Matrix band retainer

1. A matrix band retainer for dental restoration comprising:

a unitary member of a stiff planar spring material formed to have an open ring substantially in a first plane, with the plane of said material of said ring perpendicular to said first plane, a tine at each end of said open ring, each tine extending substantially normal to said plane of said ring, with at least one said tine having a first portion of said planar material extending from the respective end of said ring and a second portion of said planar material extending from said first portion, at an angle to said first portion and adjoining said first portion, to define on one side a ridge, facing the other said tine, and on the other side a valley facing away from the other said tine;

the ring, the first portion of said planar material, the second portion of said planar material and the ridge being arranged so that, in use, the first and second portions of said planar material can press against respective first and second adjacent teeth, with said ridge pressing into the interproximal zone between said first and second teeth, and with the other said tine pressing against the opposite side of the same pair of adjacent teeth.

2. The matrix band retainer as claimed in claim 1 wherein said first portion of said planar material and said second portion of said planar material define an angle behind said ridge of 65° to 130°, the angle defined in a plane parallel to the plane of said ring.

3. The matrix band retainer as claimed in claim 2 wherein said angle behind said ridge is approximately 80°.

4. The matrix band retainer as claimed in claim 2 wherein said stiff planar spring material is between 0.7 mm and 1.1 mm thick.

5. A matrix band retainer for dental restoration comprising:

a unitary member of a stiff planar spring material formed to have an open ring substantially in a first plane, with the plane of said material of said ring perpendicular to said first plane, a tine at each end of said open ring, each tine extending substantially normal to said plane of said ring, with at least one said tine having a first planar portion extending from the respective end of said ring and a second planar portion extending from said first portion, at an angle to said first portion and adjoining said first portion, to define a ridge facing the other said tine; said first planar portion and said second planar portion defining an angle behind said ridge of 65° to 130°, the angle defined in a plane parallel to the plane of said ring; and the tine being bifurcated at the end distal from said ring, such that a distal portion of said first planar portion and a distal portion of said second planar portion are divided by a notch,

the ring, the first planar portion, the second planar portion and the ridge being arranged so that, in use, the first and second planar portions can press against respective first and second adjacent teeth, with said ridge pressing into the interproximal zone between said first and second teeth, and with the other said tine pressing against the opposite side of the same pair of adjacent teeth.

6. The matrix band retainer as claimed in claim 5 wherein each said tine is a mirror of the other.

7. The matrix band retainer as claimed in claim 6 wherein each said tine flares outward as it extends away from said ring.

8. The matrix band retainer as claimed in claim 7 wherein each said planar portion is sloped outward moving toward its distal end from the ring end so that the defined ridge converges toward the other tine moving toward the distal end.

9. The matrix band retainer as claimed in claim 6 wherein each of said first planar portion and said second planar portion is slightly concave on the outside face thereof.

10. The matrix band retainer as claimed in claim 6 wherein said first planar portion is substantially coplanar with the adjacent end portion of said ring.

11. The matrix band retainer as claimed in claim 6 wherein, when said matrix band retainer is in a rest condition the angle between the first planar portion of one tine and the first planar portion of the other tine is larger than the angle between the second planar portion of the first tine and the second planar portion of the other tine, but with the ring opened to an in-use condition the angle between the first planar portions is substantially the same as the angle between the second planar portions.

12. The matrix band retainer as claimed in claim 6 including a backing spring member secured around the outside of said ring of said unitary member such that at least with the ring expanded in use the outer ring member contributes to the clamping force pushing or pressing the tines together.

13. The matrix band retainer as claimed in claim 12 wherein said backing spring member is located around said unitary member by a plurality of tabs bent outward from said ring.

14. The matrix band retainer as claimed in claim 5 wherein said notch is substantially triangular, being defined by an edge of said distal portion of said first portion, an edge of said distal portion of said second portion and the line between the distal end of said first portion and the distal end of said second portion.

15. The matrix band retainer as claimed in claim 14 wherein said first planar portion includes an inward toe adjacent said distal end, extending from said edge of said first distal portion generally toward said second planar portion, and said second planar portion includes an inward toe adjacent said distal end extending from said edge of said second distal portion substantially toward said first distal portion.

16. The matrix band retainer as claimed in claim 5 wherein said angle behind said ridge is approximately 82°.

17. The matrix band retainer as claimed in claim 5 wherein said stiff planar spring material is between 0.7 mm and 1.1 mm thick.

18. A matrix band retainer for dental restoration comprising a first tooth engagement portion for engaging against one side of a pair of teeth, a second tooth engagement portion for engaging against the other side of said pair of teeth, and a spring member connecting between said first tooth engagement portion and said second tooth engagement portion biasing said portions to a closed condition where said engagement portions are separated by less than the width of a tooth, said first tooth engagement portion and said second tooth engagement portion each comprising a member of low thickness relative to its width and height having a narrow proximal portion connected with said spring and a wider distal portion extending away from said spring and a bend extending from said narrow proximal portion to said wider distal portion, dividing said tooth engagement portion into a first planar portion and a second planar portion and defining a ridge there between, the ridge of said first tooth engagement portion and the ridge of said second tooth engagement portion facing each other across a gap into which said teeth are interposed in use, such that, in use, the first and second planar portions of said first tooth engagement portion press against respective first and second adjacent teeth with said ridge pressing into the interproximal zone between the first and second teeth, and the second tooth engagement portion pressing against the other side of said pair of teeth.

19. The matrix band retainer as claimed in claim 18 wherein said thickness is between 0.7 mm and 1.1 mm.

20. The matrix band retainer as claimed in claim 19 wherein said first planar portion and said second planar portion define an angle of approximately 82°.

21. The matrix band retainer as claimed in claim 20 wherein each said tooth engagement portion is bifurcated, with a distal portion of said first planar portion and a distal portion of said second planar portion being separated by a substantially triangular open notch.