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I read on some articles saying that two-piece (kind of nut-and-bolt system) dental implants might have gap as time goes, because a man chews foods everyday.

Some bad bacteria (anaerobic bacteria such as Porphyromonas gingivalis) may live in the gap, as I read from a dentist's article.

However, most famous dental implants are still two-piece system, although I found that many small manufacturers produce one-piece system.

What are the advantages and disadvantages of one-piece system? Are there any guidelines for helping patients decide between one-piece and two-piece implants?

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  • Good edit, @Lucky. I retracted my close vote.
    – Carey Gregory ♦
    Mar 15, 2016 at 14:37
  • I would always a teeth bridge. This takes very less time than a dental implant. Most of the times the dentist gives you an option or alternative
    – hellojoe
    Nov 14, 2018 at 9:05
  • There is also a snap system ( like a western shirt) . I have 4 implants each in upper and lower jaws and the dentures snap in and out each day. The snap inserts need to be replaced about once a year. It has worked for 10+ years.
    – blacksmith37
    Jul 2, 2019 at 15:41

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The simplest answer is that both types of systems are more or less equal.

Long answer: It's actually the dentist that needs to be aware of a few concepts:

  1. The angle of the bone in which the implant is placed relative to the position of the crown that will be on top of it. they are not always in line. The ideal scenario is second from left, while the worst one is 3rd from the left. Nobody wants a screw to show up in the front of the crown! To remedy this problem it is possible to use the second stage in a 2-piece system to reangulate the crown. enter image description hereenter image description here

  2. Amount of gingival tissue between the bone and the mouth. If the gingiva isn't very thick, it might be advantageous to remove the intermediate step, so that as little as possible metal shows through the gingiva.

  3. Ability of the bone to endure immediate loading of the implant. If both the implant and the platform come in one piece, the implant will be exposed to forces in the mouth immediately after being placed, while the two piece option permits us to temporarily bury and avoid putting immediate stress on the implant, thereby enabling it to better integrate the bone, especially if the later is of poor quality.

  4. To address your concern about a micro crack appearing between the two pieces, it is most often due to the insufficient tightening of the screw. At least 15-25 Newtons need to be applied, using an implant screw, to sufficiently tighten the the pieces to avoid the appearance of a micro crack and further of the screw.

My source, excluding professional formation:

http://www.oralhealthgroup.com/features/the-one-piece-implant-design-prospective-case-report/
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Today, there is a trend to go for two-piece restoration. One pice (base) is placed on the day of surgery on the implant and remains there. the second piece (abutment with crown, or one-piece implant-crow) comes o top.

The recent scientific evidence shows that keeping the biological barrier around the implant and base intact. This limits the chances to see bacteria migrating along with the prosthesis towards the implant - often cause of mucositis/peri-implantitis. See an illustration here: https://www.teeth4all.org/getting-treated-with-dental-implants/complications-with-implants/

With regards to the crown, a one-piece solution where the abutment and crown are 'merged' together present better longevity and less need of repairs (due to porcelain chipping). This option is esthetic enough for prosthesis not too visible when smiling (i.e. posterior region).

For the anterior region, visible when smiling, two-pieces solution offers the flexibility to the dental technician to produce highly esthetic prosthesis. In the anterior region, as the chewing forces are lower, the problem of chipping is less frequent.

See an illustration here: https://www.teeth4all.org/all-about-dental-implants/dental-prosthesis/#Prosthesis-type

Overall the one-piece solution is cheaper than the two-piece one, but the level of aesthetics might be lower while its strength is higher.

The explanation above was for the restorative part. For the implant part, the trend is to use the two-piece part. The rationale is the following:

Having an implant at the bone level and the restoration screwed on top, through the gingiva offers flexibility. Always consider the future development of the patient condition: if there is some gingiva recession, then the restoration can then be swapped for a shorter one and the implant will not show up. New implants/prostheses might be added and, and, being bone level offers more flexibility if the prosthesis must be changed (insertion angle, implant height,...).

With regards to the trans-gingival implant (tissue level implant) thew offer through the assurance that the peri-implant soft tissue will never be disturbed, and thus, the biological seal around the implant limits the risk of bacteria navigating along with the implant towards the bone (cause of mucositis and peri-implantations). this is tough dependent on many other factors as well (implant surface, patient hygiene,...).

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