This application claims priority to Taiwan Patent Application Serial No. 106114979, filed on May 5, 2017, the content of which is hereby incorporated by reference in its entirety.
The present invention relates to a retraction cord, especially a rolled retraction cord. The present invention further relates to a method for manufacturing the rolled retraction cord.
In dental therapeutics, gingival retraction is a special method to temporarily distend and retract the gingiva away from teeth. For instances, when the tooth has caries near or below the gingival margin, gingival retraction is adopted to fill the gingival sulcus to separate the tooth and gingiva so the caries of the tooth can be exposed for the dentist to perform restoration; for prosthesis fabrication, the margin of the abutment tooth needs to be fully and accurately impressed. Since the dental crown or bridge margin design needs to be level with or below the gingival margin, gingival retraction is adopted to expose the margin of the abutment teeth to complete the impression of the teeth below the gingival margin. The most common process of gingival retraction is to place a retraction cord into the gingival sulcus to retract the gingiva away from the tooth, and the retraction cord is withdrawn before the insertion of the impression material, so that the part of the abutment tooth that was originally covered by gingiva is completely exposed and an accurate and reliable impression of the tooth without gingiva interference can be taken. However, gingival bleeding often occurs during withdrawal of the retraction cord, and the gingival bleeding must be stopped before the impression can be continued. Therefore, the ideal retraction cord should have a certain degree of ductility and deformability to decrease gingival bleeding or gingival atrophy and to reduce the patient's pain and discomfort.
The conventional retraction cords are usually made of cotton or silk with different forming methods, such as a spun retraction cord, a twisted retraction cord, a braided retraction cord, and a knitted retraction cord. Further, to avoid bleeding or exudates, some conventional retraction cords are impregnated with the hemostatic agents prior to use.
The spun retraction cord, the twisted retraction cord, and the braided retraction cord are firm cords and can achieve gingival retraction effect. On the other hand, the firm cords have limited deformability, which easily causes gingival bleeding. The knitted retraction cord is hollow in cross section, and has better deformability to match the width of the gingival sulcus between the gingiva and the teeth than the firm retraction cords. However, the rough surface of the tooth can easily tear or shred the knitted retraction cord, resulting in the deviation of the dental impression, affecting the accuracy of the tooth mold production, and increasing the complexity of clinical treatment. Further, the conventional retraction cord containing hemostatic agents is usually acidic, is not applicable to all patients, and may cause tooth erosion. The conventional retraction cord is in linear contact with the gingiva of the patient, so the contact points are subject to greater pressure, are likely to cause discomfort or pain of the patient, and cause gingival bleeding, even permanent damages such as the gingival recession and degeneration.
In view of the drawbacks that the firm retraction cords have poor deformability, the knitted retraction cord is easily torn or shredded, and these conventional retraction cords cause gingival bleeding or tissue trauma and even permanent damage such as the gingival recession and degeneration, the objective of the present invention is to provide a rolled detraction cord with a smooth surface formed by a non-firm, non-knitted pattern to increase the plasticity, enhance ductility, and reduce gingival bleeding, ensuring that the teeth impression or other treatment can be carried out smoothly while reducing the patient's discomfort.
To achieve the above objective of the present invention, the present invention provides a rolled retraction cord having flexibility and made of a sheet rolled into a non-firm multilayer strip. The sheet comprises a first side edge and a second side edge, the first side edge and the second, side edge are opposite to each other, and the roiled retraction cord is formed by rolling the first side edge of the sheet toward the second side edge of the sheet.
According to the present invention, the term “non-firm,” as used herein refers to the rolled retraction cord of the present invention is not fully solid and is not fully hollow, and the rolled retraction cord has inside cushion spaces that allow the multilayer strip molding.
Preferably, the thickness of the sheet ranges from 0.05 mm to 0.15 mm.
Preferably, the outer diameter of the rolled retraction cord ranges from 0.2 mm to 5 mm.
Preferably, the rolled retraction cord has a middle section and two end sections, the two end sections are respectively between two ends of the first side edge and between two ends of the second side edge, and the middle section is between the two end sections, wherein the outer diameter of the middle section is larger than the outer diameter of the two end sections.
According to the present invention, the term “outer diameter” as used herein refers to a straight line distance between two opposing positions of the outer edge of the rolled retraction cord.
Preferably, the ductility of the sheet in a direction perpendicular to the first side edge and the second side edge is greater than the ductility in a direction parallel to the first side edge and the second side edge of the sheet.
Preferably, the sheet further comprises a folding portion formed by bending the sheet near the first side edge, and the folding portion is parallel to the first side edge.
Preferably, the sheet is formed by polytetrafluoroethylene fibers or expanded polytetrafluoroethylene fibers in a parallel arrangement, and the arrangement direction of the polytetrafluoroethylene fibers or the expanded polytetrafluoroethylene fibers is parallel to the first side edge and the second side edge of the sheet.
The present invention further provides a method for manufacturing the rolled retraction cord, comprising the steps of:
(A) preparing the sheet;
(B) placing the sheet on a first surface of a first forming member;
(C) contacting a first side edge of the sheet with a second surface of a second forming member, the first side edge of the sheet sandwiched between the first surface of the first forming member and the second surface of the second forming member; and
(D) applying a three via the first surface or the second surface to the sheet, and rolling the sheet from the first side edge to the second side edge to obtain the retraction cord.
Preferably, the method comprises a step (E) between the step (A) and the step (B) or between the step (B) and the step (C), wherein the step (E) is folding a folding portion close to the first side edge, and the folding portion is parallel to the first side edge.
Preferably, the second surface of the second forming member is in contact with the two ends of the first side edge of the sheet.
Preferably, the first forming member and the second forming member are flat plates, swash plates or rollers. More preferably, the first surface and the second surface include, but are not limited to, a plane, a slope, or a curved surface.
Preferably, the rolled retraction cord is made by means of a friction between the first surface of the first forming member and the second surface of the second forming member and the sheet, so that the sheet is rolled.
Preferably, the ductility of the sheet in a direction perpendicular to the first side edge and the second side edge is greater than the ductility in a direction parallel to the first side edge and the second side edge of the sheet.
Preferably, the sheet is formed by polytetrafluoroethylene fibers or expanded polytetrafluoroethylene fibers in a parallel arrangement, and the arrangement direction of the polytetrafluoroethylene fibers or the expanded polytetrafluoroethylene fibers is parallel to the first side edge and the second side edge of the sheet.
The rolled retraction cord of the present invention is a non-firm body formed by a rolled sheet which has higher plasticity than conventional firm retraction cords, and is less likely to cause stress on the gingiva that results in bleeding and pain. Compared with the rough surface of the conventional retraction cord, such as the hollow knitted retraction cord and the firm retraction cord, the rolled retraction cord of the present invention has a smooth surface. Further, the rolled multilayer structure of the rolled retraction cord has good malleability to be easily pressed into the gingival sulcus. Furthermore, during the dental retraction by using the rolled retraction cord, the rolled retraction cord is in plane contact with the gingiva, so that the gingiva are uniformly under pressure to educe gingival bleeding or discomfort of the patient. The rolled retraction cord of the present invention is less prone to tear, shredding, or frizz, the impression of the tooth mold can be more accurate, and bleeding can be mitigated during the withdrawal of the retraction cord compared with the conventional retraction cord.
Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
Before the present invention is described in greater detail with reference to the accompanying embodiments, it should be noted herein that like elements are denoted by the same reference numerals throughout the present invention.
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In other embodiments, the material of the sheet 10 can be expanded polytetrafluoroethylene (ePTFE), also called GORE-TEX®, and the outer diameter D1 of the rolled retraction cord 1 is from 0.2 mm to 2 mm, which is suitable for placing the rolled retraction cord 1 in the gingival sulcus between the teeth and the gingiva.
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In another embodiment, the second forming member 30 can be fixed while pressing the first forming member 20 from the first side 11 of the sheet 10 toward the second side 12. In another embodiment, the second forming member 30 is pressed against the first side edge 11 of the sheet 10 by the first side 11 toward the second side 12 while the first forming member 20 is moved by the first side edge 11 of the sheet 10 toward the first side edge 11.
In the rolling process, the sheet 10 is pressed and pushed by the first surface 21 and the second surface 31 so that the rolled retraction cord 1 is rolled more closely; in other words, the tightness of the rolled retraction cord 1 is proportional to the force exerted on the rolled retraction cord 1 during rolling. In the roiling process, the first forming member 20 and the second forming member 30 press-fit the sheet 10 so that there is no gap between the sheets 10 (as shown in
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In use, depending on the width of the gingival sulcus or the state of gingival health, the dentist selects among a collection of retraction cords 1 of different external diameters or different levels of softness. Referring to
In another state of use, in view of the gingival condition of the patient, the dentist stretches the retraction cord 1 in a lateral direction first, in other words, stretching perpendicularly to the direction of the polytetrafluoroethylene fibers, and then proceeds with the retraction.
Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and features of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of contour, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Number | Date | Country | Kind |
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106114979 | May 2017 | TW | national |