Failure Rate of Palatal Orthodontic Mini-implants: A Retrospective Study

Aim Skeletal anchorage devices have become a widely used tool in orthodontics without requiring patient compliance, notwithstanding, implant failure remains a critical issue. This retrospective study aims to investigate failure rates of palatal mini-implants and to identify the risk factors underlying it. Materials and Methods The study included 1,358 consecutive patients (799 females, 559 males) with a median age of 14 years (range: 6–64 years) who underwent orthodontic treatment using palatal skeletal anchorage. For each patient, we recorded whether any mini-implant failed (loss of stability requiring premature removal) or all remained stable (success). The failure rates of orthodontic mini-implants were assessed in relation to several factors, including patient age and gender, insertion site (median vs. paramedian), clinician type (specialist vs. resident), anchorage type (direct vs. indirect), the number of mini-implants utilized, and the type of appliance employed. Descriptive statistics were calculated. Associations between failure (yes/no per patient) and each factor were tested using Fisher’s exact test or chi-square test, as appropriate. A two-tailed p < 0.05 was considered statistically significant. Results A total of 1,336 patients (out of 1,358; 22 excluded for incomplete follow-up data) were included in the final analysis, with 2,632 mini-implants placed. The overall failure rate was 4.1%. Neither patient sex nor age (analyzed in age groups <13, 13–17, ≥18 years) showed a significant association with failure (p > 0.05). The number of mini-implants per patient (most patients had 1 or 2 implants) was also not significantly related to failure risk (p = 0.31). However, among patients under 13 years of age, the median insertion was associated with a significantly higher failure rate (7.3%) compared to the paramedian insertion (2.7%) (p = 0.046). In older patients (≥13 years), failure rates did not differ between median and paramedian placements. Appliances in which a direct anchorage was utilized demonstrated a significantly higher failure rate (4.9%) than the appliances which have used indirect anchorage (0.6%) (p = 0.006, odds ratio ~8.5). Specific appliances such as the Mousetrap for molar intrusion (11.1%) and the Hybridhyrax-Distalizer for expansion and distalization (23.1%) showed the highest failure rates. A chi-square analysis confirmed a significant overall association between appliance type and failure rate (p = 0.013). Conclusion Our findings confirm the effectiveness of mini-implants as temporary anchorage devices while highlighting clinical factors that may influence their failure rates. In particular, for younger patients, a paramedian insertion site may be preferable over midline insertion to reduce the chance of failure. Furthermore, in case for appliances that exert high forces on the anchorage unit, the use of multiple mini-implants should be considered to reduce the likelihood of implant failure. Nevertheless, all recommendations should be considered with caution given the observational nature of the study. Ongoing attention to patient oral hygiene, absence of peri-implant inflammation, and careful surgical technique remain critical for the long-term success of mini-implant anchorage.