Optical waveguides – Optical fiber bundle – Transition between geometric shapes
Reexamination Certificate
1998-07-29
2001-03-27
Spyrou, Cassandra (Department: 2872)
Optical waveguides
Optical fiber bundle
Transition between geometric shapes
C385S115000, C385S134000, C433S029000, C606S015000, C606S017000, C607S093000, C362S554000, C362S572000, C362S573000
Reexamination Certificate
active
06208788
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to apparatus and methods for light activation of hardening material. More particularly, the present invention is directed to apparatus and methods for activating dental compositions on a person's teeth. The apparatus and methods for activating dental compositions utilize a fiber optic funnel configured to focus radiant energy on a tooth of a person being treated.
2. Relevant Technology
Hardenable materials which are activated by radiant energy are commonly used in dentistry as sealants, adhesives and as filling material in dental preparations. Such hardenable materials are typically activated by exposure to radiant energy in a preselected spectral range, typically in either the long-wave ultraviolet light or blue visible spectrum. The light utilized to activate the hardenable material, or more specifically the photocurable material, is typically tailored specifically to the type of material.
A light curing unit containing a reflector lamp is used to irridate the photocurable material by directing light from the reflector lamp through a light guide positioned with its distal end adjacent to the photocurable material to be cured. The light guide functions to channel the light to the material located on a dental substrate during a dental procedure.
FIG. 1
schematically depicts a source of light
10
as utilized in a conventional light curing unit and light guide.
FIG. 1
corresponds with
FIG. 1
of U.S. Pat. No. 5,371,826, which is incorporated herein by reference. The source of light comprises a lamp filament
12
and a parabolic reflector
11
; the light source is an example of means for generating light and then providing light to a light guide. The lamp filament
12
is disposed on the optic axis
13
within the light source
10
to reflect cones of light
17
off the reflector
11
toward a focal spot where light guide
15
is positioned. Light guide
15
has a light-receiving surface
14
oriented perpendicular to the optic axis
13
to receive the incident cones of light
17
. The cones of light
17
are received at an acceptance angle which for maximum efficiency, should be as large as possible. The mathematical sine of the maximum acceptance angle, known as the numerical aperture, is determined by the optical properties of the fiber optic material and its shape The diameter of the light guide
15
at the light-receiving surface
14
is selected to maximize the efficient collection of light incident at the focal plane, coinciding with the light-receiving surface
14
, and is generally in a range of between 8-13 mm. It is conventional for light guide
15
to have a curved end section
16
to satisfy the requirements of maneuverability and accessibility of the light guide
15
for placement in the oral cavity of a dental patient. The curved section
16
has a radius of curvature which is chosen in proportion to the diameter of the curved end of the light guide
15
, with an angle of curvature of from, thirty degrees (30°) to sixty degrees (60°), for a diameter range of between about 8 mm to about 16 mm.
Conventional light guides are generally either fiber optic conductors or are solid conductors formed from glass or plastic. Light guides formed with fiber optics typically contain multiple strands of glass fiber held together as a flexible bundle or as a solid rod of fused individual fibers.
The use of such light guides with light curing units enables a dental practioner to rapidly harden compositions such that many dental procedures can be efficiently completed. It is often difficult, however, to direct sufficient light to only a small specific area without also directing light to areas which preferably do not receive any radiant energy. Many conventional light guides have diameters of about 11 mm or about 8 mm which is often larger than a typical dental preparation. Accordingly, smaller diameter light guides, such as those having diameters of about 2 mm, are also available. However, using light guides with smaller diameters also results in less light being delivered to the photocurable material. Additionally, the need for light guides with different diameters increases the costs of dental procedures.
An attempt to overcome the problems associated with delivering an optimal amount of light to relatively small areas is disclosed in U.S. Pat. No. 5,371,826. U.S. Pat. No. 5,371,826 discloses a fiber optic light guide which is tapered for concentrated delivery of light. More specifically, the fiber optic strands bundled together in the light guide each have a taper such that the diameter of the guide is less at the distal end than it is at the proximal end. To form such a tapered light guide, each fiber optic strand may be separately tapered, bundled and then fused together or a length of solid fiber optic may be stretched to form an elongated stretched section of conical geometry wherein each strand is uniformly tapered over the stretched section.
While the tapered light guide disclosed in U.S. Pat. No. 5,371,826 may be useful to deliver more light to a smaller area than is possible with conventional light guides, the tapered light guide only minimizes the problems associated with activating photocurable materials on dental substrates. Although the distal end has a diameter that enhances the ability of the light guide to be placed into smaller openings, it is still inadequate for some uses such as in a deep and narrow preparation. As indicated at column 3, line 64 to column 4, line 13, the taper angle is preferably relatively small to minimize the loss of light due to the angle of incidence becoming smaller than the critical angle. Claim 3 indicates that the taper angle for each fiber optic strand is preferably less than 0.1° and that the taper angle of the light guide is less than 5°. Accordingly, the diameter at the distal end of the light guide is not significantly less than the diameter at the proximal end of the light guide. Additionally, while the tapered light guide increases the concentration of the light delivered to a particular surface area as compared to conventional light guides, it is preferably to have even greater concentration in some circumstances than such slight tapers can deliver. Further, such tapered light guides fail to eliminate the need for multiple light guides having different diameters.
Such tapered light guides deliver large amounts of light compared to similarly sized light guides, however, such claims are primarily supported when the amount of light delivered is measured as the amount coming out of the distal end of the light guides. Even though a tapered light guide delivers more concentrated light, the light still tends to flare outward such that the diameter of the area that receives the light is much greater than the diameter of the distal end of the light guide. In clinical use, the distal end of the light guide is typically offset from the target photocurable material at a distance which produces flaring. Accordingly, the amount of light delivered to the target area is substantially less than amount of light exiting the distal end of the light guide. Comparative measurements taken to determine the amount of light delivered when the distal end of a light guide is offset from the target by about 1 cm indicate that the amount of light delivered by conventional light guides is not significantly different from supposedly more powerful light guides. Additionally, the flaring effect may also result in heat being potentially transferred to surfaces which are not intended to be targeted.
One method of reducing the offset distance between a distal end of a conventional light guide and the target photocurable material is the use of light tips attached to a light guide as disclosed in U.S. Pat. No. 4,666,405, which is incorporated herein by reference. The light tip has one end which is cone-shaped and the other end is configured for coupling with the distal end of a light guide.
FIGS. 2-5
depict light tips as disclosed in U.S. Pat. No. 4,666,405.
FIG. 2
Jr. John Juba
Spyrou Cassandra
Ultradent Products Inc.
Workman & Nydegger & Seeley
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