Milton, WI...July 12, 1994
On the 18th anniversary of the first Automated Endo course, Dr.
Dana Lubet, stimulated me to unearth an idea that had been buried in the far reaches of my mind for several years.
Being a typical dentist, he wasn't happy with nebulous answers to one of his questions as to how to deliver precise amounts of cement to the apex with the Precision Endo Syringe.
One of the chief attributes of the Precision Endo Syringe as opposed to some of the others on the market is that the inside diameter is smaller.
This may seem like a small difference but when you consider that if you cut the diameter of a syringe in half, you divide the cross sectional area by a four.
This has two effects.
First, it takes less axial load on the plunger to deliver cement, and the flow rate per unit of linear movement is cut.
So if you make a syringe smaller it gets easier to control.
The name of the game in syringe endodontics is CONTROL.
It so happens that 25 gauge stainless steel tubing has a bore ( inside diameter ) almost exactly the same as the outside diameter of a 30 gauge needle or of a section of 30 gauge wire, that is 0.014" or one-tenth the inside diameter of the Precision Endo Syringe.
This means that the cross sectional area is 1/100th...very small.
If you were to make a syringe/needle combination out of 25 gauge tubing, and made the plunger out of 30 gauge wire, you would create a quantum leap in control but you have created several problems.
First, the outside diameter of a 25 gauge needle is much larger ( .49mm ) which means that the needle would bind quite far from the apex unless you made the canal much larger than is desirable.
Second, how do you fill the syringe?
I have recently made available through Special Products a new product, now dubbed the Milton Syringe that solves those two problems and makes syringe endo about as precise as anyone could possibly want.
It is now possible not only to decide whether to get a puff of cement at the apex, but how big that puff will be.
Further it has eliminated three mainstays of the current technique, the Mc Combs prep, the Parabolic Funnel prep and the Youngstown Technique.
The answer to the second problem was simplicity itself.
Just fill the 25 gauge needle with a Precision Endo Syringe using a 30 gauge needle.
Stick the 30 gauge needle into the 25 gauge tube and fill it completely.
The solution to the problem of the needle wedging further from the apex requires some explanation.
As good as the Precision Endo Syringe is, it is not controllable enough to allow us to pressure fill, that is wedge the needle and force cement to flow to the apex.
To do that we would have to be able to control flow plus or minus the amount we would be willing to overfill.
Here's the main advantage of the Milton Syringe technique.
If you assume that you can move the 30 gauge plunger in increments of 0.1 mm you can control the amount of cement that you deliver to the apex down to .099 cubic millimeters, that is .0000099 cubic centimeters.
And thus can actually calculate the amount of cement that it will take to fill any length of any size canal.
The volume of cement needed to fill the canal is essentially the volume of a truncated cone.
Since we know the diameter of the top of the cone i.e.
the size to which you prepared the apex, and we know the size of the bottom of the cone i.e.
the diameter of the tube ( exactly .49mm ) and the height of the cone i.e.
the apical length minus the distance from the apex that the tubing wedges, it is a simple mathematical calculation to determine the volume.
The technique goes like this:
Do not use a needle holder here.
That would crush the tube.
Follow across the top to the column designating the size of your apex.
Follow down until the row designating the wedge point of the Milton syringe.
The stroke needed to deliver that exact volume of cement will be at the conjunction of the row and column.
Since the size of the Milton Syringe is the same as a size 50 file, you will be in an area large enough to give you pressure relief and the path of lease resistance for the cement extruding from the 30 gauge needle will be coronal, not apical.
As an example, a size 20 prep with a one per cent taper will allow the Milton Syringe to get 15mm from the apex.
This works out to a plunger movement of 12.5 mm.
This is pushing the limits because the farther you are from the apex, the larger the volume of air that must be expelled through the apex.
What you get with the Milton Syringe is this:
If you misjudge the distance or amount of cement, additions are easy.
E-mail your comments to drjack@BetterEndo.com