Practice Tips 36: Handpiece Couplers- The ABC's of ISO

In most cases, handpiece tubing couplers are standardized thanks to the International Organization for Standardization or ISO. ISO is a non-governmental body with international representatives who disseminate medical/dental, industrial and commercial standards worldwide. ISO has established specific standards for dental handpiece couplers.

There are three main types of couplers recognized by ISO in use today:


Also known as a “Borden” coupler. These couplers have 2 or 3 holes and do not include an exhaust port. ISO-A couplers are used most extensively in Europe and Latin America.


Commonly known as a “Midwest” coupler. These couplers have 2, 4 or 5 holes and include an exhaust port. The largest port in this coupler is the exhaust. The 5th hole usually accommodates a light bulb for an illumination system or glass tube for a fiberoptic system. You will notice the 4-hole coupler even includes a “dimple” in the place of the 5th hole to comply with ISO standards (although the dimple is not drilled through). This allows use of a fiber optic handpiece on a 4 hole coupler. ISO-B couplers are used most commonly in the US.

Handpiece Connector Gasket


Also known as “new style” 6-pin coupler. Due to standards set forth by ISO, these couplers are configured like the ISO-B or “Midwest” couplers. The two additional holes are there to accommodate the pins on a 6-pin handpiece or lamp module and are set in the same position the 5th hole would normally be on an ISO-B coupler. In fact, a 2-hole or 4-hole ISO-B handpiece could actually be attached to an ISO-C coupler.

The ISO-C coupler is the most recent standard for handpiece couplers and had not been adopted until several manufacturers produced 6-pin systems of their own. Most of the newest systems now comply with this recent ISO-C standard. However, there are still older systems or systems that have been around since before this coupler was standardized. These systems do not have an ISO-type coupler.

The various ISO configurations are pictured below:

PHOTO: Note that all of these couplers incorporate threads. There is a “nut” at the end of the hose that screws on to the threaded portion at the back of the handpiece.

With ISO-C couplers, there are two types of nut that can be used. The standard, or “short” nut is used on ISO-C couplers that are intended to be used with a 6 pin handpiece or quick disconnect (such as pictured below). Some ISO-C systems use a long nut (about 1 ½” longer than a standard connector nut) as these are designed to be used with a lamp module. The longer nut allows room for the lamp module between the hose and handpiece. The lamp module will have a 5 hole (ISO-B) end to accept a standard ISO-B handpiece. So, while the tubing will be an ISO-C 6 pin, you will still use an ISO-B handpiece with it.

Handpiece Couplers

Many handpieces now incorporate swivel and/or quick disconnect couplers. These couplers are not standardized and can vary widely. Most manufacturers have their own uniquely designed swivel which will not be compatible with other brands. This means that if you have a swivel disconnect handpiece, all other handpieces used on the same unit must be the same brand. No other brand would use the same style swivel connector. The only exception are some aftermarket systems designed to be compatible with some of the “brand name” QD systems (see below).

In recent years, the Kavo swivel has become popular with many other manufacturers. They now offer this style of swivel quick disconnect (Q/D) for their handpieces as well. A fiber optic (Lux-style) Kavo coupler is pictured below.


In the photo above, this coupler has 5 o-rings on the shaft (3 large black o-rings and 2 small white ones). The number of o-rings help to differentiate this coupler from other designs.

Most other couplers will only have 2 or 3 o-rings. Be certain to pay attention to the o-rings on your coupler. The o-rings should be lubricated regularly with a silicone based lubricant to extend their life. Typically, replace the o-rings every 6 months (depending on usage). Worn o-rings result in such issues as leakage of air or water at the coupler, difficulty in swivelling the handpiece, poor performance of the handpiece (inhibited drive air flow), or poor or erratic water spray.

Fiber Optics

The coupler above incorporates a bulb at the end to provide illumination. This coupler will attach to a 6 pin ISO-C hose. If you look carefully, you can see 6 pins (or, more accurately, 4 tubes and 2 pins) at the bottom.

Kavo swivels are made in 5 hole and 4 hole configurations as well. The 5 hole coupler looks very similar to the 6 hole, but instead of a bulb, there is just a bundle of glass to allow light to pass through from your lighted hose. Pictured below are 5 hole and 4 hole swivel quick disconnect couplers of the Kavo design:

Just as you should lubricate the o-rings, you should also take care to clean the fiber optic port on 5 hole couplers on a regular basis. A cotton swab moistened with isopropyl alcohol will usually work well.

Whenever purchasing a handpiece, replacing the hose or fiber optic system, just remember your ABC’s and you’ll maintain compatibility every time.


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