When Is a Discrepancy in Crestal Bone Height Level for Adjacent Dental Implants Significant? A Retrospective Study...

To investigate the influence of a discrepancy in crestal bone height between two neighboring implants and how it affects MBL over time.

Medical and dental records and periapical radiographs of individuals with at least two adjacent implants were retrieved and analyzed. Records were divided into two groups according to the prosthetic part: (1) nonsplinted (NS) and (2) splinted (S) groups. Furthermore, groups were categorized by crestal bone height level (CBHL) differences between the two adjacent implant platforms: (1) ≤ 0.75 mm, (2) 0.76 to 1.25 mm, (3) 1.26 to 1.75 mm, and (4) > 1.75 mm. Radiographic measurements were performed at three time points: time of abutment placement (T0), 1 to 3 years of follow-up (T1), and at the last visit (T2). Multilevel linear regression models using generalized estimating equations were used, with a significance level of 5% (α = .05).

A total of 56 patient records with 120 implants (84 NS [70%] and 36 S [30%]) were included. In the NS group, the mean mesial bone loss (T0 measurements subtracted from T2 measurements) of the most posteriorly positioned implant was 2.9, 3.1, 3.4, and 3.9 mm, respectively, across height intervals; the mean distal bone loss of the most anteriorly positioned implant was 3.1, 3.3, 3.4, and 3.9 mm, respectively, across height intervals. In the S group, mean mesial bone loss was 1.1, 2.1, 2.7, and 0.9 mm, respectively, across different height intervals, while the mean distal bone loss was 1.6, 2.1, 1.6, and 1.3 mm, respectively. Results from linear regression showed that NS implants exhibited more marginal bone loss (MBL) progression as the vertical difference between adjacent implants increased (P < .001). The S group showed 1.73 mm less bone loss than the NS group at the mesial side and 1.79 mm more bone loss on the distal side (P < .001) when both had the same CBHL difference (P < .001).

This study suggests that MBL progression depends on the difference in crestal height and is aggravated in NS implants.