Quantitative assessment of intrapulpal axon response to orthodontic movement

Nerve fiber changes are of potential concern during tooth movement. Quantitative and qualitative assessments using electron microscopy of nerve fibers entering the tooth give an indication of change in the remainder of the pulp. Eight healthy mandibular first premolars were selected from four subjects, so that respective pairs had open apices and short-term movement, open apices and long-term movement, closed apices and short-term movement, and closed apices and long-term movement. These were compared to forty-nine untreated control teeth. No significant differences in myelinated or unmyelinated axon number were observed between experimental and control teeth. Altered myelin figures, possibly degenerating, were observed in only a small percentage of axons in teeth moved for a short period. No alterations were observed in teeth moved for long periods. It is concluded that intrapulpal axon alterations are minimal and not progressive with conservative orthodontic tooth movement.