Methylphenidate-effects on orthodontic tooth movement, orthodontically induced and nonorthodontic root resorption? : A micro-computed tomography and immunohistochemical analysis.

PURPOSE: The aim of this study was to examine the effect of methylphenidate, prescribed for individuals with attention deficit hyperactivity disorder (ADHD), on orthodontic tooth movement (OTM) and root resorption.

METHODS

In all, 30 rats were divided into (1) control (C), (2) constant (MCD), and (3) increasing dose of methylphenidate (MID) groups and 2 subgroups for each of them (nonorthodontic (30 days)/orthodontic (44 days)). After receiving saline or methylphenidate for 30 days, rats in the nonorthodontic groups were euthanized (n = 5/group). Subsequently, 50 g of orthodontic force was applied to the remaining rats' first molars for 14 days (orthodontic groups). Quantitative micro-computed tomography (micro-CT) and immunohistochemical analyses were conducted. For statistical analyses Kruskal-Wallis and Dunnet tests were applied with a significance set at p < 0.05.

RESULTS

Micro-CT analysis demonstrated a statistically significant increase in tooth displacement with higher doses of methylphenidate compared to control and lower-dose groups, though no significant difference was detected between MID-44 and MCD-44 groups. Orthodontic force led to a significant increase in root resorption, peaking in the coronal region and diminishing toward the apex. The highest amount of resorption was observed in the MID groups, with a significant difference between nonorthodontic MID-30 and C‑30 groups. No significant changes in bone parameters were noted in the tension zone, but numerical reductions in trabecular thickness (Tb.Th), bone volume fraction (BV/TV), and bone mineral density (BMD) were observed. In nonorthodontic cohorts, VEGF and RANK levels were significantly elevated in the MID-30 group, along with increased TRAP expression, indicating bone resorption. Orthodontic cohorts exhibited a significant increase in RANK- and TRAP-positive cells with methylphenidate administration. Reductions in OPG and elevations in RANK, RANKL, VEGF, and TRAP were noted, primarily between orthodontic and nonorthodontic groups.

CONCLUSION

The present rat model suggests a weak potential for methylphenidate to increase root resorption. However, increased doses of methylphenidate accelerated OTM.