Here’s a little walk-through that will teach you some troubleshooting procedures, and a bit about one type of 3-way syringe. Several issues can come about when a syringe fails, usually the most pressing problems being water leaks.
Warning: Please, please, PLEASE practice caution when working on your syringes, or any dental equipment for that matter. Syringe buttons/valves have quite a bit of both air and water pressure behind them, and once the locking mechanism is disabled, they can and will fly out at you which could cause injury! Turn off the dental unit and clamp off the syringe hose before attempting any work.
WARNING: Turn the delivery unit to the OFF position AND clamp off the syringe hose!!
How to tell if you have a pin-less type of syringe? Take a look at the captioned picture below:
The left syringe has no locking pin going through the head, while the right syringe does.
(Pin-type syringes will be covered in a later tutorial.)
In a pin-less style syringe, the button/valve is actually in two pieces. If you are noticing that the buttons are sticking, there is water leaking from the tip constantly, or if water is coming out around the button, it’s time to replace the buttons/valves.
First, remove the buttons by pulling up on them while wiggling slightly. Depending on how corroded the buttons are, it could be a challenge to take them out.
Pin-less syringe buttons pull straight out.
Second, you’re going to have to get a special tool to remove the second piece of the valve. It’s called a valve core tool, and it can be purchased at most tire/auto-parts/bike stores.
The valve core tool looks a little something like this.
Gently insert the valve core tool into the syringe and carefully twist with a counter-clockwise direction, as if you were taking out a screw.
Once the valve is unscrewed, sometimes you still need to use a pair of hemostates or the like to remove the valve core.
This is what you should pull out:
Something to note, treat the two parts of the valve as one device, meaning that if you change one, you change the other. Corrosion can and will transfer from an old valve core to a new button, and visa versa, so it doesn’t pay to cut corners.
Treat these two pieces as one. Keep both in stock.
During our repair courses that I help teach at the CDA So-Cal meetings, I’m always asked, “So, all we have to change are the o-rings on these pieces, right?” That’s where I smile politely and remind them that the whole point to doing your own repairs is to be cost efficient. If you’re really bored, you can take one of these old buttons and valve cores apart and really see that these parts are more complicated than they look. If you were to find rubber replacements for them, you’re still looking at a looooooong repair time, which cuts into your schedule, which is better spent on your patients. The combined cost of a valve and button is less than $15, and these pieces can be changed in about a minute. Do yourself a favor (and save yourself the aggravation) by just using replacement valves and buttons.
To replace the valve cores and buttons, reverse the steps you used to take the old ones out. Note: use silicone based lube, a very light coat, on the pieces you change. Don’t use petroleum jelly (Vaseline) on your dental equipment for lubrication. Petroleum jelly will destroy the o-ring material.
You don't need much lube when prepping your new buttons and valves. Rub some between your fingers and handle the parts until they have a shiny coat.
If you are noticing that water is leaking around where the syringe tip is inserted into the syringe head, or if when going back and forth between air and water you get mixture, there are o-rings that have to be changed. Depending one what type of nose cone your syringe has, either by hand, or with the use of the proper sized Allen wrench, remove the nose cone and brass insert. There will be either one (for the cones you have to tighten down by hand to lock a syringe tip in) or two (non-twist nose cone) o-rings in the cone. Replace what you remove.
*"Twist type"* nose cone that is tightened by hand.
Removing the brass insert.
When going back and forth between air and water, and you’re getting spurts of water when you switch, you have to change the tip adapter o-ring. In the case of most of the pin-less types of syringes, it’s usually below the brass insert.
Tiny tip adapter o-ring under the brass insert.
If you’re using disposable tips with a metal insert, you’ll notice when you change this tip adapter o-ring that it may be pretty shredded up. I personally suggest using autoclaveable syringe tips, due to the fact they don’t damage o-rings and are generally a better fit, or fully plastic tips without metal inserts.
As with the buttons and valves, when changing the o-rings in the tip adapter and nose cone areas, be sure to handle your parts with a light and shiney coat of silicone lube.
That’s all for now! Coming up, I’ll be going over pin-retention type syringes, more specifically the most common syringe out there: the DCI quick connect 3430.