Orthodontic forces produce a series of changes in dental pulp. However, no one has attempted to investigate the incidence of pulp necrosis after orthodontic therapy in the clinic. In this study, we aimed to investigate pulp vitality and histologic changes after the application of moderate and severe intrusive forces. Methods Twenty-seven adolescent patients were assigned to 1 of 3 groups: the control group of 3 subjects; the moderate-force group, with 12 subjects who received a 50-g force to the first premolars bilaterally; and the severe-force group, with 12 subjects who received a 300-g force. The forces were applied for 1, 4, 8, or 12 weeks. An electric pulp tester was used to test for vitality, and teeth that did not respond to the electric pulp tester were subsequently tested thermally with a stick of heated gutta-percha. Results The teeth with a negative response to the electric pulp tester still responded to the thermal test. We found odontoblast disruption, vacuolization, and moderate vascular congestion in both force groups, but no necrosis was observed. Pulp stones were formed only in the severe-force group. Conclusions Dental pulp still has vitality after intrusive treatment with different forces. These data provide new insights into the effects of intrusive orthodontic forces.
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