INTRODUCTION: Force application to a tooth during orthodontic treatment evokes a biological response of the dental pulp. The aim of this systematic literature review was to investigate the relationship between orthodontic force level and pulp reaction in humans.
METHODS: Electronic search was made of publications in PubMed/old MEDLINE, Web of Science, EMBASE, CINAHL, Scopus, and the Cochrane Library (DARE, CENTRAL) until July 21, 2012. Hand search was made of publications before 1954 and the most recent ones in main dental and orthodontic journals. Additional studies were identified by hand search of reference lists of relevant articles from both the electronic and hand searches. Search terms included biomechanics, force, orthodontic*, tooth movement, dental pulp, and pulpal reaction. Two independent observers assessed eligibility for inclusion, extracted the data, applied quality indicators, and graded level of evidence.
RESULTS: Twenty-four studies matched the inclusion criteria. The outcomes concerned histologic and cell biological parameters after orthodontic tooth movement in 19 studies and pulpal blood flow in 5 studies. The methodologic quality of most studies was graded moderate to low.
CONCLUSIONS: Because of a lack of high-quality studies there is no conclusive scientific evidence for a relation between force level and dental pulp tissue reaction in humans. There is contradictory scientific support for a force-dependent reduction of blood flow.