Light shield for dental apparatus

A light shield is provided for dental apparatus which shines light onto light curable material used to repair teeth. The shield is formed of a plastic material which substantially attenuates light in the blue range, and can be mounted onto the guide tube of the light gun utilizing engagement members defined between slits cut in the plastic sheet forming the body of the shield. The engagement members between the slits are displaced as the light shield is pressed onto the tip of the guide tube, with the engagement members then resiliently pressing against the periphery of the guide tube to firmly hold the shield in place. The shield can be easily removed by the dentist after the procedure with the patient is completed, and is economical so that it may be disposed of after one use.

FIELD OF THE INVENTION 
This invention pertains generally to the field of dental apparatus and 
particularly to shields for use with dental equipment which uses light to 
cure dental resins. 
BACKGROUND OF THE INVENTION 
In modern dentistry, materials are used in the repair of teeth which 
require the application of light, particularly blue light, and sometimes 
near ultraviolet light, to cure the material. Typically, a dentist uses a 
hand held light gun with a guide tube to direct the light to the area of 
the patient's teeth to which the light curable material has been applied. 
Common dental visible light activated resin systems are polymerized by 
blue light in the 470 nm range. To obtain proper curing, it is necessary 
that the light be applied to the material for a significant period of 
time, e.g., 30 seconds or more. To ensure that the light from the light 
gun is applied to the proper area, the dentist or hygienist generally must 
observe where the light is being applied during this time. 
Prolonged or repeated exposure to ultraviolet or blue light can lead to 
cataracts. Overexposure to relatively short wavelength visible light 
(e.g., less than 500 nm) may contribute to premature aging of the cornea 
and to senile macular degeneration. To avoid potential eye problems, 
dentists and hygienists commonly use light filters attached to their 
glasses which filter out the shorter wavelengths, or various types of 
light shields which are available as attachments to the light gun or which 
may be held separately from the light gun. 
Because of the increasing concerns with possible cross contamination 
between patients, dental equipment that is in contact with or proximate to 
a patient generally must be sterilized before it is used again with 
another patient or disposed of altogether. Light shields presently 
available which attach to the light gun are generally relatively 
expensive, and it is not economically feasible to dispose of these shields 
after use with one patient. Existing disposable light shields have 
typically not been as effective as the more permanent type of shields and 
not as convenient to use. In particular, disposable shields often are not 
easily placed on the light gun before use and easily removed after use by 
the dentist, especially where surgical gloves are used by the dentist or 
hygienist. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, a light shield is provided which 
is simple, easy to use, inexpensive so that it can be economically 
disposed of after one use, stable once in place on the guide tube of a 
light gun, and effective to protect the dentist's eyes from excessive 
exposure to potentially damaging wavelengths of light. The shield 
comprises a rounded, preferably oval sheet of crystalline styrene plastic 
which filters out a substantial portion, e.g., 97% or more, of the blue 
light (e.g., shorter than 500 nm) incident on the shield, and yet is 
substantially transparent to wavelengths longer than the blue or near 
ultraviolet wavelengths being filtered. In a preferred material, light in 
the wavelengths of 560 nanometers or less is substantially filtered. 
The shield is provided with slits that define resilient engagement members 
between them to provide a firm but adjustable mounting of the shield on 
the guide tube of a light gun. The engagement members are defined between 
the slits and, because of the resiliency of the plastic of the shield, 
will bend resiliently as the guide tube is inserted into the center 
intersecting point of the slits. The length of the slits is selected with 
respect to the standard diameter of the guide tube for typical light guns 
so that the guide tube fills a substantial portion but less than all of 
the radial area defined between the ends of the slits, so that the 
engagement members are deformed to press against the sides of the guide 
tube and hold the shield firmly in place on the guide tube without 
substantial distortion of the shape of the shield. The shield can be 
readily adjusted in position by the dentist by grasping the shield and 
sliding or rotating it with respect to the guide tube. The pattern of 
slits is preferably selected such that a cluster of shorter slits 
converges on the central point of the opening and is opposed by longer, 
more widely separated slits, which define wider engagement members than 
those defined between the shorter slits. Such a pattern of slits serves to 
more readily center the shield in position on the guide tube. 
Attachment of the shield to the guide tube is readily accomplished by 
simply pressing the end of the guide tube against the engagement members 
to press the guide tube through the hole defined by the deflected 
engagement members. When the procedure on the patient is completed, the 
shield is similarly easily removed by the dentist by simply holding the 
shield between the dentist's fingers and pulling it off the guide tube. 
The shield itself can be die cut from a sheet of plastic filter material. 
Moreover, the slits defining the engagement members can be readily die cut 
at the same time as the periphery of the shield, resulting in a simple, 
inexpensive, and precise forming operation for the shield. In this manner, 
the shield can be formed inexpensively so that it is economically 
disposable after use with a single patient. 
Further objects, features and advantages of the invention will be apparent 
from the following detailed description when taken in conjunction with the 
accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
With reference to the drawings, wherein like numerals refer to like parts, 
the light shield of the present invention is shown generally at 10 in FIG. 
1 mounted on the guide tube 11 of a light gun 13. The light gun 13 has a 
handle 14 by which the dentist holds the light gun with the tip 15 of the 
guide tube 11 adjacent to the teeth of the patient at the position at 
which the material to be cured is located. The light gun 13 is held by the 
dentist so that the shield 10 is interposed in his or her line of sight 
leading to the position at which light from the tip 15 of the guide tube 
is applied to the teeth. 
As illustrated in FIGS. 1 and 2, the light shield 10 has a sheet-like 
plastic body 17 with a rounded outer periphery 18. Resilient engagement 
members 19 are integrally formed in the plastic body 17 to engage against 
the outside of the tube 11 to hold the shield 10 in place on the tube. 
As shown in FIG. 2, the engagement members 19 are preferably defined 
between a "vertical" slit 21 and a "horizontal slit" 22 which are 
perpendicular and intersect at a central point 23, and two shorter slits 
24 which extend away from the central point 23 at approximately a 
45.degree. angle to the slits 21 and 22. Thus, it is seen that in the 
preferred engagement structure of FIG. 2, two engagement members 19 are 
formed above the horizontal slit line 22, while four engagement members, 
each being smaller than the engagement members defined between the slits 
21 and 22, are defined between the slit 22 and the slits 24, and between 
the portion of the slit 21 below the horizontal slit 22 and the adjacent 
shorter slits 24. 
As illustrated in FIG. 4, to emplace the shield 10 on the guide tube 11, 
the dentist holds the shield so that the tip 15 of the guide tube is 
pressed against the engagement members 19, and presses the tip 15 through 
the opening formed as the engagement members are pushed out of the way by 
the tip 15. The engagement members 19 then bend as shown in FIG. 1 to 
resiliently hold the shield 10 in place on the guide tube with the shield 
extending out generally perpendicularly to the guide tube. The dentist can 
easily adjust the position of the shield 10 on the guide tube by sliding 
it toward or away from the tip and by rotating it about the guide tube. 
When the procedure on the patient is completed, the dentist pulls the 
light shield off the guide tube and disposes of the shield. 
A preferred material for the body 17 of the shield is a crystalline styrene 
plastic with coloring material therein effective to filter out light in 
the blue and near ultraviolet range, and preferably to substantially 
filter out (97% or more) light wavelengths shorter than 560 nanometers. A 
suitable resin from which the film can be extruded is available under the 
name KRO4 K-Resin from Phillips Chemical Company, or Styron resin from Dow 
Chemical, with FDA approved coloring agents mixed therein (typically 
orange coloring) available from various suppliers (e.g., Spectrum Colors, 
Inc.), and such material in a thickness of 0.008 inch (8 mils) has been 
found satisfactory for the purposes of the present invention. A styrene 
material in this thickness can be readily die cut to cut the slits 21, 22 
and 24 to define the engagement members 19, and to define the outer 
periphery 18 of the shield. This material in this thickness also allows 
the engagement members 19 to resiliently deflect as they are engaged by 
the tip of the guide tube 15 to allow the guide tube to pass through the 
opening defined as these engagement members are deflected, allowing the 
engagement members to resiliently press against the surface of the guide 
tube to hold the shield in place. 
The light shield has a preferred shape as shown in FIG. 2, being 
substantially oval (elliptical) with the central point 23 of the slits 
located along the narrower central axis of the elliptical periphery 18 and 
off of the long axis of the ellipse. For example, the central point 23 may 
preferably be formed halfway between the long axis of the ellipse and the 
edge. Locating the engagement members at this position enables mounting of 
the light shield 10 on the tube at a position such that a relatively wide 
area of the shield is provided between the guide tube and the shield 
periphery 18 through which the dentist can observe the area of the teeth 
being treated with light. By placing the engagement members 19 close to 
but spaced away from the periphery, the plastic material of the shield is 
strong enough to prevent the pressure from the guide tube, as it deflects 
the engagement members 19, from tearing through the plastic. One advantage 
of utilizing shorter slits 24 at the lower portion of the opening, to 
define smaller engagement members 19 below the horizontal slit 22, is that 
less pressure is applied on these smaller engagement members as the guide 
tube is pressed against them than is applied against the larger engagement 
members 19 above the horizontal slit 22, thereby making it less likely 
that the plastic adjacent to the slits below the horizontal slit 22 would 
be torn as the shield is pressed onto the guide tube. 
In an exemplary preferred form, the shield periphery is an ellipse with a 
long axis of 3.0 inches and a short axis of 2.25 inches. The vertical slit 
21 is preferably 0.669 inch long, lying along the short axis of the 
ellipse, and the horizontal slit 22 is preferably 0.866 inch long and 
spaced 0.591 inch from the closest point of the periphery 18. The length 
of the portion of the slit 21 below the horizontal slit 22 is preferably 
0.276 inch, and terminates 0.315 inch from the nearest point of the 
periphery. The short slits 24 are also preferably 0.276 inch long, and 
extend at 45.degree. angles with respect to the slits 21 and 22. 
The shield of the present invention can be formed in an inexpensive manner 
by die cutting the shield from a commercially available base sheet of the 
material to form the body 17 of the shield. In a preferred process, a die 
is provided having a knife edge which cuts into the plastic base sheet to 
define the periphery 18 of the shield, and also has knife edges which 
simultaneously cut the slits 21, 22 and 24. Because the slits 21, 22 and 
24 converge on a central point 23 in the preferred pattern, no material 
need be removed from the body 17 of the shield to define the opening in 
the shield into which the tube 11 may be inserted, thereby simplifying the 
manufacturing process and allowing the shield to be produced in the 
simplest and most economical manner. 
It is understood that variations of the shield of the invention may be 
utilized without departing from the scope of the present invention. For 
example, the outer periphery 18 of the shield may be formed as a circle, 
or any other geometric form, although the oval shape as shown in FIG. 2 is 
preferred. Further, if desired, the engagement members which define the 
opening in the shield may be formed such that they do not meet at a 
central point 23 as illustrated in FIG. 2, but have a portion of the 
shield body removed so that a central opening may be formed between the 
ends of the engagement members 19. As noted above, this is not preferred 
since it results in an extra step in the manufacturing process. 
It is understood that the invention is not confined to the particular 
construction and arrangement of parts herein illustrated and described, 
but embraces such modified forms thereof has come within the scope of the 
following claims.