Longterm effect of low intensity pulsed ultrasound on a human tooth slice organ culture

Objective Investigate the effect of therapeutic Low Intensity Pulsed Ultrasound (LIPUS) on human dentine–pulp complex in an in vitro model. Design 92 premolars were extracted from 23 adolescent orthodontic patients. The premolars were sectioned transversely into 600 μm thick slices. The slices were divided into two main groups according to how often the LIPUS was applied (single or daily application), and then subdivided into five subgroups each (5, 10, 15 and 20 min and one control group). The tooth slices were cultured at (37 °C/5% CO2) in a humidified incubator where medium was changed every 48 h. LIPUS was applied using a 3.9 cm2 transducer that produces an incident intensity of 30 mW/cm2. After five days, tissue was harvested for histomorphometrical analysis and real time PCR to investigate expression of genes of interest (Collagen I, DMP1, DSPP, TGF-β1, RANKL and OPG). Results Histomorphometric analyses revealed that odontoblast cell count was higher in the single application groups (5, 10 and 15 min, respectively) than in the control and other treatment groups. Predentin thickness was higher in the single application group (10, 5 and 15 min) respectively than in the daily application group and the control groups, however they were not significantly different from each other. Real time PCR demonstrated no statistically significant difference between the groups in the expression of Collagen I, DMP1, TGF-β1, DSPP, RANKL and OPG. Conclusion Reproducible responses from cultured dentine–pulp complex were observed in groups with single application of LIPUS for 5, 10 and 15 min