Crestal vs Subcrestal: Should we be submerging our immediate implants?
I got a great question about this topic in my previous post and wanted to look at this from a evidence based approach, rather than just give an anecdotal “This-works-for-me” type of response.
On the one hand, if we place immediate implants crestally, we will risk showing exposed threads if there is any bone loss. On the other hand, if we place them too deep, will we we run the risk of causing bone loss around the implant?
What to do?
Let’s start with something that most people agree on. According to a meta-analyses by Kinaia in 2014, placing an implant immediately after extracting a tooth can help preserve the bone level.
It was thought, however, that placing implants subcrestally would cause bone loss.
This suspicion was confirmed with older studies that used polished implant surfaces rather than roughened ones. (See Hammerle Clin Oral Implants Res 1996, 7:111-119)
But then Romanos comes along in 2015 and shows his results with subcrestal placement. It works very well for him and he proposes that subcrestal placement as a general strategy.
He suggests that an implant can be placed subcrestally if they have “platform switching” and have a rough surface that extends over the entire body to the top of the implant in order to encourage bone integration over the implant.
He emphasizes that eliminating the microgap between abutment and implant and minimizing micromovement is important for long term tissue stability.
Here’s the diagram from one of his publications that illustrates the subcrestal placement technique:
Immediate implant placement = good
Subcrestal placement = good.
But we still don’t know how far to sink them.
That’s when I came across a 2018 article by a group of doctors out of Germany. (Elika Madani, et al) This is a really good paper, it answered almost all of my questions.
This is a retrospective study of 159 patients. They looked at implants that were placed in immediate and delayed sites and compared how the depth of placement correlated with bone loss.
In a nutshell, this is what they found:
- Highest estimated loss of crestal bone: implants submerged over 2mm
- Lowest bone loss: crestally placed implants
- Lowest “effective” bone loss: implants placed 1-2mm subcrestally.
This is what they mean by “effective” bone loss:
Say you place an implant at the crest and then you get .8mm bone loss. You’ve got .8mm of implant exposed, right?
Now say you place an implant 1mm subcrestal and you get .8mm bone loss. You’ve still got .2 of bone crestal to your implant platform.
By this example, the crestal implant had more “effective” bone loss.
They recommend a theoretical optimal depth of 1.08mm subcrestal to minimize effective bone loss.
Great, so I’ll just sink all immediate implants 1.08mm, right?
Well, not so fast…
Anterior rules are different than posterior rules.
These factors make people’s bone remodel differently:
- Gingival biotype
- Buccal wall thickness
- Presence of infection
- Delayed wound healing
You might want to sink posterior implants a little deeper to minimize thread exposures with minimal effect on esthetics.
Remember according to Madani, the more you sink the implants, the more bone loss you are likely to get. You can get away with this in the posterior, but not in the anterior.
Mark Bishara (Canadian Implant Dentistry Network) has some good guidelines on immediate molar implants in this article. He bases his suggestions off of classifications of extraction sockets.
As for anterior immediate implant guidelines, there is a LOT to be said. I want to do the topic justice so I’ll leave that for another post. BUT, I will leave you with a few good reads on the subject.
Do yourself a favor and check them out. I’ve uploaded them. (Hopefully I don’t get shut down or something for sharing these.)
Thanks for learning this with me. I’ll see you in another post, my friend.
Interested in learning tips & tricks on basic implant placement? Check out my Online Course. The course is only open 2 times per year, add your name to the waitlist if you want to check it out 🙂
Kinaia BM. Crestal bone level changes around immediately placed implants: a sustematic review and meta-analysis with at least 12 months follow-up after functional loading. 2014.
Romanos GE, Long term results after subcrestaal or crestal placement of delayed loaded implants. 2015.
Madani et al. Impact of different placement depths on crestal bone level of immediate versus delayed placed platform-switched implants. 2018.