IADR Abstract Archives
Socket Healing and Immediate Implant Osseointegration Via Wnt-responsive PDL Cells
Objectives: Wnt signaling maintains homeostasis of the periodontium: if Wnt signaling is inhibited then alveolar bone volume and density, as well as cementum volume, decline. Also, periodontal ligament (PDL) remnants in osteotomies have been shown to contribute to bone formation. Therefore, in this study, we examined whether Wnt activity in PDL remnants contributes to socket healing and implant osseointegration.
Methods: We used the Axin2CreERT/-;mTmG/- transgenic mouse strain to trace eGFP+veWnt-responsive cells and their descendants following a tamoxifen pulse injection. After maxillary first molar extraction, osteotomies were created in the palatal root socket against the palatal surface using a 0.48 mm diameter drill. After osteotomy, PDL fibers were retained on buccal, mesial, and distal surfaces whilst not on the palatal surface. Titanium implants (Outer diameter 0.5mm, inner core diameter 0.4mm) were placed. Mice were sacrificed 3, 7, 14 days later for immunohistochemistry on 6 samples per group.
Results: We found that the PDL contained a quiescent population of Wnt-responsive cells. In response to tooth extraction, this population became mitotically active: cells migrated into the center of the extraction socket, and down-regulated expression of the Periostin protein while simultaneously up-regulated osteogenic protein expression on post-extraction day 3, ultimately, giving rise to osteoblasts and healed the extraction sockets on post-exrtaction day 7. Around implants, regions retaining PDL fibers showed more Wnt-responsive osteogenic cells that produced significantly more new bone than regions deprived PDL.
Conclusions: A quiescent, Wnt-responsive cell population in the PDL is activated by injury and differentiates into alveolar bone-producing osteoblasts. This Wnt-responisve population ultimately contributes to socket healing and immediate implant osseointegration.
Methods: We used the Axin2CreERT/-;mTmG/- transgenic mouse strain to trace eGFP+veWnt-responsive cells and their descendants following a tamoxifen pulse injection. After maxillary first molar extraction, osteotomies were created in the palatal root socket against the palatal surface using a 0.48 mm diameter drill. After osteotomy, PDL fibers were retained on buccal, mesial, and distal surfaces whilst not on the palatal surface. Titanium implants (Outer diameter 0.5mm, inner core diameter 0.4mm) were placed. Mice were sacrificed 3, 7, 14 days later for immunohistochemistry on 6 samples per group.
Results: We found that the PDL contained a quiescent population of Wnt-responsive cells. In response to tooth extraction, this population became mitotically active: cells migrated into the center of the extraction socket, and down-regulated expression of the Periostin protein while simultaneously up-regulated osteogenic protein expression on post-extraction day 3, ultimately, giving rise to osteoblasts and healed the extraction sockets on post-exrtaction day 7. Around implants, regions retaining PDL fibers showed more Wnt-responsive osteogenic cells that produced significantly more new bone than regions deprived PDL.
Conclusions: A quiescent, Wnt-responsive cell population in the PDL is activated by injury and differentiates into alveolar bone-producing osteoblasts. This Wnt-responisve population ultimately contributes to socket healing and immediate implant osseointegration.