Material and method for introducing ionic silver to dental pulp

A pulp cap mixture is prepared from silver particles and a dental cement such as polycarboxylate cement. Provision is made to apply low intensity direct current through the material placed in proximity to the pulp tissue. Ionic silver is released which provides anti-bacterial action.

BACKGROUND OF THE INVENTION 
This invention concerns the treatment of dental pulp and tissue and more 
particularly is directed to treating pulp infections by electrical means. 
Deep carious lesions present problems to the dentist if the bacteria which 
are always present in the mouth extend deep into the dentin. A worse 
situation exists if the bacterial infection extends through the dentin 
into the pulp. Pulpal tissue has limited blood supply so that systemic 
antibiotics are ineffective. Elimination of bacteria by topical 
antibiotics is also relatively ineffective because the antibiotic cannot 
penetrate deep enough into the tissue to reach all of the bacteria. 
At the present time, calcium hydroxide is the most widely accepted agent 
for capping exposed pulp during treatment of deep caries. It is widely 
used as a liner near or directly in contact with the pulp, covered with 
another restorative material such as zinc oxide - eugenol paste. In most 
cases, the calcium hydroxide appears to promote formation of a secondary 
dentin bridge over the pulp. It is effective in the presence of infection 
if the amount of bacterial invasion is relatively small. However, even in 
cases where the treatment appears to be successful, there is often chronic 
inflamation of the soft tissue. Occasionally the pulp is totally destroyed 
or calcified by the effects of the calcium hydroxide. 
An object of the present invention is to provide bactericidal affects to 
viable pulp (soft tissue) and dentin within a tooth that has become 
infected, thus possibly avoiding need for a root canal treatment which 
destroys the vitality of the tooth. 
PRIOR ART 
Applicants are aware of the following U.S. patents which pertain to 
electric dental treatment. 
Oppenhein in U.S. Pat. No. 2,069,112 teaches, for insertion in a root 
canal, the use of an electric couple fashioned from gold and silver wire 
which may be left in after treatment. No external source is called for. 
Kruse in U.S. Pat. No. 2,121,875 calls for precoating with silver compounds 
a silver bearing anode for insertion into a root canal. Continuous current 
is not called for but in situs reactivation may be required. 
Meiman in U.S. Pat. No. 2,276,623 inserts a wire into a root canal and 
applies 0.5 to 1 milliamperes of negative current for sterilization of the 
area. 
Moore U.S. Pat. No. 2,355,231 treats infected epithelial tissue such as 
pyorrha pockets by applying a positive potential to the area. A conductive 
jelly containing metal salts may be used. The desired result is the 
destruction of tissue. 
Knappwost in U.S. Pat. No. 2,655,922 provides a cathode of silver-palladium 
alloy for the release of OH ions by gavanic action. A different metal is 
used for an anode. 
Summers U.S. Pat. No. 3,019,787 applied ionized floride by means of 0.2 to 
0.7 millamperes of positive direct current. 
Ellis et al. describes in U.S. Pat. No. 3,964,477 a method of sterilizing 
skin tissue by using silver or silver bearing material as the positive 
electrode in a system utilizing low intensity direct current. 
In U.S. Pat. No. 4,027,393 (Ser. No. 614,911, allowed) Ellis et al teach 
the use of a silver post for insertion into a root canal. Low intensity 
direct current releases ionic silver providing antibacterial action. 
The above cited patents are the most relevant known to Applicants at the 
time of filing.

SUMMARY OF THE INVENTION 
A material for dental pulp caps is a mixture of silver particles suspended 
in a dental cement such as polycarboxylate. A mixture of polycarboxylate 
and 65 to 85% silver flakes is preferred. 
The mixture may be used as a dental pulp cap. Direct current in the order 
to 1 to 40 microamperes is caused to flow through the cap releasing ionic 
silver into the surrounding tissue. For electrical contact a silver wire 
may be embedded in the pulp cap which current flows and then clipped 
flush. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Our invention calls for the use of silver particles mixed with a carrier 
for use as a dental pulp cap. With the application of direct current 
electricity, the silver provides antibacterial action for infected dentin 
and viable dental pulp. 
FIG. 1 is schematic representation of a tooth which has been prepared for 
restoration by removing infected dentin leaving a cavity 10a. 
Special dental cap material is prepared by mixing silver particles with a 
suitable carrier such as polycarboxylate dental cement, an example being 
the formulation sold under the trademark "Durelon". 
The silver may be in the form of powder, precipitate, flakes or the like. 
We prefer silver flakes, 0.5 to 1 microns thick and 14 to 17 microns wide, 
as this form produces good results at low concentrations. Approximately 
65% to 85% of the total weight of cap material is preferred, to assure 
conductivity and adhesion. 
The polycarboxylate cement is available as a liquid and a powder to be 
mixed before use. The silver may be added to the powder or added after the 
powder is mixed with the liquid. After mixture, the resulting material 
remains soft and moldable for a few minutes. 
During this time, a thin layer of our pulp cap material 12 is placed in the 
prepared cavity 10a on the pulp chamber 10b if exposed or on the dentin 
near the pulp chamber. The pulp cap material will act as a positive 
electrode and it is best if provision is made for electrical contact. 
Accordingly, as an addition feature of our invention, a piece of silver 
wire 14 is embedded in the material while it is still soft and the 
material is then allowed to harden. After the material has hardened, 
positive direct current is caused to flow through the silver laden pulp 
cap material 12 causing bactericidal silver ions to be released into the 
tissue proximate to the material. Direct current is best supplied by a 
constant current source 16. A return path 18 must be provided from a 
contact on the patient (not shown) to the source so as to complete the 
electrical circuit. Direct current in the range of 1 to 40 microamperes is 
preferred, being applied for approximately ten minutes. 
The silver wire 14 is then clipped flush with the surface of the material 
12 and the dentist proceeds with the restoration of the tooth in his 
normal manner. 
Silver ion activity continues for 3 or 4 hours at a slowly decreasing rate 
and then continues at a very low level indefinitely.