Tissue-level implants at 25 years: prosthesis design doesn't drive bone loss — suppuration does

Over two decades of implant function, does the type of prosthetic restoration influence crestal bone loss or peri-implant disease? This was the central question of a single-center observational study that followed patients rehabilitated with tissue-level implants for 25 years, comparing three prosthetic configurations: single crowns (SC), splinted crowns (SP), and bridges (BR).

The study enrolled 147 patients carrying 233 implants, all evaluated with standardized clinical and radiographic protocols at both 10 and 25 years of function. Peri-implant conditions — peri-implant mucositis (PM) and peri-implantitis (PI) — were diagnosed using established consensus definitions. Crestal bone level changes (ΔCBL) were measured radiographically, and multivariate analyses were used to identify implant-, prosthetic-, and patient-related factors independently associated with bone loss.

At 25 years, PI prevalence had increased across all prosthetic groups — reaching 7.8% for SC, 6.3% for SP, and 4.9% for BR — yet no statistically significant differences were found between groups at either time point. PM rates were notably high across the board at 25 years, with SP showing the highest tendency (87.3%), followed by BR (80.5%) and SC (74.4%), though again without statistical significance between groups. Mean ΔCBL was modest and comparable across configurations: -0.37 mm for SC, -0.25 mm for SP, and -0.70 mm for BR, with no significant intergroup difference.

The multivariate analysis shifted attention away from prosthetic variables entirely. Neither prosthetic retention type, marginal misfit, nor emergence geometry showed a significant association with ΔCBL. Instead, three clinical factors emerged as independent predictors of greater bone loss: implant location in the incisor region (-0.74 mm), increased probing depth (-0.16 mm per mm of depth), and suppuration on probing (-0.97 mm).

For the clinician, these findings carry a clear message: when planning implant-supported fixed rehabilitations with tissue-level implants, the choice between a single crown, a splinted unit, or a bridge does not appear to compromise long-term crestal bone stability or drive peri-implant disease over a 25-year horizon. Bone loss is instead driven by anatomical location — the anterior maxilla deserves particular vigilance — and by clinical signs of biological complication, especially deep probing depths and suppuration. These markers should guide the intensity of long-term supportive peri-implant care, regardless of the prosthetic design chosen. The high prevalence of peri-implant mucositis across all groups at 25 years is itself a call to action: sustained plaque control and regular professional monitoring remain non-negotiable over the long term.