What Are the Types of Tubing Connections?

2 Hole (Borden Connection)

• Usually the standard in developing countries (e.g., all of Latin America).
• Has one large hole, which is air intake to drive the turbine to spin, and a small hole for water to cool the bur/tooth.
• No air exhaust, so the exhaust just blows right out of the handpiece, making it much louder.
• Also, no chip air, so the water comes out more as a stream than as a fine mist.
• A 2/4 adapter can be used to fit this kind of handpiece onto 4 hole tubing, but the handpiece will still not have the chip air or exhaust air features.

3 Hole

• Used very little. In fact, we may be one of the last manufacturers still to offer this style!
• Has the same handpiece thread design as 2 hole, but with the addition of one extra small tube for the chip air line to allow the water to come out as a fine mist.
• Can be converted to 2 hole by simply removing the chip air tube.

4 Hole (Midwest Connection)

• The standard in the U.S. and Europe.
• Has two large air holes (the smaller of the two is air in and the larger is air exhaust out).
• Also has two small holes, a water tube and a chip air tube (which brings air to the head where it either mixes with or hits the water to make a fine mist) to cool the bur/tooth and clear debris.
• A 4/2 adapter can be used to fit this kind of handpiece onto 2 hole tubing, but the handpiece will lose the exhaust and chip air feature.
  

5 Hole

• Has the same handpiece thread design as 4 hole, but with the addition of a fiber optic rod which transmits light through the handpiece and illuminates the bur and tooth area for better visibility.
• Has all the other features of 4 hole as well.
• A 5 hole handpiece can be used on 4 hole tubing, but the light feature will not function.

Quick Disconnect Coupler Connections

• Couplers can be 2 hole, 4 hole, and fiber optic (2 types).
• 5 hole fiber optic couplers have an internal glass rod that goes onto tubing that has a light source (bulb) either in the tubing or on the dental control unit.
• 6 pin couplers (with 4 holes like a normal 4 hole handpiece plus 2 metal pins to provide electricity) have the light bulb in the coupler itself.

References

Article excerpts from：

https://johnsonpromident.com/handpiece-tubing-compatibility#:~:text=2%20Hole%20(Borden%20Connection)&text=Has%20one%20large%20hole%2C%20which,than%20as%20a%20fine%20mist.