What is the 3/2 rule for dental implants?

The 3/2 rule for dental implants is a rule of thumb to help positional placement of implants in regards to the surrounding soft tissue.

The 3 stands for placing the shoulder of the implant 3mm below the soft tissue, and the 2mm is for allowing 2mm of facial soft tissue. This idea comes from a 2008 article from the Journal of Restorative Dentistry that states ““The ideal depth of the implant placement is suggested to be 3 mm apical to the planned gingival zenith. The implant/abutment interface should also reside 2 mm palatal to the zenith to ensure adequate thickness of bone and mucosa to support tissue form. “

However in 2025 and beyond I (Calvin Eastwood, DDS) think this is an outdated way of treatment planning these cases and will actually lead to insufficient tissue thickness and prosthetic issues down the line. This relatively shallow placement depth to get 3mm of soft tissue is very shallow and if any recession occurs the implant will show through, resulting in unacceptable results. Shallow placement was necessary with older implant designs that had less ideal connections to prevent bone loss from the leaky connection. However with today’s modern conical implant connection designs, we can place implants much deeper without fearing bone loss, which in turn allows for a better soft tissue emergence and thickness to develop. This falls in line with teachings from Tomas Linkevičius, the highly acclaimed dentist, researcher, and author of Zero Bone Loss principles. The following guidelines will lead to better results:

1. Immediate placement in an extraction site:
   • Implant depth 6mm apical to the gingival free margin
     • This allows for 3+mm of highly polished zirconia on the final restoration for tissue adhesion
   • Implant placed 4+mm palatally from the buccal soft tissue
     • This allows for a more stable base of tissue to increase bloodflow to the tissue overlying the implant
     • More blood flow to overlying tissue means better response to trauma or bacterial insults, allowing for better healing and healthier long term results.
2. Placement in a healed site:
   • Implant depth 4mm below soft tissue
     • In thin (2mm) tissue, this means subcrestal placement of 2mm or more
     • In average (3mm) tissue, this means 1mm+ subcrestal
     • In thick (4mm+) tissue, this means bone level. Typically this thick of tissue is not found in a healed ridge.

In general, with modern implant designs and more recent literature that indicates we should be using highly polished zirconia to gain tissue adhesion, it is critical to place implants deeper than studies from 2008 said we should. Following zero bone loss principles is the best way to predictably place implants and have the tissue look amazing for years to come, even if it does mean changing some of our pre conceived notions about implant placement and depth.