Pulpal Blood-flow Changes in Human Permanent Maxillary Canines During the Orthodontic Retraction Period
Abstract
The purpose of this study was to determine the effect of the external load of elastic orthodontic traction force on human pulpal blood flow (PBF) in maxillary canines using a Laser Doppler Flowmeter (LDF). Methods: Recordings were made from 9 maxillary canines, in 5 subjects who were to receive retraction of their teeth, after their upper first premolars were extracted, using a Moor type MBF3D/42 blood flow monitor with an opaque rubber dam covering all the gingivae around the teeth. The optic probe for LDF measurement was fixed to each tooth with an individual guiding fork constructed from 0.016x0.022 stainless steel wire soldered to a metal tube (int. diameter 1.75 mm). The probe was placed 2 mm from the gingival margin. The PBF was recorded before the force application as a baseline value. After that the traction forces of 300 gm from orthodontic elastic chains were applied from the hook of the maxillary molar band to the hook of canine bracket, and both the PBF and the traction force were measured again immediately and at day 1, 7, 21 and 28. Results: Compared to the preload value, the mean PBF statistically significantly increased at day 1, 7, 21 and 28 (baseline: 4.0+2.9 P.U.; after loading: 4.8 P.U.; after day 1: 8.2±5.7P.U.; day 7: 9.7±7.5P.U.;day21: 8.9±5.5P.U.; day 28: 9.1±3.6P.U., P<0.05, One way RM ANOVA and Dunnett’s method). However, the traction force significantly decreased at day 1, 7, 21 and 28 (base line : 300±0 gm; after day 1: 196.7± 26.5 gm; day 7: 161.7±35.9 gm; day 21: 140±28.9 gm; day 28: 125±30.6 gm, P<0.05, One way RM ANOVA and Tukey’s test). Conclusion: It is concluded that the continuous retraction force substantially causes pulpal vasodilation up to 28 days.
Key words:pulpal blood flow(PBF), Laser Doppler Flowmeter (LDF), individual guiding fork
