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February 27, 2014
Air water syringe tips are one of the most common products dentists and hygienists use in dental offices. So let's get to know more about the differences between syringe tips and which ones will work best for your practice.
The basic design of the standard air water syringe tip has remained unchanged for decades. The air water syringe has two concentric passageways, one for air (usually the outer passage) and one for water (usually the inner passage).
The central tube (see image below) is for water. On most standard tips, this tube is longer and projects out the back of the tip. This design allows the water tube to penetrate a small o-ring (#01-06) inside the syringe head to help keep the air and water separate.
On many disposable tips, the inner water passage is the same length as the rest of the tip; this means that these tips will require a special adaptor to help keep the air and water separate. If used without an adaptor, they are much more prone to cross-over (See Tech Tips #50 & Tech Tips #51). This is one reason that autoclavable tips will usually deliver superior performance.
On most syringe tips, air moves through the outer passage of the tip coming out at the end. Sometimes the air is expelled through a simple gap but sometimes several holes are used (this aspect of the design can vary widely). Most metallic tips will have a series of holes regularly spaced at the end of the tip to allow expulsion of air (see image below). The regular and consistent spacing of these holes provides a consistent spray pattern (when spraying both air and water mist). As a cost saving measure, many disposable tips simply use the natural “gap” between the inner water line and outer air line of the tip to allow air to escape out the end. Relying on this gap provides inconsistent spacing and an irregular and inconsistent spray pattern.
As mentioned, syringe tips at their most basic are simply an assembly of two concentric tubes. These are round. They go into a round passage in the air water syringe and are normally secured with o-rings. This means you’ve got a round tube in a round hole. It will spin. Many practitioners like to use the syringe tip for retraction and will push on the cheek with the syringe tip. If pushing with the tip, rotation is not desired. Most syringes are designed for quick changing of tips (as the tip should be changed after each patient) which does not normally allow for a mechanism to reduce the ability to spin if pushed on. The DCI rotation lock tips (#01-97) are an exception to this.
The rotation lock tips have a series of “dimples” (see image below) around the perimeter of the tip which will lock in with the ball bearings of the DCI syringe holding mechanism (“collar”) making it harder for these tips to spin. These tips will only work in a DCI syringe (#01-01Q or #01-85) which has 6 ball bearings in the collar to secure the tips. The ball bearings are retracted to change tips, so using a design that incorporates the ball bearings does not preclude quickly changing tips either.
With most other syringes, two o-rings (#01-04) are used to hold the tips in place. On some of these, one o-ring may be replaced with a cone (#01-21 or #01-23). Along the length of the cone is a slit (see image below). This slit provides lateral tension making it harder to spin the tip. Some syringes can be adapted to use a cone instead of an o-ring if you wish to minimize tip spin. Normally, use of a cone will make it more difficult to change tips, but it shouldn’t prevent quickly changing tips. Consult with our staff and we will help you determine if you can incorporate a cone in your syringe.
As you can see, many aspects of the tip design affect syringe performance. Keep your needs and uses in mind when purchasing tips and syringes.
October 30, 2012
Last month in Tech Tips we discussed a few possible sources of cross over and how to determine if you actually have cross over. We finished up by looking at master valves.
What if you’ve got cross over in more than one room? Is it possible that one room is affecting the others? Yes, cross over can work through the lines from one room to the entire office. In fact, you can even get air in your pipes (if you’ve got air in the water line) so pipes will rattle, squeak, or groan when any source of water is used (such as a faucet or even a toilet). Of course, you can also get failed valves in multiple rooms at once.
How do you determine which room is to blame, or even tell if it’s one or more?
Since we left off last month in the junction box, let’s continue there.
In addition to your master valves, you should also have manual shut offs in your junction box. Normally, the master valves are attached directly to the manual shut-offs. The manual shut-offs have a knob that you can turn to physically stop the flow of air and water. Use them to shut both air and water off in an affected room. Start in the room closest to the compressor.
Once the manual shut-offs are closed, depress the buttons on your air/water syringe until all flow ceases. Next turn the AIR manual valve back on, but LEAVE THE WATER OFF. Put your syringe tip into a cup of water and hit the WATER button of the syringe. If you have bubbles, you have cross over in that room. If you had been experiencing water in the air line, you’ll want to hold the syringe button down for at least one full minute as it may take some time for the air to work its way through the lines. If you don’t have bubbles, that room is probably fine. Turn both air and water off with the manual shut-offs and proceed to the next room and repeat this test. It’s important that you turn both valves off before checking the next room to keep any cross-over that might be occurring in this room from affecting others.
Where else can you get cross over? Any other air-activated water valve in the unit.
If you have cuspidors with timers for the bowl rinse or cup filler functions, the timers are air activated and could be a source of cross over. As cuspidors typically have large lines attached, these can affect the whole office more readily. If you’ve got squeaking pipes, your cuspidor may be a more likely culprit.
Just like master valves, timer valves can vary in design but will be mounted inside some sort of “box” or “utility center” directly below the cuspidor. The timers often have a similar appearance to master valves and will have some sort of knob to adjust the timing.
Other possible sources of cross over are the water relay valve or even the handpiece block.
Normally, a failure in the water relay valve will result in trouble with handpiece water long before you experience cross over, so this is not very likely unless you’ve also had trouble with your handpiece water coolant (dripping, coming out of the wrong handpiece, or other issues). Depending on the design of valve, usually the water relay just needs to be replaced as most are not readily serviceable.
Last of all is the handpiece block. There are many designs of block, so this can be more difficult to check, but often a diaphragm will be readily apparent when you inspect the block (such as in the block pictured below, as used in a Beaverstate delivery system). You can clearly see the seam between the two layers of brass in the photo. This is where the diaphragm is.
In many models of units, water does not actually enter the handpiece block, so you would not get cross over here. Always be sure to verify the configuration of your unit before checking the block.
If you have quick disconnect handpieces, you can also get cross over in the coupler. Normally cross over here would only be seen in the handpieces. In this case, you may see water dripping out of the unit. This is actually from water coming out the exhaust line (which often empties into the unit). If you see water dripping out of the unit (or it’s getting into your turbines) change the o’rings on your quick disconnect.
As you can see, there are a number of possible sources of cross-over in the dental office. To help you diagnose, we’ve provided a handy checklist below:
Possible Sources of Cross-over
As mentioned above, check one room at a time to verify where cross-over is occurring then check the valves within each room to determine the precise source.
September 25, 2012
What is cross-over? What causes it, and how do you fix it?
And no, we don’t mean a 4 wheel drive vehicle that combines the features of a sedan, wagon, and SUV.
As we discussed way back in Tech Tips #3 Dental Pneumatics, most dental units run on air and require air for just about everything, including turning on the water (which is “air activated”). This means there are valves inside the unit which have both air and water flowing to (and possibly through) them. A failure in one of these valves can lead to cross-over, getting the air in the water line or water in the air line.
The first step is to verify that cross-over is actually occurring. If you have water in the air line, start by checking at the compressor. Do you have good dry air coming out of the compressor? If the air is moist right at the compressor, the problem is at the compressor itself and you don’t have cross-over. Check the filters, dryer, and drain the tank. If the problem persists, additional trouble-shooting of your compressor may be required, call and speak with one of our technicians.
If the air is dry at the compressor, then you probably have cross-over, so now you need to figure out where it’s happening.
Are you experiencing cross-over in just one room or several? If it’s in just one room, that will narrow things down considerably; if it’s in more than one, you could have multiple failures, or you could have water or air working its way through the lines from one room to the others. Either way, we’ll next want to check within one room that’s affected.
Are you getting cross-over in the air/water syringe? The syringe air and water doesn’t typically go through many valves, so if you’ve got cross-over here, it’s likely from a failure within the syringe itself, or in the master valves (see Tech Tips #23 ”Getting to Know Your Utility Center”).
If cross over is occurring in the syringe itself, the cross-over could be isolated to the syringe. Check for cross-over elsewhere. Do you have trouble with the handpiece drive air? If you've got water in the drive air, youll often notice that water drips out the bottom of the unit when you use your handpiece (as the drive air typically exhausts into the unit). Do you have an assistants side syringe as well? Is it affected? If you dont have cross-over anywhere but in one syringe, then the cross-over is quite possibly within that syringe.
If it’s just one syringe, the most likely culprit is the small internal o’ring, our part #01-06. If this o’ring is missing or damaged, you can get cross-over in your syringe.
If the water just fails to shut off, you’ve probably got a worn button or valve core. Check our previous issues on syringe repair and syringe troubleshooting for more information on resolving these issues.
Another possible point of cross-over in the syringe is unique to certain brands of autoclavable syringe (such as A-dec). With these syringes, a manifold is inside the handle and the syringe head attaches to this manifold and is secured in place when the handle is threaded on. The manifold has two male connectors that are off-center and which correspond to two holes on the bottom of the syringe. One port is for air, the other for water. These ports are off-center so they will only connect to the syringe if properly aligned. In theory, this will prevent cross-over, however in reality it can cause it. If the ports are not properly aligned, the handle can still screw onto the head of the syringe, but the air and water will just flow into the cavity between the manifold and the syringe head. This creates a constant mix in the syringe handle which will yield cross over in the syringe. Ironically, even though this occurs at the syringe, this particular source can lead to air or water flowing back down the lines and yielding cross over in other items in the operatory as well. If you are getting cross over and have autoclavable syringes, always make certain that the syringe head is securely attached to the manifold before proceeding with other checks (if for no other reason, this is a very quick and simple thing to check).
This photo shows an A-dec syringe handle with the manifold.
If the syringe checks out, then we need to check other possible sources of cross over.
Every air activated valve in the unit is a potential source of cross-over, and all of them should be checked.
As mentioned previously, if you’re getting cross-over in the syringe, you could also have a failure in your master valve. The master valve is one of the most common sources of cross-over we encounter. There is a diaphragm on the master valves that corresponds to the air activation. Usually the diaphragm is under a square cover on the valve. This will also be where an air line attaches to the valve.
A few common designs of master valve are shown below with the location of the diaphragm pointed out:
Note the square covers held on with screws at the corners in the second and third photos. This type of design is very common on master valves. Look for a square cover on your master to find the diaphragm.
The third photo is of an A-dec water master. Note the yellow tubing with a red dash. This is the A-dec color-code for an air activation line (air out from the master switch on the front of the unit). The diaphragm will usually be near where this line attaches (another thing to look for to correctly identify where your diaphragm is). American Dental Accessories, Inc. carries master valve repair kits which will allow you to replace the diaphragm. In addition, the repair kits include o’rings, valve stems and springs. We recommend replacing all of these components if you’re accessing the valve interior. You can also see a manual shut-off in the third photo. The master valve normally attaches directly to the manual shut-off. You will want to use the manual shut-offs to turn the air and water off at the unit before servicing the master valve(s).
It is also common to have a relief hole in the side of the master valve just above the diaphragm. If water is coming out of this hole, this is another indication of a ruptured diaphragm.
A worn or damaged diaphragm in the water master can also lead to getting air in your water line.
Stay tuned for Part 2 next month. Well cover more valves that could be the source of cross-over, details on how to narrow down which operatory might be the source of cross-over, and the effects of air in the water line. All of this and more, next month!