Changes in the Pulp Tissue Complex Induced by Orthodontic Forces: Is There a Need for Concern? A Systematic Review and Meta-Analysis of RCTs and Prospective Clinical Trials.

To identify and assess any changes in the pulp tissue complex following orthodontic force application.Published and unpublished literature was searched in seven databases until 9 August 2022 for randomised controlled trials (RCTs) and prospective trials (nR-PCT). Representative key words included 'pulp response', 'pulp tissue', 'orthodontic force', and 'tooth movement'. Study selection, data extraction, risk of bias and certainty of evidence assessment were conducted independently by two reviewers. Random effects meta-analyses with respective confidence intervals (95%CIs) were conducted where applicable.A total of 363 records were screened, a final number of 24 articles were eligible for qualitative synthesis, while 8 of those contributed to meta-analyses. There was evidence that pulpal blood flow (PBF) decreased after 3 weeks of tooth movement compared to no force application (4 studies, mean difference: -1.68; 95% CI: -3.21, -0.15; p = 0.03). However, this was not the case after 6 months of treatment (p = 0.68). A rise in the activity of aspartate aminotransferase (AST) was detected after 7 days of treatment, but combining 2 studies, this was not statistically significant (p = 0.25). Other outcomes were assessed through single studies. Risk of bias was within the range of 'some concerns/moderate to high/critical overall', while certainty of evidence was low to very low according to GRADE.As a short-term effect, PBF decreased upon initiation of orthodontic force application, while enzymatic and peptide activity within the pulp was transiently affected. Further long-term evidence of improved quality and certainty is needed.