Expression of substance P, calcitonin gene-related peptide and vascular endothelial growth factor in human dental pulp under different clinical stimuli

Abstract

Background: The aim of this study was to measure the dental pulp inflammatory response through neuropeptides (SP and CGRP) as a response to occlusal trauma, orthodontic movements and a combination of both, as well as the angiogenic defense mechanism through VEGF expression, which could be the initial step to mineralized tissue formation.

Methods: Forty human dental pulp samples were collected from healthy first premolars with extraction indicated due to orthodontic reasons from a sample of 20 patients. Patients were divided into four groups with 10 premolars each (1 mandibular and 1 maxillary premolar from each patient): healthy pulp control group, occlusal trauma group, moderate orthodontic forces group; and occlusal trauma plus moderate orthodontic forces group. Stimuli were applied for 24 h before tooth extraction in all experimental groups. All samples were processed, and SP, CGRP, and VEGF were measured by radioimmunoassay. The Kruskal-Wallis test was performed to assess significant differences among groups and Mann-Whitney's U post hoc pairwise comparisons were also performed.

Results: The highest increase in SP, CGRP, and VEGF expressions was found in the occlusal trauma plus orthodontic forces group, followed by the moderate orthodontic forces, the occlusal trauma and the control groups, with statistically significant differences between all groups for each of the 3 peptides analyzed (Kruskal-Wallis p < 0.001). All possible pairwise post-hoc comparisons were also significant for each peptide analyzed (Mann-Whitney's U p < 0.001).

Conclusion: SP, CGRP, and VEGF expressions significantly increase in human dental pulps when stimulated by occlusal trauma combined with moderate orthodontic forces, as compared with these two stimuli applied independently. Name of the registry: Importance of Neurogenic Inflammation in the Angiogenic Response of the Dental Pulp as a Defensive Response.

Trial registration number: NCT03804034. Date of registration: 01/15/2019 Retrospectively registered. URL of trial registry record: https://clinicaltrials.gov/ct2/show/NCT03804034?term=NCT03804034&draw=2&rank=1 .

Keywords: CGRP; Neurogenic inflammation; Occlusal trauma; Orthodontics force; SP; VEGF.

Fig. 1

Clinical images of the different stimuli applied to the patients in each group. a Control Group (without occlusal trauma nor orthodontic force); b occlusal trauma group; c moderate orthodontic force group; d occlusal trauma plus moderate orthodontic force group

Fig. 2

Substance P (SP) expression (pmol/mg) in human dental pulp from teeth under different stimuli (Colored boxes: mean and 95% confidence interval, whiskers: minimum and maximum values, circle dots: individual sample values)

Fig. 3

Calcitonin gene-related peptide (CGRP) expression (pmol/mg) in human dental pulp from teeth under different stimuli (Colored boxes: mean and 95% confidence interval, whiskers: minimum and maximum values, circle dots: individual sample values)

Fig. 4

Vascular endothelial growth factor (VEGF) expression (pmol/mg) in human dental pulp from teeth under different stimuli (Colored boxes: mean and 95% confidence interval, whiskers: minimum and maximum values, circle dots: individual sample values)