Influence of Apico-Coronal Implant Placement on Post-Surgical Crestal Bone Loss in Humans

Contradictory results exist regarding influence of apico-coronal implant placement on crestal bone levels.

Complete charts of patients ≥18 years old with one or more dental implants were included. Demographic, medical, surgical, and prosthetic information was recorded. Implant bone levels were evaluated at initial placement, implant uncovery, prosthetic delivery, and 3 to 6, 7 to 11, and 12 to 18 months post-implant placement.

Charts of 55 patients and 134 implants were included. At baseline, 19.5%, 67.3%, and 13.3% of implants were recorded as equicrestal, subcrestal, and supracrestal, respectively, on their mesial aspect, and 32.1%, 50.0%, and 17.9% on their distal aspect, respectively. At time of prosthetic delivery, mesial aspect implant position was equicrestal in 35.4%, subcrestal in 17.7%, and supracrestal in 46.9% of cases, whereas on their distal aspects, the same categorical positions were found in 28.4%, 21.1%, and 50.5% of implants. For the mesial aspect of the implant, 3- to 6-, 7- to 11-, and 12- to 18-month intervals, and for the distal aspect of the implant, 7- to 11- and 12- to 18-month intervals, along with diabetes (for both mesial and distal), were associated with a statistically more apical position of the bone compared with baseline. Although the odds ratio of a subcrestal implant position at follow-up times was statistically greater for implants located subcrestally at surgery, linear measures of differential crestal bone loss (CBL) as a function of the categorical initial placement of the implant (supracrestal, equicrestal, subcrestal) at 3- to 6-, 7- to 11-, and 12- to 18-month time points generally showed no significant differences among groups.

A subcrestal position of the implant at time of surgery leads to reduced odds of having implant threads exposed; however, it is associated with similar linear CBL compared with an equicrestal or supracrestal surgical position.