Background: Smoking is a risk factor for dental implants. The mechanisms behind the impact of smoking on osseointegration are not fully understood.

Purpose: To investigate the initial molecular and clinical course of osseointegration of different titanium implants in smokers and nonsmokers.

Materials and Methods: Smoker (n = 16) and nonsmoker (n = 16) patients were included. Each patient received three implant types: machined, oxidized and laser-modified surfaces. After 1, 7, 14, and 28 days, the peri-implant crevicular fluid (PICF) was sampled for gene expression analysis of selected factors involved in early processes of osseointegration. Furthermore, pain-score (VAS), resonance frequency analysis (RFA) and baseline clinical assessments were performed.

Results: Early failure of osseointegration, associated with a high and sustained perception of pain, was encountered in 3/32 patients. In general, high pain scores were reported during the first days after implantation, irrespective to smoking habit, which correlated to high levels of pro-inflammatory cytokines during the first days after implantation. Higher ISQ values were found in smokers compared to nonsmokers. In smokers exclusively, ISQ values correlated to harder and less atrophic bone quality and quantity, respectively. Smokers displayed a higher expression of osteocalcin (OC), but later peak and lower expression of bone morphogenetic protein (BMP-2) (at 7 days) compared to nonsmokers. In comparison to machined implants, surface-modified implants were associated with higher expression of alkaline phosphatase (ALP) and cathepsin K (CatK) at 28 days in nonsmokers.

Conclusions: During the early phase of osseointegration, postoperative pain is linked to the inflammatory cell response and, may tentatively serve as an indicator of biological complication and implant loss. The present study suggests that smokers have an altered bone composition and (ultra)structure based on the observations that ISQ values are higher and correlate to recipient bone quality and quantity in smokers.