Discrepancy in Crestal Bone Height Level for Adjacent Dental Implants, When is it Significant? A Retrospective Study With a Minimum of 1-Year Follow-Up

Purpose: This retrospective study investigated the influence of discrepancy in crestal bone height between neighboring implants. Methods: 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: non-splinted and splinted groups. Furthermore, groups were categorized by crestal bone height differences between the two adjacent implant platforms into < 0.75mm, 0.76-1.25mm,1.26-1.75, an >1.75mm. Radiographic measurements were performed at 3-time points: time of abutment placement (T0), 1-3 years 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=0.05). Results: Fifty-six patient records with 120 implants (84 non-splinted (70%) and 36 splinted (30%)) were included. In the non-splinted group, the mean mesial mean bone loss (T2-T0) of the most posteriorly positioned implant was 2.9 mm, 3.1 mm, 3.4 mm, and 3.9 mm across height intervals. The mean distal bone loss of the most anteriorly positioned implant was 3.1 mm, 3.3 mm, 3.4 mm, and 3.9 mm across height intervals. In the splinted group, mean mesial bone loss was 1.1 mm, 2.1 mm, 2.7 mm, and 0.9 mm along different height intervals, while the mean distal bone loss was 1.6 mm, 2.1 mm, 1.6 mm, and 1.3 mm. Results from linear regression showed that non-splinted implants exhibit greater marginal bone loss progression as the vertical difference between adjacent implants increases (p<0.001). The splinted group showed 1.73 mm less bone loss than the non-splinted group at the mesial sides when both had the same CBHL difference (p<0.001) and 1.79 mm more bone loss on the distal side (p<0.001). Conclusions: This study suggests that marginal bone loss progression depends on the difference in crestal height and is aggravated in non splinted implants.