Impression tray for fixed dental prosthesis

Abstract: An impression tray for fixed dental prosthesis, whose main feature is to have a first (5) and a second opposed recesses (8) to contain the material to be impressed, through which both the impressions of the upper and lower side of the dental arcade of a patient can be taken simultaneously.

Description: The present invention refers to an impression tray for fixed dental prosthesis. As known, when teeth need treatment for cosmetic or functional reasons, either through their capsulation or replacement of missing teeth, impressions of dental arcades are taken. Said impressions are obtained by means of impression trays having different configurations according to the kind of impression to be taken, i.e. suitable either for the impression of the complete upper or lower dental arcade or for a section of the upper or lower dental arcade. Said impression trays are generally made of metal, namely aluminium or stainless steel or plastic and have a "U"-shaped section. Said impression trays are filled with plastic material, and then they are introduced into the mouth and pressed down on the dental arcade whose impression has to be taken. Thus the plastic material is impressed and takes the configuration of the dental arcade. When the impression has to be taken for both the upper arcade and lower arcade two single separate impressions are needed with a consequent loss of time and the risk of jeopardizing their precision when coupling both parts together. Usually, the impression tray is maintained in position through a finger pressure by the patient or by the dentist till the plastic material filling it has set. However, such a method is not safe as the pressure exerted by the fingers is not steady over the whole impression tray during the setting time of the impressing material and not be strong enough so that the result of the operation may be jeopardized. After the plastic material has set, the impression tray is removed from the patient's mouth by pulling it off the dental arcade with manual movements; this may cause deformations to the impression, which will jeopardize the subsequent work. Moreover, to avoid that the plastic material may remain stuck to the dental wall when removing the impression tray, impression trays are provided with a set of holes arranged on several rows, both on the side walls and on the bottom of the U-shaped section, over the whole extension of the impression tray. Thus, the plastic material in the impression tray exceeding the quantity required for the purposes of the impression can run out of the holes and cause a retention along with the impression tray. Therefore, this method requires the use of more plastic material than actually needed for the impression alone, with consequent higher costs. Impressions trays are also known, having a first and a second opposed recesses for receiving the material to be impressed, through which both the impressions of the upper and lower side of a patient's dental arcade can be taken simultaneously (see for instance DE-A-14 91 083, US-A-4,432,728, US-A-3,107,428, US-A-5,102,335). It is the object of the present invention to provide an impression tray for fixed dental prosthesis to obviate in a simple and safe way to the problems related to the known impression trays. To reach this purpose it is the object of the present invention an impression tray having the characterizing feature of claim 1. Further advantageous embodiments of the invention are contained in claims 2 to 15. The features and advantages of the impression tray according to the present invention will be apparent from the following description based on the annexed drawings, which are supplied only by way of a non limiting example, wherein: Fig. 1 shows a plan view of an impression tray according to the present invention; Fig. 2 shows a lengthwise section of an impression tray according to the present invention; Fig. 3 shows a rear view of an impression tray according to the present invention; Fig. 4 shows a side view of an impression tray according to the present invention; Fig. 5 shows a front view of an impression tray according to the present invention; Fig. 6 shows a plan view of a change to the impression tray according to the present invention; Fig. 7 shows a plan view of a second change to the impression tray according to the present invention; Fig. 8 shows a plan view of a third change to the impression tray according to the present invention. In Fig. 1, showing a plan view of an impression tray according to the present invention, reference number 1 indicates the impression tray, which in its plane position has substantially a U configuration following that of the dental arcade and consisting of both a buccal part and lingual part extending approximately to the retromolar trigone, whereas number 2 indicates a protruding part having a gripping function. The U configuration obtained allows the patient to move the tongue, swallow and breathe adequately, with less inconvenience for the patient during the impression stage. In Fig. 2 showing a lengthwise section of an impression tray 1 according to the present invention, numbers 3 and 4 indicate two walls, one outside and one inside to define laterally a substantially U-shaped recess 5 forming the upper part of the impression tray 1, said configuration following the one of the upper dental arcade; numbers 6 and 7 indicate two side walls, one outside and one inside to define laterally a substantially upturned U-shaped recess 8 forming the lower part of the impression tray 1, said configuration following the one of the lower dental arcade. Therefore, the two recesses related to the upper and lower dental arcade respectively are opposed to each other. Number 9 indicates a closing and joining wall for the opposed U-shaped recesses 5 and 8. The thickness of said wall 9 is not constant over the whole extension of the impression tray but varies from about 3 mm max. for the incisive area to about 1 mm min. in correspondence with the retromolar area, to comply with the closing angle of the mouth. Also, said joining wall 9 is extending in compliance with the Spee's curve . Moreover, also the width of the recesses 5 and 8 is not constant as it increases from the incisive area to the retromolar area to comply with the configuration of the dental arcade. Outside walls 3 and 6 are inclined by about 3 - 4 degrees inwards the respective recesses 5 and 8 to follow the configuration of the dental arcade. The height of the internal wall 4 with respect to the horizontal plane of the impression tray is lower than the height of the external wall 3, whereas the height of the internal wall 7 is higher than the external wall 6, in order to follow the configuration of the dental arcade. Always in order to follow the shape of the dental arcade, the external side wall 3 has a height varying from a maximum value in the front section to a minimum value in the rear section of the impression tray where it ends with rounded corners. Also the side wall 6, whose height is substantially constant, ends with rounded corners to avoid a contact with the mastication muscles. Each side wall 3, 4, 6 and 7 is provided with a row of holes having about 1.5 mm diameter, indicated with number 10. Said row of holes 10 is located at a distance from the plane of wall 9, which is equal to about 2/3 of the height of said side walls. A row of holes 10 is also obtained at the end of wall 9 in the retromolar area. At the end of the side walls 3, 4, 6 and 7 and over their whole extension a small tooth indicated by number 11 is provided, which is directed inside the recesses 5 and 8. The holes 10 and the small tooth 11 have the function to anchor the impression tray to the plastic material and allow the removal of the impression tray after taking the impression and the consequent setting of the plastic material. Number 2 indicates the handgrip of the impression tray, which is inclined downwards with respect to the horizontal plane of the impression tray. Thus, the impression tray can be easily removed from the mouth and obtain a more precise impression. In addition, said inclination reduces the friction of the patient's lips on the impression tray and will cause less inconvenience to the patient during the impression stage. In Fig. 3, showing a front view of an impression tray according to the present invention, numbers 3 and 4 indicate the walls defining the upper recess 5 of the impression tray, whereas numbers 6 and 7 indicate the walls defining the lower recess 8 of the impression tray. Number 9 indicates the common wall joining the recesses 5 and 8, whose inclination with respect to the horizontal plane of the impression tray determines an angle in compliance with the Wilson's curve . In Fig. 4, showing a side view of an impression tray according to the present invention, number 1 indicates the impression tray, number 2 indicates the handgrip of the impression tray and number 10 indicates the anchoring holes of the impression tray to the plastic material used for the impression. Number 13 indicates a reference notch to position the impression tray within the patient's mouth. After filling the recesses 5 and 8 with the required quantity of plastic material, the impression tray is introduced into the patient's mouth; the patient will maintain it in position simply through the closing pressure of the mouth till the impressing material has set. Thus, the obtained impression faithfully reflects both the upper and lower sections of the dental arcade in a natural closing position of the mouth. This will avoid any coupling errors that may arise when taking the two impressions separately, as done according to the known state of the art. To remove the impression tray from the mouth and avoid possible deformations to the impression just taken due to the adhesion of plastic material to the dental arcade, air is blown between the plastic material of the impression and the dental arcade using the syringe of the dental unit. In order to allow this operation (i.e. the syringe insertion), the side walls 3 and 6 have four small recesses, indicated by number 17, which are in correspondence of the teeth "23" and "13" (upper) and with the teeth "33" and "43" (lower); two of said recesses 17 are shown in Fig. 1, and the other two are symmetrically opposed recesses, not shown in Fig. 1, in line with the lower teeth. To ensure a correct position of the impression tray on the dental arcades, the external side of the impression tray has some reference notches, as indicated by numbers 12, 13, 14, 15 and 16 in Fig. 5. The notch 12 is located in correspondence with the central line of the dental arcade between the teeth 11-21 and 41-31, whereas the notches 13 and 14 are placed in correspondence with the side teeth 23-13 and "43"-"33" respectively. The notches 15 and 16 are located in line with the teeth "16"-"26" and "36"-"46" respectively. Said notches 12, 13, 14, 15 and 16 can be provided either raised or in low relief. Both the way and use of the impression tray according to the present invention will be apparent from the above description and annexed drawings. As it results from the above description, the impression tray for fixed prosthesis according to the present invention provides for the following advantages: one single operation is enough to impress both the upper dental arcade and lower dental arcade, as both impressions are obtained simultaneously; time saving for the patient and the dentist; higher precision for the impression; easy removal of the impression tray from the patient's mouth; less inconvenience for the patient's lips; less inconvenience for the patient to move the tongue, swallow and breathe; the impression tray can be easily placed in its correct position. It is obvious, without prejudice to the principle of the present invention, that many changes are possible to the manufacturing features of the impression tray described above by way of example without departing from the novelty spirit of the innovative idea, and it is also clear that in practical actuation of the invention the configurations and dimensions shown may differ from the ones described above and be replaced with technical equivalent elements. For instance, if only a section of the dental arcade has to be impressed, it is possible to change the configuration of the impression tray according to the illustration of Figs. 6, 7 and 8, i.e. reducing the length of the right side or left side or of both sides, but leaving the other dimensions and features unchanged.

Claims: Impression tray for fixed dental prosthesis, comprising an upper and a lower opposed recesses (5,8) adapted to receive a material to be impressed, for simultaneously obtaining upper and lower dental arcade impressions, the tray (1) comprising a common wall (9) from which a first outer peripheral wall (3) and a respective first inner peripheral wall (4) extend upwards, the latter being spaced inwardly from the former, said first walls (3,4) defining with said common wall (9) said upper recess (5), a second outer peripheral wall (6) and a respective second inner peripheral wall (7) extend downwards, the latter being spaced inwardly from the former, said second walls (6,7) defining with said common wall (9) said lower recess (8), characterized in that said common wall (9) is inclined with respect to the horizontal plane of the impression tray (1) in accordance with the Wilson's curve and the Spee's curve and has a variable thickness, namely from about 3 mm for the incisive area to about 1 mm in correspondence with the retromolar area. Impression tray, according to Claim 1, characterized in that said upper recess (5) has a substantially "U" shaped configuration, whereby said first outer wall (3) is inclined inwards said upper recess (5) and said first inner wall (4) is inclined outwards said upper recess (5). Impression tray, according to Claim 1 or 2, characterized in that said lower recess (8) has a substantially "U" shaped configuration, whereby said second outer wall (6) is inclined inwards said lower recess (5) and said second inner wall (7) is inclined outwards said lower recess (8). Impression tray, according to at least one of the previous claims, characterized in that at the end of said peripheral walls (3,4,6,7) a respective small tooth (11) is provided, which is directed inside the respective recess (5,8). Impression, tray, according to at least one of the previous claims, characterized in that on each of said peripheral walls (3,4,6,7) a row of holes is provided (10). Impression, tray according to Claim 5, characterized in that said holes (10) have about 1,5 mm diameter and are located at about 2/3 of the height of said peripheral walls (3,4,6,7) with respect to said common wall (9). Impression tray, according to to at least one of the previous claims, characterized in that reference notches (12,13,14,15,16) are provided, for a correct positioning of the impression tray (1) on the dental arcades. Impression tray, according to Claim 7, characterized in that one of said reference notches (12) is positioned in correspondence with the central line of the dental arcade, in correspondence of teeth "11"-"21" and "31"-"41". Impression tray, according to Claim 7, characterized in that one of said reference notches (13,14,15,16} is positioned in line with teeth "23" and "43", and/or teeth "13" and "33", and/or teeth "16" and "26", and/or teeth "36" and "46" of the dental arcade. Impression tray, according to Claim 1, characterized in that on said first and second outer walls (3,6) small recesses (17) are provided in correspondence of the upper teeth "23" and "13" and the lower teeth "33" and "43", for allowing air to be blown between the material used for obtaining said impressions and the dental arcade. Impression tray, according to Claim 10, characterized in that said small recesses (17) are provided in line with the upper teeth "23" and "13" and the lower teeth "33" and "43". Impression tray, according to Claim 1, characterized in that an downwards inclined handgrip (2) is provided on the front side of the tray (1). Impression tray, according to Claim 12, characterized in that , said handgrip (2) is inclined downwards with respect to the horizontal plane of the tray (1) by about 3-4 degrees. Impression tray, according to Claim 1, characterized in that the width of said upper and lower recesses (5,8) increases from the incisive area to the retromolar area. A method for simultaneously obtaining upper and lower dental arcade impressions by means of an impression tray according to one or more of the previous claims, comprising the steps of: i) filling the upper and the lower recesses (5,8) with the material to be impressed, ii) inserting the impression tray (1) into a patient's mouth, iii) maintaining the impression tray (1) between the dental arcades till the impressing material has been set, iv) removing the impression tray (1) from the patient's mouth, characterized in that step iv) comprises blowing air between said material and the dental arcade using a syringe of a dental unit.

Inventors: MIO ALESSANDRO, ZACCHEO ALESSANDRO IVANO, MIO, ALESSANDRO, ZACCHEO, ALESSANDRO IVANO
Applicants: MIO ALESSANDRO, ZACCHEO ALESSANDRO IVANO, MIO, ALESSANDRO, ZACCHEO, ALESSANDRO IVANO
Application year: 1997
Main classification: A61C9
IPC codes: A61C9, F04B39, F02M59, F04B9