will. This allows the direction of the shear forces to be varied in this area, Teeth can optionally z. B. in exactly the vestibular, oral or buccal direction or defined angles.

All sample holders are made with an incline to completely empty the sample holder Secure the sample chamber in the normal state of the device.

2.5. Articulator and periodontal mobility

Criteria: transfer of the oral situation, reproducibility of the relation of the stamp / test specimen to each other, paradontal mobility of the test specimen / stamp.
All of the teeth used can be inserted into the sample holder in the dental articulator, specifying the exact tooth and mouth situation. The tooth / counter tooth distance can be freely adjusted using a suitable height-adjustable table. The relation of the samples to each other is fixed by an integrated anti-twist protection ( 17 ). As mentioned under 4., the sample holder can be converted into the chewing simulator, whereby the reproducibility and accuracy of the connection is guaranteed by the 2 pin 2 hole ( 6 ) system. The teeth, but also samples, artificial teeth, etc. are fixed in the sample holder using bonding materials (e.g. plastic, plaster). The tooth mobility of the natural mouth situation can be simulated using a special embedding process. Using a dip wax process, a defined, but variable in size layer of elastic material (e.g. polyether rubber, silicone) can be introduced to simulate a physiological paradontal mobility between the specimen or tooth and specimen holder. This rubber layer allows a variable deflection in clinically relevant areas of approx. 1/10 mm axially and radially with appropriate chewing forces. (Dr. Scharnagl's work)

2.6. Distance of samples

Criteria: variable interocclusal distance, various forms of contact between sample and stamp.
The described, flexible height adjustment of the sample holder in the articulator is compensated accordingly by the different extension of the pneumatic cylinder in the chewing device. A system mounted on the top of the device (here spring or compressed air) ensures that the upper sample holder is lifted off (= mouth opening). In this way, a lifting of the stamp from the specimen can be defined, but also a simulation can be carried out without the specimen stamp lifting off the test object or a defined lifting movement being set. In addition, the impact force or the closing speed of the upper sample holder on the lower one can be freely adjusted.

2.7. Monitoring, number of samples

Criteria: recording, control and regulation, number of samples.
The complete system consists of at least one simulation unit (0), but it makes sense to have a number of simulation units between 6 and 10. All functions (masticatory force / temperature) in the test chambers can be recorded and monitored by PC control. For this purpose, thermometers and force transducers must be connected to each test chamber, which record the values in the corresponding areas. A feedback of the values to the temperature control units as well as the power unit can e.g. B. can be achieved via PC control.

The technical drawings of the prototype system with the corresponding follow Pneumatic circuit diagrams.

Claims (1)

1. Device and method for simulating the intraoral situation in relation to thermal and / or mechanical stress on teeth, restorations or corresponding test specimens in the field of dentistry / dental technology. The device is characterized in that a mouth-like force and temperature load of several natural and / or dental models and materials can be carried out taking into account the tooth mobility, the adjustable jaw and tooth relationships in the dental articulator and a sliding movement of the teeth to each other.