Radiopaque dental composite and materials

Radiopaque dental compositions, radiopaque dental markers, and methods for making such markers are described, as well as kits containing combinations of, inter alia, the markers, molds for making the markers, and materials for sculpting the markers. The compositions contain a radiopaque material, for example diatrizoate sodium, in a polymeric binder. The markers may be in the shape of teeth, and can be sculpted or ground to conform to a patient's gingival surface and to occlude with an opposing tooth. The marker can then be placed in a stent for purposes of making radiographs of a patient's mouth from which an oral surgeon can determine the optimal placement of a permanent dental implant.

FIELD OF THE INVENTION 
This invention relates to radiopaque compositions and devices made 
therefrom. In particular, this invention relates to a radiopaque 
composition made by combining a radiopaque material and a binder. The 
composition is molded into a radiopaque dental marker which may be in the 
shape of a tooth. The invention further relates to the method of making 
the markers as well as to kits containing, inter alia, the composition, 
molds, and/or finished, sculptable tooth-shaped radiopaque markers. 
BACKGROUND OF THE INVENTION 
Dental restoration is an important and highly technical subcategory of the 
dental specialty of prosthodontics. Many important and significant 
developments have occurred in this field since the days of President 
Washington and his set of wooden dentures. Although conventional cemented 
or removable prosthetic devices, for example, bridges, partial dentures, 
and complete dentures, are still used widely in dentistry, it is now more 
and more prevalent to find dental patients receiving permanently implanted 
individual replacement teeth. In many cases such permanent replacement 
teeth are preferred over removable prostheses, but at the present time the 
process involved in the actual fitting of permanently implanted 
replacement teeth is quite complicated and difficult to perform with 
accurate results. 
The fitting of an implant-retained replacement tooth in place of a missing 
tooth in a patient's mouth requires several complicated steps. In order to 
anchor the replacement tooth in the patient's mouth, an implant must be 
placed into the patient's jaw. This implant will provide an anchoring 
device for the abutment(s) and screw(s) which will eventually hold the 
replacement tooth. However, it is difficult to properly locate sufficient 
maxillary or mandibular bone in which to fix the implant so that optimum 
security and positioning of the replacement tooth is achieved. Due to the 
fact that the bone structure and the density or mass of the underlying 
bone is not readily apparent on radiographs, implants are frequently 
positioned in a location where the bone structure is insufficient to form 
a proper anchoring position for the implant. This can ultimately lead to 
the failure of the implant. In addition, if the implant is seated at an 
improper angle an unaesthetic cosmetic appearance is achieved and, perhaps 
more importantly, improper occlusion results. 
U.S. Pat. No. 5,015, 183, issued to Fenick, partially addressed some of the 
earlier problems in the placing of such implants. That patent describes a 
method and device for placing an implant or artificial tooth in optimal 
bone structure by providing a radiology stent with a radiopaque grid 
contained within the stent. The stent is placed in the vicinity of the 
void where the implant is to be placed. A series of x-rays at oblique 
angles at spaced intervals along the implant provides grid points for 
determining the optimum trajectory of the proposed implant. The angles are 
then related to a formed surgical stent having a guide for directing a 
drill bit in the direction established by the radiology stent. In this 
device, and in other devices typically used in determining angle of 
placement of abutments for implants, metal wires serve as the radiopaque 
materials. Alternatively, in some cases, metal spheres may also serve as 
radiopaque markers. A principal disadvantage of the use of metal in x-ray 
radiography is that the metal can introduce distortional artifacts on the 
final radiograph. When angle of drilling trajectory is calculated based 
upon x-ray radiographs, such distortion can introduce significant error. 
As noted above, such error can lead to placement of abutments in bone of 
less than optimal mass or density, and/or at improper angles. 
In addition, positioning of radiopaque metal wires or spheres in a stent 
such as that described in U.S. Pat. No. 5,015,183 does not provide an 
optimally accurate positioning vis-a-vis the gingival surface and the base 
of the replacement tooth. This can introduce further drilling error, 
further seating error, and once again can lead to a less than optimal 
anchoring of the replacement tooth. Furthermore, use of such a stent 
cannot provide an optimally accurate indication of the ultimate anatomical 
configuration of the replacement tooth. Without a knowledge of this final 
configuration, the best drilling angle may still not be achieved, and the 
best occlusal positioning may not be possible. This is due to the fact 
that peculiarities of tooth shape, occlusal angles, etc., in the final 
replacement implant may be such that an oral surgeon cannot use the most 
advantageous drilling angles for that particular tooth, even if those 
angles have been correctly calculated. Using a stent such as those known 
in the prior art in determining those drilling angles does not allow an 
oral surgeon to appropriately compensate for anatomical peculiarities. 
Additionally, the method of making tooth-shaped forms currently recognized 
in the art is a complicated process involving several steps. First, the 
patient's dentist would make an impression of the patient's teeth. That 
impression would then be provided to a laboratory technician who would 
make stone models based upon the impression. The replacement teeth would 
then be designed and fabricated in wax from the stone mold. This 
multi-step process introduces error and variance in the size, shape, and 
most importantly in the occlusal conformation of the replacement tooth. It 
is also a time-consuming operation and an especially inefficient means of 
making forms for individual teeth. 
Therefore, a significant need exists for a reference device for radiography 
that will provide a more accurate determination of proper drilling angles 
for better positioning of implants, and which does not create the 
distortion of x-ray images which can be generated by metallic objects. 
Ideally, such a reference device would be tooth shaped and would be made 
of a material which could be easily sculpted or modified in shape after it 
is molded so that it can serve not only as a radiopaque reference device 
for determination of drilling angles on a radiograph, but also as an 
accurate indicator of the final anatomical form and shape of the 
replacement tooth. The latter advantage would allow an oral surgeon to 
interpret simultaneously not only the proper angles for drilling vis-a-vis 
the underlying bone structure but also to take into account any 
peculiarities in the tooth shape which might require adjustment of those 
angles for the final drilling process. 
SUMMARY OF THE INVENTION 
The present invention addresses these problems by providing radiopaque 
compositions which can be molded into a tooth-shaped radiopaque dental 
marker or reference device, as well as the tooth-shaped radiopaque markers 
themselves. The marker can be sculpted or modified in shape to provide for 
the determination of optimal drilling angles on x-rays, and at the same 
time allow for adjustments based upon occlusal surface angles and 
peculiarities of tooth confirmation. Furthermore, the makeup of the 
radiopaque composition is such that the reference device can be modified 
to a surgical guide which can be drilled through in situ, thereby allowing 
for optimal placement of permanent implants. The invention also relates to 
a method of making radiopaque dental markers in the shape of teeth, and to 
kits containing, in various embodiments, combinations of the composition, 
molds for the markers, pre-molded dental markers, drill bits, and tools 
for shaping and modifying the markers. Premolded markers can be in the 
shape of teeth or in the shape of balls or spheres. 
The radiopaque marker of the present invention comprises a moldable, 
sculptable radiopaque compound molded in the shape of a tooth, or, 
alternatively, in the shape of a ball or sphere. The marker can take the 
general shape of any tooth, for example, a molar, a cuspid, a bicuspid, or 
an incisor. The compound comprises a radiopaque material, for example, 
diatrizoate sodium, barium sulfate, iodine, or barium, and a binder, for 
example urethane, acrylic, or epoxy. The radiopaque material will, in one 
embodiment, comprise from about 10% to about 80% weight/volume (w/v) of 
the compound; in a preferred embodiment from about 15% to about 70% (w/v); 
and in a currently most preferred embodiment, from about 20% to about 60% 
(w/v) of the compound. 
Tooth-shaped markers can be molded with hemispherical bases, for 
point-to-point contact with the gingival surface of a patient, or with 
lengthened bases which can be sculpted or ground to abut the edentulous 
ridge of a patient. Either variation of the method allows an oral surgeon 
to determine the optimal drilling parameters for implant placement. The 
marker can be further sculpted for proper occlusion with opposing teeth. 
The kits of the present invention comprise combinations of at least two 
tooth-shaped dental markers, at least one in the general shape of a first 
type tooth, and at least one in the general shape of a second type tooth. 
The teeth included will be selected from the general types of teeth noted 
above. In additional alternative embodiments, the kits can also include 
molds for making markers, along with materials for making the composition 
of the invention, stabilizing struts for making stents for use in a 
patient's mouth, and instruments for sculpting, grinding and/or drilling 
the markers, and combinations thereof.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The radiopaque dental marker of the present invention comprises a 
sculptable radiopaque compound which is molded into the general shape of a 
tooth or sphere and then hardened or cured. The compound, as discussed 
below, comprises a radiopaque material and a binder. The molded radiopaque 
marker can take the form of any of the teeth found in the human mouth, or 
the form of any tooth of any dentulous animal. In a preferred embodiment 
of the marker, the radiopaque material used in the formation of the marker 
is diatrizoate sodium. In a further preferred embodiment, the base of the 
marker is rounded or hemispherical, so that the marker, when placed in a 
radiopaque stent, makes a single point of contact with the surface of the 
gingiva of the patient. In an alternative preferred embodiment, the 
radiopaque dental marker is molded so that the length of the base of the 
marker is elongated. The base of the marker is then ground to fit 
precisely over the edentulous ridge of a particular patient. In either 
case, the use of the marker allows an oral surgeon to precisely determine, 
from a radiograph or a radiographic series, the depth of the gingival 
tissue between the base of the marker and the underlying bone, as well as 
the relationship between the marker (and ultimately the permanent implant) 
and the underlying bone in which the implant must be anchored. 
In a particular embodiment, the radiopaque composition comprises a 
polymeric binding material combined with a radiopaque material. In a 
preferred embodiment the radiopaque material is diatrizoate sodium. Other 
radiopaque materials can be used, however, including, for example, barium 
sulfate, iodine, barium, or mixtures thereof. In one embodiment of the 
radiopaque composition, the radiopaque material comprises from about 10% 
to about 80% weight/volume (w/v) of the composition. In a preferred 
embodiment, the radiopaque material comprises from about 15% to about 70% 
w/v, and in currently most preferred embodiments from about 20% to about 
60% w/v of the composition. In one embodiment, the binding material is a 
dental acrylic, for example, a tooth color, cold cure, acrylic resin, such 
as methyl methacrylate. In an alternative embodiment, the binding material 
is an epoxy. In a currently preferred embodiment, diatrizoate sodium 
(e.g., HYPAQUE.TM., Winthrop Pharmaceuticals) is mixed with urethane in 
order to arrive at the radiopaque composition of the invention. 
The present invention also relates to a method of making a radiopaque 
dental marker in the shape of a tooth for radiographic purposes. The 
following exemplary steps may be followed in a preferred embodiment of the 
method of the invention: First, a moldable radiopaque compound comprising 
a radiopaque material and a binder is mixed. The radiopaque compound is 
then poured into a wax mold, preferably in the shape of a tooth (for 
example, a human tooth), alternatively in the shape of a ball or sphere. 
The molded material is allowed to cure and dry, and is then removed from 
the mold. As discussed above, the moldable radiopaque compound is, in a 
preferred embodiment, a combination of diatrizoate sodium and urethane or 
an acrylic (e.g., methylmethylacrylate) or an epoxy. Alternatively, the 
moldable radiopaque compound can be a mixture of barium sulfate and 
urethane or an acrylic or an epoxy. Of course, other materials having 
similar desired characteristics may also be used. The method can also be 
refined so that the gingival base of the radiopaque marker is rounded or 
in a pear or hemispherical shape, such that after the marker is modified 
in shape, the base of the marker will make point-to-point contact with the 
surface of the gingiva in such a way as to allow an oral surgeon to 
determine, from a radiograph or a radiographic series, the optimal 
drilling site and angles for implant placement. Alternatively, the method 
can involve the molding of a marker having a base lengthened sufficiently 
to allow the base to be ground to fit precisely over the edentulous ridge 
of a patient. The method of the present invention also can be refined to 
include the modification of the shape of the dental marker so that a 
proper occlusion will occur with the opposite tooth of the patient, and so 
that the marker bears a conformation approximating that of the final 
implant. A stent can then be made which includes the ground, sculpted 
marker and a nonradiopaque stabilizing strut. The stent can then be placed 
in a patient's mouth and a radiograph (or a series of radiographs) can be 
made which allow an oral surgeon to determine the optimal drilling site 
and angle for placement of a permanent implant. The oral surgeon can also 
make judgments regarding adequate adjustments for the tooth's positioning 
peculiarities in the process of surgically placing the implant. 
The present invention also relates to kits comprising radiopaque dental 
markers for radiography. In one embodiment of such a kit, at least two 
such dental markers are included, at least one in the general shape of a 
first type tooth, and at least one in the general shape of a second type 
tooth, the markers being independently selected from the group consisting 
of, for the maxillary teeth, right and left central incisors, tight and 
left lateral incisors, right and left cuspids, a bicuspid capable of use 
on either the right or left side, a right molar, and a left molar. For the 
mandibular teeth, the markers are independently selected from the group 
consisting of an incisor capable of use on the right or left and in either 
the central or lateral position, a right cuspid, a left cuspid, a bicuspid 
capable of use on either the right or left side, a right molar, and a left 
molar. In alternative embodiments, the teeth will be of a small or a large 
size, and in all cases the bicuspids and the mandibular incisor will be of 
a more generic shape. The kits, in alternative embodiments, also comprise 
combinations including additional teeth. In addition, alternate 
embodiments of the kits also comprise various combinations of the 
following: molds for making the radiopaque dental markers along with an 
amount of the elements of the radiopaque compound of the present 
invention, as well as stabilizing struts for the construction of stents 
containing one or more of the radiopaque dental markers, and instruments 
for sculpting and drilling the markers, for example, an acrylic cutting 
burr and/or dental drill bits. 
The foregoing may be better understood in connection with the following 
examples: 
EXAMPLE 1 
Fabrication of Markers 
Tooth-shaped radiopaque markers 10, as shown in FIG. 1, may be fabricated 
by making models of various teeth, such as, for example, centrals, 
laterals, cuspids, premolars and molars, both maxillary and mandibular. As 
can be seen in FIG. 1, the models of teeth may be designed so that, after 
a mold is constructed from the model and the marker is cast, the marker 
has a crown portion 12 (the portion of the tooth that is seen visually in 
the oral cavity) as well as an elongation of the root portion 14 of the 
tooth. A technician, dentist, or oral surgeon can modify the marker 10 to 
fit precisely to a space in the oral cavity, where teeth have been lost 
and implants are indicated, and to properly occlude with the opposite 
tooth 22, as shown in FIGS. 2 and 3. Once the desired shape of the model 
tooth is achieved, a mold is made from a flexible material (for example, 
polyvinyl siloxane). A radiopaque material, in this example diatrizoate 
sodium (HYPAQUE.TM., Winthrop Pharmaceuticals), and binder were mixed, as 
described in Table 1, and poured into the polyvinyl siloxane mold, and 
allowed to cure. Curing can take place at room 10 temperature, or at 
elevated temperature and pressure. The marker 10 is then extracted from 
the mold for use in fabrication of a stent 18, as shown in FIG. 3. 
TABLE 1 
______________________________________ 
Amount of Binder* 
Amount of HYPAQUE .TM. 
Radiopacity 
______________________________________ 
5 ml 0.5 gm slight 
5 ml 1 gm optimal 
5 ml 2 gm optimal 
5 ml 3 gm optimal 
5 ml 3.5 gm very 
opaque** 
______________________________________ 
*Urethane, acrylic or epoxy. 
**Quite thick. 
EXAMPLE 2 
Fabrication of a Stent 
An impression is taken of a patient's maxilla and/or mandibular arch. As 
shown in FIG. 3, a stone model 16 is made from this impression. A 
radiopaque stent 18 is then fabricated on this stone model 16. For 
purposes of this example a single marker 10 is selected from an assortment 
based on the tooth to be replaced. The marker 10 is modified or shaped 
with an acrylic cutting burr to fit in the designated area. As shown in 
FIGS. 3 and 7, it is important that the marker 10 fit precisely to the 
edentulous ridge 20 and be in proper occlusion with the opposing tooth 22. 
The marker 10 should replicate the optimum position of the final 
prosthesis with cosmetic and functional concerns foremost in mind. 
Alternatively, the marker may take the form of balls or spheres of 
appropriate size (for example, 2-5 mm diameter) (not shown), in which case 
the sphere should make point-to-point contact with the gingival surface 20 
at a point approximately midway between the adjacent teeth 26. 
It is necessary for the marker 10 to be suspended in this position during 
the course of radiographs and surgery. A stabilizing strut 24, as shown in 
FIGS. 4 and 5, is fabricated over the marker 10 and the adjacent teeth 26. 
This secures the marker 10 in a fixed position, as shown in FIGS. 6 and 7. 
This enables one to transfer the stent 18 from the stone working model 16 
to the patient's mouth with utmost accuracy. The stabilizing strut 24 is 
made from nonradiopaque materials, for example, methylmethacrylate or 
bis-GMA (light cure resin). The stent 18 is initially used to provide a 
reference point, visible on radiographs, to evaluate the amount and 
position of the underlying bone 28 and the position of the underlying 
nerve 30. As shown in FIGS. 6 and 7, the stent 18 is placed in the 
patient's mouth, and pertinent radiographs are made. The radiopaque 
markers 10 are visible on the radiographs, and measurements are made from 
the radiographs to determine maximal length of implant, and the implant 
angulation and position. 
After using the stent 18 to determine ideal implant length, position and 
angulation from the radiographs, the stent 18 can be modified in several 
ways to act as a guide in helping the surgeon accurately place the 
implant. For example, as shown in FIGS. 8-10, a hole 32 can be drilled 
through the tooth-shaped marker 10 at the appropriate angle and in the 
optimal position on the tooth-shaped marker 10 to guide the oral surgeon's 
drill to allow for alignment of the implant with the roots of the adjacent 
teeth 26, and to allow for placement of the implant in the area of maximum 
bone density. This radiopaque tooth-shaped marker 10 included in the stent 
18 eliminates duplication of effort, since one stent can be used both for 
radiographic marking and for surgical guidance during implant placement. 
While the preferred embodiment of the invention has been illustrated and 
described, it will be appreciated that various changes can be made therein 
without departing from the spirit and scope of the invention.