Assessment of Pulp Regeneration Induced by Stem Cell Therapy by Magnetic Resonance Imaging

• This study was designed to evaluate the usefulness of MRI for detecting tooth vitality after stem cell transplantation for pulp regeneration.
• The signal intensity (SI) of normal teeth was significantly higher than that of nonvital pulpectomized teeth and collagen transplanted nonregenerated teeth.
• Regenerated pulp tissue showed a high SI similar to normal teeth.
• The changes in SI of MRI in the regenerated pulp were consistent with histopathologic findings, showing a potential noninvasive method to serially access the effectiveness of pulp regeneration elicited by stem cell therapy.

IntroductionThis study was designed to evaluate the usefulness of magnetic resonance imaging (MRI) to assess the regeneration of pulp tissue.MethodsMobilized dental pulp stem cells and granulocyte colony-stimulating factor with collagen were transplanted into mature pulpectomized teeth for pulp regeneration (n = 4). The controls consisted of pulpectomized teeth with or without collagen and normal teeth with intact pulp tissue (n = 4, each). The signal intensity (SI) of MRI using T2 sequences was compared after the extraction of teeth in dogs. MRI was correlated with the corresponding histologic findings.ResultsPulp tissue was fully regenerated 90 days after cell transplantation. On the other hand, the root canal was empty in the control collagen-transplanted teeth at 90 days. The SI of the normal teeth was significantly higher than that of nonvital pulpectomized teeth and the controls of collagen transplanted teeth at 90 days. The stem cell transplanted teeth showed a gradual decrease in the SI until 180 days at which time the SI was similar to that in the normal teeth and significantly higher than that in the teeth transplanted with collagen alone without the stem cells.ConclusionsThe changes in the SI of the pulplike tissue were consistent with the histologic findings, showing the potential usefulness of the noninvasive method to serially access the efficacy of pulp regenerative therapy.