Changes in maxillary molar pulp blood flow during orthodontic intrusion

The aim of this prospective study was to evaluate the effects of maxillary first molar intrusion on pulpal blood flow (PBF) in humans as recorded by laser Doppler flowmetry (LDF).

Maxillary first molars of 16 participants were divided into two groups. In the study group, 20 teeth in 10 participants were subjected to an intrusive force of 100 g delivered from mini-implants for 6 months. A control group of 6 subjects (12 teeth) received no orthodontic treatment. LDF measurements were recorded at baseline and at 3 days, 3 weeks, 3 months and 6 months during intrusion. Data was analysed using the Wilcoxon Signed Rank and Mann-Whitney U tests, with a level of p < 0.05 considered statistically significant.

No significant changes in PBF perfusion units (PU) were observed in the control group over the course of the study. However, PBF in the study group was significantly higher at TO (8.7 ± 0.9 PU) when compared with T1 (6.1 ± 0.6 PU, p < 0.001) and T2 (6.0 ± 0.6 PU, p < 0.001). PBF did not vary significantly between T1 and T2 (p = 0.073) or between T3 and T4 (p = 0.262). Moreover, PBF at the end of the study (T4) was similar to baseline PBF values for both groups (study group: p = 0.687; control group: p = 0.525).

Despite significant short-term regressive changes in pulpal tissue during continuous molar intrusion with mini-implants and an applied force of 100 g, blood vessel function was maintained throughout intrusion, as indicated by LDF measurements of PBF, which tended to return to baseline values by the end of the observation period. These results highlight the changes that can occur in molar vascularity, especially during six months of intrusion.