IADR Abstract Archives
A New Rat Molar Model of Symptomatic Irreversible Pulpitis
Objectives: To develop a new translatable model of symptomatic irreversible pulpitis (SIP) and explore its nociceptive peripheral and central mechanisms.
Methods: A small access cavity was drilled into the first maxillary molar of Naïve adult male Sprague Dawley rats (180-250g, n=33), after which a sterilised paper point was introduced into the pulp. A glass-ionomer restoration was placed with the paper point protruding through it. At days 1-5 nociceptive mechanisms were assessed using behavioural, biochemical, and immuno-histological analysis.
Results: Behavioural assessment demonstrated:
-Increased rat grimace scale score in SIP vs sham at day 1 (change from baseline: 0.234 vs -0.049, p=0.003, n=25).
-Mechanical allodynia (Von Frey test) demonstrated in SIP vs sham at days 1 and 2: 11.75g vs 25.00g (p=0.012, n=25); 9.36g vs 26.58g, (p=0.006, n=18) respectively.
-Thermal allodynia caused less attempts to access reward in SIP vs sham at days 1, 2 and 5: 5.86 vs 21.58 (p=0.008, n=33); 3.34 vs 20.83 (p=0.037, n=25); 10.42 vs 25.38 (p=0.033, n=10) respectively.
Soft food preference in SIP vs sham at day 5 (change from baseline: 4.36 vs -6.55, p=0.021, n=10).
Biochemical analyses demonstrated:
-Serum IL-1β increased in SIP vs sham at day 2 (948.5pg/ml vs 616.58pg/ml, p=0.039, n=18).
-Serum TNFα increased in SIP vs sham at day 5 (238.32pg/ml vs 50.09pg/ml, p=0.039, n=10).
Histological (Hematoxylin and Eosin) analyses demonstrated: progressive coronal pulp inflammation from day 2 to day 5, with the formation of micro-abscesses and areas of necrosis at day 5.
Immunohistochemical analyses of sub-nucleus caudalis demonstrated: increased levels of GFAP and phosphorylated α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid ipsilateral to SIP.
Conclusions: This novel model of SIP is valid and presents previously unreported behavioural and histological changes in rats. It offers a more translatable biological model to SIP pathogenesis in humans compared to previously reported models.
Methods: A small access cavity was drilled into the first maxillary molar of Naïve adult male Sprague Dawley rats (180-250g, n=33), after which a sterilised paper point was introduced into the pulp. A glass-ionomer restoration was placed with the paper point protruding through it. At days 1-5 nociceptive mechanisms were assessed using behavioural, biochemical, and immuno-histological analysis.
Results: Behavioural assessment demonstrated:
-Increased rat grimace scale score in SIP vs sham at day 1 (change from baseline: 0.234 vs -0.049, p=0.003, n=25).
-Mechanical allodynia (Von Frey test) demonstrated in SIP vs sham at days 1 and 2: 11.75g vs 25.00g (p=0.012, n=25); 9.36g vs 26.58g, (p=0.006, n=18) respectively.
-Thermal allodynia caused less attempts to access reward in SIP vs sham at days 1, 2 and 5: 5.86 vs 21.58 (p=0.008, n=33); 3.34 vs 20.83 (p=0.037, n=25); 10.42 vs 25.38 (p=0.033, n=10) respectively.
Soft food preference in SIP vs sham at day 5 (change from baseline: 4.36 vs -6.55, p=0.021, n=10).
Biochemical analyses demonstrated:
-Serum IL-1β increased in SIP vs sham at day 2 (948.5pg/ml vs 616.58pg/ml, p=0.039, n=18).
-Serum TNFα increased in SIP vs sham at day 5 (238.32pg/ml vs 50.09pg/ml, p=0.039, n=10).
Histological (Hematoxylin and Eosin) analyses demonstrated: progressive coronal pulp inflammation from day 2 to day 5, with the formation of micro-abscesses and areas of necrosis at day 5.
Immunohistochemical analyses of sub-nucleus caudalis demonstrated: increased levels of GFAP and phosphorylated α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid ipsilateral to SIP.
Conclusions: This novel model of SIP is valid and presents previously unreported behavioural and histological changes in rats. It offers a more translatable biological model to SIP pathogenesis in humans compared to previously reported models.