Dental thickness gauge

Dental thickness gauge is for gauging the space between a cusp and fossa during preparation for a restoration. The dental thickness gauge is a plurality of tabs in a set, with each tab being of a different thickness. The material of the tabs is tough and flexible.

BACKGROUND OF THE INVENTION 
This invention is directed to a dental thickness gauge for gauging the 
correctness of space between opposing teeth during preparation for a 
restoration to assure that adequate space is provided for a proper 
restoration. 
When the condition of a tooth requires a restoration, the tooth in question 
is prepared or cut down to both remove the portion which is decayed and to 
provide the space required for a proper restoration. When the restoration 
is to be a cast metal cap, a spacing of 1/2 millimeter thickness is 
required to provide enough metal to provide a sufficient strength to 
satisfactorily resist the forces involved in chewing. Because some facing 
teeth intergage with cusp and fossa, it is difficult to properly estimate 
the spacing therebetween. At present, dentists estimate the space and a 
great deal of experience is required. Thus, in some cases the space is 
more than is necessary, which means increased preparation time and excess 
removal of tooth structure. When the space is less than necessary, either 
the restoration is too thin or the patient must be called back for further 
preparation work to provide the necessary space for the restoration. 
Present dental practice and restoration materials require a 1/2 millimeter 
space for a cast metal restoration. When the crown is to be a porcelain 
crown, a space of 11/2 millimeters is required. This is because 1/2 
millimeter is required for the metal substructure and a millimeter for the 
porcelain to be fused to the surface of the metal substructure and which 
creates the tooth form. The porcelain must have a thickness of 1 
millimeter in order to give the restoration tooth shape and tooth color. 
Thus, the dental thickness gauge set requires a tab of 11/2 millimeters. 
In addition, when there are two such restorations facing each other, the 
set requires a tab of 3 millimeters. When there are two cast metal 
restorations opposite each other, the required space is 1 millimeter. When 
a cast metal restoration is to be used opposite a porcelain restoration, 
the required space is 2 millimeters. Thus, there is need for a dental 
thickness gauge which measures specific spaces in the mouth during 
preparation. 
SUMMARY 
In order to aid in the understanding of this invention, it can be stated in 
essentially summary form that it is directed to a dental thickness gauge 
which comprises a set of tabs, each of the tabs being of a thickness 
related to a dental preparation thickness and each of the tabs being made 
of a flexible, resilient and soft material so that when the preparation 
space is inadequate, the selected gauge is clamped between facing teeth. 
It is an object and advantage of this invention to provide a dental 
thickness gauge which comprises a set of tabs, with each tab being of a 
thickness suitable for measuring the space required for a particular 
dental restoration, with each of the tabs being made of a flexible, soft 
material so that it can be clamped when tooth spacing is inadequate for 
the selected restoration. 
It is a further object and advantage of this invention to provide a dental 
thickness gauge which is of easy and convenient use, and is of inexpensive 
manufacture so that it can be widely used both by the dentist during tooth 
preparation for a restoration and can be used in the dental laboratory for 
aiding in preparation of the required dental restoration. 
The features of the present invention which are believed to be novel are 
set forth with particularity in the appended claims. The present 
invention, both as to its organization and manner of operation, together 
with further objects and advantages thereof, may be best understood by 
reference to the following description, taken in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIGS. 2, 3, 4 and 5 show the dental thickness gauge 10 of this invention. 
The gauge comprises a series of tabs, which in the preferred embodiment 
comprise six tabs 12, 14, 16, 18, 20 and 22. Each of the tabs has a 
different thickness, in the direction normal to the sheet in FIG. 3. Each 
of the tabs is in the form of a finger which extends in the length 
direction normal to the sheet in FIGS. 4 and 5. Furthermore, each of the 
tabs has a width direction in the upright direction of the sheet as seen 
in FIG. 3 and normal to the two other directions. The width and length 
dimensions of each of the tabs is substantially the same and, in FIG. 3, 
the tabs are shown as lying adjacent to each other. Throughout most of 
their length, the tabs are of the same width and toward the outer free 
ends thereof, the tabs are narrowed to a tip. Tab 12 has walls 24 and 26 
which adjoin the sides 28 and 30 at their divergent end. The walls 
converge toward tip 32 so that at the tip the tab is more narrow than the 
major width of the tab between sides 28 and 30. Each of the other tabs is 
similarly configured. 
Each of the tabs is of a different thickness. As described above, 
particular thickness requirements are present in preparation of teeth and 
restorations so they properly fit. Tabs 12, 14, 16, 18, 20 and 22 are 
preferably respectively of thickness 0.5 millimeter, 1.0 millimeter, 1.5 
millimeter, 2.0 millimeter, 2.5 millimeter and 3.0 millimeter. The reasons 
for these particular thicknesses are discussed both above and below in 
this description. However, these thicknesses are based on present dental 
restoration and material technology, and changes in that technology may 
suggest different, or additional thickness gauges than those described 
herein. In addition, a different number of gauge tabs may be helpful or 
required with changes in materials used in dental restorations. 
The gauge tabs in the set are each separately used for a separate 
measurement. There is no need for stacking the gauge tabs with respect to 
each other to obtain a total thickness. Each gauge tab is used 
individually. However, for the sake of being able to find the desired 
gauge tab, it is preferable that the gauge tabs be retained in a set. In 
view of the fact that the material, described below, can be 
injection-molded, it is convenient to mold the several gauge tabs in 
association with a single tab holder. 
The particular thickness of each tab is defined in accordance with a 
particular need in dentistry to measure a particular space. The tabs of 
each are substantially the same width, with the distance between the sides 
28 and 30 being approximately the width of a tooth space, as is seen in 
FIG. 6. This permits each tab to be used to test the gap spacing without 
interfering with adjacent teeth. The tips of the tabs are narrowed, as 
described above, in order to permit them to be used where the region to be 
tested is less than the usual full tooth width. The length of each tab is 
sufficient that the adjacent tabs may be bent away and the selected tab 
can be placed between the teeth where the preparation space is to be 
tested. The tab is sufficiently long that a sufficient portion extends 
from the mouth that the dentist can pull upon it to see if it is indented 
by the teeth when they are in centric relation, or unindented so that it 
may be easily withdrawn. 
Tab holder 34 is a rectangular body of the same material as the tabs and 
the tabs are integrally molded therewith. The tabs are separate fingers 
lying adjacent to each other, and where the fingers join the tab holder 
body, circular cylindrical openings are provided parallel to the thickness 
of the tabs. Openings 36 and 38 are provided between the tabs on the right 
side of the body, as seen in FIG. 3, and openings 40 and 42 are provided 
between the tabs on the left side of that body. The openings relieve the 
stress raiser which would otherwise be present if the sides of the 
adjacent tabs lay together in a narrow slit. 
The nature of the material is very important to the proper utilization of 
the dental thickness gauge. The material is an injection-moldable 
rubberlike material. It is identified as Kraton G-7705 supplied by Shell 
Chemical Company. The material is flexible and soft; it is 
injection-moldable so that parts can be made economically; it has a high 
thermoplastic point at 425.degree. F. so that it can be sterilized without 
deformation. Preferable hardness is between a 25 and 30 Shore. With this 
material of this hardness, the gauge is flexible enough so that it can 
bend between the cusp and fossa of opposing teeth and so that it can be 
indented when the space between the opposing teeth is not as large as the 
thickness of the gauge. 
FIGS. 1, 6 and 7 shown teeth in various stages of preparation. Tooth 44 is 
to be prepared for a restoration. It faces tooth 46. As seen in FIG. 7, 
tooth 44 has cusp 48 which faces fossa 50. The dentist grinds away tooth 
44. He removes the decayed material and, in addition to the removal of the 
decay, the dentist must remove sufficient material to provide a space for 
the restoration. If the restoration is going to be a cast metal 
restoration, a 1/2 millimeter spacing is enough. If the restoration is 
going to be a metal substructure covered with fused porcelain, the spacing 
must be 1.5 millimeters. Assuming that it is to be a porcelain-on-metal 
substructure restoration, the dentist chooses tab 16 for testing the 
spacing. The patient opens his mouth; the dentist places the selected tab 
at the interengaging tooth surfacces; and the patient closes his mouth. As 
he closes his mouth, the tab flexes to fit the contours defined by the 
cusp and fossa. With the patient's jaw closed, the dentist attempts to 
withdraw tab 16. If there is inadequate space, the tab can be readily 
withdrawn because, even though it is flexed by the facing contours of the 
teeth, it is not indented by the teeth. However, if the space is 
inadequate, the tooth surfaces indent and grasp the tab and it is 
difficult to withdraw. The dentist can sense the inadequacy of the 
preparation space and cut to provide adequate space. He makes the 
additional cuts, places the selected tab between the tooth he has cut and 
the opposing tooth, and asks the patient to bite down. This position of 
the teeth is called the centric relation, when the teeth are in their 
closest position. With the jaws in centric relation, the tab follows the 
contours of the teeth because of the softness of the material. If the 
dentist pulls on the guide, in the direction of the arrow of FIG. 7, if 
there is inadequate spacing, he will not be able to easily pull the guide 
from between the teeth because the teeth indent into the tab and prevent 
easy withdrawal. If there is proper clearance, then the dentist will be 
able to easily slide the tab from between the teeth, even though it is 
flexed between the cusp and fossa. In this way, the dentist can assure 
himself that proper space is provided for a proper restoration. 
In the dental laboratory, the technician uses a similar procedure with the 
dental thickness gauge. The laboratory is provided with reproductions of 
the patient's upper and lower jaws. These reproductions are placed on an 
articulator which holds the reproductions in position. The laboratory 
technician places the selected tab for the type of desired restoration 
between the duplication of the prepared tooth and the opposing tooth. If 
the gauge indicates inadequate clearance, he knows he should not begin 
making this restoration without indicating to the dentist that there is 
inadequate clearance. 
The laboratory technician also uses the dental thickness gauge to help him 
in the fabrication of pontics. A pontic is a replacement for one or more 
teeth which are missing. The pontics are suspended by preparing a vital 
tooth on each side of the missing tooth area. A wax frame is prepared, 
including the abutments mounted on the adjacent vital teeth and the bridge 
therebetween. The structure is first built up in wax and, as it is built, 
the technician knows that he must have a 1 millimeter space between the 
metal frame and the opposing tooth so that there is proper thickness for 
the dental glass. Thus, when the technician is making the wax pattern, he 
uses the 1 millimeter gauge tab together with the wax structure on the 
articulator. With this relationship, he can remove wax or add wax so that 
the gauge shows he has the exact clearance that he needs. It is in this 
dental laboratory use that the 2.5 millimeter tab 20 becomes of value. 
When the technician is building up a pontic which requires a 1 millimeter 
glass space thereover, and the opposing tooth will receive a restoration 
of porcelain on metal, the total space will be 2.5 millimeters. Thus, 
after the pontic is prepared the technician can measure for adequate space 
for the porcelain-on-metal restoration. By use of the dental thickness 
gauge 10 of this invention, the proper clearance can be achieved under 
various circumstances. 
This invention has been described in its presently contemplated best mode 
and it is clear that it is susceptible to numerous modifications, modes 
and embodiments within the ability of those skilled in the art and without 
the exercise of the inventive faculty. Accordingly, the scope of this 
invention is defined by the scope of the following claims.