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Periodontal ligament enhancement after orthodontic movement in third molars: Proliferative stimulus or increased periodontal ligament space?

Periodontal ligament enhancement after orthodontic movement in third molars: Proliferative stimulus or increased periodontal ligament space?

American Journal of Orthodontics and Dentofacial Orthopedics, 2021-07-01, Volume 160, Issue 1, Pages 7-7, Copyright © 2021 American Association of Orthodontists

The understanding of how orthodontic movement of the teeth can assist other dental specialties and benefit the patients should be a major concern of orthodontic clinicians and researchers, hence the prominent role of the articles published by the American Journal of Orthodontics and Dentofacial Orthopedics over more than 100 years. The critical analysis of these papers contributes to the improvement of scientific evidence associated with the American Journal of Orthodontics and Dentofacial Orthopedics content.

Therefore, we read the article “Periodontal ligament enhancement in mesio-angulated impaction of third molars after orthodontic tooth movement: A prospective cohort study” with great interest, as the authors tried to provide information on the effect of using orthodontic forces as a means of assisting autotransplantation of third molars. Despite it not being the main objective of the paper, the text presents simple and effective orthodontic mechanics used to upright molars through the distal movement of the crown, describing in detail the materials used and the required activations.

The success of autotransplantation procedures is strongly related to the integrity of periodontal ligament (PDL) cells adhered to the root surface. According to the authors, orthodontic uprighting of the third molars facilitated access to the crown of the teeth and increased the space of the PDL, allowing a simple and atraumatic extraction and minimizing the damages to the PDL. At the moment of extraction, the molars of the experimental group had indeed been uprighted 26.2° (54%) in 3.4 months.

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To evaluate the amount of PDL adhered to root surfaces of uprighted third molars, the study compared a control group with completely erupted teeth that had not been subjected to orthodontic forces, thus having normal width of the PDL space. As stated by the authors several times, the lack of increased width of PDL space in the control group resulted in destructive pressure between the root and the alveolar bone during extraction, compromising PDL cells on the root surface.

Despite the increased width of the PDL being accompanied by the maintenance of cell density, which can indicate proliferative stimulus as a result of orthodontic forces, we believe that the larger area stained with toluidine blue visualized by Promchaiwattana et al in the root of uprighted teeth is strongly related to their extraction being less traumatic to the PDL. Therefore, upcoming clinical studies aiming to demonstrate the effects of preapplication of orthodontic force on human PDL tissue must efficiently control the trauma to the PDL during the extraction.

References

  • 1. Promchaiwattana P., Suzuki B., Krisanaprakornkit S., Suzuki E.Y.: Periodontal ligament enhancement in mesio-angulated impaction of third molars after orthodontic tooth movement: a prospective cohort study. Am J Orthod Dentofacial Orthop 2020; 158: pp. 495-504.
  • 2. Suzaki Y., Matsumoto Y., Kanno Z., Soma K.: Preapplication of orthodontic forces to the donor teeth affects periodontal healing of transplanted teeth. Angle Orthod 2008; 78: pp. 495-501.