Cushion for dental implant

Abstract

A dental implant with a cushion device that can simulate the functions of natural human periodontal ligament (PDL) is provided.

Claims

1. A dental implant comprising: a base member; an abutment; an implant-abutment junction (IAJ) portion at one end of said base member to retain said abutment to said base member, so that said abutment is able to move within a predetermined distance along an axial direction of said base member; and a cushion means for providing a resistance force when said abutment is pressed to move relatively toward said base member in said axial direction and providing a bouncing back force when said abutment is released from said pressing, wherein the cushion means simulates functions of natural human periodontal ligament (PDL).

2. The dental implant of claim 1, wherein the dental implant shows at least two different slopes in an axial load-displacement profile when compressed, wherein a first slope simulates desmodontal tooth movement, and a second slope simulates periodontal tooth movement of a human natural tooth.

3. The dental implant of claim 2, wherein the first slope is in a range from about 2 to 20 m/N, preferably 5 to 20 m/N and more preferably 7 to 15 m/N; and the second slope is in a range from about 0.1 to 10 m/N; preferably 0.3 to 6 m/N and more preferably 0.6 to 3 m/N, wherein the first slope is greater than the second slope.

4. The dental implant of claim 3, wherein the first slope is in a range from about 7 to 15 m/N; and the second slope is in a range from about 0.6 to 3 m/N.

5. The dental implant of claim 1, wherein the dental implant shows a vertical load-displacement profile with at least two different compressive modulus values when compressed, wherein a first modulus simulates desmodontal tooth movement, and a second modulus simulates periodontal tooth movement of a human natural tooth.

6. The dental implant of claim 5, wherein the first modulus is in a range from about 0.3-40 MPa, preferably about 0.4-20 MPa, and more preferably 1.0-10 MPa; and the second modulus is in the range from about 0.7-550 MPa, preferably about 0.9-100 MPa and more preferably about 1.0-50 MPa, wherein the second modulus is greater than the first modulus.

7. The dental implant of claim 5, wherein the first modulus is in a range from about 1.0-10 MPa; and the second modulus is in the range about 1.0-50 MPa, wherein the second modulus is greater than the first modulus.

8. The dental implant of claim 1, wherein the cushion means comprises: a first cushion sandwiched between said IAJ portion and said abutment; a second cushion sandwiched between said abutment and said base member only in said axial direction; and wherein the first cushion and the second cushion are two separate members, wherein the first cushion and the second cushion have different modulus values or different thicknesses or different modulus values and different thicknesses.

9. The dental implant of claim 8, wherein the first cushion and the second cushion are made from different elastic materials having different modulus values, wherein the first cushion has a compressive modulus about 0.3-40 MPa; and the second cushion has a compressive modulus in the range from about 0.7-550 MPa, wherein the first cushion and the second cushion both have a thickness about 0.1 mm-about 1.0 mm.

10. The dental implant of claim 8, wherein the first cushion and the second cushion are made from different elastic materials having different modulus values, wherein the first cushion has a compressive modulus about 1.0-10 MPa; and the second cushion has a compressive modulus in the range from about 1.0-50 MPa, wherein the first cushion and the second cushion both have a thickness about 0.1 mm-about 1.0 mm.

11. The dental implant of claim 9, wherein the first cushion and the second cushion both have a same thickness, and the first cushion has a compressive modulus less than that of the second cushion.

12. The dental implant of claim 8, wherein the first cushion and the second cushion have different thicknesses and are made from a same elastic material having a compressive modulus about 0.3-500 MPa; wherein the first cushion has a thickness greater than that of the second cushion, wherein the first cushion has a thickness about 0.2 mm-1.0 mm, while the second cushion has a thickness about 0.1 mm-0.6 mm.

13. The dental implant of claim 8, wherein the first cushion and the second cushion have different thicknesses and are made from a same elastic material having a compressive modulus about 1.0-50 MPa; wherein the first cushion has a thickness greater than that of the second cushion, wherein the first cushion has a thickness about 0.3 mm-0.8 mm, while the second cushion has a thickness about 0.2 mm-0.4 mm.

14. The dental implant of claim 1, wherein the cushion means comprises: a second cushion sandwiched between said abutment and said base member only in said axial direction; and wherein the second cushion is a composite cushion comprising materials having different modulus values.

15. The dental implant of claim 14, wherein the second cushion is a lamellar-type composite cushion comprising two layers of different elastic materials, wherein one layer has a compressive modulus about 0.3-40 MPa, and has a thickness about 0.1-1.0 mm, while another layer has a compressive modulus about 0.5-500 MPa, and has a thickness about 0.1-1.0 mm.

16. The dental implant of claim 14, wherein the second cushion is a lamellar-type composite cushion comprising two layers of different elastic materials, wherein one layer has a compressive modulus about 0.4-20 MPa, and has a thickness about 0.2-0.8 mm, while another layer has a compressive modulus about 1.0-100 MPa, and has a thickness about 0.2-0.8 mm.

17. The dental implant of claim 16, wherein said one layer is closer to said abutment than said another layer, and said one layer has a compressive modulus less than that of said another layer.

18. The dental implant of claim 1, wherein the cushion means comprises: a first cushion sandwiched between said IAJ portion and said abutment; and wherein the first cushion is a composite cushion comprising materials having different modulus values.

19. The dental implant of claim 18, wherein the first cushion is a lamellar-type composite cushion comprising two layers of different elastic materials, wherein one layer has a compressive modulus about 0.3-40 MPa, and has a thickness about 0.1-1.0 mm, while another layer has a compressive modulus about 0.5-500 MPa, and has a thickness about 0.1-1.0 mm.

20. The dental implant of claim 19, wherein said one layer is closer to said abutment than said another layer, and said one layer has a compressive modulus less than that of said another layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Preferred embodiments of the present invention will be described in the following with the accompanying drawings, wherein like elements/parts are presented by like numerals.

[0022] FIG. 1 shows a cross-sectional view of a dental implant constructed in accordance with a first preferred embodiment of the present invention.

[0023] FIG. 2 shows a cross-sectional view of a dental implant constructed in accordance with a second preferred embodiment of the present invention.

[0024] FIG. 3A shows a cross-sectional view of a dental implant constructed in accordance with a third preferred embodiment of the present invention.

[0025] FIG. 3B shows a cross-sectional view of a dental implant constructed in accordance with a fourth preferred embodiment of the present invention.

[0026] FIG. 4 shows a cross-sectional view of a compressive testing set-up for determining the slope of a stress-strain profile (m/N), which may be transformed into compressive modulus (MPa).

[0027] FIG. 5 is a plot showing the results of compressive testing on single cushions (sample code, SP) (the second cushion 40 in FIG. 4) with different heat treatment conditions and/or different initial thicknesses, wherein - represents results of human molar (11.8 m/N, 1.1 m/N); -.square-solid.- represents an initial cushion thickness of 1.3 mm and heat treatment of 225 C., 4h (28.2 m/N); -.Math.- represents an initial cushion thickness of 5 mm and heat treatment of 225 C., 4h (60.7 m/N); -- represents an initial cushion thickness of 0.3 mm and heat treatment of 225 C., 8h (0.1 m/N); and -- represents an initial cushion thickness of 0.8 mm and heat treatment of 210 C., 2h (560.7 m/N).

[0028] FIG. 6 is a plot showing the results of compressive testing on double cushions (sample code, SP) with same material and different thicknesses, wherein - represents results of human molar (11.8 m/N, 1.1 m/N); -.square-solid.- represents an outer cushion thickness of 0.3 mm and an inner cushion thickness of 1.2 mm (10.3 m/N, 3.1 m/N); -.diamond-solid.- represents an outer cushion thickness of 1.0 mm and an inner cushion thickness of 1.0 mm (30.8 m/N); -- represents an outer cushion thickness of 0.8 mm and an inner cushion thickness of 0.8 mm (20.6 m/N); and -- represents an outer cushion thickness of 0.5 mm and an inner cushion thickness of 0.8 mm (15.1 m/N, 8.8 m/N).

[0029] FIG. 7 is a plot showing the results of compressive testing on double cushions with different materials and same thicknesses (0.5 mm), wherein - represents results of human molar (11.8 m/N, 1.1 m/N); -.square-solid.- represents an outer cushion of sample code Ca and an inner cushion of sample code WS (8.3 m/N, 2.8 m/N); -.box-tangle-solidup.-represents an outer cushion of sample code SP and an inner cushion of sample code WS (21.2 m/N, 11.1 m/N); and -.Math.- represents an outer cushion of sample code Ca and an inner cushion of sample code DT (16.8 m/N, 3.3 m/N).

[0030] FIG. 8 is a plot showing the results of compressive testing on single cushions with same material and different thicknesses, wherein - represents results of human molar (11.8 m/N, 1.1 m/N); -.square-solid.- represents an outer cushion of sample code C6-265 having a thickness of 0.35 mm (2.8 m/N); -- represents an outer cushion of sample code C6-265 having a thickness of 0.30 mm (2.0 m/N); -.Math.- represents an outer cushion of sample code C6-265 having a thickness of 0.2 mm (1.7 m/N); and -.diamond-solid.- represents an inner cushion of sample code C6-265 having a thickness of 0.1 mm (0.3 m/N).

[0031] FIG. 9 is a plot showing the results of compressive testing on double cushions with same material (sample code of C6-265) and different thicknesses, wherein - represents results of human molar (11.8 m/N, 1.1 m/N); -- represents an inner cushion thickness of 0.2 mm and an outer cushion thickness of 0.35 mm (14.5 m/N, 2.1 m/N); -.box-tangle-solidup.- represents an inner cushion thickness of 0.2 mm and an outer cushion thickness of 0.30 mm (7.2 m/N, 1.8 m/N); and -*- represents an inner cushion thickness of 0.1 mm and an outer cushion thickness of 0.20 mm (8.3 m/N, 1.4 m/N).

DETAILED DESCRIPTION OF THE INVENTION

[0032] The present invention includes the following aspects (but not limited thereto):

[0033] 1. A dental implant comprising:

[0034] a base member;

[0035] an abutment;

[0036] an implant-abutment junction (IAJ) portion at one end of said base member to retain said abutment to said base member, so that said abutment is able to move within a predetermined distance along an axial direction of said base member; and

[0037] a cushion means for providing a resistance force when said abutment is pressed to move relatively toward said base member in said axial direction and providing a bouncing back force when said abutment is released from said pressing,

[0038] wherein the cushion means simulates functions of natural human periodontal ligament (PDL).

[0039] 2. The dental implant of aspect 1, wherein the dental implant shows at least two different slopes in an axial load-displacement profile when compressed, wherein a first slope simulates desmodontal tooth movement, and a second slope simulates periodontal tooth movement of a human natural tooth.

[0040] 3. The dental implant of aspect 2, wherein the first slope is in a range from about 2 to 20 m/N, preferably 5 to 20 m/N and more preferably 7 to 15 m/N; and the second slope is in a range from about 0.1 to 10 m/N; preferably 0.3 to 6 m/N and more preferably 0.6 to 3 m/N, wherein the first slope is greater than the second slope.

[0041] 4. The dental implant of aspect 1, wherein the dental implant shows a vertical load-displacement profile with at least two different compressive modulus values when compressed, wherein a first modulus simulates desmodontal tooth movement, and a second modulus simulates periodontal tooth movement of a human natural tooth.

[0042] 5. The dental implant of aspect 4, wherein the first modulus is in a range from about 0.3-40 MPa, preferably about 0.4-20 MPa, and more preferably 1.0-10 MPa; and the second modulus is in the range from about 0.7-550 MPa, preferably about 0.9-100 MPa and more preferably about 1.0-50 MPa, wherein the second modulus is greater than the first modulus.

[0043] 6. The dental implant of aspect 1, wherein the cushion means comprises: a first cushion sandwiched between said IAJ portion and said abutment;

[0044] a second cushion sandwiched between said abutment and said base member only in said axial direction; and

[0045] wherein the first cushion and the second cushion are two separate members,

[0046] wherein the first cushion and the second cushion have different modulus values or different thicknesses or different modulus values and different thicknesses.

[0047] 7. The dental implant of aspect 6, wherein the first cushion and the second cushion are made from different elastic materials having different modulus values, wherein the first cushion has a compressive modulus about 0.3-40 MPa, preferably about 0.4-20 MPa, and more preferably 1.0-10 MPa; and the second cushion has a compressive modulus in the range from about 0.7-550 MPa, preferably about 0.9-100 MPa, and more preferably about 1.0-50 MPa, wherein the first cushion and the second cushion both have a thickness about 0.1 mm-about 1.0 mm.

[0048] 8. The dental implant of aspect 7, wherein the first cushion and the second cushion both have a same thickness, and the first cushion has a compressive modulus less than that of the second cushion.

[0049] 9. The dental implant of aspect 6, wherein the first cushion and the second cushion have different thicknesses and are made from a same elastic material having a compressive modulus about 0.3-500 MPa, preferably about 0.4-100 MPa, and more preferably 1.0-50 MPa; wherein the first cushion has a thickness greater than that of the second cushion, wherein the first cushion has a thickness about 0.2 mm-1.0 mm, preferably 0.3 mm-0.8 mm, while the second cushion has a thickness about 0.1 mm-0.6 mm, preferably 0.2 mm-0.4 mm.

[0050] 10. The dental implant of aspect 1, wherein the cushion means comprises:

[0051] a second cushion sandwiched between said abutment and said base member only in said axial direction; and

[0052] wherein the second cushion is a composite cushion comprising materials having different modulus values.

[0053] 11. The dental implant of aspect 10, wherein the second cushion is a lamellar-type composite cushion comprising two layers of different elastic materials, wherein one layer has a compressive modulus about 0.3-40 MPa, preferably about 0.4-20 MPa, and has a thickness about 0.1-1.0 mm, preferably about 0.2-0.8 mm, while another layer has a compressive modulus about 0.5-500 MPa, preferably about 1.0-100 MPa, and has a thickness about 0.1-1.0 mm, preferably about 0.2-0.8 mm.

[0054] 12. The dental implant of aspect 11, wherein said one layer is closer to said abutment than said another layer, and said one layer has a compressive modulus less than that of said another layer.

[0055] 13. The dental implant of aspect 1, wherein the cushion means comprises:

[0056] a first cushion sandwiched between said IAJ portion and said abutment; and

[0057] wherein the first cushion is a composite cushion comprising materials having different modulus values.

[0058] 14. The dental implant of aspect 13, wherein the first cushion is a lamellar-type composite cushion comprising two layers of different elastic materials, wherein one layer has a compressive modulus about 0.3-40 MPa, preferably about 0.4-20 MPa, and has a thickness about 0.1-1.0 mm, preferably about 0.2-0.8 mm, while another layer has a compressive modulus about 0.5-500 MPa, preferably about 1.0-100 MPa, and has a thickness about 0.1-1.0 mm, preferably about 0.2-0.8 mm.

[0059] 15. The dental implant of aspect 13, wherein said one layer is closer to said abutment than said another layer, and said one layer has a compressive modulus less than that of said another layer.

[0060] A dental implant constructed in accordance with a first preferred embodiment of the present invention is shown in FIG. 1, which comprises

[0061] a base member 10;

[0062] an abutment 20;

[0063] an implant-abutment junction (IAJ) portion 30 at one end of said base member 10 to retain said abutment 20 to said base member 10, so that said abutment 20 is able to move within a predetermined distance along an axial direction of said base member 10;

[0064] a first cushion 50 sandwiched between said IAJ portion 30 and said abutment 20,

[0065] a second cushion 40 sandwiched between said abutment 20 and said base member 10 only in said axial direction.

The Advantages of Our Inventive Design

[0066] The micromotion provided by the cushions, contributes towards a more natural function of the implant, rendering it an improved tooth-replacement. It promotes a more natural bite feel, and an enhanced interaction with the surrounding teeth. In addition, it enables the implementation of fixed bridging supported by a combination of an implant and a tooth, which is traditionally endangered by the discrepancy of the amount of micromotion exhibited by the tooth and the implant. However, perhaps the most prominent advantage of the implant with cushions is minimizing the amount of micromotion transferred from the bite load to the connecting interface between the implant and the surrounding bone, especially in the early stages of implantation where excessive micromotion at the root-form leads to fibrous encapsulation. (Werner et al., 2012)

Double-Cushion Design

[0067] For double-cushion design, although interchangeable, preferably the first (outer) cushion is a thicker, softer (lower modulus/less stiff), near-abutment donut-shaped cushion, and the second (inner) cushion is a thinner, harder (higher modulus/stiffer), near-root cushion.

Load-Displacement Slope

[0068] A cushioned dental implant with multiple cushions [Note: Double-cushion design is preferred], wherein the cushion(s) simulating natural PDL, has a vertical load-displacement profile with at least two different slopes (the first slope representing desmodontal TM, and the second slope representing periodontal TM) when compressed; wherein the first slope is in the range from about 2 to 20 m/N, preferably 5 to 20 m/N and more preferably 7 to 15 m/N; and the second slope is in the range from about 0.1 to 10 m/N; preferably 0.3 to 6 m/N and more preferably 0.6 to 3 m/N.

Modulus

[0069] A cushioned dental implant with multiple cushions, wherein the cushion(s) simulating natural PDL, has a vertical load-displacement profile with at least two different compressive modulus values (the first modulus representing desmodontal TM, and the second modulus representing periodontal TM) under compressive loading; wherein the first modulus is in the range from about 0.3-40 MPa, preferably about 0.4-20 MPa, and more preferably 1.0-10 MPa; and the second modulus is in the range from about 0.7-550 MPa, preferably about 0.9-100 MPa, and more preferably about 1.0-50 MPa.

Thickness

[0070] For a double-cushion dental implant, the two cushions can be made from different elastic materials having different moduli; or one or both cushions are composite cushions; or the two cushions having different thicknesses (even made from the same elastic material), therefore resulting in a vertical load-displacement profile with at least two different slopes (and different modulus values (desmodontal TM and periodontal TM).

[0071] For double-cushions having different thicknesses made from the same material, although interchangeable, preferably the first (soft, near-abutment) cushion is thicker than the second (stiffer, near-root) cushion.

[NOTE: For two cushions with different thicknesses made from the same material, the thinner cushion has a larger load-displacement slope]

[0072] For the double-cushion dental implant wherein the two cushions are made from different elastic materials having different modulus values, the first cushion has a compressive modulus about 0.3-40 MPa, preferably about 0.4-20 MPa, and more preferably 1.0-10 MPa; and the second cushion has a compressive modulus in the range from about 0.7-550 MPa, preferably about 0.9-100 MPa, and more preferably about 1.0-50 MPa. Each cushion has a thickness about 0.1 mm-1.0 mm.

[0073] For a double-cushion dental implant wherein the two cushions have different thicknesses and are made from the same elastic material, the first (soft, near-abutment) cushion has a thickness larger than the second (stiffer, near-root) cushion. The first cushion has a thickness about 0.2 mm-1.0 mm, preferably 0.3 mm-0.8 mm, while the second (stiffer, near-root) cushion has a thickness about 0.1 mm-0.6 mm, preferably 0.2 mm-0.4 mm.

[0074] For the double-cushion device, optionally there exists a space (gap) with a spacing of about 5-50 m, preferably 10-30 m, between the second cushion (the stiffer, near-root cushion) and an abutment to be pressed on the second cushion when the dental implant is compressed (Note: This is for further enhancing its similarity in load-displacement profile to natural teeth). This design is shown in FIG. 2, wherein a space (gap) 70 exists between the second cushion 40 and the bottom of the abutment 20.

[0075] For the double-cushion device, optionally there inserts an elastic layer of soft (low modulus) membrane with a thickness of about 5-50 m, preferably 10-30 m, between the second cushion (the stiffer, near-root cushion) and the abutment. This design is shown in FIG. 3A, wherein an additional elastic layer of soft (low modulus) membrane 80 sandwiched between the second cushion 40 and the bottom of the abutment 20. Further optionally there inserts an additional soft (low modulus) cushion 90 similar to the first cushion 50 between the IAJ portion 30 and the abutment 20, as shown in FIG. 3B.

[Note: This membrane should have a modulus similar to or lower than the first cushion modulus]
[Note: This is for further enhancing its similarity in load-displacement profile to natural teeth]
[Note: This design may be easier to fabricate than the above space between the second cushion and the abutment design shown in FIG. 2]

[0076] Cushion shape can be solid round, ring, flat, porous, etc.

[0077] The cushion is an elastomer, preferably a rubber and more preferably a silicone-based rubber. The elastomer may further comprise modulus-enhancing modifiers, such as ceramic, metallic or glass particles, whiskers or short fibers, carbon fiber, carbon black, CNT, graphite, carbon black, activated carbon, etc.

Single-Cushion Design

[0078] For the single-cushion design, the cushion is made of a composite material comprising at least two elastic materials with distinctively different compressive stress-strain modulus values; wherein the composite can be lamellar (at least two flat layers of different modulus values), particulate (one matrix and at least one particular reinforcement), or columnar (multiple columns with at least two different elastic materials with distinctively different modulus values), therefore resulting in a vertical load-displacement profile with at least two different slopes (desmodontal TM and periodontal TM).

[0079] For the lamellar-type single cushion comprising two different elastic materials (two flat layers), one layer has a compressive modulus about 0.1-10 MPa, preferably about 0.5-5 MPa, while the other layer has a compressive modulus 1-500 MPa, preferably 5-100 MPa.

[0080] Although interchangeable, preferably the soft (low modulus) layer is the near-abutment layer.

Method of Making an Elastic Cushion for Dental Implant

[0081] In order to adjust (usually to increase) the modulus (stiffness) of an elastic silicone-based cushion material (no matter commercially available or in-house made), a heat treatment at >150 C. for >0.1h, preferably at about 200-300 C. for about 0.1-24 h, and more preferably at about 210-250 C. for about 1-12h, is applied to the raw cushion material. This heat treatment may be either applied to the cushion material before shaping/forming into a final product, or applied to the cushion already formed into its final shape. Different thicknesses of cushions may be obtained by either rolling/compressing or directly cutting into different thicknesses.

[Note: Generally a thinner cushion had a larger load-displacement slope than a thicker cushion of the same material]

Materials Used for Tests

[0082] Table 1 lists the commercial silicone-based materials with different modulus values with or without heat treatment used for tests.

TABLE-US-00001 TABLE 1 Manufacturer/ Code of Company, Country Product name/type Material sample Dow Corning, USA DOW CORNING Silicone C6-265 C6-265 elastomer ELASTOMER Perfect Medical Catheter Silicone complex Ca Industry, Vietnam Perfect Medical Drainage tube Silicone complex DT Industry, Vietnam MISUMI Corp., Japan White silicone Silicone WS Wacker Chemie AG, Stirring plate Wacker Silicone SP Germany 70 [Note: Dow Corning C6-265 is a USP Class V medical grade material which has passed biocompatibility test and is referenced in FDA 21 CFR 177.2600 as Substances for Use Only as Components of Articles Intended for Repeated Use]

Method of Making a Silicone Rubber Sheet (Cushion) for Tests

[0083] To prepare a series of cushions with different modulus values for tests, a medical grade silicone (Wacker Chemie AG, Germany) was heat-treated to different temperatures for different periods of time. [Note: Within the present temperature and time ranges, a higher temperature and/or longer time generally resulted in a higher modulus]. An appropriate amount of the silicone was placed between two acrylic plates which were coated with a layer of petrolatum for lubrication purpose. The silicone was then placed in a furnace at different temperatures for different periods of time to obtain different levels of modulus (stiffness), followed by cooling in air. The thickness of the silicone rubber sheet was controlled by controlling the space between the two acrylic plates.

Compressive Test of Cushions

[0084] The compressive testing was conducted using a Shimadzu universal testing machine (Autograph AG-X 10 kN, Shimadzu, Japan) at a constant crosshead speed of 1 mm/min. The compressive testing set-up is shown in FIG. 4, wherein the first cushion is designated by a numeral of 50 (donut-shape with an outside diameter of 50 mm and an inside diameter of 30 mm) and the second cushion is designated by a numeral of 40 (round-shape with a diameter of 30 mm). Data analysis was conducted using an Origin system (OriginPro8, OriginLab Corp., USA) to determine the slope of a stress-strain profile (m/N), which may be transformed into compressive modulus (MPa).

TABLE-US-00002 TABLE 2 Materials, manufacturers, initial thicknesses, heat treatment conditions, compressive load-displacement slopes and compressive modulus values of cushions Sample code/ Initial sample 1.sup.st load- 1.sup.st 2.sup.nd load/ 2.sup.nd heat treatment thickness displacement modulus displacement modulus condition (mm) slope (m/N) (MPa) slope (m/N) (MPa) SP/210 C., 2 h 0.8 560.7 0.004 N/A N/A SP/225 C., 4 h 5 60.7 0.2 N/A N/A SP/225 C., 4 h 1.3 28.2 0.1 N/A N/A SP/225 C., 8 h 0.3 0.1 5.9 N/A N/A Double SP 1 + 1 30.8 1.7 N/A N/A Double SP 0.8 + 0.8 20.6 2.0 N/A N/A Double SP 0.5 + 0.8 15.1 2.7 8.8 4.6 Double SP 0.3 + 1.2 10.3 5.9 3.1 19.9 SP + WS 0.5 + 0.5 21.2 1.2 11.1 2.3 Ca + WS 0.5 + 0.5 8.3 3.1 2.8 9.0 Ca + DT 0.5 + 0.5 16.8 1.5 3.3 7.8 Double C6-265 0.2 + 0.1 8.3 1.2 1.4 7.1 Double C6-265 0.3 + 0.2 7.2 2.1 1.8 8.3 Double C6-265 0.35 + 0.2 14.5 1.2 2.1 8.4 C6-265 0.35 2.8 31.5 N/A N/A C6-265 0.3 2.0 37.5 N/A N/A C6-265 0.2 1.7 28.9 N/A N/A C6-265 0.1 0.3 45.8 N/A N/A

[0085] FIG. 5 shows the results of compressive testing on single cushions (the second cushion 40) with different heat treatment conditions and/or different initial thicknesses, and the results show: [0086] (1) Each profile has substantially one slope. [0087] (2) Within the test range, a higher heating temperature and/or longer heating time results a stiffer (larger load-displacement slope or higher modulus) cushion. [0088] (3) The load-displacement profile of the cushion may be manipulated to simulate that of human PDL with proper heat treatment.

[0089] FIG. 6 shows the results of compressive testing on double cushions with same material and different thicknesses, and the results show: [0090] (1) Double cushions with same thickness result in one-slope profiles. Double cushions with different thicknesses result in two-slope profiles. [0091] (2) The thinner cushion results in the stiffer cushion [0092] (3) Some profiles shown in this figure are close to the first slope (initial TM) of human PDL, but all are far less stiff than the second slope of human PDL.

[0093] FIG. 7 shows the results of compressive testing on double cushions with different materials and same thicknesses, and the results show: [0094] (1) Each profile has substantially two slopes. [0095] (2) The first slope of Ca(o)+WS(i) profile is close to the first slope of human PDL, and its second slope is close to the second slope of human PDL.

[0096] FIG. 8 shows the results of compressive testing on single cushions with same material and different thicknesses, and the results show: [0097] (1) Each profile has substantially one slope. [0098] (2) The thinner cushion results in the stiffer cushion [0099] (3) The slopes of the profiles are close to the second slope of human PDL,

[0100] FIG. 9 shows the results of compressive testing on double cushions with same material and different thicknesses, and the results show: [0101] (1) Each profile has substantially two slopes. [0102] (2) The first slopes of the profiles are very similar to the first slope of human PDL, and the second slopes are very similar to the second slope of human PDL.

REFERENCES

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