British Orthodontic Society, Chapman Prize Winner 2003. A novel in vitro culture model to investigate the reaction of the dentine-pulp complex to orthodontic force.
OBJECTIVE
To develop a novel mandible slice organ culture model to investigate the effects of externally applied force on the dentine-pulp complex.


METHODS
In vitro organ culture.


METHODS
School of Dentistry, Birmingham, UK.


METHODS
Transverse 2 mm thick sections were cut from the mandibles of five 28-day-old male Wistar rats. Serial sections were used for control and test pairs. Springs made from 0.016-inch and 0.019 x 0.025-inch stainless steel wires were used to apply a 50 g tensile or compressive force, respectively, to test specimens. Control and test specimens were cultured for 5 days in a humidified incubator with 5% CO(2) at 37 degrees C and processed for routine histological investigation. Nine more rats were used to provide control and compression test pairs where the pulps were extirpated after 3 days culture and total RNA isolated for gene expression analysis by reverse transcriptase polymerase chain reaction (RT-PCR).


RESULTS
Histology showed the dental and supporting tissues maintained a healthy appearance in the control cultures after culture. Histomorphometric analysis revealed a 20-27% increase in pulp fibroblast density in test specimens compared with controls. Gene expression analyses revealed up-regulation in the test groups of PCNA, c-Myc, Collagen 1alpha, TGF-beta1 and alkaline phosphatase, whilst expression of osteocalcin was reduced.


CONCLUSIONS
The results demonstrated that the present organ culture technique provides a valuable in vitro experimental model for studying the effects of externally applied forces. These forces stimulated a cellular response in the pulp chamber characterized by altered gene expression and proliferation of fibroblasts; the latter being unaffected by the nature of the force in terms of compression or tension.
Dhopatkar
A A
AA
Orthodontic Unit, School of Dentistry, St Chad's Queensway, Birmingham B4 6NN, UK. dhopatkar@aol.com
Sloan
A J
AJ
Rock
W P
WP
Cooper
P R
PR
Smith
A J
AJ
D000469:Alkaline Phosphatase / Q000032:analysis; D000818:Animals; D001363:Awards and Prizes; D002452:Cell Count; D024042:Collagen Type I / Q000032:analysis; D000090602:Collagen Type I, alpha 1 Chain; D003782:Dental Pulp / Q000033:anatomy & histology* / Q000166:cytology; D003804:Dentin / Q000033:anatomy & histology*; D005347:Fibroblasts / Q000166:cytology; D008297:Male; D008334:Mandible / Q000033:anatomy & histology*; D009924:Organ Culture Techniques; D009969:Orthodontic Wires; D009970:Orthodontics; D015675:Osteocalcin / Q000032:analysis; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D016271:Proto-Oncogene Proteins c-myc; D051381:Rats; D017208:Rats, Wistar; D013193:Stainless Steel; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques; D016212:Transforming Growth Factor beta / Q000032:analysis; D053773:Transforming Growth Factor beta1
D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D018809:Proliferating Cell Nuclear Antigen; D016271:Proto-Oncogene Proteins c-myc; C508962:Tgfb1 protein, rat; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D015675:Osteocalcin; D013193:Stainless Steel; D000469:Alkaline Phosphatase