AIM: To examine the feasibility of using the pOBCol3.6GFPtpz [3.6-green 
fluorescent protein (GFP)] transgenic mice as an in vivo model for studying the 
biological sequence of events during pulp healing and reparative dentinogenesis.
METHODOLOGY: Pulp exposures were created in the first maxillary molar of 
12-16-week-old 3.6-GFP transgenic mice with CD1 and C57/Bl6 genetic background. 
Direct pulp capping on exposed teeth was performed using mineral trioxide 
aggregate followed by restoration with a light-cured adhesive system (AS) and 
composite resin. In control teeth, the AS was placed in direct contact with the 
pulp. Animals were euthanized at various time points after pulp exposure and 
capping. The maxillary arch was isolated, fixed and processed for histological 
and epifluorescence analysis to examine reparative dentinogenesis.
RESULTS: Analysis of teeth immediately after pulp exposure revealed absence of 
odontoblasts expressing 3.6-GFP at the injury site. Evidence of reparative 
dentinogenesis was apparent at 4 weeks in 3.6-GFP mice in CD1 background and at 
8 weeks in 3.6-GFP mice with C57/Bl6 background. The reparative dentine with 
both groups contained newly formed atubular-mineralized tissue resembling a 
dentine bridge and/or osteodentine that was lined by cells expressing 3.6-GFP as 
well as 3.6-GFP expressing cells embedded within the atubular matrix.
CONCLUSION: This study was conducted in a few animals and did not allow 
statistical analysis. The results revealed that the 3.6-GFP transgenic animals 
provide a unique model for direct analysis of cellular and molecular mechanisms 
of pulp repair and tertiary dentinogenesis in vivo. The study also shows the 
effects of the capping material and the genetic background of the mice in the 
sequence and timing of reparative dentinogenesis.