What is a one-piece abutment — sometimes called a screw-in abutment or monoblock abutment?

Dentists can use a one-piece abutment to fabricate a single abutment supported crown. These are decisions that a dentist and lab tech must make for implant dentistry. The style of abutment one chooses will influence the types of dental implant problems one can run into in the future. 

There are two basic designs for dental implant abutments

The majority of dental implant crowns today use a ti base system. That is debatable if that is a true abutment. Most crowns that are not using a ti base use a two piece abutment, these include MUAs. A small number of dental implants utilize a one-piece abutment still today. There are also rare uses for 3 piece abutments known as hybrid abutments.

1. A one-piece (screw-in / monoblock) abutment

• The entire abutment threads directly into the implant

• No separate abutment screw — the abutment is the screw

• Torque is applied to the abutment body itself

• Older design, still in use for some systems and narrow implants

2. A two-piece abutment (abutment + screw)

• Abutment seats on the implant

• Separate abutment screw holds it in place

• This is the modern standard (Straumann, Nobel, BioHorizons, etc.)

Why the one-piece abutment fell out of favor

The main reason by far is the first one and for any dentist that has dealt with one unknowingly, they know how difficult things can be. Even if you know it’s a one piece abutment it’s harder to deal with.

• If it loosens → you’re rotating the entire abutment, not just tightening a screw. Since there is a crown on the abutment, that means destroying the crown to get the abutment off.

• Harder to retrieve without damaging soft tissue or provisional

• Worse for precise torque control

• Less flexible prosthetically

Where you still see one-piece dental implant abutments in use.

The most common uses today are when using the implant for retention or for zirconia implants. Systems like locator and ERA are one-piece abutments. Zirconia crowns often will have monoblock abutments as well.

• Some narrow-diameter implants

• Legacy systems

• Certain tissue-level or immediate-load setups

• One-piece implants (implant + abutment combined) — different beast but same idea

Quick abutment terminology cheat sheet

• One-piece abutment = abutment screws directly into implant

• Two-piece abutment = abutment retained by a screw

• One-piece implant = implant and abutment are literally one unit (no interface at all). These would be narrow implants and zirconia only.