Traumatic tooth shortening in commercial piglets: effects on gross tooth pathology and mRNA markers of inflammation and pain

Aim of investigations[br/] The aim of the study was to characterise the long-term effects (1-6 weeks) of two methods of tooth resection (clipping and grinding) on tooth pathology and markers of inflammation and pain in commercial piglets. The experiments are part of a project aimed at assessing the effects of the management practice of tooth resection on piglet welfare. [br/] Methods[br/] Forty-eight female piglets from 8 replicates (litters) were assigned to one of three treatments (SHAM, CLIP, GRIND). Tooth integrity was scored post-mortem at 1 or 6 weeks after tooth treatment (n=8/treatment/time-period). Dental pulp was extracted from 384 teeth (8/pig) - pooled and processed at pig level - to quantify changes in mRNA transcript expression of C-X-C motif chemokine ligand 8 (CXCL8) and calcitonin related polypeptide beta (CALCB) as neuropeptide markers of inflammation and pain using reverse transcription quantitative PCR. Data were analysed using the statistical package R Studio. The statistical tests used to analyse CALCB and CXCL8 were ANOVA and Kruskal-Wallis respectively.[br/] Results[br/] All CLIP and GRIND piglets exhibited pulp exposure. Mean percentage numbers of needle teeth with exposed pulp were 0.8%, 65.8%, and 85.8% in SHAM, GRIND, and CLIP piglets respectively. In resected teeth, CXCL8 gene expression was found to be significantly increased by both methods of tooth resection (p<0.001) at both time periods (mean fold-changes relative to SHAM were 333-fold and 483-fold at 1 week and 330-fold and 558-fold at 6 weeks for GRIND and CLIP treatments respectively) indicating a prolonged localised inflammatory state in the tooth pulp induced by both methods of tooth resection. In resected teeth, expression of CALCB was found to be significantly downregulated (p<0.001) in week 1 (mean fold changes relative to SHAM were 0.55-fold for GRIND (p<0.05) and 0.29-fold for CLIP (p<0.001)), with the CLIP downregulation being significantly greater than that of GRIND (p<0.05). By week 6, this downregulation was reduced to a tendency for GRIND (0.41-fold change relative to SHAM, p=0.06), whereas CLIP downregulation remained significant (0.13-fold change relative to SHAM, p<0.001) and significantly greater than for GRIND (p