A retrospective evaluation of the effect of hypothyroidism treatments on dental implant osseointegration success

ABSTRACT Objective: The aim of this retrospective cohort study was to evaluate the osseointegration success of dental implants in individuals diagnosed with hypothyroidism and to investigate the effect of levothyroxine (LT4) replacement therapy on this process. Materials and Methods: Medical and dental records of patients who underwent implant treatment in the mandibular posterior region between 2014 and 2024 were retrospectively reviewed. Participants were divided into three groups: individuals with hypothyroidism receiving LT4 replacement therapy (HT+LT4), individuals with hypothyroidism without LT4 treatment (HT–LT4), and systemically healthy individuals (control group, CG). Early implant success was evaluated, and the obtained data were statistically compared among the groups. In addition, the peri-implant trabecular bone microarchitecture was assessed using the fractal analysis (FA) method. FA was performed in six regions of interest (ROIs) around each implant, and fractal dimension (FD) values were calculated using the box-counting method. The mean FD values were statistically analyzed and compared among the groups. Results: A total of 125 patients (472 implants) were included in the study. The failure rate in the HT–LT4 group (23.1%) was significantly higher than in the HT+LT4 (3.6%) and control (5.4%) groups (p=0.032). Implant-level analysis also revealed a significant difference among the groups (p<0.001), with failure rates of 14.6% in the HT–LT4 group and 1.4% in both the HT+LT4 and control groups. Due to insufficient sample size (n=2), the HT–LT4 group was excluded from FA analysis. Immediate postoperative FD values were higher than those obtained before prosthetic loading (p<0.01). Although the decrease in FD values was greater in healthy individuals than in the HT+LT4 group, the difference was not statistically significant (p=0.072). Conclusions:The early failure rate of dental implants in hypothyroid individuals who did not receive LT4 replacement therapy was significantly higher compared to the other two groups. In contrast, the early implant success rate in hypothyroid individuals receiving LT4 replacement therapy was comparable to that of healthy individuals. Fractal analysis findings suggested that, although early implant failure was not observed, trabecular bone remodeling in LT4-treated hypothyroid individuals may proceed slightly more slowly than in healthy individuals. Keywords: Hypothyroidism, Levothyroxine, Dental implant, Osseointegration, Fractal analysis